Meeting Abstract
Locusts are grasshoppers (Acrididae) that form large migratory swarms or marching bands, and show density-dependent phase polyphenism. This polyphenism consists of two phases, a solitarious and a gregarious phase, which manifest in response to low and high population density, respectively. The two phases differ in several traits, including behavior, morphology, nymphal coloration, physiology and reproduction. Moreover, recent studies have shown clear molecular differences between both phases in two well-studied locust species, Schistocerca gregaria and Locusta migratoria. From a phylogenetic perspective, locusts are rare among grasshoppers, representing only 19 species out of 6700 species, and they are phylogenetically heterogenous group, which strongly suggests that locust phase polyphenism convergently evolved multiple times. The genus Schistocerca contains three swarming locust species and more than 40 non-swarming sedentary species, and its phylogeny is well understood. In this study, we focus on the Central American locust (S. piceifrons) and three closely related non-swarming grasshoppers that, together, form a spectrum in the degree of density-dependent phenotypic plasticity. We quantified density-dependent reaction norms in S. piceifrons and these three related species at a behavioral, morphological and molecular level by rearing them in isolated and crowded conditions. We establish that the spectrum of density-dependent phenotypic plasticity in this clade does not only extend to the behavioral and morphological level, but also to the molecular level. Further, our transcriptome analysis points towards clear similarities and differences in gene expression patterns among these four species. Finally, we compare and contrast our results in S. piceifrons to what is known from other locust species.
