This research perspective focuses on three of the disciplinary areas that have engaged my interest as a professional biologist. My research first focused on life history evolution, but it expanded to include the evolution of viviparity, and developmental biology. My subjects are squamate reptiles, although I do hands-on research largely with lizards. A common theme of the research that I discuss here is the role of eggs and embryos in ecological and evolutionary studies and why that role may be critical to the resolution of important biological problems. In this perspective, I summarize highlights of my major research projects since 1971: 1) life history evolution of West Indian island and mainland Anolis lizards; 2) long-term studies on the demography and egg survival of a small, r-selected Panamanian anole; 3) ecological and physiological studies on the transition between oviparity and viviparity in Sceloporus; 4) costs and benefits of the novel rigid-shelled egg of gekkotan lizards; and 5) embryonic adaptations to low oxygen availability in rigid-shelled eggs of gekkotan lizards. I put these projects in the context of my own developmental trajectory as a biologist; my research has shifted from population biology to embryonic development without breaking the connection between these seemingly disparate disciplines.

We quantified diets of Kemp's Ridley Sea Turtles (Lepidochelys kempii) in Charlotte Harbor National Estuary, Florida, to identify possible ontogenetic variation in prey consumption, to examine the use of local prey, and to contrast the diets of conspecifics at other foraging areas. Dietary analysis was conducted by identifying prey remains recovered in 58 fecal samples from 53 turtles (24.2–63.7 cm midline straight carapace length). Turtles consumed seven prey categories: crustaceans, chelicerates, fish, sessile invertebrates, molluscs, plants/algae, and unidentified items. Spider crabs (Libinia sp.) are the dominant prey consumed in the mangrove estuary, occurring in 94.8% of fecal samples, accounting for 71.4% of dry mass, and as 76.3% in the Index of Relative Importance. We found no significant ontogenetic differences in prey composition between small (<40 cm) and large (≥40 cm) turtles, although crustaceans were more prevalent in diets of the larger turtles. The prey consumed in Charlotte Harbor differed significantly from a similar study of a nearby mangrove estuary in the Ten Thousand Islands. Sandy-Skinned Tunicates (Molgula occidentalis) were the predominant food item in the latter locale, and there were no significant ontogenetic differences in prey composition. A comparison of prey availability and use suggests that Kemp's Ridley Sea Turtles ingested the most abundant prey in the Charlotte Harbor estuary. Geographic differences in diet may reflect localized differences in use of foraging habitat and available prey, but more studies are needed on the availability, use, and selection of both habitat and prey.

Effective conservation action relies on access to the best-available species data. Reptiles have often been overlooked in conservation prioritization, especially because of a paucity of population data. Using data for 549 reptile populations representing 194 species from the Living Planet database, we provide the first detailed analysis of this database for a specific taxonomic group. We estimated an average global decline in reptile populations of 54–55% between 1970 and 2012. Disaggregated indices at taxonomic, system, and biogeographical levels showed trends of decline, often with wide confidence intervals because of a prevalence of short time series. We assessed gaps in our reptile time-series data and examined what types of publication they primarily originated from to provide an overview of the range of data sources captured in the Living Planet database. Data were biased toward crocodilians and chelonians, with only 1% and 2% of known lizard and snake species represented, respectively. Population time-series data stemmed primarily from published ecological research (squamates) and data collected for conservation management (chelonians and crocodilians). We recommend exploration of novel survey and analytical techniques to increase monitoring of reptiles, especially squamates, over time. Open access publication and sharing of data sets are vital to improve knowledge of reptile status and trends, aided by the provision of properly curated databases and data-sharing agreements. Such collaborative efforts are vital to effectively address global reptile declines.

Several species within the terrestrial salamander genus Plethodon exhibit color polymorphisms consisting of individuals with a dorsal stripe (striped) and individuals lacking this feature (unstriped). The ecological and physiological differences between these color morphs have been extensively studied within the ubiquitous and widespread species Plethodon cinereus. We chose to determine whether physiological differences exist between striped and unstriped morphs within the ecologically and morphologically similar Plethodon angusticlavius. We explored energy assimilation at two ecologically relevant temperatures and determined that thermal sensitivity of energy assimilation did not differ between the two color morphs. We found that energy assimilation increased with increasing temperature. Additional studies should examine whether the same ecological and physiological differences that exist between P. cinereus color morphs exist in P. angusticlavius and other polymorphic species of Plethodon.

