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Ed Vargo

Texas A&M University, Entomology, Faculty Member

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Phone: 979-845-5855
Address: Building 1804 F&B Rd. 2556
2143 TAMU
Texas A&M University
College Station, TX 77843-2143, U.S.A.

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Papers by Ed Vargo

Unique features of a global human ectoparasite identified through sequencing of the bed bug genome

Nature communications, Jan 2, 2016

The bed bug, Cimex lectularius, has re-established itself as a ubiquitous human ectoparasite thro... more The bed bug, Cimex lectularius, has re-established itself as a ubiquitous human ectoparasite throughout much of the world during the past two decades. This global resurgence is likely linked to increased international travel and commerce in addition to widespread insecticide resistance. Analyses of the C. lectularius sequenced genome (650 Mb) and 14,220 predicted protein-coding genes provide a comprehensive representation of genes that are linked to traumatic insemination, a reduced chemosensory repertoire of genes related to obligate hematophagy, host-symbiont interactions, and several mechanisms of insecticide resistance. In addition, we document the presence of multiple putative lateral gene transfer events. Genome sequencing and annotation establish a solid foundation for future research on mechanisms of insecticide resistance, human-bed bug and symbiont-bed bug associations, and unique features of bed bug biology that contribute to the unprecedented success of C. lectularius as...

Asexual queen succession in the subterranean termite Reticulitermes virginicus

Proceedings of the Royal Society B: Biological Sciences, 2011

Termite colonies are founded by a pair of primary reproductives. In many species, including subte... more Termite colonies are founded by a pair of primary reproductives. In many species, including subterranean termites (family Rhinotermitidae), the primary king and queen can be succeeded by neotenic reproductives that are produced from workers or nymphs within the colony. It is generally believed that these neotenics inbreed within the colony, sometimes for many generations. Here, we show that primary queens of the North American subterranean termite, Reticulitermes virginicus , are replaced by numerous parthenogenetically produced female neotenics. We collected functional female neotenics from five colonies of R. virginicus in North Carolina and Texas, USA. Genetic analysis at eight microsatellite loci showed that 91–100% of the neotenics present within a colony were homozygous at all loci, indicating that they were produced through automictic parthenogenesis with terminal fusion. In contrast, workers, soldiers and alates were almost exclusively sexually produced by mating between the...

Inbreeding and disease resistance in a social insect: effects of heterozygosity on immunocompetence in the termite Zootermopsis angusticollis

Proceedings of the Royal Society B: Biological Sciences, 2006

Recent research has shown that low genetic variation in individuals can increase susceptibility t... more Recent research has shown that low genetic variation in individuals can increase susceptibility to infection and group living may exacerbate pathogen transmission. In the eusocial diploid termites, cycles of outbreeding and inbreeding characterizing basal species can reduce genetic variation within nestmates during the life of a colony, but the relationship of genetic heterogeneity to disease resistance is poorly understood. Here we show that, one generation of inbreeding differentially affects the survivorship of isolated and grouped termites ( Zootermopsis angusticollis) depending on the nature of immune challenge and treatment. Inbred and outbred isolated and grouped termites inoculated with a bacterial pathogen, exposed to a low dose of fungal pathogen or challenged with an implanted nylon monofilament had similar levels of immune defence. However, inbred grouped termites exposed to a relatively high concentration of fungal conidia had significantly greater mortality than outbre...

Thrips tabaci Population Genetic Structure and Polyploidy in Relation to Competency as a Vector of Tomato Spotted Wilt Virus

PLoS ONE, 2013

Knowledge of population-level genetic differences can help explain variation among populations of... more Knowledge of population-level genetic differences can help explain variation among populations of insect vectors in their role in the epidemiology of specific viruses. Variation in competency to transmit Tomato spotted wilt virus (TSWV) that exists among populations of Thrips tabaci has been associated with the presence of cryptic species that exhibit different modes of reproduction and host ranges. However, recent findings suggest that vector competency of T. tabaci at any given location depends on the thrips and virus populations that are present. This study characterizes the population genetic structure of T. tabaci collected from four locations in North Carolina and examines the relationship between population genetic structure and variation in TSWV transmission by T. tabaci. Mitochondrial COI sequence analysis revealed the presence of two genetically distinct groups with one characterized by thelytokous, parthenogenetic reproduction and the other by arrhenotokous, sexual reproduction. Using a set of 11 microsatellite markers that we developed to investigate T. tabaci population genetic structure, we identified 17 clonal groups and found significant genetic structuring among the four NC populations that corresponded to the geographic locations where the populations were collected. Application of microsatellite markers also led to the discovery of polyploidy in this species. All four populations contained tetraploid individuals, and three contained both diploid and tetraploid individuals. Analysis of variation in transmission ofTSWV among isofemale lines initiated with individuals used in this study revealed that 'clone assignment,' 'virus isolate' and their interaction significantly influenced vector competency. These results highlight the importance of interactions between specific T. tabaci clonal types and specific TSWV isolates underlying transmission of TSWV by T. tabaci.

Elimination of Subterranean Termite (Isoptera: Rhinotermitidae) Colonies Using a Refined Cellulose Bait Matrix Containing Noviflumuron When Monitored and Replenished Quarterly

Journal of Economic Entomology, 2012

Using a quarterly (3-mo) monitoring and bait-replenishment interval, 122 subterranean termite col... more Using a quarterly (3-mo) monitoring and bait-replenishment interval, 122 subterranean termite colonies throughout the United States were baited with a reÞned cellulose bait matrix containing 0.5% novißumuron. All colonies were eliminated in less than 1 yr after initiation of baiting as determined by long-term monitoring and genetic markers. Sixty-three percent of the colonies were eliminated during the Þrst quarter after the initiation of baiting and 77% of colonies were eliminated after consuming two bait tubes or less. This suggests that a single baiting cycle and bait installed in response to a single active monitoring device were sufÞcient to eliminate the majority of colonies. Although termites temporarily abandoned stations after depleting bait, workers resumed feeding when baits were replenished. Colonies that consumed large amounts of bait before elimination foraged into multiple stations, thus allowing adequate amounts of bait to sustain feeding. The time to eliminate termite colonies with bait replenished quarterly was similar to that previously reported for laminated cellulose bait replenished monthly. Our data support the conclusion that extending the bait replenishment interval from monthly to quarterly for bait tubes with reÞned cellulose containing 0.5% novißumuron did not adversely impact colony elimination.

