High-Elevation Chromosomal Diversity of Black Flies(Diptera: Simuliidae) in Thailand

摘要

The highest elevations of tropical mountains, much like oceanic islands, often support disproportionatelyhigh levels of endemism, some of which is concealed as cryptic species. In a search for additional species,we explored the chromosomal diversity of three morphologically defined species of black flies known onlyfrom the upper elevations of Doi Inthanon, Thailand’s highest mountain. Analysis of the polytene chromosomesfacilitated the discovery of the previously unknown larva of Simulium kiewmaepanense Takaoka &Srisuka, permitted linkage of the formal name of S. undecimum Takaoka, Srisuka & Saeung with its previouscytological identity, and revealed cryptic species, designated A and B, within S. tenebrosum Takaoka,Srisuka & Atiporn. A probable new species of microsporidium was discovered in the larval fat body ofS. kiewmaepanense, suggesting that at least some symbiotic organisms of endemic hosts are also restrictedto Doi Inthanon. A mitochondrial DNA analysis did not distinguish the two cryptic species of S. tenebrosumdespite complete reproductive isolation chromosomally inferred from an absence of hybrids, emphasizingthe need for integrated approaches to species problems. The chromosomes of all four analyzed species weremonomorphic, or nearly so, perhaps reflecting the suppression of polymorphic inversions that otherwisewould restrict recombination needed to generate adequate variation in the peripheral environment of themountain summit.