Exploring Patterns of Genetic Diversity of a Malagasy Ant Species: Anochetus Madagascarensis
Madagascar is extremely diverse and imperiled. Close to 90% of all land dwelling species are endemic to Madagascar (plants, reptiles, mammals and amphibians). Understanding patterns of genetic diversity for species can aid in better conservation efforts. In this study, I focus on the endemic Malagasy ant species, Anochetus madagascarensis. By employing a broad geographic sample of this species from throughout its distribution and a multilocus genetic data set, I explored population structure and historical factors that affected these patterns. I tested hypotheses proposed to be responsible for generating population structure, and by extension the process of speciation in Madagascar, including geologically based models such as the Riverine and Watershed hypotheses and employed ecological niche modeling to test for evidence of ecologically driven speciation. Four genetic clusters were recovered using GENELAND; one found on Mayotte of the Comoros Islands, one restricted to the eastern coast of Madagascar, one on the northern tip of Madagascar and one along the western dry forests of Madagascar. I found no association between the position of watersheds and the population structure of this species. Rivers do appear to function as barriers to gene flow between the clusters, as major rivers (Sofia in the northwest, Antainambalana in the northeast and Mandrare in the southeast) were found to demarcate the boundaries of the three Malagasy genetic clusters. The persistence of interpopulation migration on the mainland confirms these entities do indeed represent a single species, but the magnitude and pattern of this migration reveals much about the migratory capabilities of this species and the factors that influence interpopulation connectivity. I found that the ecological niche of the four clusters are not identical, but are no less similar than would be expected by chance. Together, these data provide strong support for geographic (allopatric) diversification and the absence of significant ecological divergence despite the occupation of very dissimilar habitat.
Anochetus Madagascarensis, Madagascar, Ecology and Evolutionary Biology
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