The behavioral phenotypes of hybrids vary in degree of similarity to their parent species. Unisexual salamanders (Ambystoma laterale sp.), the result of ancient hybridization, contain nuclear DNA of multiple sperm-host species whose habitat preferences differ from one another. We radio tracked unisexual salamanders from four vernal pools to quantify migration distances and post-breeding habitat selection and compared these to published accounts for Blue-Spotted Salamanders (A. laterale) and Jefferson Salamanders (Ambystoma jeffersonianum). Unisexual salamanders used sites with higher numbers of small mammal burrows, lower substrate temperatures, and lower cover by forest floor vegetation than available sites, similar to the sperm-hosts. Unisexual salamanders also migrated distances within the range reported for these sperm-hosts. Even so, individual migration distances were context specific. We implore managers to use caution when designating management zones around breeding pools by considering that some populations may move farther than those reported in published accounts.

Evolutionary significant units are an important level of biodiversity in management and conservation programs. Molecular data are considered a high priority for efficient Broad-Snouted Caiman (Caiman latirostris) conservation. In this study, we used two mitochondrial (COI and 16sRNA) and one nuclear (RAG1) molecular markers to test the hypothesis of independent evolution of geographic lineages across Brazilian river basins. We captured caimans at night and cut one or more scales from the tail for genetic analyses. We obtained genetic data from 37 C. latirostris captured between September 2012 and June 2013 from 13 locations throughout four river basins: Doce, Jequitinhonha, Paraná, and São Francisco. Clades were closely associated to river basins, supporting the presence of three distinct phylogenetic lineages within the 1) São Francisco and Jequitinhonha, 2) Doce, and 3) Paraná river basins. These lineages have been isolated probably since the rise of Pleistocene low sea levels and do not have recent gene flow. They have mtDNA reciprocal monophyly and, therefore, present compelling evidence to be considered as evolutionary significant units. Considering the hidden genetic diversity within this species, we recommend conservation efforts for all three independent units within C. latirostris.

Unidades evolutivas são um importante nível de biodiversidade em programas de conservação e manejo. Dados moleculares têm alta prioridade para estratégias de conservação eficientes de jacarés-de-papo-amarelo. Neste estudo usamos dois marcadores mitocondriais (COI e 16sRNA) e um nuclear (RAG1) para testar a hipótese de que linhagens geográficas desta espécie evoluíram de forma independente em bacias hidrográficas brasileiras. Capturamos jacarés à noite e cortamos uma ou mais escamas da cauda para análises genéticas. Obtivemos dados genéticos de 37 indivíduos de C. latirostris capturados entre setembro de 2012 e junho de 2013 em 13 localidades ao longo de quatro bacias: Doce, Jequitinhonha, Paraná e São Francisco. Os clados foram fortemente associados às bacias, corroborando a existência de três linhagens filogenéticas ocupando as bacias dos rios (1) São Francisco e Jequitinhonha, (2) Doce, e (3) Paraná. Estas linhagens estão isoladas provavelmente desde a elevação do nível do mar durante o Pleistoceno, não apresentando fluxo gênico recente. Elas têm monofilia recíproca de mtDNA e, portanto, apresentam evidências suficientes para serem consideradas Unidades Evolutivas Significativas. Desse modo, recomendamos esforços de conservação direcionados a cada uma destas três unidades independentes dentro de C. latirostris tendo em vista a diversidade genética oculta nesta espécie.

Species that breed in stream environments with unpredictable interannual variability in hydrological regimes may exhibit plasticity in the timing of their breeding activities. Breeding phenology should coincide with conditions and habitats that maximize a species' reproductive success. For the lotic-breeding frog Rana boylii, the timing of breeding activities of a population can vary by more than a month among years. To examine the influence of abiotic factors on the variation in the timing of onset and patterns (i.e., peaks and pauses) in breeding activity of R. boylii, we sampled seven geographically separated sites that covered an extensive portion of the species' range in northwestern California for two breeding seasons. We collected daily environmental and male vocalization data and conducted weekly egg mass surveys at breeding sites. Here, we found the timing of calling activity and oviposition varied markedly among geographically separated sites and between years. Water depth and water temperature influenced calling phenology, whereas water depth and both temperatures (water and air) were significant factors in the timing of oviposition. In general, breeding activity did not commence until water temperatures reached 10°C. Calling and oviposition occurred later at deeper sites with colder, spring water temperatures. Models that predict the timing of breeding activities can improve survey and monitoring efforts and can assist managers of regulated streams in developing flow assessments that are compatible with species' breeding requirements. This information may be particularly useful in developing individual based models to assess overall reproductive success.

