A reconsideration of the systematic status of Rhoptropus bradfieldi ...

African Journal of Herpetology, 2001 50(2): 71-78.

Original article

A reconsideration of the systematic status of Rhoptropus bradfieldi diporus Haacke 1965 AARON M. BAUER1 AND TRIP LAMB2 1

Department of Biology, Villanova University, 800 Lancaster Avenue, Villanova, Pennsylvania 19085, USA [email protected] 2 Department of Biology, East Carolina University, Greenville, North Carolina 27858, USA Abstract.—We re-evaluated the taxonomic status of Rhoptropus bradfieldi diporus, an endemic Namibian gecko. Preanal pores, the character originally used to diagnose the taxon, are variably present, but R. b. diporus is reliably differentiated from R. b. bradfieldi by smaller, more rounded scalation of the thigh and precloacal regions. The two forms are also distinguished by relatively high levels of sequence divergence (9.7-11.6%) observed for the mitochondrial cytochrome b gene. On the basis of these distinct morphological and molecular characteristics, we regard R. diporus as a valid species restricted to the Brandberg and areas north of the Ugab River. The significance of consistent colour differences between R. diporus and R. bradfieldi remains unclear, but the melanism prevalent in the latter species may be an adaptation to the cool coastal Namib fog belt. Morphological variation in R. bradfieldi is also evident in the southern portion of its range, where inland and coastal populations are notably distinct. The precise geographic patterns of this variation (and its possible evolutionary significance) warrant further investigation. Key words.—Gekkonidae, Rhoptropus, Namibia, taxonomy.

he genus Rhoptropus is a demonstrably monophyletic group of diurnal geckos endemic to Namibia and Angola (Bauer & Good 1996; Lamb & Bauer 2001). Morphological, allozyme and mtDNA data sets support a single species level phylogeny for the genus (Lamb & Bauer 2001). Each of the six recognised species is well defined and easily diagnosed. However, the status of the subspecies R. boultoni montanus, R. boultoni benguellensis, and R. bradfieldi diporus, each currently regarded as valid (Wermuth 1965; Kluge 1993; Bauer & Good 1996; Branch 1998; Rösler 1999), remains problematic. The two subspecies of R. boultoni were described from Angola and are apparently restricted to the area north of the Kunene River. The limited recent material available for these two forms derive from too limited a set of localities to allow a meaningful evaluation of their taxonomic status. The existing political situation in

Angola precludes collection of additional material at present. However, the third subspecies, R. bradfieldi diporus, is a Namibian endemic for which relatively large numbers of specimens are available.

T

Haacke (1965) described Rhoptropus bradfieldi diporus on the basis of sixteen specimens from Farm Twyfelfontein and the Brandberg. He identified a single diagnostic character that distinguishes this form from the nominate subspecies; a pair of enlarged preanal scales, each of which (in males) bears a pore. These structures are clearly illustrated in the photographs of the pre-cloacal region provided by Haacke (1965). With respect to most other features for which Haacke (1965) provided comparative data, R. b. bradfieldi and R. b. diporus are indistinguishable. Haacke’s justification for the recognition of this new form as a subspecies, rather than a full species, was based on a series 71

AFRICAN JOURNAL OF HERPETOLOGY 50(2) 2001

of morphologically intermediate specimens. Material from Numas Gorge on the western side of the Brandberg as well as areas south of Tsissab Gorge exhibit some variation in the presence of pores and the degree to which preanal scales are enlarged. Haacke also reported that some features of R. b. diporus were present in two specimens (TM 28243, 28252) “from 50 and 95 mls. E. of Walvis Bay, respectively, along the Gamsberg road to Windhoek.” These intermediate specimens were collected among others that Haacke considered referable to the nominate form.

