Natural variation of outcrossing in the hermaphroditic nematode <it>Pristionchus pacificus</it>

• Main Authors: Click Arielle, Savaliya Chandni H, Kienle Simone, Herrmann Matthias, Pires-daSilva Andre
• Format: Article
• Language: English
• Published: BMC 2009-04-01
• Series: BMC Evolutionary Biology
• Online Access: http://www.biomedcentral.com/1471-2148/9/75

<p>Abstract</p> <p>Background</p> <p>Evolution of selfing can be associated with an increase in fixation of deleterious mutations, which in certain conditions can lead to species extinction. In nematodes, a few species evolved self-fertilization independently, making them excellent model systems to study the evolutionary consequences of this type of mating system.</p> <p>Results</p> <p>Here we determine various parameters that influence outcrossing in the hermaphroditic nematode <it>Pristionchus pacificus </it>and compare them to the better known <it>Caenorhabditis elegans</it>. These nematode species are distinct in terms of genetic diversity, which could be explained by differences in outcrossing rates. We find that, similarly to <it>C. elegans</it>, <it>P. pacificus </it>males are generated at low frequencies from self-fertilizing hermaphrodites and are relatively poor mating partners. Furthermore, crosses between different isolates reveal that hybrids have lower brood sizes than the pure strains, which is a sign of outbreeding depression. In contrast to <it>C. elegans</it>, <it>P. pacificus </it>has lower brood sizes and the male X-bearing sperm is able to outcompete the X-nullo sperm.</p> <p>Conclusion</p> <p>The results indicate that there is no evidence of any selection acting very strongly on <it>P. pacificus </it>males.</p>