Donald B Shepard

• PhD
• University of Arkansas at Fayetteville

Roads can act as barriers to animal movement through mortality during crossing attempts or behavioral avoidance. This barrier effect has negative demographic and genetic consequences that can ultimately result in local or regional extinction. Here we use radio-telemetry data on three terrestrial vertebrates (eastern massasauga Sistrurus catenatus,...

Identification of mechanisms that promote variation in life-history traits is critical to understand the evolution of divergent reproductive strategies. Here we compiled a large life-history data set (674 lizard populations, representing 297 species from 263 sites globally) to test a number of hypotheses regarding the evolution of lifehistory trait...

Aim The aim was to examine the links between past biome stability, vegetation dynamics and biodiversity patterns. Location South America. Time period Last 30,000 years. Major taxa studied Plants. Methods We classified South America into major biomes according to their dominant plant functional groups (grasses, trees and shrubs) and ran a random...

Sky Islands present unique landscapes for organismal evolution because they comprise high mountain peaks separated by low valleys with vastly different environmental conditions. The Espinhaço Mountain Range in eastern Brazil is formed of groups of Sky Islands in the states of Minas Gerais and Bahia. Several phylogeographic studies have discovered s...

Accurate knowledge of species distributions is necessary for research and conservation. Slimy Salamanders (Plethodon glutinosus complex) are similar in appearance, tend toward small geographic ranges, and have a propensity for hybridization, necessitating genetic analysis and fine-scale sampling for accurate representation of species distributions....

We describe a new species of Leptophis (parrot snake) from the Cerrado ecoregion of Brazil. The new species, L . mystacinus sp. nov., differs from all other congeners in the following unique character combination: two Spectrum Green (129) to Light Parrot Green (133) dorsolateral stripes separated by a Buff (5) vertebral stripe, usually continuous o...

As many new evolutionary lineages are being discovered and formally named, sequencing topotypes when holotypes are not available becomes essential for taxonomy. This study uses a DNA-taxonomy approach to sequence new populations of the Ischnocnema verrucosa species complex (Brazilian Wart Frogs) from different locations, including, for the first ti...

Crawfish Frog (Lithobates areolatus) occupancy has declined by 35% throughout much of its historic range primarily due to conversion of habitat to agriculture. In Louisiana, USA, most records date prior to the 1970s, and more recently the species has been documented at only a few locations. This study aimed to assess the current distribution and st...

Species identification plays a significant role in biodiversity conservation. As many species remain unrecognized, particularly in neotropical hotspots like the Brazilian Atlantic Forest (AF), novel molecular techniques are being widely employed to bridge this gap. In this study, we used DNA barcoding and phylogenetic tools to identify a new popula...

It is repeatedly stressed the need to characterize the extant biodiversity in tropical ecosystems. However, inventory studies are still progressing slowly in dry ecosystems, leading to the underestimation of their true biodiversity and hindering conservation efforts. In this study, we present primary and secondary data, along with an updated list o...

Nutritional ecology of ropical ecosystems like Neotropical savannas, which are of high conservation concern, is understudied. Sodium is essential for heterotrophs but availability often falls short relative to plant consumer requirements. Savanna plant consumers like ants and termites should be sodium-limited due to high temperatures, nutrient-poor...

Based on concordant differences in morphology, male advertisement call, and 16S mtDNA barcode distance, we describe a new species of Proceratophrys from southern Amazonia, in the states of Mato Grosso and Pará, Brazil. The new species is most similar to P. concavitympanum and P. ararype but differs from these species by its proportionally larger ey...

Rates of climatic niche evolution vary widely across the tree of life and are strongly associated with rates of diversification among clades. However, why the climatic niche evolves more rapidly in some clades than others remains unclear. Variation in life history traits often plays a key role in determining the environmental conditions under which...

Geographic barriers are integral to the processes of dispersal and vicariance, but some barriers, such as rivers, may vary spatiotemporally, potentially affecting biodiversity patterns in significant ways. Fountain Bluff is an isolated upland in the Mississippi River floodplain along the Illinois-Missouri border, USA. The Mississippi River presentl...

Body size varies with many life history and ecological traits. Assessing intraspecific variation in body size, particularly in species with broad distributions, can reveal how selective pressures vary geographically and how populations have adapted locally. We examined body size, growth, and sexual size dimorphism in a population of Eastern Massasa...

In 1999, we began a long-term study in Illinois of the Eastern Massasauga (Sistrurus catenatus), a species of conservation concern throughout its range. We focused on temporal changes in population size (N), adult sex ratio (ASR), and adult-juvenile ratio (AJR) over a 12-year period. At the largest known hibernacula in Illinois, South Shore State P...

