Nancy E. Karraker

Contrasting road effect signals in reproduction of long- versus short-lived amphibians

Despite an increasing understanding of the effects of roadways on amphibian populations, no studies have examined road effects on demographic traits other than survival. We predicted that road mortality could exert a disproportionate effect on fecundity in long-lived species due to shifts in population age structures to younger individuals of smaller size that produce commensurately smaller egg masses. To test this hypothesis, we assessed egg mass sizes of a long-lived amphibian (spotted salamander, Ambystoma maculatum) and short-lived one (wood frog, Rana sylvatica) in wetlands near and far from highways. Egg mass sizes of A. maculatum were smaller in wetlands near highways. In contrast, those of R. sylvatica were similar among wetlands regardless of the distance from highways. We conclude that paved highways with moderate traffic volume may be having important effects on populations of long-lived amphibians through mortality-mediated depression of reproduction.

Temperature‐dependent acute toxicity of methomyl pesticide on larvae of 3 Asian amphibian species

Relative to other animal taxa, ecotoxicological studies on amphibians are scarce, even though amphibians are experiencing global declines and pollution has been identified as an important threat. Agricultural lands provide important habitats for many amphibians, but often these lands are contaminated with pesticides. The authors determined the acute toxicity, in terms of 96-h median lethal concentrations, of the carbamate pesticide methomyl on larvae of 3 Asian amphibian species, the Asian common toad (Duttaphrynus melanostictus), the brown tree frog (Polypedates megacephalus), and the marbled pygmy frog (Microhyla pulchra), at 5 different temperatures (15 °C, 20 °C, 25 °C, 30 °C, and 35 °C) to examine the relationships between temperature and toxicity. Significant interspecific variation in methomyl sensitivity and 2 distinct patterns of temperature-dependent toxicity were found. Because high proportions of malformation among the surviving tadpoles were observed, a further test was carried out on the tree frog to determine effect concentrations using malformation as the endpoint. Concentrations as low as 1.4% of the corresponding 96-h median lethal concentrations at 25 °C were sufficient to cause malformation in 50% of the test population. As the toxicity of pesticides may be significantly amplified at higher temperatures, temperature effects should not be overlooked in ecotoxicological studies and derivation of safety limits in environmental risk assessment and management.

Blood clinical biochemistry and packed cell volume of the Chinese three-striped box turtle, Cuora trifasciata (Reptilia: Geoemydidae)

Abstract: Reference intervals for blood biochemical analytes and packed cell volume are useful to veterinarians and conservation programs for monitoring the health of threatened species. Populations of the critically endangered Chinese three-striped box turtle, Cuora trifasciata (Bell, 1825), are heavily depleted in the wild because of overharvesting; and many individuals are now maintained in captive breeding programs. Reference intervals of biochemical analytes and packed cell volume were established for individuals of this species held in a captive breeding program at Kadoorie Farm and Botanic Garden, Hong Kong. Blood samples were obtained from 86 healthy individuals from a captive population during annual health examinations between 2006 and 2010. Packed cell volume and 17 biochemical analytes were measured, and data were analyzed using both multivariate and univariate statistical analyses. Significant differences in eight analytes between males and females were identified. Ten analytes were found to increase or decrease significantly with the body weight of the turtles. The reported plasma reference intervals, based on 2.5th and 97.5th percentiles, may serve as benchmarks for clinical assessment and conservation of this critically endangered species.

Growth Rate and an Evaluation of Age Estimation for the Endangered Big-Headed Turtle (Platysternon megacephalum) in China

Abstract Understanding growth patterns is critical for determining age and size at sexual maturity and longevity in species that are severely threatened by over-collection and habitat loss, particularly in poorly understood species in tropical East Asia. Using data collected during a 9-year mark–recapture study, we fit the von Bertalanffy and logistic growth models to examine growth patterns of the endangered Big-headed Turtle (Platysternon megacephalum). Growth rate of P. megacephalum was best described by the von Bertalanffy model. Mean age at maturation for female and male P. megacephalum was 8 and 13 years. At maturity for female and male P. megacephalum, mean carapace length was 100 mm and 130 mm, respectively. We determined that counting growth rings on the carapace and plastron was not a reliable method for estimating ages. The long time to maturation in P. megacephalum may be costly in harvested populations, with individuals potentially being removed from populations prior to first reproduction. The growth patterns we have documented, and associated information on body size and age at sexual maturity, yield metrics that may be used to assess the effects of harvesting in populations and may contribute to conservation efforts for this endangered species.

Are toad tadpoles unpalatable: Evidence from the behaviour of a predatory dragonfly in South China

Predators are important determinants of amphibian community structure in aquatic habitats, and larval odonates can be significant predators of amphibian larvae. Despite their toxicity as adults, the palatability of bufonid eggs and tadpoles to vertebrate and invertebrate predators remains widely debated. I tested the palatability of hatchling tadpoles of the Asian common toad (Bufo melanosticus) and four other amphibians in Hong Kong to larvae of the dragonfly Pantala flavescens. Attempted predation of Bufo melanostictus hatchling tadpoles by P. flavescens resulted in 100% mortality of hatchlings, but none were consumed. All other amphibians were palatable to P. flavescens. Development of toxins may not protect early-stage bufonids from invertebrate predators that detect prey by visual cues and then make a debilitating strike. These findings present the first report of unpalatability of bufonid tadpoles to an invertebrate predator and provide evidence that unpalatability of early stage bufonids to odonates may decrease through ontogeny.

