The tadpole of Hylodes caete (Anura: Hylodidae), an endemic Atlantic rainforest Torrent frog of Brazil.

The genus Hylodes Fitzinger currently comprises 26 species of Torrent frogs, organized into four morphological taxonomic groups (Heyer 1982; Frost 2020): Hylodes glaber, H. lateristrigatus, H. mertensi, and H. nasus groups. Hylodes lateristrigatus is the most speciose group, comprising today 20 known species (Frost 2020). Nested in this group, a clade has been recovered based on molecular evidence, gathering the only four Hylodes species that are known to have males with nuptial thumb tubercles (de Sá et al. 2015; Malagoli et al. 2017). This well-supported clade includes H. phyllodes Heyer Cocroft, Hylodes fredi Canedo Pombal, H. pipilans Canedo Pombal, and H. caete Malagoli, de Sá, Canedo Haddad. Among these four Torrent frogs, tadpoles are unknown only for the most recently described H. caete (see tadpole descriptions in Heyer et al. 1990; Laia et al. 2010; Nogueira-Costa et al. 2019). With important taxonomic and conservation implications for the family Hylodidae (Laia Rocha 2012), we describe here the tadpole of Hylodes caete, a species endemic to the crests and slopes of Serra do Mar, State of São Paulo, southeastern Brazil (Malagoli et al. 2017). The present description is particularly important because, in its type-locality, H. caete occurs in sympatry and syntopy with H. phyllodes (Malagoli et al. 2017).

Unexpected reproductive fidelity in a polygynous frog.

Polygynous mating systems with group fidelity are a common animal organization, typically consisting of multiple females in a mated group with a single male for an extended period (sometimes referred to as harem polygyny). Single-male polygyny with reproductive fidelity occurs in invertebrates, bony fishes, and some tetrapods, such as lizards, mammals, and birds. In amphibians, reproductive fidelity in polygynous groups is not fully demonstrated. Combining data on larval development, molecular paternity assignment, and in situ behavioral observations, we reveal high fidelity during a prolonged breeding season in a Neotropical polygynous frog. Males dominate scarce breeding sites, guarding offspring, and mating exclusively with multiple females that exhibit dominance rank. This system likely evolved in response to intense competition for breeding sites and intrasexual competition for mates.

Male-male competition and repeated evolution of terrestrial breeding in Atlantic Coastal Forest frogs.

Terrestrial breeding is a derived condition in frogs, with multiple transitions from an aquatic ancestor. Shifts in reproductive mode often involve changes in habitat use, and these are typically associated with diversification in body plans, with repeated transitions imposing similar selective pressures. We examine the diversification of reproductive modes, male and female body sizes, and sexual size dimorphism (SSD) in the Neotropical frog genera Cycloramphus and Zachaenus, both endemic to the Atlantic rainforest of Brazil. Species in this clade either breed in rocky streams (saxicolous) or in terrestrial environments, allowing us to investigate reproductive habitat shifts. We constructed a multilocus molecular phylogeny and inferred evolutionary histories of reproductive habitats, body sizes, and SSD. The common ancestor was small, saxicolous, and had low SSD. Terrestrial breeding evolved independently three times and we found a significant association between reproductive habitat and SSD, with shifts to terrestrial breeding evolving in correlation with decreases in male body size, but not female body size. Terrestrial breeding increases the availability of breeding sites and results in concealment of amplexus, egg-laying, and parental care, therefore reducing male-male competition at all stages of reproduction. We conclude that correlated evolution of terrestrial reproduction and small males is due to release from intense male-male competition that is typical of exposed saxicolous breeding.

Sophisticated Communication in the Brazilian Torrent Frog Hylodes japi.

Intraspecific communication in frogs plays an important role in the recognition of conspecifics in general and of potential rivals or mates in particular and therefore with relevant consequences for pre-zygotic reproductive isolation. We investigate intraspecific communication in Hylodes japi, an endemic Brazilian torrent frog with territorial males and an elaborate courtship behavior. We describe its repertoire of acoustic signals as well as one of the most complex repertoires of visual displays known in anurans, including five new visual displays. Previously unknown in frogs, we also describe a bimodal inter-sexual communication system where the female stimulates the male to emit a courtship call. As another novelty for frogs, we show that in addition to choosing which limb to signal with, males choose which of their two vocal sacs will be used for visual signaling. We explain how and why this is accomplished. Control of inflation also provides additional evidence that vocal sac movement and color must be important for visual communication, even while producing sound. Through the current knowledge on visual signaling in Neotropical torrent frogs (i.e. hylodids), we discuss and highlight the behavioral diversity in the family Hylodidae. Our findings indicate that communication in species of Hylodes is undoubtedly more sophisticated than we expected and that visual communication in anurans is more widespread than previously thought. This is especially true in tropical regions, most likely due to the higher number of species and phylogenetic groups and/or to ecological factors, such as higher microhabitat diversity.