Session 39: Squamate Ecology (* last talk is morphology)Room: Room 206C2022-07-30 13:30 - 16:00 |
| Moderator: Roger Anderson |
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1. 13:30 Nanohabitat use, behaviors and body temperatures of the lizard, Sceloporus occidentalis along the cool coast of the Salish Sea. Roger Anderson*, Western Washington University drraanderson@gmail.com
Sceloporus occidentalis is a medium-to-small lizard that inhabits the interface of the coastal shore and forest edge in the maritime climate of northwest Washington state. Given that this lizard has a relatively short activity season of about 5 months along the Salish Sea, it was reasonable to ask whether it is active at relatively low body temperatures when compared to conspecifics and congeners in warmer locales, thereby possibly extending its daily and seasonal activity. The short answer is no, but the longer, detailed path to this answer reveals correlates of nanohabitat conditions (substratum temperatures, air temperatures, insolation level) and a variety of lizard behaviors that provide perspective on how this lizard can occupy such a wide diversity of locales and broad geographic range across latitude and altitudes. |
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2. 13:45 Demographics and Microhabitat Use of a Recently Established Population of Invasive Anolis sagrei in Southeastern Louisiana. Florence Wen*, Southeastern Louisiana University; Oliver Ljustina, Southeastern Louisiana University florence.wen@selu.edu
Anolis sagrei (Brown Anole) is a species of lizard native to Cuba and the Bahamas that has been widely established in the southeastern United States, including southeastern Louisiana. In 2018, we discovered the first established population of A. sagreiin Tangipahoa Parish, Louisiana, presenting us with a unique opportunity to study a nonnative species early in its introduction to a new locale. As this population is in the northern portion of their introduced range, they are subjected to cooler temperature regimes than they would experience in their native range. Since September 2018, we have monitored this population’s demographics and microhabitat use. We hypothesized lizards would experience decreased population size and decreased body condition in cooler seasons versus hotter seasons. We also hypothesized that lizards would be more likely to use artificial substrates (e.g. concrete) during cooler periods and more natural substrates (e.g. tree trunks) during hotter portions of the year. Our data suggest that population size decreases in winter and increases during the summer, likely due to high morality experienced during cool winter temperatures. This population begin their breeding season in the spring (May), with hatchlings emerging in the summer and into early fall. We did not find significant differences in body conditions of adult lizards between spring and summer. We did find significant, negative correlation with frequency of artificial substrate use relative to air temperature, with lizards being more likely to perch on artificial substrates during cooler temperatures. |
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3. 14:00 Demographic Fluctuation of Sky-island Populations of Sceloporus occidentalis on a Mojave Desert Sky Island: Collapse, Recovery, and Persistence. James Archie*, CSU Long Beach; Milinda Thompson, Cypress College james.archie49@gmail.com
Climatic fluctuations in the Mojave Desert of California including extended drought periods have resulted in demographic fluctuations in the western fence lizard (Sceloporus occidentalis) found on desert sky-islands. Over a 13 year period (2010-2022), we carried out a mark-recapture study of two lizard populations on Ord Mountain in the Mojave. The high elevation population (Upper Ord: 1850m) was up to four times more dense than the low elevation population (Lower Ord: 1450m), near the lower elevation limit of the species in the Mojave Desert. The number of adults captured on the 1ha grids fluctuated on Upper Ord by 215% (33 to 72; avg 43.8) but recovered following declines. The Lower Ord population showed a steady decline from 2013 to present (range: 33 to 10; avg 23.8). Both populations experienced demographic collapse during the 2012-13 and 2018-19 seasons due to the lack of juvenile recruitment. The frequency of first-year lizards dropped from highs of 45% (Upper) and 29% (Lower) of all lizards captured during most years down to 0% in 2013 and 4% (Lower) to 8% (Upper) in 2019. Inter-annual adult recapture frequency increased following the severest drought year (2012-2013). Summer monsoonal rains in 2013 and 2014 resulted in successful juvenile recruitment presumably due to increases in insect activity following late summer and fall blooms of plant life. In addition to the occurrence of Crotaphytus bicinctores at both sites, since 2017 Sceloporus uniformis adults and young have been found on the Lower Ord site increasing likely predation on S. occidentalis. |
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4. 14:15 Traits predict multidimensional resource use in an introduced lizard community of anoles and day geckos in Hawai'i. Amber Wright*, University of Hawaii at Manoa; Stevie Kennedy-Gold, University of Hawaii at Manoa; Carla Piantoni, University of Hawaii at Manoa; Emily Naylor, George Washington University; Robyn Screen, University of Hawaii at Manoa; Tyler Figueira, University of Hawaii at Manoa; Carlos Navas, University of Sao Paulo; Timothy Higham, University of California, Riverside anwright@hawaii.edu
