Associations of variable coloration with nich breadth and conservation status among Australian reptiles

School of Pure and Applied Natural Sciences, University of Kalmar, SE-391 82 Kalmar, Sweden.
Ecology (Impact Factor: 4.66). 06/2008; 89(5):1201-7. DOI: 10.1890/07-1670.1
Source: PubMed


We evaluate predictions concerning the evolutionary and ecological consequences of color polymorphisms. Previous endeavors have aimed at identifying conditions that promote the evolution and maintenance within populations of alternative variants. But the polymorphic condition may also influence important population processes. We consider the prediction that populations that consist of alternative "ecomorphs" with coadapted gene complexes will utilize more diverse resources and display higher rates of colonization success, population persistence, and range expansions, while being less vulnerable to range contractions and extinctions, compared with monomorphic populations. We perform pairwise comparative analyses based on information for 323 species of Australian lizards and snakes. We find that species with variable color patterns have larger ranges, utilize a greater diversity of habitat types, and are underrepresented among species currently listed as threatened. These results are consistent with the proposition that the co-occurrence of multiple color variants may promote the ecological success of populations and species, but there are also alternative interpretations.

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Available from: Anders Forsman
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    • "By largely failing to address animal camouflage, wildlife biologists may be ignoring aspects of the habitat that have important conservation implications. For example, reptiles with more variable color patterns that use a wider range of habitats are less likely to have threatened conservation status (Forsman and Aberg 2008). A possible explanation is that variable coloration confers crypsis in a wider range of habitats or less variation reduces crypsis thereby causing fitness consequences. "
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    ABSTRACT: Camouflage via animal coloration and patterning is a broadly important antipredator strategy. Behavioral decision making is an influential facet of many camouflage strategies; fitness benefits often are not realized unless an organism selects suitable backgrounds. Controlled experimental studies of behavioral strategies in selection of backgrounds conferring camouflage, however, are rarely paired with observations of wild populations. In order to investigate how substrate composition influenced habitat preference and selection by juvenile desert tortoises (Gopherus agassizii), we completed a manipulative experiment in captivity and an observational study in the wild. In our captive experiment, we found that tortoises spent a greater portion of their time near rocks. We similarly found that wild tortoises preferentially placed themselves in areas with equivalent or larger-sized rocks. Additionally, juvenile tortoises were found to be less detectable on rock substrate by observers than they were on substrate-lacking rocks. We hypothesize that rocks improve juvenile tortoise camouflage and thus that tortoises select for habitat containing rock substrate, in part, due to a survival advantage conferred by such use. The desert tortoise is a threatened species, and the present study provides a model for examining the intersection between behavior and conservation, with implications for how suitable habitat is defined and measured in species conservation programs.
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    • "Under some conditions, genetic incompatibilities and positive frequency-dependent selection arising from correlational selection and assortative mating are predicted to lead to the loss of morphs (Kirkpatrick and Nuismer 2004). Loss of morphs could, in turn, reduce the population's niche breadth (Forsman and Aberg 2008) or possibly contribute to socially mediated speciation if allopatric populations fix for different morphotypes (West-Eberhard 1986; Corl et al. 2010; Hugall and Stuart-Fox 2012). Whether polymorphic populations can remain stable over long time periods may depend critically on the relative strengths of correlational selection, which tends to destabilize polymorphism through assortative mating, and negative frequency dependent selection, which promotes disassortative mating patterns that help preserve the polymorphism. "
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    ABSTRACT: Abstract Genetically determined polymorphisms incorporating multiple traits can persist in nature under chronic, fluctuating, and sometimes conflicting selection pressures. Balancing selection among morphs preserves equilibrium frequencies, while correlational selection maintains favorable trait combinations within each morph. Under negative frequency-dependent selection, females should mate (often disassortatively) with rare male morphotypes to produce conditionally fit offspring. Conversely, under correlational selection, females should mate assortatively to preserve coadapted gene complexes and avoid ontogenetic conflict. Using controlled breeding designs, we evaluated consequences of assortative mating patterns in color-polymorphic side-blotched lizards (Uta stansburiana), to identify conflict between these sources of selection. Females who mated disassortatively, and to conditionally high-quality males in the context of frequency-dependent selection, experienced highest fertility rates. In contrast, assortatively mated females experienced higher fetal viability rates. The trade-off between fertility and egg viability resulted in no overall fitness benefit to either assortative or disassortative mating patterns. These results suggest that ongoing conflict between correlational and frequency dependent selection in polymorphic populations may generate a trade-off between rare-morph advantage and phenotypic integration and between assortative and disassortative mating decisions. More generally, interactions among multiple sources of diversity-promoting selection can alter adaptations and dynamics predicted to arise under any of these regimes alone.
    Full-text · Article · Aug 2014 · The American Naturalist
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    • "Because color morphs may be adapted to alternative ecological conditions, color polymorphism may allow species to expand their distribution to a larger range of habitat types and climatic conditions compared to monomorphic species (Forsman and Aberg, 2008). For example, in the Northern hemisphere , various polymorphic taxa reach more northerly geographic regions, exploit more diverse habitats, and exhibit broader geographic ranges than monomorphic species (Forsman et al., 2008; Galeotti and Rubolini, 2004). "
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