FEMALE MATE CHOICE IN A SUBSOCIAL BEETLE - MALE PHENOTYPE CORRELATES WITH HELPING POTENTIAL AND OFFSPRING SURVIVAL

In Parastizopus armaticeps (Tenebrionidae), a nocturnal desert beetle, the males excavate breeding burrows and maintain their moisture level while the females provision the larvae with detritus collected on the surface. The beetles court in small groups on the surface at night af ter rain. Male size distribution in these groups corresponded to that in the population but more large and fewer small females were present than expected and more large beetles of both sexes bred. Offspring num ber correlated positively with burrow depth and body length for males but not for females. Since large males dig deeper burrows, which resul ts in higher larval survival rate, females should prefer them. In choi ce experiments, females selected larger males. Behavioural analyses sh owed that choice was not dependent on differences in male courtship ac tivity or intermale dominance. When the mass of the smaller male was i ncreased experimentally by a dorsally attached weight, the smaller mal e was preferred, females estimating male size difference by mass. Part ner choice is therefore epigamic for a male phenotypic character which correlates with both parenting ability and greater reproductive succe ss for females. (C) 1998 The Association for the Study of Animal Behav iour.