Papers by Javier delBarco-Trillo
Research Square (Research Square), Oct 12, 2022
The sustained expansion of urban environments has been paralleled by an increase in the number of... more The sustained expansion of urban environments has been paralleled by an increase in the number of studies investigating the phenotypic changes of animals driven by urbanization. Most of these studies have been con ned to only one urban center. However, as the types and strength of anthropogenic stressors differ across cities, a generalizable understanding of the effects of urbanization on urbandwelling species can only be reached by comparing the responses of urban populations from the same species across more than one city. We conducted phylogenetic meta-analyses on data for animal species (including both invertebrates and vertebrates) for which measures about any morphological, physiological, or behavioral trait were reported for two or more cities. We found that morphological, physiological and behavioral traits of urban animals all differ similarly across cities, and that such phenotypic differences across cities increase as the more cities were investigated in any given study. We also found support for phenotypic differences across cities being more pronounced as the farther away cities are from each other. Our results clearly indicate that separate urban populations of the same species can diverge phenotypically, and support previous pleas from many researchers to conduct urban studies across several urban populations. We particularly recommend that future studies choose cities in different biomes, as urban adaptations may differ substantially in cities sited in different ecological matrices. Ultimately, a generalized knowledge about how organisms are affected by urbanization will only be possible when comprehensive biological patterns are similarly studied across separate and distinct cities.
As the natural habitats of many species are degraded or disappear, there is scope for these speci... more As the natural habitats of many species are degraded or disappear, there is scope for these species to be established in urban habitats. To ease the establishment and maintenance of urban populations of more species we need to better understand what degree of phenotypical change to expect as different species transition into urban environments. During the first stages of urban colonization, behavioural changes such as an increase in boldness are particularly important. A consistent response in urban populations is to decrease the distance at which individuals flee from an approaching human (flight initiation distance, or FID). Performing a phylogenetic generalized least-squares (PGLS) analysis on 130 avian species, I found that the largest changes in FID between rural and urban populations occur in species that are larger-bodied and naturally shy (higher rural FID), two phenotypic traits that are not normally associated with urban colonizers. More unlikely species may thus be able to colonize urban environments, especially if we design cities in ways that promote such urban colonizations.
Total DNA fragmentation index (tDFI) and high DNA stainability (HDS) results obtained by Sperm Ch... more Total DNA fragmentation index (tDFI) and high DNA stainability (HDS) results obtained by Sperm Chromatin Structure Assay (SCSA)
Dong wu xue bao. [Acta Zoologica Sinica], 2005
R code used for the analyses
A comparison of human chorionic gonadotropin releasing hormone on (90 % vs. 75%) by nine hours po... more A comparison of human chorionic gonadotropin releasing hormone on (90 % vs. 75%) by nine hours post-administration. Kouba et al. Reproductive Biology and Endocrinology 2012, 10:59
Journal of Urban Ecology, 2020
Animals colonising urban environments are exposed to a series of novel stressors and ecological c... more Animals colonising urban environments are exposed to a series of novel stressors and ecological challenges, which can result in adaptations to alternative urban niches. Tardigrades are cosmopolitan invertebrates present in all types of ecosystems, including urban environments; and they can survive under extreme conditions, including periods of desiccation, thus allowing them to colonise novel harsh habitats. Tardigrades are thus a promising model to investigate the challenges and opportunities encountered by urban colonisers. Our aims were 1, to determine if tardigrade abundance in natural substrates (moss, lichen and leaf litter) differs between rural and urban sites and 2, to assess if tardigrades have successfully colonised urban substrates that are highly anthropogenic (road sediment, and material accumulated under cars and in wall crevices). Among natural substrates, we found fewer tardigrades in Cork city than in rural sites. However, in urban sites we found no differences bet...
Journal for Nature Conservation, 2020
Wildlife rehabilitation is an increasingly important and global practice, aiming towards advancem... more Wildlife rehabilitation is an increasingly important and global practice, aiming towards advancements in animal welfare and species conservation. Although there are ongoing discussions on the benefits and limitations of wildlife rehabilitation, there is a general agreement on the importance of wildlife rehabilitation on improving the welfare of wild animals and identifying threats to wildlife. Determining which factors lead to a successful outcome of rehabilitation can allow wildlife rehabilitation centres to best focus their resources to benefit animals with the greatest chance of a successful release. In this study, three factors affecting the success of rehabilitation were evaluated: taxonomic group, life stage and circumstance of rescue. We used a large database of patients' records (9561 animals from 198 species) from Sandy Pines Wildlife Centre (Ontario, Canada) over a three year study period (from 2015 to 2018). We found that reptiles had a higher rate of release (63.6 %), compared with mammals (42.1 %) and birds (48.3 %), although released reptiles spent longer in the centre than birds and mammals. Animals arriving to the centre in poor condition were less likely to be rehabilitated and spent longer in the centre than animals arriving in good condition. Overall, preadults were more likely to be released than adults, although the number of days spent at the centre did not differ by life stage. Animals suffering active damage (e.g. 'collision' and 'projectile') were less likely to be rehabilitated than animals suffering passive damage (e.g. arriving to the centre as 'orphan' or due to 'habitat destruction'); however, when only considering those animals that left the centre, the number of days spent at the centre did not differ between animals suffering passive or active damage. The analysis of patients' records can provide relevant information to rehabilitators about factors influencing rehabilitation efforts, which can be used to implement strategies that maximise release rates, given limited resources.
