Session 2: General Herpetology IRoom: Ballroom 111B2022-07-28 13:30 - 14:45 |
| Moderator: Andrew Durso |
|
1. 13:30 The Phylogenetics of Lung Loss in Anuran Larvae with Special Consideration for Toad Evolution. Jackson Phillips*, Utat State University; Molly Womack, Utah State University jackson.phillips@uconn.edu
Lungs are a quintessential feature of modern and ancestral tetrapods. Lissamphibians are the sole extant tetrapod class with some secondarily lungless groups. Why lungs are lost is controversial, but one hypothesis is that loss is associated with living in streams, where inflated lungs are unnecessary for respiration and maladaptive for locomotion. Larval frogs, or tadpoles, are typically lunged, but there are several well-known cases of larval loss, often in stream specialists. We present the first comprehensive survey of larval lunglessness and first phylogenetic analysis of lung evolution in tadpoles. We used Bayestraits to test whether lung loss is correlated with larval habitat (ponds vs. streams) and found strong support for a dependent model of lung evolution over an independent model, suggesting lung loss is positively correlated with living in streams. Under all well-supported models, we estimated high rates of losing lungs in streams, near-zero rates of losing lungs in ponds, and near-zero rates of regaining lungs, despite apparent selective pressures to do so. These results led us to speculate that traditional natural selection drives lung loss in stream-dwelling tadpoles, while some form of evolutionary constraint prevents the regain of lungs in lungless clades such as the bufonid toads, even when lungless forms live in oxygen-limited habitats and have evolved other, non-pulmonary means of acquiring atmospheric oxygen. This picture is complicated by the fact that adult frogs retain lungs and larval loss is primarily a shift in developmental timing rather than a total loss of structure, as in plethodontid salamanders. |
|
2. 13:45 Coevolution of hearing and advertisement calls among frogs and toads. Molly Womack*, Utah State University molly.womack@usu.edu
Anurans are well-known for locating and attracting mates via acoustic communication, providing unique opportunities for hearing and acoustic communication research. Anuran hearing research has steadily accumulated over decades and we are now able to ask fundamental questions about the evolution of hearing at broad phylogenetic scales. We combined data from neurophysiological studies on over 100 anuran species to understand how acoustic communication has evolved within Anura. We show surprising variation in hearing ability among species and correlations with body size that are consequential for signal and receiver coevolution. We perform the largest test of call and hearing coevolution that accounts for phylogenetic relationships and find mixed support for the matched filter hypothesis. Furthermore, we raise new questions and outline future directions for anuran hearing research. |
|
3. 14:00 Empty Stomachs are Still Data: Variation in Feeding Frequency in Snakes. Andrew Durso*, Florida Gulf Coast University amdurso@gmail.com
We all know that most snakes eat relatively infrequently and that their stomachs are often empty, which complicates studies of their trophic ecology and forces us to use more complicated methods, such as fecal eDNA or stable isotope analysis. I reviewed 535 studies from >170 countries that reported data on stomach contents from 845 snake species in 16 families. I found that the median percent of individuals with empty stomachs was 72% (range 2-99%, inter-quartile range 50-84%). Pairwise comparisons among families revealed that the stomachs of viperids are empty ~17% less often than those of snakes from other families. The median percent of individuals with empty stomachs was 11% higher in studies of museum specimens compared to wild-caught snakes, with implications for the use of this metric as a proxy for feeding frequency. Variation within a species by sex, body size, and reproductive status is also examined where data are available. There has been little critical discussion of empty stomach frequency in the literature, and the reliance on generalizations and bias towards publishing only novel or unusual diet records hinders our understanding of snake feeding frequency, prey preference, and variation in diet. |
|
4. 14:15 Using bone histology to trace organism-environment interactions in squamates. Holger Petermann*, Denver Museum of Nature and Science holger.petermann@dmns.org
Study of organism-environment interactions – the interplay of biotic and abiotic factors steering organismic evolution – traditionally requires in-the-field observations and measurements. As field methods and measuring techniques improve, older data loses usefulness. Historic museum collections may be unusable for studying impacts of environmental and climate change on populations, species, and faunas at a longer time-scale. This limits the predictive capabilities of organism-environment interaction research. However, understanding these interactions is crucial for predicting effects of ongoing environmental and climate change on the species’ evolutionary success and ecosystem persistence. Using bone histology, I investigated links between organismic growth patterns, longevity, body size, and environmental parameters. I found a robust correlation of early growth success and temperature and precipitation regimes in the first two growth seasons for the tiger whiptail lizard, Aspidoscelis tigris. Expansion to over 20 squamate taxa from the SW USA produced complex relationships that highlight two main factors for the success of such analyses: 1) Organism-environment interactions are highly species-specific complicating multi-taxon data analysis; 2) comprehensive analysis requires sample sizes >30 individuals per taxon. Continued collecting and historic museum collections are crucial for building necessary specimen numbers and allow investigation of longer time spans, thus strengthening the predictive power of recovered correlations. Because bone histology is largely independent from in-the-field measurements and observation, it adds usefulness to museum collections and enables comparison to (sub-) fossil specimens with similar ecological roles and/or environments. Thus, bone histology provides an additional starting point for predicting organism responses to environmental change at multiple levels. |