The Role Of Niche Evolution On Lineage Diversification In Two Agamid Lizards

There has been a controversy over whether niches are conserved or divergent during lineage diversification.To better understand these processes it is critical to study niche conservatism during initial stages of lineage diversification.Here,we combined ecological niche modelling and genetic information,using two agamid lizards(Leiolepis reevesii and Calotes versicolor)as model systems,to assess how the ecological niche influences lineage diversification.Using molecular-based phylogeographical lineages we performed ecological niche modelling analyses to investigate the differences in ecological niche(estimated by measuring Schoener's D and Hellinger's I)and in geographical distribution(estimated by measuring geographical overlap and inter-predictability)between divergent lineages in each species.We performed respectively two tests(niche identity test and background test)to measure Schoener's D and Hellinger's I.The niche identity test and background test showed that the two lineages in L.reevesii share environmental niche space whereas the two lineages in C.versicolor differ in environmental niche space.The value of the overlap index and inter-predictability indicate that the predicted distribution of Lineage A contains Lineage B for both species.Lineage A of L.reevesii was predicted to have a wider distribution including some regions along the coast of Beibu Gulf,Leizhou Peninsula,and Hainan and Vietanm,whereas Lineage B of L.reevesii was restricted to the south of Wuzhishan and Yinggeling mountain ranges along the coastal regions.Lineage A of C.versicolor was predicted to have a wider distribution including the whole coastal area,whereas Lineage B of C.versicolor was restricted to the central and southern regions of Hainan province.Our results support the hypothesis of allopatric speciation resulting from the presence of niche spatial differences,where genetic differentiation occurred accompanied by niche divergence.Our results also indicate that environmental specialization has a key role in driving genetic and ecological differentiation in L.reevesii and C.versicolor.Ecological niche modelling can contribute and validate evolutionary analyses performed by combining ecological niche modeling and genetic information.