Linking functional traits to resource use allows for mechanistic understanding of species interactions, increasing our ability to predict community dynamics. Greater Antillean Anolis lizards are a textbook example of adaptive radiation, and functional traits associated with resource partitioning of structural habitat, thermal habitat, and diet are well-established. Introductions of Anolis (green and brown anoles) and the ecologically convergent Phelsuma (gold dust day geckos) to Hawaiʻi provide an opportunity to test whether trait differences predict patterns of resource use that can explain dynamics in this novel community. We measured the following traits and resource use in enclosures under controlled resource availability: head morphology and diet stable isotopes, clinging ability and perch use, preferred temperature and field temperature. Lizards did not shift resource use due to species assemblage, and differences in thermal traits and use were subtle. However, structural habitat and diet were highly correlated. Over half of the variation in multidimensional resource use space was explained by an axis varying from smooth, high perches, high ????15N, and low ????13C at one extreme (day geckos), to low, rough perches, low ????15N, and high ????13C at the other (brown anoles). Green anoles used the entire spectrum, and as a result, they lack competitor-free resource space when co-occurring with both brown anoles and day geckos. This is consistent with the observation that green anoles have declined following the introduction and spread of the other two species on O'ahu. Our results also show that the Anolis trait-performance-ecology framework generalizes to a novel player. |
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5. 14:30 Beyond “Thermoregulation”: Microhabitat Use Impacts Both UV and Temperature Regulation Effectiveness in Tree Lizards. Matthew Lattanzio*, Christopher Newport University matthew.lattanzio@cnu.edu
Over a century of ecophysiological studies on reptiles have perpetuated the assumption that basking and shuttling behaviors function solely for temperature regulation. However, these behaviors also modulate exposure to ultraviolet (UV) light wavelengths that are essential for maintaining physiological homeostasis and ensuring proper growth and development. An alternative hypothesis is that lizards also actively regulate their UV exposure. In this scenario, microhabitat selection should influence both temperature and UV regulation effectiveness, potentially in contrasting ways. I test this hypothesis on tree lizards (Urosaurus ornatus), employing a classic thermoregulatory framework with operative, preferred, and body exposure values of both UV and temperature. Despite operative UV models revealing daily exposure to UV often exceeding 10 (UV Index), tree lizards preferred values between ~0.5-2.9 UVI. Temperature preferences and exposures matched prior studies; interestingly, operative temperature models revealed that U. ornatus could attain preferred temperatures in the shade, especially lizards using living trees over dead snags. However, use of living trees conferred a much stronger UV advantage: UV regulatory effectiveness of lizards in trees was almost double that for lizards using snags. Overall, my findings confirm active UV regulation in tree lizards, and suggest that microhabitat selection may have divergent impacts on the ability of a lizard to satisfy both its UV and thermal demands. Outside of zoos and hobbyists, appreciation of the importance of UV for reptile biology has been minimal. Addressing this deficit is vital to improve our understanding of the factors shaping the evolution of photoregulation behavior in nature. |
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6. 14:45 Evolutionary Opportunity and the Limits of Community Similarity in Replicate Radiations of Island Lizards. Luke Frishkoff*, University of Texas at Arlington; Gavia Lertzman-Lepofsky, University of Toronto; Luke Mahler, University of Toronto frishkol@gmail.com
Ecological community structure ultimately depends on the generation of community members through speciation. To understand how macroevolutionary processes shape communities, we surveyed Anolis lizard assemblages across elevations on Jamaica and Hispaniola, neighboring Caribbean islands similar in environment, but contrasting in the species richness of their evolutionarily independent faunas. The impact of diversification on local communities depends on available opportunities for speciation within or between ecologically distinct sub-regions. Where opportunities abound, as in the vast lowlands of both islands, communities converge in species richness and average morphology. But community structures diverge in the highlands. On Jamaica, where limited highland area restricted diversification, communities remain depauperate and consist largely of elevational generalists. In contrast, a unique fauna of high-elevation specialists evolved in the expansive Hispaniolan highlands, augmenting highland richness, and driving islandwide turnover in community composition. Accounting for disparate evolutionary opportunities may illuminate when regional diversity will enhance local diversity and help identify the causes of convergent versus divergent community structure. |
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7. 15:00 Diverse phenotypes facilitate niche partitioning in a sky island Sceloporus assemblage. Erin Westeen*, UC Berkeley; José Gabriel Martínez-Fonseca, Northern Arizona University; Ian Wang, UC Berkeley ewesteen@berkeley.edu
If closely-related species should be more similar and therefore more likely to compete for resources, why do we see so many examples of species-rich congeneric communities in nature? To avoid competition, many interacting species possess traits associated with resource use – or ecomorphologies – that allow them to access unique niche space. Ecomorphologically diverse communities can develop in-situ because of competition (adaptive radiations) or ex-situ the dispersal of phylogenetically conserved species into communities with previously unoccupied niche space (niche differentiation). Island systems, in which species interactions are at extremes due to limited resources, provide valuable insights to our understanding of how ecomorphological diversity contributes to coexistence. Spiny lizards (genus Sceloporus) comprise a species-rich, widespread and ecologically diverse lineage, in which many species live in sympatry. To understand how ecomorphological diversity evolves and influences resource use, studied Sceloporus lizards of the Chiricahua Mountains in southeastern Arizona. This ‘sky island’ community is composed of lizards from different clades, many of which are at their range edge. By quantifying structural, temporal, and thermal niche use of co-occurring species over three field seasons, we show that species diverge primarily in perch height and type. We also demonstrate interspecific divergence in ecologically-relevant phenotypic traits – including body size, scale size, hindlimb length, foot length, and dorsal and ventral coloration – and find that phenotype is a strong predictor of niche use. Studies of niche partitioning and ecomorphology, especially of closely-related species, deepen our understanding of how diverse communities assemble and how morphological diversity accumulates across the tree of life. |