Journal of Urban Ecology, 2020
The unprecedented growth rate in human population and the increasing movement of people to urban ... more The unprecedented growth rate in human population and the increasing movement of people to urban areas is causing a rapid increase in urbanisation globally. Urban environments may restrict or affect the behaviour of many animal species. Importantly, urban populations may change their spatial movement, particularly decreasing their home ranges in response to habitat fragmentation, the presence of landscape barriers and the availability and density of resources. Several species-specific studies suggest that urban animals decrease their home ranges compared with their non-urban counterparts; however, it remained unclear whether this pattern is widespread across taxa or is instead restricted to specific taxonomic groups. Consequently, we conducted a meta-analysis, collecting 41 sets of data comparing home ranges in both natural and urban environments in 32 species of reptiles, birds and mammals. We calculated effect sizes as the difference in animal home range sizes between natural and ...
Basic and Applied Ecology, 2018
The effect of management practices on bumblebee densities in hedgerow and grassland habitats Runn... more The effect of management practices on bumblebee densities in hedgerow and grassland habitats Running head: Management type and bumblebee density
Reproductive Biology and Endocrinology, 2012
Background: Captive breeding programs for endangered amphibian species often utilize exogenous ho... more Background: Captive breeding programs for endangered amphibian species often utilize exogenous hormones for species that are difficult to breed. The purpose of our study was to compare the efficacy of two different hormones at various concentrations on sperm production, quantity and quality over time in order to optimize assisted breeding. Methods: Male American toads (Anaxyrus americanus) were divided into three separate treatment groups, with animals in each group rotated through different concentrations of luteinizing hormone releasing hormone analog (LHRH; 0.1, 1.0, 4.0 and 32 micrograms/toad), human chorionic gonadotropin (hCG; 50, 100, 200, and 300 IU), or the control over 24 hours. We evaluated the number of males that respond by producing spermic urine, the sperm concentration, percent motility, and quality of forward progression. We also evaluated the effects of hCG and LHRH on reproductive behavior as assessed by amplexus. Data were analyzed using the Generalized Estimating Equations incorporating repeated measures over time and including the main effects of treatment and time, and the treatment by time interaction. Results: The hormone hCG was significantly more effective at stimulating spermiation in male Anaxyrus americanus than LHRH and showed a dose-dependent response in the number of animals producing sperm. At the most effective hCG dose (300 IU), 100% of the male toads produced sperm, compared to only 35% for the best LHRH dose tested (4.0 micrograms). In addition to having a greater number of responders (P < 0.05), the 300 IU hCG treatment group had a much higher average sperm concentration (P < 0.05) than the treatment group receiving 4.0 micrograms LHRH. In contrast, these two treatments did not result in significant differences in sperm motility or quality of forward progressive motility. However, more males went into amplexus when treated with LHRH vs. hCG (90% vs. 75%) by nine hours post-administration. Conclusion: There is a clear dichotomy between the two hormones' physiological responses on gamete production and stimulation of amplexus. Understanding how these two hormones influence physiology and reproductive behaviors in amphibians will have direct bearing on establishing similar breeding protocols for endangered species.
Physiology & Behavior, 2007
Anogenital distance (AGD) in rodents is a useful indicator of masculinization or feminization due... more Anogenital distance (AGD) in rodents is a useful indicator of masculinization or feminization due to prenatal hormonal effects. If such cues convey useful information about both &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;maleness&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; and more importantly mate quality, then females may select males based on this cue or other cues related to it. We tested this hypothesis by asking if female prairie voles (Microtus ochrogaster) preferred males with relatively longer AGDs and if AGD correlated with fitness enhancing characteristics such as sperm count, sperm size, and gonad size. Not only did preferred males have significantly longer AGD and larger testes than nonpreferred males, but AGD was directly related to the testes size, seminal vesicle size, and the number of sperm stored. We re-evaluated data collected in semi-natural field enclosures and discovered that males that were members of a pairbond had longer AGD than single males. This later result, taken under semi-natural conditions, was consistent with results we obtained in the laboratory. Taken together these data indicate that AGD serves as a useful cue of male potency and that females preferentially associate with males that demonstrate this masculinized phenotype. Moreover, these data imply that females may select mates based on their potential to effectively fertilize ova, a potentially important trait for a species that forms life-long pairbonds.
