Dpto de Zoología y Antropología Física Vertebrados, Facultad de Biología, Universidad Complutense, 28040 Madrid, Spain.
Oecologia. 2013 May;172(1):167-76. doi: 10.1007/s00442-012-2492-8. Epub 2012 Oct 18.
The trade-off between clutch and offspring size, which is a central topic in life-history research, is shaped by natural selection to maximize the number of surviving offspring, but it also depends on the resources available for reproduction. Conspecific populations living in different environments may differ in adult body size, clutch mass, clutch size, offspring size, and/or post-natal growth rates, due either to phenotypic plasticity or to local adaptation. Here, we compare these traits and their relationships between two populations of the lizard Psammodromus algirus separated by a 600-m altitudinal gradient. We used a common garden design to control incubation temperature and food availability, with two different feeding treatments. Females were larger at the high-elevation site. Although SVL-adjusted clutch mass did not differ between populations, high-elevation females laid more but smaller eggs than low-elevation ones. Hatchlings were larger at lower elevation. Our common garden experiment revealed that low-elevation hatchlings grew faster than high-elevation hatchlings under both feeding treatments. However, higher food availability at higher altitude allows high-elevation lizards to grow faster and attain larger adult sizes, especially in the case of females. The two key adaptations of low-elevation lizards, large eggs and hatchlings and the ability to grow rapidly after hatching, are likely to enhance survival in low-productivity Mediterranean lowlands. Our data support the hypothesis that the reproductive strategies of these populations provide an example of countergradient variation, because the genotypes that encode for fast growth and large body size occurred in low food availability habitats where juveniles grew slowly and attained small adult sizes.
卵囊大小与后代大小的权衡是生命史研究的核心课题，它受到自然选择的影响，旨在最大限度地增加存活后代的数量，但也取决于繁殖所需的资源。生活在不同环境中的同种群体在成体体型、卵囊质量、卵囊大小、后代大小和/或产后生长率方面可能存在差异，这要么是由于表型可塑性，要么是由于局部适应。在这里，我们比较了两种蜥蜴 Psammodromus algirus 种群的这些特征及其关系，这两种蜥蜴种群被 600 米的海拔梯度隔开。我们使用了一个共同的花园设计来控制孵化温度和食物供应，有两种不同的喂养处理。高海拔地区的雌性体型较大。尽管种群间 SVL 调整后的卵囊质量没有差异，但高海拔地区的雌性产下的卵囊数量更多，但卵囊较小。低海拔地区的幼体体型较大。我们的共同花园实验表明，在两种喂养处理下，低海拔地区的幼体孵化后生长速度比高海拔地区的快。然而，高海拔地区较高的食物供应使高海拔蜥蜴生长更快，达到更大的成年体型，特别是雌性蜥蜴。低海拔蜥蜴的两个关键适应特征，即大卵和幼体，以及孵化后快速生长的能力，很可能提高它们在低生产力的地中海低地的存活率。我们的数据支持了这样一种假设，即这些种群的繁殖策略提供了一个反梯度变异的例子，因为编码快速生长和大体型的基因型出现在食物供应不足的栖息地，在这些栖息地中，幼体生长缓慢，成年体型较小。
