Locust Phase Polyphenism

Locusts are grasshoppers that can form dense migrating swarms through a phenomenon known as locust phase polyphenism. There had been a number of advances made in the areas of behavioral ecology, physiology, and biochemistry which helped understand the mechanism of locust swarming, but the evolutionary relationship between locusts and non-swarming relatives was not well-understood, preventing scientists to see the “big picture.” The results from my dissertation based on a morphological phylogenetic analysis suggest that the locust species within a given lineage do not necessarily form a monophyletic group, indicating that locust phase polyphenism must have evolved multiple times.

Moreover, locust species are often closely related to sedentary species that are capable of expressing density-dependent phenotypic plasticity, which has resulted in a novel hypothesis that the locust swarming is a result of a stepwise assembly of phylogenetically conserved phenotypic plasticity, evolved throughout the diversification of grasshoppers.

My current research at Texas A&M expands this work by developing a full-scale comparative study to empirically investigate the expression of phenotypic plasticity in phylogenetically close species which can ultimately pinpoint what makes grasshoppers become locusts. This work is currently supported by NSF CAREER Award. Stay tuned for more exciting findings!

Representative Papers:

  • Gotham, S and Song, H. 2013. Non-swarming grasshoppers exhibit density-dependent phenotypic plasticity reminiscent of swarming locusts. Journal of Insect Physiology. 59: 1151-1159.
  • Song, H. 2011. Density-dependent phase polyphenism in nonmodel locusts: A minireview. Psyche 2011, Article ID 741769, 16 pages. doi:10.1155/2011/741769
  • Song, H. and Wenzel, J.W. 2008. Phylogeny of bird-grasshopper subfamily Cyrtacanthacridinae (Orthoptera: Acrididae) and the evolution of locust phase polyphenism. Cladistics 24: 515-542.