Comparative biologists often conceptualize sexual size dimorphism (SSD) as a static characteristic of adult populations, but recent work has emphasized that SSD reflects a developmental process in which males and females “grow apart” in body size. This ontogenetic perspective requires knowledge of (1) the demographic factors that give rise to SSD (e.g., differential survival, migration, or growth) and (2) the ontogenetic timing of these sexual differences (e.g., juvenile, maturational, or adult divergence). Together, such data help formulate testable hypotheses concerning proximate physiological mechanisms responsible for the development of SSD. To illustrate this approach, we present a case study of two sympatric lizard congeners with opposite patterns of SSD (Sceloporus virgatus: female-larger; S. jarrovii: male-larger). Using mark-recapture data, we show that (1) sex differences in survival and migration cannot account for SSD, and (2) both nonlinear growth models and age-specific linear growth rates identify sexually dimorphic growth as the cause of SSD in each species. SSD develops in S. virgatus because females grow more quickly than males, particularly during the spring mating season. By contrast, SSD develops in S. jarrovii because males grow more quickly than females throughout the first year of life, particularly in association with vitellogenesis and gestation in females. Thus, opposite developmental patterns of SSD in these species may reflect underlying differences in energetic trade-offs between reproduction and growth.

We describe oviposition site, clutch characteristics and breeding phenology of a population of Eurycea lucifuga, the cave salamander, from SE Missouri, to understand the impact of biophysical and biotic conditions on a troglophilic species. In the field oviposition occurred in underground rimstone pools over 6 mo, with most reproduction occurring from August to October. Individual females deposited 1–31 eggs per pool, hatching approximately 10–20 d post-oviposition. Larvae remained in the pools as long as 6 mo before moving into the stream. We raised eggs and larvae of E. lucifuga in the lab and compared survival, growth, and development under three temperature regimes. Embryonic growth was slowest at cooler temperatures and produced larger larvae, while temperatures typical of summer surface stream temperatures resulted in high mortality. We suggest that the cool, predator free habitats of midwestern caves have allowed for a longer reproductive season in E. lucifuga, but that the unpredictable hydrology and limited food supply of these cave environments has expanded the breeding period and slowed embryonic and larval development.

Investigations of natural history trade-offs between reproduction and immunity are common throughout the literature. Most previous studies of such trade-offs have focused on how resources can be drawn from immune response to fuel reproduction. Our results demonstrate that resources also can be shifted from reproduction to immunity. Immunologically-challenged male northern cricket frogs (Acris crepitans) expressed reduced investment in reproduction. Spermatic cyst diameter, germinal epithelium depth, and gonadosomatic index were smaller in antigen-injected males relative to those injected with a sham (saline injected) and noninjected control animals. Although body size increased in all groups during this study, linear growth and body mass did not appear to be significantly different among these three treatment groups. These results demonstrate indirectly that in A. crepitans immune response may increase metabolic demand for resources and fuel that need from the stores normally used to support male reproduction. We speculate that anything eliciting an immune response in this species may reduce male fertility, so pathogens and toxins at levels that are currently believed to be relatively harmless may impact populations in ways we could not previously predict.

Because sex is determined by incubation temperatures in sea turtles and immature animals are not sexually dimorphic externally, circulating levels of testosterone measured with radioimmunoassay (RIA), in conjunction with laparoscopies, have been used to estimate sex ratios. From September to December 1995 to 1997, and from June to December 1998 to 2002, we sampled blood from 1106 juvenile loggerhead sea turtles (Caretta caretta) incidentally captured in pound nets set in Core and Pamlico Sounds, North Carolina to measure testosterone levels. Laparoscopies of 89 of these turtles revealed a sex ratio of 2.1F:1M, similar to other juvenile loggerhead populations along the southeastern coast of the USA. Laparoscopies demonstrated that testosterone levels correctly identified males during summer months (water temperatures >23 C), but were unreliable during late autumn/winter months (water temperatures ≤16 C). During the summer months, females (n  =  201) exhibited testosterone concentrations with an upper limit of 239.0 pg/ml, and males (n  =  69) exhibited a lower limit of 372.0 pg/ml, for a sex ratio of 2.9F:1.0M. We recommend that verification of the RIA should be conducted by laparoscoping a subset of turtles sampled in all sex ratio studies. In addition, this verification should be conducted at several different times throughout the year to evaluate any possible seasonal effects on testosterone concentrations.

Hellbenders are large aquatic salamanders. The Ozark subspecies is in decline through its range. This is the first comprehensive report on hematologic and serum chemistry for both Ozark and eastern hellbenders. Blood samples were analyzed for 25 parameters in 33 Ozark hellbenders from the North Fork of White River and the Eleven Point River in Missouri and 45 eastern hellbenders from the Davidson River-Looking Glass Creek in North Carolina and the Cooper Creek in Georgia. Each river was considered a population. In general, the majority of the blood parameters analyzed were similar between populations and subspecies for same-sex individuals, although a few significant differences were identified. The baseline data we acquired are important for future monitoring of hellbender populations, particularly as Ozark hellbender populations continue to age.

