System changes in Phaedusinae (Clausiliidae)
Hartmut Nordsieck (II.2021)
Two recent papers (Motochin et al. 2017, Mamos et al. 2020), presenting DNA studies of the Phaedusinae, require a revision of the shell-based system of that subfamily used until now (Nordsieck 2007). In parts I and II these papers are reported and commented. In part III the shell-based system is summarized. In part IV the evaluation of morphology is discussed. In part V the conclusions are given.
[of shell-based system = sbs]
I. Motochin et al.
Results of gene trees:
Synprosphymini (Synprosphyma) basal.
Separation of tribe of its own (Nordsieck 2007) confirmed.
[In brackets representative species. Groups with G type CA = G].
Groups from Japan and Taiwan (new system used, clades denoted with capitals):
A = Stereophaedusa:
Breviphaedusa (gouldi = Stereophaedusa sbs);
Mesophaedusa (hickonis, japonica = Stereophaedusa sbs, koshikijimana = Pliciphaedusa sbs);
Luchuphaedusa (callistochila, bernardii = Nesiophaedusa sbs);
Oophaedusa (ophidoon = Luchuphaedusa sbs);
unassigned neniopsis = Pseudophaedusa sbs, hemileuca = Pliciphaedusa sbs, okimodoki = Mesophaedusa sbs, caloptyx = Hemizaptyx sbs.
B = Megalophaedusa:
Pinguiphaedusa (pinguis, awajiensis = Placeophaedusa sbs);
Ventriphaedusa (platyderula = Tyrannophaedusa sbs);
Vitriphaedusa (subulina, hosayaka = Mundiphaedusa sbs);
Aulacophaedusa (gracilispira, aratorum = Mundiphaedusa sbs);
Megalophaedusa (martensi, ducalis = Mundiphaedusa sbs);
Dimphaedusa (decapitata = Mundiphaedusa sbs);
Tyrannophaedusa (mikado, bilabrata);
Tyrannophaedusoides (kawamotoi = Tyrannophaedusa sbs);
Neophaedusa (ishikawai = Mesozaptyx sbs, other sp. = Mundiphaedusa sbs);
Pauciphaedusa (toshiyukii = Mundiphaedusa sbs);
unassigned aenea = Pliciphaedusa sbs, rex = Mundiphaedusa sbs, ikenoi = Mesophaedusa sbs.
C = Tosaphaedusa:
(cincticollis, akiratadai = Mundiphaedusa sbs).
D = Zaptyx:
Taiwanphaedusa (similaris = Hemizaptyx sbs);
Tyrannozaptyx (+ polita = Hemizaptyx sbs);
Hemizaptyx (pinto, + probably stimpsoni = Hemizaptyx sbs);
Stereozaptyx (+ Oligozaptyx G);
Zaptyx G (+ Metazaptyx G, Diceratoptyx G);
Thaumatoptyx (+ kotoshoensis = Zaptyx sbs, + Hemizaptyx sp. from Taiwan, but without examination);
unassigned oxypomatica = Heterozaptyx, asperata = Hemizaptyx sbs, ptychocyma = Hemizaptyx sbs, pseudosheridani = Hemizaptyx sbs.
E = Tauphaedusa.
F = Reinia (+ Pictophaedusa, Parareinia, sieboldtii = Pseudophaedusa sbs).
G = Changphaedusa (horikawai = Pseudophaedusa sbs).
Basal Solitariphaedusa (miyoshii = Mundiphaedusa sbs).
Groups from foreign regions (shell-based system used):
Basal to groups from Japan and Taiwan Selenophaedusa bavayi + Hemizaptyx minuta;
Clade of remaining groups:
basal Atractophaedusa antibouddah;
Serriphaedusa violacea = serrata;
Formosana swinhoei + F. splendens;
Papilliphaedusa porphyrea + Margaritiphaedusa ziyuanensis;
Euphaedusa aculus + Dentiphaedusa spinula;
Pseudonenia aenigmatica = salacana (= Oospira sbs) + Acrophaedusa sp. (= Oospira sbs), basal Margaritiphaedusa amoena = rusticana;
Formosanella bensoni, F. recedens + Oospira ootayoshinarii;
Phaedusa dichroa, P. sorella, P. filicostata, P. kelantanensis + Papilliphaedusa kunmingensis.
Morphological characters of following structures considered:
1 superior lamella;
2 inferior lamella;
3 clausilium plate;
4 lunellar (mistake: many Phaedusini species have a dorsolateral lunellar!);
6 + 7 upper palatal plica;
8 middle palatal plica;
9 lower palatal plica;
10 sutural plica(e);
11 shell apex;
12 diverticulum of bursa copulatrix.