tinguishing northern and southern populations of R. bradfieldi were complemented by molecular markers. Tissue samples from eight specimens were processed at field collection sites and preserved in a saturated salt-DMSO buffer (Amos & Hoelzel 1991). Genomic DNA was extracted from liver using the Qiagen QIAamp DNA Mini kit. Portions of the mitochondrial cytochrome b (cytb) gene were used to assess sequence variation among specimens of R. bradfieldi. A single specimen of R. afer, the sister species to R. bradfieldi (Bauer & Good 1996, Lamb & Bauer 2001), was also included in the analysis. The primers L14724 and H15149 (Meyer et al. 1990) were used to amplify a 400 bp segment of the cytb gene. 50 ul reactions were amplified for 32 cycles at 92 °C for 45 sec, 55 °C for 35 sec, and 72 °C for 1 min. Amplification products were purified over Centri-sep columns and served as templates in cycle-sequencing reactions employing dyelabelled terminators (PRISM kit, Applied Biosystems, Inc.). PRISM reaction products were analysed on an Applied Biosystems 373A automated DNA sequencer. Forward and reverse sequences were generated for each sample and their complementarity confirmed using the Sequence Navigator software (Applied Biosystems, Inc.). Sequences were aligned using the CLUSTAL X program, applying default settings (Thompson et al. 1997). Pairwise sequence divergence estimates were derived using the Hasegawa-KishinoYano model (HKY85; Hasegawa et al. 1985), which assumes different evolutionary rates for transitions and transversions and unequal base frequencies. A neighbour-joining analysis was implemented in PAUP* (Swofford 1999).

We recently collected material of Rhoptropus cf. bradfieldi from near Gai-As, northern Namibia. Most specimens lacked preanal pores, as is typical for the nominate species, but one male (CAS 214605) clearly possessed the preanal pores diagnostic of R. b. diporus. This prompted us to re-examine other specimens of R. bradfieldi we had previously collected in the region in an attempt to determine if more reliable characters might be used to distinguish diporus or, alternatively, if continued recognition of the two subspecies was warranted.

MATERIALS AND METHODS Scale features and colour patterns were examined on all specimens of Rhoptropus bradfieldi in the collections of the California Academy of Sciences (CAS) and the Carnegie Museum of Natural History (CM) and selected material (including the types of R. bradfieldi) from the Port Elizabeth Museum (PEM) (see Appendix). These data were compared to those previously recorded for specimens from other collections, including the Transvaal Museum (TM; now Flagship Institution of the North) and the National Museum of Namibia (SMW), in association with earlier research (Bauer & Good 1996).

RESULTS Few of the specimens that we examined possessed the typical preanal pores of R. b. diporus. However, we did note a consistent difference in another character between the northern and southern specimens examined.

DNA sequence analysis was also conducted to determine whether morphological features dis72

BAUER & LAMB — Systematic status of Rhoptropus bradfieldi diporus

Nominate specimens, including the syntypes of R. bradfieldi (PEM R15874-75), are typified by enlarged precloacal scales, some or many of which have more-or-less straight-sided distal borders. Scales of the thighs are similar or otherwise elongate and nearly straight-sided (Fig. 1A-C). In contrast, specimens from the Khorixas District possess thigh and precloacal scales that are both absolutely and relatively smaller. This scalation also grades more gradually in size towards the smaller scales adjacent to the cloacal lips and margins of the thigh. Finally, the scales are generally more rounded in outline than those observed in southern specimens (Fig. 1D-F).

grey to grey above. He noted that this difference was unrelated to sex but speculated that it might relate to the time of day of collection (and presumably fixation). Our southern coastal specimens (Swakopmund to Cape Cross) were blackish in dorsal colouration (Fig. 2A-B), whereas northern specimens (Ugab River and north) were a paler gray, with especially pale venters (Fig. 2C-D). Specimens from southern inland localities (Roessing Mountain, Gobabeb, 19 km ENE Arandis), however, did not fit the north-south trend; rather, they exhibited the paler pattern. Differences in colouration were independent of sex or age and, at least for the specimens collected by us, time of fixation.

Northern and southern individuals also differed consistently from nominate R. bradfieldi in colour pattern. This is in contrast to the situation noted by Haacke (1965), who indicated that the type series of R. b. diporus included individuals whose preserved colour pattern was black above and others that were brownish-

Pairwise comparisons of the cytb sequence data revealed that all R. bradfieldi had genetic distances > 0.2 from R. afer. Distances within the southern and northern samples of R. bradfieldi were small (southern = 0.00618-0.01241; northern = 0.00000-0.01247), whereas consid-