Genetic Analysis of Colony and Population Structure of Three Introduced Populations of the Formosan Subterranean Termite (Isoptera: Rhinotermitidae) in the Continental United States

Environmental Entomology, 2006

The Formosan subterranean termite, Coptotermes formosanus Shiraki, is a major invasive pest speci... more The Formosan subterranean termite, Coptotermes formosanus Shiraki, is a major invasive pest species in many parts of the world. We compared the colony breeding system and population genetic structure in three introduced populations in the continental United States: Charleston, SC; City Park, New Orleans, LA; and Rutherford County, NC. Based on worker genotypes at 12 microsatellite loci, we found that colonies were mainly genetically distinct entities consisting of either simple families headed by monogamous pairs of reproductives or extended families containing multiple neotenic (replacement) reproductives descended from simple families. Populations varied from 48% simple families in Charleston to 82% simple families in City Park. Extended family colonies in all three populations were likely headed by Ͻ10 neotenic reproductives. There was no signiÞcant isolation by distance in any of the populations, suggesting that colonies reproduce by relatively long-range mating ßights and/or human-mediated dispersal within each population. The Charleston population showed evidence of a recent genetic bottleneck and most likely was founded by very few colonies. Cluster analysis indicated that the Charleston and City Park populations are quite genetically distant from each other and most likely originated from different source populations. The more recently introduced Rutherford County population was genetically most similar to City Park. These Þndings, together with results from other infested sites, indicate considerable variation in the genetic structure and breeding system of introduced populations of this species, making it unlikely that there is a simple genetic or behavioral explanation for the success of C. formosanus as an invasive species.

Genetic diversity and colony breeding structure in native and introduced ranges of the Formosan subterranean termite, Coptotermes formosanus

Biological Invasions, 2011

The Formosan subterranean termite, Coptotermes formosanus is recognized as one of the most import... more The Formosan subterranean termite, Coptotermes formosanus is recognized as one of the most important invasive pest species. Originating from China, C. formosanus has spread to many tropical and subtropical regions around the globe in the last 400 years, including Japan, Hawaii and the continental USA. Although the current distribution is well documented, information about the patterns of invasion and effects of introduction on the population genetics of this species is largely lacking. We analyzed the genetic structure of populations from two native populations (Guangdong and Hunan provinces, China) and two introduced populations (Maui and Kauai, Hawaii) using microsatellite genotyping. We also reanalyzed published data of additional populations from China, Japan, Hawaii, and the continental USA. The population from Hunan, the earliest introduction outside of China (Japan) and the first introduction to the continental USA (South Carolina) showed little genetic similarity with any of the native or introduced populations investigated. However, populations from Oahu (HI), New Orleans (LA) and Rutherford County (NC) showed close similarity. In general, genetic patterns suggest multiple introductions to the USA, with, for example, two separate introductions to the island of Maui. Bottleneck effects were detected in almost all recent introductions (after 1940). All populations in the introduced range showed lower genetic diversity than those in the native range. However, this low genetic diversity did not result in the formation of polygynous supercolonies as has been described for other invasive termite and ant species.

Clinal variation in colony breeding structure and level of inbreeding in the subterranean termitesReticulitermes flavipesandR. grassei

Molecular Ecology, 2013

Social insects exhibit remarkable variation in their colony breeding structures, both within and ... more Social insects exhibit remarkable variation in their colony breeding structures, both within and among species. Ecological factors are believed to be important in shaping reproductive traits of social insect colonies, yet there is little information linking specific environmental variables with differences in breeding structure. Subterranean termites (Rhinotermitidae) show exceptional variation in colony breeding structure, differing in the number of reproductives and degree of inbreeding; colonies can be simple families headed by a single pair of monogamous reproductives (king and queen) or they can be extended families headed by multiple inbreeding neotenic reproductives (wingless individuals). Using microsatellite markers, we characterized colony breeding structure and levels of inbreeding in populations over large parts of the range of the subterranean termites Reticulitermes flavipes in the USA and R. grassei in Europe. Combining these new data with previous results on populations of both species, we found that latitude had a strong effect on the proportion of extended-family colonies in R. flavipes and on levels of inbreeding in both species. We examined the effect of several environmental variables that vary latitudinally; while the degree of inbreeding was greatest in cool, moist habitats in both species, seasonality affected the species differently. Inbreeding in R. flavipes was most strongly associated with climatic variables (mean annual temperature and seasonality), whereas nonclimatic variables, including the availability of wood substrate and soil composition, were important predictors of inbreeding in R. grassei. These results are the first showing that termite breeding structure is shaped by local environmental factors and that species can vary in their responses to these factors.

Identification of a queen and king recognition pheromone in the subterranean termite Reticulitermes flavipes

by Ed Vargo and Colin Funaro

Chemical communication is fundamental to success in social insect colonies. Species-, colony-, an... more Chemical communication is fundamental to success in social insect colonies. Species-, colony-, and caste-specific blends of cuticular hydrocarbons (CHCs) and other chemicals have been well documented as pheromones, mediating important behavioral and physiological aspects of social insects. More specifically, royal pheromones used by queens (and kings in termites) enable workers to recognize and care for these vital individuals and maintain the reproductive division of labor. In termites, however, no royal-recognition pheromones have been identified to date. In the current study, solvent extracts of the subterranean termite Reticulitermes flavipes were analyzed to assess differences in cuticular compounds among castes. We identified a royal-specific hydrocarbon—heneicosane—and several previously un-reported and highly royal enriched long-chain alkanes. When applied to glass dummies, heneicosane elicited worker behavioral responses identical to those elicited by live termite queens, including increased vibratory shaking and antennation. Further, the behavioral effects of heneicosane were amplified when presented with nestmate termite workers' cuticular extracts, underscoring the importance of chemical context in termite royal recognition. Thus, heneicosane is a royal-recognition pheromone that is active in both queens and kings of R. flavipes. The use of heneicosane as a queen and king recognition pheromone by termites suggests that CHCs evolved as royal phero-mones ∼150 million years ago, ∼50 million years before their first use as queen-recognition pheromones in social Hymenoptera. We therefore infer that termites and social Hymenoptera convergently evolved the use of these ubiquitous compounds in royal recognition.

Molecular biology meets urban entomology: How molecular biology is changing urban pest management

Urban Insect Pests: Sustainable Management Strategies, P. Dhang, ed. CAB International , 2014

Novel use of aliphatic n-methyl ketones as a fumigant and alternative to methyl bromide for insect control

BACKGROUND: Fumigants like phosphine, methyl bromide and sulfuryl fluoride are highly effective f... more BACKGROUND: Fumigants like phosphine, methyl bromide and sulfuryl fluoride are highly effective for the control of structural, storage and agricultural arthropod pests. Unfortunately, many of these synthetic compounds are highly toxic to people, many pests have developed resistance to these compounds and methyl bromide, the 'gold standard' for fumigants, was de-registered because of its contribution to depletion of the stratospheric ozone layer. Alternative fumigant chemistry is needed. RESULTS: Several plant species produce n-aliphatic methyl ketones to prevent plant herbivory. To examine the use of methyl ketones as a fumigant, structure–mortality studies were conducted using the red imported fire ant, Solenopsis invicta Buren, as a model. A new easy-to-use, inexpensive and disposable bioassay system was developed for this study. The LC 50 values for heptanone, octanone, nonanone and undecanone were 4.27, 5.11, 5.26 and 8.21 í µí»g/cm 3 of ambient air, respectively. Although heptanone, octanone and nonanone were more effective than undecanone, subsequent research was conducted with 2-undecanone because this compound already has US Environmental Protection Agency (EPA) registration as a biopesticide. In dose–response field studies, 12.4 mL of undecanone injected into mounds was the lowest application rate that produced no ant activity in the mound with no re-establishment of ants. Reagent grade undecanone was more cost-effective than methyl bromide for fire ants, adult German cockroaches and tobacco budworm eggs, but slightly more expensive for adult flour beetles. CONCLUSION: The naturally occurring methyl ketone undecanone has the potential to be an alternative to current fumigants for a variety of pest applications.

