Wollastonia jessicae monticola De Mattia, Neiber & Groh

Mattia, Willy De, Neiber, Marco T. & Groh, Klaus, 2018, Revision of the genus-group Hystricella R. T. Lowe, 1855 from Porto Santo (Madeira Archipelago), with descriptions of new recent and fossil taxa (Gastropoda, Helicoidea, Geomitridae), ZooKeys 732, pp. 1-125 : 50-52

Wollastonia jessicae monticola De Mattia, Neiber & Groh ssp. n. Figs 159-161, 162-166, 167

Type material.

NMWC Z.2016.013.00010, holotype, from loc. typ., leg. W. De Mattia & J. Macor, May 21 2015, NMWC Z.2016.013.00011/4 PT, SMF 348931/4 PT, NHMW 1121341/3 PT, CKG/3 PT, CMN/3 PT, CWDM/6 PT, from loc. typ., leg. W. De Mattia & J. Macor, May 21 2015; FW 11155/5 PT, CMN/5 PT, ZMH 131208/4 PT, 200 m SW of the Zimbreiro near the road turn serpentine, 33°04'16"N / 16°18'53"W, 100 m, leg. F. Walther, Mar. 31 2017; FW 11157/>10 PT, ridge between Zimbreiro and the quarry, 33°04'13"N / 16°18'49"W, 110 m, leg. F. Walther, Apr. 3 2017.

Locus typicus.

Porto Santo, Zimbreiro, 200 m SW of the village, near the road turn serpentine, 33°04'16"N / 16°18'53"W, 85 m.

Diagnosis.

Subspecies of Wollastonia jessicae with two keels on the body whorl, the lower distinct, the upper one very weakly developed to lacking; granulation relatively fine and scattered; internal walls of penis smooth, without pleats or prominent folds.

Etymology.

Named for the restriction of its habitat to the mountainous region (Lat. mons, montis = mountain(s) and -cola = inhabitor) of the island of Porto Santo.

Shell. Similar to the nominate subspecies, except for the ornamentation of the body whorl. In W. jessicae monticola ssp. n. the upper keel is missing and the lower keel is somewhat less strongly developed and less evident compared to W. jessicae jessicae sp. n. (see Figs 159-161).

Measurements.

D 4.6 ± 0.2 mm (range 4.2-4.9 mm); H 3.1 ± 0.1 mm (range 2.8-3.6 mm); FW 2.0 ± 0.1 mm (range 1.9-2.3 mm); PA 58,6 ± 6.1° (range 51.3-65.7°); DU 0.7 ± 0.04 mm (range 0.6-0.8 mm); NT 25 ± 14 (range 8-39); NW 5.5 ± 0.3 (range 4.9-5.9) (n = 30). Ratio D/H 1.5; ratio FW/H 0.6.

Body.

The overall body colouration (i.e. head, neck and sides) of W. jessicae monticola ssp. n. tends to be somewhat darker than in the nominate subspecies.

Genital anatomy.

The distal genitalia of W. jessicae monticola ssp. n. are similar to those of the nominate subspecies, except for the inner ornamentation of the genital atrium and penis that is, contrary to W. jessicae jessicae sp. n., completely smooth, without any pleats or folds. Minor differences can also be found in the length of the vaginal digitiform glands that are, on average, longer in W. jessicae monticola ssp. n. (see Figs 162-166).

Ecology.

W. jessicae monticola ssp. n. lives in a sloping hollow, in a relative humid spot along a temporary creek. The new taxon has been found exclusively under small volcanic stones in shady places under small shrubs. Its ecology differs somewhat from all the other Hystricella and Wollastonia species on Porto Santo, which are usually found under stones in open, dry grassland areas or on exposed rocky cliffs. W. jessicae monticola sp. n. has been found syntopically with Callina bulverii .

Distribution.

W. jessicae monticola ssp. n. is only known from the area in the vicinity of the locus typicus. Despite extensive field research in the area, the subspecies seems to occupy an area not larger than 100 m2 (see Fig. 167 for the distribution map).

Comparison and comments.

The new taxon differs from the nominate subspecies H. jessicae jessicae sp. n. by the almost complete lack of the upper keel on the body whorl and by the smooth internal genital atrium and penis. There is also a significant distributional gap between the two conspecific taxa and the habitats and altitudinal ranges also differ. In the phylogenetic analyses, W. jessicae monticola ssp. n. represents the sister group of W. jessicae jessicae inside the W. jessicae s. lat. clade, but divergence is rather low which speaks for a relatively recent separation and may be taken as justification for the subspecific status of the two taxa.

Status and conservation.

The subspecies has a very limited distribution area of less than 1 km2 (Fig. 167) close to a village and population size is probably rather low. Habitat quality is inferred to be declining and potential and ongoing threats to the species include, in our opinion, urbanization, tourism, goat grazing and quarrying. Therefore, the subspecies is considered here to be Critically Endangered (CR B1a, b(iii), 2a, b(iii)).