Geographic variation in life-history characteristics of amphibians: a review

1. This review examines the intraspecific patterns and differences in life-history traits of amphibian populations living at different altitudes and latitudes. Specifically we examined differences in development and growth (physiological constraints) and reproductive ecology (plasticity in reproductive traits). 2. Research published to date suggests that amphibian populations at higher altitudes and latitudes tend to: (a) have shorter activity periods, and hence shorter breeding seasons; (b) have longer larval periods; (c) are larger at all larval stages including metamorphosis; (d) are larger as adults; (e) reach reproductive maturity at older ages; (f) produce fewer clutches per year; (g) produce larger clutches absolutely and smaller clutches relative to body size; and (h) produce larger eggs. 3. These generalizations must be viewed with caution, due first to the small number of papers supporting them, and secondly to the inconsistent results published to date. 4. The implications of the intraspecific geographical variation in life history traits for general amphibian biology, amphibian population declines and conservation are discussed.Griffith Sciences, Griffith School of EnvironmentNo Full Tex

Genetic signals of high-altitude adaptation in amphibians : A comparative transcriptome analysis

Background: High-altitude adaptation provides an excellent system for studying how organisms cope with multiple environmental stressors and interacting genetic modifications. To explore the genetic basis of high-altitude adaptation in poikilothermic animals, we acquired transcriptome sequences from a high-altitude population and a low-altitude population of the Asiatic toad (Bufo gargarizans). Transcriptome data from another high-altitude amphibian, Rana kukunoris and its low-altitude relative R. chensiensis, which are from a previous study, were also incorporated into our comparative analysis. Results: More than 40,000 transcripts were obtained from each transcriptome, and 5107 one-to-one orthologs were identified among the four taxa for comparative analysis. A total of 29 (Bufo) and 33 (Rana) putative positively selected genes were identified for the two high-altitude species, which were mainly concentrated in nutrient metabolism related functions. Using SNP-tagging and FST outlier analysis, we further tested 89 other nutrient metabolism related genes for signatures of natural selection, and found that two genes, CAPN2 and ITPR1, were likely under balancing selection. We did not detect any positively selected genes associated with response to hypoxia. Conclusions: Amphibians clearly employ different genetic mechanisms for high-altitude adaptation compared to endotherms. Modifications of genes associated with nutrient metabolism feature prominently while genes related to hypoxia tolerance appear to be insignificant. Poikilotherms represent the majority of animal diversity, and we hope that our results will provide useful directions for future studies of amphibians as well as other poikilotherms