The migratory locust Locusta migratoria is an infamous pest insect with exceptional migratory ability – with dispersal documented over a thousand kilometers. Its distributional area is greater than that of any other locust or grasshopper, occurring in practically all the temperate and tropical regions of the eastern hemisphere. Consequently, minimal population substructuring is expected. However, in marked contrast to its high dispersal ability, three geographical subspecies have been distinguished in China, with more than nine being biologically and morphologically identified in the world. Such subspecies status has been under considerable debate.

Here it raises the questions: (1) Are the subspecific patterns morphologically identified for the migratory locust in China genetically supported; (2) How to explain the patterns in the context of biogeographic evolution, given the strong dispersal capabilities of the insect?

De-Xing Zhang's research group studied these using a molecular ecology approach, namely multilocus microsatellite genotyping analysis. They found ample genetic evidence for strong population substructure in this highly migratory insect that conforms to geography, and that the migratory locust populations in China have differentiated into three genetically distinct groups despite high dispersal capability. More importantly, genetic data identified an unexpected cryptic subdivision and demonstrated a strong affiliation of the East China locusts to those in Northwest/Northern China. This means that the locusts in the vast area of East China are not the oriental subspecies but the Asiatic subspecies. Therefore, the traditional concept on Locusta subspecies status established from Uvarov in 1930s needs to be revised. The three groups of locusts probably have separate evolutionary histories that were most likely linked to Quaternary glaciations events, and derived from different ancestral refugial populations following postglacial expansions. The current distribution pattern of the three locust groups in China may be primarily defined by adaptive differentiation coupled to Quaternary glaciations events. Their results are of general significance both for locust research and for phylogeographical study of flora and fauna in China, illustrating the potential importance of phylogeographical history in shaping the divergence and distribution patterns of widespread species with strong dispersal ability.

The above results were recently published in BMC Evolutionary Biology (Zhang DX, Yan LN, Ji YJ, Hewitt GM, Huang ZS. Unexpected relationships of substructured populations in Chinese Locusta migratoria, 2009, 28, 9:144).