Substrate Influences Turtle Nest Temperature, Incubation Period, and Offspring Sex Ratio in the Field
Substrate Influences Turtle Nest Temperature, Incubation Period, and Offspring Sex Ratio in the Field
复制标题
基质影响田间龟巢温度、孵化期和后代性别比
作者：
Timothy S. Mitchell;F. Janzen
摘要：温度依赖性性别决定是爬行动物中一种常见的性别决定机制，即卵的孵化温度不可逆地决定后代的性别。天气是爬行动物巢穴温度的主要决定因素，但天气的影响是通过母亲选择的巢穴微生境（例如，上层树冠覆盖）来调节的。巢微生境的一个潜在的重要方面是用于筑巢的物理基质。然而，基质类型对巢温和后代性别决定的影响尚未在野外进行过实验评估。我们在三种基质中孵化彩绘龟（Chrysemys picta）的蛋，这些基质与我们研究群体中通常选择的筑巢基质相似。在一个单一的研究地点，我们建造了坑，我们用壤土，沙子或砾石填充。然后，我们在每种基质类型中创建人工巢，并随机分配鸡蛋到基质处理中。基质类型影响巢内温度和土壤湿度，并影响孵育时间，但除后代性别比例外，其他表型均不受影响。较冷的壤土产生了最偏向男性的结果。这一发现说明了筑巢基质作为筑巢地点选择的一个组成部分和作为模拟未来筑巢温度情景的一个因素的潜在重要性。
Abstract: Temperature-dependent sex determination, where egg incubation temperature irreversibly determines offspring sex, is a common sex-determining mechanism in reptiles. Weather is the primary determinant of temperature in reptile nests, yet the effects of weather are mediated through the nest microhabitat selected by the mother (e.g., overstory canopy cover). One potentially important aspect of the nest microhabitat is the physical substrate used for nesting. However, the influence of substrate type on nest temperature and offspring sex determination has never been experimentally assessed in the field. We incubated eggs of Painted Turtles (Chrysemys picta) in three substrate types similar to those commonly selected for nesting within our study population. Within a single study site, we constructed pits, which we refilled with loam, sand, or gravel. Then, we created artificial nests in each substrate type, and randomly assigned eggs to a substrate treatment. Substrate type influenced nest temperature and soil moisture, and affected incubation duration, but no other phenotype measured beyond offspring sex ratios. The cooler loam yielded the most male-biased outcome. This finding illustrates the potential importance of nesting substrate as a component of nest-site choice and as a factor in modeling future nest-temperature scenarios.