Microevolutionary studies in nematodes: a beginning

Comparisons between related species often allow the detailed genetic analys is of evolutionary processes. Here we advocate the use of the nematode Caen orhabditis elegans (and several other rhabditid species) as model systems f or microevolutionary studies. Compared to Drosophila species, which have be en a mainstay of such studies, C. elegans has a self-fertilising mode of re production, a shorter life cycle and a convenient cell-level analysis of ph enotypic variation. Data concerning its population genetics and ecology are still scarce, however. We review molecular, behavioral and developmental i ntraspecific polymorphisms for populations of C. elegans, Oscheius sp. 1 an d Pristionchus pacificus. Focusing on vulval development, which has been we ll characterized in several species, we discuss relationships between patte rns of variations: (1) for a given genotype (developmental variants), (2) a fter mutagenesis (mutability), (3) in different populations of the same spe cies (polymorphisms) and (4) between closely related species. These studies have revealed that evolutionary variations between sister species affect t hose characters that show phenotypic developmental variants, that are mutab le and that are polymorphic within species. (C) 2001 John Wiley & Sons, Inc .