Aim

Amphibians exhibit unusually diverse reproductive modes, including a wide array of parental care strategies. The evolutionary drivers of this diversity, however, remain unclear. Here we investigate three major factors which may predict interspecific variation in parental care strategies: climate, intrasexual selection and social environment. We hypothesise that some care forms evolved to cope with harsh conditions such as dry or unpredictable habitats. We contrast this prediction with the hypothesis that parental roles have coevolved with the social environment and mating systems. 

Location

Global.

Major taxa studied

Frogs and toads (Anura, Amphibia).

Time period

Extant taxa that represent approximately 220 million years of evolutionary history

Methods

Using geographic and behavioural data for 971 species of frogs and toads that represent 45 anuran families, we quantify the global distribution of four forms of parenting separately for males and females: nest building, nest and/or tadpole attendance, carrying and nourishment. We use phylogenetic comparative analyses to investigate whether climate, social environment and mating systems predict interspecific variation in parental care.

Results

Our results show that climatic effects contribute to parental care diversity: under cool and humid climates males provide offspring attendance, while endotrophy, whereby the female provides all nutrients for the offspring until metamorphosis, occurs under predictable temperatures. In addition, we found other associations between mating systems and parental care forms: uniparental clutch attendance by males is present in species with territorial defence, while cooperative nest building co-occurs with sperm competition. The type of parental care is not associated with adult sex ratios.

Main conclusions

No specific form of care is associated with hostile environments; actually, some care forms occur under beneficial conditions, while others are used independently from the climate. Instead, parenting diversity has closely coevolved with mating systems in frogs.