The Evolution of Wing Dimorphism in Insects

Abstract

Abstract. -Wing-dimorphic insects are excellent subjects for a study of the evolution of dispersal since the nondispersing brachypterous morph is easily recognized. The purpose of this paper is to develop a framework within which the evolution ofwing dimorphism can be understood. A review ofthe literature indicates that the presence or absence of wings may be controlled by a single locus, two-allele genetic system or a polygenic system. Both types of inheritance can be subsumed within a general threshold modeL An increase in the frequency of a brachypterous morph in a population may result from an increased relative fitness of this morph or the emigration of the macropterous type. The abundance ofwing-polymorphic species argues for an increased fitness of the brachypterous form. An analysis of the life-history characteristics of 22 species of insects indicates that the brachypterous morph is both more fecund and reproduces earlier that the macropterous morpho Unfortunately, data on males are generally lacking.It is suggested that suppression ofwing production results when some hormone, perhaps juvenile hormone, exceeds a threshold value during a critical stage of development. Further, it is known that in the monomorphically winged species Oncopeltus fasciatus both flight and oviposition are regulated by the titer of juvenile hormone. These observations are used to construct a possible pathway for the evolution ofwing dimorphism. This suggests that evolution to a dimorphic species requires both an increase in the rate of production of the wing suppressing hormone and a change in the threshold level at which wing and wing-muscle production are suppressed. The stage in this evolutionary sequence that an organism will reach depends on the stability of the habitat.

Intercastes, intermorphs, and ergatoid queens: who is who in ant reproduction?

“…A, and apparently also in Leptothorax sphagnicolus (Buschinger and Francoeur, 1991), queen polymorphism thus appears to be genetically controlled in a way similar to genetically mediated wing polymorphism in numerous non-social insects (Roff, 1980(Roff, , 1990. There is no evidence that intermorphic queens in formicoxenine ants evolved from developmental peculiarities.…”

Variation in propensity to defend by reproductive gall morphs in two species of gall-forming thrips

“…This casts some doubt on the link between morphology and defensive behaviour and there are reasons to believe that many morphological features of soldiers instead represent adaptations to non-dispersal, rather than defence. For example, three features of thrips soldiers, reduced antennae, reduced or absent wings, and decreased melanization of cuticle, are common features in non-dispersing morphs in diverse insect groups (Harrison, 1980;Roff, 1986;Roff and Fairbairn, 1991;Roff and Bradford, 1996;Roff et al, 1999;Kranz et al, 2001).…”

Alternative reproductive tactics in females: the case of size polymorphism in winged ant queens

“…These, if existing long enough, will eventually be reflected by correlated phenotypes. This reasoning explains the evolution of wing polymorphisms in insects in general (Roff, 1986) and in some ant species in particular (Buschinger and Heinze, 1992;Heinze and Tsuji, 1995). It can be extended to queen size polymorphisms in ants, with microgynes providing the means for successfully exploiting the local patch by budding, as do wingless, intermorphic queens in wing-polymorphic species (Briese, 1983;Heinze, 1993a).…”

“…This system of female polymorphism is probably stable because male-like females evade sexual harassment at high male concentrations but have lower mating chances when males are scarce (Hinnekint, 1987; for an alternative view see Johnson, 1975). The evolution of an alternative form of non-dispersing females in insects is often linked to the loss or the reduction of wings (aptery and brachyptery; Braune, 1983;Roff, 1986) but not always (e.g., Lindquist and Walter, 1988). In some cases, such as the cricket Gryllus firmus a central trade-off between fecundity and dispersion capability appears to be responsible for the reduction of wings (Roff, 1984).…”