Phylogenetic Analysis of Pseudapatemon spp. (Digenea: Diplostomoidea) Reveals a Lineage Specific to Scolopacid Shorebirds.

Abstract

PURPOSE: Pseudapatemon Dubois, 1936 is a small genus of diplostomoidean digeneans parasitic as adults in the intestines of scolopacid birds in the Holarctic and Indomalaya. Until now, no DNA sequences of any member of the genus were available and its phylogenetic affinities remained unknown. Herein, we sequenced 2 Pseudapatemon spp. from American woodcock in the United States and conducted molecular phylogenetic analysis to examine their relationships with other diplostomoideans. METHODS: Two species of diplostomids belonging to Pseudapatemon were collected from American woodcock in Wisconsin (USA). Partial nuclear 28S ribosomal rDNA and mitochondrial CO1 genes were sequenced. Phylogenetic analysis based on 28S ribosomal data was used for phylogenetic inference. RESULTS: In the phylogenetic tree, both species of Pseudapatemon spp. formed a strongly supported cluster in a 100% supported clade with another diplostomoidean parasitic in scolopacid birds, Pulvinifer macrostomum (Jägerskiöld, 1900). Very low intergeneric difference in 28S sequences (2.5%) was detected between Pulvinifer and Pseudapatemon spp. The 2 Pseudapatemon spp. in our analysis differed by 1.2% in partial 28S sequences and 13.5-13.7% in CO1 sequences. CONCLUSION: Representatives of the 2 currently sequenced genera of diplostomoideans from scolopacids proved to form a monophyletic clade. This provides evidence of an evolutionary host switch to scolopacid birds with subsequent radiation. Sequencing of other diplostomoideans from the Scolopacidae is needed to learn more about their phylogenetic relationships and address the question of the potential synonymy of Pseudapatemon and Pulvinifer Yamaguti, 1933.