Phylogeography ofTrichurispopulations isolated from different Cricetidae rodents

Abstract

The phylogeography of Trichuris populations (Nematoda) collected from Cricetidae rodents (Muroidea) from different geographical regions was studied. Ribosomal DNA (Internal Transcribed Spacers 1 and 2, and mitochondrial DNA (cytochrome c- oxidase subunit 1 partial gene) have been used as molecular markers. The nuclear internal transcribed spacers (ITSs) 1 and 2 showed 2 clear-cut geographical and genetic lineages: one of the Nearctic region (Oregon), although the second was widespread throughout the Palaearctic region and appeared as a star-like structure in the minimum spanning network. The mitochondrial results revealed that T. arvicolae populations from the Palaearctic region were separated into 3 clear-cut geographical and genetic lineages: populations from Northern Europe, populations from Southern (Spain) and Eastern Europe (Croatia, Belarus, Kazahstan), and populations from Italy and France (Eastern Pyrénean Mountains). Phylogenetic analysis obtained on the basis of ITS1-5·8S-ITS2 rDNA sequences did not show a differential geographical structure; however, these markers suggest a new Trichuris species parasitizing Chionomys roberti and Cricetulus barabensis. The mitochondrial results revealed that Trichuris populations from arvicolinae rodents show signals of a post-glacial northward population expansion starting from the Pyrenees and Italy. Apparently, the Pyrenees and the Alps were not barriers to the dispersal of Trichuris populations.

How many species of whipworms do we share? Whipworms from man and other primates form two phylogenetic lineages

“…The majority of phylogenetic studies on whipworms have been based on analyses of ITS1-5.8S-ITS2 rDNA, which revealed the relationships of rodent-and ruminant-infecting species of Trichuris (e.g. Cutillas et al 2004, Callejón et al 2012. However, the occurrence of more variants of RNA genes, including ITS2 region (Nissen et al 2012), makes their use in solving the phylogeny of Trichuris much less informative, especially in organisms with unknown ploidy.…”

“…Blouin et al 1998, Peng et al 2007, Jex et al 2009), allowing high resolution in deep analyses of closely related lineages (Callejón et al 2012). However, when comparing rDNA and cox1 data alone, support of branches is higher in trees based on nuclear data.…”

Whipworms of south-east Asian rodents are distinct from Trichuris muris

“…A redescription of T. muris by Roman [3] in 1951 based on multiple specimens collected from both the wood mouse (A. sylvaticus) and the house mouse (Mus musculus domesticus) from France provided morphometric attributes that provide a basis to distinguish T. muris from potentially novel species from other rodent species or geographic regions. In the last decade, various studies have established molecular evidence that representative host species of Murinae (Apodemus, Mus and Rattus) sampled in several localities across Europe are associated with T. muris as a unique whipworm species [4,5,6]. This molecular evidence is of particular importance as morphometrical traits are not conclusive to distinguish Trichuris species from rodents [7] and other mammals (e.g.…”

“…The use of internal transcribed spacer (ITS) have been proven useful as a tool to resolve relationships of helminths such as Trichuris at the species level, including whipworms studies from Murinae (e.g. : [5,11] and more generally in Rodentia collected elsewhere [33]). The present study aimed to shed light on the taxonomy of whipworms from rodents in SEA and to test whether specimens can be confirmed as "T. muris" as widely assumed.…”

The population genetics of parasitic nematodes of wild animals

“…Naturally, parasites with a fast generation time will undergo more rapid genetic drift (and so faster population divergence) than parasites with a slow generation time. Indeed, the significantly faster generation time of H. polygyrus compared with Trichuris muris may contribute to the comparatively more strongly genetically structured populations of the former when both species are analysed from the same host individuals [ 15 , 53 , 54 ].…”