Predation and the Maintenance of Color Polymorphism in a Habitat Specialist Squamate

Abstract

Multiple studies have addressed the mechanisms maintaining polymorphism within a population. However, several examples exist where species inhabiting diverse habitats exhibit local population-specific polymorphism. Numerous explanations have been proposed for the maintenance of geographic variation in color patterns. For example, spatial variation in patterns of selection or limited gene flow can cause entire populations to become fixed for a single morph, resulting in separate populations of the same species exhibiting separate and distinct color morphs. The mottled rock rattlesnake (Crotalus lepidus lepidus) is a montane species that exhibits among-population color polymorphism that correlates with substrate color. Habitat substrate in the eastern part of its range is composed primarily of light colored limestone and snakes have light dorsal coloration, whereas in the western region the substrate is primarily dark and snakes exhibit dark dorsal coloration. We hypothesized that predation on high contrast color and blotched patterns maintain these distinct color morphs. To test this we performed a predation experiment in the wild by deploying model snakes at 12 sites evenly distributed within each of the two regions where the different morphs are found. We employed a 2×2 factorial design that included two color and two blotched treatments. Our results showed that models contrasting with substrate coloration suffered significantly more avian attacks relative to models mimicking substrates. Predation attempts on blotched models were similar in each substrate type. These results support the hypothesis that color pattern is maintained by selective predation.

Trade-off between camouflage and sexual dimorphism revealed by UV digital imaging: the case of Australian Mallee Dragons (Ctenophorus fordi)

“…Predation studies implementing experiments and models in different animal groups have shown that conspicuous individuals suffer higher predation than their counterparts, thus suggesting that natural selection should favour concealing colour patterns (StuartFox et al, 2003;Husak et al, 2006;Vignieri et al, 2010;Farallo and Forstner, 2012). However, mate choice experiments with fish, birds and reptiles have demonstrated the importance of visual signals produced by bright and colourful ornaments for mate preference and its role as an indicator of phenotypic quality (Beausoleil et al, 2012;Miyagi et al, 2012;Simons et al, 2012;Pérez i de Lanuza et al, 2013).…”

Dorsal colour pattern variation in Eurasian mountain vipers (genus Montivipera): A trade-off between thermoregulation and crypsis

“…There are examples of relationships between reptile colour patterns and substrate colour (e.g., Vincent, 1982;Stuart-Fox et al, 2004;McGaugh, 2008;Micheletti et al, 2012;Farallo & Forstner, 2012). Cryptic colour patterns may help to avoid detection by predators (Farallo & Forstner, 2012) and by prey (Götmark, 1987).…”

“…Cryptic colour patterns may help to avoid detection by predators (Farallo & Forstner, 2012) and by prey (Götmark, 1987). Although there is some evidence of disruptive colouration function of the viperzigzag patterns (Edmunds 1974;Shine &Harlow, 1998), it has been shown that even vipers with an aposematic colour pattern (see Andrén & Nilson 1981;Forsman 1995;Lindell & Forsman 1996;Wüster et al, 2004;Niskanen & Mappes, 2005;Valkonen et al, 2011;Santos et al, 2014) can appear cryptic against their natural background from a distance (Sherratt & Beatty 2003;Tullberg, Merilaita & Wiklund, 2005).…”

“…Among visual effects, crypsis may represent the major function (and hence selective pressure) explaining the adaptive nature of colour pattern variation (Vincent, 1982). There are numerous examples of cryptic colour and pattern in reptiles (Brodie, 1992;King, 1992;Shine et al, 1998;Wilson et al, 2006;Farallo & Forstner, 2012;Isaac & Gregory, 2013). Aposematism, the use of bright colours and patterns by noxious animals to deter predators, is documented in reptiles too (Campbell & Lamar, 1989;Savage & Slowinski, 1992;Brodie 1993;Brodie & Janzen, 1995;Valkonen et al, 2011).…”

Polychromatism of populations of Corallus hortulanus (Squamata: Boidae) from the southern Amazon Basin, Brazil

“…Such phenotypic variation can be explained by a set of environmental factors, which may influence its behavior and gene flow rate among populations (Henderson 1997). According to some studies, its polymorphism may be linked to different variables such as behavior, thermoregulation, metabolism, interactions with environment, predator-prey interactions through mimicry, aposematism and camouflage, and higher occupancy of habitat; besides indicating resilience/ age of the species (Terribile et al 2009;Farallo and Forstner 2012;Pizzatto and Dubey 2012).…”