Capitina calcicola, Herbert & Moussalli, 2010

Herbert, D. G. & Moussalli, A., 2010, Revision of the larger cannibal snails (Natalina s. l.) of southern Africa - Natalina s. s., Afrorhytida and Capitina (Mollusca: Gastropoda: Rhytididae), African Invertebrates 51 (1), pp. 1-1 : 116-124

Capitina calcicola sp. n.

Figs 6B , 8C , 10A , 73C, D , 74 , 76 , 78B , 79–81

Natalina schaerfiae [non Pfeiffer, 1861]: Connolly 1912: 96 (in part); 1939: 116 (in part), pl. 4, figs 9–11. Natalina (Capitina) schaerfiae: Watson 1934: 153 (in part); Schileyko 2000: fig. 972A.

Etymology: From Latin calx (lime) and cola (an inhabitant); referring to its occurrence in calcium-rich habitats.

Identification ( Fig. 80 ): Capitina calcicola is a distinctive taxon easily separated from C. schaerfiae by its paler, more elevated, thicker shell, frequently with a bolder spiral colour pattern. In addition, the sculpture is somewhat coarser, the protoconch smaller (diameter 4.0– 5.3 mm), the head-foot coloration more orange and the radula has fewer teeth per transverse row.

Description: Shell subglobose to lenticular, spire low; comprising 4.5–5.0 whorls when adult; last adult whorl descending prior to aperture; apical surface lustreless, base glossy. Protoconch diameter 4.0– 5.3 mm, sculptured by axial riblets, strongest below suture, and increasing in strength toward end of final whorl; one or more weak incised spiral lines may be present just above abapical suture/periphery, but these sometimes scarcely evident. Teleoconch with similar axial riblets, these interacting with irregular spiral elements to produce a pitted or wrinkled sculpture; this sculpture evanescing at periphery and base smoother and more glossy with only weak growth-lines and fine spiral lirae. Aperture variable in shape, generally obliquely ovate-reniform; outer lip weakly, but distinctly thickened, white; interior of aperture sometimes with a thickened subsutural spiral ridge set back some distance behind outer lip, a second similar ridge present on upper part of parietal lip, the two delimiting a distinct groove underlying the suture (this feature present only in adult specimens and then only in some individuals); umbilicus of moderate width, partially obscured by upper, reflected portion of columella lip. In sub-adult specimens ( Fig. 80J ) the basal and columella lips show some thickening, but the upper outer lip remains thin and descends only slightly, the thickening of the columella lip is also not completed and the umbilicus is therefore less obstructed.

Shell whitish, overlain by a pale straw-brown to light honey-brown periostracum; apical surface patterned with spiral lines of differing width, in various shades of brown, one or two lines just above periphery usually more distinct; lines weaker on base and usually absent in peri-umbilical area; periostracum not extending over aperture lip at maturity.

Dimensions: Holotype: diameter 28.0 mm, height 17.2 mm; largest specimen (NMSA W5670/T2265, Grootbos Nat. Res.), diameter 33.6 mm; H:D of adults 0.58–0.70 (N=22).

Living animal ( Fig. 78B ): Head-foot pale apricot to bright orange or brown, usually paler laterally and beneath shell; pedal margin and tail often slightly more intensely coloured; tentacles somewhat paler or more greyish; no pale longitudinal bands evident on neck; mantle edge darker orange-brown.

Radula ( Figs 73C, D ): See generic description; formula 1+~20 (N=3) in adult, juveniles with fewer teeth in lateromarginal series.

Holotype ( Figs 80A–C ): SOUTH AFRICA: W. Cape: Die Dam region (34.7487°S: 19.6708°E), coastal fynbos, A. Moussalli & D. Stuart-Fox, 14/ii/2005 ( NMSA W6265 /T2262).

