Effects of parental care on skin microbial community composition in poison frogs

Parent-offspring interactions constitute the first contact of many newborns with their environment, priming community assembly of microbes through priority effects and shaping host health and disease. Microbe acquisition during parental care is well studied in humans and agriculturally relevant species but remains poorly understood in other vertebrate groups, such as amphibians. Here, we investigate vertical transmission of skin microbiota in poison frogs (Dendrobatidae), where fathers transport tadpoles piggyback-style from terrestrial clutches to aquatic nurseries. We found that substantial bacterial colonization of embryos begins after hatching, suggesting that the vitelline envelope acts as a microbial barrier. A cross-foster experiment demonstrated that poison frogs performing tadpole transport serve as a source of skin microbes for tadpoles on their back. To study how transport impacts skin communities of tadpoles in an ecologically relevant setting, we sampled sympatric species that do or do not exhibit tadpole transport in their natural habitat. We did not find a higher degree of similarity between microbial communities of tadpoles and adults in species that transport their offspring compared to those that do not. Similarly, communities of tadpoles were no more similar to their caregiver than to unrelated adults, indicating that most caregiver-associated microbes do not remain in tadpole communities long-term. Nonetheless, some taxa persisted on tadpoles over development. This study is the first to demonstrate that offspring transport facilitates transmission of parental skin microbes in anurans.