Efficacy of Chlorantraniliprole in Controlling Structural Infestations of the Eastern Subterranean Termite in the USA

by Ed Vargo, Clay Scherer, and Nicola Gallagher

Subterranean termites are the most economically important structural pests in the USA, and the ea... more Subterranean termites are the most economically important structural pests in the USA, and the eastern subterranean termite, Reticulitermes flavipes (Kollar) (Dictyoptera: Rhinotermitidae) is the most widely distributed species. Soil treatment with a liquid termiticide is a widely used method for controlling subterranean termites in structures. We assessed the efficacy of a nonrepellent termiticide, Altriset ® (active ingredient: chlorantraniliprole), in controlling structural infestations of R. flavipes in Texas, North Carolina, and Ohio and determined the post-treatment fate of termite colonies in and around the structures. In all three states, microsatellite markers indicated that only one R. flavipes colony was infesting each structure. A single chlorantraniliprole treatment provided effective structural protection as there was no further evidence of termite activity in and on the majority of structures from approximately 1 month to 2 years post-treatment when the study concluded. Additionally, the treatment appeared to either severely reduce the infesting colony's footprint at monitors in the landscape or eliminate colony members from these monitors. A supplemental spot-treatment was conducted at one house each in Texas and North Carolina at 5 and 6 months post-treatment, respectively; no termites were observed thereafter in these structures and associated landscaping. The number of colonies found exclusively in the landscape (not attacking the structure) varied among the states, with the largest number of colonies in Texas (0–4) and North Carolina (0–5) as compared to 0–1 in Ohio, the most northern state.

Radiocarbon analysis reveals expanded diet breadth associates with the invasion of a predatory ant

by Ed Vargo, Chihiro Himuro, Kazuki Tsuji, and Kenji Matsuura

Invasions are ecologically destructive and can threaten biodiversity. Trophic flexibility has bee... more Invasions are ecologically destructive and can threaten biodiversity. Trophic flexibility has been proposed as a mechanism facilitating invasion, with more flexible species better able to invade. The termite hunting needle ant Brachyponera chinensis was introduced from East Asia to the United States where it disrupts native ecosystems. We show that B. chinensis has expanded dietary breadth without shifting trophic position in its introduced range. Transect sampling of ants and termites revealed a negative correlation between the abundance of B. chinensis and the abundance of other ants in introduced populations, but this pattern was not as strong in the native range. Both termite and B. chinensis abundance were higher in the introduced range than in native range. Radiocarbon (14 C) analysis revealed that B. chinensis has significantly younger 'diet age', the time lag between carbon fixation by photosynthesis and its use by the consumer, in the introduced range than in the native range, while stable isotope analyses showed no change. These results suggest that in the introduced range B. chinensis remains a termite predator but also feeds on other consumer invertebrates with younger diet ages such as herbivorous insects. Radiocarbon analysis allowed us to elucidate cryptic dietary change associated with invasion success. Tens of thousands of species have been introduced, either intentionally or inadvertently, to locations outside their native ranges 1. A subset of these species become established in the new locations as invasive species where they have negative impacts on native communities and ecosystems. These invasive species are now recognized as the second most important cause of species extinctions 2. Species introductions have been the subject of an enormous body of research with thousands of published articles. However, why some species cause such impacts and others do not remains enigmatic. Ants represent a particularly interesting taxonomic group for studying biological invasions mechanisms as they count among the most ecologically and economically important groups of biological invaders, with five species on the list of the 100 most problematic invaders 3. Invasive ants often become highly abundant in their introduced range where they reduce native ant diversity and affect other organisms both directly and indirectly as has been well-documented for argentine ants 4,5 , fire ants 6 , crazy ants 7–9 , and Asian needle ants 10 among others. The ecological effects of invasive ants in introduced ranges depend on a complex interaction of behavioural, ecological and genetic factors, each independently increasing the numerical abundance of the introduced species relative to native species 11. Recently, a number of studies have highlighted the possibility of species that exhibit behavioral or ecological flexibility may be particularly likely to have strong effects on local communities 12–14 .

Relative Abundance and Comparative Breeding Structure of Subterranean Termite Colonies (<I>Reticulitermes flavipes</I>, <I>Reticulitermes hageni</I>, <I>Reticulitermes virginicus</I>, and <I>Coptotermes formosanus</I>) in a South Carolina Lowcountry Site as Revealed by Molecular Markers

by Ed Vargo and Christopher DeHeer

Annals of the Entomological Society of America, 2006

There are several species of subterranean termites in the United States, some of which occur symp... more There are several species of subterranean termites in the United States, some of which occur sympatrically over broad geographic regions. However, there is little information on the relative abundance of the different species or the extent to which they differ with respect to colony social and spatial organization. We used microsatellite markers to investigate the relative numbers of colonies, to infer colony breeding structures, and to delineate colony foraging areas in four species of subterranean termites occurring in a state park in Charleston, SC. The two most abundant species, Reticulitermes hageni Banks and Reticulitermes flavipes (Kollar), which together accounted for 80% of the 49 colonies sampled, had fairly localized foraging ranges of Ͻ30 m across. In contrast, Reticulitermes virginicus (Banks) and the Formosan subterranean termite, Coptotermes formosanus Shiraki, had far fewer colonies, but these colonies were more expansive, spanning distances Ͼ100 linear m. Colonies of all species were primarily simple families each headed by a single monogamous pair of reproductives. Generally, the remaining colonies of each species were consistent with being extended families, i.e., headed by multiple neotenic reproductives descended from simple families. Only in R. flavipes was a mixed family colony detected, with workers from two distinct families occurring together. These results from molecular markers reveal how the various species in a relatively diverse subterranean termite community can vary in abundance, size of colony foraging area and breeding structure, thereby setting the stage for subsequent studies to identify the factors shaping these communities.