Paratypes: SOUTH AFRICA: W. Cape: same data as holotype ( NMSA W3354 /T2276, 1 specimen; W3355/ T2264, 5 specimens) ; Gansbaai (34.5794°S: 19.3442°E), coastal dune scrub, dormant, buried in sand under vegetation, A. Moussalli & D. Stuart-Fox, 13/ii/2005 ( NMSA W3201 /T2269, 4 specimens; W3368/T2263, 1 specimen; W3369/T2268, 1 specimen) ; Gansbaai area, Grootbos Nat. Res. (34.53402°S: 19.43480°E), 330 m, limestone fynbos, under vegetation beside rocks, D. Herbert & L. Davis, 08/x/2007 ( ELM D15856 , 2 specimens; BMNH 20100127 , 1 specimen; NMSA W5670 /T2265, 29 specimens; RMNH.MOL.121374, 1 specimen) ; Pearly Beach area, Bantamsklip (34.674772°S: 19.590264°E), limestone hills, at base of or in restios, M. Picker, 29/ix/2007 ( NMSA W5998 /T2266, 3 specimens) ; Cape Agulhas (34.8293°S: 19.9854°E), coastal dune scrub, buried deep in sand under small bush, A. Moussalli & D. Stuart-Fox, 14/ii/2005 ( MVM F167491 , 1 specimen; NMSA W3360 /T2270, 1 specimen; W3365/T2267, 8 specimens) ; Cape Agulhas, V. Fitzsimons , x/1940, ex Transvaal Museum ( NMSA 3978 /T2271, 1 specimen) ; Bredasdorp, E.L. Layard ( BMNH 1937.12.30.1311–13, 3 specimens) .

Additional material examined (all NMSA unless otherwise indicated): W. Cape: Hermanus, Maanskynkop ( SAMC A8174 ) ; Gansbaai, M. Picker, 06/ix/2003 (W4854); Gansbaai area, Grootbos Nat. Res. (34.54205°S: 19.41529°E), 215 m, milkwood forest, dead in leaf-litter, D. Herbert & L. Davis, 07/x/2007 (W5664) ; ditto (34.54063°S: 19.41318°E), 217 m, milkwood forest, in sandy leaf-litter, A. Moussalli & D. Stuart-Fox, 13/ ii/2005 (W5421) ; ditto (34.54135°S: 19.43871°E), 325 m, Afrotemperate forest, in leaf-litter and under logs, D. Herbert & L. Davis, 08/x/2007 (W5919); Bredasdorp area, Soetendalsvlei , ex Transvaal Museum (B7315); l’Agulhas, in macchia veld, J.S. Taylor, 22/viii/1964 (4122) ; Cape Agulhas (34.8293°S: 19.9854°E), coastal dune scrub, buried deep in sand under small bush, A. Moussalli & D. Stuart-Fox, 14/ii/2005 (W3359); Bredasdorp District, Prof. de Villiers ( BMNH 1937.12.30.1314–16) .

Distribution ( Fig. 79 ): Endemic to the Agulhas Plain, recorded only from the coastal region between Hermanus and Cape Agulhas, W. Cape. Records from Bredasdorp (e.g., Connolly 1939: pl. 4, figs 9–11), although perfectly plausible, require confirmation since all are early records and may simply cite the town due to its being the nearest well-known settlement. Recorded at altitudes from sea level to 330 m.

Habitat: Occurs primarily in coastal fynbos habitats (Agulhas Limestone fynbos and western Overberg dune strandveld, sensu Musina & Rutherford 2006), and can be common in limestone areas. Dead shells have also been found in coastal milkwood ( Sideroxylon ) forest, but much less commonly so. In the dry season the animals bury themselves deeply in sandy soil/litter beneath shrubs, but can be found on the surface beneath plants during wetter periods.

Notes: Capitina calcicola differs clearly and consistently from C. schaerfiae . Its shell is paler and more elevated (H:D=0.58–0.70 compared with 0.48–0.53 in C. schaerfiae , see Fig. 81 ), and the spiral colour bands are generally darker and more pronounced (excepting occasional weakly patterned individuals). In addition, the protoconch is smaller (diameter 4.0– 5.3 mm, compared with 6.0–7.0 mm in C. schaerfiae ), the body coloration is paler and of a more orange hue, and the radula has fewer teeth (approx. 20 per half row compared to approx. 30 in C. schaerfiae ). C. calcicola is also generally thickershelled (perhaps due to the presence of environmental limestone) and the periostracal layer is paler and thinner, tending to flake off after death; it is however certainly present in living specimens (cf. Connolly 1939).

