Chondrina Reichenbach, 1828

Kokshoorn, Bas & Gittenberger, Edmund, 2010, Chondrinidae taxonomy revisited: New synonymies, new taxa, and a checklist of species and subspecies (Mollusca: Gastropoda: Pulmonata) 2539, Zootaxa 2539 (1), pp. 1-62 : 26-27

Chondrina Reichenbach, 1828

Type species (design. Reichenbach 1836: 152): Bulimus avenaceus Bruguière, 1792 .

Notes.—For this genus the results of a preliminary, molecular, phylogenetic analysis are available ( Kokshoorn 2008: 41–58). This analysis (see fig. 4) made clear that in any case, a revision of the classification presented by Gittenberger (1973) is necessary. In particular the nominal taxa united by that author as a single, polytypic species, i.e. Chondrina farinesii ( Des Moulins, 1835) , should not all be lumped. Obviously, there are many more taxa, characterized by shells with more or less obsolete, apertural teeth. In some cases, shell dimensions, shape and sculpture, could be used under the direction of the molecular data, but many questions remain unanswered because of a lack of sufficient information. Since it is unlikely that this situation will improve substantially in the near future, we have already adapted the classification of the Chondrina taxa to the new insights. Since the dataset presented in figure 4 is inconclusive at some points in the tree, we refrain from revising taxa that show ambiguous positions in the phylogenetic reconstruction.

New taxa are formally described and named only when they can be recognized on the basis of molecular and (to some extent) conchological characteristics. For the time being, to promote further research, some taxa are referred to with numbers only. These taxa can only be defined on very limited DNA data, so that their geographical distribution and the variation in shell morphology remain unknown. More sequence data are needed to acquire more reliably classified material. Shell morphology should be studied again in search of hitherto unnoticed common characteristics. Inevitably, an additional increase of DNA data will dictate further changes in the following overview. The phylogenetic relationships within Chondrina are more complicated than may be assumed at first sight.

The apertural teeth do not vary randomly in Chondrina . There is a “bauplan I” with more than two palatals and a spiralis, next to a “bauplan II” with two palatals at most and no spiralis. Toothless forms may be considered derived from the latter bauplan. These two groups are not clades however. Some individual specimens or even species do not belong to one of the alternatives. In C. aguilari there may be an infrapalatalis but never a spiralis, whereas in C. pseudavenacea there are three palatals, again without a spiralis. According to Gittenberger (1973: 232) there may be an infrapalatalis, a suprapalatalis and an obsolete spiralis in C. calpica . In this species bauplan II is the rule, but rarely specimens with apertural teeth according to bauplan I occur as well. We have to conclude that the apertural teeth became obsolete or were reduced completely several times independently, resulting in shells that misleadingly suggest a close relationship in various cases.Several authors have contributed to the currently accepted taxonomy of the group ( Nordsieck 1962, 1970; Gittenberger 1973; Gómez & Angulo 1982). Chondrina avenacea and C. arcadica clienta have been used as model organisms in ecological and evolutionary studies ( Armbruster et al. 2007; Baur, A. & Baur, B. 1991; Baur, B. & Baur, A. 1990, 1994, 1995; Baur, B. et al. 1993, 1995; Baur, A. et al. 1992, 1994; Fröberg et al. 1993; Hesbacher et al. 1995; Szarowska et al. 2003). However, a study devoted to the phylogeny of the Chondrina species was still not available. Gittenberger (1973) divided the genus in four subgroups. He regarded that classification rather artificial, probably reflecting only some morphological and geographical similarities rather than phylogenetic relationships. Since this subdivision does indeed not reflect the evolutionary history of the genus, it is no longer acceptable.

Since C. maginensis has to be considered the sister-group of all other Chondrina taxa combined, that species is dealt with first. The remaining Chondrina taxa are provisionally arranged in six species groups, guided by the results of the molecular analysis ( Kokshoorn et al. 2010)(see also fig. 4). Since the taxonomic diversity is much larger than previously expected, the molecular analysis should be considered far from complete. Consequently, the arrangement of species based on it, must be considered hypothetical at most. As a final group, some nominal taxa are listed that have been synonymized or overlooked before, but might represent separate Chondrina species or subspecies.The geographical distributions of the Chondrina taxa discussed in this paper are shown in fig. 5, 6 and 7.