Is the 'best season' the best choice? Temporal variations of β-diversity patterns in moth communities of Calabrian black pine forests

摘要

In this paper we address the question of changes in community structures along temporal gradients and whether such changes affect beta-diversity patterns. We examined how differences among moth communities vary across seasons and between years in a mosaic-like pine forest of Calabria, Italy. Samples were gathered from 15 sites entering presence/absence and abundance data in pairwise and multisite analyses. We found a strong instability of pairwise beta-diversity coupled with a high stability of multisite beta-diversity across moth flight seasons. Phenology and autoecology of individual species were the main drivers of pairwise beta-diversity instability as demonstrated by the change of indicator species. Although we observed substantial changes in abundance of species, the beta-diversity patterns sampled in a given period were very similar between years. This is probably due to the synchronized fluctuation of populations that similarly changes the abundance of species over large areas, leaving the dissimilarity between sites unaltered. Applicative implications arose from our study as we demonstrated that it is better to sample the whole flying season of moths during one year extensively rather than over more years during only 'the best season' because beta-diversity patterns were much more stable across years than across seasons.