The ontogeny of asymmetry in earwig forceps

Fluctuating asymmetry may play an important role in the evolution of naturally selected and secondary sexual traits. However, very little is known about how asymmetries arise or how organisms maintain symmetry during development. Here I propose three mutually exclusive patterns for the development o...

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Bibliographic Details
Published in:Evolution 1999-02, Vol.53 (1), p.157-163
Main Author: Tomkins, J.L. (University of Western Australia, Nedlands, Western Australia.)
Format: Article
Language:English
Subjects:
Anatomy & physiology
Animal reproduction
Coefficients
Compensatory growth
CRECIMIENTO
CROISSANCE
Developmental biology
Developmental instability
DEVELOPMENTAL STAGES
DIFERENCIACION SEXUAL
DIFFERENCIATION SEXUELLE
ETAPAS DE DESARROLLO
Evolution
Evolutionary genetics
FLUCTUATING ASYMMETRY
FORCEPS ASYMMETRY
FORFICULA AURICULARIA
Genetics
GROWTH
Growth traits
Insects
Instars
Male animals
Morphogenesis
MORPHOLOGY
Ontogeny
Phenotypic traits
SECONDARY SEXUAL TRAITS
SEX DIFFERENTIATION
sexual selection
STADE DE DEVELOPPEMENT
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Summary:Fluctuating asymmetry may play an important role in the evolution of naturally selected and secondary sexual traits. However, very little is known about how asymmetries arise or how organisms maintain symmetry during development. Here I propose three mutually exclusive patterns for the development of asymmetries through consecutive growth stages: (1) compensatory growth, in which growth of the shorter side is greatest at the following growth stage; (2) persistent growth, in which growth of the longer side is greatest at the following growth stage; and (3) uncorrelated growth in which growth of the following stage is unrelated to the asymmetry at the previous one. I followed the growth in the forceps of male earwigs through four successive instars. Dyar's rule was used as a null model of insect growth. In the molt from the second to third instar, asymmetries increased through uncorrelated growth and with the magnitude but not the sign expected from Dyar's rule. However, following this, at the molts between instars 3-4 and 4-5, compensatory growth maintained asymmetries at a lower level than expected from Dyar's rule. Although there was no reduction in the absolute magnitude of asymmetry, relative asymmetry did decline. The net growth of forceps length did not follow Dyar's rule. The interpretation of patterns of growth were more sensitive and informative than the interpretation of the relations between asymmetries at consecutive instars.
ISSN:0014-3820
1558-5646
DOI:10.1111/j.1558-5646.1999.tb05341.x