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8. 15:15 Habitat Use and Movement Patterns of Northern Pine Snakes (Pituophis melanoleucus) in Coastal South Carolina. Alan Jones*, Coastal Carolina University; Tiffany Bogan, Coastal Carolina University; Andrew Grosse, SC DNR; Scott Parker, Coastal Carolina University ajones4248@gmail.com
Pine Snakes (Pituophis melanoleucus) are of conservation concern over much of their geographic range due to habitat loss, fire suppression, and targeted removal by collectors. Across their geographic range, only a few studies have examined spatial ecology and habitat use of Pine Snakes, and no studies have been conducted in South Carolina. The purpose of this study is to determine Pine Snake movement patterns, home range size and habitat use with the long-term goal of assisting conservation management. We used a combination of radio telemetry and trail cameras to quantify movement patterns and daily use of four male and four female Northern Pine Snakes (NPS) from a population on the Coastal Plain of South Carolina from April 2021 – July 2022. Preliminary data indicate that during the summer, male NPS occupied an area of about 13.8 ha vs 12.1 ha for females. Maximum single day distance moved was 594 m. Snakes spent most of their time in open canopy habitat but also used patches of dense vegetation. Average canopy cover at snake locations determined by radio telemetry was 35% compared to 31% at random sites. Average ground cover at snake locations was 31%, compared to 62% at random sites. Pine Snakes preferentially used root cavities of fallen trees or burned-out stumps as refugia and secondarily, abandoned rodent burrow systems. Eastern Coachwhips (Masticophis flagellum) were frequently observed sharing refugia with NPS. Our results suggest that NPS exist in discrete meta-populations in SC, with males traveling between population subunits during the reproductive season. |
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9. 15:30 Resistance against rattlesnake venoms in a Great Plains rodent community. Neil Balchan*, University of Northern Colorado; Stephen Mackessy, University of Northern Colorado neilbalchan@gmail.com
The Red Queen hypothesis describes the coevolutionary dynamic between predator and prey where both partners evolve in tandem to remain competitive. In several cases, rodents have demonstrated resistance to the venoms of their snake predators. For example, the California Ground Squirrel (Otospermophilus beecheyi) exhibits high resistance to the venom of the Pacific Rattlesnake (Crotalus oreganus). Conversely, cases exist where a prey species apparently lacks physiological resistance to the venom of its predator - the Cape Ground Squirrel (Xerus inauris) lacks venom resistance to the predatory Puffadder (Bitis arietans) and Snouted Cobra (Naja annulifera). My research evaluates patterns of venom resistance in a Colorado grassland ecosystem, where the Desert Massasauga (Sistrurus tergeminus edwardsii) and Prairie Rattlesnake (Crotalus viridis) predate upon a suite of rodent species. Field sites are located in northern (one snake predator) and southern Colorado (two snake predators) to investigate patterns of resistance between and within locations at the geographic level. Median lethal dose assays are used to assess venom resistance of select rodent populations to specific rattlesnake venoms. Serum-based assays determine the protective effect that a rodent’s serum exhibits against specific venom components. Preliminary results indicate a moderate protective effect of the serum of Deer Mice (Peromyscus maniculatus) and Meadow Voles (Microtus pennsylvanicus) against Prairie Rattlesnake venoms, but not Desert Massasauga venom. Studying patterns of venom resistance in a system with two predator and multiple prey species allows us to understand better the evolution of such defenses and to evaluate whether local adaptation exists. |
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10. 15:45 Snake Eyes Contain a Soft, Deformable, Lens: a Game Changer in Accommodating Refractive Error. Cliff Fontenot*, Southeastern Louisiana University; Nisha Lama, Southeastern Louisiana University cfontenot@selu.edu
The eyes of snakes are morphologically unique, evolved from a lineage of lizards that had severely degenerated eyes, and essentially reinvented its eye. One result is that snakes lack the accommodation muscles of other vertebrates that would move the lens forward (amphibians) or backward (fishes), or ciliary muscles that change the shape by pulling on its periphery (lizards, birds, mammals). Although Walls (1942) indicated that the snake eye lens is rigid, other authors suggest that it is soft (Beer 1898, Michel 1933, Schaeffel and DeQueiroz 1990, and Schaeffel and Mathis 1991), partly based on calculations of overcoming extensive refractive error. To determine lens hardness and deformability in a variety of North American species, we attempted to compress freshly dissected snake eye lenses 1) by gently squeezing with foreceps, and 2) with a mechanically adjustable stage that compressed the lens against a glass plate equipped with a force sensor. All lenses tested were soft, compressible, and deformable, which suggests a substantial additional accommodation mechanism of lens deformation that may work in concert with lens displacement. |