Thermal dependence of feeding performance and resting metabolic expenditure in different altitudinal populations of toad-headed lizards.

Inter-population variations in growth rate can result from independent or interactive effects of genetic and environmental factors, and be induced by some physiological differences as well. Toad-headed lizards (Phrynocephalus vlangalii) from a higher-elevation population were shown to have a higher growth rate than those from a lower-elevation population. The physiological basis of growth rate variation in this species is not well understood. Here, we investigated the feeding performance and resting metabolic rate (RMR) of lower- and higher-elevation individuals at different test ambient temperatures to evaluate the role of differences in energy intake, assimilation efficiency and metabolic expenditure on growth rate variations. Within the range of 25-35 °C, lizard RMR increased with increasing test ambient temperature, but food intake, apparent digestive coefficient (ADC, food energy minus faecal energy divided by food energy), and assimilation efficiency (AE, food energy minus faecal and urinary energy divided by food energy) were less thermally sensitive in both populations. Higher-elevation lizards tended to eat more food and have a lower RMR than lower-elevation ones, despite the lack of differences in ADC and AE. Our result showed that more energy intake and reduced maintenance cost may be associated with the higher growth rate of higher-elevation lizards. Accordingly, inter-population differences in energy acquisition and expenditure could act as potential sources for geographic variation in growth rate.

Different mechanisms lead to convergence of reproductive strategies in two lacertid lizards (Takydromus wolteri and Eremias argus).

Life history traits may vary within and among species. Rarely, however, are both variations examined concurrently to identify the life history adaptation. We found that female body size, offspring number and size, and incubation period showed convergent evolution in two lacertid lizards (Takydromus wolteri and Eremias argus) that occur sympatrically in high-latitude and low-latitude localities. Females from the high-latitude population were larger and produced larger clutches than those from the low-latitude population. In both species, the incubation period was shorter for the high-latitude population than for the low-latitude population. However, the physiological mechanism underlying the shorter incubation period differed between the species. These results suggest that: (1) sympatric lizards may adopt similar reproductive strategies in response to their common environments, and (2) embryonic development of the two species follows different pathways for adaptation to low temperatures. This study highlights the importance of understanding the adaptive evolution of life history in response to environmental changes at the embryonic life stages.

Latitudinal Variation in the Pattern of Temperature-Dependent Sex Determination in the Japanese Gecko, Gekko japonicus.

Identifying latitudinal variation in the pattern of temperature-dependent sex determination (TSD) may provide insight into the evolution of sex determining system in vertebrates, but such studies remain limited. Here, we quantified TSD patterns of three geographically separated populations of the Japanese gecko (Gekko japonicus) along the latitudinal cline of China. We incubated gecko eggs from the three populations at constant temperatures of 24, 26, 28, 30, and 32 °C to quantify the TSD pattern. Our study demonstrated that G. japonicus exhibited a FMF pattern of TSD, with the low and high incubation temperatures yielding significantly female-biased hatchlings, and the medium temperatures producing male-biased hatchlings. More interestingly, we found latitudinal variations in the TSD pattern in terms of pivotal temperatures (Tpivs), transitional range of temperatures (TRT), and the sex ratios at the medium temperatures. The Tpivs for the low-latitude population were lower than those for the two high-latitude populations. The low-latitude population has a narrower FM TRT, but a wider MF TRT. The sex ratio is almost 50:50 for the low-latitude population when eggs were incubated from 26 to 30 °C. Conversely, the sex ratio is male-biased for the two high-latitude populations at 28 or 30 °C. Therefore, G. japonicus may provide an interesting system to explore the evolution of TSD in reptiles given the diversity of TSD patterns among populations.

Comparative population genetics and phylogeography of two lacertid lizards (Eremias argus and E. brenchleyi) from China.

