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    ASIH Stoye Award, Ichthyology I

    2021-07-21   09:15 - 10:15

    Moderator: Bill Ludt

    1.  09:15  IN-PERSON    Role of Paleoclimatic Events on the Evolution of Body Size in Tetraodontiform Fishes. Emily Troyer*, University of Oklahoma; Ricardo Betancur-R, University of Oklahoma; Dahiana Arcila, University of Oklahoma

    Body size is an important species trait, correlating with lifespan, fecundity, and other ecological factors. Over Earth’s geological history, climate shifts have occurred, potentially shaping body size evolution in many clades. General rules attempting to summarize the evolution of body size include Bergmann’s rule, which states that species grow to larger sizes in cooler environments and smaller sizes in warmer environments, and Cope’s rule, which poses that lineages tend to increase in size over evolutionary time. Tetraodontiform fishes (pufferfishes, boxfishes, ocean sunfishes) provide an excellent model clade to test these rules owing to their exemplary fossil record. We tested Bergmann’s and Cope’s rules in this group by combining phylogenomic data (1,103 exon loci from 187 extant species) with 210 anatomical characters coded from both fossil (52) and extant (17) species, and by aggregating data layers on paleoclimate and body size obtained from the species examined. We inferred a set of time-calibrated phylogenies using tip-dating approaches and used these trees to examine patterns of body size evolution in a model-fitting framework. Our analyses provide strong support for a temperature-driven model, in which increasing body size over time is correlated with decreasing oceanic temperatures. On average, extant tetraodontiform species are 2 to 3 times larger than their fossil counterparts, which otherwise evolved during periods of warmer ocean temperatures. These results provide strong support for both Bergmann’s and Cope’s rules, trends that are much less studied in marine fishes compared to terrestrial vertebrates and marine invertebrates.

    2.  09:30  IN-PERSON    The Bold and the Brilliant: Resolving Taxonomic Issues Between the Bold Characodon (Characodon audax) and the Rainbow Characodon (C. lateralis). Andrew Sherman*, Southeastern Louisiana University; Kyle Piller, Southeastern Louisiana University

    The Mesa Central of Mexico formed as a result of tectonic and volcanic activity and is considered to be a hot spot of freshwater fish biodiversity. This region is a double-edged sword, where the isolated nature of the Mesa Central that allowed for rapid speciation has made many of these species vulnerable to extinction. The genus Characodon (Goodeidae) is one such group on the decline due to a mix of restricted range, changes and loss in habitat and other anthropogenic interference. This group is also plagued by a turbulent taxonomic history and the inability to properly define the species boundaries between its two extant species, Charcodon lateralis and C. audax. The goal of this study was to use genomic techniques to analyze populations across the range of Characodon in both a phylogenetic and population genetic framework to delineate the species boundaries within this group. Our results show there are four distinct lineages across the populations sampled in this study, and that a geographic feature, the El Salto waterfall, acts as a major genetic barrier. Insights from this study will help inform conservation and management efforts aimed at preserving extant populations of this genus.

    3.  09:45  IN-PERSON    Resolving taxonomic difficulties between Poeciliopsis pleurospilus and Poeciliopsis gracilis (Cyprinodontiformes: Poeciliidae). Sarah J. Ward*, The University of Oklahoma; Caleb D. McMahan, Field Museum of Natural History; Kyle R. Piller, Southeastern Louisiana University

    Middle America is a biologically and geologically interesting region. The family Poeciliidae is widespread throughout Middle America and is host to a variety of novel adaptations, making it an interesting group to study from a diversification perspective. Poeciliopsis is a genus of poeciliids that dominates the freshwater fish biomass in parts of Middle America. Two widely distributed species, Poeciliopsis pleurospilus (primarily distributed in Pacific Coast drainages) and Poeciliopsis gracilis(Atlantic Coast drainages), are morphologically similar to one another, with the species primarily being differentiated based on pigmentation patterns. As a result of variation in pigmentation patterns, species boundaries for these species are unclear. This has caused some researchers to suggest that P. pleurospilus and P. gracilis should be synonymized. However, no targeted study has examined the distinctiveness of these species. Therefore, the goal of this study was to examine the monophyly of P. pleurospilus and P. gracilis using ddRAD data from populations of these species from El Salvador, Guatemala, Honduras, and Mexico and to assess genetic variation using both ddRAD and mitochondrial data. Together, the results from this study will provide resolution to long-standing taxonomic issue of these two congeners.

    4.  10:00  VIRTUAL    A new species of Chromis damselfish from the tropical western Atlantic (Teleostei, Pomacentridae). Emily McFarland*, San Francisco State University; Carole Baldwin, Smithsonian Institution; Ross Robertson, Smithsonian Tropical Research Institute; Luiz Rocha, California Academy of Sciences; Luke Tornabene, University of Washington

    Initially described in 1882,Chromis enchrysurus, the Yellowtail Reeffish, was redescribed in 1982 to account for an observed color morph that possesses a white tail instead of a yellow one, but morphological and geographic boundaries between the two color morphs were not well understood. Taking advantage of newly collected material from submersible studies of deep reefs and photographs from rebreather dives, this study sought to determine whether the white-tailedChromisis actually a color morph ofChromis enchrysurusor a distinct species. Phylogenetic analyses of mitochondrial genes cytochrome b and cytochrome c oxidase subunit I separatedChromis enchrysurusand the white-tailedChromisinto two reciprocally monophyletic clades. A principal component analysis based on 27 morphological characters separated the two groups into clusters that correspond with caudal-fincoloration, which was either known or presumed based on the specimen’s collection site according to biogeographic data on species boundaries in the Greater Caribbean. Genetic, morphological, and biogeographic data all indicate that the white-tailedChromisis a distinct species, herein described asChromis vanbebberaesp. nov.The discovery of a new species within a conspicuous group such as damselfishes in a well-studied region of the world highlights the importance of deep-reef exploration in documenting undiscovered biodiversity.

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