Warning Signal Brightness Variation: Sexual Selection May Work under the Radar of Natural Selection in Populations of a Polytypic Poison Frog

• Published in: The American naturalist 2013-05, Vol.181 (5), p.E116-E124
• Main Authors: Crothers, Laura R., Cummings, Molly E.
• Format: Article
• Language: English
• Subjects: Animal cognition; Animal Communication; Animal populations; Animals; Anura - genetics; Anura - physiology; Biological Evolution; Birds; Color; Colors; Crabs; Cues; E-Note; Female; Frogs; Genetic variation; Male; Male animals; Mating Preference, Animal; Phenotype; Predation; Predators; Predatory Behavior; Reflectance; Selection, Genetic; Sex Characteristics; Sexual selection; Signal detection
• ISSN: 0003-0147; 1537-5323
• DOI: 10.1086/670010

Though theory predicts consistency of warning signals in aposematic species to facilitate predator learning, variation in these signals often occurs in nature. The strawberry poison frogDendrobates pumiliois an exceptionally polytypic (populations are phenotypically distinct) aposematic frog exhibiting variation in warning color and brightness. In the Solarte population, males and females both respond differentially to male brightness variation. Here, we demonstrate through spectrophotometry and visual modeling that aposematic brightness variation within this population is likely visible to two putative predators (crabs, snakes) and conspecifics but not to the presumed major predator (birds). This study thus suggests that signal brightness withinD. pumiliopopulations can be shaped by sexual selection, with limited opportunity for natural selection to influence this trait due to predator sensory constraints. Because signal brightness changes can ultimately lead to changes in hue, our findings at the within-population level can provide insights into understanding this polytypism at across-population scales.