Papers by Douglas Eernisse
Insight into the origin and early evolution of the animal phyla requires an understanding of how ... more Insight into the origin and early evolution of the animal phyla requires an understanding of how animal groups are related to one another. Thus, we set out to explore animal phylogeny by analyzing with maximum parsimony 138 morphological characters from 40 metazoan groups, and 304 18S rDNA sequences, both separately and together. Both types of data agree that arthropods are not closely related to annelids: the former group with nematodes and other molting animals (Ecdysozoa), and the latter group with molluscs and other taxa with spiral cleavage. Furthermore, neither brachiopods nor chaetognaths group with deuterostomes; brachiopods are allied with the molluscs and annelids (Lophotrochozoa), whereas chaetognaths are allied with the ecdysozoans. The major discordance between the two types of data concerns the rooting of the bilaterians, and the bilaterian sister-taxon. Morphology suggests that the root is between deuterostomes and protostomes, with ctenophores the bilaterian sister-group, whereas 18S rDNA suggests that the root is within the Lophotrochozoa with acoel flatworms and gnathostomulids as basal bilaterians, and with cnidarians the bilaterian sister-group. We suggest that this basal position of acoels and gnathostomulids is artifactal because for 1,000 replicate phylogenetic analyses with one random sequence as outgroup, the majority root with an acoel flatworm or gnathostomulid as the basal ingroup lineage. When these problematic taxa are eliminated from the matrix, the combined analysis suggests that the root lies between the deuterostomes and protostomes, and Ctenophora is the bilaterian sister-group. We suggest that because chaetognaths and lophophorates, taxa traditionally allied with deuterostomes, occupy basal positions within their respective protostomian clades, deuterostomy most likely represents a suite of characters plesiomorphic for bilaterians.
Abstract Annelids and arthropods have long been considered to be each other&a... more Abstract Annelids and arthropods have long been considered to be each other's closest relatives, as evidenced by similarities in their segmented body plans. In the first cladistic analysis of metazoan morphology accompanied by an explicit data matrix, Schram (Meglitsch and Schram, 1991, Invertebrate zoology, 3rd edition, Oxford Univ. Press, New York) suggested tentative support for this conventional “Articulata” hypothesis. Our reanalysis of the Schram data matrix yielded weak support for an alternative “Eutrochozoa ...
Abstract: About,36 species of chitons possibly,occur,at depths greater than 30 m along,the contin... more Abstract: About,36 species of chitons possibly,occur,at depths greater than 30 m along,the continental,shelf and slopeof the Southern California Bight (SCB), although littleis known about their distribution or ecology.Nineteen speciesare reported here based on chitons collected as part of long-term, local benthic monitoring programs orless frequent region-wide surveys of the entire SCB, and these show little overlap with species that occur
Biological Bulletin, 1988
... DIARMAID O FOIGHIL* AND DOUGLAS J. EERNISSE** ... as spermatophores/ spermatozeugmata (Coe, 1... more ... DIARMAID O FOIGHIL* AND DOUGLAS J. EERNISSE** ... as spermatophores/ spermatozeugmata (Coe, 1931; 0 Foighil, 1985b), dwarf/complemental males (Turner and Yakovlev, 1983; 0 Foighil, l985c), and pseudocopulation (Townsley et al., 1965). ...
Evolution: Education and Outreach, 2008
For over 100 years, molluscan eyes have been used as an example of convergent evolution and, more... more For over 100 years, molluscan eyes have been used as an example of convergent evolution and, more recently, as a textbook example of stepwise evolution of a complex lens eye via natural selection. Yet, little is known about the underlying mechanisms that create the eye and generate different morphologies. Assessing molluscan eye diversity and understanding how this diversity came about will be important to developing meaningful interpretations of evolutionary processes. This paper provides an introduction to the myriad of eye types found in molluscs, focusing on some of the more unusual structures. We discuss how molluscan eyes can be applied to the study of evolution by examining patterns of convergent and parallel evolution and provide several examples, including the putative convergence of the camera-type eyes of cephalopods and vertebrates.
