Hopping out of Mindanao: Miocene-Pliocene geological processes and cross-island dispersal as major drivers of diversity for Philippine treehoppers

Aim: We investigated the biogeographical history of an endemic Philippine treehopper, Pyrgonota bifoliata (Membracidae), to test the effect of Neogene geological events and Pleistocene climate change in generating speciation within the Philippines. Location: The Philippine archipelago. Methods: Phylogenies were reconstructed based on the mitochondrial cytochrome c oxidase I subunit (cox1) and nuclear wingless (wg) genes using maximum parsimony, maximum likelihood and Bayesian criteria. Divergence times were estimated in beast based on a range of mutation rates. Ancestral ranges were reconstructed using rasp (Reconstruct Ancestral State in Phylogenies) and Bayesian stochastic search variable selection (BSSVS). Species boundaries were tested using the Bayesian general mixed Yule coalescent (bGMYC) and Bayesian phylogenetic and phylogeography (BPP) methods. Results: Pyrgonota bifoliata showed one of the lowest levels of between-Pleistocene island genetic variation among all the taxa examined. Most Pleistocene aggregate island complex (PAIC) lineages and extant P. bifoliata originated before the onset of the first extensive Pleistocene glacial cycle. Ancestral P. bifoliata originated in the late Miocene from Mindanao, followed by a sequential northwards colonization of the Visayan Islands and Luzon in the Pliocene-early Pleistocene, which coincided with the spatial reorganization of the Philippines. The statistically delimited nine provisional species of what we now view as the P. bifoliata species complex correspond to current island boundaries and specialized host plants. Main conclusions: The temporally calibrated phylogeny of P. bifoliata represents the first invertebrate study to support the hypothesis that Miocene-Pliocene geological events and consequent cross-island dispersal were pivotal promoters of species diversity in the Philippines. We hypothesize that ecological adaptation to specialized host plants, together with either local selection or genetic drift through within-island allopatric isolation, present a plausible in situ speciation mechanism for the origin of these herbivorous insects.