For stereoma (= Stereophaedusa sbs) and cymatodes (= Mesophaedusa sbs) incongruity between nDNA and mtDNA trees stated: introgression concluded.
Morphology discordant with phylogeny.
Phylogeny concordant with biogeography.
Gene trees thought to represent one to one phylogenies of taxa. Clades of gene trees regarded as genera. Species not belonging to certain clades remain unassigned.
Imbalance of ranks: In the new system for Japanese and Taiwanese groups former genera downgraded to subgenera, in the system for foreign groups subgenera elevated to genera.
Characters of shell morphology, which are of decisive importance for species definitions, obviously without any importance for genus definitions.
Several characters of shell morphology not considered:
2 basal keel;
3 relationship of spiral lamella and superior lamella;
4 subcolumellar lamella;
5 lamellulae of G type CA;
6 relationship of inner endings of spiral lamella and inferior lamella;
7 inner part of subcolumellar lamella.
Characters of genital morphology (except of presence or absence of diverticulum) not considered.
So-called diagnoses are simply enumerations of morphological characteristics of the included species or species groups.
Similar genital organs of Phaedusini make possible interspecies hybridization. Possibility of interspecies hybridization proved by case stereoma–cymatodes. Phaedusini comparable to Albinaria group of Alopiinae (shell morphology diverse, genital organs similar), in which interspecies hybridization is a frequent phenomenon (see article on hybridization).
Possible past interspecies hybridization in Phaedusini a long time ago not taken into consideration.
Several remarkable cases of incongruity of shell morphology and gene sequences would be explicable by interspecies hybridization:
Hemizaptychoids scattered over many clades;
stereophaedusoids scattered over several clades,
luchuphaedusoids distributed among two clades;
striking similarity of Oligozaptyx with luchuphaedusoids;
inclusion of sieboldtii (Pseudophaedusa sbs) in the Reinia clade.
II. Mamos et al.
Synprosphymini (Synprosphyma) sister group of Garnieriinae (not well-supported).
See part I.
Phaedusini (for groups from Japan and Taiwan new system used, for other groups shell-based system, clades denoted with PH):
1: Phaedusa sp. Timor, P. dichroa; Oospira vanbuensis (Oospira), Phaedusa paviei; Euphaedusa aculus, Phaedusa lypra; Euphaedusa porphyrea (Papilliphaedusa).
2: Acanthophaedusa ookuboi.
3: Hemiphaedusa polydona (Notoptychia), H. billeti (Selenophaedusa).
4: Leptacme (= Leptocochlea) sykesi; Liparophaedusa auregani, Oospira grangeri (Siphonophaedusa); Dautzenbergiella duella, Oospira miranda (Oospira).
5: Phaedusa stenothyra (Phaedusa).
6: Oospira antibouddah (Atractophaedusa).
7: Oospira swinhoei, O. formosensis (Formosana).
8: (subclades denoted with J):
1: Tauphaedusa tau, T. sheridani;
Messageriella gargominyi, Zaptyx hachijoensis (Metazaptyx), Z. kikaiensis, Z. buschii (Zaptychopsis);
2: Reinia ashizuriensis, R. variegata, R. eastlakeana;
3: Changphaedusa horikawai (= Pseudophaedusa sbs);
4: Stereophaedusa japonica, hickonis (= Mesophaedusa sbs), jacobiana, nesiothauma (= Nesiophaedusa sbs); Megalophaedusa martensi, M. hosayaka (= Mundiphaedusa sbs), M. attrita (= Pinguiphaedusa sbs), M. pinguis (= Pinguiphaedusa sbs), M. mikado (= Tyrannophaedusa sbs), M. iotaptyx (= Tyrannophaedusa sbs).
No morphology considered.
Genus system used: For groups from Japan and Taiwan system resulting from gene trees (former genera downgraded to subgenera, following Motochin et al.), for other groups system based on shell morphology (former genera used, not subgenera, in contrast to Motochin et al.).
III. System based on shell morphology
System of Phaedusini (Nordsieck 2007) based exclusively on shell characters as follows:
[Evolution from … to …: genera]
1. Shell type:
from normal = Oospira type (inferior lamella steeply ascending, clausilium plate narrow) to Phaedusa type (inferior lamella spirally ascending , clausilium plate broad), in connection with ovipary to (ovo)vivipary:
megagenera Oospira and Phaedusa / Euphaedusa.
2. Lunellar type:
from plicae = Oospira type (free palatal plicae) to lunella = Hemiphaedusa type (instead of plicae lunella):
megagenera Oospira and Hemiphaedusa.
