Abstract:For many frog species that aggregate around ponds or streams, chorus attendance, the percentage of time or nights a given male is present and actively calling at an aggregation, is the strongest documented predictor of inter‐male variation in reproductive success in the wild. Males are, thus, thought to compete via endurance rivalry, where available energetic reserves and individual physiology interact to determine chorus tenure. Frogs often exhibit territorial behavior within these aggregations, and territori… Show more
“…Male mate choice has never been studied for red‐eyed treefrogs, to our knowledge; however, a study of male reproductive success in a Panamanian population of red‐eyed treefrogs showed that territoriality and site‐fidelity were strong predictors of male reproductive success (Dougherty et al, 2022). Male–male competition in A. callidryas includes shaking tree limbs to displace other males and to establish territories, wrestling (Caldwell et al, 2010), and amplectant males being pushed off the backs of females by other males (D'Orgeix & Turner, 1995, personal observation).…”
Contact zones provide important insights into the evolutionary processes that underlie lineage divergence and speciation. Here, we use a contact zone to ascertain speciation potential in the red‐eyed treefrog (Agalychnis callidryas), a brightly coloured and polymorphic frog that exhibits unusually high levels of intraspecific variation. Populations of A. callidryas differ in a number of traits, several of which are known sexual signals that mediate premating reproductive isolation in allopatric populations. Along the Caribbean coast of Costa Rica, a ~100 km contact zone, situated between two phenotypically and genetically divergent parent populations, contains multiple colour pattern phenotypes and late‐generation hybrids. This contact zone provides the opportunity to examine processes that are important in the earliest stages of lineage divergence. We performed analyses of colour pattern variation in five contact zone sites and six parental sites and found complex, continuous colour variation along the contact zone. We found discordance between the geographic distribution of colour pattern and previously described genomic population structure. We then used a parental site and contact zone site to measure assortative mating and directional selection from naturally‐occurring amplectant mating pairs. We found assortative mating in a parental population, but no assortative mating in the contact zone. Furthermore, we uncovered evidence of directional preference towards the adjacent parental phenotype in the contact zone population, but no directional preference in the parent population. Combined, these data provide insights into potential dynamics at the contact zone borders and indicate that incipient speciation between parent populations will be slowed.
“…Male mate choice has never been studied for red‐eyed treefrogs, to our knowledge; however, a study of male reproductive success in a Panamanian population of red‐eyed treefrogs showed that territoriality and site‐fidelity were strong predictors of male reproductive success (Dougherty et al, 2022). Male–male competition in A. callidryas includes shaking tree limbs to displace other males and to establish territories, wrestling (Caldwell et al, 2010), and amplectant males being pushed off the backs of females by other males (D'Orgeix & Turner, 1995, personal observation).…”
Contact zones provide important insights into the evolutionary processes that underlie lineage divergence and speciation. Here, we use a contact zone to ascertain speciation potential in the red‐eyed treefrog (Agalychnis callidryas), a brightly coloured and polymorphic frog that exhibits unusually high levels of intraspecific variation. Populations of A. callidryas differ in a number of traits, several of which are known sexual signals that mediate premating reproductive isolation in allopatric populations. Along the Caribbean coast of Costa Rica, a ~100 km contact zone, situated between two phenotypically and genetically divergent parent populations, contains multiple colour pattern phenotypes and late‐generation hybrids. This contact zone provides the opportunity to examine processes that are important in the earliest stages of lineage divergence. We performed analyses of colour pattern variation in five contact zone sites and six parental sites and found complex, continuous colour variation along the contact zone. We found discordance between the geographic distribution of colour pattern and previously described genomic population structure. We then used a parental site and contact zone site to measure assortative mating and directional selection from naturally‐occurring amplectant mating pairs. We found assortative mating in a parental population, but no assortative mating in the contact zone. Furthermore, we uncovered evidence of directional preference towards the adjacent parental phenotype in the contact zone population, but no directional preference in the parent population. Combined, these data provide insights into potential dynamics at the contact zone borders and indicate that incipient speciation between parent populations will be slowed.
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