Niche Differentiation And Phenotypic Differentiation Among Populations Of Desert Sand Lizard Lineages

The toad-headed lizard（Phrynocephalus przewalskii）is an oviparous agamid lizard that is widely distributed in arid and semiarid areas in North-Northwest China and adjacent Mongolia,thus being ideally suited to the investigation studying genetic and phenotypic differentiation.In this study,I combined genetic（two mitochondrial molecular markers,COI and Cyt b genes）and climatic data to evaluate the relationship between niche evolution and lineage differentiation,and to identify the key factors driving phenotypic differentiation in P.przewalskii.The main results are as follows:Phylogenetic analyses revealed three lineages（A,B and C）.Lineages A and B are bounded by Helanshan and Yinshan Mountains,and Lineage C exists in a basin between Qilianshan and Longshoushan Mountains.There were intermixes of individual haplotypes,suggesting that there is a certain degree of gene flow among the three significantly differentiated lineages.Considering molecular-based phylogeographical lineages,we performed niche equivalency and similarity tests between divergent lineages,and then identidy the key climatic factors driving niche differentiation.Using the“pca＿env”method,I quantified the climate niches of different phylogeographical lineages of P.przewalskii,and then compared the overlap and similarity of niches.Results showed that:climatic niche differentiation between Lineages A and C occurred in the process of genetic divergence between the two lineages.The climatic niche of Lineages A and B share a portion of ecological spaces,and Lineage A can be regarded as a specialized fraction of Lineage B.Mean diurnal range,max temperature of warmest month,and precipitation seasonality have a greater contribution to niche differentiation.Geographic isolation and subsequent niche divergence,together with local adaptation,may have led to genetic differentiation and further lineage sorting in P.przewalskii.P.przewalskii displays strong phenotypic plasticity and significant phenotypic variation among populations.We explored the driving factors of phenotypic variation among 11 populations by comparing genetic(F_ST estimated using neutral marks)and phenotypic(P_ST values for the 14 traits)differentiation.Of the 14 traits,only one（standard metabolic rate,SMR）was found to have a result of P_ST>F_ST,suggesting that the trait is under directional selection;the other 13 had a result of P_ST<F_ST,suggesting that they are all under stabilizing selection.Through principal components analysis（PCA）of climatic variables,then conducted regression analysis between the first principal component（PC1）and SMR,showed that SMR was negatively correlated with PC1,SMR decreased with the increase of diurnal temperature range,isothermality and mean temperature in the coldest season,and increased with the increase of seasonal variation of precipitation.