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    V: ASIH Stoye Award, Ichthyology IV

    2021-07-22   09:15 - 10:15

    Moderator: Eric Hilton

    1.  09:15  VIRTUAL    An environmental DNA (eDNA) assessment of fish assemblages on artificial reefs in the northern Gulf of Mexico. Aaron Krolow*, Southeastern Louisiana University; Aaron Geheber, University of Central Missouri; Kyle Piller, Southeastern Louisiana University

    Globally, estuarine and marine fisheries have declined over the past century and a variety of approaches have been employed in an attempt to improve fisheries including the development of protected areas, implementation of catch regulations, hatchery stocking, and habitat augmentation. The focus of this study was to assess the impact of the introduction of artificial reefs on the fish assemblages in the northern Gulf of Mexico (nGOM). Unfortunately, assessing the success of artificial reefs has been problematic due to the high turbidity of the region and the difficulty of using traditional sampling gears to assess species diversity at reefs. To accomplish this, we gathered environmental DNA (eDNA) metabarcode data (12S) to assess the impact of reef age (1-19 yrs), construction material (limestone, concrete, shell, and oil & gas), and season on the fish assemblages at nine artificial reefs in the nGOM. The results indicate higher species richness at reefs versus paired control sites; as well as differences between seasons, reef materials, and reef position. These results suggest that this technique is a viable method that can be used to monitor ray-finned fish species on artificial reefs and can provide baseline information on the fish assemblages associated with artificial reefs in the nGOM.

    2.  09:30  VIRTUAL    Complex Riverscape Processes in Cichlids from the Lower Congo River. Naoko P. Kurata*, City University of New York; Elizabeth Alter, California State University - Monterey Bay; Melanie Stiassny, American Museum of Natural History; Michael Hickerson, City University of New York

    The lower Congo River (LCR) consists of a dynamic hydroscape exhibiting extraordinary aquatic biodiversity, endemicity, and ecological specialization. Previous studies have suggested that numerous rapids throughout the LCR form physical barriers to gene flow, thus facilitating speciation, thereby shaping the diversity of ichthyofauna. However, this theory has not yet been fully explored for species distributed across the LCR. In this study, we examined four species of lamprologine cichlids endemic to the LCR, of which three are sequentially distributed along the LCR without range overlap. The fourth species is blind and likely lives at deep depths. Using genome-wide SNP data, we tested the hypothesis that rapids serve as physical barriers to gene flow that generate genetic divergence at the species and population levels and that gene flow directionality follows the river flow. Morphological adaptation to rapid-water was also examined using CT scanning methods. Our results suggest that the riverscape processes of the cichlids are more complex than the simple riverscape model suggested. We identified the populations of the most widely distributed species, lamprologus tigripictilisare highly connected through multidirectional gene flow. Furthermore, our results are consistent with the prediction that the rapids correspond to differences in gene flow. We detected some early-stage morphological divergence possibly related to the adaption to fast-water environments. However, we found that rather than always serving as barriers, high-energy rapids may provide occasional dispersal opportunities for riverine cichlids. These results suggest that the complex evolutionary processes in the riverscape may be generating the hyper-diverse fish assemblies.

    3.  09:45  VIRTUAL    (A Lack of) Patterns of Phenotypic Evolution Associated with Marine/Freshwater Transitions in Fishes. Victor de Brito*, Western Michigan University; Ricardo Betancur-R., University of Oklahoma; Michael Burns, Cornell University Museum of Vertebrates; Thaddaeus Buser, Rice University; Kevin Conway, Texas A&M University; João Paulo Fontenelle, University of Toronto Scarborough; Matthew Kolmann, University of Michigan; Tyler McCraney, University of California; Christine Thacker, Natural History Museum of Los Angeles County; Devin Bloom, Western Michigan University

    Evolutionary transitions between marine and freshwater ecosystems have occurred repeatedly in fishes. The theory of ecological opportunity posits that dispersal to new habitats can lead to increase in phenotypic diversity. If dispersal to new habitats influences phenotypic evolution then transitions between marine/freshwater transitions may be predicted to drive shifts in body size evolution. In this study, we tested if transitions between marine and freshwaters are directly associated with an increase or decrease in body size. We used phylogenetic comparative methods to analyze body size evolution in trans-marine/freshwater clades, including ariid catfishes, silversides, gobies, pufferfishes, anchovies, sculpins, stingrays, needlefishes, and clingfishes. Our results show no difference in body size between marine and freshwater fishes, and no directionality in size variation following marine/freshwater transitions. We demonstrated that size disparity of freshwater species in a clade is associated with the number of closely related lineages that invaded freshwaters, but not speciation following the transition event. Shifts in size evolution estimated by simulations without a priori assignment of habitat data were not congruent with habitat transitions, suggesting that other factors may be more important in body size evolution. Our study shows that transitions between marine and freshwater environments do not always drive changes in patterns of phenotypical evolution across a wide range of globally distributed fishes.

    4.  10:00  VIRTUAL    Genome-wide Markers and 3D Geometric Morphometrics Reveal Hidden Structure in the Congolese Carp Species Labeo sorex Nichols & Griscom (1917). Tobit Liyandja*, Richard Guilder Graduate School, American Museum of Natural History; Elizabeth Alter, California State University; Yves Mabeki, University of Kinshasa; Melanie Stiassny, Richard Guilder Graduate School, American Museum of Natural History

    Labeo sorexis a carp species endemic to the Congo River (CR) where it mainly occurs in rapids habitats. The species ischaracterized as rheophilicbased on its morphological characteristics. Previous studies have associated L. sorexdistribution with rapids and rocky habitats, which are discontiguous habitats along the CR. We used an integrative approach, including 3D morphological analysis, ecological niche modeling (ENM), and reduced-representation genome sequencing (RADseq) to investigate population structure, demographic history, phenotypic variation, and habitat suitability of L. sorex along the CR.Twenty-four tissue samples have been obtained from 10 localities throughout the species range.Analysis of 15,761 loci suggests the existence of two reciprocally monophyletic populations (lower-middle Congo population, and the upper Congo population) of L. sorex along the CR with moderate gene flow (average Fst=0.11 p-value <0.00001). Demographic model selection suggests that the structure of these populations was best explained by divergence with bidirectional migration. We found that the upstream population has a considerably smaller (4.4 times less) effective population size than the downstream population and that most migration events were into the upstream population. Principal component analysis of the kinethmoid shape suggests a significant difference between the two populations. ENM rejects the hypothesis of disjunct distribution and supports an extensive distribution of L. sorexalong the CR.Our results are an important step for delimiting Labeo species and understanding the drivers of carp diversification in the CR. Finally, revising the taxonomy of Labeo is critical for the development of sound strategies for fish resource management for these important food items in the region.

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