Sexual selection and community structure: an island biogeographic analysis with beetles

In 1995 and 1996, chrysomelid, curculionid, and cerambycid beetles were collected from 54 islands and smaller cays in the Caribbean Sea's Virgin Islands archipelago. Each species was assigned a sexual selection value based on an index that ranged from 0 to 3, depending on the size distribution of males relative to females. It is assumed that the greater the male size relative to female size, the greater the intensity of sexual selection. Species with a high index value were less likely to occur on smaller cays and were also less likely to persist in communities on cays from one year to the next. Body size is negatively correlated with island size, indicating that conditions experienced during development are more severe on the smaller cays. Thus, prior response to sexual selection pressures appears to restrict community membership of some species in harsh habitats, perhaps because less energy is allocated to dealing with natural selection pressures.