Restricted Gene Flow among Lineages of Thrips tabaci Supports Genetic Divergence Among Cryptic Species Groups

by Ed Vargo and George Kennedy

Knowledge of the relative influence of population-versus species-level genetic variation is impor... more Knowledge of the relative influence of population-versus species-level genetic variation is important to understand patterns of phenotypic variation and ecological relationships that exist among and within morphologically indistinguishable cryptic species and subspecies. In the case of cryptic species groups that are pests, such knowledge is also essential for devising effective population management strategies. The globally important crop pest Thrips tabaci is a taxonomically difficult group of putatively cryptic species. This study examines population genetic structure of T. tabaci and reproductive isolation among lineages of this species complex using microsatellite markers and mitochondrial COI sequences. Overall, genetic structure supports T. tabaci as a cryptic species complex, although limited interbreeding occurs between different clonal groups from the same line-age as well as between individuals from different lineages. These results also provide evidence that thelytoky and arrhenotoky are not fixed phenotypes among members of different T. tabaci lineages that have been generally associated with either reproductive mode. Possible biological and ecological factors contributing to these observations are discussed.

Development of a universal double-digest RAD sequencing approach for a group of nonmodel, ecologically and economically important insect and fish taxa

The generation of genome-scale data is critical for a wide range of questions in basic biology us... more The generation of genome-scale data is critical for a wide range of questions in basic biology using model organisms, but also in questions of applied biology in nonmodel organisms (agriculture, natural resources, conservation and public health biology). Using a genome-scale approach on a diverse group of nonmodel organisms and with the goal of lowering costs of the method, we modified a multiplexed, high-throughput genomic scan technique utilizing two restriction enzymes. We analysed several pairs of restriction enzymes and completed double-digestion RAD sequencing libraries for nine different species and five genera of insects and fish. We found one particular enzyme pair produced consistently higher number of sequence-able fragments across all nine species. Building libraries off this enzyme pair, we found a range of usable SNPs between 4000 and 37 000 SNPS per species and we found a greater number of usable SNPs using reference genomes than de novo pipelines in STACKS. We also found fewer reads in the Read 2 fragments from the paired-end Illumina Hiseq run. Overall, the results of this study provide empirical evidence of the utility of this method for producing consistent data for diverse nonmodel species and suggest specific considerations for sequencing analysis strategies.

Revisiting Coptotermes (Isoptera: Rhinotermitidae): a global taxonomic road map for species validity and distribution of an economically important subterranean termite genus

all named species within the genus and investigated evidence supporting the validity of each name... more all named species within the genus and investigated evidence supporting the validity of each named species. Species were systematically scrutinized according to the region of their original description: Southeast Asia, India, China, Africa, the Neotropics, and Australia. We estimate that of the currently 69

The Mating System of White-Tailed Deer Under Quality Deer Management

by Ed Vargo, Mark Conner, and Warren Booth

Mating systems, which can reveal temporal and spatial plasticity within a given species, may infl... more Mating systems, which can reveal temporal and spatial plasticity within a given species, may influence inbreeding, effective population size, genetic diversity, reproductive fitness, and survival. Although observational research on white-tailed deer has indicated dominant males monopolize breeding opportunities, recent molecular studies suggest a more complex system. It is possible that population characteristics fostered under management strategies designed to balance the sex ratio and extend the male age structure, such as Quality Deer Management (QDM), influence the pre-breeding interactions that affect the distribution of mating success across age classes. Therefore, our objective was to evaluate the white-tailed deer mating system under QDM through paternity analysis. Using 8 microsatellite loci and tissue samples harvested from hunter-killed deer at Chesapeake Farms in Chestertown, Maryland, we evaluated 731 deer. The 3.5 age class dominated mating at Chesapeake Farms, with 41% of paternity. However, together, the 1.5-and 2.5-year-old age classes accounted for more than half of paternity (59%). No evidence of polyandry was detected. Our results indicate the interaction between the sex ratio and age structure, fostered by strategies that balance the sex ratio and extend the male age structure, facilitate breeding by younger males. These results indicate management strategies that employ QDM practices with a goal of propagating the genes of dominant males may fall short, and the interplay among sex ratio, age structure, and dominance relationships may be the main influences of mating success. Managers should account for these findings when setting expectations for reproduction under restricted harvest.

Subterranean termite phylogeography reveals multiple postglacial colonization events in southwestern Europe

by Ed Vargo and Thomas Lefebvre

A long-standing goal of evolutionary biology is to understand how paleocli-matic and geological e... more A long-standing goal of evolutionary biology is to understand how paleocli-matic and geological events shape the geographical distribution and genetic structure within and among species. Using a diverse set of markers (cuticular hydrocarbons, mitochondrial and nuclear gene sequences, microsatellite loci), we studied Reticulitermes grassei and R. banyulensis, two closely related termite species in southwestern Europe. We sought to clarify the current genetic structure of populations that formed following postglacial dispersal from refugia in southern Spain and characterize the gene flow between the two lineages over the last several million years. Each marker type separately provided a fragmented picture of the evolutionary history at different timescales. Chemical analyses of cuticular hydrocarbons and phylogenetic analyses of mitochondrial and nuclear genes showed clear separation between the species, suggesting they diverged following vicariance events in the Late Miocene. However, the presence of intermediate chemical profiles and mtDNA introgression in some Span-ish colonies suggests ongoing gene flow. The current genetic structure of Iberian populations is consistent with alternating isolation and dispersal events during Quaternary glacial periods. Analyses of population genetic structure revealed postglacial colonization routes from southern Spain to France, where populations underwent strong genetic bottlenecks after traversing the Pyrenees resulting in parapatric speciation.

Genome size and ploidy of Thysanoptera

by George Kennedy and Ed Vargo

Insect Molecular Biology, 2013

Flow cytometry was used to study the genome sizes and ploidy levels for four thrips species: Fran... more Flow cytometry was used to study the genome sizes and ploidy levels for four thrips species: Franklinothrips orizabensis Johansen (Thysanoptera: Aeolothripidae), Frankliniella occidentalis Pergande, Frankliniella fusca Hinds, and Thrips tabaci Lindeman (Thysanoptera: Thripidae). F. orizabensis males and females had 1C genome sizes of 426 Mb and 422 Mb, respectively. Male and female F. fusca had 1C genome sizes of 392 Mb and 409 Mb, whereas F. occidentalis males and females had smaller 1C genomes that were 345 Mb and 337 Mb, respectively. Male F. orizabensis, F. occidentalis and F. fusca were haploid and females diploid. Five isofemale lines of T. tabaci, initiated from parthenogenetic, thelytokous females and collected from different locations in North Carolina, were included in this study; no males were available. One isofemale line was diploid with a genome size of 1C = 310 Mb, and the other four had a mean genome size of 1C = 482 Mb, which is consistent with evidence from microsatellite data of diploidy and polyploidy, respectively, in these same five thelytokous lines. This is the first study to produce genome size estimates for thysanopteran species, and report polyploidy in T. tabaci populations.

