The Malay archipelago is a group of islands located between two continents, Asia and Australia. Most of these islands were originated during the middle Miocene (around 15 million years ago) as the product of the collision between the Australian and Philippines plates some 25 million of years ago. This group of islands is called Wallacea, in honor of Alfred R. Wallace.
It became clear that the region was a major transitional zone between two very distinct faunas, being Alfred Wallace one of the first naturalists who described such discontinuity. In addition, Wallacea was not only a “bridge” connecting two continents but provided the space for species diversification and the establishment of many different endemic taxa.
The Indo-Australian pierid genus Delias has apparently descended from Australian ancestors, which has been proposed to support a Gondwanan origin of these butterflies. Indeed, the two main hypotheses for the Australian Lepidoptera origination involve such a southern vicariance hypothesis, or the alternative dispersal from southeast Asia (Oriental region). Diversification of butterflies has also been proposed to be largely the result of Pleistocene sea level fluctuations and the temporal connection-isolation of the present-day islands. However, dated phylogenies are still needed to test such a hypothesis.
Our project for the Indo-Australian Delias butterflies includes:
- The study of its evolutionary history and biogeography (Müller et al., 2013). It has been shown by the fine-scale systematics and biogeography of the genus that the highlands of New Guinea as well as the dispersal opportunities through and within Wallacea favored the main diversification of Delias. Moreover, an Australian origin of these butterflies is plausible. Convergent evolution of wing pattern and coloration (Müllerian mimicry) has also been shown in the light of the inferred phylogeny. Finally, the hypothesis of explosive radiation during the Pleistocene Ice Ages is rejected for Delias, since most of its species diversity arose throughout the Miocene and Pliocene (some 23 to 3 million years ago).
The main aims of the work range from the clarification of the systematics and biogeography of South Pacific ants, to the elucidation of population-level ant phylogeographic patterns, as an attempt to understand the diversity and distribution of ants in Melanesia and the South Pacific.
The region consists of both insular and mainland landscapes of rather similar physical conditions, with a very dynamic geological history. Because of these characteristics and the discrete nature of islands, the signatures left by evolutionary and ecological processes can be easier to detect than in continental habitats.
Our projects for the Melanesia and South Pacific regions include:
- Reconstruction of the phylogenetic relationships among ant species within three genera, Odontomachus, Nylanderia andAcropyga, using them as models to study speciation across archipelagos and terrains of various origins. Our preliminary results showed consistent patterns in colonization routes as well as population structure across archipelagos and within New Guinea (Manuscripts in preparation).
- Population characteristics of widespread ant species and the evaluation of hypothetical dispersal routes, geological history, historical sea level fluctuations and climate changes across the South Pacific. The discovery of extensive informative polymorphisms (SNPs) using RADtags is helping to understand the population-level patterns in certain lineages.
- Population genetic patterns and phylogeography of selected ant taxa to identify potential historical and contemporary landscape configurations affecting gene flow and population structure on the island of New Guinea.
- Janda, M., Matos-Maraví, P., Borovanska, M, Zima Jr., J., Youngerman, E., Pierce, N. 2016: Phylogeny and population genetic structure of the ant genus Acropyga (Hymenoptera: Formicidae) in Papua New Guinea. Invertebrate Systematics 30(1): 28-40. doi:10.1071/IS14050
- Müller, C. J., Matos-Maraví, P. F., Beheregaray, L. B. 2013: Delving into Delias Hübner (Lepidoptera: Pieridae): fine-scale biogeography, phylogenetics and systematics of the world’s largest butterfly genus. Journal of Biogeography 40(5): 881-893. doi:10.1111/jbi.12040