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Recently, Wade et al. (2006, 2007) have published further molecular phylogenetic trees of the Helicoidea. The trees include 42 genera of the superfamily and are based on 823 (2006) or 915 resp. 1012 sites (2007) of nuclear rDNA. Helicoid groups from all over the world have been considered.
Analysis
For the family names used see the classification of part 1.
In the trees a part of the Pleurodontidae = Polydontinae together with Sagda (Sagdidae, until now excluded from Helicoidea) is basal to all other helicoid genera. Cepolis (Cepolidae) is basal to the remaining genera. Within those remaining genera there are six clades, Hygromiidae (+ Cochlicella (Cochlicellidae)), the other part of the Pleurodontidae = Pleurodontinae, Bradybaenidae + majority of Camaenidae, Satsuma (Camaenidae), Polygyridae and Helicidae, in different combinations. The seventh group, Monadenia (Monadeniidae), is basal to the clade Satsuma + Polygyridae + Helicidae or only to the Helicidae. If combined with the tree of Koene & Schulenburg (2005) the other examined North American Helicoidea (Helminthoglyptidae, Humboldtianidae) fall with Monadenia. The Camaenidae (except the Satsuma group) are scattered across the Bradybaenidae within the common clade.
The other families or family groups, Hygromiidae + Cochlicellidae (like in the other trees, see part 2), Polygyridae and Helicidae appear as monophyletic groups.
The results concerning the European groups do not essentially differ from those of Steinke et al., Koene & Schulenburg and Manganelli et al.
Discussion
The conclusions of this analysis are as follows:
(1) The Camaenidae sensu lato are not monophyletic (contrary to Cuezzo 2003).
(2) A part of the Camaenidae sensu lato (part of the American Pleurodontidae and the Asian / Australasian Camaenidae) and the Polygyridae are true Helicoidea.
(3) The American Pleurodontidae are not monophyletic either. The subfamilies Pleurodontinae (without epiphallic appendages) and Polydontinae (with epiphallic appendages) should be considered separate families; the latter are possibly related to the Sagdidae. This is supported by the fact that Sagdidae and Polydontinae have a genital feature in common, the presence of an accessory flagellum (named epiphallic caecum in Polydontinae). The Sagdidae, however, have a penial appendix like the Orthurethra, which is missing in the Polydontinae.
For further research, the examination of the Labyrinthus group (Pleurodontinae) and the Solaropsinae, both from South America, is urgently needed.
(4) The majority of Asian / Australasian Camaenidae are obviously Bradybaenidae without dart apparatus. The segregation of the Japanese Satsuma group from the other Asian / Australasian Camaenidae which is expressed in the trees cannot be supported by the genital morphology. It is true that, in contrast to most other Camaenidae, this group has a penial caecum, but this is also the case with Nipponochloritis, also from Japan, which is found within the Bradybaenidae-Camaenidae clade.
If the Bradybaenidae-Camaenidae clade is regarded as one family, unfortunately it has to bear the older name Camaenidae.
(5) The American Helicoidea with dart apparatus (Helminthoglyptidae sensu lato = Xanthonychidae sensu lato, Cuezzo 1998) are not monophyletic either. The Caribbean Cepolidae are not related to the North American families (Monadeniidae, Helminthoglyptidae, Humboldtianidae).
For further research, the examination of the Central American families (Lysinoidae, Metostracidae, Xanthonychidae) and the family Epiphragmophoridae from South America is urgently needed.
(6) Like in other trees (see part 2), the monophyly of the Ariantinae (+ Marmorana group) is supported, but not that of the Helicinae.
The discussion of the results by Wade et al. (2006: 604, 2007: 411, 413-414) suffers from the fact that the authors ignore the progress in the systematics of the Helicoidea since the seventies of the last century.
Besides, there are some short-comings in the discussion on the genital anatomy. Trochulus (Hygromiidae) has not only granules instead of darts, it has fully developed darts (see e. g. Koene & Schulenburg 2005). It is not clear whether the appendicula of Monacha (Hygromiidae) is homologous to the dart sac (as asserted by Wade et al. 2007: figs. 1-2) or to the accessory sac of the dart apparatus.
If the relation of the Sagdidae to the Helicoidea is confirmed, new insights on the phylogeny of the stimulatory organ (penial appendix, dart apparatus) are possible. Compared with the dart apparatus of the Helicoidea the penial appendix of the Sagdidae is regarded as plesiomorphic (Hausdorf 1998: fig. 2A). This would mean that the penial appendix is also the plesiomorphic stimulatory organ of the Helicoidea sensu lato. Contrary to the statement of Wade et al. (2007: fig. 1), the penial appendix of the Sagdidae has no dart.
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