| Understanding the processes that generate biodiversity is a major goal of evolutionary biology. The ultimate cause of biodiversity is the evolution of barriers to gene flow between populations of organisms, but the proximate mechanisms are often more complex. I am interested in disentangling the roles of geographic isolation and ecological selection in the diversification of a species-rich genus of tropical tephritid fruit flies. Blepharoneura are highly specialized and host specific flies; most species specialize on a single plant host and flower sex although multiple species may exploit the same resource. At one location in Peru, two plant species (two sexes - four plant niches) are host to 14 Blepharoneura species. Phylogenetic analyses of mitochondrial DNA sequences reveal that some species may be diverging as a result of shifts to new host plants (suggesting possible ecological selection acting in speciation), while other species show an apparent pattern of geographic divergence in addition to or without host shifts. To further investigate these ecological and geographic signals underlying the history of Blepharoneura speciation, more rapidly evolving molecular markers are required. Here, I use microsatellites to address this question for seven Blepharoneura species (sp1, sp4, sp8, sp10, sp21, sp28, and sp30) characterized by differing patterns of host-plant use and geographic distribution. Microsatellite data indicates patterns of ecological divergence associated with host use in at least five species (sp1, sp4, sp10, sp21, sp30) and patterns of geographic divergence in all seven species. |