In all regions from Oospira type
to different types with modified plicae in direction to formation of lunella:
several genera with modified Oospira type.
In Japanese regions from Hemiphaedusa type
to Tyrannophaedusa type (inferior lamella straightly ascending, clausilium plate angular to notched), and
to Luchuphaedusa type (inferior lamella spirally ascending, clausilium plate chanelled to notched):
genera Tyrannophaedusa and Luchuphaedusa.
In Japanese and Taiwanese regions shell becoming smaller to dwarf insular = zaptychoid forms:
several zaptychoid genera.
3. Clausiliar type:
from normal = N type to special G type of most zaptychoids (parallel lamellae and sutural plicae distinct, clausilium plate enlarged into sutural angle):
zaptychoid genera with G type.
IV. Evaluation of morphology
Published shell morphology is often incomplete, its knowledge is insufficiently used.
The genus taxa have been diagnosed among others by the characters of the inner lamellae endings. These characters have not been considered for the genus taxa out of Japan and Taiwan described in the last decade (except of two); thus, the morphological analysis of these taxa is incomplete. This is of importance, if one tries to classify species with these genus taxa. A good example is Oospira ootayoshinarii. This species has been classified with nominate Oospira, but clusters in DNA analysis with Formosanella (see part I). The examination of the inner lamellae endings could give information, where it belongs. Thus, the systematic position of many species described in the last years is uncertain.
It should be considered that the genus taxa out of Japan and Taiwan can include several groups differing in shell characters, which might be not closely related. Atractophaedusa consists of two groups, the type group with decollate shell and another group with entire shell. Formosana includes at least three groups: type group, group of artifina, and group of moschina (small dextral species). Serriphaedusa includes two groups, type group and group of draesekei; two further groups (Gibbophaedusa, Altiplica) have recently been added. Within Bathyptychia three subgenera have been described. Selenophaedusa consists of five groups: type group, groups of diplochilus, billeti, bavayi, and spinifera. Margaritiphaedusa includes two groups: type group and group of ziyuanensis, Euphaedusa also two groups: type group and group of cylindrella. One may not be surprised if these genus taxa do not come out in DNA analysis as monophyletic.
Most publications on genital morphology do not offer exact subdivisions of the male end ducts and measurements. So it must be stated that genital morphology of most species is insufficiently known.
From DNA studies (I, II) it is concluded:
Character changes used for the shell-based system (III) frequently evolved in parallel.
Thus groups with lunella type (included in megagenus Hemiphaedusa) and groups with Phaedusa type = (ovo)viviparous groups (included in megagenera Phaedusa and Euphaedusa) comprise non-related evolutionary units.
Not only groups with modified plicae types are different evolutionary units, but also several groups with normal plicae type included in megagenus Oospira.
Zaptychoids did not evolve separately from similar groups with normal shell size (as assumed in Nordsieck 1998), but evolved within one (Zaptyx) clade.
But – morphological characters should be evaluated more thoroughly (IV). This has to be considered in future DNA studies.
Because shell characters are often homoplasies and genital characters are similar, higher taxonomic units within Phaedusini can only be characterized by gene sequences. Species or species groups with unknown sequences (at time nearly two thirds of the species, among them the vast majority of species out of Japan and Taiwan) must be provisionally assigned according to morphology and distribution (see Nordsieck 2021).
Motochin, R., Wang, M. & Ueshima, R . (2017): Molecular phylogeny, frequent parallel evolution and new system of Japanese clausiliid land snails (Gastropoda: Stylommatophora). – Zoological Journal of the Linnean Society, 181 (4): 795-845.
Mamos, T., Uit de Weerd, D., von Oheimb, P. V. & Sulikowska-Drozd, A. (2020): Evolution of reproductive strategies in the species-rich land snail subfamily Phaedusinae (Stylommatophora: Clausiliidae). – Molecular Phylogenetics and Evolution. https://doi.org/10.1016/j.ympev.2020.107060.
Nordsieck, H. (1998): Critical revision of the system of the Japanese Phaedusinae, proposed by Minato (1994) (Gastropoda: Stylommatophora: Clausiliidae). – Archiv für Molluskenkunde, 127 (1/2): 21-32.
Nordsieck, H. (2007): Worldwide Door Snails (Clausiliidae), recent and fossil. – 214 pp., 20 pls. Hackenheim (ConchBooks).
Nordsieck, H. (2021): Taxonomic important shell characters of Asiatic Phaedusinae (Gastropoda, Stylommatophora, Clausiliidae). – Acta Conchyliorum, 20: 56 pp., 19 pls.