High-mountain summits in tropical regions are habitat islands that provide refugia for
northern taxa and opportunities for speciation. These focal hotspots of biodiversity are also
threatened by increasing anthropogenic pressures and changing climatic conditions. The
largest species group of black flies, the Simulium vernum group, reaches its southern limit in
the mountains of Southeast Asia, providing an opportunity to examine macrogenetic
diversification at the southern edge of the group's range. We investigated the polytene …