Abstract
Checkerspot butterflies in the genera Euphydryas and Chlosyne exhibit phenotypic polymorphisms along a well-defined latitudinal and elevational gradient in California. The patterns of phenotypic variation in Euphydryas chalcedona, Chlosyne palla, and Chlosyne hoffmanni suggest a mimetic relationship; in addition, the specific patterns of variation in C. palla suggest a female-limited polymorphic mimicry system (FPM). However, the existence of polymorphic models runs counter to predictions of mimicry theory. Palatability trials were undertaken to assess whether or not the different color morphs of each species were distasteful or toxic to a generalized avian predator, the European starling (Sturnus vulgaris). Results indicate that the black morph of E. chalcedona is distasteful, but not toxic, to predators, while the red morph is palatable. C . hoffmanni and both color morphs of C. palla are palatable to predators. Predators that learn to reject black E. chalcedona also reject black C. palla, suggesting that the latter is a FPM of the former. C. hoffmanni does not appear to be involved in this mimetic relationship.
Highlights
Mimicry theory predicts that once a predator guild begins to associate a warning signal with a penalty of the model, individuals that exhibit the familiar aposematic phenotype will gain protection from predation and will experience increased fitness
We interpret this as an indication that C. palla and C. hoffmanni are palatable to generalized avian predators, as is the red form of E. chalcedona
Black C. palla Black E. chalcedona Red C. palla Red E. chalcedona C. hoffmani changed over time: three of the four birds learned to reject black E. chalcedona, while the fourth rejected it on day 3 but ate it on prior and subsequent days (P = 0.005)
Summary
Mimicry theory predicts that once a predator guild begins to associate a warning signal (aposematism) with a penalty (noxiousness) of the model, individuals that exhibit the familiar aposematic phenotype will gain protection from predation and will experience increased fitness. Because a fundamental tenet of Batesian mimicry holds that the mimic is detrimental to the model, as the mimic increases in abundance, a model that is able to evolve and establish a new aposematic phenotype, free of mimics, would gain a selective advantage (Turner et al 1984; Huheey 1988; Malcolm 1990; Joron and Mallet 1998).
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