【作者】 李佳琦；

【导师】 刘迺发；

【作者基本信息】 兰州大学 ， 动物学， 2013， 博士

【摘要】 爬行动物(特别是蜥蜴和蛇)之所以受到生态学家的青睐,是因为作为外温动物,它们高度依赖周围环境的气候条件,因此表现出许多环境诱导的生活史特征变异。爬行动物的生活史特征在种间以及种内不同种群间都存在差异,而海拔及其相关的环境因子是造成爬行动物生活史差异的主要因素。青藏高原地区地理环境独特,因此不同地区的自然环境存在较大的差异。这种独特的地理环境造就了青藏高原上生物分布及其特征的多样性,为进化生物学研究提供了理想的场地。本文以青藏高原上不同海拔分布的贵德沙蜥(Phrynocephalus putjatia)、青海沙蜥(Phrynocephalus vlangalii)、贵南沙蜥(Phrynocephalus guinanensis)和红尾沙蜥(Phrynocephalus erythrurus)等四种沙蜥的七个地理种群为研究对象,从形态学,种群生态学,繁殖生态学和分子生态学等方面综合研究不同海拔上高原沙蜥种间和种内的生活史特征的差异及其进化：探索不同海拔地区生活史特征变化的规律,验证这些变化趋势是否符合各种已知的生物地理学规律,并且进一步探讨不同海拔地区生活史特征差异形成的原因。贵德沙蜥、青海沙蜥、贵南沙蜥和红尾沙蜥这四种高原沙蜥中普遍存在两性形态特征的异形。其中雌性拥有较大的体长和腹长,而雄性具有较大的尾长、头部和四肢等特征。雄性蜥蜴的相对头部大小(头长和头宽)在幼体和成体之间没有显著差异,而成体雌性的相对头部特征小于幼体,表明成年雌性蜥蜴的头部特征的发育在成年后相对减慢。高原沙蜥两性异形可能是受到性选择和生育力选择两种压力共同作用的结果,也是蜥蜴体内各方面权衡后能量分配的差异导致的。种间比较时,四种沙蜥成体体长随海拔的升高而减小,这不符合Bergmann规律。高海拔物种选择较小的体型是对环境的适应性进化并且受到系统发生的影响。低温缺氧条件下,蜥蜴的体温维持和能量代谢受到影响,分配给生长的能量相对较少,这些压力都会使蜥蜴向小体型方向进化。尾长和头部特征随海拔的升高而减小,这符合Allen规律。较小的附肢特征具有较小的表面积,有利于蜥蜴充分利用环境温度,减少能量消耗保持身体相对恒定的温度。高原沙蜥种间和种群间雌雄体长的两性异形变化不符合Rensch规律。种内比较时,青海沙蜥和贵德沙蜥种内不同种群间,体长随海拔的升高而增大,符合Bergmann规律。这可能是不同地区的沙蜥出生体长和性成熟年龄差异引起的,主要是受到环境的影响。高海拔地区的贵德沙蜥和青海沙蜥与低海拔地区相比具有更小的尾长、头部特征和附肢长度,这符合Allen规律。青海沙蜥高海拔种群(玛多种群,MD)的雌性蜥蜴具有更大的相对腹长,而贵德沙蜥低海拔种群(贵德种群,GD)的雌性蜥蜴具有更大的相对腹长,种群间腹长的差异可能对后代大小产生一定的影响。而雄性蜥蜴的腹长在不同海拔之间没有显著差异。青藏高原沙蜥尾椎骨数目在雌雄之间没有显著差异,同时尾椎骨数目与体长没有显著相关性。另外,尾椎骨数目会随海拔的升高而减少,但是这种现象不能通过Jordan规律来解释。尾椎的差异可能受到遗传和系统发生的影响,温度也可能对在尾椎骨数目的变化有一定的影响。骨龄切片结果显示,青藏高原四种沙蜥参与繁殖个体的最大年龄为6龄,即度过6个冬眠期。采用Von Bertalanffy模型拟合体长的生长曲线,结果显示四种沙蜥雌雄体长在2龄之前没有显著差异,从3龄(性成熟)后雌雄体长开始出现显著差异。不同地理种群之间的生长率也存在差异。这些差异可能与蜥蜴生长和繁殖过程中能量分配的差异有关。青海沙蜥和贵德沙蜥低海拔种群性成熟年龄为2龄,高海拔地区为3龄。贵南沙蜥和红尾沙蜥的性成熟年龄为3龄。另外,四种沙蜥中雌性繁殖的优势年龄为3-4龄,但是青海沙蜥和贵德沙蜥低海拔种群3龄个体繁殖相对较多,而高海拔地区4龄个体繁殖相对较多。这些差异可能与不同海拔的温度环境有关。四种沙蜥实验室内产仔时间在6月29日到9月7日之间,随着海拔的升高产仔时间会推迟。种内高海拔种群繁殖雌性的平均体长和最小繁殖体长(性成熟体长)都大于低海拔种群。新生后代性比没有显著的性别偏移,同一种群不同年份之间也没有显著差异。种间和种内不同种群之间的繁殖生活史特征存在显著差异。青海沙蜥的平均窝仔数最大,而红尾沙蜥最小。各繁殖特征(窝仔数、后代大小、相对繁殖投入等)与海拔存在显著的相关性。相比低海拔地区,青海沙蜥高海拔地区的雌性产小窝大仔,且繁殖投入较小；而贵德沙蜥高海拔地区的雌性产小窝小仔,且繁殖投入较小。除了贵南种群和玛多种群,其它五个种群内都存在后代数量和大小之间权衡,但这种权衡关系不存在地区间差异。繁殖特征的差异受到遗传和环境的作用。四种沙蜥种间和种内遗传多样性存在显著的差异。线粒体DNA(ND2)的遗传多样性低于核DNA(RAG1)。遗传多样性受到环境因子的影响以及种群历史动态的影响。系统发生分析结果显示,ND2进化树得到3个进化枝,贵南和倒淌河种群处于贵德沙蜥分支中,且相互之间遗传距离非常小,没有达到种间遗传距离的水平,说明贵南和倒淌河的沙蜥在进化上属于贵德沙蜥,贵南沙蜥没有达到种的分类水平。而RAG1进化树中主分支不明确,倒淌河种群有一个单倍型与德令哈种群的一些单倍型在进化上比较相近。另外倒淌河蜥蜴的形态特征更加接近于青海沙蜥。这些都说明青海沙蜥和贵德沙蜥历史上可能发生过杂交事件,并且杂交使倒淌河沙蜥具有一部分青海沙蜥的核基因,从而导致倒淌河沙蜥生活史特征的特殊性。通过生活史特征和系统发生之间的比较分析显示,系统发生关系与种间形态特征和后代大小的变化趋势存在一致性,而与总体繁殖投入(窝仔数、窝仔重和相对窝仔重等)方面的变化趋势的一致性较差。因此,系统发生作用对不同物种间形态特征和后代大小的差异具有一定的影响,而对繁殖投入方面的影响较小,说明种间繁殖投入的差异可能还受到环境的影响。而系统发生作用对种内不同种群之间的生活史特征差异的影响较小,说明高原沙蜥种内生活史特征差异主要是受到环境影响。总之,青藏高原的隆升及其引起的环境因子的海拔差异是造成高原沙蜥种间、种内形态和繁殖对策等生活史特征差异和进化的主要原因。更多还原

【Abstract】 Being ectothermic species, reptile (especially the lizards and snakes) life history traits are highly dependent on habitat conditions, thus exhibiting many life history variations induced by environmental factor. Therefore, they are favored by ecologjsts. Reptile life history traits often exhibit both interspecific and intraspecific variations, and elevation and related environmental factors contribute largely to the geographical variation. The geographical environment on Tibetan Plateau is unique, and there have great elevation drop and various habitat environments, which have contributions to current particular species distribution and diversity. Thus, it provided an ideal place for evolutionary biology studies. In this study, we chose seven populations belonging to four species of Phynocephalus (P. putjatia, P. vlangalii, P. guinanensis and