Evol Ecol Res 15: 667-687 (2013) Full PDF if your library subscribes.
Geographic variation in sexual signals and behaviour in two species of poison frogs
Heike Pröhl1, Beatriz Willink2 and Susanne Hauswaldt3
1Institute of Zoology, University of Veterinary Medicine, Hannover, Germany, 2Escuela de Biología, Universidad de Costa Rica, Costa Rica and 3Unit of Evolutionary Biology, Institute of Zoology, TU Braunschweig, Germany
Correspondence: H. Pröhl, Institute of Zoology, University of Veterinary Medicine, Bünteweg 17d, D-30559 Hannover, Germany.
Background: Geographic variation in sexual signals is involved in the evolution of reproductive isolation among populations. In poison frogs, acoustic as well as visual signals vary geographically and are involved in mate choice. Here we compare geographic variation in sexual signals, behavioural strategies, and population structure among two closely related species. We end by discussing the causes and consequences of this variation for the speciation process.
Question: Are differences in advertisement calls and colour pattern associated with genetic population structure or with differences in anti-predator and reproductive behaviour in two species of poison frogs.
Organisms: Strawberry poison-dart frog (Oophaga pumilio) and granular poison-dart frog (Oophaga granulifera) from Central America.
Data: Morphological measurements, advertisement calls, distribution of colour morphs, mitochondrial (Cytb) and microsatellite markers from multiple frog populations across the species range. Behavioural observations and visual contrasts (as indicators of conspicuousness) from two colour morphs in each species.
Methods: Assess genetic population structure for both species. Analyse variation of (1) advertisement call parameters, (2) size, and (3) weight in relation to different levels of genetic population structure and colour morphs. Use visual modelling to assess conspicuousness of colour morphs. Compare behaviour between colour morphs (conspicuous vs. cryptic) and species.
Conclusions: The genetic-geographic population structure, variation in advertisement calls, and coupled divergence in colour pattern and behaviour were strikingly similar in the two species. Advertisement calls varied in accordance with the genetic population structure. In contrast, most colour patterns were restricted to one derived genetic lineage and unrelated to genetic structure. Colour patterns were correlated with differences in anti-predator behaviour and it was possible to distinguish strategies between more aposematic and more cryptic morphs. Colour patterns and advertisement calls are sexual signals and involved in pre-zygotic isolation in amphibians but in Oophaga they operate independently in different geographic-genetic settings.
Keywords: acoustic signals, dendrobatid frogs, genetic divergence, natural selection, Oophaga, sexual selection, visual signals.
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