Journal of Evolutionary Biology, 2011
Sperm competition theory predicts that under high risk of sperm competition, males will increase ... more Sperm competition theory predicts that under high risk of sperm competition, males will increase the number of sperm that they allocate to a female. This prediction has been supported by some experimental studies but not by others. Here, I conducted a meta-analysis to determine whether the increase in sperm allocation under high risk of sperm competition is a generalized response across taxa. I collected data from 39 studies and 37 species. Across taxa, males under a high risk of sperm competition respond by increasing their sperm allocation (mean effect size = 0.32). Number of offspring did not explain a significant portion of the variation in effect sizes. A traditional meta-analysis (i.e. without phylogenetic information) described the variation among effect sizes better than a meta-analysis that incorporates the phylogenetic relationships among species, suggesting that the increase in sperm allocation under high risk of sperm competition is similarly prevalent across taxa.
Animal Behaviour, 2009
In laboratory studies, hamsters (Mesocricetus spp.) exhibit intense male-male aggression, thus ma... more In laboratory studies, hamsters (Mesocricetus spp.) exhibit intense male-male aggression, thus making them an excellent model system for studies of the functional and mechanistic bases of aggression. In a field study of golden hamsters (M. auratus) in the wild, however, the few documented male-male interactions were not highly aggressive. Thus, we tested the hypothesis that familiarity modulates aggression in hamsters. Previous investigations of the effects of familiarity on aggression have mostly involved familiarization of unfamiliar individuals through agonistic interactions. Here we allowed male Turkish hamsters (M. brandti) to become familiar with each other by housing them together but separated by a wire-mesh partition (thus 'non-agonistic' familiarity). We found that although non-agonistic familiarity did not decrease investigation of the familiar male, it did decrease the occurrence of fights, the number of fights, and the percentage of time fighting; it also increased the latency to fight. These results are consistent with the 'dear enemy' hypothesis, which proposes that males are less aggressive toward familiar neighbors than to unfamiliar conspecifics because previous interactions have provided enough information about the other individual to render severe aggression unnecessary. Most importantly, our results suggest that information gained about other individuals through non-agonistic interactions decrease the frequency and intensity of fights with those individuals. We conclude that results from laboratory studies on aggression that do not consider the kind of social interactions that individuals have in nature should be interpreted with caution.
Aggressive Behavior, 2010
In many species, young males are the dispersers, leaving their natal area after weaning to 21 est... more In many species, young males are the dispersers, leaving their natal area after weaning to 21 establish a breeding area of their own. As young males disperse, however, they are bound to encounter unfamiliar adult males with established territories. Such interactions 23 between an adult male and a young male may always be agonistic. Alternatively, there 24 may be an age threshold below which aggression is not elicited and above which the 25 adult male is aggressive toward the juvenile male. To test these two alternative 26 hypotheses, we paired 47 young Syrian hamster (Mesocricetus auratus) males ranging 27 from 24 to 65 days of age with 47 adult male hamsters and measured aggressive and 28 investigatory behavior for 5 minutes. We observed no aggression by the adult toward 29 young males between 24 to 47 days of age or toward the single male that was 49 days of 30 age. Young males that were 50 days of age or older, however, elicited significant levels 31 of aggression from the adults. These results indicate that in Syrian hamsters, young males 32 are less vulnerable to adult aggression up to an age threshold and are more vulnerable to 33 adult aggression beyond that threshold. This pattern may facilitate the establishment of 34 territories by dispersing young males below that age threshold. 35
There are 2 models of male adjustment of sperm investment in the ejaculate in relation to sperm c... more There are 2 models of male adjustment of sperm investment in the ejaculate in relation to sperm competition. The ''risk model'' predicts that as ''risk'' of sperm competition increases, sperm investment also increases. This prediction has been supported in many species, including mammals. The ''intensity model'' involves the number of competing males copulating with the same female and predicts that males will allocate the highest sperm investment at low sperm competition intensity (SCI) and then decreasing sperm investments as SCI increases. Two alternative outcomes are that sperm investment is unaffected by SCI and that sperm investment increases as SCI increases. There are studies supporting all 3 possible outcomes in relation to SCI but no data on mammals. The present paper presents the first study of SCI in a mammal species, the meadow vole, Microtus pennsylvanicus. We used odors of conspecific males to simulate low and high intensities of sperm competition. We found that males allocate the highest sperm investment at low SCI and decrease significantly their sperm investment at high SCI. We also found that males allocate the lowest sperm investment at low sperm competition risk (SCR) and the highest sperm investment at high SCR. All these results agree with current theoretical models of sperm competition.
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Papers by Javier delBarco-Trillo