Several specimens of Pachydactylus angolensis, a poorly known Angolan endemic gecko, have recently been collected in southern Angola, considerably increasing its known distribution range. Previous observations led to the hypothesis that two different morphological forms exist in the country—a coastal form and an inland form. Based on the morphological examination of historical and recently collected specimens, as well as on newly generated molecular data, we conducted a taxonomic revision of this putative species complex. The results support the separation of these two forms as two different species. The coastal form belongs to the nominotypic population, while the inland form is here described as a new species, Pachydactylus maiatoi sp. nov.. A brief comment on the biogeographical implications of this discovery is also provided.

Vários espécimes de Pachydactylus angolensis, uma osga endémica de Angola, rara e pouco conhecida, foram recentemente coletados no sul de Angola, aumentando consideravelmente a sua área de distribuição conhecida. Observações anteriores levantaram a hipótese da existência de duas formas morfológicas distintas no país — uma forma costeira e outra das regiões interiores. Com base na observação morfológica de espécimes históricos e recentes, bem como dados moleculares gerados recentemente, levou-se a cabo a revisão taxonómica deste putativo complexo de espécies. Os resultados suportam a separação destas duas formas em duas espécies diferentes. A forma costeira pertence à população nominotípica, enquanto a forma das regiões interiores é aqui descrita como uma nova espécie, Pachydactylus maiatoi sp. nov.. Apresentam-se ainda as implicações biogeográficas desta nova descoberta.

Africa, biogeography, integrative taxonomy, reptiles, type specimens

África, biogeografia, espécimes tipo, répteis, taxonomia integrativa

The genus Pachydactylus Wiegmann, 1834 is represented in Angola by 10 species (Marques et al. 2018; Branch et al. 2019b; Lobón-Rovira et al. 2022), namely P. angolensis Loveridge, 1944, P. caraculicus FitzSimons, 1959, P. parascutatus Bauer, Lamb & Branch, 2002, P. cf. punctatus Peters, 1854, P. cf. oreophilus McLachlan & Spence, 1976, P. rangei (Anderson, 1908), P. scherzi (Mertens, 1954), P. cf. rugosus Smith, 1849, P. wahlbergii (Peters, 1869), and P. vanzyli (Steyn & Haacke, 1966). Laurent (1964) considered Pachydactylus amoenoides Hewitt, 1935 as a distinct species from P. punctatus based on their sympatry in southern regions of Angola (Marques et al. 2018). Bauer and Branch (1995) synonymized P. amoenoides with P. punctatus, although the taxonomic status of P. amoenoides is currently being reviewed (Bauer et al. unpublished). Currently the genus accommodates 57 recognized species (Uetz et al. 2022) across its southern African distribution and together with its close relatives Chondrodactylus Peters, 1870 and Elasmodactylus Boulenger, 1895, it comprises the most successful and diverse radiation of lizards in southern Africa (Heinicke et al. 2017). Recent species-level phylogenies have provided important insights about the diversification of the genus and defined several species groups (Bauer 1999; Bauer and Lamb 2005; Heinicke et al. 2017). Of special interest for this study is the “northwestern group” to which all but four of the species of Pachydactylus occurring in Angola (P. rangei, P. vanzyli, P. cf. rugosus and P. wahlbergii) belong. The members of this “northwestern group” as defined by Bauer (1999), Bauer and Lamb (2005) and most recently by Heinicke et al. (2017) are restricted to northern Namibia and southwestern Angola, with the exception of the P. punctatus species complex which extends to South Africa, Botswana, Mozambique, Malawi, Zambia and the Democratic Republic of the Congo (Heinicke et al. 2011). The group comprises the P. punctatus species complex, P. scherzi, P. caraculicus, P. angolensis, P. parascutatus, P. scutatus Hewitt, 1927, P. gaiasensis Steyn & Michell, 1967, the P. oreophilus species complex, P. sansteynae Steyn & Michell, 1967, P. otaviensis Bauer, Lamb & Branch, 2006, P. boehmei Bauer, 2010, P. maraisi Heinicke, Adderly, Bauer & Jackman, 2011, and P. bicolor Hewitt, 1926 (Heinicke et al. 2017).

