The evolution of the placenta in poeciliid fishes
The evolution of the placenta in poeciliid fishes
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DOI：
10.1016/j.cub.2021.02.008
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发表时间：
2021-05-10
期刊：
影响因子：
9.2
通讯作者：
Reznick, David N.
中科院分区：
文献类型：
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作者：
Furness, Andrew I.;Avise, John C.;Reznick, David N.
复杂器官是如何进化的，以及为什么进化，这在历史中已经被遗忘了。例如，哺乳动物的胎盘来自一个生活在1亿多年前的共同祖先。因此，支持这一复杂性状的选择因素仍然不清楚。在生鱼科Poeciliidae的物种中，胎盘独立进化了许多次，同时保留了密切相关的非胎盘姐妹物种。（4-7）这为检验胎盘进化的其他假说提供了原材料。我们收集了大量关于繁殖模式、生活史和栖息地的物种水平数据，然后采用系统发育比较方法来检验胎盘进化的适应性假设。我们发现胎盘和栖息地之间没有一致的全家族关联。然而，胎盘物种表现出显著减少的生殖分配，并有更高的可能性表现出重叠妊娠（在不同发育阶段孕育多窝的能力）。这两个特征都有可能增加身体流线型和增强怀孕期间的运动能力，可能在高捕食或水流快的环境中提供选择优势。此外，我们还发现体型和胎位对后代的体型和繁殖力有显著的相互作用。与非胎盘物种相比，小体物种的繁殖力较高，后代体积较小，而大体物种的繁殖力较低，后代体积较大。这一模式表明，可能存在两个与胎盘相关的表型适应峰值，对应于两个选择最佳：一个由生命史快的小体物种代表，另一个由生命史慢的大体物种代表。
How and why complex organs evolve is generally lost to history. The mammalian placenta, for example, was derived from a single common ancestor that lived over 100 million years ago.(1-3) Therefore, the selective factors favoring this complex trait remain obscure. Species in the live-bearing fish family Poeciliidae have independently evolved placentas numerous times while retaining closely related non-placental sister species.(4-7) This provides the raw material to test alternative hypotheses for the evolution of the placenta. We assemble an extensive species-level dataset on reproductive mode, life histories, and habitat, and then implement phylogenetic comparative methods to test adaptive hypotheses for the evolution of the placenta. We find no consistent family-wide associations between placentation and habitat. However, placental species exhibit significantly reduced reproductive allotment and have a higher likelihood of exhibiting superfetation (the ability to gestate multiple broods at different developmental stages). Both features potentially increase body streamlining and enhance locomotor performance during pregnancy, possibly providing selective advantage in performance-demanding environments such as those with high predation or fast water flow. Furthermore, we found significant interactions between body size and placentation for offspring size and fecundity. Relative to non-placental species, placentation is associated with higher fecundity and smaller offspring size in small-bodied species and lower fecundity and larger offspring size in large-bodied species. This pattern suggests that there may be two phenotypic adaptive peaks, corresponding to two selective optima, associated with placentation: one represented by small-bodied species that have fast life histories, and the second by large-bodied species with slow life histories.