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Abstract

Although the identification of causal genes for hybrid incompatibility is a fundamental topic in speciation research, there are at least two major limitations. First, in many systems it is difficult to culture species in the laboratory and to perform genetic analyses. Second, closely related species suitable for the analysis of speciation are often difficult to find in nature. While nematodes, in principle, have the potential to overcome these limitations, sufficient number of taxonomic samplings to find closely related species pairs have often not been performed. We focus on Pristionchusnematodes, which have a necromenic association with beetles. These nematodes are easily cultured and amenable to many genetic tools, such as genome sequences and CRISPR/Cas9 engineering. Our sampling of beetles around the world resulted in more than 30 new species of Pristionchus in the last decade. With these materials, we are running two large projects. First, we use two closely related gonochoristic species and study F2 hybrid progeny that allows screening for genes involved in nascent hybrid incompatibility during on-going speciation. Second, we use the model hermaphrodite Pristionchus pacificus and its closely related gonochoristic species. We found recovery of hermaphroditic fertility in backcrosses of hybrids to P. pacificus and established multiple lines with introgression of the gonochoristic species into the P. pacificusgenetic background. We are currently sequencing these lines to screen for genes involved in hybrid sterility in the hermaphrodites.