Speciation of Phlebotomus sandflies of the subgenus Larroussius coincided with the late Miocene-Pliocene aridification of the Mediterranean subregion

Abstract

The phylogeny and mode of speciation of Mediterranean Phlebotomus of the subgenusLarroussius were inferred by comparative sequence analyses of a fragment of mitochondrial DNA (Cytochrome b) and of a nuclear gene (Elongation factor alpha). The molecular phylogenies were congruent basally, where their clades matched the species complexes defined by a few genitalic characters of each sex. Reticulate evolution was suggested for the most derived species complex (Phlebotomus perniciosus): the molecular phylogenies were incongruent, and mitochondrial-marker distribution was consistent with introgressive hybridizations not between sister species but between species whose ranges now overlap or abut. By considering the molecular phylogenies, the mitochondrial molecular clock and the ecological niches of the species, as well as the historical biogeography and palaeoecology of the Mediterranean subregion, we propose that the derived lineages arose from a sequential series of speciation events associated with habitat shifts promoted by progressive aridification. This «taxon pulse»-like speciation occurred in the Pliocene, later than previously proposed in a vicariance hypothesis that invoked only tectonic events, but too early for Pleistocene Ice-age refugia to have played any role other than the isolation of geographical races. Speciation occurred before the proposed divergence of members of the Leishmania donovani complex and this helped to rule out any vector-parasite co-speciation or co-cladogenesis.