Data from: Time-limited environments affect the evolution of egg - body size allometry

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 co-evolution 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. In order 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 size and body size in annual, compared to non-annual species. We also found higher rates of evolution of egg and body size in annual compared to non-annual 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.

初始子代体型是绝对生长速率的核心决定组分，体型较大的子代相较于体型较小的子代，能够更快达到既定的成体体型。然而，目前学界对于子代体型与成体体型之间的协同进化关系，认知仍较为有限。
在时间受限的环境中，生物需要以较高的繁殖速率完成繁衍，并快速达到繁殖体型。为此我们提出假说：在季节性生境中，为了快速获得较大的成体体型，大型物种必然拥有较大的初始子代体型；相较于受时间约束程度更低的环境系统，此类生境中卵大小的进化将与成体体型的进化紧密耦合。
我们以鳉鱼（killifishes）为研究对象验证该假说，结果发现：相较于非一年生鳉鱼，一年生鳉鱼的卵大小与成体体型之间的异速生长关系斜率显著更高。同时，一年生物种的卵大小与成体体型的进化速率也显著高于非一年生物种。
我们的研究结果表明，时间受限的环境会对物种快速达到物种特异性体型以及高效繁殖施加强烈的选择压力，进而对卵大小的进化形成约束。综上，这些差异化的选择压力导致了时间受限生境与永久生境中，不同物种间卵大小与成体体型的关联模式存在显著差异。