Incorporating substantial intraspecific genetic variation for 19 species from 131 individual chit... more Incorporating substantial intraspecific genetic variation for 19 species from 131 individual chitons, genus Mopalia (Mollusca: Polyplacophora), we present rigorous DNA barcodes for this genus as per the currently accepted approaches to DNA barcoding. We also have performed a second kind of analysis that does not rely on blast or the distance-based neighbour-joining approach as currently resides on the Barcode of Life Data Systems website. Our character-based approach, called characteristic attribute organization system, returns fast, accurate, character-based diagnostics and can unambiguously distinguish between even closely related species based on these diagnostics. Using statistical subsampling approaches with our original data matrix, we show that the method outperforms blast and is equally effective as the neighbour-joining approach. Our approach differs from the neighbour-joining approach in that the end-product is a list of diagnostic nucleotide positions that can be used in descriptions of species. In addition, the diagnostics obtained from this character-based approach can be used to design oligonucleotides for detection arrays, polymerase chain reaction drop off diagnostics, TaqMan assays, and design of primers for generating short fragments that encompass regions containing diagnostics in the cytochrome oxidase I gene.
Systematic Biology, 1992
Abstract Annelids and arthropods have long been considered to be each other&a... more Abstract Annelids and arthropods have long been considered to be each other's closest relatives, as evidenced by similarities in their segmented body plans. In the first cladistic analysis of metazoan morphology accompanied by an explicit data matrix, Schram (Meglitsch and Schram, 1991, Invertebrate zoology, 3rd edition, Oxford Univ. Press, New York) suggested tentative support for this conventional “Articulata” hypothesis. Our reanalysis of the Schram data matrix yielded weak support for an alternative “Eutrochozoa ...
Journal of Paleontology, 2009
Journal of Molluscan Studies, 1987
Invertebrate Systematics, 2008
The chiton genus Mopalia Gray, 1847 is highly speciose despite showing little morphological diffe... more The chiton genus Mopalia Gray, 1847 is highly speciose despite showing little morphological differentiation. Many of the 24 extant species are conspicuous, large-bodied and ecologically important today, but pre-Pleistocene fossils for the genus are rare. Here, we use a combined analysis of four gene regions (16S and COI mtDNA, 18S and 28S rDNA) to estimate the phylogenetic relationships for Mopalia species and use the inferred phylogeny to analyse the group's biogeography and patterns of speciation. We then use these molecular data to distinguish between two alternative interpretations of the fossil record, as there is a large temporal gap between the oldest fossils tentatively identified as Mopalia and the next oldest fossils (Miocene versus Plio-Pleistocene). Based on the estimated substitution rates from a wide variety of other marine animals, we conclude that the observed rates in Mopalia are consistent with a Miocene origin for the genus. Given this age for the group and assuming a molecular clock, most speciation events in Mopalia are inferred to have occurred on average ~5 Mya. The phylogenetic results indicate that most of the speciation events leading to extant species must have occurred along the western North American coast, though there appear to have been multiple spreading events across the Pacific. When considered along with results for the many other near-shore taxa that have similar distributions to Mopalia, our findings suggest the emergence of a coherent historical biogeography of the northern Pacific.
Integrative and Comparative Biology, 1994
SYNOPSIS. There is interest in assembling a robust hypothesis of animal relationships based on mo... more SYNOPSIS. There is interest in assembling a robust hypothesis of animal relationships based on molecular and other character-based evidence, but even if a high degree of phylogenetic resolution is available, there remain challenging problems for postulating ancestral larval traits. This distinction between hypotheses of genealogies and our knowledge of specific traits is illustrated with specific examples of the portion of variable larval traits that are homoplastic (i.e., they require convergences, parallelisms, or character reversals) with respect to specific molecular-based genealogical hypotheses. Corresponding molecular studies suggest (1) maximal incongruity in larval form and metamorphosis for extant echinoderm classes, (2) convergences in larval size and form associated with coloniality in ascidians, (3) multiple losses of the locomotory larval tail in molgulid ascidians, (4) multiple losses of larval feeding and gain of apomictic parthenogenesis within a genus of bivalves, (5) multiple losses of larval feeding in echinoids, (6) alternative explanations of the distribution of feeding and non-feeding larvae among gastropods, and (7) recent modifications in embryonic and larval development of echinoids following prolonged stasis. These examples show that inferences from phylogenetic studies will ultimately be limited by the extent to which homoplasy and polarity can be unambiguously assessed for larval traits. These limitations are illustrated by alternative hypotheses for larval trait synapomorphies among phyla, evolution of feeding with opposed prototrochal and metatrochal ciliary bands, and the retention or reacquisition of the locomotory nauplius of the Euphausiacea and Dendrobranchiata. Inferences on the evolution of larval traits require other sorts of evidence, perhaps including information on the evolution of genes that play important roles in morphogenesis and their sites of expression.
