A phylogeny for the pomatiopsidae (Gastropoda: Rissooidea): a resource for taxonomic, parasitological and biodiversity studies

Abstract

BackgroundThe Pomatiopsidae are reported from northern India into southern China and Southeast Asia, with two sub-families, the Pomatiopsinae (which include freshwater, amphibious, terrestrial and marine species) and the freshwater Triculinae. Both include species acting as intermediate host for species of the blood-fluke Schistosoma which cause a public health problem in East Asia. Also, with around 120 species, triculine biodiversity exceeds that of any other endemic freshwater molluscan fauna. Nevertheless, the origins of the Pomatiopsidae, the factors driving such a diverse radiation and aspects of their co-evolution with Schistosoma are not fully understood. Many taxonomic questions remain; there are problems identifying medically relevant species. The predicted range is mostly unsurveyed and the true biodiversity of the family is underestimated. Consequently, the aim of the study was to collect DNA-sequence data for as many pomatiopsid taxa as possible, as a first step in providing a resource for identification of epidemiologically significant species (by non-malacologists), for use in resolving taxonomic confusion and for testing phylogeographical hypotheses.ResultsThe evolutionary radiation of the Triculinae was shown to have been rapid and mostly post late Miocene. Molecular dating indicated that the radiation of these snails was driven first by the uplift of the Himalaya and onset of a monsoon system, and then by late-Pliocene global warming. The status of Erhaia as Anmicolidae is supported. The genera Tricula and Neotricula are shown to be non-monophyletic and the tribe Jullieniini may be polyphyletic (based on convergent characters). Triculinae from northern Vietnam could be derived from Gammatricula of Fujian/Yunnan, China.ConclusionsThe molecular dates and phylogenetic estimates in this study are consistent with an Australasian origin for the Pomatiopsidae and an East to West radiation via Oligocene Borneo-Philippines island hopping to Japan and then China (Triculinae arising mid-Miocene in Southeast China), and less so with a triculine origin in Tibet. The lack of monophyly in the medically important genera and indications of taxonomic inaccuracies, call for further work to identify epidemiologically significant taxa (e.g., Halewisia may be potential hosts for Schistosoma mekongi) and highlight the need for surveys to determine the true biodiversity of the Triculinae.

Timing and causes of the distribution pattern of Oncomelania hupensis estimated by molecular and geologic data

“…The existing research results show that the subfamily Triculinae of Pomatiopsidae is mainly distributed in Southeast Asia, and the differentiation of the species is closely related to the temporal variation of the geologic events in the distribution area [28], which are closely related to the results of this paper. Although Oncomelania is now classified as part of Pomatiopsidae, the molecular clock (Fig 2) estimates show that Oncomelania species diverged at 12.41Ma,earlier than the rest of the included species in the family, suggesting the independence of Oncomelania .…”

The genera Erhaia and Tricula (Gastropoda, Rissooidea, Amnicolidae and Pomatiopsidae) in Bhutan and elsewhere in the eastern Himalaya

“…In addition to the 16S rRNA fragment (c. 535 bp; using standard primers by Palumbi et al 1991), the mitochondrial COI gene was also amplified (658 bp; standard primers by Folmer et al 1994). The final genetic dataset mainly comprised sequences from the study by Liu et al (2014) and additional sequences for Tricula that were obtained from Guan et al (2008). Uncorrected genetic p-distances for 16S rRNA and COI were calculated using MEGA 7.0.20 (Kumar et al 2016).…”

“…Distribution. The genus Erhaia is mainly known from China, where it has been recorded with various species from the province of Yunnan in the west to the provinces of Hunan, Hubei and Fujian in the east (Davis et al 1985;Davis and Kang 1995;Davis and Rao 1997;Wilke et al 2000Wilke et al , 2001Liu et al 2014). One species was described from northern India (Davis and Rao 1997), three from Nepal (Nesemann et al 2007) and one from Bhutan (Gittenberger et al 2017a).…”

“…The two populations differed genetically by 1.0% and 4.9% for 16S rRNA and COI, respectively. Because the monophyly of Tricula remains uncertain (see e.g., Liu et al 2014), we compared these sequences with additional data available from GenBank. For 16S rRNA, the lowest genetic distances, i.e., 3.1% and 3.3%, were identified between snails from Chhuburee and Khardungchhu, respectively, and Tricula sp.…”

“…the family Amnicolidae Tryon, 1863, with the genus Erhaia Davis & Kuo, 1985 and the family Pomatiopsidae Stimpson, 1865, with the genus Tricula Benson, 1843. Some species of these two genera are intermediate hosts for Platyhelminthes that are medically significant since they may transmit the human lung fluke Paragonimus Braun, 1899 or human Schistosoma Weinland, 1858 (Liu et al 2014).…”