Global Phylogeography of Salmonid Ectoparasites of the Genus Gyrodactylus, with an Emphasis on the Origin of the Circumpolar Gyrodactylus salmonis (Platyhelminthes: Monogenea)

The wageneri species group of Gyrodactylus contains the following molecularly confirmed salmonid parasites in Asia: taimeni Ergens, 1971, magnus Konovalov, 1967, brachymystacis 1978, and derjavini Mikhailov, 1975; Europe it following: derjavinoides Malmberg, Collins, Cunningham, Jalali, 2007, truttae Gläser, 1974, teuchis Lautraite, Blanc, Thiery, Daniel, Vigneulle, 1999, lavareti 1956, salvelini Kuusela, Ziętara, Lumme, 2008 (presented herein as a junior synonym salmonis Yin Sproston, 1948), salaris 1957, with lone North American exception being G. salmonis. mitochondrial DNA (cox1, 1545 bp) this shows star-like phylogenetic expansion that began 2.05 ± 0.4 million years ago (mya), estimated from mean distance cox1 gene (dMCL = 0.267) using tentative, potentially high-end, divergence rate 0.13/Myr. European on Thymallus thymallus Asian arcticus have been separated for 1.95 Myr 0.253). nuclear ITS rDNA region (1,245 was nearly uniform among populations Oncorhynchus mykiss, clarkii, nerka, Salvelinus fontinalis, Salmo salar (and non-native trutta) well alpinus (under salvelini) Lake Inari, Finland. is distal monophyletic subclade labeled by an apomorphic 56 bp insertion ITS1, shared (host: Coregonus lavaretus), pomeraniae Rutilus rutilus), bliccensis 1974 Alburnus alburnus). This subphylogeny suggests particular host switch cyprinids to salmonids may occurred less than 1.8 mya Old World [dMCL 0.234 vs (G. salmonis, lavareti)] possibly again coregonine hosts 1.2 0.156). Although hypothetical, transition coregonines charr (notably widely distributed adaptable alpinus) could proglacial refugium leading circumpolar distribution secondary other hosts. maximum genetic within all dMCL 0.032, at same level multihosted 0.032), suggesting circa 250,000 yr population these since temporal, coinciding bottleneck.