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    V: Reptile Genetics and Morphology

    2021-07-27   13:30 - 15:30

    Moderator: Steven Jasinski

    1.  13:30  VIRTUAL    Parceling out the brain: allometry and encephalization deconstructed. Daniel Hoops*, The Hospital For Sick Children; John Sled, The Hospital For Sick Children

    Brain allometry is a measure of how closely changes in body size are paralleled by changes in brain size, while the encephalization quotient estimates how “enlarged” a brain is relative to what’s predicted for a given body size. Both measures are traditionally applied to the brain overall, and interesting trends have been found using these measures to compare brain evolution within and across vertebrate groups, as well as across individuals within species. However, rarely are the relative contributions of different neural structures to overall variation in brain volume considered in this context. Since the brain is anatomically and functionally heterogeneous, regional differences in brain evolution have profound effects on the behavioural and cognitive implications of allometric and encephalic scaling. Here, we take advantage of a novel data set of almost 300 magnetic resonance images of agamid lizard brains to parcellate the brain into over 9000 voxels (3D pixels) in order to determine what variation exists in allometric scaling across species (referred to as evolutionary allometry) and within species (referred to as static allometry). We also examine encephalization across the fourteen agamid species included in the data set and determine which brain regions contribute the most, and the least, to encephalization across species. Finally, we discuss the potential behavioural and cognitive implications of our findings, and examine what other factors, such as sex and habitat, may help explain variation in brain structure across and within species.

    2.  13:45  VIRTUAL    Systematics and Evolution of Boas in the West Indies. Graham Reynolds*, University of North Carolina Asheville

    West Indian boid snakes in the genus Chilabothrus comprise an exclusively insular monophyletic lineage dating to the Miocene. These nocturnal boas occupy habitats ranging from xeric scrub to montane rainforest and have maximum adult body sizes spanning a range from<1 m to nearly 4 m. As recently as 2013, only nine species were recognized, though substantial work in the last few years has increased the number of known species by 36%. This includes the recognition of cryptic species such as the Virgin Islands Boa, the re-discovery of the Crooked-Acklins Boa, and the dramatic discovery of the Silver Boa, a new species found in 2015. The last decade has also seen a substantial amount of progress in our understanding of the biology West Indian Boas. Two morphotypes have been recognized based on ecological, morphometric, and meristic analyses: large-bodied generalists and small-bodied specialists. Both large and small species are distributed across the West Indies, though no single island has more than one large species, and small species frequently co-occur with large species (with the exception of the Bahamas banks). Further, this determinism in body size and ecological evolution has been arrived at via different evolutionary pathways, notably, via accelerated rates of head shape (trophic morphology) evolution as small-bodied species evolved from larger ancestors. I will discuss our current understanding of the ecology and evolution of these boas, including the application of multivariate morphological analysis, statistical historical biogeography, molecular phylogenomics, and phylogenetic comparative methods that have greatly increased our understanding of these lineages.

    3.  14:00  VIRTUAL    Clutch Predicts Growth of Hatchling Burmese Pythons Better Than Food Availability or Sex. Jillian Josimovich*, U.S. Geological Survey, Fort Collins Science Center - South Florida Field Station in Everglades National Park; Bryan Falk, U.S. Geological Survey, Fort Collins Science Center - South Florida Field Station in Everglades National Park; Alejandro Grajal-Puche, U.S. Geological Survey, Fort Collins Science Center - South Florida Field Station in Everglades National Park; Emma Hanslowe, U.S. Geological Survey, Fort Collins Science Center - South Florida Field Station in Everglades National Park; Ian Bartoszek, Conservancy of Southwest Florida; Robert N. Reed, U.S. Geological Survey, Fort Collins Science Center; Andrea Currylow, U.S. Geological Survey, Fort Collins Science Center - South Florida Field Station in Everglades National Park