Figure 1. Ventral views of the thighs and cloacal regions of representative specimens of Rhoptropus bradfieldi (AC) and R. diporus (D-F). A) CAS 193911 (adult male), Hentiesbaai Rd., 30.0 km N of Swakopmund, Swakopmund District, Erongo Region, Namibia; B) CAS 193914 (adult male), same locality as A); C) CAS 214575 (adult female) Hentiesbaai Rd., 29.0 km N of Swakopmund, Swakopmund District, Erongo Region, Namibia (22°25'38"S, 14°27'53"E); D) CAS 214604 (adult female), vicinity of Gai-As, Khorixas District, Kunene Region, Nambia (20°47'18"S, 14°06'44"E)., E) CAS 214605 (adult male), same locality as D); F) CAS 214772 (adult male), Skeleton Coast National Park, N bank of Huab River at Huab River Bridge, Khorixas District, Kunene Region, Namibia (20°54'04"S, 13°31'30"E). Note the enlarged pre-cloacal and thigh scales and numerous straightedged and elongate scales (arrows) in A-C, and the smaller scales, dimpled or pore-bearing scales (arrows), and more rounded scale margins in D-F. 73


erably higher levels of divergence were observed for all north-south comparisons (0.09741- 0.11567). A neighbour-joining tree unambiguously separated specimens from GaiAs and the lower Huab Valley from those of the Swakopmund-Cape Cross corridor.

DISCUSSION Pairwise comparisons between the recognised full species of Rhoptropus yield genetic distance values for cytb in the range of 19-27%, whereas intraspecific comparisons reveal almost no divergence whatsoever in any species except R. bradfieldi (Lamb & Bauer 2001). Interspecific distances for 16S rRNA sequences are somewhat lower (9-15%), but still substantial, whereas intraspecific distances were near zero (Lamb & Bauer 2001). The values revealed between R. b. bradfieldi and R. b. diporus are intermediate (9.7-11.6% for cytb, this study, Table 1; 3.9% for 16S rRNA, Lamb & Bauer 2001). Although lower than the other interspecific comparisons in Rhoptropus, the genetic distances observed between diporus and nominate bradfieldi fall in the middle to higher end of divergence values reported for reptile (and other vertebrate) congeners with respect to cytb sequence divergence (Johns & Avise 1998). Genetic distance values within R. bradfieldi clearly reflect substantive phylogeographic structure and also correspond to the differences in pre-cloacal and thigh scalation noted above. On this basis R. b. bradfieldi and R. b. diporus are diagnosable taxa that are evolving along independent trajectories. As such, we formally recognise Rhoptropus diporus Haacke 1965 as a distinct species. Although Haacke’s original diagnostic feature, reflected in the specific epithet, remains useful for identifying some specimens, especially those near the type locality at Twyfelfontein, we regard the differences in ventral scalation size and shape as more broadly applicable diagnostic features.

Figure 2. Dorsal (A) and ventral (B) views of Rhoptropus bradfieldi (CAS 214574, adult female) from Hentiesbaai Rd., 29.0 km N of Swakopmund, Swakopmund District, Erongo Region, Namibia (22°25'38"S, 14°27'53"E) and dorsal (C) and ventral (D) views of Rhoptropus diporus (CAS 214604, adult female) from the vicinity of Gai-As, Khorixas District, Kunene Region, Nambia (20°47'18"S, 14°06'44"E). Note the darker colour of the former taxon, which is consistent in northern coastal populations.

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BAUER & LAMB — Systematic status of Rhoptropus bradfieldi diporus Table 1. HKY85 distance matrix based on cytochrome b sequence data. Specimen 1. CAS 206951 2. CAS 193898 3. CAS 193897 4. CAS 214603 5. AMB 5932 6. CAS 206957 7. CAS 214605 8. CAS 214772 9. CAS 193868

Taxon bradfieldi bradfieldi bradfieldi diporus diporus diporus diporus diporus afer

Locality vic. Cape Cross vic.Hentiesbaai vic.Hentiesbaai vic. Gaias vic. Gaias vic. Gaias vic. Gaias Huab River vic. Hentiesbaai

