Authors: Fairbairn D.J.; Yadlowski D.E.

Source: Journal of Evolutionary Biology, Volume 10, Number 4, July 1997 , pp. 495-513(19)

Publisher: Wiley-Blackwell

Abstract:

Migratory tendency in insects is a complex trait, composed of a suite of correlated behavioural, physiological, morphological and life history traits. We investigate the genetic and physiological basis of the coevolution of this suite of traits using laboratory lines of the wing dimorphic cricket, Gryllus firmus, selected for increasing and decreasing incidence of macroptery. Selection on wing morphology has produced strong direct responses in proportion macropterous as well as correlated (indirect) responses in wing muscle histolysis, flight propensity and fecundity. We investigate the hypothesis that these responses have been mediated by changes in the metabolism of juvenile hormone (JH) during the final nymphal stadium (the critical period for wing morph determination). Previous studies of Gryllus sp. have established that JH titre in this period is determined primarily by the activity of the degradative enzyme, juvenile hormone esterase (JHE). Assays of JHE activity in the final nymphal stadium of the replicated control and selected lines demonstrate highly significant differences in both mean activity and the probability of macroptery for a given level of activity (i.e., the threshold activity required to induce wing formation). These correlated responses in JH metabolism support the general hypothesis that the correlations among traits determining migratory tendency result at least in part from the common influence of JH during the final nymphal stadium. We discuss these results in the context of the quantitative genetic model for the evolution of polygenic, dichotomous traits (the threshold model), and present four general predictions concerning the coevolution of traits associated with ecological (i.e., trophic, life history, behavioural) dimorphisms.

Keywords: Selection; genetic correlation; wing dimorphism; juvenile hormone; Gryllus firmus

Document Type: Research article

DOI: http://dx.doi.org/10.1046/j.1420-9101.1997.10040495.x

Affiliations: 1: Department of Biology, Concordia University, 1455 de Maisonneuve Blvd., West, Montreal, Quebec H3G 1M8, Canada, Email: fairbrn@vax2.concordia.ca

Publication date: 1997-07-01

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