NATURAL VARIATION AND COPULATORY PLUG FORMATION IN CAENORHABDITIS-ELEGANS

Most of the available natural isolates of the nematode Caenorhabditis elegans have been examined and compared with the standard laboratory w ild type (Bristol N2). Molecular markers, in particular transposon res triction fragment length polymorphisms, were used to assign these isol ates to 22 different races, for which brood size and spontaneous male frequency were determined. Several distinctive traits were observed in some of these races. One example is mab-23, in a race from Vancouver, which leads to severe distortion of male genitalia and prevents male mating. Another is gro-1, segregating in a Californian race, which is associated with Slow growth, heat resistance and longevity. Many races differ from N2 in carrying a dominant allele at the plg-1 locus, caus ing copulatory plug formation by males. Properties and possible advant ages of the plugging trait have been investigated. The dominant plg-1 allele does not lead to increased male mating efficiency, but males fr om a Stanford race (CB4855), in which the plugging trait was first obs erved, are much more virile than N2 males. Crosses between N2 and CB48 55 indicate that the higher virility is due to multiple factors. Size differences between N2 and CB4855 are associated with factors mapping to LGV and LGX.