INTENSE SELECTION OF MITE CLONES IN A HETEROGENEOUS ENVIRONMENT

Genetic diversity within obligatorily parthenogenic species can be hig h, contrary to common views of the evolutionary consequences of this r eproductive system. How this clonal diversity is maintained within pop ulations is not clearly understood. Previous studies showing high clon al diversity have used parthenogenic organisms with known sexual forms or relatives. Here we report significant spatial and temporal clonal diversity within two populations of an obligatorily parthenogenic mite , Penthaleus major, which has no known sexual form or close sexual rel ative. Fitness estimates from temporal sampling at two sites and manip ulated field plots reveal intense natural selection acting on ecologic ally different clones. We propose that environmental heterogeneity con tributes to the maintenance of clonal diversity within populations of P. major and that selection is strong enough to overcome the problems of relative niche size.