Despite a considerable number of Pachydactylus species being described in recent decades (Bauer et al. 2002, 2006a, 2006b; Branch et al. 2011; Heinicke et al. 2011), undescribed cryptic diversity remains (Bauer and Branch 1995; Heinz 2011; Branch et al. 2017). Part of this diversity is found in some populations of taxa that either occur or are endemic to Angola. This is the case of P. cf. oreophilus and P. cf. rugosus, whose Angolan and some northern Namibian populations are already known to represent putative new species (Bauer et al. unpublished; Lobón-Róvira et al. 2022), or even the case of the P. punctatus species complex, signaled long ago as a species complex by Bauer and Branch (1995) and Heinz (2011), and whose Angolan populations are currently being evaluated and described as new (Marques et al. unpublished). This also seems to be the case of the Angolan endemic P. angolensis. The taxon was described by Loveridge (1944) as Pachydactylus scutatus angolensis, based on three specimens collected in coastal regions of Benguela Province by Arthur Vernay, Herbert Lang and Rudyerd Boulton in 1925 during the American Museum of Natural History Vernay-Lang Angolan Expedition. In their review of the Pachydactylus scutatus group, Bauer et al. (2002) re-examined the type specimens and elevated P. s. angolensis to a full species, closely allied to P. scutatus. Bauer and Lamb’s (2005) phylogeny of southern African Pachydactylus did not include P. angolensis due to the lack of genetic material at the time but suggested that the species should belong to the “northwestern clade” of the genus, which was later confirmed by Heinicke et al. (2011). Heinicke et al. (2017) found that P. angolensis was sister to P. caraculicus, instead of being closely related to P. scutatus as supposed before. The holotype is from Hanha, a small town 6 km inland from the coast and on the border of the Cacubi river [–12.2450°, 13.7075°], whereas the two paratypes were collected approximately 20 km south, at Lobito Bay [–12.3500°, 13.5500°]. Additional details regarding the type locality of P. angolensis were provided by Branch et al. (2017), who noted the historical confusion between Hanha do Norte and Hanha do Cubal, two geographically proximate localities bearing a similar name, as already noted by Bauer et al. (2002). The authors confirmed Bauer et al.’ (2002) assumption that Hanha do Norte is the correct type locality for this species (Branch et al. 2017). The type series is still present in the collections of the American Museum of Natural History (AMNH), New York, which holds the holotype and one paratype, AMNH R47874 (Fig. 1) and AMNH R47872, respectively, and in the collections of the Museum of Comparative Zoology (MCZ), Massachusetts, which is the repository of the remaining paratype (MCZ R46856).

Figure 1. 

Holotype (AMNH R47874) of P. angolensis, from Hanha, Benguela Province, Angola. Photo by Luis M.P. Ceríaco.

Subsequent records were given by Laurent (1964), who reported on four specimens from the “environs de Moçamedes”, one of which was collected in the coastal region of “Praia das Conchas” [–15.1333°, 12.1167°], while the other three were collected by the side of the road that connects Sá da Bandeira (now Lubango) to Moçâmedes (precise locality impossible to georeference). These specimens are still extant in the collections of the Museu Regional do Dundo (MD), in Lunda Norte Province, under the catalogue number MD 1931 (Ceríaco et al. 2020c).

Further specimens of this species were collected by Charles Koch, on an expedition to southwest Angola in September 1956, as well as Wulf D. Haacke in 1971 and 1974. Koch’s and Haacke’s specimens were deposited in the Transvaal Museum (TM; today Ditsong National Museum of Natural History) but these records were only published much later by Bauer (2010), Ceríaco et al. (2016), and Branch et al. (2017). These included specimens collected in Namibe Province, namely in São Nicolau, Bentiaba [–14.2667°, 12.3833°], Lucira [–13.8667°, 12.5333°], Lungo [–14.3167°, 13.2000°], São Nicolau [–14.2577°, 12.3969°] and Saco do Giraul [–15.0688°, 12.1422°], and from Benguela Province, namely Hanha, 20 km north of Lobito [–12.2585°, 13.6734°], Benguela, 24 km south [–12.6975°, 13.2522°], and 30 km north of Dombe Grande [–12.7309°, 13.2302°].

Due to the violent civil war that afflicted Angola from 1975 to 2002, decades passed without the sighting or the collection of additional specimens of this species in Angola. Between 2013 and 2019 several specimens of this species were collected in both Namibe and Benguela provinces by our team. In December 2013 a juvenile specimen was collected during the California Academy of Sciences (CAS), Villanova University (VU) and Instituto Nacional da Biodiversidade e Áreas de Conservação (INBAC) joint expedition to southwestern Angola. This specimen (CAS 254887), reported by Ceríaco et al. (2016), was collected in a rocky outcrop, covered with vegetation, in the south side of the Namibe-Lubango road, 2 km East (by road) of Mangueiras [–15.0436°, 13.1600°]. This was the most inland record for the species. Two years later, during a subsequent expedition to the southwestern regions of Benguela Province, a total of ten specimens, agreeing with the topotypical and coastal coloration pattern, were collected in the Chimalavera Regional Natural Park (Fig. 2).

