Influence Of Climate Change On Body Size Of Phrynocephalus Przewalskii

In recent years,global warming has become one of the most widely concerned issues in the world,while the biogeographical rules that were closely related to environmental temperature became one of the hot spots of ecological research again,such as Bergmann's rule and Allen's rule.Studies revealed that temperature was the most important factor that affected the activity?physiology,behavior,survival and fecundity?of ectotherms,and ectotherms highly dependent on external sources of heat to achieve the preferred temperature.In the context of increasing influence of human activities on environment,it was of great scientific significance whether the existing biogeographical rules could be applied to predict phenotypic changes of animals scientifically and reasonably.Therefore,Phrynocephalus przewalskii which widely distributed in the desert regions of northwest China was selected as the research object.The variation of body size of 11 geographic populations of P.przewalskii,as well as the variation of body size of P.przewalskii with climate change in Minqin from 1987 to 2015 were analyzed to test:?1?Whether geographical variation of body size of P.przewalskii conformed to Bergmann's rule and Allen's rule.?2?Whether above rules could be used to predict inter-annual variation of body size of P.przewalskii.In order to test geographical variation rules of body size of P.przewalskii in this study,a total of 467 samples from 11 geographical populations were collected.In addition,438 samples were collected in Minqin to test influence of climate change on body size of P.przewalskii.At the same time,a 5 years length monthly climate data of each sample site were collected from the nearby climatic station?no more than 50 km?from Chinese National Climatic Data Center?CDC?.According to the average temperature,rainfall and sunshine time of annual activity seasons which lasted from April to October,and climate factor for each sample based on its age were calculated in order to analyze influence of climatic factor on body size of P.przewalskii.7 morphological data of each sample were measured by caliper,the sex of each individual was identified,and skeletochronology method was applied to analyze the age.The principal component analysis of the morphological data was carried out with reference to the literature,the preserved principal components PC_BS and PC_AS were used as indicators of overall body size,limbs and tails respectively.We tested the correlation of temperature with two measurements of body size(log₁₀SVL and PC_BS)for males and females to investigate the adherence of P.przewalskii to Bergmann's rule.Similarly,the correlation of temperature with limbs and tails?PC_AS?was conducted to test Allen's rule.SPSS 20.0 was used for two-way analysis of variance?ANOVA?and GLMM analysis to examine geographical variation of body size of P.przewalskii and related geographical variation rules.The results of geographical variation of body size indicated that there was a significant geographical variation in body size?PC_BS?,limbs and tails?PC_AS?of geographic populations of P.przewalskii.The body size of P.przewalskii increased with increasing temperature which following the contrary to Bergmann's rule.The limbs and tails of females positively correlated with temperature which following the Allen's rule but males had no concern with Allen's rule.GLMM indicated that body size of geographic populations of P.przewalskii was only affected by age,while limbs and tails significantly and positively correlated with temperature,but significantly and negatively correlated with age,rainfall and sunshine time.The results of influence of climate change on body size indicated that there was a significant inter-annual variation in body size?PC_BS?,and there were significant variation between sexes and among years in limbs and tails?PC_AS?of P.przewalskii in Minqin.The body size,limbs and tails of females increased with increasing temperature which following the contrary to Bergmann's rule,but following the Allen's rule.The males were completely opposite to that of females,their body size,limbs and tails significantly and negatively correlated with temperature.GLMM indicated that body size of P.przewalskii in Minqin significantly and positively correlated with age,but significantly and negatively correlated with rainfall and sunshine time.The limbs and tails significantly and positively correlated with age,but significantly and negatively correlated with rainfall.The variation of body size of geographic populations of P.przewalskii contrary to the Bergmann's rule,and this trend was caused by plasticity of growth rate that determined by temperature and food available.The variation of limbs and tails of females following the Allen's rule,relative longer limbs and tails in hot desert were advantage in maintaining optimal body temperature.While males had no concern with Allen's rule,relative longer limbs and tails in a cold environment associated with sexual selection.The age structure was an important reason of variation of body size of P.przewalskii,therefore we advised to consider age and use a general body size?PC_BS?in rule testing.Considering the situation was confusion when geographical variation involved the latitude and altitude simultaneously,it recommended use temperature directly instead of latitude or altitude in rule testing.Global warming resulted in rising temperature and rainfall,the body size,limbs and tails of P.przewalskii varied differently for females and males in Minqin.The body size of females increased and ascribed to fecundity selection which contrary to Bergmann's rule,whereas the males reduced and ascribed to sexual selection which following the Bergmann's rule.The variation of limbs and tails of females following the Allen's rule and due to the thermal advantage,but that of males following the contrary to Allen's rule and ascribed to sexual selection.The age,growth rate and distribution of substance and energy used for growth were the reasons for different variation rules in geographical variation and climate change between two sexes.Males of P.przewalskii varied differently in geographical variation and climate change,it was generally believed that geographic variation of body size of different population was the result of long-term effects of different environmental factors in the habitat,perhaps phenotypic plasticity caused by different environmental factors,or the combination of two factors.It was surmised that inter-annual variation of body size of P.przewalskii in Minqin originated from proximal factors,which may be related to phenotypic plasticity under immediate influence of environmental factors.In conclusion,in the context of global warming,this study believed that Bergmann's rule and Allen's rule only suitable for predicting inter-annual variation of body size of P.przewalskii for females.