Gulella inobstructa van Bruggen, 1965

van Bruggen, A. C., 2011, Northern Drakensberg range Gulella species (Gastropoda, Pulmonata, Streptaxidae): Gulella inobstructa van Bruggen, 1965, revisited, or types are not typical, African Invertebrates 52 (1), pp. 11-19 : 11-18

Gulella inobstructa van Bruggen, 1965

Figs 1–3, 7, Tables 1, 2 Gulella inobstructa: YDQ %UXJJHQ l965: ƻl, ¿JV l, 4 (7\SH ORF.: 6RXWK $IULFD,>7UDQVYDDO@ /LPSRSR SURYLQFH,

Magoebaskloof, Woodbush Forest); Richardson 1988: 91; Aiken 1995: 17. New material examined (all South Africa, Mpumalanga province, enumerated from south to north): Lydenburg area, 20 km SSE of Lydenburg, Uitsoek Forest (25°16.366'S: 30°33.138'E), 1200 m, indigenous forest, in leaf litter, leg. J.L. Horn leg., L 112, 3.ii.2006 (1 shell, NMSA W4561); Buffelskloof Nat. Res. (25°16.118'S: 30°31.139'E), c. 25 km S of Lydenburg, 1750 m, indigenous forest, leaf litter, J.L. Horn leg., L 180, 16.iii.2006 (2 shells, NMSA W4474, Fig. 1); Horseshoe Falls (25.13°S 30.7°E) near Sabie, c. 1130 m,

leaf litter, 23.vii.1978, H.E. van Hoepen leg./don. (5 shells, RMNH); Mt Sheba Nat. Res. (24°56.340'S: 30°42.634'E), c. 5 km Wof Pilgrim’s Rest, 1690 m, indigenous forest, leaf litter, J.L. Horn leg., MTS 14, 12.xii.2006 (29 shells, NMSA W5530 ; duplicates in RMNH); Mt Sheba Nat. Res. (24.931220°S: 30.709650°E), 1900 m, indigenous forest, on decaying log, A. Moussalli & D. Stuart-Fox leg., 25.ii.2004>ƻƟ7‒ƻƟ9@ (5 VKHOOV,106$:4 l9,)LJ. ƻ); 0W 6 KHED (ƻ4.9 lƻ°6 Ɵ.7Ɵ97°(), l9ƟƟ P, DIURPRQWDQH IRUHVW, OHDI OLWWHU,$. 0RXVVDOOL & '. 6 WXDUW ‒) R [OHJ., ƻ5.LL.ƻƟƟ4>ƻƟ7‒ƻƟ9@ (ƻ VKHOOV, 106$:ƻ4ƻ); 0DULHSVNRS) RUHVW (ƻ4° 4.Ɵl5‵6: Ɵ° 5l. 899‵(), l5ƻƟ P, LQGLJHQRXV DIURPRQWDQH IRUHVW, LQ OHDI OLWWHU RQ IRUHVW ÀRRU, -./. Horn leg., L 19, 1.iii.2005 (1 shell, NMSA W3502 , Fig. 3); Mariepskop Forest (24°33.307'S: 30°53.637'E), l46Ɵ P, LQGLJHQRXV DIURPRQWDQH IRUHVW, LQ OHDI OLWWHU RQ IRUHVW ÀRRU, -./. +RUQ OHJ., / l, ƻ. LY.ƻƟƟ5 (

shells, NMSA W3503). Gulella inobstructa has also been collected in only two of the forest study sites of

6ZD\H (ƻƟƟ4: 5 (WDEOH ƻ.l) & 6 (¿J. ƻ.l); $SSHQGL[ƻ RQ S. ƻ ƻ), L.H. 1HZ $JDWKD (Mmakgowa) Forest and Forest Glens. Both are situated in Limpopo Province but are part and parcel of the northern Drakensberg range as opposed to the more northern Soutpansberg complex. This material has not been studied for the present paper.

When G. inobstructa was described (van Bruggen 1965: 21) it was diagnosed as follows: “A smooth, medium-sized species of Gulella with only four teeth in a little obstructed aperture, viz., a parietal, labral and two columellar processes.” Only two DGXOW VKHOOV ZHUH DYDLODEOH DQG ZHUH FRQVLGHUHG VXI¿FLHQWO\ FKDUDFWHULVWLF WR ZDUUDQW recognition as a separate taxon. In addition there was a juvenile shell without any apertural dentition.

Recently a number of similar specimens has been collected in the northern Drakensberg escarpment (see above) exhibiting considerable variation in size, shape, sculpture and apertural dentition. Metric data of this material (inclusive of the type material) are shown in Table 1, which may be summarized as 4.4–9.4× 2.5–4.5 mm, l/d 1.75–2.48, with 6–8+ whorls, which implies that the smallest adult specimen is less than half the size of the largest shell. This is rare among species of Gulella , particularly those with a somewhat restricted distribution (see below).

