Landberg Tobias
Biology Department, Arcadia University, Glenside, PA, USA.
Int J Dev Biol. 2014;58(10-12):909-16. doi: 10.1387/ijdb.140324TL.
Egg size varies genetically and with the maternal environment. It is correlated with and can act as a resource fueling variation in many other key life history traits. This study examined hypotheses about how plastic responses of offspring to yolk variation evolve (and contribute to phenotypic evolution) when maternal investment in egg size evolves. I used a split-clutch, controlled, surgical experiment with a longitudinal (repeated-measures) design to examine the effects of yolk removal on sister salamander species with distinct egg and larval phenotypes. Yolk removal had large effects in the derived larger-egged species, A. barbouri, and greatly reduced effects in A. texanum. Early hatching and smaller larval body size was only found in A. barbouri and survival rates decreased more in A. barbouri. These results provide strong experimental evidence that as female salamanders evolve greater yolk investment in each egg, offspring coevolve an increased magnitude of phenotypic plasticity in response to yolk variation across a suite of life history traits. Yolk therefore acts as an integrator of phenotypes that allows females to modify modules of life history traits together (facilitating adaptation). When organisms invade new environments, complex integrated phenotypes may evolve via correlated responses to increased maternal investment, yet individual traits can be coupled or decoupled to yolk quantity variation in different species.
卵的大小在遗传上以及随母体环境而变化。它与许多其他关键生活史特征的变异相关，并可作为一种资源推动这些变异。本研究探讨了在母体对卵大小的投资发生进化时，后代对卵黄变异的可塑性反应如何进化（并对表型进化做出贡献）的假说。我采用了一种具有纵向（重复测量）设计的分窝、受控的手术实验，来研究去除卵黄对具有不同卵和幼体表型的姐妹蝾螈物种的影响。去除卵黄对进化出较大卵的物种巴氏钝口螈有很大影响，而对德州钝口螈的影响则大大降低。早期孵化和较小的幼体体型仅在巴氏钝口螈中出现，且巴氏钝口螈的存活率下降得更多。这些结果提供了有力的实验证据，表明随着雌性蝾螈在每个卵中进化出更大的卵黄投资，后代会共同进化出更大幅度的表型可塑性，以应对一系列生活史特征中的卵黄变异。因此，卵黄充当了表型的整合者，使雌性能够一起改变生活史特征模块（促进适应）。当生物体侵入新环境时，复杂的综合表型可能会通过对增加的母体投资的相关反应而进化，但不同物种的个体特征可能与卵黄量变异耦合或解耦。
