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Estimating effective population size for a cestode parasite infecting three-spined sticklebacks

Strobel, Hannah M., Hays, Sara J., Moody, Kristine N., Blum, Michael J., Heins, David C.
Parasitology 2019 v.146 no.7 pp. 883-896
Gasterosteus aculeatus, Schistocephalus, body length, effective population size, evolution, genetic variation, host-parasite relationships, hosts, lakes, microsatellite repeats, parasites, population genetics, population structure, Alaska
Remarkably few attempts have been made to estimate contemporary effective population size (Nₑ) for parasitic species, despite the valuable perspectives it can offer on the tempo and pace of parasite evolution as well as coevolutionary dynamics of host–parasite interactions. In this study, we utilized multi-locus microsatellite data to derive single-sample and temporal estimates of contemporary Nₑ for a cestode parasite (Schistocephalus solidus) as well as three-spined stickleback hosts (Gasterosteus aculeatus) in lakes across Alaska. Consistent with prior studies, both approaches recovered small and highly variable estimates of parasite and host Nₑ. We also found that estimates of host Nₑ and parasite Nₑ were sensitive to assumptions about population genetic structure and connectivity. And, while prior work on the stickleback–cestode system indicates that physiographic factors external to stickleback hosts largely govern genetic variation in S. solidus, our findings indicate that stickleback host attributes and factors internal to the host – namely body length, genetic diversity and infection – shape contemporary Nₑ of cestode parasites.