1

2

3

4

5

6

7

8

— 0.00618 0.01241 0.09741 0.09741 0.09741 0.09741 0.11254 0.22923

— 0.00618 0.09711 0.09711 0.09711 0.09711 0.11218 0.22068

— 0.10055 0.10055 0.10055 0.10055 0.11567 0.21224

— 0.00000 0.00000 0.00000 0.01247 0.20272

— 0.00000 0.00000 0.01247 0.20272

— 0.00000 0.01247 0.20272

— 0.01247 0.20272

— 0.19847

As previously construed, Rhoptropus bradfieldi had a limited distribution extending from the south bank of the Kuiseb River north to the region of Twyfelfontein (Haacke & Odendaal 1981; Bauer & Good 1996), making it the only member of the genus strictly endemic to the Republic of Namibia. On the basis of our results, we would regard the range of R. bradfieldi, sensu stricto, as extending north along the coast to the Cape Cross area and inland to the (unspecified) type locality on the Messum River (Fig. 3). On the basis of Haacke’s (1965) report, the species probably also extends to the southern and western approaches to the Brandberg. Rhoptropus diporus occurs as far north as Farm Vrede (2014Ac) along the Huab River (Bauer et al. 1993) and has been taken on the north bank of the Huab a few km inland from the river mouth. It extends southward through Twyfelfontein to at least the Ugab River and the Brandberg (Haacke 1965; van den Elzen 1983) (Fig. 3). Figure 3. Map of west central Namibia showing the localities of specimens examined and relevant landmarks. Rhoptropus bradfieldi localities are indicated by open squares. The type locality (“Messum River”) is represented by a question mark inside a square to indicate uncertainty about precise origin of the types along the Messum River. Rhoptropus diporus localities are indicated by stars in circles. The type locality is indicated by a black star. The locality of Hewitt’s “Ugab” material is indicated by a question mark inside a circle, indicating uncertainty about the precise origin of the specimens along the Ugab River. Asterisks (*) indicate the localities from which material for DNA sequencing was obtained. The Brandberg is indicated in grey and coastal reference points are labelled and designated by hollow circles. Although only selected localities have been plotted, the map encompasses the entire range of both R. diporus (Brandberg and north to the Huab drainage) and R. bradfieldi (Kuiseb River north at least as far as the Messum River).

The border between the two forms in the vicinity of the Brandberg and the Ugab River remains unclear. Hewitt (1935), who noted that specimens from “Ugab” were much paler, both dorsally and ventrally, than the R. bradfieldi types from “Messum River,” provided the first evidence that two taxa might be present in the area surrounding the Brandberg. He did not mention the presence of preanal pores in the material he examined, but our re-examination of his material from “Ugab” reveals that PEM R15877, an adult male, has one dimpled scale corresponding to the left pore position, and 75


PEM R15878, an adult female, has a pair of dimpled scales in the position typical for female R. diporus. All three Ugab specimens also possess the typical ventral scalation pattern of R. diporus. Haacke (1965) noted the intermediate condition of some specimens from the Brandberg with respect to pore presence, but we suspect that most, if not all, material from the Brandberg possesses the ventral scalation pattern of R. diporus, regardless of the level of development of preanal pores.

not strictly consistent in their morphological features with those from the vicinity of the type locality and vary significantly in details of colour pattern. Most inland specimens are pale coloured and at least some exhibit thigh and/or pre-cloacal scale features that are intermediate between R. diporus and R. bradfieldi. Further, although we did not observe any southern inland specimens with preanal pores, Haacke (1965) reported dimpled pre-cloacal scales for several specimens from this area.

Despite the limited number of localities, it appears that all populations north of the Ugab are referable to R. diporus and that this form is also present south of the Ugab in the vicinity of the Brandberg. Several possibilities exist as to the cladogenetic event responsible for the division of these two taxa. It is possible that the Ugab River, which during past periods of high precipitation was a potentially significant barrier to dispersal (Grünert 2000), may have divided once continuous ancestral populations into northern and southern phylogroups. As such, the Brandberg population of R. diporus south of the Ugab would likely reflect a subsequent trans-Ugab colonisation. Alternatively, speciation may have occurred along ecological lines. We routinely found typical R. bradfieldi in association with dark granite boulders in nearcoastal localities from Swakopmund to Cape Cross. Similar habitats are utilised by this form at the southern end of its range between the Kuiseb and Swakop rivers (Haacke & Odendaal 1981). However, all of the R. diporus we collected were associated with sandstone or granite koppies or walls of rock, as opposed to isolated boulder clusters.

