title: Coarse dark patterning functionally constrains adaptive shifts from aposematism to crypsis in strawberry poison frogs.
abstract: Ecological specialization often requires tight coevolution of several traits, which may constrain future evolutionary pathways and make species more prone to extinction. Aposematism and crypsis represent two specialized adaptations to avoid predation. We tested whether the combined effects of color and pattern on prey conspicuousness functionally constrain or facilitate shifts between these two adaptations. We combined data from 17 natural populations of strawberry poison frogs, Oophaga pumilio with an experimental approach using digitalized images of frogs and chickens as predators. We show that bright coloration often co-occurs with coarse patterning among the natural populations. Dull green frogs with coarse patterning are rare in nature but in the experiment they were as easily detected as bright red frogs suggesting that this trait combination represents a transient evolutionary state toward aposematism. Hence, a gain of either bright color or coarse patterning leads to conspicuousness, but a transition back to crypsis would be functionally constrained in populations with both bright color and coarse patterning by requiring simultaneous changes in two traits. Thus, populations (or species) signaling aposematism by conspicuous color should be less likely to face an evolutionary dead end and more likely to radiate than populations with both conspicuous color and coarse patterning.
authors.affiliation: Animal Ecology, Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden. Anna.Qvarnstrom@ebc.uu.se.
authors.forename: Anna
authors.initials: A
authors.lastname: Qvarnström
authors.forename: Andreas
authors.initials: A
authors.lastname: Rudh
authors.forename: Torkel
authors.initials: T
authors.lastname: Edström
authors.forename: Anders
authors.initials: A
authors.lastname: Ödeen
authors.forename: Hanne
authors.initials: H
authors.lastname: Løvlie
authors.forename: Birgitta S
authors.initials: BS
authors.lastname: Tullberg
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000818:Animals; D001001:Anura / Q000235:genetics*; D005075:Biological Evolution; D002489:Central America; D010858:Pigmentation / Q000235:genetics*; D011235:Predatory Behavior
keywords: Adaptive landscape; Dendrobates pumilio; amphibian; aposematism; crypsis; fitness peak shifts; warning signal