Resource partitioning by forest species of harvestmen of the genus Leiobunum (Arachnida, Phalangida)

The temporal, spatial and functional niche of forest species of harvestmen (Arachnida, Phalangida) on a Southern Appalachian foot hill is investigated in order to determine if the pattern of resource partitioning is consistent with strategies dictated by competition theory.

Three species, Leiobunum calcar, L. nigropalpi and L. longipes, share common life histories in that they overwinter as eggs, reach maturity in the late spring and early summer and reproduce soon thereafter. These species show a strong overlap in diel activity and in the type and size of food items scavenged for. There is some degree of spatial segregation, most apparent at night, when different proportions of the three populations forage in different forest strata and show a preference for forest patch type along a continuum of ground cover abundance and sparseness of the forest understory.

This habitat selection is discussed in view of the likelihood that it 1) reduces the potential for competition among the species, 2) is a product of the optimal functioning of the species to obtain preferred resources and/or 3) is part of a mechanism by which the populations remain reproductively isolated. I conclude that harvestmen densities are maintained below competitive levels by predation and that species differences in habitat associations may represent diver gent adaptations to predation based on optimal functioning criteria.