The significance of the colour difference noted between populations is unclear. As has been demonstrated in a variety of reptile species (Zug et al. 2001), colour may be related to substrate matching. Another plausible explanation is to regard the darker pattern of coastal R. bradfieldi as an adaptation to the frequently fog-bound, cool coastal Namib habitat, whereas both R. diporus and inland populations of R. bradfieldi retain a paler, ancestral colouration. However, dark colouration also characterises the inland species R. boultoni. Moreover, R. diporus only a few km inland from the Huab River mouth retain the paler pattern, despite their occurrence in the advective fog belt. Even if colouration is adaptive, its utility as a taxonomic character remains uncertain. For example, members of the Cordylus cordylus group have evolved melanistic colouring in association with the cool, coastal and montane climates of the southwestern Cape (Mouton 1987; Mouton & Oelofsen 1988; Mouton & van Wyk 1990). In this instance melanism has accompanied significant morphological and genetic changes, reflecting regional speciation. Conversely, melanism in the Cordylus polyzonus complex, which also inhabits cool, coastal regions, is not linked to significant genetic differentiation (P.le F.N. Mouton, pers. comm.). Likewise, among geckos, inland populations of Pachydactylus bicolor are capable of dramatic colour changes, from a dark chocolate background with pale white spots to a much lighter mottled appearance (see photographs in Branch 1998). In contrast, coastal

The status of southern inland populations of R. cf. bradfieldi remains problematic. Our genetic comparisons were limited to specimens from near-coastal localities and sites north of the Ugab River. Thus, we have not been able to assess levels of genetic variation in R. bradfieldi across its entire range. This is a significant issue given that southern inland populations are 76

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tion of the genus Rhoptropus (Reptilia, Gekkonidae) in the central Namib Desert. Madoqua 12: 199-215. HASEGAWA, M., H. KISHINO & T. YANO. 1985. Dating the human-ape splitting by a molecular clock of mitochondrial DNA. J. Mol. Evol. 22: 160-174. HEWITT, J. 1935. Some new forms of batrachians and reptiles from South Africa. Rec. Albany Mus. 4: 282-357, pls. 27-36. JOHNS, G.C. & J.C. AVISE. 1998. A comparative summary of genetic distances in the vertebrates from the mitochondrial cytochrome b gene. Mol. Biol. Evol. 15: 1481-1490. KLUGE, A.G. 1993. Gekkonoid Lizard Taxonomy. International Gecko Society, San Diego. LAMB, T. & A.M. BAUER. 2001. Mitochondrial phylogeny of Namib day geckos (Rhoptropus) based on cytochrome b and 16SrRNA sequences. Copeia. 2001: 775-780. MEYER, A., T.D. KOCHER, P. BASASIBWAKI & A.C. WILSON. 1990. Monophyletic origin of Lake Victoria cichlid fishes suggested by mitochondrial DNA sequences. Nature 347: 550-553. MOUTON, P.LE F.N. 1987. Phenotypic variation among populations of Cordylus cordylus (Reptilia: Cordylidae) in the south-western Cape Province, South Africa. S. Afr. J. Zool. 22: 119-129. MOUTON, P.LE F.N. & B.W. OELOFSEN. 1988. A model explaining patterns of geographic character variation in Cordylus cordylus (Reptilia: Cordylidae) in the south-western Cape, South Africa. S. Afr. J. Zool. 23: 20-31. MOUTON, P.LE F.N. & J.H.VAN WYK. 1990. Taxonomic status of the melanistic forms of the Cordylus cordylus complex (Reptilia: Cordylidae) in the south-western Cape, South Africa. S. Afr. J. Zool. 25: 31-38. RÖSLER, H. 1999. Kommentierte Liste der rezent, subrezent und fossil bekannten Geckotaxa (Reptilia: Gekkonomorpha). Gekkota 2: 28-153. SWOFFORD, D.L. 1999. PAUP*: Phylogenetic Analysis Using Parsimony (and Other Methods), Version 4.0. Sinauer, Sunderland, Massachusetts. THOMPSON, J. D., T. J. GIBSON, F. PLEWNIAK, F. JEANMOUGIN, & D. G. HIGGINS. 1997. The CLUSTAL X windows interface: flexible strategies for multiple sequence alignment aided by quality analysis tools. Nucleic Acids Res. 24: 4876-4882. VAN DEN ELZEN, P. 1983. Zur Herpetofauna des Brandberges, Südwest-Afrika. Bonn. zool. Beitr. 34: 293-309. WERMUTH, H. 1965. Liste der rezenten Amphibien und Reptilien, Gekkonidae, Pygopodidae, Xantusiidae. Das Tierreich 80. Walter de Gruyter, Berlin. ZUG, G.R., L.J. VITT & J.P. CALDWELL. 2001. Herpetology, an Introductory Biology of Amphibians and Reptiles, 2nd ed. Academic Press, San Diego.

populations inhabiting boulders between Swakopmund and Cape Cross appear incapable of blanching to the lighter pattern but are not genetically distinct (pers. obs.). A genetic survey of southern inland R. bradfieldi will be required to determine whether populations from this region exhibit substantive phylogeographic structure, or merely reflect labile responses to local conditions.