Studies of animal movement and space use provide insight into how species interact with their environment to meet food, reproductive, and survival needs. From March 2000 to November 2002, we used radio-telemetry to track the daily movements of 48 Eastern Massasaugas (Sistrurus catenatus) at the southern limit of the species’ distribution. Our goals...

Introduced species can negatively affect natural communities and ecosystems through interactions with native species. Dusky salamanders (genus Desmognathus) are commonly collected from the wild and used as fishing bait, which can result in release outside their native population or beyond the limits of the range of the species. Desmognathus conanti...

Montane regions are centers of endemism and species richness for many taxa, including plethodontid salamanders. The forces creating and maintaining species' elevational range limits have been extensively studied in members of the genus Plethodon. However, the mechanisms underlying these limits are still poorly understood. Prior work has often focus...

Aim The Interior Highlands (Ouachita Mountains and Ozark Plateau) are major physiographical regions of eastern North America and harbour many endemic species. Despite their close proximity, the Ozarks and Ouachitas have different geological histories and relatively distinct species pools. Few studies have tested the biogeographical origins of this...

The southeastern United States (U.S.) has experienced dynamic climatic changes over the past several million years that have impacted species distributions. In many cases, contiguous ranges were fragmented and a lack of gene flow between allopatric populations led to genetic divergence and speciation. The Southern Red-backed Salamander, Plethodon s...

Disturbance alters the structure and dynamics of communities. Here, we examined the effects of seasonal flooding on the lizard community structure by comparing two adjacent habitats, a seasonally flooded and a non-flooded forest, in a Cerrado-Amazon ecotone area, the Cantão State Park, Tocantins state, Brazil. Despite the strong potential impact of...

Life is defined by a capacity for reproduction, yet the ways in which animals reproduce vary tremendously among species. Reproductive life histories are complex phenomena influenced by a variety of factors, such as physical condition of individuals, food supply, bauplan, and phylogenetic history, which are often correlated. Understanding life histo...

Associations between the morphology of animals and their ecology have contributed to our understanding of phenotypic diversity by helping to relate form and function. Most early studies on fishes used traditional measurements of linear distances on the body or fins to quantify morphological variation among taxa. More recently, geometric morphometri...

Inferring the evolutionary and biogeographic history of taxa occurring in a particular region is one way to determine the processes by which the biodiversity of that region originated. Tree boas of the genus Corallus are an ancient clade and occur throughout Central and South America and the Lesser Antilles, making it an excellent group for investi...

Decisions affecting wildlife management and conservation policy of imperiled species are often aided by population models. Reliable population models require accurate estimates of vital rates and an understanding of how vital rates vary geographically. The eastern massasauga (Sistrurus catenatus catenatus) is a rattlesnake species found in the Grea...

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Local adaptation is often invoked to explain hybrid zone structure, but empirical evidence of this is generally rare. Hybrid zones between two poeciliid fishes, Xiphophorus birchmanni and X. malinche, occur in multiple tributaries with independent replication of upstream-to-downstream gradients in morphology and allele frequencies. Ecological niche...

Terrestrial salamanders of the genus Plethodon are closely tied to abiotic environmental habitat features and are particularly sensitive to land use and habitat change. To better understand the effects of land use and habitat fragmentation on population genetic characteristics, we screened 137 primers developed from 454 sequence libraries, and deve...

Among vertebrates, most of the largest genomes are found within the salamanders, a clade of amphibians that includes 613 species. Salamander genome sizes range from ~14 to ~120 Gb. Because genome size is correlated with nucleus and cell sizes, as well as other traits, morphological evolution in salamanders has been profoundly affected by genomic gi...

Morphology of some groups of organisms has been highly conserved over evolutionary time, resulting in genetically divergent taxa with relatively little morphological variation. Genetic studies on salamanders of the genus Plethodon have revealed a high level of morphologically cryptic diversity, and recent ecological and evolutionary studies have su...

Spatial and temporal heterogeneity in environmental factors can have profound effects on diversification in species that are tightly linked to their environments. The Caddo Mountain Salamander (Plethodon caddoensis) inhabits a unique physiographic section of the Ouachita Mountains in central North America, a region in which Pleistocene climatic flu...

Interspecific competition for resources is predicted to be high in dense populations of closely related species and should lead either to species partitioning resources along one or more niche axes, or exclusion of the competitively inferior species. Between 19 June and 19 July 2003, we collected 71 recently metamorphosed Rana areolata (Crawfish Fr...

A total of 107 leptodactylid frogs representing 6 species, Leptodactylus fuscus (n = 15), Leptodactylus leptodactyloides (n = 9), Leptodactylus mystaceus (n = 2), Leptodactylus ocellatus (n = 31), Leptodactylus petersii (n = 31), and Leptodactylus pustulatus (n = 19), collected in the Brazilian state of Tocantins, were examined for helminths. One s...

