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Food and sex-specific growth strategies in a spider


Uhl, Gabriele; Schmitt, Sandra; Schäfer, Martin A; Blanckenhorn, Wolf U (2004). Food and sex-specific growth strategies in a spider. Evolutionary Ecology Research, 6:523-540.

Abstract

Growth patterns are expected to differ between environments and between the sexes if there is sexual dimorphism, the general view being that male growth strategies are primarily sexually selected whereas female growth strategies are fecundity selected. We investigated the effects of food on sex-specific growth in the cellar spider Pholcus phalangioides, a sexually dimorphic spider with larger males than females. In a full sib design, 1164 offspring of 39 once-mated females were reared to sexual maturity under two feeding regimes. Food level had strong positive effects on (1) offspring body size, with males growing larger than females, and (2) offspring mass, with females maturing heavier than males; it had negative effects on (3) development time for males but not females. Males matured before females under unlimited food conditions. Analysing the entire ontogeny revealed that until the last instar, both sexes were equally retarded in development by food limitation, males lagging behind females. During the last instar, the picture reversed: development time of males was equally long at high and low food, while females had extremely long development at high food and abbreviated development at low food. We conclude that females are selected to increase mass and hence fecundity, while sexual selection apparently favours larger males but at the same time earlier maturity (i.e. protandry). Achieving both was only possible when food was plentiful, and is facilitated by a low genetic correlation between development time and body size. We found high genetic variation, as well as genotype–environment interactions, for size, mass, development time and growth rate, and consequently high full-sib but lower parent–offspring (size only) heritabilities. Genetic variation was not greater under food stress but genetic covariation was.

Abstract

Growth patterns are expected to differ between environments and between the sexes if there is sexual dimorphism, the general view being that male growth strategies are primarily sexually selected whereas female growth strategies are fecundity selected. We investigated the effects of food on sex-specific growth in the cellar spider Pholcus phalangioides, a sexually dimorphic spider with larger males than females. In a full sib design, 1164 offspring of 39 once-mated females were reared to sexual maturity under two feeding regimes. Food level had strong positive effects on (1) offspring body size, with males growing larger than females, and (2) offspring mass, with females maturing heavier than males; it had negative effects on (3) development time for males but not females. Males matured before females under unlimited food conditions. Analysing the entire ontogeny revealed that until the last instar, both sexes were equally retarded in development by food limitation, males lagging behind females. During the last instar, the picture reversed: development time of males was equally long at high and low food, while females had extremely long development at high food and abbreviated development at low food. We conclude that females are selected to increase mass and hence fecundity, while sexual selection apparently favours larger males but at the same time earlier maturity (i.e. protandry). Achieving both was only possible when food was plentiful, and is facilitated by a low genetic correlation between development time and body size. We found high genetic variation, as well as genotype–environment interactions, for size, mass, development time and growth rate, and consequently high full-sib but lower parent–offspring (size only) heritabilities. Genetic variation was not greater under food stress but genetic covariation was.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Scopus Subject Areas:Life Sciences > Ecology, Evolution, Behavior and Systematics
Language:English
Date:2004
Deposited On:22 Aug 2019 11:56
Last Modified:13 May 2020 23:10
Publisher:Evolutionary Ecology Ltd
ISSN:1522-0613
OA Status:Green

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