A PRELIMINARY PHYLOGENETIC AND BIOGEOGRAPHIC ANALYSIS OF THE DYAKIIDAE (GASTROPODA: STYLOMMATOPHORA) AND A BIOGEOGRAPHIC ANALYSIS OF OTHER SUNDALAND TAXA.

Abstract

- The phylogeny of the Dyakiidae, an early diverging lineage of the Limacoidea sensu lalo, is reconstructed. In the Dyakiidae a unique transformation series of different genital accessory organs, the so-called "stimulators", is preserved which is an important argument for the hypothesis that the different stimulator types of the Stylommatophora are homologous. The biogeographic distribution patterns of the genera of the Dyakiidae are summarized and the ancestral areas of the major clades are analysed. The analysis of the area cladograms of the Dyakiidae and of several butterfly and heteroptera genera occurring in Sundaland revealed neither a general pattern of relationship between the areas of endemism in Sundaland, nor a general pattern of relationship between Sundaland and other areas. The area cladogram of the rather immobile Dyakiidae endemic to Sundaland might reflect older events than the area cladograms of the more mobile and widespread butterfly and plant bug genera. The general incompatibility of the area cladograms involving Sundaland taxa suggests that dispersal across barriers has played a major role in the historical biogeography of the analysed groups and challenges the hypothesis of vicariance biogeography that the distribution patterns of organisms are largely due to the fragmentation of an ancestral biota.