Sex ratio variation shapes the ecological effects of a globally introduced freshwater fish.
Sex ratio and sexual dimorphism have long been of interest in population and evolutionary ecology, but consequences for communities and ecosystems remain untested. Sex ratio could influence ecological conditions whenever sexual dimorphism is associated with ecological dimorphism in species with strong ecological interactions. We tested for ecological implications of sex ratio variation in the sexually dimorphic western mosquitofish, Gambusia affinis. This species causes strong pelagic trophic cascades and exhibits substantial variation in adult sex ratios. We found that female-biased populations induced stronger pelagic trophic cascades compared with male-biased populations, causing larger changes to key community and ecosystem responses, including zooplankton abundance, phytoplankton abundance, productivity, pH and temperature. The magnitude of such effects indicates that sex ratio is important for mediating the ecological role of mosquitofish. Because both sex ratio variation and sexual dimorphism are common features of natural populations, our findings should encourage broader consideration of the ecological significance of sex ratio variation in nature, including the relative contributions of various sexually dimorphic traits to these effects.
Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA 95060, USA dfryxell@ucsc.edu.
David C
DC
Fryxell
School of Biology and Ecology, University of Maine, Orono, ME 04469, USA.
Heather A
HA
Arnett
Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA 95060, USA.
Travis M
TM
Apgar
School of Biology and Ecology, University of Maine, Orono, ME 04469, USA.
Michael T
MT
Kinnison
Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA 95060, USA.
Eric P
EP
Palkovacs
D000818:Animals; D003532:Cyprinodontiformes / Q000502:physiology*; D017753:Ecosystem; D005260:Female; D020387:Food Chain; D005618:Fresh Water; D008297:Male; D010839:Phytoplankton; D012727:Sex Characteristics; D012744:Sex Ratio; D015048:Zooplankton
Gambusia; freshwater ecology; mosquitofish; sexual dimorphism; trophic cascade