用双繁殖模式属代表物种研究蜥蜴对气候暖化的易危性

This project will assess vulnerability of lizards to climate changes in mainland China. It is motivated by recent discovery that climate warming has already driven many lizard populations extinct as well as by the prediction that warming will drive many more extinct by 2080. Lizard extinctions are exacerbated by climate-driven vegetation change, specifically by changes in structure of plant canopies that alter thermal loads on lizards and evapotranspiration that alters hydric environments of eggs in soil. Because lizard extinction is happening now and because lizards are important to many ecosystems, studies that quantify extinction risks of populations must be a high priority for biodiversity studies. Lizard extinctions are phylogenetically, physiologically, or geographically not random. Risks can be evaluated and predicted, but doing so requires integration of both real-time (field) and historical (phylogenetic) analyses. We need to know what traits make a lizard vulnerable now, and how and why those traits evolved. Here, we will use 10 lizard species selected from five reproductively bimodal genera to answer three main questions: (1) Is extinction risk elevated for viviparous species because they have evolved reduced heat tolerance? (2) Is extinction risk higher in species where evolutionary rates of the phenotypes adapting to specific habitats are more likely to lag behind climate change? (3) Is extinction risk associated with viviparity, geography, and species range limits? We will use the difference between operative temperature (Te) and preferred body temperature (Tp) during breeding seasons as a predictor of extinction risk, as Te data can estimate the number of hours that lizards can be active. We expect Te to be higher at the extinction sites, and extinction risk to be higher in species with lower Tp. We will establish mechanistic niche models for the 10 species studied herein to test the hypothesis that extinction risk is higher in species with lower evolutionary rates of phenotypes. We will maintain congeneric lizards with different reproductive modes in warming environments to test the hypothesis that extinction risk is high in species where thermoregulatory behavior is highly sensitive to warming. We will use 2 nDNA (RAG1 and PDC) and 2 mtDNA (COI and Cyt b) loci to resolve relationships among species groups, species within groups, and intra-specific units. Because species with adjacent or overlapping ranges might be related phylogenetically and hence are not statistically independent sampling units, we will use phylogenetic ANOVA and phylogenetic generalized least squares implemented in R to determine associations for viviparity, species limits, and historical changes in climate warming on contemporary extinction risks. With the data from this study, we will develop conservation measures that can be adopted across mainland China to preserve critically endangered lizard species from effects of climate changes.

蜥蜴对气候暖化的易危性与有关物种的系统发生、形态和生理特性、地理分布、分布区大小等相关，评估这种易危性及相应的种群灭绝风险需要整合实时和历史分析结果。申请人拟以中国大陆5个双繁殖模式属卵生和卵胎生各5种蜥蜴为代表，探讨3 个主要问题：1、卵胎生类群在变暖环境中具有高于卵生类群的易危性是否与卵胎生进化伴随高温耐受性下降有关？2、区域或山地特有种在变暖环境中具有高于广布物种的易危性是否与前者表型反应模随环境的变化速率相对较低有关？3、对气候暖化的易危性是否因具有谱系非依赖性而更多地与物种地理分布、分布区大小和繁殖模式有关？因有效热负荷Te与调温活动负相关，申请人预测Te高的地区易于发生灭绝、喜好体温低的物种易于发生灭绝。申请人还将通过室内实验，检验"在升温热环境中行为调温受影响较大的物种灭绝风险较大"和"表型反应模随环境变化的临界速率与环境变化速率差异较大的物种灭绝风险较大"假设的有效性。

蜥蜴正在经历与两栖动物相似的种群衰退和灭绝，气候暖化被认为与此有关。蜥蜴中，卵胎生物种被认为对气候暖化的易危性大于卵生种，原因是卵胎生进化伴随喜好体温和热耐受性下降。然而，这一假设并未经过实验检验。为检验此假设，我们以5个双繁殖模式属卵生和卵胎生各5种蜥蜴（荒漠沙蜥/贵德沙蜥、丽斑麻蜥/密点麻蜥、宁波滑蜥/南滑蜥、股鳞蜓蜥/印度蜓蜥、长尾南蜥/多线南蜥）为代表，各属用3温度（20、24和28 ℃）和不同繁殖模式各一种的因子设计实验，模拟气候暖化检验相关假设。操纵环境温度影响蜥蜴的活动节律和喜好体温、卵胎生物种的产仔期等，生育力、繁殖输出，以及后代的大小、形态和运动等其它特征不受显著影响。两性对气候暖化的行为响应无显著差异。卵胎生物种行为调温比卵生种更活跃，但同属不同繁殖模式的蜥蜴在相同热环境下的喜好体温无显著差异。气候暖化缩短调温活动时间，但该效应对卵胎生物种更显著。本研究数据支持卵胎生物种对气候暖化的易危性更高的假设，但这并非是卵胎生物种有较低的喜好体温和热耐受性，而是气候暖化对卵胎生物种活动的制约更显著。..本研究还发现冷气候区和温带蜥蜴比温暖气候区蜥蜴选择更高的体温并能耐受更极端的温度。蜥蜴对气候变化的适应反映其进化历程，选择体温和温度耐受上限更多地反映祖先状态，而温度耐受下限更多地与当前气候适应有关，表明卵胎生进化受适应极端气候条件的驱动。PGLS 结果显示蜥蜴热生理表现多与气候变量、栖息地特征和其它生态因子有关，而与繁殖模式本身无关。..动物获取的能量须在彼此冲突的需求之间进行分配，而繁殖能量分配的优先次序次于维持和生长。这种能量分配的等级序位提示维持能耗较高的物种或类群分配用于繁殖的能量较少或不太可能进化出能耗较高的繁殖模式。我们分析迄今报道的196种有鳞类标准代谢率数据，发现卵胎生物种维持能耗比卵生物种更低。由于卵胎生是能耗较高的繁殖模式，我们的结果支持卵胎生进化伴随维持能耗下降的假设。

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