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Competing dwarf males: sexual selection in an orb‐weaving spider
Author(s) -
FOELLMER M. W.,
FAIRBAIRN D. J.
Publication year - 2005
Publication title -
journal of evolutionary biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.289
H-Index - 128
eISSN - 1420-9101
pISSN - 1010-061X
DOI - 10.1111/j.1420-9101.2005.00868.x
Subject(s) - biology , sexual selection , sexual dimorphism , mating , spider , orb (optics) , context (archaeology) , scramble competition , competition (biology) , zoology , mate choice , operational sex ratio , seasonal breeder , ecology , mating system , paleontology , artificial intelligence , computer science , image (mathematics)
Hypotheses for the adaptive significance of extreme female‐biased sexual size dimorphism (SSD) generally assume that in dimorphic species males rarely interfere with each other. Here we provide the first multivariate examination of sexual selection because of male–male competition over access to females in a species with ‘dwarf’ males, the orb‐weaving spider Argiope aurantia . Male A. aurantia typically try to mate opportunistically during the female's final moult when she is defenceless. We show that, contrary to previous hypotheses, the local operational sex ratio (males per female on the web) is male‐biased most of the season. Both interference and scramble competition occur during opportunistic mating, the former leading to significant selection for large male body size. Male condition and leg length had no effect on mating success independent of size. We discuss these findings in the context of the evolution of extreme female‐biased SSD in this clade.