Quantitative and qualitative alterations in the environment may have serious ecological consequences for populations of native species. Isolated forest fragments, such as those surrounded by highly urbanized areas, may function similarly to oceanic islands with differences in species diversity compared to mainland areas. These differences may include changes in prey availability and predator pressure, with consequent effects on growth and size of species that interact with those prey and predators. Here, we investigate body size, prey availability, and predation pressure in populations of Bothrops jararaca in two forest fragments within an urban environment in southeastern Brazil (a completely isolated, small forest fragment and a large, well-connected forest fragment). While we found no differences in mean body size or stoutness between the two populations, we did find larger specimens in the small isolated fragment. Prey availability and predator pressure also were significantly lower in the small isolated fragment. The urban environment significantly changes the population ecology between the two locations. These results suggest that lower food availability in the isolated fragment did not decrease the growth rate of B. jararaca, but the low predator pressure increased longevity, resulting in a higher proportion of large snakes in this population.

As is true for many North American turtles, nest predation by Raccoons (Procyon lotor) is the primary cause of mortality of Diamondback Terrapin (Malaclemys terrapin) eggs laid at Jamaica Bay, New York, USA. Previous research using artificial nests at this site indicated that Raccoons located nests based on soil disturbance and ocean water scent, were repelled by human scent, and that vinyl marking flags did not increase predation rates. To test whether more than a decade of subsequent field work at the same site resulted in a change in Raccoon behavior, we replicated the previous 9 artificial nest experiments and added 4 new designs, for 13 total treatments. Our experiments further tested the effects of seven potential cues used for locating nests: moisture, human scent, Diamondback Terrapin scent, ocean water scent, fresh water scent, soil disturbance, and flag markers. Our results corroborate previous research that flag markers are not important cues for Raccoons to locate terrapin nests. Contrary to previous research, we found that ocean water scent no longer increases Raccoon predation and human scent no longer repels Raccoons. Also, in the first test of its kind, we found that Raccoons dug at sites where we applied geosmin, a pungent organic compound produced by Actinobacteria, which is naturally released when soil is disturbed. We conclude that Raccoons in Jamaica Bay have not learned to use signs left by humans and continue to locate nests primarily by relying on the tactile cue of soil disturbance rather than visual markers, moisture, or olfactory cues.

Squamate remains from fossil-bearing deposits are difficult to identify on the basis of their morphology, because their modern relatives lack osteological description. In addition, intraspecific morphological variability of modern taxa is mostly understudied, making taxonomic identification of subfossil bones even more difficult. The aim of this study was to investigate osteological differences between two sympatric gecko species, Thecadactylus rapicauda and Hemidactylus mabouia, both currently occurring in the Lesser Antilles and in the subfossil assemblages of the region. Comparison of several modern museum specimens reveals the intraspecific osteological variability of these lizards and how difficult it is to distinguish between their bones, even though they are from two distant families. This study presents nine osteological characters, allowing for a fully reliable distinction of these two gecko species. These characters are applied to the specific identification of gecko species subfossil remains unearthed from the Pointe Gros Rempart 6 Hole (La Désirade Island, Guadeloupe). Our results confirm the past occurrence of T. rapicauda as well as the historical introduction of H. mabouia on La Désirade Island.

Although tank bromeliads are used by many anuran species, bromeligenous frogs (species strictly dependent on bromeliads for reproduction) occur less frequently and are poorly understood. Crossodactylodes are small frogs confined to bromeliads where they lay their eggs and complete their life cycle without leaving the plant. The genus comprises five species and little information exists on their natural history. We focused on Crossodactylodes itambe—a species confined to a single summit of <0.5 km² at 1,700 m above sea level in the Espinhaço Mountain Range of Brazil. We surveyed frogs in 75 individual bromeliads during two consecutive years, and we used a Generalized Linear Model to investigate the drivers of species abundance related to habitat structure and local climate. We recorded 446 adults, 267 tadpoles, and 40 juveniles over the two years. Most bromeliads contained one adult frog with a mean number of 2–3 tadpoles. The structure of bromeliads influenced species abundance more than local climate. We found that bromeliad size, volume of central tank, and presence/absence of invertebrates and of water influenced frog abundance. Abundance increased in larger bromeliads at higher elevation. Changes in the structure and size of bromeliads might, therefore, affect abundance. We provide the first species assessment and evaluation of threat categories for this poorly known species.