Unique features of a global human ectoparasite identified through sequencing of the bed bug genome

Nature communications, Jan 2, 2016

The bed bug, Cimex lectularius, has re-established itself as a ubiquitous human ectoparasite thro... more The bed bug, Cimex lectularius, has re-established itself as a ubiquitous human ectoparasite throughout much of the world during the past two decades. This global resurgence is likely linked to increased international travel and commerce in addition to widespread insecticide resistance. Analyses of the C. lectularius sequenced genome (650 Mb) and 14,220 predicted protein-coding genes provide a comprehensive representation of genes that are linked to traumatic insemination, a reduced chemosensory repertoire of genes related to obligate hematophagy, host-symbiont interactions, and several mechanisms of insecticide resistance. In addition, we document the presence of multiple putative lateral gene transfer events. Genome sequencing and annotation establish a solid foundation for future research on mechanisms of insecticide resistance, human-bed bug and symbiont-bed bug associations, and unique features of bed bug biology that contribute to the unprecedented success of C. lectularius as...

Asexual queen succession in the subterranean termite Reticulitermes virginicus

Proceedings of the Royal Society B: Biological Sciences, 2011

Termite colonies are founded by a pair of primary reproductives. In many species, including subte... more Termite colonies are founded by a pair of primary reproductives. In many species, including subterranean termites (family Rhinotermitidae), the primary king and queen can be succeeded by neotenic reproductives that are produced from workers or nymphs within the colony. It is generally believed that these neotenics inbreed within the colony, sometimes for many generations. Here, we show that primary queens of the North American subterranean termite, Reticulitermes virginicus , are replaced by numerous parthenogenetically produced female neotenics. We collected functional female neotenics from five colonies of R. virginicus in North Carolina and Texas, USA. Genetic analysis at eight microsatellite loci showed that 91–100% of the neotenics present within a colony were homozygous at all loci, indicating that they were produced through automictic parthenogenesis with terminal fusion. In contrast, workers, soldiers and alates were almost exclusively sexually produced by mating between the...

Inbreeding and disease resistance in a social insect: effects of heterozygosity on immunocompetence in the termite Zootermopsis angusticollis

Proceedings of the Royal Society B: Biological Sciences, 2006

Recent research has shown that low genetic variation in individuals can increase susceptibility t... more Recent research has shown that low genetic variation in individuals can increase susceptibility to infection and group living may exacerbate pathogen transmission. In the eusocial diploid termites, cycles of outbreeding and inbreeding characterizing basal species can reduce genetic variation within nestmates during the life of a colony, but the relationship of genetic heterogeneity to disease resistance is poorly understood. Here we show that, one generation of inbreeding differentially affects the survivorship of isolated and grouped termites ( Zootermopsis angusticollis) depending on the nature of immune challenge and treatment. Inbred and outbred isolated and grouped termites inoculated with a bacterial pathogen, exposed to a low dose of fungal pathogen or challenged with an implanted nylon monofilament had similar levels of immune defence. However, inbred grouped termites exposed to a relatively high concentration of fungal conidia had significantly greater mortality than outbre...

Thrips tabaci Population Genetic Structure and Polyploidy in Relation to Competency as a Vector of Tomato Spotted Wilt Virus

PLoS ONE, 2013

Knowledge of population-level genetic differences can help explain variation among populations of... more Knowledge of population-level genetic differences can help explain variation among populations of insect vectors in their role in the epidemiology of specific viruses. Variation in competency to transmit Tomato spotted wilt virus (TSWV) that exists among populations of Thrips tabaci has been associated with the presence of cryptic species that exhibit different modes of reproduction and host ranges. However, recent findings suggest that vector competency of T. tabaci at any given location depends on the thrips and virus populations that are present. This study characterizes the population genetic structure of T. tabaci collected from four locations in North Carolina and examines the relationship between population genetic structure and variation in TSWV transmission by T. tabaci. Mitochondrial COI sequence analysis revealed the presence of two genetically distinct groups with one characterized by thelytokous, parthenogenetic reproduction and the other by arrhenotokous, sexual reproduction. Using a set of 11 microsatellite markers that we developed to investigate T. tabaci population genetic structure, we identified 17 clonal groups and found significant genetic structuring among the four NC populations that corresponded to the geographic locations where the populations were collected. Application of microsatellite markers also led to the discovery of polyploidy in this species. All four populations contained tetraploid individuals, and three contained both diploid and tetraploid individuals. Analysis of variation in transmission ofTSWV among isofemale lines initiated with individuals used in this study revealed that 'clone assignment,' 'virus isolate' and their interaction significantly influenced vector competency. These results highlight the importance of interactions between specific T. tabaci clonal types and specific TSWV isolates underlying transmission of TSWV by T. tabaci.

Elimination of Subterranean Termite (Isoptera: Rhinotermitidae) Colonies Using a Refined Cellulose Bait Matrix Containing Noviflumuron When Monitored and Replenished Quarterly

Journal of Economic Entomology, 2012

Using a quarterly (3-mo) monitoring and bait-replenishment interval, 122 subterranean termite col... more Using a quarterly (3-mo) monitoring and bait-replenishment interval, 122 subterranean termite colonies throughout the United States were baited with a reÞned cellulose bait matrix containing 0.5% novißumuron. All colonies were eliminated in less than 1 yr after initiation of baiting as determined by long-term monitoring and genetic markers. Sixty-three percent of the colonies were eliminated during the Þrst quarter after the initiation of baiting and 77% of colonies were eliminated after consuming two bait tubes or less. This suggests that a single baiting cycle and bait installed in response to a single active monitoring device were sufÞcient to eliminate the majority of colonies. Although termites temporarily abandoned stations after depleting bait, workers resumed feeding when baits were replenished. Colonies that consumed large amounts of bait before elimination foraged into multiple stations, thus allowing adequate amounts of bait to sustain feeding. The time to eliminate termite colonies with bait replenished quarterly was similar to that previously reported for laminated cellulose bait replenished monthly. Our data support the conclusion that extending the bait replenishment interval from monthly to quarterly for bait tubes with reÞned cellulose containing 0.5% novißumuron did not adversely impact colony elimination.

