Toby J. Hibbitts

Naturally occurring variation in tadpole morphology and performance linked to predator regime.

Divergent natural selection drives a considerable amount of the phenotypic and genetic variation observed in natural populations. For example, variation in the predator community can generate conflicting selection on behavioral, life-history, morphological, and performance traits. Differences in predator regime can subsequently increase phenotypic and genetic variations in the population and result in the evolution of reproductive barriers (ecological speciation) or phenotypic plasticity. We evaluated morphology and swimming performance in field collected Bronze Frog larvae (Lithobates clamitans) in ponds dominated by predatory fish and those dominated by invertebrate predators. Based on previous experimental findings, we hypothesized that tadpoles from fish-dominated ponds would have small bodies, long tails, and large tail muscles and that these features would facilitate fast-start speed. We also expected to see increased tail fin depth (i.e., the tail-lure morphology) in tadpoles from invertebrate-dominated ponds. Our results support our expectations with respect to morphology in affecting swimming performance of tadpoles in fish-dominated ponds. Furthermore, it is likely that divergent natural selection is playing a role in the diversification on morphology and locomotor performance in this system.

Molecular phylogeny of Panaspis and Afroablepharus skinks (Squamata: Scincidae) in the savannas of sub-Saharan Africa

African snake-eyed skinks are relatively small lizards of the genera Panaspis and Afroablepharus. Species allocation of these genera frequently changed during the 20th century based on morphology, ecology, and biogeography. Members of these genera occur primarily in savanna habitats throughout sub-Saharan Africa and include species whose highly conserved morphology poses challenges for taxonomic studies. We sequenced two mitochondrial (16S and cyt b) and two nuclear genes (PDC and RAG1) from 76 Panaspis and Afroablepharus samples from across eastern, central, and southern Africa. Concatenated gene-tree and divergence-dating analyses were conducted to infer phylogenies and biogeographic patterns. Molecular data sets revealed several cryptic lineages, with most radiations occurring during the mid-Miocene to Pliocene. We infer that rifting processes (including the formation of the East African Rift System) and climatic oscillations contributed to the expansion and contraction of savannas, and caused cladogenesis in snake-eyed skinks. Species in Panaspis and Afroablepharus used in this study, including type species for both genera, formed a monophyletic group. As a result, the latter genus should be synonymized with the former, which has priority. Conservatively, we continue to include the West African species P. breviceps and P. togoensis within an expanded Panaspis, but note that they occur in relatively divergent clades, and their taxonomic status may change with improved taxon sampling. Divergence estimates and cryptic speciation patterns of snake-eyed skinks were consistent with previous studies of other savanna vertebrate lineages from the same areas examined in this study.

Ecology of a Population of the Narrow-Headed Garter Snake (Thamnophis rufipunctatus) in New Mexico: Catastrophic Decline of a River Specialist

Abstract We studied natural history and ecology of Thamnophis rufipunctatus at San Francisco Hot Springs, Catron County, New Mexico. Gee minnow traps were more effective at sampling adults than opportunistic captures. Females were larger than males in snout–vent length and mass, but males had longer tails. Although females were larger, rates of growth for juvenile males and females were similar. In 1996, the population was ca. 7.2 adult snakes/ha; however, we did not detect snakes in subsequent visits. Thamnophis rufipunctatus was most likely to be captured at sites with steep riverbed slope and large rocks of uniform size. Diet was exclusively fish, of which a large proportion was the introduced Gambusia affinis. This population of T. rufipunctatus was one of the most robust in the United States and it has completely disappeared in <10 years.

