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

Michelle A Gordy,Patrick C Hanington

doi:10.1002/ece3.4939

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.

Highlights

Trends in the ecology of pathogens are reliant upon an accurate identification of both pathogen and host species
The resulting diversity estimates from this study exemplify both the power and utility of molecular phylogenetics for species identi‐ fication, but this study identifies gaps and caveats that trema‐ tode taxonomists may face in future studies
More Cotylurus species have been added to GenBank (Locke et al, 2018), and these additions helped define three previously unidentifiable lineages from phylogenies. Both ML and Bayesian inference (BI) trees agreed with strong statistical support for the di‐ vision of all aligned sequences into 16 groups, which was further supported by Automatic Barcode Gap Discovery (ABGD) (pmax = 0.0077–0.0129)

Summary

| INTRODUCTION

Trends in the ecology of pathogens are reliant upon an accurate identification of both pathogen and host species. With the onset of molecular barcoding, have we realized the problems of cryptic morphology and the need for multiple lines of evidence for species delineation, but that for trematodes, we can use larval stages to delin‐ eate species (Detwiler et al, 2010, 2012; Georgieva, Selbach et al, 2013; Gordy, Locke, Rawlings, Lapierre, & Hanington, 2017; Locke, Mclaughlin et al, 2010; Schwelm, Soldánová, Vyhlídalová, Sures, & Selbach, 2018; Soldánová et al, 2017) This is advanta‐ geous in that it is considerably easier to collect larvae from snail, first‐intermediate hosts. We provide a current record of trematode and host associations within Alberta and encourage the continued effort

| METHODS

| DISCUSSION

Findings

13 Lakes in Alberta