The bog turtle Glyptemys ( =  Clemmys) muhlenbergii is an inhabitant of groundwater-fed sedge meadows in the northeastern and southeastern United States. Observations of bog turtle habitats throughout the species' range demonstrate that livestock grazing has been an important factor in staving off successional processes and abating large-scale invasions by tall-growing, competitively dominant plants—many of which are exotic in origin. The demise of small-scale dairy farming over the past three decades has led to the pastoral abandonment of the majority of bog turtle habitats in the Northeast. As a consequence, habitats are being degraded by the growth of invasive flora, changes in hydrology, and loss of turtle microhabitats created by livestock. In this study we compared the number of bog turtle captures, bog turtle demographic parameters, bog turtle densities, and vegetation at sites that are currently grazed (n  =  12) and at sites in which grazing had recently ceased (n  =  12). This analysis demonstrated that grazed sites contained greater numbers of turtles, greater turtle density, and greater frequency of occurrence for juvenile turtles. Grazed sites also contained greater cover of low-growing herbaceous vegetation and lower heights of tall-growing exotic and/or invasive vegetation than the formerly grazed sites. We hypothesize that nutrient enrichment from manure and agricultural run-off has promoted the establishment and growth of invasive plant species at many of the sites, but livestock grazing has kept these plants in check. When livestock are removed, invasive species proliferate, and the hummocky microtopography maintained by the livestock traffic is often reduced to a mat of vegetation. This investigation showed that efforts to preserve viable populations of bog turtles may depend on the preservation of low-intensity, pasture-based dairy and beef farming.

One of the basic tenets of ecological niche theory is that closely-related, ecologically similar species do not coexist. When such species co-occur over large portions of their geographic ranges, they often are segregated by habitat. The objective of this study was to evaluate experimentally the roles of abiotic habitat characteristics and competition in the habitat segregation of two sister taxa of Hylid treefrogs. These species co-occur throughout the southeastern United States, but Hyla cinerea typically breeds in permanent ponds, while H. gratiosa breeds in temporary ponds. I conducted a reciprocal transplant experiment using enclosures in natural ponds to compare survival, larval period, and size at metamorphosis for both species in temporary and permanent ponds. While the overall survival of H. cinerea was higher than H. gratiosa and survival varied among localities, there were no significant distinctions in survival between temporary and permanent ponds. Hyla cinerea tadpoles had longer larval period and larger size at metamorphosis in temporary ponds relative to permanent ponds. Hyla gratiosa tadpoles were significantly larger at metamorphosis in temporary ponds than permanent ponds, and had longer larval periods when encountering only conspecifics than when raised with H. cinerea. The results of these experiments, in conjunction with other work, suggest that a combination of factors is likely responsible for the habitat segregation between these two species.

Island populations are convenient models of large-scale evolutionary processes and provide natural replicates of evolution. Recently founded island populations also provide an opportunity to study populations derived from few individuals, and these populations, in particular, often show rapid diversification. Here we report morphological and molecular data for the túngara frog, Physalaemus pustulosus, from three different islands of Panama: Coiba, a large island with a rather old túngara frog population; Isla Grande, a small island with a fairly recent population of túngara frogs, and Barro Colorado Island (BCI), a large island artificially created by flooding to form the Panama Canal about 100 yr ago. Frogs from the two natural islands, but not those from BCI, were significantly larger than frogs from the mainland, which is consistent with the “island rule” stating that small species on islands tend to be larger while large species tend to be smaller than their mainland relatives. Genetic diversity, estimated from allelic richness at seven microsatellite loci, was drastically reduced in the Isla Grande population, whereas heterozygosity was not reduced. This result suggests that this island population of frogs went through a severe and recent bottleneck.

The dynamics of reptile populations in urban landscapes are poorly understood. We studied demography of an urban population of the Texas horned lizard (Phrynosoma cornutum), a species that apparently declines in abundance following urban development but may persist in localized areas. We located and captured lizards within an urban reserve at Tinker Air Force Base, Oklahoma, from June 2003 to October 2005. Lizards were monitored using radiotelemetry, and data were collected on morphometrics, survival, and reproduction. These data were applied to a life-table analysis that estimated the hatchling survival rate necessary to maintain a stable population. Females were larger than males in adult and juvenile cohorts. Mark-recapture sessions resulted in estimates (±1 SE) of 53 ± 11 individuals in the population and a density of 5.00 ± 1.04 lizards/ha. Annual rates of survival were estimated to be 0.59–0.70 for adult lizards and 0.45 for juvenile lizards. Mean (±1 SE) clutch size was 17.4 ± 0.8 eggs, incubation periods ranged from 49 to 68 days, and 60% of nests survived to hatching. Assuming a single clutch per year, fecundity of adult females was 5.22 female hatchlings/female/year. From application of Euler's equation, the hatchling survival rate needed for population stability ranged from 0.19 to 0.25. Relative to other, more southerly populations of P. cornutum, our study population had higher survival but lower reproductive rates. Reduced reproduction was likely due to latitudinal trends associated with body size, but we could not separate confounded influences of urban environment and latitude on survival. Relative to other phrynosomatine lizards, Texas horned lizards in our study population were characterized by high survival, moderate reproductive output, and delayed maturation.

