Climatic Correlates Of Genetics,morphology And Distribution And The Possibility Of Hybridization In Lizards Of The Genus Takydromus (Lacertidae)

Due to climate change and human activities,the distribution of organisms has dramatically changed.So the previously geographically isolated species get a second chance to contact again,and the physical reproductive isolation has been broken.When reproductive isolation is incomplete,it will result in existence of mixed areas between two adjacent species for a long time,which makes it possible to cross to form new species.Various mathematical models have proved that selective pressure may induce genetic differences and species formation,but just under very specific conditions or under very extreme combinations of parameters.So the genetic differences is not only factor to effect the the ability of species to adapt to new environments,the factors of climatic may induce the rapid morphology differentiation.The southern grass lizard(Takydromus sexlineatus)and the northern grass lizard(Takydromus septentrionalis)belong to the same genus.They have similar morphology and habitat,and some distribution areas of them are overlapped.Therefore,so we used the southern grass lizard and northern grass lizard as research objects,combines indoor experiments and species distribution model,to study whether populations separation and second contacts will lead to new species formation.We chose the northern grass lizard as the research object,which has a wide range of distribution and large climate differences in the distribution area,to study the impact of climate differences on the population differentiation.The results showed that there were differences of the microclimate in the species distribution area,and these differences will lead to irregular alteration of the rate of variation in genes and morphology among different populations,and lead to the differentiation of genes and morphology among populations.Moreover,precipitation climate factors have important effects on genes variation and morphology plasticity.The result of mating experiment between female individuals of Lishui population and male individuals of native and other 4 populations(Liuheng,Xiushan,Chang'an and Chuzhou)showed that the frequency of female preference was different among different populations,and geographical distance,genetic differentiation,environmental dissimilarity and morphological difference had significant effects on female preference in the northern grass Lizards.Morphological difference played a major role in female preference,followed by genetic differentiation.Morphological differences directly affected mating selection,the male with larger head length and width had the higher probability of mating.In addition,the genetic differentiation will lead to morphological differences.Geographical distance plays a key role in the evolution of female preference,and morphological differentiation is a direct factor affecting spouse preference differentiation.In the study of the hybrid speciation,we used four gene markers(2 mitochondrial genes:Cytb and COX1;2 nuclear genes: RAG1 and PDC)to reconstruct phylogenetic trees of the two species,which sympatric exists between their distribution area.We found that there was genes introgression among southern and northern grass lizards from Guilin and Daqiao populations.We also found that genes introgression also exists in other populations in Zhejiang region,so we speculated that there may be the sympatric area of northern and southern grass lizards in this region.In addition,146 bisexual mating events were observed under laboratory conditions.181 eggs were laid,including 30 fertilized eggs with 25 successfully hatched.Molecular identification showed that the hybrid offsprings were polyploidy,which suggested that the southern grass lizard and the northern grass lizard may form new species through hybridization.In the mating selecting process,the size of male individuals will play a crucial role.The larger male individuals are more likely to obtain mating chance,but the larger size will cause female death.This indicates that there may be a "safe body shape variance" in mating.The integrated prediction model was used to predict the distribution of the southern grass lizard and the northern grass lizard in China.The results showed that there were similar distribution areas of the southern and northern grass lizards near the junction of Jiangxi,Hunan,Fujian,Guangxi and Guangdong provinces.In addition,linear fitting of morphological data and latitude for different populations of the southern grass lizard and the northern grass lizard showed that the body shapes of the northern grass lizard and the southern grass lizard in the same region conformed to the "safe body shape variance" individuals.This indicates that there is mating phenomenon in the wild and the possibility of producing hybrid offspring smoothly.Based on the information of the distribution sites of the southern grass lizard and the northern grass lizard,the future distribution areas of grass lizards were predicted by integrating the climate data in 2050 and 2070.The results showed that the climate factor Bio6(min temperature of coldest month)is the key factor to determine the distribution of the grass lizard,which makes the distribution area of the grass lizard migrate northward because of global warming.Additionally,the distribution area of the northern grass lizard will decline,while the distribution area of the southern grass lizard will expand.And the same distribution area of them will expand,which will further increase the possibility of gene penetration and hybridization between the northern and southern grass lizards.Similarly,we analyzed the exogenous and homologous distributions of seven species of the grass lizards.The results showed that the distribution areas of most grass lizards will expand.The southern grass lizards and Taiwan grass lizards(Takydromus formosanus)living in low latitudes expanding to high latitudes.The distribution areas of Heilongjiang grass lizards(Takydromus amurensis)living in high latitudes show signs of expanding to the west.The size and location of the same distribution area of different species will also change.Species with in the narrow distribution area will decline or even extinct because of unsuitable for the living environment.Species in the wide distribution area will be fragmented,resulting in geographical isolation,which is conducive to species differentiation and lead to the formation of new species.The global warming may threaten or even cause extinction of tropical and subtropical populations,but it is beneficial to the survival and expansion of the whole species,and the distribution area expand to a large extent.While it is unfavorable to the species in temperate regions,making the distribution area decline in the south and north,and the distribution of the whole species decreased.The expanding of same distribution areas will promote the formation of new species.However,the genetic infiltration will not lead to the fusion of the distribution area of the northern grass lizard,they will continue to maintain the different distribution.Seven kinds of grass lizards are mainly distributed in the southern part of China.There are many species in the same region,and there is the possibility for gene infiltration and hybridization.In the future,the homologous distribution areas of these lizards will change due to the dynamic changes of species distribution,but the whole trend will be conducive to the formation of new species.