Lively C M, Johnson S G
Department of Biology, Indiana University, Bloomington 47405.
Proc Biol Sci. 1994 Apr 22;256(1345):89-95. doi: 10.1098/rspb.1994.0054.
Developmental defects are expected to be common and severe in the early evolution of parthenogenesis, and they could help to explain the predominance of sexual forms of reproduction. It is difficult, however, to see how such defects might explain the ecological and phylogenetic correlates of sex. Here we suggest that internally fertilized animals that brood their young may be more susceptible to invasion by parthenogenetic mutants. The reason is that brooders could establish 'selective arenas' in which developmentally defective embryos are competitively displaced. Brooders could also selectively abort defective embryos, and replace them with minimal cost. Consistent with these ideas, we found a striking association between brooding and parthenogenesis in aquatic invertebrates. For example, in the Cnidaria and Mollusca, parthenogenesis is significantly more common in lineages that retain their young through the early stages of development. Hence brooding and ecological factors (such as escape from parasites) might combine to explain the initial spread, long-term persistence, and phylogenetic distribution of parthenogenetic reproduction.
在孤雌生殖的早期进化过程中，发育缺陷预计会很常见且严重，它们可能有助于解释有性生殖形式的优势地位。然而，很难理解这些缺陷如何能够解释性别的生态和系统发育相关性。在此我们提出，那些孵育幼崽的体内受精动物可能更容易受到孤雌生殖突变体的入侵。原因在于，孵育者能够建立“选择场”，发育有缺陷的胚胎在其中会被竞争性取代。孵育者还能够选择性地终止有缺陷胚胎的发育，并以最小的代价替换它们。与这些观点一致，我们在水生无脊椎动物中发现了孵育与孤雌生殖之间的显著关联。例如，在刺胞动物门和软体动物门中，孤雌生殖在那些在发育早期阶段保留幼崽的谱系中明显更为常见。因此，孵育和生态因素（如躲避寄生虫）可能共同作用，来解释孤雌生殖的初始传播、长期存在以及系统发育分布。
