A molecular biogeographic analysis of the gomphocerine grasshoppers (Orthoptera: Acrididae).

摘要

The Gomphocerinae, the second most speciose subfamily of Acrididae, are distributed world-wide, occurring on all continents except Australia and Madagascar. They are commonly called the "tooth-legged" grasshoppers, owing to the presence of a row of stridulatory pegs on the inner surface of the hind femur, which distinguishes them from a sister subfamily, the Acridinae, that lack this feature. Although there has been considerable speculation on the internal organization of the Gomphocerinae, to date there has not been a large-scale testing of such speculations using molecular analysis. This study aims to examine suggested tribal affiliation of several genera and to test biogeographic hypotheses concerning connections between Eurasian, North American, South American and African members of the subfamily Gomphocerinae.; To achieve these goals, portions of four mitochondrial genes were sequenced and phylogenetically analyzed using weighted and unweighted maximum parsimony, Bayesian inference and maximum likelihood methods. Maximum resolution was found using weighted parsimony (at third codon positions only transversions were counted) and Bayesian inference. The subfamily Gomphocerinae is not monophyletic, given the occurrence of acridine grasshopper species within the subfamily. Only the tribes Scyllinini and Orphulellini were found to be monophyletic, while all other tribes (Amblytropidini Arcypterini, Aulocarini, Chyrochraontini, Compsacrini, Eritettigini, Gomphocerini, Mermirini, Parapomalini) were not monophyletic. Regarding biogeographic origins of the subfamily, our molecular data provisionally support a southern origin of the Gomphocerinae, most likely from the prehistoric continent of Gondwanaland. Multiple dispersal events occurred from South America to North America, followed by movements between Eurasia and North America. Assigning the range 50 to 100 Mya to the time of gomphocerine divergence, this thesis provides molecular clock estimates for the times of these dispersal events.