Conflict of mitochondrial phylogeny and morphology-based classification in a pair of freshwater gastropods (Caenogastropoda, Truncatelloidea, Tateidae) from New Caledonia

Abstract

Morphological classification and mitochondrial phylogeny of a pair of morphologically defined species of New Caledonian freshwater gastropods, Hemistomia cockerelli and Hemistomia fabrorum, were incongruent. We asked whether these two nominal species can be unambiguously distinguished based on shell morphology or whether the taxonomic discrepancy inferred from these character types was reflected in the variation of shell morphology. Our investigations were based on phylogenetic analyses of a fragment of the mitochondrial cytochrome c oxidase subunit I, geometric morphometric analyses as well as micro computer tomography. The species presorted to morphospecies by eye overlapped in shell shape. However, statistically, all shells were correctly assigned, but not all of them significantly. Qualitatively, both nominal species can be unambiguously distinguished by the presence/absence of a prominent denticle within the shell. In the phylogenetic analyses, individuals from three populations clustered with the “wrong” morphospecies. In the absence of data from multiple loci, it was assumed for the single specimen from one of these populations that its misplacement was due to a recent hybridization event, based on its very shallow position in the tree. For the other two cases of misplacement neither introgression nor incomplete lineage sorting could be ruled out. Further investigations have to show whether the morphological overlap has a genetic basis or is due to phenotypic plasticity. In conclusion, despite their partly unresolved relationships Hemistomia cockerelli and Hemistomia fabrorum may be considered sister species, which are reliably diagnosable by the presence or absence of the denticle, but have not yet fully differentiated in all character complexes investigated.

Application of Shape Analyses to Recording Structures of Marine Organisms for Stock Discrimination and Taxonomic Purposes

“…The study suggests that genetic characters are determined by the distribution history of the species, whilst the shell structure to a greater extent reflects the influence of local environmental factors. This probably explains the fact that in some studies, GM-based analysis and molecular analysis showed similar results (Cruz et al, 2012;Vaux et al, 2018), whilst in others they did not (Becker et al, 2016).…”

“…The main fields of application include the study of intraspecific variability (Vuolo et al, 2011;Madeira et al, 2012;Moneva et al, 2012b;Sepúlveda and Ibáñez, 2012;Vogler et al, 2012;Avaca et al, 2013;Camama et al, 2014;Jamasali et al, 2014;Sobrepeña and Demayo, 2014;Cazenave and Zanatta, 2016;Zhao et al, 2019;Tuset et al, 2020) and assessment of environmental impacts (Sepúlveda and Ibáñez, 2012;Vogler et al, 2012;Vasallo et al, 2013;Camama et al, 2014;Cazenave and Zanatta, 2016;Amini-Yekta et al, 2019;Zhao et al, 2019), including the effect of pollution (Márquez et al, 2011;Abdelhady, 2016;Primost et al, 2016). Nevertheless, GM was also used for identification of mollusks (Doyle et al, 2018), evaluation of interspecific variability (Dommergues et al, 2003;Carvajal-Rodríguez et al, 2005;Vuolo et al, 2011;Cruz et al, 2012;Vogler et al, 2012;Silos et al, 2014;Becker et al, 2016;Miller, 2016), ontogenetic and individual variation (Moneva et al, 2012a;Avaca et al, 2013;Sobrepeña and Demayo, 2014), and to characterize phylogenetic relationships (Smith and Hendricks, 2013;Dillon and Jacquemin, 2015;…”

“…Doyle et al (2018) compared the classification power of landmarkbased analysis and EFA and showed that the latter provides higher accuracy in the classification of cases. Nevertheless, the landmark-based analysis, which is used routinely in studies of the intraspecific variability of gastropod shells also provides a reasonable level of classification accuracy (Becker et al, 2016;Cazenave and Zanatta, 2016). Despite the fact that landmarkbased GM has been used in studies of gastropod mollusks for about 30 years (Johnston et al, 1991), this method truly flourished only during the last decade, when the development of imaging technologies improved the quality and resolution of digital images, allowing for a sufficient number of landmarks to be distinguished in the images.…”

Diversity of Potamolithus (Littorinimorpha, Truncatelloidea) in a high-diversity spot for troglobites in southeastern Brazil: role of habitat fragmentation in the origin of subterranean fauna, and conservation status

“…However, molecular studies indicated a position within the Tateidae (Wilke et al 2013), a much smaller family with 32 genera, distributed in Australasia/Oceania and the Neotropics (Wilke et al 2013, Haase andZielske 2015). Considering the possibility of conflict with molecular phylogenies and morphologybased classifications, as recently shown for some Tateidae (Becker et al 2016), we choose not to take any position regarding the familial status of Potamolithus until all the evidence corroborates one of these, or different, taxonomic hypotheses. Comparisons are made with other subterranean truncatelloids.…”