Since these differences are considerable and include features of the protoconch, teleoconch and radula, we believe they are sufficient to warrant recognition of the two taxa as separate species. Molecular data likewise separate the two taxa ( Moussalli et al. 2009), although at present, the level of genetic divergence between the two is difficult to assess given the limited number of specimens sequenced to date. This remains a topic needing to be investigated more thoroughly through the collection and sequencing of further samples of both species from additional localities, particularly for C. schaerfiae . Conservation: Although not as narrowly endemic as C. schaerfiae , C. calcicola sp. n. too is evidently a species of restricted range. The known extent of occurrence is approx. 2500 km 2. It is recorded from or likely to occur in several formally protected areas and private nature reserves (Cape Agulhas National Park, Walker Bay Provincial Nat. Res. and Grootbos Private Nat. Res.). The continued preservation of pristine limestone fynbos habitats in the western Agulhas Plain is crucial to the on-going survival of this taxon. In this regard, habitat transformation resulting from the invasion of exotic Acacia species represents a potential threat.

BIOGEOGRAPHIC SUMMARY

Rhytidid snails represent a characteristic element of the palaeogenic invertebrate fauna of southern Africa ( Stuckenberg 1962). The family is thought to be of Gondwanan origin and part of what Solem (1959) termed the ‘southern relict fauna’. However, the Rhytididae has a somewhat restricted distribution within fragmented Gondwana, with representatives occurring only in southern Africa, Australasia and islands in the south-western Pacific (supposed rhytidids occurring in E.Africa, the Seychelles and Madagascar belong to other families, see Introduction). Strangely, they are absent from that part of Gondwana with which Africa had its most recent contact, namely South America (although their relationship to the South American Systrophiidae , which are also often included in the Rhytidoidea , needs to be further explored).A similar Gondwanan distribution that excludes South America is evident in sphaerotheriid millipedes and suggests an origin in eastern Gondwana ( Wesener & VandenSpiegel 2009). However, sphaerotheriid millipedes are also known from India, Madagascar and south-east Asia, whereas rhytidid snails are not. The absence of rhytidids from the latter regions implies that their pre-fragmentation distribution in eastern Gondwana did not include those parts of the African plate abutting the Indo-Malagasy plate. This is consistent with the fact that, within Africa, rhytidids are [remain] restricted to the extreme south and south-east of the continent. The African distribution of peripatopsid Onychophora is similarly confined to this region, and they are also absent from India-Madagascar and south-east Asia, but unlike rhytidids and sphaerotheriids, the peripatopsids also occur in South America. Although the present-day global distribution of each of these low-vagility, Gondwanan invertebrate groups comprises a different assemblage of Gondwanan continental fragments, this does not detract from their hypothesised Gondwanan origins and probably strongly relates to the distribution of respective groups in pre-fragmentation Gondwana.

Within south-east Africa, the larger rhytidids are limited to those regions south and east of the Great Escarpment ( Fig. 82 ) and the same is true for the smaller species ( Nata s. l.), although new distribution data indicate that the latter penetrate further inland than indicated in the map provided by Bruggen (1978), further even than Natalina s.l. (unpubl. data). The north-eastern family boundary is defined by the low-lying Limpopo Valley, a geomorphic feature already in existence in the Cretaceous ( Partridge & Maud 1987) and an effective biogeographic barrier since the early Tertiary ( Stuckenberg 1962). Only at the coast has the family crossed this barrier, and then only marginally so. The range of the related chlamydephorid slugs and the African peripatopsid Onychophora is similarly restricted by the Great Escarpment ( Hamer et al. 1997; Herbert 1997), but unlike the peripatopsids and rhytidids, the distribution of the chlamydephorids extends to the eastern highlands of Zimbabwe. African sphaerotheriid millipedes, though also largely confined to south-eastern Africa, range still further north, reaching Malawi (Wesener & Van den Spiegel 2009). It is possible that the restriction of these groups to the south and east of southern Africa is linked to the distribution of forests, but while this may have been true historically, it is not currently the case for either rhytidids or chlamydephorids as representatives of both occur in non-forest habitats such as open thicket and savannah, and even fynbos in the case of rhytidids.

