Eckerström-Liedholm Simon, Sowersby Will, Gonzalez-Voyer Alejandro, Rogell Björn
Department of Zoology, Stockholm University, Stockholm, 114 18, Sweden.
Instituto de Ecología, Universidad Nacional Autónoma de México, Apartado Postal 70-275, Ciudad Universitaria, 04510, Cd México, Mexico.
Evolution. 2017 Jul;71(7):1900-1910. doi: 10.1111/evo.13286. Epub 2017 Jun 19.
Initial offspring size is a fundamental component of absolute growth rate, where large offspring will reach a given adult body size faster than smaller offspring. Yet, our knowledge regarding the coevolution between offspring and adult size is limited. In time-constrained environments, organisms need to reproduce at a high rate and reach a reproductive size quickly. To rapidly attain a large adult body size, we hypothesize that, in seasonal habitats, large species are bound to having a large initial size, and consequently, the evolution of egg size will be tightly matched to that of body size, compared to less time-limited systems. We tested this hypothesis in killifishes, and found a significantly steeper allometric relationship between egg and body sizes in annual, compared to nonannual species. We also found higher rates of evolution of egg and body size in annual compared to nonannual species. Our results suggest that time-constrained environments impose strong selection on rapidly reaching a species-specific body size, and reproduce at a high rate, which in turn imposes constraints on the evolution of egg sizes. In combination, these distinct selection pressures result in different relationships between egg and body size among species in time-constrained versus permanent habitats.
初始后代大小是绝对生长率的一个基本组成部分，大型后代比小型后代更快达到特定的成年体型。然而，我们关于后代与成年体型之间协同进化的知识有限。在时间受限的环境中，生物体需要以高繁殖率进行繁殖并迅速达到繁殖体型。为了快速达到大型成年体型，我们推测，在季节性栖息地中，大型物种必然具有较大的初始大小，因此，与时间限制较少的系统相比，卵大小的进化将与体型的进化紧密匹配。我们在鳉鱼中检验了这一假设，发现与非一年生物种相比，一年生物种的卵大小与体型之间的异速生长关系显著更陡峭。我们还发现，与非一年生物种相比，一年生物种的卵大小和体型的进化速率更高。我们的结果表明，时间受限的环境对迅速达到特定物种体型并以高繁殖率进行繁殖施加了强烈选择，这反过来又对卵大小的进化施加了限制。综合起来，这些不同的选择压力导致时间受限栖息地与永久栖息地的物种之间卵大小与体型的关系有所不同。