8QIRUWXQDWHO\ WKHUH LV RQO\ RQH VDPSOH FRQWDLQLQJ D VXI¿FLHQW QXPEHU RI VKHOOV (ƻ7 DGXOW VKHOOV) WR UHÀHFW ORFDO YDULDWLRQ LQ VL]H DQG VKDSH (106$:55 Ɵ). $ IHZ RWKHU samples each encompass more than two adult shells (see Table 2). The data in this table more or less imply that local variation in size and shape is fairly limited. However, of the 24 specimens measured 11 are in the category 6.1–7.0 mm and 7 in 7.1–8.0 mm, or, conversely, 18 in the joint category 6.1–8.0 mm against only 3 in the category 4.1–6.0mm and also only 3 in 8.1–10.0 mm (see Fig. 4). Incidentally, the sum total of the material is too limited for statistical analysis.

Looking at Table 1 it is clear that as regards shell length there are hardly any really VLJQL¿FDQW JDSV LQ WKH VHULHV ± WKH RQO\ RQH WKDW LV VHHPLQJO\ DEHUUDQW EHLQJ VKHOO QR. l, 1.2 mm shorter than no. 2. The next gaps amount to no more than 0.3 mm. However, in the greater lengths (> 7.7 mm) the gaps become increasingly larger, i.e. 0.6 mm (between nos. 21 and 22) and 0.8 mm (between the paratype, no. 22, and the holotype, no. 23).

The major diameter or width of the shells varies from 2.5 to 4.5 mm. This is also unequally divided among the material, e.g. in the range 2.9–3.2 mm there are 18 shells, of which half (9) are 3.1 mm. Large gaps here are 2.6–2.9 = 0.3 mm, 3.2–4.2 mm = 1.0 mm, and 4.2–4.5 mm = 0.3 mm.

The ratio length/major diameter (l/d) varies from 1.75–2.45 implying that on the one hand there are fairly squat specimens as opposed to distinctly cylindrical shells (Table 1 and Fig. 5). However, this is another series with small gaps, varying from 0.02–0.08 with a value of 0.14 as the single exception (between nos. 21 and 2, i.e. 1.82 and 1.96). There is a cluster here too, i.e. there are 16 shells with l/d values of between (and inclusive of) 1.95 and 2.25.

The intergradation between ‘smooth’ and ‘costulate’ is slight; even pronounced growth striae may be considered costulae, so that no sharp delimitation is observed here. The VDPH DSSOLHV WR WKH RXWHU FROXPHOODU SURFHVV.,W DSSHDUV WKDW WKH VXSHU ¿ FLDO WKLFNHQLQJ of the columellar lip, originally considered an apertural process, is of rare occurrence and has so far only been found in the type material .

To summarize, there are small squat, medium elongate, large squat, and large elongate shells. Would this be an indication that more than one taxon is involved? This is a matter of personal interpretation – for the time being the present author prefers to consider this material only to represent G. inobstructa of which the populations live in a fragmented environment resulting in a noticeable amount of individual variation in shell shape and size.

The type material (two shells only) seems to represent close to the maximum length for the shell ( Fig. 5). As regards shape and apertural dentition, the extremely limited type material also represents a slightly aberrant population. This leads to the conclusion that G. inobstructa is a valid taxon but subject to considerable variation in shell size and shape. These data once again show that ‘ type material’ is at times far from ‘typical’ for the taxon involved.

The phenomenon of great variation in size, implying that the smallest adult specimen is approximately less than half the size of the largest shell, is rare among species of Gulella , particularly those with a somewhat restricted distribution (vide e.g., van Bruggen 1980; see also Herbert & Kilburn 2004). Some South African examples are G. adamsiana (Pfeiffer, 1859) with 6.5–11.0 mm (with a fairly large distribution in KwaZulu-Natal), G. farquhari (Melvill & Ponsonby, 1895) with 1.9–3.8 mm (includes data of van Bruggen, 1992, an in southern and East Africa very widely distributed species), G. infrendens (Von Martens, 1866) with 5.2–9.1 mm (a fairly widely distributed taxon in the Eastern Cape and KwaZulu-Natal), and G. planti (Pfeiffer, 1856) with 12.7–21.5 mm (a restricted endemic in KwaZulu-Natal).

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A normally smooth, medium-sized species of Gulella with only three processes in a little obstructed aperture, viz., a parietal (angular), a labral, and a columellar process (Verdcourt’s formula proposed in 1957/1962 1; 1; 0; 1); rimate or with closed umbilicus., Q UDUH FDVHV JURZWK OLQHV PD\ GHYHORS LQWR IDLUO\ LQVLJQL¿FDQW FRVWXODWLRQ. $OVR, WKH outer columellar wall of the lip of the aperture may exhibit a swelling that may be interpreted as an outer columellar process so that the apertural dentition then must be considered four-fold instead of three-fold (Verdcourt’s notation 1; 1; 0; 2). Anatomical and molecular data are as yet not available.

