Recent geography determines the distribution of some flying Hymenoptera in the Tuscan Archipelago

The aim of this paper is to examine whether current and/or Pleistocene geography affects the pattern of species richness and composition in two families of flying Hymenoptera in the Tuscan Archipelago (Italy). Faunistic data were obtained from the literature and from our own surveys. We used the Spearman rank correlation test to assess the influence on the richness of present-day and Pleistocene island area and isolation. Moreover, we searched for patterns of similarity among the six examined islands of Tuscan Archipelago, with the adjacent Tuscan mainland and Sardinia and Corsica islands by cluster analysis (UPGMA) and by parsimony analysis of endemicity (PAE). Moreover, we verified whether the percentage of typical species of Tuscany and Sardo-Corsican area is related to the recent and/or palaeogeographical distances of the islands from the two main fauna source pools. Isolation is the best predictor for species richness while Pleistocene area and Pleistocene isolation do not show any significant correlation. Cluster analysis and PAE show a biogeographic pattern where generally Capraia and Montecristo group together with Corsica, while Elba, Giglio, and Pianosa group with Tuscan mainland. Recent geography seems to also affect fauna compositions. Indeed the incidence of Tuscan and Sardo-Corsican species is related to the present-day island distance to Tuscany and Corsica. In conclusion, we strongly suggest that colonization of these islands acted by dispersal from Tuscany and Corsica, using Elba island as a stepping stone.