Climatic changes associated with Pleistocene glacial cycles profoundly affected species distributions, patterns of interpopulation gene flow, and demography. In species restricted to montane habitats, ranges may expand and contract along an elevational gradients in response to environmental fluctuations and create high levels of genetic variation a...

Sky islands provide ideal opportunities for understanding how climatic changes associated with Pleistocene glacial cycles influenced species distributions, genetic diversification, and demography. The salamander Plethodon ouachitae is largely restricted to high-elevation, mesic forest on six major mountains in the Ouachita Mountains. Because these...

Retrieval efficiencies of paper-based references in journals and other serials containing 10 scientific names of fossil amphibians were determined for seven major search engines. Retrievals were compared to the number of references obtained covering the period 1895—2006 by a Comprehensive Search. The latter was primarily a traditional library-based...

Roads have numerous negative ecological effects on terrestrial fauna, and vehicular mortality can have significant demographic consequences for some species. We studied road mortality of reptiles around Carlyle Lake, Clinton County, Illinois, USA, from April 2000 through November 2002, to assess the impact of vehicular traffic and identify influent...

Aim To investigate the influence of climate variables in shaping species distributions across a steep longitudinal environmental gradient. Location The state of Oklahoma, south‐central United States. Methods We used Geographical Information Systems (GIS) niche‐based models to predict the geographic distributions of six pairs of closely related amph...

We studied the ecology of Anolis nitens brasiliensis during late-dry and early-wet season 2005 in a Cerrado habitat in Tocantins state, Brazil. Most lizards were found on tree trunks or leaf litter in non-flooded igapo forest. Most were found in shade or filtered sun on both cloudy and sunny days. Body temperatures (T(b)s) averaged 30.6 degrees C a...

This study was conducted at Carlyle Lake, Clinton County, Illinois. Brood size averaged eight and was not significantly correlated with maternal snout-vent length. Based on preserved snakes, females initiate vitellogenesis in the summer/fall. Vitellogenic follicles reach 20 mm in length by late September, overwinter at this size, and resume growth...

Rhinella ocellata é uma espécie relativamente desconhecida que ocorre no Cerrado brasileiro. Nós estudamos a área de vida e o comportamento de vocalização de uma população dessa espécie no estado do Tocantins, norte do Brasil, no ano de 2004. Diferentemente de outras espécies de bufonídeos, os machos de R. ocellata não migraram para poças ou outros...

Knowledge of mating system characteristics can elucidate forces driving sexual selection. In male pitvipers, both male movement tactics and body size are predicted to be important determinants of reproductive success. We used radio telemetry to monitor free-ranging Sistrurus catenatus (Eastern Massasauga) from 2000 through 2002 to determine whether...

We tested three non-exclusive hypotheses that the lizard, Gymnodactylus carvalhoi, lives in termitaria to avoid thermal extremes, to avoid predators, or because of an abundance of food (dietary specialist). We first confirm that these geckos are restricted to termitaria in the region studied. Body temperatures (Tb) of geckos averaged below environm...

Predators use characteristics such as pattern and shape in forming search images of prey, thereby influencing the evolution of prey morphology. In lizards, sit-and-wait foraging species are thought to have body shapes that enhance their ability to remain cryptic to predators. Structurally complex habitats provide more opportunities for prey to avoi...

nests and into ponds. Tadpoles collected from the ponds had eggs in their guts, and feeding experiments confirmed that free-living tadpoles of L. labyrinthicus eat eggs of other frog species. The reproductive mode of L. labyrinthicus is intermediate between two previously described modes for closely related species. This mode may be adaptive in the...

Body size–age relationships may have important implications for the evolution and maintenance of alternative mating tactics, but these relationships remain largely unexplored in anuran amphibians (frogs and toads). In a single territorial anuran species, smaller noncalling ‘satellite’ males are younger than calling males. These results have led to...

Because prey acquisition in young organisms often has profound effects later in life, understanding the foraging ecology of early age classes is important. We examined diet and prey preference of neonate Eastern Massasaugas (Sistrurus c. catenatus) at Carlyle Lake, Clinton County, Illinois. Prey recovered from free-ranging neonates consisted primar...

Many anurans are thought to be territorial only during breeding; thus these species should exhibit seasonal differences in social behavior. Aggressive behavior and site tenacity, two components of territoriality, were examined in male Rana clamitans (Green Frogs) to test for differences between breeding and nonbreeding seasons. I predicted that agg...

The spatial relationships exhibited by individuals in a population may indicate their social organization. In territorial species interactions between individuals should lead to maximal spacing in a uniform pattern. Using nearest neighbor distances (NND), I tested for territoriality in the green frog (Rana clamitans) by determining if males were un...

Thesis (M.S.)--Illinois State University, 2000. Includes bibliographical references (leaves 52-56) and abstract.