Speciation in the genusCloacina(Nematoda: Strongylida): species flocks and intra-host speciation

Abstract

Sequences of the first and second internal transcribed spacers (ITS1 + ITS2) of nuclear ribosomal DNA were employed to determine whether the congeneric assemblages of species of the strongyloid nematode genus Cloacina, found in the forestomachs of individual species of kangaroos and wallabies (Marsupialia: Macropodidae), considered to represent species flocks, were monophyletic. Nematode assemblages examined in the black-striped wallaby, Macropus (Notamacropus) dorsalis, the wallaroos, Macropus (Osphranter) antilopinus/robustus, rock wallabies, Petrogale spp., the quokka, Setonix brachyurus, and the swamp wallaby, Wallabia bicolor, were not monophyletic and appeared to have arisen by host colonization. However, a number of instances of within-host speciation were detected, suggesting that a variety of methods of speciation have contributed to the evolution of the complex assemblages of species present in this genus.

Genetic variation in Austrostrongylus thylogale Johnston & Mawson, 1940 (Nematoda: Trichostrongylida) from the tammar wallaby, Notamacropus eugenii (Gray), and the quokka, Setonix brachyurus (Quoy & Gaimard) (Marsupialia: Macropodidae) in Australia

“…undergo speciation via host-switching due to overlapping host-ranges and feeding habits [25,26,31]. In the present example, apart from infecting a new host species, the parasite appears to have undergone a degree of genetic differentiation within the new host.…”

Phylogenetic relationships of three tribes of cloacinine nematodes (Strongylida: Chabertiidae) from macropodid marsupials

“…2) provides little evidence of co-speciation. These host–parasite associations are potentially best explained in evolutionary terms by a process of host colonization, as proposed in previous molecular studies of related tribes of the Cloacininae (Chilton et al ., 2011, 2016a, b, c, 2017), but this should be considered as a preliminary hypothesis pending the possibility of more formal analyses. In several instances, genetically identical (based on ITS-1 and ITS-2 sequences) individuals of a nematode species (e.g.…”

“…Although the present study has highlighted the radiation of some nematode genera within a particular host genus (e.g. Thylonema , Trigonostonema and Thallostonema in species of Thylogale , and Alocostoma and Zoniolaimus in species of Macropus ), relatively few instances of within-host speciation were identified, a phenomenon occurring in the related genus Cloacina (Chilton et al ., 2017). As indicated above, associations within Thylogale spp.…”

“…Recent molecular studies of the tribe Labiostrongylinea (Chilton et al ., 2011), of three genera within the tribe Pharyngostrongylinea (i.e. Cyclostrongylus , Pharyngostrongylus and Rugopharynx ) (Chilton et al ., 2016a, b, c), and within the genus Cloacina (tribe Cloacininea) (Chilton et al ., 2017), have demonstrated the utility of the internal transcribed spacers (ITS-1 and ITS-2) of the nuclear ribosomal DNA for determining the relationships between nematode species belonging to this subfamily.…”

Wildlife parasitology in Australia: past, present and future

“…However, detailed studies remain to be undertaken. By contrast, studies of the anoplocephaline cestodes and cloacinid nematodes of macropodids using both morphological and molecular approaches currently suggest that host switching has been the major mechanism by which these large parasite radiations have evolved (Baverstock et al 1985;Beveridge and Spratt 1996;Beveridge and Chilton 2001;Chilton et al 2011Chilton et al , 2017.…”