Distance decay of similarity in fungivorous insect communities: Assessing dispersal limitation using genetic data

Abstract

We evaluated how dispersal limitation affected spatial variation in the species composition of fungivorous insect communities inhabiting fruiting bodies of bracket fungi on scattered deadwoods. The insect communities showed significant distance decay of similarity pattern among deadwoods, which was not fully explained by differences in environmental conditions. To investigate whether insect dispersal limitation could explain the distance-decay pattern, we analyzed mitochondrial haplotype data; limited dispersal is expected to generate an isolation-by- distance pattern of genetic structure in component species. However, genetic distance between deadwoods was not correlated with geographic distance in any species, and a simulation study suggested that the absence of genetic structure refutes the dispersal limitation hypothesis even when the resolution of genetic differences is not high, as in our study. Thus, dispersal limitation did not contribute to the observed community patterns within our study site, suggesting that unmeasured environmental factors may have played an important role. Our study demonstrates that genetic data can help determine whether dispersal limitation of component species is the primary cause of observed distance decay in community similarity.