Density-Dependent Phase Polyphenism in Nonmodel Locusts: A Minireview

Hojun Song

doi:10.1155/2011/741769

Abstract

Although the specific mechanisms of locust phase transformation are wellunderstood for model locust species such as the desert locustSchistocerca gregariaand the migratory locustLocusta migratoria, the expressions of density-dependent phase polyphenism in other nonmodel locust species are not wellknown. The present paper is an attempt to review and synthesize what we know about these nonmodel locusts. Based on all available data, I find that locust phase polyphenism is expressed in many different ways in different locust species and identify a pattern that locust species often belong to large taxonomic groups which contain mostly nonswarming grasshopper species. Although locust phase polyphenism has evolved multiple times within Acrididae, I argue that its evolution should be studied from a phylogenetic perspective because I find similar density-dependent phenotypic plasticity among closely related species. Finally, I emphasize the importance of comparative analyses in understanding the evolution of locust phase and propose a phylogeny-based research framework.

Highlights

The contemporary definition of locusts is fairly strict and narrow
Earlier studies described the nymphs and adults to be gregarious [130, 131] and reported the migrating bands of the late instar nymphs [131]. These earlier studies led Song [4] and Pener and Simpson [2] to include C. kiangsu as one of the species exhibiting a certain level of density-dependent phase polyphenism, but there is no definitive report of this species being able to change color, morphology, or behavior in response to change in population density
I have performed a literature review focusing on locust phase polyphenism of nonmodel locust species

Summary

Introduction

The contemporary definition of locusts is fairly strict and narrow. Pener [1] defined locusts as grasshoppers that belong to Acrididae (Orthoptera: Caelifera) that meet two criteria: (1) they form at some periods dense groups comprising huge numbers, bands of hoppers, and/or swarms of winged adults which migrate; (2) they are polyphenic in the sense that individuals living separately differ in many characteristics from those living in groups. The second criterion, the expression of density-dependent phase polyphenism, is rarer [6] and has only been convincingly documented in the migratory locust, Locusta migratoria, the brown locust, Locustana pardalina, the desert locust Schistocerca gregaria, the Central American locust, S. piceifrons, the South American locust, S. cancellata, and the red locust, Nomadacris septemfasciata, and to the lesser degree in the Moroccan locust, Dociostaurus maroccanus. In these species, color, behavior, morphology, biochemistry, and life history traits are strikingly affected by the change in local population density [2]. I propose a robust research framework that incorporates a phylogenetic approach in studying the evolution of density-dependent phase polyphenism

Expression of Density-Dependent Phase Polyphenism of Nonmodel Locusts

Other Pest Grasshopper Species

Evolution of Density-Dependent Phase Polyphenism in Acrididae

Findings

Conclusion