LIFETIME SELECTION ON ADULT BODY SIZE AND COMPONENTS OF BODY SIZE IN A WATERSTRIDER: OPPOSING SELECTION AND MAINTENANCE OF SEXUAL SIZE DIMORPHISM

Sexual size dimorphism (SSD), the difference in body size between males and females, is common in almost all taxa of animals and is generally assumed to be adaptive. Although sexual selection and fecundity selection alone have often been invoked to explain the evolution of SSD, more recent views ind...

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Bibliographic Details
Published in:Evolution 2000-04, Vol.54 (2), p.558-566
Main Authors: Preziosi, Richard F, Fairbairn, Daphne J
Format: Article
Language:English
Subjects:
Abdomen
Animals
Aquarius remigis
Balancing selection
Body size
episodes of selection
Evolution
Fecundity
Female
Female animals
Freshwater
Genetics
Genitalia
Gerridae
Insecta - anatomy & histology
Insecta - genetics
Insects
lifetime fitness
longevity
Male
Male animals
Mating behavior
natural selection
REGULAR ARTICLES
Selection, Genetic
Sex Characteristics
Sexual dimorphism
Sexual selection
Size
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Summary:Sexual size dimorphism (SSD), the difference in body size between males and females, is common in almost all taxa of animals and is generally assumed to be adaptive. Although sexual selection and fecundity selection alone have often been invoked to explain the evolution of SSD, more recent views indicate that the sexes must experience different lifetime selection pressures for SSD to evolve and be maintained. We estimated selection acting on male and female adult body size (total length) and components of body size in the waterstrider Aquarius remigis during three phases of life history. Opposing selection pressures for overall body size occurred in separate episodes of fitness for females in both years and for males in one year. Specific components of body size were often the targets of the selection on overall body size. When net adult fitness was estimated by combining each individual's fitnesses from all episodes, we found stabilizing selection in both sexes. In addition, the net optimum overall body size of males was smaller than that of females. However, even when components of body size had experienced opposing selection pressures in individual episodes, no components appeared to be under lifetime stabilizing selection. This is the first evidence that contemporary selection in a natural population acts to maintain female size larger than male size, the most common pattern of SSD in nature. Corresponding Editor: W. T. Starmer
ISSN:0014-3820
1558-5646
DOI:10.1554/0014-3820(2000)054[0558:LSOABS]2.0.CO;2