Group Living on Trees Does Not Elevate Inbreeding Risk in Shedao Pit Vipers Gloydius shedaoensis

Group living has increasingly been emphasized due to its potential consequence on inbreeding, nevertheless, the relationship between group living and inbreeding risk is largely unknown. The endangered snake species, Shedao pit viper(Gloydius shedaoensis) inhabiting mostly on Shedao Island(meaning "snake island" in Chinese), provides an excellent model system for research on group living and inbreeding risk. Small island area, high population density and extreme seasonal foraging opportunity prompt many individuals to live on the same tree, which likely increase the potential mating among relatives. To confirm this probability, we used genotypes from 13 microsatellites DNA markers and examined the genetic relationships between pair of individuals lived on the same tree. The results showed that snakes on the same tree did not show closer relationships compared with individuals from different trees. The group constructions based on scenarios of parental-offspring, full-sibling, half-sibling as well as cousin were not consistent with tree-based group living. In addition, we did not find significant correlation between pair of individual genetic distance and geographic distance going beyond trees, suggesting group living on trees might not elevate inbreeding risk.

Ring Clinal Variation in Morphology of the Green Odorous Frog(Odorrana margaretae)

The green odorous frog(Odorrana margaretae)has an interesting ring-shaped divergence pattern around the Sichuan Basin and documenting its morphological variations is essential in understanding its evolutionary history.Using curvilinear models,we detected significant geographical clinal variations in morphological traits,particularly sizes,of female O.margaretae.Males had significantly smaller sizes than females,and also had smaller variation ranges than females.One major trend of morphological variations was clinal:populations from the west tended to have a larger size with wider head and longer posterior limbs than populations from the east.Species history,with an early extended isolation and two subsequent secondary contacts,may explain most of the geographical clinal variations of O.margaretae.Bioclimatic factors may also contribute in explaining the variance of morphology.

Low diversity,little genetic structure but no inbreeding in a high-density island endemic pit-viper Gloydius shedaoensis

Island species and their ecosystems play an important role in global biodiversity preservation,and many vulnerable island species are conservation priorities.Although insular habitat likely facilitates the species diversification process,it may also aggravate the fragility of these species with high risk of inbreeding.The Shedao pit-viper Gloydius shedaoensis is an island endemic species with an extremely high population density,which has been categorized as vulnerable in the IUCN(International Union for the Conservation of Nature and Natural Resources)Red List.We collected 13,148 SNP(Single Nucleotide Polymorphism)from across its genome and examined its genetic diversity and demographic history.The Shedao pit-viper has a low genetic diversity but shows no sign of inbreeding.Furthermore,population genetic structure analysis,including the neighbor-joining tree,principal coordinate analysis,clustering,and spatial autocorrelation,revealed a general lack of spatial structure.Only the isolation by distance residues suggested a weak patchiness.Overall,the population is nearly panmictic and gene flow is evenly distributed across the island.A large number of individuals,small size of the island,and the lack of population structure likely all contribute to the lack of inbreeding in this species.We also detected signs of male-biased dispersal,which likely is another inbreeding avoidance strategy.Historical demographic analysis suggested that the historical population size and distribution of the species are much larger than their current ones.The multiple transgressive–regressive events since the Late Pleistocene are likely the main cause of the population size changes.Taken together,our results provide a basic scientific foundation for the conservation of this interesting and important species.