Genetic Analysis of Colony and Population Structure of Three Introduced Populations of the Formosan Subterranean Termite (Isoptera: Rhinotermitidae) in the Continental United States

Environmental Entomology, 2006

The Formosan subterranean termite, Coptotermes formosanus Shiraki, is a major invasive pest speci... more The Formosan subterranean termite, Coptotermes formosanus Shiraki, is a major invasive pest species in many parts of the world. We compared the colony breeding system and population genetic structure in three introduced populations in the continental United States: Charleston, SC; City Park, New Orleans, LA; and Rutherford County, NC. Based on worker genotypes at 12 microsatellite loci, we found that colonies were mainly genetically distinct entities consisting of either simple families headed by monogamous pairs of reproductives or extended families containing multiple neotenic (replacement) reproductives descended from simple families. Populations varied from 48% simple families in Charleston to 82% simple families in City Park. Extended family colonies in all three populations were likely headed by Ͻ10 neotenic reproductives. There was no signiÞcant isolation by distance in any of the populations, suggesting that colonies reproduce by relatively long-range mating ßights and/or human-mediated dispersal within each population. The Charleston population showed evidence of a recent genetic bottleneck and most likely was founded by very few colonies. Cluster analysis indicated that the Charleston and City Park populations are quite genetically distant from each other and most likely originated from different source populations. The more recently introduced Rutherford County population was genetically most similar to City Park. These Þndings, together with results from other infested sites, indicate considerable variation in the genetic structure and breeding system of introduced populations of this species, making it unlikely that there is a simple genetic or behavioral explanation for the success of C. formosanus as an invasive species.

Genetic diversity and colony breeding structure in native and introduced ranges of the Formosan subterranean termite, Coptotermes formosanus

Biological Invasions, 2011

The Formosan subterranean termite, Coptotermes formosanus is recognized as one of the most import... more The Formosan subterranean termite, Coptotermes formosanus is recognized as one of the most important invasive pest species. Originating from China, C. formosanus has spread to many tropical and subtropical regions around the globe in the last 400 years, including Japan, Hawaii and the continental USA. Although the current distribution is well documented, information about the patterns of invasion and effects of introduction on the population genetics of this species is largely lacking. We analyzed the genetic structure of populations from two native populations (Guangdong and Hunan provinces, China) and two introduced populations (Maui and Kauai, Hawaii) using microsatellite genotyping. We also reanalyzed published data of additional populations from China, Japan, Hawaii, and the continental USA. The population from Hunan, the earliest introduction outside of China (Japan) and the first introduction to the continental USA (South Carolina) showed little genetic similarity with any of the native or introduced populations investigated. However, populations from Oahu (HI), New Orleans (LA) and Rutherford County (NC) showed close similarity. In general, genetic patterns suggest multiple introductions to the USA, with, for example, two separate introductions to the island of Maui. Bottleneck effects were detected in almost all recent introductions (after 1940). All populations in the introduced range showed lower genetic diversity than those in the native range. However, this low genetic diversity did not result in the formation of polygynous supercolonies as has been described for other invasive termite and ant species.

Clinal variation in colony breeding structure and level of inbreeding in the subterranean termitesReticulitermes flavipesandR. grassei

Molecular Ecology, 2013

Social insects exhibit remarkable variation in their colony breeding structures, both within and ... more Social insects exhibit remarkable variation in their colony breeding structures, both within and among species. Ecological factors are believed to be important in shaping reproductive traits of social insect colonies, yet there is little information linking specific environmental variables with differences in breeding structure. Subterranean termites (Rhinotermitidae) show exceptional variation in colony breeding structure, differing in the number of reproductives and degree of inbreeding; colonies can be simple families headed by a single pair of monogamous reproductives (king and queen) or they can be extended families headed by multiple inbreeding neotenic reproductives (wingless individuals). Using microsatellite markers, we characterized colony breeding structure and levels of inbreeding in populations over large parts of the range of the subterranean termites Reticulitermes flavipes in the USA and R. grassei in Europe. Combining these new data with previous results on populations of both species, we found that latitude had a strong effect on the proportion of extended-family colonies in R. flavipes and on levels of inbreeding in both species. We examined the effect of several environmental variables that vary latitudinally; while the degree of inbreeding was greatest in cool, moist habitats in both species, seasonality affected the species differently. Inbreeding in R. flavipes was most strongly associated with climatic variables (mean annual temperature and seasonality), whereas nonclimatic variables, including the availability of wood substrate and soil composition, were important predictors of inbreeding in R. grassei. These results are the first showing that termite breeding structure is shaped by local environmental factors and that species can vary in their responses to these factors.

Identification of a queen and king recognition pheromone in the subterranean termite Reticulitermes flavipes

by Ed Vargo and Colin Funaro

Chemical communication is fundamental to success in social insect colonies. Species-, colony-, an... more Chemical communication is fundamental to success in social insect colonies. Species-, colony-, and caste-specific blends of cuticular hydrocarbons (CHCs) and other chemicals have been well documented as pheromones, mediating important behavioral and physiological aspects of social insects. More specifically, royal pheromones used by queens (and kings in termites) enable workers to recognize and care for these vital individuals and maintain the reproductive division of labor. In termites, however, no royal-recognition pheromones have been identified to date. In the current study, solvent extracts of the subterranean termite Reticulitermes flavipes were analyzed to assess differences in cuticular compounds among castes. We identified a royal-specific hydrocarbon—heneicosane—and several previously un-reported and highly royal enriched long-chain alkanes. When applied to glass dummies, heneicosane elicited worker behavioral responses identical to those elicited by live termite queens, including increased vibratory shaking and antennation. Further, the behavioral effects of heneicosane were amplified when presented with nestmate termite workers' cuticular extracts, underscoring the importance of chemical context in termite royal recognition. Thus, heneicosane is a royal-recognition pheromone that is active in both queens and kings of R. flavipes. The use of heneicosane as a queen and king recognition pheromone by termites suggests that CHCs evolved as royal phero-mones ∼150 million years ago, ∼50 million years before their first use as queen-recognition pheromones in social Hymenoptera. We therefore infer that termites and social Hymenoptera convergently evolved the use of these ubiquitous compounds in royal recognition.

Molecular biology meets urban entomology: How molecular biology is changing urban pest management

Urban Insect Pests: Sustainable Management Strategies, P. Dhang, ed. CAB International , 2014

Novel use of aliphatic n-methyl ketones as a fumigant and alternative to methyl bromide for insect control

BACKGROUND: Fumigants like phosphine, methyl bromide and sulfuryl fluoride are highly effective f... more BACKGROUND: Fumigants like phosphine, methyl bromide and sulfuryl fluoride are highly effective for the control of structural, storage and agricultural arthropod pests. Unfortunately, many of these synthetic compounds are highly toxic to people, many pests have developed resistance to these compounds and methyl bromide, the 'gold standard' for fumigants, was de-registered because of its contribution to depletion of the stratospheric ozone layer. Alternative fumigant chemistry is needed. RESULTS: Several plant species produce n-aliphatic methyl ketones to prevent plant herbivory. To examine the use of methyl ketones as a fumigant, structure–mortality studies were conducted using the red imported fire ant, Solenopsis invicta Buren, as a model. A new easy-to-use, inexpensive and disposable bioassay system was developed for this study. The LC 50 values for heptanone, octanone, nonanone and undecanone were 4.27, 5.11, 5.26 and 8.21 í µí»g/cm 3 of ambient air, respectively. Although heptanone, octanone and nonanone were more effective than undecanone, subsequent research was conducted with 2-undecanone because this compound already has US Environmental Protection Agency (EPA) registration as a biopesticide. In dose–response field studies, 12.4 mL of undecanone injected into mounds was the lowest application rate that produced no ant activity in the mound with no re-establishment of ants. Reagent grade undecanone was more cost-effective than methyl bromide for fire ants, adult German cockroaches and tobacco budworm eggs, but slightly more expensive for adult flour beetles. CONCLUSION: The naturally occurring methyl ketone undecanone has the potential to be an alternative to current fumigants for a variety of pest applications.