Recent phylogeographic work on Taricha torosa has revealed that the subspecific lineages, T. t. torosa and T. t. sierrae, are distinct evolutionary lineages that form a secondary contact zone in the southern Sierra Nevada of California. I examined the dynamics of this contact zone using two allozyme markers, mitochondrial DNA, morphometrics (head shape), and head color pattern. The subspecific lineages interbreed where they meet, and form a hybrid zone centered along the Kaweah River in Tulare County. Clines among genetic markers had similar shapes and centers, and ranged from 7–10 km wide. There is evidence of selection against hybrid genotypes in the center of the hybrid zone. Analyses of head shape and color pattern show that the two subspecies are phenotypically differentiated, and that patterns of differentiation in these characters are congruent with the genetic clines. The two subspecies constitute distinct evolutionary lineages and merit recognition as separate species: T. torosa (California newt) and T. sierrae (Sierra newt).

We describe a new species of forest frog (genus Platymantis) from 180–300 m above sea level on Mt. Lihidan in the northwestern part of Panay Island, Philippines. It is assigned to the Platymantis dorsalis species group and is distinguished from congeners by external morphology, various spectral and temporal components of the advertisement call, and a preference for terrestrial, limestone microhabitat. Unique morphological characters include a moderately large body (27.7–34.3 mm SVL for 15 males), slightly expanded terminal finger and toe discs, distinctly rugose dorsal and lateral skin, pronounced supratympanic fold, protuberant rictal tubercle cluster, hidden dorsal and posterior edges of tympanum, and unique coloration.

I describe a new species of treefrog of the genus Litoria from Sudest Island, in the Louisiade Islands, off the southeastern tip of New Guinea. The new species is readily distinguishable from all other Papuan species of the genus except L. prora and L. humboldtorum in its possession of fully webbed hands and a fleshy rostral spike. It is distinguished from these species by its larger size, reduced crenelated fringes on arms and legs, absence of heel lappets, reduced papillae on the mandibular margin, and details of color pattern. I describe the tadpole for the new species and show that it differs from that of L. humboldtorum in morphology and color pattern. All three species form cohesive, distinct clusters in multivariate morphometric space. Morphologically, the new species most closely resembles L. humboldtorum, known from Yapen Island and the nearby New Guinea mainland 2000 km to the northwest. The new species was not found in recent surveys of nearby Rossel and Misima islands, the other large islands of the Louisiade group, and it may be restricted to Sudest Island.

We describe four new species of anoles (genus Anolis) from the Serranía de Tabasará, west-central Panama. Two of the new species are most similar in external morphology to a cluster of Central American species that are short-legged (fourth toe of adpressed hindlimb reaches only to tympanum), have a single elongated prenasal scale, smooth ventral scales, and slender habitus, often delicate. They differ from the other species in this cluster by hemipenial morphology and scalation characteristics. One of the new species appears to be most similar to A. pachypus and A. tropidolepis from which it differs by male dewlap coloration and its very small dorsal head scales. The fourth new species appears to be most similar to A. laeviventris from which it differs by its multicarinate head scales, lack of heterogeneous flank scalation, and an overall green coloration.

A new species of rhacophorid frog of the genus Chiromantis is described from Phnom Samkos in the northwestern section of the Cardamom Mountains, Cambodia on the basis of having the following unique characteristics: green blood; turquoise bones; a thick, white line running from below the midsection of the eye onto the upper lip to the shoulder; and fingers III and IV being more than one-quarter webbed. It is further distinguished from its congeners by a unique combination of additional morphological and color pattern characteristics. This new species is the eighth potential endemic known from the Cardamom Mountains and underscores the need for continued field work in this remote section of Indochina.

A new species of Uraeotyphlus (Gymnophiona: Uraeotyphlidae) is described on the basis of a single, distinctive specimen from the Western Ghats of southern Kerala, India. This species is most similar to U. malabaricus (Beddome) in that it lacks a clear differentiation between primary annuli and their higher-order (secondary or tertiary) subdivision. The pattern of annulation among species of Uraeotyphlus falls into two clear types based on the differentiation of primary and higher-order annuli, and the number of annular divisions per vertebra and whether this varies along the body. This difference is reflected in our recognition of oxyurus-group (U. interruptus, U. menoni, U. narayani, U. oxyurus) and malabaricus-group (U. malabaricus and a new species described herein) species within Uraeotyphlus.