Colour polymorphism torn apart by opposing positive frequency-dependent selection, yet maintained in space

Swanne P. Gordon*, Hanna Kokko, Bibiana Rojas, Ossi Nokelainen, Johanna Mappes

*Corresponding author for this work

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Polymorphic warning signals in aposematic species are enigmatic because predator learning and discrimination should select for the most common coloration, resulting in positive frequency-dependent survival selection. Here, we investigated whether differential mating success could create sufficiently strong negative frequency-dependent selection for rare morphs to explain polymorphic (white and yellow) warning coloration in male wood tiger moths (Parasemia plantaginis). We conducted an experiment in semi-natural conditions where we estimated mating success for both white and yellow male moths under three different morph frequencies. Contrary to expectations, mating success was positively frequency-dependent: white morph males had high relative fitness when common, likewise yellow morph males had high relative fitness when instead they were common. We hence built a model parameterized with our data to examine whether polymorphism can be maintained despite two sources of positive frequency dependence. The model includes known spatial variation in the survival advantage enjoyed by the yellow morph and assumes that relative mating success follows our experimentally derived values. It predicts that polymorphism is possible under migration for up to approximately 20% exchange of individuals between subpopulations in each generation. Our results suggest that differential mating success combined with spatial variation in predator communities may operate as a selection mosaic that prevents complete fixation of either morph.

Original languageEnglish
Pages (from-to)1555-1564
Number of pages10
JournalJournal of Animal Ecology
Volume84
Issue number6
DOIs
Publication statusPublished - 1 Nov 2015
Externally publishedYes

Keywords

  • Aposematism
  • Coloration
  • Mating success
  • Modelling
  • Predation
  • Sexual selection
  • Spatial mosaic

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