P. erythrurus), which distributed in different altitudes, as object to study the life history traits variation and evolution in different altitudes from several aspects, including morphology, population ecology, reproductive ecology and molecular ecology. We intended to explore the life history variations of lizards from different altitudes and verify whether these variation trends conform to the known rules of biogeography, and to identify the sources of variation in life history.There are many differences in morphological traits were found between male and female in the four species. For adults, females have larger SVL and abdomen length than males, while males have larger tail length, relative head size and limb length in all the four Phrynocephalus. Relative head sizes are different in female between juveniles and adults, and adult female have smaller relative head size than juveniles, indicating that the development of female head is slow down after sexual maturity. The sexual size dimorphism (SSD) of these four Phynocephalus may be the result of a balance of sexual selection and fecundity selection, and also may be caused by the trade-off of energy allocation in vivo of lizards.Body size decreased with the increasing of altitude among species, which follows the converse to Bergmann’s rule. The species at higher altitude with smaller body size is adaptive evolution on the environment and controled by the phylogeny. Under the condition of low temperature and hypoxia, the temperature maintenance and energy metabolism of lizard are under restrictions and energy for growth may relatively less, which make lizards evolve into smaller size. However, the higher altitude species had relative smaller tail length and head size which match the Allen’s rule. Smaller appendages have smaller superficial area that would be conducive for lizard to make full use of the environment temperature and reduce energy consumption to keep the relatively constant temperature of body. The difference in male and female size among species allows rejection of Rensch’s rule.Within P. putjatia and P. vlangalii, lizards from high altitude have larger body size than those from low altitude, which follows Bergmann’s rule and may be the results of the differences in newborn body size and sexual maturely size among populations. The intraspecific difference may be under the influence of environment. Lizards from high altitude population have smaller tail length, head size and limb length, which follows Allen’s rule. There is no difference in the relative abdomen length of male among altitudes. However, females from high altitude have larger relative abdomen length in P. vlangalii, but have smaller relative abdomen length in P. putjatia, than those from low altitude. The difference in abdomen length among populations may affect offspring size.The caudal vertebra number of Phrynocephalus has no difference between the genders, and has no significant correlation with body size, which indicated that the caudal vertebra number of Phrynocephalus is fixed after birth, and would not change with the increasing of body size. So this phenomenon could not be explained by the Jordan’s rule. The variation of caudal vertebra number may be affected by genetic and phylogenetic factors, as well as temperature.Skeletochronology analysis showed that the oldest age of reproductive individual in the four Phrynocephalus was6yr (experience six hibernation). Body size was almost the same between the genders before2yr; however, the difference arisen at3yr. Females grew faster than males from2yr to3yr (before sexual maturity), and the other age stages have the same growth rate between the genders. The growth rate also differed among populations/species. The variation of growth rate may caused by the difference of energy allocation in the process of growth and reproduction. Within P. vlangalii and P. putjatia, the age at sexual maturity of lizards from low altitude was2yr and younger than that from high altitude (3yr). And the age at sexual maturity of P. guinanensis and P. erythrurus were3yr.3yr and4yr were the predominant age of females participated in reproduction.3yr females dominate at low altitude and4yr females dominate at high altitude. These differences may be related to the variation of environmental temperature at different altitudes.Females gave birth between29June and7September, and the birth dates of females from lower elevation were earlier than those from higher elevation. Within species, females from the higher elevation had larger SVL at sexual maturity and mean SVL. Female size and age have positive effect on litter size, litter mass and offspring size in three Phrynocephalus except for P. erythrurus. Newly born offspring have no gender-bending, and the sex ratios have no difference among years.Reproductive traits varied significantly among populations and species. Reproductive traits were correlated with elevation. Females from the higher elevation localities had a lower RLM than those from the lower elevations. In P. vlangalii, females from the high elevation produced fewer and larger offspring. However, in P. putjatia, females from the high elevation produced fewer and smaller offspring. Trade-offs between offspring size and number were detected in P. putjatia, P. vlangalii and P. guinanensis, but not in P. erythrurus.The genetic diversity varied among populations and species. MtDNA (ND2) genetic diversity was higher than nuclear DNA (RAG1). The genetic diversity of Phrynocephalus may be affected by environmental factors and the migration of population. ND2and RAG1data were used to establish cladogram tree. ND2tree revealed three clades, and the haplotypes from GN and DTH were in the clade of P. putjatia. The genetic distance among GN, DTH and other P. putjatia populations were smaller than that between species, which indicated that lizards from DTH and GN are P. putjatia, and P. guinanensis is not a species. The pattern of RAG1tree is not clear. A haplotype from DTH and some haplotypes from DLH mixed in a clade, indicating that the ancestors of P. putjatia and P. vlangalii might have hybridization. Hence, it is make sense that lizards from DTH have similar life history traits with P. vlangalii.Life history phylogenetic comparative analysis suggested that phylogeny had large effect on the interspecific variation of morphological characteristics and offspring size, and had little effect on total reproductive investment (litter size, litter mass and RLM), which may also affected by environmental factors. Phylogeny had little effect on the intraspecific variation of life history, indicating that the intraspecific variation of life history may mainly affected by environmental factors.In summary, the variation of environmental factors along elevation, which caused by the uplift of the Tibetan Plateau, may be the main force behind the variation and evolution of life history.更多还原