A fine‐scale phylogenetic assessment of digenean trematodes in central Alberta reveals we have yet to uncover their total diversity

Abstract

Despite over 100 years of digenean trematode parasite species descriptions, from a wide diversity of vertebrate and invertebrate host species, our ability to recognize the diversity of trematode species within a single lake remains an incredible challenge. The most challenging aspect is the identification of species from larval stages derived from intermediate hosts, due to the disjointed data of adult worm morphological descriptions, from which species are named, and links to corresponding molecular identifiers in depauperate databases. Cryptic species also play a significant role in the challenge of linking trematode larvae to adults, species identifications, and estimating diversity. Herein, we utilize a large, longitudinal dataset of snail first‐intermediate host infection data from lakes in Alberta, Canada, to infer trematode larval diversity using molecular phylogenetics and snail host associations. From our assessments, we uncover a diversity of 79 larval trematode species among just five snail host species. Only 14 species were identified to a previously described species, while the other 65 species are either cryptic or otherwise unrepresented by mitochondrial genes in GenBank. This study currently represents the largest and most diverse singular molecular survey of trematode larval fauna composed of over one thousand mitochondrial sequences. Surprisingly, rarefaction analyses indicate we have yet to capture the complete diversity of trematodes from our sampling area.

Environmental and ecological factors driving trematode parasite community assembly in central Alberta lakes

“…The collection of trematode cercariae from their snail first intermediate hosts in central Alberta has been previously described ( Gordy et al, 2016 ), as were the methods used for species identifications through molecular and morphological assessments ( Gordy et al, 2017 ; Gordy and Hanington, 2019 ), thus we only summarize the key findings here. The final dataset from this survey resulted in 2452 trematode samples that ultimately represented 79 trematode species identified from infections within five freshwater snail species: Stagnicola elodes, Lymnaea stagnalis, Helisoma trivolvis, Physa gyrina, and an unidentified planorbid.…”

“…The final dataset from this survey resulted in 2452 trematode samples that ultimately represented 79 trematode species identified from infections within five freshwater snail species: Stagnicola elodes, Lymnaea stagnalis, Helisoma trivolvis, Physa gyrina, and an unidentified planorbid. The collections took place from June to September 2013–2015 on a biweekly basis across six lakes in central Alberta: Buffalo Lake, Gull Lake, Isle Lake, Lac La Nonne, Pigeon Lake, and Wabamun Lake (for specific site information, see Gordy et al, 2016 ; Gordy and Hanington, 2019 ).…”

“…To examine biotic and abiotic influences on trematode community variation within their intermediate snail hosts, we built upon a recent survey that aimed to identify larval trematodes within snails from six lakes in central Alberta ( Gordy et al, 2016 ; Gordy and Hanington, 2019 ). From a sample of nearly 18,000 snails over three summers (2013–2015), 79 trematode species were found based on molecular phylogenetic identifications from five snail host species ( Gordy and Hanington, 2019 ), representing a fine level of taxonomic resolution over a relatively small spatial scale that allowed for an opportunity to focus on regional dynamics here. Previous studies examining this many trematode species did so over much larger spatial scales ( Thieltges et al, 2011 ), or employed smaller spatial scales with fewer species ( Richgels et al, 2013 ), and none utilized molecular approaches to characterize species.…”

Leeches as the intermediate host for strigeid trematodes – genetic diversity and taxonomy of the genera Australapatemon Sudarikov, 1959 and Cotylurus Szidat, 1928

“…In recent years, Heneberg et al [13] has combined a morphological and molecular analysis of central European Strigeidae from avian de nitive hosts to investigate the taxonomic position of several Cotylurus species and surprisingly revealed a high level of molecular diversity within morphologically wellestablished species. Locke et al [31] and Gordy and Hanington [14] also revealed the occurrence of several new species within this genus in Canada. These results clearly indicate the need for further, detailed morphological, molecular and phylogenetic studies.…”

“…Since then, the taxonomic status and validity of these genera have been questioned and changed several times: some authors (e.g., [17,18]) reduced Australapatemon to the level of a subgenus within Apatemon, while Yamaguti [19] restored it to the full generic rank, as further con rmed by Niewiadomska [20]. As the morphological differences between Apatemon and Australapatemon in both metacercariae as well as adult specimens are limited or subtle, these taxa have often been incorrectly determined (for details see [6] and references therein), and thus a few attempts to use molecular markers in the identi cation, taxonomy and phylogeny of these genera have been made in recent years [21,22,6,12,14,23]. Importantly, a detailed molecular analysis of cercariae and adult specimens of Australapatemon sampled across North America clearly indicates the existence of several distinct lineages within this taxon and indisputably points out the hidden species diversity [12,14].…”