Terrestrial isopods (Isopoda: Oniscidea) in Alberta: species diversity, symbionts, and population structure
Creators: Stormer, Hannah G
Publisher: name: University of Alberta Library
Year: 2024

<p>Terrestrial isopods (Isopoda: Oniscidea), also known as sowbugs or woodlice, are one of the few groups of crustaceans that include members fully adapted to a terrestrial lifestyle. Sowbugs are readily transported by human activity, and many species have been introduced worldwide. Potential impacts of sowbugs on areas to which they are introduced include altering decomposition through feeding on organic matter, competition with native species, and cointroduction of symbionts (including parasites). However, the study of sowbugs has been largely overlooked in Canada, especially in the Prairie Provinces: only a single published study mentions the presence of sowbugs in this area. The goal of this study was to document a neglected component of Alberta’s biodiversity and to provide a foundation for understanding the potential impact of introduced sowbugs in this region. I first conducted a survey of sowbug species in Alberta, with additional collections from British Columbia, Saskatchewan, Ontario, and Newfoundland, and compiled an updated list of the sowbugs found in Canada. All nine species in Alberta are non-native and originate from Europe or Asia; one of these species (Nagurus cristatus (Dollfus) (Trachelipodidae)) has never been recorded from Canada. To assess the potential impact of introduced sowbugs through co-introduction of symbionts, I examined collected sowbugs for associated symbiotic species and compiled a list of all previously-recorded metazoan symbionts of sowbugs. I recovered nematodes, acanthocephalans, and mites from sowbugs in Alberta and British Columbia, including eight symbiont species never recorded previously from sowbugs. Sowbug-associated mites include the first record of Bakerdania elliptica (Krczal) (Neopygmephoridae) from North America. Sowbug and symbiont identifications are both supported by molecular data (COI barcodes, partial 18S) and include the first sequences for one sowbug and one symbiont species. Finally, I investigated the population structure of the sowbug Porcellio spinicornis Say in Alberta using genomic markers (ddRADseq) to explore the history and routes of entry of introduced sowbugs in the province and to assess the long-held hypothesis that greenhouses are sites of sowbug introduction. I found that sowbugs in Alberta likely originate from at least three introductions, most probably from other North American populations. Genetic evidence is consistent with anecdotal reports that sowbugs in Alberta are a recent introduction. Sowbug populations within Edmonton were remarkably homogenous, and likely originated from the same source. Evidence for greenhouses as primary introduction sites was inconclusive, but at least one greenhouse population originated via introduction from another site within Edmonton. Overall, it is unlikely that sowbugs currently pose a threat to Alberta’s ecology, economy, or human health. However, given the probable recency of sowbug introduction, sowbug populations in Alberta should be monitored to detect evidence of range expansion outside of urban sites of introduction. Additional surveys of sowbugs in Alberta and sowbug-associated symbionts globally may uncover many additional species records and symbiotic associations.</p>