title: Females sample more males at high nesting densities, but ultimately obtain less attractive mates.
abstract: BACKGROUND
  Sexual selection is largely driven by the availability of mates. Theory predicts that male competition and female choice should be density-dependent, with males competing more intensely at relatively high density, and females becoming increasingly discriminating when there are more males from whom to choose. Evidence for flexible mating decisions is growing, but we do not understand how environmental variation is incorporated into mate sampling strategies. We mimicked threespine stickleback (Gasterosteus aculeatus) breeding conditions in pools with high and low densities of nesting males and allowed females to search for mates to determine whether 1) mate search strategies change with the density of breeding males and 2) pre-copulatory components of mate choice (signalling, competition, search patterns, and mating decisions) are modified in parallel.
  
  
  RESULTS
  While females sampled more males at high male density, suggesting greater opportunity for sexual selection, the expanded search did not result in females choosing males with more attractive sexual signals. This is likely because red throat colouration was twice as great when half as many males competed. Instead, females chose similarly at high and low male density, using a relative strategy to compare male traits amongst potential suitors. Reduced throat colour could reflect a trade-off with costly male competition. However, we did not observe more intense competition at higher relative density. Density-dependent signalling appears largely responsible for females associating with males who have more attractive signals at low density. If we lacked knowledge of plasticity in signalling, we might have concluded that females are more discriminating at low male density.
  
  
  CONCLUSIONS
  To understand interactions between mate choice and population dynamics, we should consider how components of mate choice that precede the mating decision interact.
authors.affiliation: Department of Biological Sciences, University of Denver, 2190 E Iliff Ave., Denver, CO, 80210, USA. robin.tinghitella@du.edu.
authors.forename: Robin M
authors.initials: RM
authors.lastname: Tinghitella
authors.affiliation: School of Biological Sciences, University of Nebraska, 1044 T Street, Lincoln, NE, 68588, USA. cstehle@huskers.unl.edu.
authors.forename: Chelsea
authors.initials: C
authors.lastname: Stehle
authors.affiliation: Department of Integrative Biology and BEACON Center for the Study of Evolution in Action, Michigan State University, 288 Farm Lane, East Lansing, MI, 48824, USA. boughman@msu.edu.
authors.forename: Janette W
authors.initials: JW
authors.lastname: Boughman
mesh_terms: D000818:Animals; D005260:Female; D008297:Male; D052586:Mating Preference, Animal; D009425:Nesting Behavior; D012726:Sexual Behavior, Animal; D023701:Smegmamorpha / Q000502:physiology*