Geographic Variations Of Morphology,Maintenance Cost And Reproductive Traits In Takydromus Septentrionalis

We studied patterns of evolutionary strategies of life history in squamata reptiles using the northern grass lizard(Takydromus septentrionalis)as an animal model in this dissertation.Our studies mainly focus on more than 20 separate populations with different geographic locations on mainland and island of China.For each population,we determined morphological characteristics,reproductive life histories and maintenance cost.Moreover,we paid particular attention to setting up two new hypotheses and testing them with our results.The two hypotheses are(1)the sizes of the lizards at maturity from higher latitude populations are larger than those of the lizards from lower latitude populations;(2)the maintenance cost of the lizrads from higher latitude populations are lager than those of the lizards from the lower latitude population;(3)if resources unlimited during breeding season,there is no relationship between maintenance cost and reproductive effort in the subsequenct reproductive events.The main results and conclusions are as follows:Since the curvilinear relationship between metabolic rate and body size has been adopted,it may be brought a new horizon for the study of the scaling relationship.We re-examined a dataset for 166 species of reptiles that the relationship between SMR and body mass or temperature is well described by a power function.Aim(1)to identify statistical best scaling models,and(2)thereby to prove whether correcting for differences in temperature and species' shared evolutionary history improves models and their biological interpretability.There was a convex curvature on a logarithmic scale between body mass and SMR,and with a power law accounting for temperature,and all best models corrected by phylogeny in reptiles.The beast model is a curvature scaling associated with phylogenetic analyses for reptiles.It indicated the curvilinear scaling is a universal law for reptiles.And the slope and activation energy of the suborder level beyond the excepted range by MTE theory,the metabolic scaling will in the excepted range by MTE for the order level.There was a strong phylogenetic signal,indicating that phylogenetic relationships associated with the SMR.We used data reported for 129 species of squamates to test the hypothesis that selection favors the evolution of reduced maintenance costs in taxa that invest more energy in reproduction or with an expensive mode of reproduction.We found that:1)standard metabolic rate(SMR),body mass,temperature-corrected SMR and mass-corrected SMR presented a significant phylogenetic signal;and 2)maintenance costs were lower in snakes than in lizards,and the costs were lower in viviparous species than in oviparous species.Because reproductive investment per episode is higher in snakes than in lizards and because viviparity is an expensive mode of reproduction,our results validate the hypothesis tested.Our study is the first to demonstrate that evolutionary transitions in body plan(from lizard-to snake-like body form)and reproductive mode(from oviparity to viviparity)alters maintenance metabolism of the organisms involved.Southern China is one range of high levels of species diversity in world.The goal was to investigate historical demography and the influence of pleistocene climate fluctuations on genetic diversity and the evolutionary history of Takydromus septentrionalis across the hilly country of southeastern China.Using two mitochondrial DNA genes(Cyt b and COI)and two nuclear DNA genes(RAG 1 and PDC)from 513 individuals.To do that,we reestablished the maximum likelihood(ML)and Bayesian phylogenetic tree by the concatenated fragment of four genes.Phylogenetic analyses and SAMOVA analyses revealed that T.septentrionalis comprises two distinct clades divided into five subclades.The results of AMOVA suggested strong population genetic structure based on mtDNA.Demographic analyses revealed the expansion events appearing 0.075 Ma(E1 subclade),0.028 Ma(E3)and 0.022 Ma(W2),but it still revealed the decline event appearing 0.025 Ma(E2).The basic phylogeographical structure of T.septentrionalis was established by 0.78 Ma.By contrast,ENM indicated that species' distributions remained fairly stable over the last glacial/post-glacial cycle.Our results indicated that T.septentrionalis experienced fragmentation of wide-ranging ancestral populations.Climatic fluctuations during the Pleistocene,as result of glacial oscillations and the unique East Asian monsoon system inducing the uplift of the Tibetan Plateau and the Himalayas,was likely to be the primary contributor to influence the population differentiation and species distributions in this species.Although there was no sexual difference on snout-vent length of the adult lizard,sexual dimorphisms were found on head sizes,arm length and leg length,which benefit to males.which benefit to females.The morphologic characteristics of the adult lizard differed among geographic populations.Differences on head sizes,arm length,leg length and snout-vent length contributed to the most of geographic variation on morphology.Snout-vent length of the lizards decreased with the decreasing of latitude,whereas,head sizes,arm length and leg length,of the lizards from high latitude population were higher than those from lower latitude populations.Clutch size,clutch mass and relative clutch mass of the first clutch were significantly higher than those of the subsequent clutch.But,there were no inter-clutch differences on egg mean size.Moreover,for the first clutch,clutch size and clutch mass were positively correlated with snout-vent length of females.We did identify the phylogenetic signals in clutch size,clutch mass and egg mean mass by PGLS.Clutch size and relative clutch mass of lower latitude populations were larger than those of higher latitude populations,whereas egg sizes of lower latitude populations were smaller than those of higher latitude populations.These geographic variations in clutch size and clutch mass not only caused by female size but also by thermal variations.However.egg size is determined ultimately by natural selection.The maintenance cost of the lizard differed among geographic populations during non-breeding season.The whole maintenance cost(MC)increased with temperature,body mass or latitude.But the mass-specific MC was differing with the whole MC.The whole MC decreased with the reproductive effort increased during the subsequent clutch.