Integrative and Comparative Biology, 1986
SYNOPSIS. Gametogenesis and gonadal growth in the west coast sea star Pisaster ochraceus normally... more SYNOPSIS. Gametogenesis and gonadal growth in the west coast sea star Pisaster ochraceus normally begins in the fall and leads to large gonads full of gametes in the spring, when spawning occurs. The timing of gametogenesis can be shifted simply by maintaining the animals on a seasonally changing photoperiodic regime out of phase with ambient. When they are kept on a spring-summer photoperiodic regime during the fall and winter, gametogenesis proceeds 6 mo ahead of schedule in the following spring and summer. Gametogenesis can be shifted out of phase even when the eyespots are removed. Short daylengths that normally occur during the fall and winter are not required for gametogenesis to proceed, nor are even the long daylengths of spring and summer that precede the initiation of gametogenesis in the fall. The temporal program is insensitive to fixed daylengths (LD 15:9, 13:11, 12:12, 9:15) and appears to involve an endogenous calendar.
American Malacological Bulletin, 2008
The aesthete canals of fourteen chiton species were cast with epoxy, allowing detailed examinatio... more The aesthete canals of fourteen chiton species were cast with epoxy, allowing detailed examination and comparison of the entire canal system that infiltrates their valves (shell plates). Some species in this study have been classified without question in the family Mopaliidae (Mopalia ciliata (Sowerby, 1840), Mopalia lignosa (Gould, 1846), Mopalia spectabilis Cowan and Cowan, 1977, Mopalia swanii Carpenter, 1864, Katharina tunicata (Wood, 1815), while other species have been placed in that family by some workers but not others (one has never been placed in the Mopaliidae (Tonicia chilensis (Frembly, 1827)). The results provide additional evidence that there is high diversity in aesthete canal morphology but also some striking resemblances interpreted here as homologies, reaffirming that aesthete canal characters have considerable potential for phylogenetic analyses and for supporting classification ranks ranging from suborder to species. In this case, the results are broadly consistent with traditional classifications of mopaliids, but Tonicella and Dendrochiton (taxa not always thought not to be mopaliids) share many aesthete canal synapomorphies with undisputed mopaliids, whereas Plaxiphora (typically thought to be a mopaliid) has an aesthete canal system more similar to non-mopaliid members of the Acanthochitonina. These differences are in line with results of recent phylogenetic analyses of the Mopaliidae.
American Malacological Bulletin, 2008
The chiton fossil record is richer than previously reported in the literature. A newly compiled d... more The chiton fossil record is richer than previously reported in the literature. A newly compiled database comprised of Cambrian to Pleistocene fossil chitons totals 2594 occurrences of 900 species. Of the 900, 430 are named species known only as fossils, 123 are extant species that also have a fossil record, and 247 are indeterminate taxa. Most of the database (61%) consists of fossil chiton occurrences reported from localities other than type localities. A preliminary analysis of the data using the collector curve method suggests that the chiton fossil record has not been adequately sampled by geographic regions or geologic time. The fossil record of chitons is incomplete, sporadic, and geographically limited because the sampling record has been incomplete, sporadic, and geographically limited. The current database comprises enough information to discern diversity patterns throughout geologic time, but whether the patterns are real or artifacts of sampling inadequacy remains to be investigated.
