Stable Heterozygosity?

摘要

Bdelloid rotifers (see the figure), comprising some 380 described species, are common aquatic invertebrates with highly unusual properties, most famously their putatively ancient asexuality and ability to survive desiccation at any life stage. If truly asexual, their evolutionary success may hold the answer to why nearly all higher eukaryotes reproduce sexually and why asexual eukaryotes, arising occasionally from sexual ones, are almost always evolutionary shortlived. On page 268 of this issue, Pouchkina-Stantcheva et al. (1) present evidence of functional divergence between two copies of a gene expressed in bdelloids during desiccation. Such genes encode proteins involved in desiccation resistance in plants, invertebrates, and microorganisms. The authors argue that such divergence could provide bdelloid rotifers with greater phenotypic variation and a potential advantage from asexual reproduction.