Phylogenetic evidence for a single long-lived clade of crustacean cyclic parthenogens and its implications far the evolution of sex
Phylogenetic evidence for a single long-lived clade of crustacean cyclic parthenogens and its implications far the evolution of sex
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DOI：
10.1098/rspb.1999.0707
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发表时间：
1999-04-22
影响因子：
4.7
通讯作者：
Brown, WM
中科院分区：
文献类型：
--
作者：
Taylor, DJ;Crease, TJ;Brown, WM
有性繁殖的短期优势尚不清楚，但能够产生减数分裂或无融合卵子(循环孤雌生殖，CP)的群体的存在可能表明，有性繁殖的短期优势存在。或者，CP可能是无性和有性之间的一个不稳定的过渡阶段，或者是一个系统发育上有利的生活史(即分支选择)。对鳃足类甲壳类繁育系统和种群遗传学的广泛了解使它们成为检验这些假说的系统发育预测的有用群体。一些支持者支持这一假设，即CP在五个支脚类甲壳类动物中进化了多次。我们从核rRNA序列(大亚基和小亚基)、形态和复杂的rRNA茎环结构中推断出第一个健壮的支脚类系统发育，以评估循环孤雌生殖的系统发育分布。基于序列的、结构的rRNA和全部证据的系统发育是一致的，并表明周期性孤雌生殖只在鳃足类中出现过一次，这一支系是长期存在的(至少自二叠纪以来)，它已广泛辐射到几乎每一个水生栖息地，而没有恢复到严格的有性繁殖，而且很少转变为严格的无性繁殖。这些结果与分支选择假说一致，但与CP是导致严格有性繁殖的短暂阶段的假说不一致。证据还表明，CP的支系选择是维持CP生活史中性别维持的一种可行的替代解释。
The short-term advantages of sexual reproduction are unclear, but the existence of groups that are capable of producing either meiotic or ameiotic eggs (cyclic parthenogenesis, CP) might indicate that short-term advantages to sex exist. Alternatively, CP might be an unstable transitory stage between asexuality and sex, or a phylogenetically favoured life cycle (i.e. clade selection). The extensive knowledge of breeding systems and population genetics in branchiopod crustaceans makes them a useful group to test phylogenetic predictions of these hypotheses. Several proponents favour the hypothesis that CP has evolved multiple times in five orders of branchiopod crustaceans. We inferred the first robust branchiopod phylogeny from nuclear rRNA sequence (small-subunit and large-subunit), morphology, and complex rRNA stem-loop structures to assess the phylogenetic distribution of cyclic parthenogenesis. The sequence-based, structural rRNA and total evidence phylogenies are concordant and suggest that cyclic parthenogenesis arose once in the branchiopods, that this clade is long-lived (at least since the Permian), and that it has radiated extensively into nearly every aqueous habitat without reverting to strict sexuality and only rarely transforming to strict asexuality. These results are consistent with the clade selection hypothesis but inconsistent with the predictions of the hypothesis that CP is a transitory stage that leads to strict sexual reproduction. The evidence also indicates that clade selection for CP is a viable alternative explanation for the maintenance of sex in CP life cycles.