Reclaimed wetlands support rich trematode and host diversity: findings from a four-year survey

Snail hosts play a central role in structuring trematode communities. To test how snail hosts shape parasite diversity in central Alberta, we built upon a previous snail-trematode survey conducted at six lakes in central Alberta from 2013 to 2015 that uncovered 79 trematode species. However, analyses suggested that additional species remained to be uncovered. To build on this baseline, we conducted further snail-trematode collections from 2019 to 2022 at eight reclaimed wetland sites in various stages of reclamation, along with one established lake in Alberta. Across the nine sites, we collected 22,397 snails, of which 1981 were infected with digenetic trematodes. We also documented broader biodiversity at these sites using traditional survey techniques. Through DNA barcoding, we identified 74 trematode species infecting five snail species. Among these were 23 trematode species not previously reported in central Alberta and nine provisionally-named lineages with no matches to species in publicly available databases. In addition, we observed several previously unreported snail-trematode interactions. While trematode richness did not vary significantly with the wetland reclamation stage, host identity did influence richness: Physa gyrina hosted significantly more trematode species than Planorbella trivolvis. When combined with data from the earlier survey, sample completeness analyses indicate that we captured 100 % of the dominant species and 99 % of the typical species, but only 63 % of the overall species diversity in central Alberta. These findings underscore that trematode diversity in central Alberta remains incompletely characterized and highlight the continued value of long-term and host-inclusive sampling efforts.