Molecular evidence suggests that cladogenesis within Natalina s. l. probably predates the Pliocene ( Moussalli et al. 2009) and may have been associated with major drying, contraction and fragmentation of mesic habitat in sub-Saharan Africa commencing in the mid-Miocene and extending into the Plio-Pleistocene, a phenomenon known to have had important evolutionary implications for many components of the regional biota ( Mucina & Rutherford 2006; Tolley et al. 2008, 2009). The first lineage divergence appears to have split the ancestral stock into western ( Capitina ) and eastern lineages ( Afrorhytida and Natalina ). The boundary between the two is coincident with that between western (winter rainfall) and eastern (year-round rainfall) components of the Cape Floristic Region (CFR), in the region of the Breede River ( Cowling & Richardson 1995) ( Fig. 83 ), although the range of one Afrorhytida subspecies ( A. kraussi oraria ) lies just within the western CFR. Based on the present-day distribution of Capitina , this western lineage appears not to have crossed the Hottentots-Hollands Mountains (a sub-boundary within the western CFR), unlike Nata s.l., the other southern African rhytidid radiation. Capitina remains an isolated lineage restricted to the Agulhas– Overberg region (the Bredasdorp Centre of plant endemism). Its distribution does not overlap with either Afrorhytida or Natalina . In contrast, the current distributions of Afrorhytida and Natalina overlap extensively ( Fig. 82 ) and each has undergone moderate radiation in the year-round and summer rainfall regions south and east of the Great Escarpment.

Afrorhytida occurs only in the southern and eastern Cape, and the dominant biogeographic pattern is one of an west-east species turnover ( Fig. 83 ). Afrorhytida kraussi occurs in the eastern CFR, reaching its easternmost limit just west of Port Elizabeth. East of this it is replaced by A. knysnaensis , the turnover zone being more or less coincident with the boundary between the Fynbos and Albany Thicket biomes ( Mucina & Rutherford 2006), in the region of the Uitenhage Basin. A. knysnaensis is the sister taxon of A. kraussi from which it may have diverged due to selection pressures associated with the increasingly open and drier habitats emerging during the Plio-Pleistocene aridification. Certainly, A. knysnaensis is now more tolerant of drier conditions than is A. kraussi , and its distribution extends a considerable distance further inland, essentially tracking the Albany Thicket biome, a recognised centre of endemism for plants (van Wyk & Smith 2001), molluscs ( Govender 2007) and millipedes (Hamer & Slotow 2002).

To the east, A. burseyae replaces A. knysnaensis at the boundary between the Albany Thicket and the southern parts of the Grassland and Savannah biomes. Their distributions coincide also with river catchments, A. knysnaensis occurring in the Sundays and Great Fish catchments and A. burseyae , largely in the Kei and Mbashe catchments. It appears therefore that for these two non-forest species, it is the catchment boundaries that may be the limiting biogeographical features in this instance. Although these two taxa are not sister species and the boundary between the Great Fish and Kei catchments therefore not a vicariant feature contributing to speciation, it may well now limit dispersal and maintain the allopatry of these lineages. The high altitude, open grassy habitats of the Winterberge and Amathole Mountains could be an effective barrier to dispersal in the inland region.Although river catchments often define species boundaries in freshwater groups, they are rarely cited as being significant for fully terrestrial taxa, but Price et al. (2007) have postulated similar catchment-delimited boundaries between lineages of the cicada Platypleura stridula (L., 1758) in the south-western Cape. Relative to the preceding Afrorhytida species, A. trimeni has a more restricted range, limited to the coastal region of the Albany Thicket. It is not, however, a thicket species, occurring instead in forest patches within the broader thicket biome and thus its distribution is limited to the higher rainfall coastal regions suitable for forest persistence.

Phylogenetic diversity within Afrorhytida is evidently considerable, as indicated by the relatively deep divergence of the major clades and long branch lengths subtending the terminal taxa in all lineages except A. trimeni ( Fig. 1 ). This suggests that the lineages are relatively old, and that gene flow within them has been historically interrupted (less so in A. trimeni ), in which case phylogeographical substructure should be evident (e.g., A. kraussi ). Alternatively, high within-clade diversity without obvious geographical substructure ( A. knysnaensis ) may result from the persistence of a single large or several well connected populations combined with the retention of ancestral polymorphisms. Additional fine-scaled molecular analysis with greater specimen representation is needed to resolve these competing hypothesis.