Organisms Diversity & Evolution, 2003
This study represents the first phylogenetic analysis of the molluscan class Polyplacophora using... more This study represents the first phylogenetic analysis of the molluscan class Polyplacophora using DNA sequence data. We employed DNA from a nuclear protein-coding gene (histone H3), two nuclear ribosomal genes (18S rRNA and the D3 expansion fragment of 28S rRNA), one mitochondrial protein-coding gene (cytochrome c oxidase subunit I), and one mitochondrial ribosomal gene (16S rRNA). A series of analyses were performed on independent and combined data sets. All these analyses were executed using direct optimization with parsimony as the optimality criterion, and analyses were repeated for nine combinations of parameters affecting indel and transversion/transition cost ratios. Maximum likelihood was also explored for the combined molecular data set, also using the direct optimization method, with a model equivalent to GTR + I + Γ that accommodates gaps. The results of all nine parameter sets for the combined parsimony analysis of all molecular data (as well as ribosomal data) and the maximum-likelihood analysis of all molecular data support monophyly of Polyplacophora. The resulting topologies mostly agree with a division of Polyplacophora into two major lineages: Lepidopleuridae and Chitonida (sensu Sirenko 1993). In our analyses the genus Callochiton is positioned as the sister group to Lepidopleuridae, and not as sister group to the remaining Chitonida (sensu Buckland-Nicks & Hodgson 2000), nor as the sister group to the remaining Chitonina (sensu Buckland-Nicks 1995). Chitonida (excluding Callochiton) is monophyletic, but conventional subgroupings of Chitonida are not supported. Acanthochitonina (sensu Sirenko 1993) is paraphyletic, or alternatively monophyletic, and is split into two clades, both with abanal gills only and cupules in the egg hull, but one has simple cupules whereas the other has more strongly hexagonal cupules. Sister to the Acanthochitonina clades is Chitonina, including taxa with adanal gills and a spiny egg hull. Schizochiton, the only genus with adanal gills that has an egg hull with cupules, is the sister-taxon to one of the Acanthochitonina clades plus Chitonina, or alternatively basal to Chitonina. Support values for either position are low, leaving this relationship unsettled. Our results refute several aspects of conventional classifications of chitons that are based primarily on shell characters, reinforcing the idea that chiton classification should be revised using additional characters.
Journal of Shellfish Research, 2009
The western North American bivalve mollusc known as the Olympia oyster, long known as Ostrea luri... more The western North American bivalve mollusc known as the Olympia oyster, long known as Ostrea lurida Carpenter 1864 †, is a historically exploited native species that has been largely displaced by larger nonnative oysters. There is much renewed interest in documenting and restoring its native populations and recent successful culturing has attracted a specialty market for these oysters. Yet its name was called into question when it was synonymized with O. conchaphila Carpenter 1857, an oyster whose type locality is Mazatla´n, Sinaloa, Mexico. Others have considered it more plausible that the Olympia oyster is a more northern species, distinct from O. conchaphila, but morphological or molecular evidence either way has been lacking. Here we used a molecular approach to test the single versus two-species hypotheses with samples from Sinaloa, Mexico, near the type locality of O. conchaphila (Mazatla´n, Mexico), and samples from Willapa Bay, WA, the type locality of O. lurida, as well as samples from intermediate locations. Based on our combined and separate analyses of two mitochondrial DNA (mtDNA) markers, 16S ribosomal RNA (16S) and cytochrome oxidase III (CO3), native Ostrea from Sinaloa, Mexico are reciprocally monophyletic with a clade from multiple other localities between Baja California, Mexico and British Columbia, Canada, including Willapa Bay, WA. Corrected pairwise sequence comparisons for 16S indicate these two groups last shared a common ancestor 1.5-3.9 mya (2.06% sequence divergence). Based on these results and assuming that the Sinaloa group represents the true O. conchaphila, molecular evidence supports O. conchaphila and O. lurida as separate species. Posthoc morphological comparisons uncovered no significant support for morphological distinction between the two taxa, underscoring the difficulty associated with using morphology alone to distinguish closely related oyster species. Despite the present lack of any morphological diagnostic differences for separating these nominal species, the molecular data are not consistent with the synonymy of the species and support the reinstatement of O. lurida from all the localities north of central Baja California.
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Papers by Douglas Eernisse