Figure 2. 

A Life photo of a juvenile Pachydactylus angolensis from Chimalavera Regional Natural Park (CAS 266480). B General view of the habitat in Chimalavera Regional Natural Park. Photos by Luis M.P. Ceríaco.

Approximately 180 km southeast of Chimalavera, in August 2018, two of the authors of this study (MPM and LMPC) collected an additional specimen of P. angolensis under some rocks near the old Portuguese fort of the coastal town of Bentiaba [–14.2733°, 12.3850°] (Fig. 3).

Figure 3. 

A Life photo of Pachydactylus angolensis from Bentiaba (CAS 264237). B General view of the old Portuguese fort at Bentiaba and its surrounding habitat. Photos by Luis M.P. Ceríaco.

At around the same time, during surveys further inland in Namibe Province — mostly in the Serra da Neve inselberg and the surrounding regions of Maungo — additional specimens resembling P. angolensis were collected. These were, however, morphologically different from all the remaining coastal material collected so far, having a duller dorsal coloration without the presence of any kind of scattered white spots (as reported by Loveridge (1944) in the original description), a character present in all other coastal specimens. Branch et al. (2017) reported a similar observation between the coastal and inland populations of P. angolensis, which they labeled as the “coastal form” and the “inland form”. Besides the records of the specimens available in the TM (cited above), Branch et al. (2017) provided reference to two photo-vouchers, one from Chimalavera to illustrate the “coastal form” and another from Serra da Tchivira [–14.3167°, 13.8833°] to illustrate the “inland form”.

Together with the review of the existing historical specimens of P. angolensis, these newly collected specimens from several localities across southwestern Angola allowed us to investigate the taxonomic identity of these two forms in Angola. Based on a combination of morphological, meristic, and coloration characters and DNA sequence data, we found evidence that supports the recognition of the “coastal” and “inland” forms of P. angolensis as two different taxa. We adopt the general lineage species concept (de Queiroz 1999) and recognize the “inland form” of P. angolensis as a separate and previously undescribed species.

In order to stabilize the taxonomy and to provide an improved estimate of the distribution of the genus in southern Africa, we describe the inland form as a new species and provide additional data on the distribution and ecology of these two taxa. Presumptive specimens of P. angolensis from far northern Namibia have been determined to be P. parascutatus (Marques et al. 2018).

Newly collected specimens for this study were euthanized with MS-222 following an approved IACUC protocol (Villanova University #1866), fixed in 10% buffered formalin in the field, and transferred to 70% ethanol for long-term storage at the conclusion of field work. Liver tissue was removed before formalin fixation and preserved in either RNAlater and transferred to 95% ethanol or directly in 95% ethanol for long-term storage. For mensural and meristic comparisons, we examined other Angolan and Namibian Pachydactylus specimens (including the type series of P. angolensis), deposited in the collections of the American Museum of Natural History (AMNH), New York, U.S.A.; the California Academy of Sciences (CAS), San Francisco, U.S.A.; the Museum of Comparative Zoology (MCZ), Harvard University, Cambridge, Massachusetts, U.S.A.; the Museu Nacional de História Natural e da Ciência da Universidade de Lisboa (MUHNAC), Lisboa, Portugal; the Museu Regional do Dundo (MD), Dundo, Angola; the Instituto Nacional da Biodiversidade e Áreas de Conservação (INBAC), Kilamba-Kiaxi, Angola; and the Ditsong National Museum of Natural History (TM), Pretoria, Gauteng, South Africa.

Southwestern Angola has been recognized by several authors as a hotspot of diversity for reptiles, especially associated with arid and hyper-arid habitats (Ceríaco et al. 2016; Marques et al. 2018; Branch et al. 2019b). This is particularly true for lizards, as suggested by the description of several endemic or near-endemic species in the last decade, including six lacertids (Conradie et al. 2012; Branch et al. 2019a; Parrinha et al. 2021; Marques et al. 2022), six gekkonids (Ceríaco et al. 2020b; Marques et al. 2020; Branch et al. 2021; Lobón-Rovira et al. 2022a), one scincid (Ceríaco et al. 2020a) and two cordylids (Stanley et al 2016; Marques et al. 2019). Gekkonids are particularly diverse in the region, with more than half of Angolan species recorded in Iona National Park alone (Lobón-Rovira et al. 2022b). The description of Pachydactylus maiatoi sp. nov. represents the most recent addition to the gekkonid fauna of Angola, raising the number of Angolan Pachydactylus to 11, and to a total of 58 recognized species in the genus. However, this number is expected to rise with further works on the taxonomy of Angolan Pachydactylus, as cryptic diversity identified in other groups within the genus awaits formal description. This is especially true for the P. cf. punctatus group, for which an ongoing revision is being prepared (Bauer et al. unpublished).