The distribution of Natalina overlaps extensively with that of Afrorhytida in Eastern Cape, but extends much further to the north-east, reaching the Limpopo River valley in southern Mozambique. The most basal divergence is that of the morphologically distinct N. (Tongalina) wesseliana , the only Natalina lineage occurring in the subtropical north-eastern coastal region ( Fig. 84 ). Its distribution closely matches that of the Maputaland centre of endemism (van Wyk & Smith 2001). However, whereas most species endemic to this centre are of Afrotropical origin (van Wyk & Smith 2001), N. wesseliana is clearly derived from southern stock. Since the forests of the Indian Ocean Belt are thought to have expanded in to this region only after the last Glacial Maximum ( Eeley et al. 1999; Lawes et al. 2007), it seems probable that N. wesseliana , a largely forest-dependent species, persisted as relict populations along the coastal scarp in northern Zululand during the last hypothermal, expanding northwards and coastwards as forest cover increased. Although represented by relatively few individuals in our molecular phylogeny, there is some geographic substructure within this clade which, combined with the comparatively long branch lengths, suggests some historical interruption in gene flow and fragmentation of the refugial population.

Subsequent cladogenesis within Natalina (i.e. within Natalina s. s.) resulted in the evolution of two distinct lineages, the small-shelled N. quekettiana complex and the large-shelled N. cafra – beyrichi clade. The distribution of the former is tied to the forest biome along the north-eastern section of the Great Escarpment, extending to lower altitude mist-belt and scarp forests ( Fig. 84 ), and mirrors a pattern evident in the forest-dependent dwarf chameleons ( Bradypodion spp. ) of KwaZulu-Natal and the northern Drakensberg ( Tolley et al. 2004, 2006). The basal divergence of the two montane lineages in this clade ( Fig. 1 ) might be taken to suggest that the complex as a whole originated at high altitudes, with subsequent dispersal into mist-belt and scarp forests. However, the idea that the geographical location of the basal taxon within a clade reflects the centre of origin of that clade is controversial. Sequential localised differentiation within a widespread ancestral population may achieve a similar result ( Heads 2009). In this case, dispersal from montane forests to mist-belt and scarp forest would run counter to the general pattern evident in eastern South Africa, i.e. post-Last Glacial Maximum (LGM) dispersal from scarp forest refugia into higher altitude forests ( Lawes et al. 2007). Although, under such a scenario one might expect the lineages in the lower altitude forests to be basal. In fact, given the considerable genetic divergence evident within this clade, it seems likely that the early divergence of both montane lineages considerably predates the LGM (estimated to date from the Pliocene based on the conservative 5 % mutation rate for mtDNA used here – see Moussalli et al. (2009) for further detail). Thus the branching pattern evident in this group probably reflects sequential vicariant cladogenic events resulting from repeated expansion and contraction of Afrotemperate forests during the Plio-Pleistocene, perhaps from lower altitude scarp forest refugia. Evidently the forests in the Cathedral Peak–Injasuthi area have persisted through these climatic fluctuations, retaining lineages from previous interglacial expansions. The fact that these forests also contain narrow-range, forest-dependent chameleons ( Tolley & Burger 2007), spiders ( Griswold 1985) and achatinid snails ( Bruggen 1965) provides further support for their long term persistence. Millipedes of the genus Doratogonus Attems, 1914 , show similar narrow-range endemism associated with high altitude forests in the KwaZulu-Natal Drakensberg (Hamer 2000), although it is not clear whether the species concerned constitute a monophyletic lineage.