ACKNOWLEDGEMENTS We thank Bill Branch, Jens Vindum, Robert Drewes, John Wiens and Stephen Rogers for the loan of the material examined. Le Fras Mouton (University of Stellenbosch) provided information about melanism in cordylids. Permission to collect in the Republic of Namibia and the Skeleton Coast Park were provided by the Ministry of the Environment and Tourism. In particular, we thank Mike Griffin for his continued support of our research in Namibia. Photographs for Figs. 1 and 2 were taken by Dong Lin (CAS). This research was funded by a grant to the authors from the National Science Foundation of the United States (DEB-9707568).

LITERATURE CITED AMOS, B.& A.R. HOELZEL. 1991. Long-term preservation of whale skin for DNA analysis. Rep. Int. Whal. Comm. Spec. Iss. 13: 99-103. BAUER, A.M., W.R. BRANCH & W.D. HAACKE. 1993. The herpetofauna of the Kamanjab area and adjacent Damaraland, Namibia. Madoqua 18: 117-145. BAUER, A.M. & D.A. GOOD. 1996. Phylogenetic systematics of the day geckos, genus Rhoptropus (Reptilia: Gekkonidae), of south-western Africa. J. Zool., Lond. 238: 635-663. BRANCH, W.R. 1998. Field Guide to the Snakes and Other Reptiles of Southern Africa, 3rd ed. Struik Publishers, Cape Town. GRÜNERT, N. 2000. Namibia, Fascination of Geology. Klaus Hess Publishers, Windhoek. HAACKE, W.D. 1965. Additional notes on the herpetology of South West Africa with descriptions of two new subspecies of geckos. Cimbebasia 11: 1-40. HAACKE, W.D. & F.J. ODENDAAL. 1981. The distribuReceived: 5 May 2001;

Final acceptance: 5 November 2001. 77


Rd. (21°49'54"S, 14°04'13"E) - CAS 206951; 13.0 km S of Cape Cross turnoff on Hentiesbaai Rd. - CAS 167676; 13.2 km S of Cape Cross turnoff on Hentiesbaai Rd. - CAS 175393; 38.7 km N of Hentiesbaai-Usakos Rd. jct. on road to Cape Cross - CAS 176228-30; Messum River (possibly Omaruru District PEM R15874-75 (ex Albany Museum 6575, syntypes of Rhoptropus bradfieldi); Heichamchab (Geigamkab) - PEM R15880-81 (ex Albany Museum 6548).

APPENDIX Material examined (all specimens from the Republic of Namibia): Rhoptropus afer: Erongo Region, Swakopmund District, Hentiesbaai Rd., 30.0 km N of Swakopmund - CAS 193868 (specimen used for molecular comparisons only). Rhoptropus bradfieldi (all specimens from Erongo Region, Swakopmund District unless otherwise noted): Namib Desert Research Station, Gobabeb - CM 58217; 19 km ENE of Arandis (22°21'S, 15°10'E) - CM 115680, 115715, 115717, 115723-24, 115752; 35.2 km E of Swakopmund - CAS 126144-48; 16.0 km E of Swakopmund - CAS 126160; Roessing Mountain, 2.7 km N of Usakos-Swakopmund Rd. and 35.7 km E of Swakopmund - CAS 167673-75; Hentiesbaai Rd., 29.0 km N of Swakopmund (22°25'38"S, 14°27'53"E) - CAS 214571-75; Hentiesbaai Rd., 30.0 km N of Swakopmund - CAS 193892-917, 200603-04; 11.3 km S of Cape Cross turnoff on Hentiesbaai

Rhoptropus diporus (all specimens from Kunene Region, Khorixas District): Ugab PEM R15877-79 (ex Albany Museum 6574); 22.7 km N of Ugab River crossing on road from Brandberg West Mine (20°47'17"S, 14°06'41"E) - CAS 206957, AMB (Aaron M. Bauer Field Series) 5932 (to be catalogued in SMW collection); vic. Gai-As (20°47'18"S, 14°06'44"E) - CAS 214603-08; Skeleton Coast National Park, N bank of Huab River at Huab River Bridge (20°54'04"S, 13°31'30"E) - CAS 214771-2.

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