title: Co-Speciation of the Ectoparasite Gyrodactylus teuchis (Monogenea, Platyhelminthes) and Its Salmonid Hosts.
abstract: Co-speciation is a fundamental concept of evolutionary biology and intuitively appealing, yet in practice hard to demonstrate as it is often blurred by other evolutionary processes. We investigate the phylogeographic history of the monogenean ectoparasites Gyrodactylus teuchis and G. truttae on European salmonids of the genus Salmo. Mitochondrial cytochrome oxidase subunit 1 and the nuclear ribosomal internal transcribed spacer 2 were sequenced for 189 Gyrodactylus individuals collected from 50 localities, distributed across most major European river systems, from the Iberian- to the Balkan Peninsula. Despite both anthropogenic and naturally caused admixture of the principal host lineages among major river basins, co-phylogenetic analyses revealed significant global congruence for host and parasite phylogenies, providing firm support for co-speciation of G. teuchis and its salmonid hosts brown trout (S. trutta) and Atlantic salmon (S. salar). The major split within G. teuchis, coinciding with the initial divergence of the hosts was dated to ~1.5 My BP, using a Bayesian framework based on an indirect calibration point obtained from the host phylogeny. The presence of G. teuchis in Europe thus predates some of the major Pleistocene glaciations. In contrast, G. truttae exhibited remarkably low intraspecific genetic diversity. Given the direct life cycle and potentially high transmission potential of gyrodactylids, this finding is interpreted as indication for a recent emergence (<60 ky BP) of G. truttae via a host-switch. Our study thus suggests that instances of two fundamentally different mechanisms of speciation (co-speciation vs. host-switching) may have occurred on the same hosts in Europe within a time span of less than 1.5 My in two gyrodactylid ectoparasite species.
authors.affiliation: Natural History Museum, University of Oslo, 0318, Oslo, Norway; School for Biological, Biomedical and Environmental Science, University of Hull, Hull, HU6 7RX, United Kingdom.
authors.forename: Christoph
authors.initials: C
authors.lastname: Hahn
authors.affiliation: Institute of Zoology, Karl-Franzens University of Graz, 8010, Graz, Austria.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Weiss
authors.affiliation: Department of Fish Parasitology, Hydrobiological Institute, 6000, Ohrid, R. Macedonia.
authors.forename: Stojmir
authors.initials: S
authors.lastname: Stojanovski
authors.affiliation: Natural History Museum, University of Oslo, 0318, Oslo, Norway.
authors.forename: Lutz
authors.initials: L
authors.lastname: Bachmann
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D004272:DNA, Mitochondrial / Q000737:chemistry; D004275:DNA, Ribosomal / Q000737:chemistry; D057915:Drug Substitution; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000235:genetics; D049810:Genetic Speciation; D014644:Genetic Variation; D006239:Haplotypes; D006790:Host-Parasite Interactions / Q000235:genetics; D059645:Mutation Rate; D058974:Phylogeography; D010986:Platyhelminths / Q000235:genetics* / Q000502:physiology; D012487:Salmonidae / Q000235:genetics / Q000469:parasitology*; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial; D004275:DNA, Ribosomal; D003576:Electron Transport Complex IV