Effects Of Geographical Distribution Pattern And Environmental Factors On Morphological Variation Of Asiatic Toad(Bufo Gargarizans)

Morphology of Species appears from the stimulation of the external environment originally.The same species may produce isolation differentiation or local adaptation between different geographical populations under various selection pressures,resulting in the appearance of morphological variation.In systematic geography,most of the researches using phylogenetic analysis which was based on mtDNA and microsatellite markers to explained morphological variation.However,only a few researches focus on explaining morphological variation from the perspective of macroecology,especially the effect of geographical distribution pattern and environmental factors on morphological variation.In this paper,we selected the Asiatic toad(Bufo gargarizans)as our research object which is widely distributed in China.Forty geographic populations were collected within its distribution region,in total 400 samples,of which 226 are males and 174 are females.The morphological indexes of each sample,including 4 basic morphological variables and 3 combined morphological variables(Mass'\L1'\L2'\L3'and L4\L\LH)were measured.In view of the fact that amphibians are morphologically dimorphic,all geographic populations were divided into 38 male geographical populations and 35 female geographical populations according to gender and distribution(there are whole female or male in partial sampling sites).Based on four basic morphological variables,all male and female geographical populations were divided into three groups by hierarchical clustering:Male₁\Male₂\Male₃\Female_l\Female₂\and Female₃.The clustering results were verified by discriminant analysis and PCA.Based on the clustering results,the morphological variation among groups were obtained by using univariate analysis and pairwise comparison to basic morphological variables and combinatorial morphological variables.Based on the results of variance analysis,explore the geographical distribution pattern?habitat types and environmental factors in each group,try to from the view of ecology with the geographical distribution pattern?habitat types?environmental factors and niche distribution model to explain morphological variation among each group.At the same time,tried to provide some suggestions to Local adaptation theory with the result of this study.Combined with the analysis results of morphological variation of each group,and the exploration of geographical distribution,habitat types and environmental factors in each group,the obtained results can be summarized as the following:(1)The morphological variation mainly existed between the groups of Male₃?Female₃ and other four groups,the differences included body mass,total length of hind limb,length of tibia,the ability of movement and jumping.(2)In terms of the geographical distribution,Male₃ and Female₃ groups located in Hengduan mountains,its geographical isolation,unique animal fauna characteristics and single geographic distribution pattern might be the reasons for the presence of morphological variation amomg different groups.(3)In terms of habitat types,the habit type of Male₃ and Female₃ groups were relatively single,the main vegetation types were coniferous forest and alpine meadow,the main vegetation zones were subtropical evergreen broad-leaved forest,and subtropical mountain cold and warm coniferous forest,and the microhabitat was alpine meadow puddles or streams.It was speculated that the single habitat type(including macrohabitat and microhabitat)might be one of the reasons for the presence of morphological variation among different groups.(4)Of the environmental factors anlayzed,the annual mean temperature(AT)was significantly correlated with morphological variables,and it could explain and predict the sources and trends of morphological variation among different groups to some extent.It can be considered that the annual mean temperature(AT)was one of the main factors of morphological variation among different groups.(5)Based on the geographical distribution pattern and environmental factors,the present potential distribution region(niche distribution)of Bufo gargarizans was predicted.The results showed that Male₃ and Female₃ had less niche than other groups.Taken together,according to the exploration results of geographical distribution and habitat types among diffrent groups,it could be speculated that the differences in geographical distribution and habitat type might be the reasons for the presence of the morphological variation among different groups.Through the exploration of environmental factors among groups,it could be concluded that the difference of annual average temperature(AT)was one of the reasons for the morphological variation among different groups.Combined with geographical distribution pattern and environmental factors,it could be concluded that the difference of niche distribution among different groups might be one of the reasons for morphological variation.Based on the results of this study,it was assumed that the morphology of different geographical populations of appeared local adaptation under the pressure of different geographical environment.