With regard to the Natalina cafra – beyrichi complex, the low levels of phylogenetic diversity evident in this clade point to relatively recent radiation ( Moussalli et al. 2009 and Fig. 1 ). The primary divergence within this complex relates to a cladogenic event in the north-eastern E. Cape, separating well-supported, north-eastern (KwaZulu-Natal) and southern (E. Cape) lineages ( Fig. 1 ). N. beyrichi then diverged from the main E. Cape lineage in the Pondoland region ( Fig. 84 ), an area known to be rich in neoendemics of Cape origin (van Wyk & Smith 2001) and a focus of endemism in other molluscan genera ( Bursey & Herbert 2004; Govender 2007; Cole & Herbert 2009). Subsequently, the remaining E. Cape N. cafra stock has diverged in to three further lineages. One is an ecologically tolerant form that is broadly distributed in the more mesic southern parts of the Albany Thicket ( N. cafra cafra ), whereas the other two are generally (though not exclusively in the case of N. cafra eumacta ) associated with forest habitats in the Amathole Mountains ( N. cafra amathole ) and the East London–southern Transkei coastal belt ( N. cafra eumacta ). The forests in the Amathole region are known to contain additional narrowly endemic, forest-dependent taxa belonging to other low-vagility groups, e.g., forest floor spiders ( Microstigmata amatola Griswold, 1985 ) and frogs ( Anhydrophryne rattrayi Hewitt, 1919 ). These forests straddle the catchment boundary between the Kei River on the one hand and the Great Fish River and smaller coastal catchments (Keiskamma and Buffalo) on the other. Griswold (1985) considered the deep, relatively arid and thicket-filled valleys of these two large drainage systems to be important barriers, isolating the forests and forest-associated animals of the Amathole Mountains. Significantly , his work on the spider genus Microstigmata ( Griswold 1985) revealed a similar spatio-temporal pattern of cladogenic events, with the KZN species occupying basal positions relative to a younger radiation in E. Cape, which in turn has foci of distribution west of the Great Fish River, in the Amathole Mountains , and in Transkei.Given these concordant patterns, it is possible that the basally divergent N. cafra natalensis represents a separate, highly cryptic species.

From the above biogeographic summary, it is evident that the spatial distribution of all the species and subspecies under consideration is correlated and congruent with the broader patterns of floristic endemism in the southern Africa, south and east of the Great Escarpment. Evidently, the historical evolutionary process that have shaped floral diversity in the region have had a similar influence on speciation in these carnivorous snails. Further studies need to focus on the more deeply divergent lineages such as Afrorhytida burseyae , A. knysnaensis , A. kraussi and the Natalina quekettiana complex, in order to improve sister-group resolution and to search for finer-level phylogeographic structuring and cryptic species. In addition, the patterns evident in Afrorhytida , Capitina and Natalina need to be compared with the growing body of information on other taxa of limited vagility ( Griswold 1985; Hamer & Slotow 2000; Tolley et al. 2006; Daniels et al. 2009), so as to identify concordant spatial patterns across unrelated groups. It is these taxa with limited dispersal capacity that are likely to retain the strongest biogeographic signal reflecting historical evolutionary processes at a regional scale ( Hugall et al. 2002, 2003). At a broader scale, the analysis of molecular data needs to be expanded to include a wider spectrum of genera from the broader Australasian region in order to explore Gondwanan relationships and to test whether the southern African rhytidid radiation is indeed monophyletic.

Figures

Fig. 6. Mantle edge anatomy of Afrorhytida, Capitina and Natalina, showing variation in left body lobe structure (all NMSA): (A) Afrorhytida knysnaensis (W5211); (B) Capitina calcicola sp. n. (W3201); (C) Natalina (Natalina) cafra natalensis subsp. n. (V8415); (D) Natalina (Tongalina) wesseliana (V7668).Abbreviations: lbl – left body lobe of mantle, pn – pneumostome, rbl – right body lobe of mantle.

Fig. 8. Radulae of Natalina, Afrorhytida and Capitina (all NMSA):(A) N. beyrichi (Martens, 1890) (W0591), scale bar = 1.0 mm; (B) A. kraussi (Pfeiffer, 1846) (W3351), scale bar = 500 µm; (C) C. calcicola sp. n. (paratype, W3360/T2270), scale bar = 250 µm.