Eremias argus and Eremias brenchleyi are lacertid lizards that are sympatric throughout the distribution of E. brenchleyi. We sequenced partial mitochondrial DNA from cytochrome (cyt) b gene for 106 individuals of E. argus from nine localities, and for 45 individuals of E. brenchleyi from five localities, in central and northern parts of North China. We determined 53 cyt b haplotypes from the E. argus samples, and 27 cyt b haplotypes from the E. brenchleyi samples. Only E. brenchleyi had followed a stepping-stone model of dispersal. Partitioned Bayesian phylogenetic analysis reveals that E. argus and E. brenchleyi are reciprocally monophyletic, and the divergence time between the two species was dated to about 4.1±1.2 million years ago. Geographical structuring of haplotypes is more significant in E. brenchleyi than in E. argus. Haplotypes of E. brenchleyi could be divided into four groups by the Yellow River and Taihang Mountains. Within-population genetic diversity indices are correlated neither with latitude nor with longitude. We calculated significant among-population structure for both species (E. argus: Φ(ST)=0.608, P<0.001; E. brenchleyi: Φ(ST)=0.925, P<0.001). Eremias brenchleyi has four independent management units, while E. argus has a more homogeneous genetic structure across its range. Our data show that: (1) the pattern seen in North American and European species that southern populations have higher genetic diversity as consequence of post-glaciation dispersal is absent in the two Chinese lizards; (2) the Yellow River and Taihang Mountains may have acted as important barriers to gene flow only in E. brenchleyi; and (3) genetic structure differs between the two lizards that differ in habitat preference and dispersal ability.

Income breeding and temperature-induced plasticity in reproductive traits in lizards.

We used the northern grass lizard Takydromus septentrionalis as a model animal to examine the energy allocation strategy and whether body temperature can affect maternal reproductive traits in lizards. We maintained adult females collected from the field soon after winter dormancy under three thermal conditions (24.0+/-1.0 degrees C, 28.0+/-1.0 degrees C and 32.0+/-1.0 degrees C) throughout the subsequent reproductive season, and then recorded their energy intake, digestive efficiency, body size and mass changes, and reproductive parameters. Manipulation of body temperature in reproducing females affected energy intake and several maternal reproductive characteristics. Females allocated energy to reproduction following the fulfillment of energetic requirements for metabolism and growth. The reduced energy availability for reproduction constrained females at low or high body temperatures to produce fewer and smaller eggs per season but had no role in influencing the number of eggs produced in single reproductive bouts. Females used currently acquired energy to fuel reproduction, and this strategy did not shift seasonally from the first to subsequent clutches. Our study supports the idea that the use of currently acquired energy for reproduction may be more widespread in ectotherms than thought before, and shows for the first time that egg size is thermally plastic in T. septentrionalis, where eggs produced in single reproductive bouts are believed to be well optimized for size.

Evolution of reptilian viviparity: a test of the maternal manipulation hypothesis in a temperate snake, Gloydius brevicaudus (Viperidae).

We kept 48 gravid short-tailed pit vipers (Gloydius brevicaudus) under four laboratory thermal conditions during gestation and collected 10 females from the field soon before they gave birth to test whether Shine's (1995) maternal manipulation hypothesis applies to temperate reptiles. Females thermoregulated more precisely but did not shift their selected body temperatures during pregnancy, with females at high body temperatures giving birth early in the breeding season. The lowest (22 degrees C) and highest (32 degrees C) temperature treatments Increased maternal mortality and resulted in production of offspring with smaller body dimensions. More deformed offspring were produced at 32 degrees C, and more poorly performing offspring were produced at 22 degrees C. In the field, air temperatures lower than 22 degrees C and higher than 32 degrees C accounted for about 9% and 33% of total temperature readings, respectively. However, offspring produced by field-caught females did not differ from those produced by laboratory-kept females with body temperatures optimal for embryonic development in nearly all traits examined. This suggests that in nature, gravid females avoid exposure of their embryos to temperature extremes through thermoregulation. Our study validates the key prediction of the maternal manipulation hypothesis that maternal thermoregulation should enhance fitness-related offspring traits, and demonstrates that viviparity evolves in temperate reptiles because internal development shields offspring from temperature extremes.

Complete mitochondrial genome of Papilio syfanius (Lepidoptera: Papilionidae).

The complete mitochondrial genome (mitogenome) of the swallowtail butterfly Papilio syfanius has been completed. It is 15,359 bp, and contains the typical complement of 13 protein-coding (PCGs), 22 transfer RNA (tRNA) and 2 ribosomal RNA (rRNA) genes. Two A + T-rich regions are included in this mitogenome. The nucleotide composition is very similar to other insects, showing a high bias towards A + T, especially the control region (92.8%). Gene order in P. syfanius mitogenome is basically identical to that of the inferred ancestral insect genome, with the exception of translocations of trnM, which is common in genus Papilio.