    Identifying environmental and genetic factors affecting growth pattern phenotypes helps biologists predict how organisms distribute finite energy resources in response to varying environmental conditions and physiological states. This information may be useful for monitoring and managing populations of cryptic, endangered, and invasive species. Consequently, we assessed the effects of food availability, clutch, and sex on the growth of invasive Burmese pythons (Python bivittatusKuhl) from the Greater Everglades Ecosystem in Florida, USA. Though little is known from the wild, Burmese pythons have been physiological model organisms for decades, with most experimental research sourcing individuals from the pet trade. Here, we used 60 hatchling pythons collected as eggs from the nests of two wild pythons, assigned them to High or Low feeding treatments, and monitored growth and meal consumption for 12 weeks. Surprisingly, clutch was a better predictor of variation in python growth and size than feeding treatment or sex. Hatchlings from one clutch grew faster and were longer, heavier, in better body condition, and ate more frequently, regardless of food availability. Further, we compared the captive-raised hatchlings to 34 additional wild-caught hatchlings that were opportunistically removed from the same invasive population. Wild counterparts exhibited more positive body conditions which suggests that the metabolic costs associated with digestion may vary according to the timing and tempo of feeding opportunities. Additional research is warranted to identify the underlying mechanisms and fitness implications of this variation to help inform risk assessments and management.

    4.  14:15  VIRTUAL    Learning to Swim: Multiple Transitions from Terrestrial to Aquatic Life in Elapids. Justin Jacobs*, Biology Department, The University of Texas at Arlington; James Titus-McQuillan, Department of Bioinformatics and Genomics, University of North Carolina at Charlotte; Alexander Hall, Thermo Fisher Scientific

    Without limbs for grasping, climbing, or locomotion, snakes must use only bones and associated musculature of their skull and spine to successfully survive and thrive in their environment. Among snakes, those in aquatic environments differ in substantive ways from terrestrial snakes: more teeth, flatter skulls, flattened tails, etc. We investigated the transition from terrestrial to aquatic life in four elapid clades, coralsnakes in the genus Micrurus, cobras in the genus Naja, kraits in the genera Laticauda and Bungurus, and elapids of the Australian radiation in subfamily Hydrophiinae. Using a phylogenetically-aware analysis of morphology, we used high resolution computed tomography (CT) to study skull and vertebral morphology. We document character evolution in this ecological transition and analyzed these data using three-dimensional geometric morphometrics. Through these comparisons across the large and diverse family, we reconstruct the evolution of Elapid morphology and, by extension—ecology, over transitions to aquatic life.

    5.  14:30  VIRTUAL    The Color of Conservation: Analyzing Color Polymorphism in the Giant Gartersnake. Anna Jordan

    Reptiles exhibit wide varieties of color patterns that vary within species. However, little is known about how such color polymorphisms are associated with reptiles in fragmented and heavily modified habitats.The demographics of the federally threatened giant gartersnake (Thamnophis gigas) have been extensively studied, but while color polymorphism in giant gartersnakes has been anecdotally observed it has never been formally quantified. Color polymorphism in other water snake species has been linked to both increased fitness advantages and increased predation risk. To determine whether different giant gartersnake subpopulations exhibit different color polymorphisms, we examined how levels of melanin varied throughout 5 water basins in their range. Using standardized photographs, we quantified the degree of melanism in 600 giant gartersnakes by scoring the percentage of black on individual scales on a semi-discrete scale. Lower melanin scores corresponded with lighter overall coloration. Using ANOVA, we found snakes within the water basin with the highest proportion of wetland habitat exhibited significantly lower melanin scores relative to snakes occupying basins dominated by irrigation canals. Our results indicate levels of color polymorphisms vary among giant gartersnake subpopulations. Furthermore, interactions between habitat and coloration may ultimately affect reproductive success or survival in this species of conservation concern.