Fig. 10. Spermatophores of Capitina, Afrorhytida and Natalina (all NMSA):(A) C. calcicola sp. n. (paratype, W5670/T2265), length 8.2 mm; (B) A. burseyae sp. n. (paratype, W5231/T2260), length 10.5 mm; (C) A. kraussi kraussi (W5803), length 20 mm; (D) N. cafra natalensis subsp. n. (paratype, E7682/T2375), length 16.3 mm; (E) N. quekettiana lucaris subsp. n. (paratype, W3305/T2559), length 26.5 mm; (F) N. wesseliana (V7668), length 32 mm. The head of the spermatophore is uppermost in all cases and the lengths given are for the spermatophore as if straightened out.

Fig. 73. Capitina species, radula: (A, B) Capitina schaerfiae (Pfeiffer, 1861), Oubos (NMSA W5672), scale bars = 300 µm and 100 µm; (C, D) Capitina calcicola sp. n., Cape Agulhas (paratype, NMSA W3360/T2270), scale bars = 200 µm and 100 µm.

Fig. 74. Capitina calcicola sp. n., reproductive tract (paratype, NMSA W5670/T2265), scale bar = 5.0 mm. Abbreviations: ag – albumen gland, bc – bursa copulatrix, bd – bursa copulatrix duct, ep – epiphallus, fod – free oviduct, gp – genital pore, hd – hermaphrodite duct, oc – oviduct caecum, ot – ovotestis, p – penis, pr – penial retractor muscle, sod – spermoviduct, v – vagina, vd – vas deferens.

Fig. 76. Capitina calcicola sp. n., spermatophore, straightened length 8.2 mm (paratype, NMSA W5670/ T2265): (A) spermatophore in situ in dissected lower part of free oviduct; (B) two views of extracted spermatophore, scale bar = 3.0 mm.Abbreviations: bd – bursa copulatrix duct, fo – free oviduct wall with longitudinal folds, o – oviduct, obd – opening of bursa copulatrix duct, sh – spermatophore head, st – spermatophore tail, v – vagina, vd – vas deferens.

Fig. 78. Capitina species, living animals: (A) Capitina schaerfiae (Pfeiffer, 1861), Oubos, Riviersonderendberge (NMSA W5672), shell diameter 28.0 mm; (B) Capitina calcicola sp. n., Gansbaai (paratype, NMSA W3201/T2269), shell diameter 22.8 mm.

Fig.79. Distribution of Capitina species:C. schaerfiae (Pfeiffer, 1861) (triangles), C. calcicola sp. n. (squares). Symbols with a white centre indicate localities for specimens used in DNA analyses (Moussalli et al. 2009). Contour at 1000 m.

Fig. 80. Capitina calcicola sp. n. (all NMSA): (A–C) holotype, Cape Agulhas (W6265/T2262), diameter 28.0 mm; (D, E) boldly patterned specimen, Bantamsklip (paratype, W5998/T2266), diameter 28.4 mm; (F) elevated specimen, Cape Agulhas (paratype, W3360/T2270), diameter 28.0 mm; (G) Bredasdorp (paratype, BMNH 1937.12.30.1311–13), diameter 29.5 mm (photo courtesy of J.Ablett and P. Hurst); (H, I) weakly patterned specimen, Cape Agulhas (paratype,W3365/T2267), diameter 29.4 mm; (J) typical pattern, subadult specimen, Grootbos Private Nat. Res. (paratype, W5670/T2265), diameter 27.5 mm.

Fig. 81. Plot of height/diameter measurements of Capitina species, showing differing shell proportions in the two species. The largest specimen of C. schaerfiae (31.6 mm diameter) is missing its apex and cannot be included in this plot. Similarly, the height of the lectotype (31 mm diameter) cannot be measured from the photographs available.

Fig. 82. Distribution of genera within Natalina s.l.: Capitina (triangles), Afrorhytida (squares), Natalina (circles).

Fig. 83. Distribution of Afrorhytida and Capitina species in relation to biome type (Mucina & Rutherford 2006). The dashed line represents the approximate boundary between the western and eastern Cape Floristic Region.

Fig. 1. All compatible Bayesian consensus tree based on mixed model partitioned analysis of the combined nucleotide dataset (16S and COI = GTR + IΓ, ITS2 = GTR+I). Asterisk indicates nodal support>95 % posterior probability (PP); PP below 95 % are not shown. (From Moussalli et al. 2009)

Fig. 84. Distribution of Natalina species in relation to biome type (Mucina & Rutherford 2006).