Connolly’s group 3 (ii) should include this form, but all taxa are different in being smaller or having 4-fold instead of 3-fold dentition. Connolly’s group 3 (ii) is partly covered by groups 2A and 2B in Herbert and Kilburn (2004: 155). Here, again, all taxa are different in being smaller or having 4-fold instead of 3-fold dentition. Also, none of the odd two dozen taxa of Gulella s.l. described since Connolly’s treatise matches this diagnosis.

The range of G. inobstructa seems to be restricted to a limited area in SE Limpopo / NE Mpumalanga between 23°30'– 25°30'S and 29°45'– 31°00'E where it lives in the leaf litter of afromontane forest situated between c. 1100 and c. 1900. All new records are from Mpumalanga ; the type locality (23°47'S: 30°04'E) and the two records in Swaye’s thesis are the only ones situated in Limpopo province .

GULELLA INOBSTRUCTA AND G. PERSPICUA

The shell of Gulella perspicua ( Melvill & Ponsonby, 1893) , partly sympatric with G. inobstructa , shows the same type of apertural dentition and comes within the range of measurements of the latter.

The following material was examined for this study ( South Africa, Mpumalanga): Barberton , 25°47'S: 31°03'E, c. 875 m, leg. G. Déglon, ex W. Falcon colln., don. Helen Boswell via A.C. van Bruggen (2 shells, RMNH); Waterval Boven, 25°38'S: 30°21'E, c. 1350 m, leg./don. H.E. van Hoepen, 9.VII.1978 (1 shell, RMNH). The Barberton material is particularly valuable as it was mentioned and probably examined by Connolly himself ( Connolly 1939: 33). Material was also personally studied in The Natural History 0 XVHXP (/ RQGRQ) LQ l967>³7UDQVYDDO´, 3RQVRQE\ FROOQ., l9Ɵ..ll.44 (OHFWRW\SH), l9 7.lƻ. Ɵ.llƻ (SDUDOHFWRW\SH); %DUEHUWRQ (+.-. 3X]H\), l945.8.ƻ.ƻ6l‒ƻ66@. ' U Herbert has kindly supplied a photograph of the paralectotype shell from Middelburg (Mpumalanga) 1 in London ( Fig. 6); this is in better condition than the now slightly damaged lectotype .

Available shell measurements (see Table 3) give a preliminary range of 4.7–5.2 × 2.4–2.7 mm, l/d 1.84–2.00, 7–7½ whorls, which is completely within the (lower parts of the) range of G. inobstructa ( Fig. 5). As regards apertural dentition there is some variation within populations, e.g. in the NMHUK series from Barberton. Four of the six shells exhibit a weak to very weak basal process, while the remaining two do not show any basal process at all. Otherwise this small sample is remarkably uniform in size, shape and whorls.

1 The type locality “Transvaal” was later restricted to Middelburg by Connolly (1912: 83).

Differences between the two taxa are fairly subtle, such as G. perspicua having more convex whorls and a more prominent inner columellar process in a less ovate aperture; both taxa have rimate shells or a closed umbilicus. However, there is one consistent difference between G. perspicua and G. inobstructa . The suture of the former is narrowly indented, resulting in an excavated, trench-like line, which is visible under fairly high PDJQL¿FDWLRQ. 7KLV KDV EHHQ GHVFULEHG LQ GHWDLO E\ +HUEHUW IRU KLV QHZ VSHFLHV Gulella deviae Herbert, 2006 . This author refers to the suture of G. perspicua ( Herbert 2006: 1072) as an “unusual, roundly rebated suture”.

Apart from Connolly (1939) only Aiken (1995: 6) has contributed detailed distribution data for G. perspicua : ³0LGGHOEHUJ>VLF!@, %DUEHUWRQ,:DWHUYDO %RYHQ, 2QGHUVDELH, Wyliespoort, Strydom Tunnels”.His locality “Ondersabie”, undoubtedly derived from the Johannesburg psychiatrist/shell collector Dr H.E. van Hoepen, is somewhat misleading. 2I¿FLDOO\ WKHUH LV RQO\ RQH 2QGHU 6DELH = /RZHU 6DELH LQ 6RXWK $IULFD, D ZHOO‒NQRZQ rest camp in the south-eastern districts of the Kruger National Park. This locality is in the Lowveld, characterized by a type of savannah vegetation utterly different from that of the afromontane forest on the Drakensberg escarpment. Van Hoepen did extensively collect in the escarpment forests in Mpumalanga.As a genuine Afrikaner, van Hoepen did most of his labelling in Afrikaans. This is the reason why the present author prefers to interpret “Ondersabie” as a lower lying area of or near the town of Sabie (25°06'S: 30°47'E, c. 1000 m), nested in a deep valley on the escarpment, rather than the Kruger National Park locality. Thus the range of G. perspicua stretches further south than that of G. inobstructa . The type locality of the former, Middelburg (25°46'S: 29°28'E, 1450 m), seems to be the southernmost limit of this taxon.

3HQGLQJ DQDWRPLFDO DQG PROHFXODU UHVHDUFK WKH DERYH LV VXI¿FLHQW HYLGHQFH WR FRQVLGHU G. inobstructa and G. perspicua to represent separate taxa.