Efficacy of Chlorantraniliprole in Controlling Structural Infestations of the Eastern Subterranean Termite in the USA

by Ed Vargo, Clay Scherer, and Nicola Gallagher

Subterranean termites are the most economically important structural pests in the USA, and the ea... more Subterranean termites are the most economically important structural pests in the USA, and the eastern subterranean termite, Reticulitermes flavipes (Kollar) (Dictyoptera: Rhinotermitidae) is the most widely distributed species. Soil treatment with a liquid termiticide is a widely used method for controlling subterranean termites in structures. We assessed the efficacy of a nonrepellent termiticide, Altriset ® (active ingredient: chlorantraniliprole), in controlling structural infestations of R. flavipes in Texas, North Carolina, and Ohio and determined the post-treatment fate of termite colonies in and around the structures. In all three states, microsatellite markers indicated that only one R. flavipes colony was infesting each structure. A single chlorantraniliprole treatment provided effective structural protection as there was no further evidence of termite activity in and on the majority of structures from approximately 1 month to 2 years post-treatment when the study concluded. Additionally, the treatment appeared to either severely reduce the infesting colony's footprint at monitors in the landscape or eliminate colony members from these monitors. A supplemental spot-treatment was conducted at one house each in Texas and North Carolina at 5 and 6 months post-treatment, respectively; no termites were observed thereafter in these structures and associated landscaping. The number of colonies found exclusively in the landscape (not attacking the structure) varied among the states, with the largest number of colonies in Texas (0–4) and North Carolina (0–5) as compared to 0–1 in Ohio, the most northern state.

Radiocarbon analysis reveals expanded diet breadth associates with the invasion of a predatory ant

by Ed Vargo, Chihiro Himuro, Kazuki Tsuji, and Kenji Matsuura

Invasions are ecologically destructive and can threaten biodiversity. Trophic flexibility has bee... more Invasions are ecologically destructive and can threaten biodiversity. Trophic flexibility has been proposed as a mechanism facilitating invasion, with more flexible species better able to invade. The termite hunting needle ant Brachyponera chinensis was introduced from East Asia to the United States where it disrupts native ecosystems. We show that B. chinensis has expanded dietary breadth without shifting trophic position in its introduced range. Transect sampling of ants and termites revealed a negative correlation between the abundance of B. chinensis and the abundance of other ants in introduced populations, but this pattern was not as strong in the native range. Both termite and B. chinensis abundance were higher in the introduced range than in native range. Radiocarbon (14 C) analysis revealed that B. chinensis has significantly younger 'diet age', the time lag between carbon fixation by photosynthesis and its use by the consumer, in the introduced range than in the native range, while stable isotope analyses showed no change. These results suggest that in the introduced range B. chinensis remains a termite predator but also feeds on other consumer invertebrates with younger diet ages such as herbivorous insects. Radiocarbon analysis allowed us to elucidate cryptic dietary change associated with invasion success. Tens of thousands of species have been introduced, either intentionally or inadvertently, to locations outside their native ranges 1. A subset of these species become established in the new locations as invasive species where they have negative impacts on native communities and ecosystems. These invasive species are now recognized as the second most important cause of species extinctions 2. Species introductions have been the subject of an enormous body of research with thousands of published articles. However, why some species cause such impacts and others do not remains enigmatic. Ants represent a particularly interesting taxonomic group for studying biological invasions mechanisms as they count among the most ecologically and economically important groups of biological invaders, with five species on the list of the 100 most problematic invaders 3. Invasive ants often become highly abundant in their introduced range where they reduce native ant diversity and affect other organisms both directly and indirectly as has been well-documented for argentine ants 4,5 , fire ants 6 , crazy ants 7–9 , and Asian needle ants 10 among others. The ecological effects of invasive ants in introduced ranges depend on a complex interaction of behavioural, ecological and genetic factors, each independently increasing the numerical abundance of the introduced species relative to native species 11. Recently, a number of studies have highlighted the possibility of species that exhibit behavioral or ecological flexibility may be particularly likely to have strong effects on local communities 12–14 .

Relative Abundance and Comparative Breeding Structure of Subterranean Termite Colonies (<I>Reticulitermes flavipes</I>, <I>Reticulitermes hageni</I>, <I>Reticulitermes virginicus</I>, and <I>Coptotermes formosanus</I>) in a South Carolina Lowcountry Site as Revealed by Molecular Markers

by Ed Vargo and Christopher DeHeer

Annals of the Entomological Society of America, 2006

There are several species of subterranean termites in the United States, some of which occur symp... more There are several species of subterranean termites in the United States, some of which occur sympatrically over broad geographic regions. However, there is little information on the relative abundance of the different species or the extent to which they differ with respect to colony social and spatial organization. We used microsatellite markers to investigate the relative numbers of colonies, to infer colony breeding structures, and to delineate colony foraging areas in four species of subterranean termites occurring in a state park in Charleston, SC. The two most abundant species, Reticulitermes hageni Banks and Reticulitermes flavipes (Kollar), which together accounted for 80% of the 49 colonies sampled, had fairly localized foraging ranges of Ͻ30 m across. In contrast, Reticulitermes virginicus (Banks) and the Formosan subterranean termite, Coptotermes formosanus Shiraki, had far fewer colonies, but these colonies were more expansive, spanning distances Ͼ100 linear m. Colonies of all species were primarily simple families each headed by a single monogamous pair of reproductives. Generally, the remaining colonies of each species were consistent with being extended families, i.e., headed by multiple neotenic reproductives descended from simple families. Only in R. flavipes was a mixed family colony detected, with workers from two distinct families occurring together. These results from molecular markers reveal how the various species in a relatively diverse subterranean termite community can vary in abundance, size of colony foraging area and breeding structure, thereby setting the stage for subsequent studies to identify the factors shaping these communities.