We describe a new species of the genus Lepidophyma from the Pacific lowlands of Guerrero, southern Mexico. Previously referred to as L. smithii, the new taxon is distinguished by a series of morphological characteristics, principally higher numbers of gulars, paravertebrals, and lateral tubercle rows. This new species increases the number of described Lepidophyma to 20 species.

Based on molecular and morphological data sets, we describe a new species of scincid lizard of the genus Lygosoma from Indochina, and redescribe true Lygosoma quadrupes (Linnaeus, 1766). The new species is small and slender, and represents the third member of the L. quadrupes complex, increasing the diversity of Lygosoma species recognized in Southeast Asia to 24. Based on the reevaluation of vouchered specimens from the type locality of L. quadrupes sensu Linnaeus (1766), the recognized geographic distribution of true L. quadrupes is restricted to the island of Java in Indonesia. With 10 species of Lygosoma recognized in Thailand, the country possesses considerable species-level diversity of these enigmatic, semifossorial skinks. In addition to being one of the smallest species in the genus, the new species can be distinguished from all congeners by features of its external morphology, including having small relative limb lengths, longer trunk length, and greater numbers of axilla–groin and paravertebral scale rows. Phylogenetic analyses support three divergent lineages corresponding to recognized and newly described members of the L. quadrupes complex. The descriptions underscore the need for continued and comprehensive biodiversity survey work throughout much of Southeast Asia, particularly in Indochina, where scincid diversity remains poorly understood.

Here we describe the tadpoles of Theloderma gordoni. These tadpoles can be distinguished from other members of the genus Theloderma by having the combination of the following characters: total length (50.1–54.5 mm, stages 28–33); tail shape (abdominal and dorsal fins with a gradual tapering toward the anterior and posterior portions, without an abrupt tapering in the posterior portion); number of marginal papillae in one row on the oral disc (51–55); degree of pigmentation (body dorsally and ventrally practically black, with a slight bluish tint). We also include a comparative analysis and thorough review of tadpole descriptions of other Theloderma.

Habitat loss and degradation are the leading causes of local extinctions, making preservation and restoration of remaining habitat increasingly critical to conserving biodiversity. Mechanisms driving species extinction, however, often begin with habitat loss and seldom are well understood, which greatly limits our ability to mitigate their impacts. The first step in understanding mechanisms that drive local extinction is to identify vital rates affected by habitat degradation. Here we provide a case study of the impact of habitat degradation on individual growth and reproductive rates of Eastern Collared Lizards (Crotaphytus collaris), a species of special concern in the Ozark Mountains. Our data suggest that C. collaris in habitats encroached by dense woody vegetation have reduced age-specific body size, primarily as a result of depressed individual growth rates in their first 2 yr of life. In turn, female C. collaris in habitats with high woody vegetation density have delayed age of maturity (by 1 yr in 70% of females), smaller age-specific clutch size and reduced clutch frequency (up to a 50% decrease in population annual fecundity). We conclude that depressed reproductive rates of C. collaris in degraded habitats likely contribute to population declines in Ozark glades. Our study provides the basis for understanding mechanisms driving population declines of C. collaris in the Ozarks and highlights an underutilized perspective that can be used to link causal factors to local extinction.

Populations at the periphery of a distribution often are genetically and ecologically distinct but tend to be less represented in conservation planning. Peripheral populations may exhibit different behaviors and persist longer than core populations as landscapes change, especially because of human-induced habitat loss and climate change. We examined how landscape factors influence occupancy patterns of Toad Headed Agamas (Phrynocephalus versicolor) along the northern periphery of their range in Asia, a region experiencing increasing development and warming conditions. We collected detection/nondetection data during surveys of 180 sites in Mongolia in 2016. We then developed a set of 70 candidate models that included the single, additive, and interacting effects of nine covariates on occupancy and detection probability and used model selection techniques to determine the best model in the set. We detected agamas at 89 sites (49.4%) and during 141 (39.2%) of 360 surveys. Only one model had strong empirical support, one which included the additive effects of forb cover, grass cover, and ruggedness on occupancy probability and wind speed on detection probability. All four covariates had negative effects, suggesting that ideal conditions for occupancy were areas with little vegetation and topographically flat or gently rolling and that detection was higher in low wind. Average predicted occupancy across all sites was 55%. Our results indicated agamas were more sensitive to vegetation cover in this area than in other parts of their range. Agamas may benefit from future climate conditions that reduce vegetation but face negative impacts from increases in landscape ruggedness because of development activities.