Not all colors are equal: predation and color polytypism in the aposematic poison frog Oophaga pumilio

Abstract

Aposematic organisms are not predicted to show high levels of warning signal diversity because they are expected to be under stabilizing selection to decrease costs of 'educating' predators about their unpalatability. However, systematic changes in warning signals (polytypism) can be expected if they represent adaptations to local predators. The aposematic strawberry poison frog (Oophaga pumilio) is red throughout its mainland distribution in Costa Rica and Panamá, but displays high levels of warning signal diversity in the Bocas del Toro Archipelago of Panamá. Both coloration and spot pattern vary in a polytypic sense. Sexual selection contributes to maintaining the polytypism, but little work has investigated the potential influence of predation. We used unspotted models of O. pumilio to determine if predation might help explain the color polytypism on Isla Colón in the Bocas del Toro Archipelago of Panamá. We tested whether attack rates differed among the red mainland morph, green/yellow Isla Colón morph, and the brown control. We found that frog color significantly predicted being attacked. The local green Isla Colón models were attacked more than foreign red or brown models. No difference in attack rate existed between red and brown control models. Our results suggest that the red mainland morph possesses a more effective warning signal, even when it is not the local morph. Honest signaling of unpalatability, neophobia, and the use of search images by local predators are potential explanations. Similarity of the brown model to other local poison frogs might explain the lower attack rate compared to previous work. The attack rate was lower on Isla Colón compared to mainland Costa Rica, which supports the hypothesis that less overall 123Evol Ecol DOI 10.1007/s10682-012-9605-z predation in the Bocas del Toro Archipelago may contribute to the overall warning signal diversity in O. pumilio there by relaxing selection for aposematic traits.

Influences of geographic differentiation in the forewing warning signal of the wood tiger moth in Alaska

“…Two recent studies of predation on polytypic and polymorphic populations of Oophaga pumilio did not find evidence that positive FDS was involved in maintaining color differences in two populations (Hegna et al 2013b, Richards-Zawacki et al 2013). However, additional investigation would be needed across the geographic distribution of Oophaga pumilio where nearly 20 polytypic morphs occur to fully understand if positive FDS maintains differences in some locations (Hegna et al 2013b). One additional explanation for why positive FDS may not always be found is that predators may generalize their avoidance of warning signals more broadly.…”

“…Some of the species found to have geographically varying warning signals include Neotropical Heliconius butterflies (Brown & Benson 1974, Brower 1996, Mallet 2010, ladybird beetles (Creed 1966, Brakefield 1985, Dolenská et al 2009, Blount et al 2012, monarch butterflies (Brower 1958, Davis et al 2005, Davis et al 2012, newts (Mochida 2009, Mochida 2011, poison frogs (Daly & Myers 1967, Savage 1968, Summers et al 2003, Wang & Summers 2010, Wang 2011, Rudh et al 2011, Maan & Cummings 2012, Willink et al 2013, RichardsZawacki et al 2013, Hegna et al 2013b), velvet ants (Wilson et al 2012), alpine leaf beetles (Borer et al 2010), and bumble bees (Plowright & Owen 1980). Interestingly, some aposematic species appear to switch between aposematic and cryptic strategies across their distributions.…”

“…In natural conditions it is thought that predator changes over the geographic distribution of the poison frog Oophaga pumilio may partly explain intra-specific color diversity of morphs (Reynolds & Fitzpatrick 2007, Hegna et al 2013b. At least two studies have found some possible taxon-specific influences.…”

“…Sexual selection is also thought to play a role in the intra-specific diversification of warning signals in the strawberry poison frog (Oophaga pumilio) (Rudh et al 2011, Cummings & Crothers 2013. Although it is well established that females prefer color morphs that are similar to their own coloration (Summers et al 1999, Maan & Cummings 2008, recent work has shown that predators may not select for local morphs on the basis of color alone (Hegna et al 2013b, Richards-Zawacki et al 2013. Instead, base coloration of O. pumilio may be related to their toxicity (Maan & Cummings 2012).…”

Reproductive isolation related to mimetic divergence in the poison frog Ranitomeya imitator

“…A number of species display remarkable intraspecific diversity in colourpattern [19][20][21][22] , although in most cases the source of divergent selection among populations is unclear [23][24][25][26][27] . In Ranitomeya imitator, intraspecific divergence in colour-pattern is associated with selection for Müllerian mimicry 28 , which led to the establishment of four distinct mimetic morphs of this species in central Peru 29 .…”