Morphometric Differentiation in a Field Population ofDichroplus maculipennis(Orthoptera: Acrididae: Melanoplinae) under Outbreak and Non-Outbreak Situations

Yanina Mariottini,María Marta Cigliano,Celeste M Scattolini,Carlos Ernesto Lange

doi:10.1665/034.024.0205

Abstract

Abstract Dichroplus maculipennis is one of the most damaging grasshopper species of Argentina. Individuals of this species at high density are historically known to show aggregation behavior and dispersal flights, attributes that might suggest that it does exhibit to some extent phase polyphenism in relation to population density. Phase polyphenism is a complex phenomenon and the amplitude of phase change is usually species-dependent. Morphological differences between gregarious and solitarious locusts can be measured and analyzed in order to characterize the phase status. The objective of this study was to evaluate morphometric differences between individuals of a D. maculipennis field population in the southern Pampas region of Argentina during non-outbreak and outbreak conditions including the magnitude of sexual size dimorphism related to variation in density. Collected individuals in the outbreak condition totaled 804 (422 females, 382 males) and those in non-outbreak condition were 325 (141 females,...

Highlights

Locusts are among the most striking examples of densitydependent phase polyphenism, a process in which solitarious and cryptically colored grasshoppers can turn into gregarious and conspicuously colored individuals in response to an increase in population density (Latchininsky 2010, Song 2011)
Morphometric differences between individuals of the same sex under different density conditions.—Principal component analyses (PCA) performed for males showed that the first three PCs accounted for 96.56% of the total variation (74.75, 15.98, and 5.84, respectively) while in females these accounted for 97.25% of the total variation (80.22, 13.14, and 3.89, respectively)
Representation from tegmina length (E) and body size (BL), while femur length (F) was the variable that most contributed to the variation of PC3 (Table 1)

Summary

Introduction

Locusts are among the most striking examples of densitydependent phase polyphenism, a process in which solitarious and cryptically colored grasshoppers can turn into gregarious and conspicuously colored individuals in response to an increase in population density (Latchininsky 2010, Song 2011). Song (2011) listed 24 Acrididae species belonging to six different subfamilies that show elements of density-dependent polyphenism Many of these species have a tendency to aggregation and migration but show rudimentary phase polyphenism, the expression of density-dependent polyphenism may be subtle and not overtly manifested as in model locusts such as Schistocerca gregaria (Forskål) and Locusta migratoria (Linnaeus) (Uvarov 1966, 1977, Jago 1985, Simpson et al 1999, Song 2011). These species may be considered as less typical locusts, aggregating grasshoppers or non-model locusts (Pener & Simpson 2009, Song 2011)

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