A molecular phylogeographic perspective on a fifty-year-old taxonomicissue in grasshopper systematics

摘要

This paper addresses a decades-old taxonomic controversy surrounding a species in the grasshopper subfamily Melanoplinae. Melanoploid grasshoppers fall into two tribes, the Nearctic-restricted Melanoplini and the Holarctically distributed Podismini. The current view regarding one member, Bohemanella frigida, is that it belongs to the latter tribe and that North American populations were established by dispersal from Eurasia via the Bering Land Bridge. Over the past 50 years, this opinion has changed a few times; this species was once regarded as part of the tribe Melanoplini and, as such, deemed to be the only Holarctically distributed Orthopteran insect with New World antecedents. A molecular phylogenetic study of this species was thus performed to verify its phylogenetic position and to establish a probable direction of dispersal. Portions of three mitochondrial genes (cyt b, COII, and ND2) were sequenced and phylogenetically analysed using weighted and unweighted parsimony, neighbour-joining, and maximum likelihood methods. Support for the inclusion of B. frigida within the tribe Melanoplini and the use of its original name, Melanoplus frigidus, was strong using all methods. Placement in the tribe Melanoplini leads to an acceptance of an earlier hypothesis regarding direction of dispersal across the Bering Land Bridge, making this grasshopper a unique case in orthopteran insects in this respect.