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 point is discontinuous rather than continuous, and (2) the linear slope of mandibular length versus elytral length changes at the hypothesized switch point. The male dimorphisms are likely related to male mating strategies where minor males increase the chances to encounter females by maintaining maneuverability, while major males do the same through intraspecific combat. Male dimorphisms may also be correlated with patterns of fungal usage.