Genetic and phenotypic variation in a colourful treefrog across five geographic barriers

Abstract

Aim Understanding the patterns and processes underlying phenotype in a polytypic species provides key insights into microevolutionary mechanisms of diversification. The red‐eyed treefrog, Agalychnis callidryas, exhibits strong regional differentiation in colour pattern, corresponding to five admixed mitochondrial DNA clades. We evaluated spatial diversity patterns across multiple, putative barriers to examine the fine‐scale processes that mediate phenotypic divergence between some regions while maintaining homogeneity between others. Location We examined patterns of phenotypic diversification among 17 sites that span five putative biogeographic barriers in lower Central America (Costa Rica and Panama). Methods We tested the extent to which genetic distance (FST) derived from six multilocus nuclear genotypes covaried with measures of phenotypic distance (leg coloration) within and between biogeographic regions. We used linear regression analyses to determine the role of geographic and genetic factors in structuring spatial patterns of phenotypic diversity. Results The factors that best explained patterns of phenotypic diversity varied among biogeographic regions. We identified one geographic barrier that impeded gene exchange and resulted in concordant phenotypic divergence across the Continental Divide, isolating Caribbean and Pacific populations. Across Caribbean Costa Rican populations, one barrier structured phenotypic but not genetic diversity patterns, indicating a role for selection. In other regions, the putative barriers had no determining effect on either genetic or leg colour structure. Main conclusions The processes mediating the distribution and diversification of colour pattern in this polytypic, wide‐ranging treefrog varied among biogeographic regions. Spatially varying selection combined with the isolating effects of geographic factors probably resulted in the patchy distribution of colour diversity across Costa Rican and Panamanian populations.

Uniformity in premating reproductive isolation along an intraspecific cline

“…We chose 3 populations for this study and refer to them according to relative location along the cline: north, central, and south ( Figure 1 ). Across these 3 focal populations, color pattern, and call show discordant patterns of diversity ( Figures 1 and 2 ): color pattern changes abruptly between the northern and central populations, with a more gradual change between central and southern populations ( Robertson and Robertson 2008 ; Robertson and Vega 2011 ), while male advertisement call exhibits a relatively small change between northern and central populations, but large differences between central and southern populations ( Akopyan et al 2017 ).…”

“…The red-eyed treefrog Agalychnis callidryas ( Cope 1862 ) is a broadly distributed Neotropical frog ranging from southern México to Colombia with a nearly continuous distribution along the Caribbean versant of the Talamanca mountains ( Savage 2002 ). Populations from northeastern Costa Rica to central Panamá exhibit population divergence in multiple traits, including color pattern ( Robertson and Vega 2011 ), genotype ( Robertson et al 2009 ), body size ( Robertson and Robertson 2008 ), male advertisement call ( Akopyan et al 2017 ), and antimicrobial skin peptides ( Davis et al 2016 ). We focus on color pattern and male advertisement call in this study as they are well established social signals important in communication in anurans ( Ryan and Rand 1993 ; Summers et al 1999 ; Ryan 2001 ; Taylor et al 2007 ; Gomez et al 2009 ).…”

Non-Invasive Measurement of Frog Skin Reflectivity in High Spatial Resolution Using a Dual Hyperspectral Approach

“…Adult specimens exhibit a bright, highly saturated green dorsal coloration with blue to orange striped patterns on cream white flanks. This pattern is highly variable among populations [38]–[40]. Exposed to direct sunlight A. callidryas might depict a whitish color [41].…”

Host Defense Skin Peptides Vary with Color Pattern in the Highly Polymorphic Red-Eyed Treefrog

“…The Talamanca Mountain range forms the continental divide, extends 400 km along the length of Costa Rica and Western Panama (Figure 1; Kohlmann et al, 2002;Savage, 2002) and imposes strong distributional limits for certain terrestrial amphibians, reptiles, and insects (Zamudio and Greene, 1997;Wiens, 2000;Kohlmann et al, 2002;Crawford, 2003;Zeh et al, 2003). The Talamanca uplift is a strong barrier associated with genetic and phenotypic differentiation of A. callidryas populations (Robertson and Vega, 2011), however we did not find an effect of this mountain range on structuring peptide diversity. Similarly we found no evidence of a geographic barrier between northwestern and southwestern CR (Río Naranjo and Río Savegre) after accounting for genetic distance.…”

“…Quantification of peptide variation in A. callidryas has thus far been based on few individuals (n = 3-6) collected from a single population in Costa Rica (Mignogna et al, 1997), or from the commercial animal trade (Wang et al, 2008(Wang et al, , 2015Ge et al, 2014;Jiang et al, 2014). The regional diversification in other heritable phenotypic characters (body size, color pattern) and variable levels of genetic connectivity among red-eyed treefrog populations (Robertson and Robertson, 2008;Robertson and Vega, 2011) sets the stage for examining the determinants of geographic variation in skin peptides in this polymorphic species.…”