Does the genetic structure of spring snail Bythinella (Caenogastropoda, Truncatelloidea) in Bulgaria reflect geological history?

Abstract

Bythinella is a minute dioecious caenogastropod that inhabits springs in central and southern Europe. In the Balkans, previous studies have addressed its morphological and genetic differentiation within Greece and Romania while the Bulgarian species have remained poorly known. The aim of the present paper has been to expand the knowledge on the subject in Bulgaria. Shell morphology and anatomy of the reproductive organs were examined, and a fragment of the mitochondrial cytochrome oxidase subunit I (COI) gene and the nuclear ribosomal Internal Transcribed Spacer 1 (ITS-1) were sequenced from 15 populations. Additional sequences from eight previously studied populations were included in our analyses. Phylogenetic analyses revealed five main mitochondrial DNA clades, which were partly confirmed by analyses of the ITS-1 sequences. The genetic differentiation between the clades was found to be in the range p=2.4-11.8%. Most of the populations belonged to clade I, representing Bythinella hansboetersi, and were distributed in SW Bulgaria. Clades II and III inhabit areas adjacent to clade I and were most closely related with the latter clade. Much more distinct were clade V, found at one locality in NW Bulgaria, and clade IV, found at one locality in SE Bulgaria, close to the sea. Four populations were found in caves, but only one of these represented a distinct clade. Considering the observed pattern of interpopulation differentiation of Bythinella in Bulgaria, we can suppose that isolation between clades I, II and III may have been caused by glaciations during the Pleistocene. The time of isolation between the above three clades and clade IV coincides with the Messinian Salinity Crisis, and the time of isolation between the clade V and the other four most probably reflects the isolation of the Rhodopes from western Balkan Mts by the seawater of the Dacic Basin.

Isolation as a phylogeny-shaping factor: historical geology and cave habitats in the Mediterranean Truncatelloidea Gray, 1840 (Caenogastropoda)

“…The low genetic diversity within the main Bythinella clade in Bulgaria, and its distinctness from the Romanian populations, indicates that the south-western and central Bulgarian populations are relatively young and colonised the area from the south, not earlier than during the late Pleistocene. This prediction is also supported by the observation that the genetic divergence of Bythinella is much greater in Romania than in Bulgaria (FAlniOwski et al 2009a, b, 2012b, OsikOwski et al 2015.…”

“…underground connections between cave systems, allowing an extensive gene flow between the local populations. A somewhat different diversity pattern was observed in cave-dwelling Bythinella from Bulgaria, where OsikOwski et al (2015) studied gastropods from 15 sites, including four caves. Among the 17 COI haplotypes discovered in their study, seven came from cave populations.…”

“…This review is entirely based on the materials published by szArOwskA et al (2014a, b, c, d, 2016a, b), OsikOwski et al (2015. To infer the phylogenetic relationships, various molecular markers were used: mitochondrial (cytochrome c oxidase subunit I (COI) and ribosomal 16S RNA) and nuclear (internal transcribed spacer (ITS-1), ribosomal 18S and 28S RNA, and histone 3 (H3)).…”

“…The COI analysis shows that the populations of Bythinella from Romania and Bulgaria form two distinct clades, with the estimated divergence time of ~8 Mya (OsikOwski et al 2015) (Figs 6, 8). The majority of the populations of Bythinella in Bulgaria inhabit western and central parts of the country (Fig.…”

Distribution of Monacha claustralis (Rossmässler, 1834) and M. cartusiana (O. F. Müller, 1774) (Eupulmonata: Hygromiidae) in central European and Balkan countries: new data

“…Analysis of selected gene nucleotide sequences is nowadays frequently used for species classification, delimitation and identification (faLniowski & wiLke 2001, HebeRt et al 2003a, b, 2013, szaRowska 2006, fioRentino et al 2008, 2016, saueR & HausdoRf 2009, szaRowska et al 2014, osikowski et al 2015, osikowski 2017, Neiber & HausdoRf 2015, Rysiewska et al 2016 and makes it possible to verify species ranges and their distribution. Nucleotide sequences of cytochrome oxidase subunit I gene (COI) were mainly used in the above cited papers.…”