    6.  14:45  VIRTUAL    Independent loss of cloacal bursae and age-dependent surfacing postures diamond-backed terrapins (Chelonia: Emydidae: Malaclemys terrapin). Jadyn Sethna*, Georgia Institute of Technology; Ollie Shinn, Georgia Institute of Technology; Megan Wright, Georgia Institute of Technology; Joseph Mendelson, Zoo Atlanta

    Malaclemys terrapin is a species of turtle that lives in brackish waters along the eastern coast of the United States from Cape Cod to Texas. We documented distinctive underwater postures during surfacing in hatchling versus yearling individuals. Hatchlings approach the water’s surface in horizontal postures, while yearlings approach in a more vertical posture. Because cloacal bursae play a role in controlling buoyancy in freshwater turtles, we investigated their potential role in determining surface postures. We discovered that cloacal bursae are absent in M. terrapin, but present in their close relatives that we examined, Trachemysand Graptemys. We attribute this absence to the brackish habitats of this species. We posit that horizontal postures in the hatchlings create a broader visual target to both aerial and aquatic predators and that the younger turtles likely do not have the strength, muscle or lung-volume coordination, or sufficient bone density to adopt the more visually streamlined vertical posture at the surface

    7.  15:00  VIRTUAL    Distinct Fossil Emydids (Testudines: Emydidae) from Eastern Tennessee and Their Potential Implications for the Evolution of the Emydidae. Steven Jasinski*, Harrisburg University of Science and Technology

    Emydid turtles (Testudines: Emydidae), the most diverse and widespread family of turtles in the New World today, consist of 10 to 12 extant genera and over 50 species. Although their fossil record shows high disparity, many of the fossil taxa have been fragmentary and/or synonymized or later considered nomina dubia. The Gray Fossil Site in northeastern Tennessee is a fossil locality from the latest Hemphillian-earliest Blancan and is interpreted as an ancient pond-like sinkhole. The site has at least 4 distinct fossil emydids among its turtle fauna, including representatives of Trachemys, Chrysemys, Terrapene, and Emydoidea/Emys. Based on phylogenetic analyses, these turtles show similarities with species from various geographic regions, suggesting a non-analog turtle fauna and adding to the distinctiveness of the site. Trachemys haugrudi from the site is most closely related to fossil species from Florida. The new species of Chrysemys is closely related to fossil Chrysemys from Nebraska. A new species of Terrapene is found to lie outside crown Terrapene, near the base of the Terrapene clade, while also being most closely related to species from the midwestern United States. The fourth, enigmatic emydid shows affinities with Emydoidea and Emys. It would represent the southern-most extent of Emydoidea, farther south than other fossil records and distinctly farther south than the modern biogeographic range, which extends to central Illinois and Indiana. The distinct turtle fauna at the Gray Fossil Site provides significant new information in understanding the evolution of the most diverse family of New World turtles today.

    8.  15:15  VIRTUAL    Repeatability in habitat use in spatially and temporally heterogeneous environments: an individual-based approach. Nathan Byer*, University of Nevada - Reno; Brendan Reid, Rutgers University

    Repeatability in habitat use – otherwise known as site fidelity – is widespread. In some cases, used habitat areas may also be inherited by offspring in a phenomenon called natal philopatry, allowing repeatability in habitat preferences to extend across generations. Site fidelity and philopatry may both represent strategies that can be used to optimize fitness in unpredictable environments. While turtles (Order Testudines) exhibit both fidelity and natal philopatry when selecting nesting areas, emerging evidence suggests that nest choice may be more plastic than previously thought. We constructed a spatially-explicit individual-based model (SEIBM) to explore factors that may produce deviations from nest site fidelity and philopatry, and parameterized this model with empirical behavioral and genetic data for the Blanding's Turtle (Emydoidea blandingii) in central Wisconsin. Our model recreated empirical deviations from nest site fidelity and philopatry, with reduced philopatry with increasing error rates in habitat discrimination and reduced site fidelity with decreasing risk tolerance. Unpredictable spatial distributions of risk increased natal philopatry for initial breeding events but decreased site fidelity overall, suggesting that strong natal imprinting may sometimes be associated with rapid shifts in habitat preferences in unpredictable environments. Associating risk exposure with increased adult or nest mortality led to increased nest site fidelity in both cases, but with relatively weak effects on natal philopatry. Our model is readily generalizable to other landscapes and species, and holds promise for more detailed exploration of the ecological and evolutionary factors that may give rise to fidelity and philopatry.

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