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Many animals provide parental care to offspring. Parental sex-roles vary extensively across taxa, and such patterns are considered well documented. However, information on amphibians is lacking relative to other vertebrate groups. We combine natural history observations with functional and historical analyses to examine the evolution of egg care in glassfrogs (Centrolenidae). Parental care was considered rare and predominately provided by males. Our field observations of 40 species revealed that care occurs throughout the family, and the caregiving sex changes across lineages. We discovered that a brief period of maternal care is widespread and occurs in species previously thought to lack care. Using a combination of female-removal experiments, prey-choice tests with egg-eating katydids, and parental disturbance-tolerance assays, we confirm the adaptive benefits of short-term maternal care in wild Cochranella granulosa and Teratohyla pulverata. To examine historical transitions between caregiving sexes, we assembled a molecular phylogeny and estimated ancestral care states using our data and the literature. We assessed patterns indicative of sex-specific constraints by testing whether transitions between the sexes are associated with changes in care levels. Our analyses support that male-only care evolved 2-3 times from female-only care, and this change is associated with substantial increases in care levels - a pattern supporting the hypothesis that male-only care evolved via constraints on maternal expenditure. Many groups of amphibians remain poorly studied, with emerging evidence indicating that care patterns are more diverse than currently appreciated. Natural history remains fundamental to uncovering this diversity and generating testable hypotheses of sex-role evolution.

Peru is well known for amphibian diversity and endemism, yet there have been relatively few field studies of glassfrog (Centrolenidae) diversity in this country. Research in Colombia and Ecuador indicates that centrolenid diversity is higher in the northern Andes. However, part of this trend appears to be due to sampling effort. We conducted fieldwork throughout northern Peru, and based on phylogenetic analysis of DNA sequences, combined with bioacoustic and morphological analyses of new and available material we now recognize 33 species from the country (versus 30 species prior to this work). Field surveys led to the discovery of four remarkable species: Centrolene charapita new species is a large, ornamented glassfrog that appears to be sister to Ce. geckoideum; Chimerella corleone new species represents the second-known member of the genus Chimerella; Cochranella guayasamini new species is the second-known member of the genus with humeral spines; and Hyalinobatrachium anachoretus new species occurs in the cloud forest of the east-Andean versant in Peru. In addition to the new species described here, we provide new country records, new localities including range extensions of up to 875 km, information on diagnostic characters and phylogenetic relationships, call and larval descriptions, and observations on natural history for several Peruvian centrolenids. Our results also revealed several taxonomic problems concerning species of the genus Rulyrana, and we conclude that R. croceopodes and R. tangarana are junior synonyms of R. saxiscandens. By implication of our phylogenetic analyses, we recognize the following new combinations: Espadarana audax new combination, Espadarana durrelorum new combination, and Espadarana fernandoi new combination.

Many animals improve offspring survival through parental care. Research on coevolution between parents has provided key insight into the genesis and maintenance of biparental care. However, understanding family dynamics more broadly requires assessing potential male-female coevolutionary processes in the more widespread and common context of

Both parental care and hatching plasticity can improve embryo survival. Research has found that parents can alter hatching time owing to a direct effect of care on embryogenesis or via forms of care that cue the hatching process. Because parental care alters conditions critical for offspring development, hatching plasticity could allow embryos to exploit variation in parental behaviour. However, this interaction of parental care and hatching plasticity remains largely unexplored. We tested the hypothesis that embryos hatch early to cope with paternal abandonment in the glassfrog Hyalinobatrachium fleischmanni (Centrolenidae). We conducted male-removal experiments in a wild population, and examined embryos' response to conditions with and without fathers. Embryos hatched early when abandoned, but extended development in the egg stage when fathers continued care. Paternal care had no effect on developmental rate. Rather, hatching plasticity was due to embryos actively hatching at different developmental stages, probably in response to deteriorating conditions without fathers. Our experimental results are supported by a significant correlation between the natural timing of abandonment and hatching in an unmanipulated population. This study demonstrates that embryos can respond to conditions resulting from parental abandonment, and provides insights into how variation in care can affect selection on egg-stage adaptations.

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