Evolutionary response to global change: Climate and land use interact to shape color polymorphism in a woodland salamander

Abstract Evolutionary change has been demonstrated to occur rapidly in human‐modified systems, yet understanding how multiple components of global change interact to affect adaptive evolution remains a critical knowledge gap. Climate change is predicted to impose directional selection on traits to reduce thermal stress, but the strength of directional selection may be mediated by changes in the thermal environment driven by land use. We examined how regional climatic conditions and land use interact to affect genetically based color polymorphism in the eastern red‐backed salamander (Plethodon cinereus). P. cinereus is a woodland salamander with two primary discrete color morphs (striped, unstriped) that have been associated with macroclimatic conditions. Striped individuals are most common in colder regions, but morph frequencies can be variable within climate zones. We used path analysis to analyze morph frequencies among 238,591 individual salamanders across 1,170 sites in North America. Frequency of striped individuals was positively related to forest cover in populations occurring in warmer regions (>7°C annually), a relationship that was weak to nonexistent in populations located in colder regions (≤7°C annually). Our results suggest that directional selection imposed by climate warming at a regional scale may be amplified by forest loss and suppressed by forest persistence, with a mediating effect of land use that varies geographically. Our work highlights how the complex interaction of selection pressures imposed by different components of global change may lead to divergent evolutionary trajectories among populations.

Diet of the endangered big-headed turtle Platysternon megacephalum

Populations of the big-headed turtle Platysternon megacephalum are declining at unprecedented rates across most of its distribution in Southeast Asia owing to unsustainable harvest for pet, food, and Chinese medicine markets. Research on Asian freshwater turtles becomes more challenging as populations decline and basic ecological information is needed to inform conservation efforts. We examined fecal samples collected from P. megacephalum in five streams in Hong Kong to quantify the diet, and we compared the germination success of ingested and uningested seeds. Fruits, primarily of Machilus spp., were most frequently consumed, followed by insects, plant matter, crabs and mollusks. The niche breadth of adults was wider than that of juveniles. Diet composition differed between sites, which may be attributable to the history of illegal trapping at some sites, which reduced the proportion of larger and older individuals. Digestion of Machilus spp. fruits by P. megacephalum enhanced germination success of seeds by about 30%. However, most digested seeds are likely defecated in water in this highly aquatic species, which limits the potential benefit to dispersal. The results of our study can be used by conservation-related captive breeding programs to ensure a more optimal diet is provided to captive P. megacephalum.

Signals of forest degradation in the demography of common Asian amphibians

Background Lowland areas in tropical East and Southeast Asia have a long history of conversion from forestland to agricultural land, with many remaining forests being chronically degraded by wood cutting, livestock grazing, and burning. Wetland-breeding amphibians that have evolved in lowland forests in the region have adjusted to changes in habitat composition caused by humans’ activities, and populations continue to persist. However, we have little understanding of the impacts of forest disturbance on these species beyond assessments of abundance and distribution, and species considered to be common and widespread have been largely neglected. Methods We examined body condition and sex ratios of toads (Duttaphrynus melanostictus), predation risk in treefrogs (2 Polypedates spp.), and growth and survival of leaf litter frogs (2 Microhyla spp.) in agricultural land, degraded forest, and intact forest in two study areas, Thailand and Hong Kong. Results Toad populations exhibited higher body condition and female-biased sex ratios in intact forest. Predation of treefrog embryos by flies was lower in intact and degraded forests than in agricultural land. Embryonic survival and larval growth and survival in leaf litter frogs were lower in intact forests than in agricultural land. Results for each study were similar between study areas. Discussion For three of five of these common amphibian species, we documented signals of forest loss and disturbance in their populations. Although these species occur in disturbed habitats, loss of forest cover continues to degrade aspects of their population demography. We urge conservation biologists to consider that populations of species appearing to be common, widespread, and tolerant of human disturbance may be eroding over time.

Nematomorpha from Hong Kong and description of a new species from Malaysia

We report here for the first time horsehair worms (Nematomorpha) from Hong Kong (China). Most specimens belong to the genus Chordodes, and can be assigned to C. bipilus, C. caledoniensis and to C. cf. moutoni. Two specimens have a cuticular pattern resembling the South American species C. peraccae or C. bouvieri, but for Southeast Asia this pattern is new. These two specimens are reported here as Chordodes sp. Additionally, Gordionus chinensis was found. One new species, Acutogordius koljai, is described from Malaysia. It has a characteristically-structured region posterior to the postcloacal crescent which sets it apart from previously described species in this genus.

Does forest extent affect salamander survival? Evidence from a long-term demographic study of a tropical newt

Abstract Forest loss has been associated with reduced survival in many vertebrates, and previous research on amphibians has mostly focused on effects at early life stages. Paramesotriton hongkongensis is a tropical newt that breeds in streams but spends up to 10 months per year in terrestrial habitats. Populations are threatened by habitat degradation and collection for the pet trade, but the cryptic terrestrial lifestyle of this newt has limited our understanding of its population ecology, which inhibits development of a species‐specific conservation plan. We conducted an eight‐year (2007–2014) mark–recapture study on four P. hongkongensis populations in Hong Kong and used these data to evaluate relationships between forest cover, body size, and rainfall on survival and to estimate population sizes. Hong Kong has been subjected to repeated historic territory‐wide deforestation, and thus, we wanted to determine whether there was a link between forest extent as a proxy of habitat quality and newt demography. Annual survival was positively associated with forest cover within core habitat of all populations and negatively related to body size. Mean annual survival (~60%) was similar to that of other stream‐dwelling amphibians, but varied among years and declined substantially in 2012–2013, perhaps due to illegal collection. Despite the link between forest extent and survival, population sizes declined at the most forested site by 40% and increased by 104% and 134% at two others. Forest protection and consequential secondary succession during recent decades in Hong Kong may have been responsible for persistence of P. hongkongensis populations.