Legacy parasite collections reveal species-specific population genetic patterns among three species of zoonotic schistosomes

Studies estimating genetic diversity and population structure in multi-host parasites are often constrained by temporally and spatially limited sampling. This study addresses these limitations by analyzing globally distributed samples of three congeneric avian schistosomes (Trematoda: Schistosomatidae: Trichobilharzia), including collections spanning 20 years archived at The Museum of Southwestern Biology, Parasites Division. The three species exhibited significant differences in population genetic parameters across one nuclear and two mitochondrial loci. Trichobilharzia querquedulae (TQ) maintained a well-connected, globally diverse metapopulation, with an effective population size approximately three times larger than that of the other two species, T. physellae (TP) and Trichobilharzia sp. A (TA). TP and TA had lower overall genetic diversity and greater population structure. These differences are likely shaped by the ecologies of the duck definitive hosts that disperse these parasites. This study highlights the value of natural history collections, particularly since Trichobilharzia is a key agent of zoonotic cercarial dermatitis, a disease whose etiology and epidemiology remain poorly understood. Within a comparative congeneric framework, population genetic data can provide insights into host-parasite natural history and its influence on microevolutionary patterns, including contributions to zoonotic disease.