Why didn’t the lizard cross the road? Dunes sagebrush lizards exhibit road-avoidance behaviour

Abstract Context. Research has shown many negative effects of roads and traffic on wildlife and other biodiversity. The direct and indirect mechanisms through which roads and traffic harm animal populations vary across taxa, making mitigation of road effects a great challenge for conservation. As such, a large toolkit of species-specific management techniques may be needed to mitigate the negative effects of roads for wildlife and other biodiversity. The dunes sagebrush lizard, Sceloporus arenicolus, is a psammophilic (sand-loving) habitat specialist endemic to the Mescalero–Monahans Sandhills ecosystem of New Mexico and Texas. Within this ecosystem, roads fragment shinnery oak sand-dune landforms occupied by the species. Aims. In the present study, we conducted behaviour trials in experimental enclosures to test whether the smallest roads restrict movements of the dunes sagebrush lizard. In addition, we also conducted trials to evaluate whether a sand-filled wildlife-crossing feature could facilitate road crossing. Methods. We conducted behavioural trials on 24 dunes sagebrush lizards in our control enclosure and 22 lizards in our road and sand-filled wildlife-crossing enclosure. Movements were recorded for 15 min. The final locations at the end of each trial were analysed using circular statistics to determine whether movements in the road or the sand-filled wildlife-crossing enclosures were different from the control. Key results. Our results supported the hypotheses that dunes sagebrush lizards avoid roads and do so according to a surface-avoidance mechanism. We also found that the wildlife crossing-feature design tested here had no effect on the movements or road-crossing frequency of dunes sagebrush lizard. Conclusions. Surface-avoidance behaviour indicated that roads will persistently affect the movements of dunes sagebrush lizard, even when traffic is not present. Also, more research into an effective wildlife crossing is needed to increase connectivity of fragmented populations. Implications. These findings help evaluate the impact of roads in creating isolated populations that experience increased demographic stochasticity and, in some instances, localised extirpation in this species. Our study can guide conservation plans for the dunes sagebrush lizard, and contribute to our understanding of road effects on biodiversity in general.

Mitochondrial genetic variation within and between Holbrookia lacerata lacerata and Holbrookia lacerata subcaudalis, the spot-tailed earless lizards of Texas

ABSTRACT We examined genetic relationships among individuals and populations of the species Holbrookia lacerata, the spot-tailed earless lizard, using whole mitochondrial genomes. Lizards were collected from south, central and west Texas. We found significant amounts of genetic structure among populations and evidence of two major reciprocally monophyletic groups of spot-tailed earless lizards in Texas. Holbrookia lacerata lacerata occurs on the Edwards Plateau and adjacent regions of West Texas north of the Balcones Escarpment, while Holbrookia lacerata subcaudalis occurs in South Texas and adjacent Mexico south of the Balcones Escarpment. These two recognised subspecies correspond to the two clades we discovered. Holbrookia l. lacerata occupies much of its historical range at sometimes high population densities, while populations of H. l. subcaudalis appear to be highly fragmented based on recent observations compared to their historical range.

Comparison of Recent Oil and Gas, Wind Energy, and Other Anthropogenic Landscape Alteration Factors in Texas Through 2014

Recent research assessed how hydrocarbon and wind energy expansion has altered the North American landscape. Less understood, however, is how this energy development compares to other anthropogenic land use changes. Texas leads U.S. hydrocarbon production and wind power generation and has a rapidly expanding population. Thus, for ~47% of Texas (~324,000 km2), we mapped the 2014 footprint of energy activities (~665,000 oil and gas wells, ~5700 wind turbines, ~237,000 km oil and gas pipelines, and ~2000 km electrical transmission lines). We compared the footprint of energy development to non-energy-related activities (agriculture, roads, urbanization) and found direct landscape alteration from all factors affects ~23% of the study area (~76,000 km2), led by agriculture (~16%; ~52,882 km2). Oil and gas activities altered <1% of the study area (2081 km2), with 838 km2 from pipelines and 1242 km2 from well pad construction—and that the median Eagle Ford well pad is 7.7 times larger than that in the Permian Basin (16,200 vs. 2100 m2). Wind energy occupied <0.01% (~24 km2), with ~14 km2 from turbine pads and ~10 km2 from power transmission lines. We found that edge effects of widely-distributed energy infrastructure caused more indirect landscape alteration than larger, more concentrated urbanization and agriculture. This study presents a novel technique to quantify and compare anthropogenic activities causing both direct and indirect landscape alteration. We illustrate this landscape-mapping framework in Texas for the Spot-tailed Earless Lizard (Holbrookia lacerata); however, the approach can be applied to a range of species in developing regions globally.

