The Marine Laboratory, University of Guam, Mangilao, GU 96923, Guam.
Proc Biol Sci. 2011 Jan 7;278(1702):75-81. doi: 10.1098/rspb.2010.1196. Epub 2010 Jul 21.
Sexuality and reproductive mode are two fundamental life-history traits that exhibit largely unexplained macroevolutionary patterns among the major groups of multicellular organisms. For example, the cnidarian class Anthozoa (corals and anemones) is mainly comprised of gonochoric (separate sex) brooders or spawners, while one order, Scleractinia (skeleton-forming corals), appears to be mostly hermaphroditic spawners. Here, using the most complete phylogeny of scleractinians, we reconstruct how evolutionary transitions between sexual systems (gonochorism versus hermaphrodism) and reproductive modes (brooding versus spawning) have generated large-scale taxonomic patterns in these characters. Hermaphrodites have independently evolved in three large, distantly related lineages consisting of mostly reef-building species. Reproductive mode in corals has evolved at twice the rate of sexuality, while the evolution of sexuality has been heavily biased: gonochorism is over 100 times more likely to be lost than gained, and can only be acquired by brooders. This circuitous evolutionary pathway accounts for the prevalence of hermaphroditic spawners among reef-forming scleractinians, despite their ancient gonochoric heritage.
性和生殖模式是两种基本的生活史特征，在多细胞生物的主要类群中表现出很大程度上尚未解释的宏观进化模式。例如，刺胞动物门（珊瑚和海葵）主要由雌雄异体（分开的性别）的孵育者或产卵者组成，而一个目，石珊瑚目（形成骨骼的珊瑚），似乎主要是雌雄同体的产卵者。在这里，我们使用最完整的石珊瑚系统发育树，重建了性系统（雌雄异体与雌雄同体）和生殖模式（孵育与产卵）之间的进化转变如何在这些特征中产生大规模的分类模式。雌雄同体在三个大的、远缘的谱系中独立进化，这些谱系主要由造礁物种组成。珊瑚的生殖模式的进化速度是性别的两倍，而性别的进化则存在严重的偏向：雄雌同体失去的可能性是获得的可能性的 100 多倍，而且只能通过孵育者获得。尽管石珊瑚目具有古老的雌雄异体遗传，但这种迂回的进化途径解释了造礁石珊瑚目中海葵产卵者的普遍存在。
