Mandibular allometry and male dimorphism in a group of obligately mycophagous beetles (Insecta : Coleoptera : Staphylinidae : Oxyporinae)

Analyses of seven species of the obligately mycophagous staphylinid beetle genus Oxyporus indicate that five species display male mandibular allometry . Among species with dimorphic separations, two general allometric patterns were observed: (1) change in mandibular length at a hypothesized switch po int is discontinuous rather than continuous, and (2) the linear slope of ma ndibular length versus elytral length changes at the hypothesized switch po int. The male dimorphisms are likely related to male mating strategies wher e minor males increase the chances to encounter females by maintaining mane uverability, while major males do the same through intraspecific combat. Ma le dimorphisms may also be correlated with patterns of fungal usage. (C) 20 01 The Linnean Society of London.