Riding into the future on a fly: toward a better understanding of phoresy and avian lice evolution (Phthiraptera) by screening bird carcasses for phoretic lice on hippoboscid flies (Diptera)

Many phoretic relationships between insects are understudied because of taxonomic impediments. We here illustrate for avian lice riding on hippoboscid flies how new natural history data on phoretic relationships can be acquired quickly with NGS barcoding. Most avian lice are host-specific, but some can arrive on new hosts by riding hippoboscid flies that feed on bird blood. Our summary of the literature yielded 254 published records which we here show to belong to two large and 13 small interaction networks for birds, flies, and lice. In order to generate new records, we then developed a new protocol based on screening bird carcasses sourced by citizen scientists. The inspection of 131 carcasses from Singapore lead to the first record of a Guimaraesiella louse species riding on Ornithoica momiyamai flies collected from a pitta carcass. Phoresy may explain why this louse species is now known from three phylogenetically disparate hosts (Pitta moluccensis, Ficedula zanthopygia; Pardaliparus elegans). A second new case of phoresy enhances a large interaction network dominated by Ornithophila metallica, a cosmopolitan and polyphagous hippoboscid fly species. Overall, we argue that many other two- and three-way phoretic relationships between arthropods (e.g., mites, pseudoscorpiones, beetles, flies) can be resolved using cost-effective large-scale NGS barcoding, which can be used to pre-sort specimens for taxonomic revision and thus partially overcome some taxonomic impediments.