LTREB: Long-term Research on Environmental Gender Determination in a Model System (Chrysemys)

与大多数脊椎动物的性别决定机制不同，许多爬行动物的性别是由胚胎发育过程中的环境温度决定的。这种性别决定系统的不同寻常的性质，以及它可能产生强烈偏见的性别配给，引起了人们对其进化起源和生物学意义的极大兴趣。尽管如此，人们对这种依赖温度的性别决定(TSD)的许多方面的重要性却知之甚少，这些方面可以为我们提供对这些基本问题的洞察。特别是，在患有TSD的爬行动物中，长期气候变化对关键的种群参数，即后代和种群性别比的影响尚不清楚。此外，巢址选择在这个系统中的作用几乎没有被探索过，特别是在这些分类群具有较长的生殖寿命的情况下，尽管它在大多数性别比进化的理论模型中具有重要意义。捕食，无论是否有偏见，在种群动力学的理论模型中也扮演着重要的角色，但它对后代性别比的影响尚不清楚。具有TSD的生物是探索这些主要因素对自然界中种群动态和性别比进化的影响的理想模型系统。拟议的LTREB研究将在一个自然种群的长寿彩龟中调查TSD进化生态学的几个重要方面，这一研究自1988年以来一直被详细研究。首先，长期气候变化如何随着年度队列性别比的变化而变化，从而影响人口统计学和TSD的演变？其次，患有TSD的雌性个体是否表现出个体发育对可用热环境的nst位置选择的长期重复性，从而为快速气候变化和人类栖息地改变强加的性别比选择提供了进化反应的目标？第三，在患有TSD的自然种群中，巢被捕食和后代性别比的长期时空动态是什么，因此它们对种群人口学和性别比进化的影响是什么？考虑到快速的气候变化和人类栖息地的改变，获得这些问题的答案显得更加紧迫。

0089680JanzenIn contrast to the sex-determining mechanisms of most vertebrates, sex in many reptiles is determined by environmental temperatures determined during embryonic development. The unusual nature of this sex-determination system, with its potential to produce strongly-biased sex rations, has generated considerable interest in its evolutionary origin and biological significance. Nonetheless, little is understood about the importance of many aspects of this temperature-dependent sex determination (TSD) that could lend insight into these fundamental questions. In particular, the impact of long-term climatic variation on crucial demograpic parameters, namely offspring and population sex ratios, is unclear in reptiles with TSD. Furthermore, the role of nest-site choice in this system is virtually unexplored, especially across the long reproductive lifespans that characterize these taxa, despite its significance in most theoretical models of sex-ratio evolution. Predation, biased or otherwise, also occupies a significant role in theoretical models of population dynamics but its impact on offspring sex ratio is unknown. Organisms with TSD are ideal model systems with which to explore the impact of these major factors on population dynamics and sex-ratio evolution in nature. The proposed LTREB research will investigate several significant aspects of the evolutionary ecology of TSD in a natural population of long-lived painted turtles, which has been studied in detail since 1988. First, how does long-term climatic variation covary with annual cohort sex ratio and thus influence population demography and the evolution of TSD? Second, do females with TSD exhibit long-term ontogenetic repeatability of nst-site choice with respect to available thermal environments and thereby provide a target for evolutionary response to sex-ratio selection imposed by rapid climate change and human habitat modification? Third, what are the long-term spatio-temporal dynamics of nest predation and offspring sex ratio in a natural population with TSD and thus their impacts on population demography and sex-ratio evolution? Obtaining answers to such questions assumes greater urgency given rapid climate change and human habitat modification.