Zhang, Guoyi
(2023)
Phylogeny of Helicoidei (Gastropoda: Stylommatophora) with special emphasis on the Chinese Camaenidae.
MRes thesis, University of Nottingham.
Abstract
The Helicoidei Rafinesque, 1815 are a widely distributed and highly diverse infraorder of land snails and slugs. Here we constructed a phylogenetic tree based on sequences of the large subunit ribosomal RNA gene to investigate the relationships within the Helicoidei. Based on our phylogenetic tree, the Polygridae and the Camaenidae cluster together, the Hygromiidae is polyphyletic and the Solaropsidae are the sister group to a clade comprising other Sagdoidea. The results suggest that the Camaenidae and Polygyridae is composed of several lineages that the relationships between these are not resolved. Our findings also suggest that the Hygromiidae s. lat. families should be restored to their previous name, Hygromiidae, as in the taxonomy of Bouchet et al. (2005).
A new subfamily of Camaenidae, Satsuminae n. subfam., is introduced and previous subgenera of Satsuma are raised to genera level. A new Camaenid genus, Jiaoliaous Zhang n. gen., belonging to the Bradybaeninae branch is described. This genus can be distinguished from other camaenid genera by its shell, which is covered with hairs, and its simple genital system, which consists of a dart sac, penial sheath, penis, distinct mucous glands and vagina Jiaoliaous tchefouensis (Crosse & Debeaux, 1863) n. gen. & n. comb. is the type species of this genus. This genus is currently known only from the Jiaodong Peninsula (Shangdong Province) and the Liaodong Peninsula (southern Liaoning Province in northeast China).
There are approximately 79 Chinese species and subspecies in the bradybaenine genus Cathaica Möllendorff, 1844 and Cathaica is a widespread genus of land snails in Shandong, China. Pliocathaica Andreae, 1900 is considered a subgenus of Cathaica. Here we re-describe six species, C. pyrrhozona (Philippi, 1847), C. fasciola (Draparnaud, 1801), C. leei Yen, 1935, P. buvigneri (Deshayes, 1873), P. pulverticula (Martens, 1882), P. gansuica (Möllendorff, 1899), and describe two new species, C. fohuiensis Zhang n. sp. and C. multicostata Zhang n. sp.s distributed in this territory.
Geometric morphometric analyses demonstrate that C. pyrrhozona, C. fasciola, C. leei and C. fohuiensis Zhang, n. sp. are conchologically similar. On the basis of differences in their genitalia, we consider C. pyrrhozona and C. fasciola to be distinct species. This re-establishes C. pyrrhozona as the type species of Cathaica. The new species C. fohuiensis, with conical shell and expanded vaginal base can be distinguished from other known Cathaica species on morphological criteria and this is robustly supported in the phylogenetic tree. The other new species, C. multicostata Zhang, n. sp., possesses a strongly ribbed discoid shell and exhibits mucous glands that cluster tightly with the vagina before inserting into the dart sac; in the molecular phylogeny it is the sister taxon to all other Cathaica species in the study.
On the basis of morphological characters and our molecular tree, the subgenera described to date are not sufficiently well established. Pliocathaica, represented here by Pliocathaica buvigneri, P. pulveratricula and P. gansuica, is not monophyletic. P. buvigneri has a very similar genital system to Cathaica muticostata, but the proximal accessory sac is on the left side instead of the right side and the mucous glands insert into the dart chamber instead of the dart sac chamber. Pliocathaica pulveratricula is also different from P. buvigneri, with the opening of the mucous glands located at the atrium instead of any chamber.
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