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Abstract:
To identify the mechanisms by which molecular variations are introduced into developmental systems, microevolutionary approaches to evolutionary developmental biology have to be taken. We describe the molecular and developmental characterization of laboratory strains of the nematode genus Pristionchus. 13 laboratory strains of the Pristionchus genus were obtained from natural isolates from around the world. Mating experiments and ITS sequence analysis indicated that these 13 strains represent four different species; the gonochoristic species P. lheritieri and three hermaphroditic species, P. pacificus, P. maupasi and an as yet undescribed species Pristionchus sp., respectively. P. pacificus is represented by five different strains isolated from California, Washington, Hawaii, Ontario and Poland. Developmental differences during vulva formation are observed between strains from different species but also between strains of P. pacificus , like the strains from California and Poland. In particular, redundant developmental mechanisms present during vulva formation in P. pacificus var. California, are absent in other strains. AFLP analyses of the P. pacificus strains revealed that the American strains are highly polymorphic, whereas the developmentally distinct strain from Poland is identical to the Californian strain. Thus developmental differences rely on a small number of changes in developmental control genes rather than the accumulation of changes at multiple loci.
