Species Selection Favors Dispersive Life Histories in Sea Slugs, but Higher Per-Offspring Investment Drives Shifts to Short-Lived Larvae
Species Selection Favors Dispersive Life Histories in Sea Slugs, but Higher Per-Offspring Investment Drives Shifts to Short-Lived Larvae
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DOI：
10.1093/sysbio/syv046
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发表时间：
2015-11-01
影响因子：
6.5
通讯作者：
Valdes, Angel A.
中科院分区：
文献类型：
--
作者：
Krug, Patrick J.;Vendetti, Jann E.;Valdes, Angel A.
40年来，对海洋腹足类的古生物学研究表明，物种选择有利于具有短寿命（卵营养型）幼虫的谱系，这些幼虫比长寿命（卵营养型）幼虫分散性小。虽然lecithotrophs似乎更经常形成和积累随着时间的推移，在一些群体，lecithotrophs也增加了灭绝率，和测试状态依赖的多样化从来没有进行。相反，不同群体的分子遗传学表明，由于频繁的单向特征变化，嗜石盐菌积累而不多样化。尽管大多数门都反复起源于卵黄营养，但没有任何成虫特征与幼虫类型的变化相关。因此，无论是lecithotrophy的进化起源和物种丰富度模式的后果仍然知之甚少。在这里，我们测试假设的发展模式和进化率之间的联系，使用基于可能性的方法和202种腹足类软体动物的食草性海蛞蝓的一个分支Sacoglossa的一个分支。进化数量遗传学建模和随机性状图谱支持了27种卵黄营养起源。相关进化的测试显示，在投资于胚胎外蛋黄的谱系中，lecithotrophy更经常进化，这是与整个群体的发育模式转变相关的第一个成年特征。然而，与古生物学研究的预测相反，物种选择实际上有利于反硝化;大多数现存的石养生物起源于最近的性状变化，并且随后没有多样化。因此，在自养生物中增加后代供应有利于向短命幼虫转移，这导致了在宏观进化时间尺度上短命的谱系。这些发现挑战了长期以来关于海洋中替代生命历史影响的假设。物种选择可以解释浮游生物营养的长期持续性，这是大多数进化枝的祖先状态，尽管频繁地过渡到卵黄营养。
For 40 years, paleontological studies of marine gastropods have suggested that species selection favors lineages with short-lived (lecithotrophic) larvae, which are less dispersive than long-lived (planktotrophic) larvae. Although lecithotrophs appeared to speciate more often and accumulate over time in some groups, lecithotrophy also increased extinction rates, and tests for state-dependent diversification were never performed. Molecular phylogenies of diverse groups instead suggested lecithotrophs accumulate without diversifying due to frequent, unidirectional character change. Although lecithotrophy has repeatedly originated in most phyla, no adult trait has been correlated with shifts in larval type. Thus, both the evolutionary origins of lecithotrophy and its consequences for patterns of species richness remain poorly understood. Here, we test hypothesized links between development mode and evolutionary rates using likelihood-based methods and a phylogeny of 202 species of gastropod molluscs in Sacoglossa, a clade of herbivorous sea slugs. Evolutionary quantitative genetics modeling and stochastic character mapping supported 27 origins of lecithotrophy. Tests for correlated evolution revealed lecithotrophy evolved more often in lineages investing in extra-embryonic yolk, the first adult trait associated with shifts in development mode across a group. However, contrary to predictions from paleontological studies, species selection actually favored planktotrophy; most extant lecithotrophs originated through recent character change, and did not subsequently diversify. Increased offspring provisioning in planktotrophs thus favored shifts to short-lived larvae, which led to short-lived lineages over macroevolutionary time scales. These findings challenge long-standing assumptions about the effects of alternative life histories in the sea. Species selection can explain the long-term persistence of planktotrophy, the ancestral state in most clades, despite frequent transitions to lecithotrophy.