title: Eutrophication and predation risk interact to affect sexual trait expression and mating success.
abstract: Sexual traits are especially sensitive to low food resources. Other environmental parameters (e.g., predation) should also affect sexual trait expression by favoring investment in viability traits rather than sexual traits. We know surprisingly little about how predators alter investment in sexual traits, or how predator and resource environments interact to affect sexual trait investment. We explored how increasing phosphorous (P) availability, at a level mimicking cultural eutrophication, affects the development of sexual, nonsexual, and viability traits of amphipods in the presence and absence of predators. Sexual traits and growth were hypersensitive to low P compared to nonsexual traits. However, a key sexual trait responded to low P only when predator cues were absent. Furthermore, investment trade-offs between sexual traits and growth only occurred when P was low. The phenotypic changes caused by predator cues and increased P availability resulted in higher male mating success. Thus, eutrophication not only affects sexual trait expression but also masks the trade-off between traits with similar P demand. Sensitivity of sexually selected traits to changes in P, combined with the important roles these traits play in determining fitness and driving speciation, suggests that human-induced environmental change can greatly alter the evolutionary trajectories of populations.
authors.affiliation: Department of Biological Sciences and Pymatuning Laboratory of Ecology, University of Pittsburgh, 4249 Fifth Ave., Pittsburgh, Pennsylvania15260 E-mail: rdc28@pitt.eduDepartment of Zoology, Oklahoma State University, 501 Life Sciences West, Stillwater, Oklahoma 74078.
authors.forename: Rickey D
authors.initials: RD
authors.lastname: Cothran
authors.affiliation: Department of Biological Sciences and Pymatuning Laboratory of Ecology, University of Pittsburgh, 4249 Fifth Ave., Pittsburgh, Pennsylvania15260 E-mail: rdc28@pitt.eduDepartment of Zoology, Oklahoma State University, 501 Life Sciences West, Stillwater, Oklahoma 74078.
authors.forename: Andy R
authors.initials: AR
authors.lastname: Stiff
authors.affiliation: Department of Biological Sciences and Pymatuning Laboratory of Ecology, University of Pittsburgh, 4249 Fifth Ave., Pittsburgh, Pennsylvania15260 E-mail: rdc28@pitt.eduDepartment of Zoology, Oklahoma State University, 501 Life Sciences West, Stillwater, Oklahoma 74078.
authors.forename: Punidan D
authors.initials: PD
authors.lastname: Jeyasingh
authors.affiliation: Department of Biological Sciences and Pymatuning Laboratory of Ecology, University of Pittsburgh, 4249 Fifth Ave., Pittsburgh, Pennsylvania15260 E-mail: rdc28@pitt.eduDepartment of Zoology, Oklahoma State University, 501 Life Sciences West, Stillwater, Oklahoma 74078.
authors.forename: Rick A
authors.initials: RA
authors.lastname: Relyea
mesh_terms: D033304:Amphipoda / Q000235:genetics* / Q000254:growth & development; D000818:Animals; D003463:Cues; D005068:Eutrophication; D005260:Female; D005298:Fertility; D008297:Male; D010641:Phenotype; D010758:Phosphorus; D011235:Predatory Behavior; D012727:Sex Characteristics; D012726:Sexual Behavior, Animal
chemical_list: D010758:Phosphorus