The bulk of models used to understand the species diversification on Madagascar have been constructed using vertebrate taxa. It is not clear how these models affect less vagile species that may interact at a variety of spatial scales. Several studies on vertebrates have divided Madagascar into east-west bioclimatic regions, suggesting there is a fundamental division between eastern wet-adapted and western dry-adapted taxa. An alternative model of ecogeographic constraints shows a north-south division. We test whether the diversifica- tion in a small arthropod with variable degrees of dispersal conform to either model of eco- geographic constraints proposed for vertebrate taxa. Weemploy amolecular taxonomic dataset using ~2 kilobases nuDNA (Wg,LW Rh, Abd-A, 28s) and 790 basepairs mtDNA (CO1), along with geographic and habitat data, to examine the diversification patterns of the ant genus Mystrium Roger, 1862, (Subfamily Amblyoponinae) from Madagascar. The nuclear and mitochondrial phylogenies were both congruent with morphospecies as indi- cated in a recent revision of the genus. Species of Mystrium practice different colony repro- ductive strategies (winged queens vs non-winged queens). Alternate reproductive strategies led to inequalities in female dispersal ability among species, providing an addi- tional layer for examination of the impacts of vagility on divergence, especially when mea- sured using a maternally inherited locus. Mystrium species distribution patterns support these models of ecogeographic constraints. Reproductive strategy effected howMystrium mtDNA lineages were associated with large-scale habitat distinctions and various topo- graphical features. Furthermore, in some cases we find microgeographic population struc- ture which appears to have been impacted by localized habitat differences (tsingy limestone formations, littoral forest) on a scale much smaller than that found in vertebrates. The current system offers a finer scale look at species diversification on the island, and helps achieve a more universal understanding of the generation of biodiversity on Madagascar.
Graham, N. R., Fisher, B. L., & Girman, D. J. (2016). Phylogeography in response to reproductive strategies and ecogeographic isolation in ant species on Madagascar: Genus mystrium (Formicidae: Amblyoponinae). PLoS ONE, 11(1). https://doi.org/10.1371/journal.pone.0146170