While these discoveries highlight the significance of southwestern Angola as a hotspot of diversity and endemism, considerable areas remain largely unexplored in terms of biodiversity and require further surveys and research efforts. The study of the Angolan radiation of Pachydactylus represents yet another contribution to the overall knowledge of biogeographic patterns in southwestern Angola. While the region supports endemic lizards that are generally widespread (e.g., Pedioplanis haackei Conradie, Measey, Branch & Tolley, 2012), it also hosts more geographically restricted endemics, like Pedioplanis huntleyi Conradie, Measey, Branch & Tolley, 2012 in the mountainous areas of southeastern Namibe Province, and several recently described species known only from the Serra da Neve inselberg (e.g., Lygodactylus baptistai Marques et al., 2020, Afroedura praedicta Branch et al., 2021, Cordylus phonolithos Marques et al., 2019). Pachydactylus angolensis as currently construed joins other gekkonids (e.g., Hemidactylus vernayi Ceríaco, Agarwal, Marques & Bauer, 2020, Bauerius ansorgii (Boulenger, 1907)) and lacertids (e.g., Pedioplanis benguelensis (Bocage, 1867)) in a group of lizards endemic to the coastal areas of Namibe and Benguela provinces. This narrow, low elevation (< 500 m a.s.l.) coastal belt between Moçâmedes and Benguela experiences cooler temperatures and less precipitation than the central plains to the east, and has been suggested to be particularly affected by fog and low clouds resulting from the cooling effect of the upwelling Benguela Current (Huntley 2019), an important source of water in the arid and hyper-arid habitats of southwestern Africa. Although no detailed data on the occurrence and effects of fog is available for Angola, previous authors have suggested that it plays an important role in the ecology of the arid savannas of coastal Angola (Pinto et al. 2019). The diversity and distribution of endemic lizards in southwestern Angola suggests the existence of complex biogeographical patterns resulting from the interaction between climate and topography, which shall be investigated elsewhere.

The present work is a result of the ongoing collaboration between the Instituto Nacional de Biodiversidade e Áreas de Conservação (INBAC) from the Ministry of Environment of Angola and its international partners. Angolan specimens were collected and exported under permits issued by INBAC (155/INBAC.MINAMB/2017; 28/INBAC.MINAMB/2019). We also thank the provincial and local authorities for their support and cooperation during our fieldwork. We thank Ishan Agarwal, Suzana Bandeira, Joyce Janota, Hilária Valério, Sango de Sá, Edward L. Stanley, David C. Blackburn, Jens V. Vindum, Arianna Kuhn, and Pedro Baptista for their support during field work and collecting valuable material. Special thanks to Álvaro (“Varito”) Baptista and his team from Omahua Lodge, for all the assistance, great support, and friendship during the field work.

As in any major taxonomic revision, the access to Natural History Collections is critical, and therefore the authors want to present a special acknowledgement to the collection managers and curators who provided access and data from the collections under their care: David Kizirian and Lauren Vonnahme from the American Museum of Natural History (AMNH); Lauren Scheinberg and Erica Ely from the California Academy of Sciences (CAS); José Rosado from the Museum of Comparative Zoology (MCZ); Ilunga André from the Museu Regional do Dundo (MD); Moleboheng Mohapi from the Ditsong National Museum of Natural History (TM); Shiela Broadley from the Natural History Museum of Zimbabwe (NMZB).

This work was funded by U.S. National Science Foundation grants (DEB 1556255, 1556585, 1556559, 1657527), a grant from JRS Biodiversity Foundation to AMB, MPH, and David C. Blackburn, and the National Geographic Society Explorer Grant (NGS-73084R-20) to LMPC. LMPC was funded by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) of the Ministry of Education of Brazil, under the Programa Institucional de Internacionalização (PRINT), process number 88887.695166/2022-00. DMP is supported by Fundação para a Ciência e Tecnologia (FCT) grant (05238/2021.BD). MPM was supported FCT grants (SFRH/BD/129924/2017, COVID/BD/152155/2022). Work co-funded by the project NORTE-01-0246-FEDER-000063, supported by Norte Portugal Regional Operational Programme (NORTE2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF).