实验检验两种共栖草蜥杂交产出可育后代的假设

Hybrid speciation has long fascinated evolutionary biologists and laymen alike, presumably because it challenges the classical viewpoint of evolution as a 'one-way street' leading to strictly tree-like patterns of ancestry and descent. Naturally occurring hybrids among reptile species have been reported with some regularity, but are generally considered uncommon. This project will test the hypothesis that hybridization between two coexisting Takydromus lizards (Lacertidae), T. sexlineatus and T. septentrionalis, leads to production of fertile offspring. It is motivated by recent and startling discovery of naturally occurring individuals morphologically similar to both T. sexlineatus and T. septentrionalis. This finding raises the hypothesis of whether these naturally occurring hybrids inform hybrid speciation in Takydromus lizards. To test this hypothesis, we need to answer three questions: (1) Are naturally occurring individuals morphologically similar to both T. sexlineatus and T. septentrionalis hybrids between the two species? (2) Is there any gene flow between the two Takydromus lizards in the area where they are sympatric? (3) Does hybridization between the Takydromus lizards lead to production of fertile offspring? We will collect individuals of both Takydromus species and putative hybrids from an area where they coexist to examine: (1) whether putative hybrids are fertile descents of the two sympatric Takydromus lizards and can therefore persist in the field as an independent group of lizards; (2) the role of gene flow between the two Takydromus lizards in influencing hybridization; and (3) the extent to which offspring produced by females mating with conspecific males differ from hybrid offspring in some important fitness-related traits such as growth rate, survivorship and fertility. We will use 10 microsatellite loci to examine gene flow between the two Takydromus species in the area where putative hybrids are found, and to assign hybrids produced in the field and laboratory to a paternal species. This study is the first to test experimentally the possibility of hybrid speciation in reptiles.

杂交物种形成挑战传统物种形成的观点。爬行动物自然杂交虽为罕见但时有发现。申请人拟通过野外调查南、北两种草蜥和形态介于两者之间的疑似杂交个体的相对数量，观测实验室和野外疑似杂交个体是否可育，以及操纵交配获得杂交异种交配雌体所产的后代，回答三个科学问题：1、野外形态介于南、北两种草蜥之间的个体是否为杂交个体？2、同域共栖的南、北两种草蜥之间是否存在基因流？3、两种草蜥杂交产出后代的适合度是否区别于同种交配的后代并且可育？申请人拟通过回答以上这三个问题，检验同域共栖的南、北两种草蜥可杂交产出可育后代的假设。申请人拟用10个微卫星座位检测同域共栖南、北两种草蜥之间的基因流，确定野外疑似杂交个体和实验室异种交配雌体所产后代的父本物种。本项目是实验检测爬行动物杂交物种形成的首项尝试。

采集10个北草蜥样点的样品（烟台，长安，南京，金寨，滁州，于都，赤壁，贵阳，桂东，桂阳，韶关，大桥）和9个南草蜥样点的样品（梨市，韶关，桂头，肇庆，宜州，百色，广州，防城港，海南），选取线粒体基因（Ctyb和COX1）和核基因（RAG1和PDC）作为分子标记，结果显示，在南、北草蜥分布区的重叠范围内存在基因渐渗。利用两种草蜥的分布点的气候数据在Maxent软件中模拟现在和未来分布区范围，发现重叠区的范围在扩大，说明两种草蜥的野外种群的基因交流程度存在加剧的可能。.连续3年采集肇庆南草蜥样品，丽水、桂阳和宁德的北草蜥样品进行室内杂交实验。发现南、北草蜥之间存在交配行为，并且以雄性北草蜥与雌性南草蜥交配居多，雄性北草蜥在形态上存在显著种群差异性。利用微卫星标记鉴定疑似杂交后代，结果显示可能存在杂交个体。利用核基因标记鉴定疑似杂交后代，结果显示其中有些个体可能是三倍体或四倍体，具体结果需要进一步的实验验证。.采集秀山岛、六横岛、滁州、丽水和长安的雄性北草蜥与丽水的雌性北草蜥进行配偶选择实验，结果显示不同种群的交配次数存在显著性差异，并且发现交配次数与距离、基因、形态和环境存在相关性。在结构方程模型中，几个变量对配偶选择存在直接或间接影响。其一，地理距离的不同造成环境因素的差别，导致了不同种群形态差别，从而使得雌性个体在配偶选择上存在一定的差异。其二，地理距离的不同造成种群基因库无法交流，使得不同种群在基因水平上产生差别，导致了不同种群在形态上的差别，从而使得雌性个体在配偶选择上存在一定的差异。.将在实验室驯化过的北草蜥于24˚C的环境下饲养，并且进行适当的加热处理后，收集体色信息。分析的体色变化的结果显示，在环境温度到最适温度的范围内，RGB中热量吸收相关变量∆R和颜色伪装相关变量∆G在不同种群中存在显著性差异。说明不同种群在体色变化上存在差异，可能与环境的适应性存在一定关系。.