Community structure of acorn weevils (Curculio): Inferences from multispecies occupancy models

We tested whether community structure of insect seed predators is influenced by spatiotemporal variation in mast availability on host-tree species. Specifically, mast production and acorn weevil (Curculio L., 1758) occupancy were estimated annually from 2006 to 2008 for individual host trees in a sample of 74 northern red oaks (Quercus rubra L.), 100 white oaks (Quercus alba L.), and 81 shagbark hickories (Carya ovata (Mill.) K. Koch) in west-central Indiana, USA. Occupancy and vital rates of nine Curculio species on their primary host-tree species were derived using multispecies, multiseason (MSMS) models within a Bayesian framework, accounting for imperfect detection. Mast production of host trees had a strong positive effect on community-level occupancy and survival of Curculio. Mast production varied considerably between years and generally was spatially autocorrelated only at distances <2 km, which likely reduced interspecific resource competition. Derived estimates of mean weevil species richness per tree and community similarity were highest in 2007 when mast production on all host-tree species was in phase. Generalist species compensated for lower survival rate on secondary hosts with higher colonization rates on these hosts during a year of mast failure in the primary host. We hypothesize that differential suitability of hosts as resources for Curculio created a spatial storage effect that, when coupled with a temporal storage effect induced by prolonged diapause common among Curculio, facilitated species coexistence. Methodologically, increased precision of parameter estimates from MSMS models makes it generally more useful than single-species models in studies of community dynamics.