Genetic Structure is Inconsistent with Subspecies Designations in the Western Massasauga Sistrurus tergeminus

Abstract The massasauga Sistrurus catenatus was historically divided into three subspecies, but this long-standing taxonomy has recently been called into question. Genetic research now recognizes a split of the species into the eastern massasauga S. catenatus and western massasauga S. tergeminus, with the latter split into two subspecies, the desert massasauga S. t. edwardsii and the prairie massasauga S. t. tergeminus. Although the distinction between geographically isolated populations of S. catenatus and S. tergeminus is well-supported genetically, the geographic relationships among populations of S. t. tergeminus and S. t. edwardsii remain unresolved because of incomplete sampling throughout the species’ range. This poses a difficult challenge for conservation and management of this species. Sistrurus t. tergeminus does not have state or federal conservation status, but S. t. edwardsii has been petitioned for listing under the U.S. Endangered Species Act. In this study, we used nuclear and mitochondri...

Resolving Questionable Records of Pituophis ruthveni (Louisiana Pinesnake)

Abstract Pituophis ruthveni (Louisiana Pinesnake) is considered one of the rarest snakes in North America. For that reason, P. ruthveni is not well represented in scientific collections, and each existing specimen is very important. Some museum records for the species are considered questionable or unverified, especially those that represent extralimital records or those from habitats not normally utilized by Louisiana Pinesnake. Clarifying these questionable Louisiana Pinesnake records will ultimately provide a better understanding of its historic and current distribution, which is necessary for listing decisions, critical-habitat designation, and overall conservation efforts for the species. To resolve this uncertainty, we performed a multivariate analysis using 13 morphological characters on 50 specimens representing 3 snake groups: (1) P. ruthveni (n = 23), (2) P. catenifer sayi (Bullsnake; n = 23), and (3) questionable or unverified snakes (n = 4). We included Bullsnake because they are sister to Louisiana Pinesnake genetically and also most morphologically similar. We identified all questionable records of Louisiana Pinesnake examined as Bullsnake. Blotch count, ventral-scale number, and scale-row number at mid-body were the most reliable characters for distinguishing between groups. These results have potential conservation implications for the species. The influence of these erroneous records could be substantial in future research and conservation of the species due to the relatively few known specimens of Louisiana Pinesnake. We recommend that the specimens we identified be annotated and considered erroneous records.

An Improved Approach for Forecasting Ecological Impacts from Future Drilling in Unconventional Shale Oil and Gas Plays

Directional well drilling and hydraulic fracturing has enabled energy production from previously inaccessible resources, but caused vegetation conversion and landscape fragmentation, often in relatively undisturbed habitats. We improve forecasts of future ecological impacts from unconventional oil and gas play developments using a new, more spatially-explicit approach. We applied an energy production outlook model, which used geologic and economic data from thousands of wells and three oil price scenarios, to map future drilling patterns and evaluate the spatial distribution of vegetation conversion and habitat impacts. We forecast where future well pad construction may be most intense, illustrating with an example from the Eagle Ford Shale Play of Texas. We also illustrate the ecological utility of this approach using the Spot-tailed Earless Lizard (Holbrookia lacerata) as the focal species, which historically occupied much of the Eagle Ford and awaits a federal decision for possible Endangered Species Act protection. We found that ~17,000–45,500 wells would be drilled 2017‒2045 resulting in vegetation conversion of ~26,485–70,623 ha (0.73–1.96% of pre-development vegetation), depending on price scenario (

Comparative call characteristics in the anuran subgenus Nenirana

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