A Key Ecological Trait Drove the Evolution of Biparental Care and Monogamy in an Amphibian

Abstract

Linking specific ecological factors to the evolution of parental care pattern and mating system is a difficult task of key importance. We provide evidence from comparative analyses that an ecological factor (breeding pool size) is associated with the evolution of parental care across all frogs. We further show that the most intensive form of parental care (trophic egg feeding) evolved in concert with the use of small pools for tadpole deposition and that egg feeding was associated with the evolution of biparental care. Previous research on two Peruvian poison frogs (Ranitomeya imitator and Ranitomeya variabilis) revealed similar life histories, with the exception of breeding pool size. This key ecological difference led to divergence in parental care patterns and mating systems. We present ecological field experiments that demonstrate that biparental care is essential to tadpole survival in small (but not large) pools. Field observations demonstrate social monogamy in R. imitator, the species that uses small pools. Molecular analyses demonstrate genetic monogamy in R. imitator, the first example of genetic monogamy in an amphibian. In total, this evidence constitutes the most complete documentation to date that a single ecological factor drove the evolution of biparental care and genetic and social monogamy in an animal.

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

“…To address the role of assortative mating, we conducted triad mate-choice experiments in which we introduced two females (one of each morphs) into the terrarium of a given male, and measured the amount of courtship time between the male and female. This is equivalent to a mutual choice test, which is appropriate here as R. imitator is monogamous 36 , and therefore both sexes should be choosy. We tested preferences in three populations: striped allopatric, striped transition and varadero, allowing us to address two questions (1) whether courtship preferences differ between the stripedtransition and varadero populations, and (2) whether courtship preferences differ among the two populations of the striped morph.…”

Experimental evidence for predator learning and Müllerian mimicry in Peruvian poison frogs (Ranitomeya, Dendrobatidae)

“…Frogs of the genus Ranitomeya appear to eat primarily ants (AMMS, unpublished data) which are extremely chitinous and likely energetically expensive to digest. A decrease in consumption of costly prey items, prey specialization, or toxin sequestration could allow more energy to be directed towards the energetically expensive process of monogamous biparental care (Brown et al 2010;Tumulty et al in press). Future work should test the efficacy of this hypothesis.…”

Benefits and costs of parental care

“…In tree frogs, the location of enough large water pools for egg deposition favours tadpole development (e.g. Brown et al 2010), whereas the parents of some crab and fish species enhance survival by oxygenating eggs via fanning (e.g. Baeza and Fernandez 2002;Green and McCormick 2005).…”