Restricted Gene Flow among Lineages of Thrips tabaci Supports Genetic Divergence Among Cryptic Species Groups

by Ed Vargo and George Kennedy

Knowledge of the relative influence of population-versus species-level genetic variation is impor... more Knowledge of the relative influence of population-versus species-level genetic variation is important to understand patterns of phenotypic variation and ecological relationships that exist among and within morphologically indistinguishable cryptic species and subspecies. In the case of cryptic species groups that are pests, such knowledge is also essential for devising effective population management strategies. The globally important crop pest Thrips tabaci is a taxonomically difficult group of putatively cryptic species. This study examines population genetic structure of T. tabaci and reproductive isolation among lineages of this species complex using microsatellite markers and mitochondrial COI sequences. Overall, genetic structure supports T. tabaci as a cryptic species complex, although limited interbreeding occurs between different clonal groups from the same line-age as well as between individuals from different lineages. These results also provide evidence that thelytoky and arrhenotoky are not fixed phenotypes among members of different T. tabaci lineages that have been generally associated with either reproductive mode. Possible biological and ecological factors contributing to these observations are discussed.

Development of a universal double-digest RAD sequencing approach for a group of nonmodel, ecologically and economically important insect and fish taxa

The generation of genome-scale data is critical for a wide range of questions in basic biology us... more The generation of genome-scale data is critical for a wide range of questions in basic biology using model organisms, but also in questions of applied biology in nonmodel organisms (agriculture, natural resources, conservation and public health biology). Using a genome-scale approach on a diverse group of nonmodel organisms and with the goal of lowering costs of the method, we modified a multiplexed, high-throughput genomic scan technique utilizing two restriction enzymes. We analysed several pairs of restriction enzymes and completed double-digestion RAD sequencing libraries for nine different species and five genera of insects and fish. We found one particular enzyme pair produced consistently higher number of sequence-able fragments across all nine species. Building libraries off this enzyme pair, we found a range of usable SNPs between 4000 and 37 000 SNPS per species and we found a greater number of usable SNPs using reference genomes than de novo pipelines in STACKS. We also found fewer reads in the Read 2 fragments from the paired-end Illumina Hiseq run. Overall, the results of this study provide empirical evidence of the utility of this method for producing consistent data for diverse nonmodel species and suggest specific considerations for sequencing analysis strategies.

Revisiting Coptotermes (Isoptera: Rhinotermitidae): a global taxonomic road map for species validity and distribution of an economically important subterranean termite genus

all named species within the genus and investigated evidence supporting the validity of each name... more all named species within the genus and investigated evidence supporting the validity of each named species. Species were systematically scrutinized according to the region of their original description: Southeast Asia, India, China, Africa, the Neotropics, and Australia. We estimate that of the currently 69

The Mating System of White-Tailed Deer Under Quality Deer Management

by Ed Vargo, Mark Conner, and Warren Booth

Mating systems, which can reveal temporal and spatial plasticity within a given species, may infl... more Mating systems, which can reveal temporal and spatial plasticity within a given species, may influence inbreeding, effective population size, genetic diversity, reproductive fitness, and survival. Although observational research on white-tailed deer has indicated dominant males monopolize breeding opportunities, recent molecular studies suggest a more complex system. It is possible that population characteristics fostered under management strategies designed to balance the sex ratio and extend the male age structure, such as Quality Deer Management (QDM), influence the pre-breeding interactions that affect the distribution of mating success across age classes. Therefore, our objective was to evaluate the white-tailed deer mating system under QDM through paternity analysis. Using 8 microsatellite loci and tissue samples harvested from hunter-killed deer at Chesapeake Farms in Chestertown, Maryland, we evaluated 731 deer. The 3.5 age class dominated mating at Chesapeake Farms, with 41% of paternity. However, together, the 1.5-and 2.5-year-old age classes accounted for more than half of paternity (59%). No evidence of polyandry was detected. Our results indicate the interaction between the sex ratio and age structure, fostered by strategies that balance the sex ratio and extend the male age structure, facilitate breeding by younger males. These results indicate management strategies that employ QDM practices with a goal of propagating the genes of dominant males may fall short, and the interplay among sex ratio, age structure, and dominance relationships may be the main influences of mating success. Managers should account for these findings when setting expectations for reproduction under restricted harvest.

Subterranean termite phylogeography reveals multiple postglacial colonization events in southwestern Europe

by Ed Vargo and Thomas Lefebvre

A long-standing goal of evolutionary biology is to understand how paleocli-matic and geological e... more A long-standing goal of evolutionary biology is to understand how paleocli-matic and geological events shape the geographical distribution and genetic structure within and among species. Using a diverse set of markers (cuticular hydrocarbons, mitochondrial and nuclear gene sequences, microsatellite loci), we studied Reticulitermes grassei and R. banyulensis, two closely related termite species in southwestern Europe. We sought to clarify the current genetic structure of populations that formed following postglacial dispersal from refugia in southern Spain and characterize the gene flow between the two lineages over the last several million years. Each marker type separately provided a fragmented picture of the evolutionary history at different timescales. Chemical analyses of cuticular hydrocarbons and phylogenetic analyses of mitochondrial and nuclear genes showed clear separation between the species, suggesting they diverged following vicariance events in the Late Miocene. However, the presence of intermediate chemical profiles and mtDNA introgression in some Span-ish colonies suggests ongoing gene flow. The current genetic structure of Iberian populations is consistent with alternating isolation and dispersal events during Quaternary glacial periods. Analyses of population genetic structure revealed postglacial colonization routes from southern Spain to France, where populations underwent strong genetic bottlenecks after traversing the Pyrenees resulting in parapatric speciation.

Genome size and ploidy of Thysanoptera

by George Kennedy and Ed Vargo

Insect Molecular Biology, 2013

Flow cytometry was used to study the genome sizes and ploidy levels for four thrips species: Fran... more Flow cytometry was used to study the genome sizes and ploidy levels for four thrips species: Franklinothrips orizabensis Johansen (Thysanoptera: Aeolothripidae), Frankliniella occidentalis Pergande, Frankliniella fusca Hinds, and Thrips tabaci Lindeman (Thysanoptera: Thripidae). F. orizabensis males and females had 1C genome sizes of 426 Mb and 422 Mb, respectively. Male and female F. fusca had 1C genome sizes of 392 Mb and 409 Mb, whereas F. occidentalis males and females had smaller 1C genomes that were 345 Mb and 337 Mb, respectively. Male F. orizabensis, F. occidentalis and F. fusca were haploid and females diploid. Five isofemale lines of T. tabaci, initiated from parthenogenetic, thelytokous females and collected from different locations in North Carolina, were included in this study; no males were available. One isofemale line was diploid with a genome size of 1C = 310 Mb, and the other four had a mean genome size of 1C = 482 Mb, which is consistent with evidence from microsatellite data of diploidy and polyploidy, respectively, in these same five thelytokous lines. This is the first study to produce genome size estimates for thysanopteran species, and report polyploidy in T. tabaci populations.