Namibian Journal of Environment

Caves and their fauna in the highlands and escarpments of Angola and Namibia

D de Matos, J Zastrow, A Val, JM Mendelsohn — Fri, 15 Dec 2023 00:00:00 +0000

Several landscapes in the highlands and escarpments of Angola and Namibia (HEAN) have karstic regions with caves. Within the Northern Escarpment in Angola there are two main karstic regions. The first one includes the northern caves associated with a tropical climate and mostly concentrated in Ambuíla, Uíge Province. The second region comprises caves near the Atlantic coast, which are linked to underground flows of the Cambongo-Negunza River. An additional cluster of caves is on the Humpata Plateau and its edges within Angola’s Marginal Mountain Chain landscape. Most caves in Namibia are in the Karstveld and Khomas Hochland Plateau landscapes in karstic areas of relatively high rainfall. In this paper, we provide a brief overview of the history of cave exploration, sites and fauna documented in them. We report on the fauna recorded during surveys in 2010 and 2018–2021 in the southern karst around Humpata, Huíla Province; and summarise information available on fauna from Namibia. Most species recorded in Angolan caves are trogloxene taxa observed or collected in cave sediments. Namibian caves house a diversity of invertebrates, many of which are endemic or likely to be endemic to Namibia and the HEAN. Two endemic fish in underground lakes in Namibia are critically endangered. This study emphasises the need for further field research and for strategies to conserve caves and their faunas in both countries.

Mammal endemism in the highlands and escarpments of Angola and Namibia

AF Palmeirim, A Monadjem, P Vaz Pinto, P Taylor, MS Svensson, P Beja — Fri, 15 Dec 2023 00:00:00 +0000

The highlands and escarpments of Angola and Namibia (HEAN) consist of a series of high-elevation plateaus, escarpment ridges and inselbergs. They are known for their increased capacity to promote speciation and species persistence, but the importance of this area as an endemism centre for mammals remains poorly documented. Here we describe the endemic and near-endemic mammalian taxa occurring in the HEAN. Based on a literature search, we were able to confirm 12 endemic, 13 possible endemic and 20 near-endemic mammalian taxa, of which 28 are species, 10 are possible undescribed (new) species, and 7 are subspecies. Rodents showed the highest endemism (28 taxa), followed by bats (6 taxa), with only a few other mammalian orders being represented by endemic species here: two carnivores, two bovids, one odd-toed ungulate, two shrews, one sengi, two primates and one hyrax. Most of these endemic mammals have their distribution concentrated in the Angolan section of the HEAN. However, there are considerable knowledge gaps due to the lack of mammal surveys in large parts of the region, in addition to a lack of taxonomic studies utilising modern techniques. As such, new species of bats, rodents and shrews are expected to be documented in the years ahead. Given the alarmingly rapid loss of native habitats in the region, and to avoid losing the unique biological heritage of the HEAN, we recommend the enforcement of regulations protecting native habitat relicts.

Fishes of the highlands and escarpments of Angola and Namibia

PH Skelton — Fri, 15 Dec 2023 00:00:00 +0000

The fishes of the highlands and escarpments of Angola and Namibia (HEAN) are described broadly and a brief biogeographical explanation sketched. The fishes of this region are poorly documented in the literature and few records are available. Species of the families Kneriidae, Mormyridae, Cyprinidae, Danionidae, Amphiliidae, Clariidae, Mochokidae, Cichlidae and Mastacembelidae are highlighted and noted. An extraordinary radiation of Labeobarbus in the Cuanza River is a distinct feature. Two river systems in western Angola and Namibia, the Cuanza and the Cunene, extend from the interior down the escarpment to the coast and their fish faunas are considerably enriched. Affinities of the various taxa are pointed out including signature links with the southern Congo River basin, and East Africa. West African connections via the coast or the Congo Basin are sparse. West Zambezian faunal links are strongest but generally restricted to elements that favour rocky environments. The fishes of typical Kalahari sand systems, such as floodplains and swamps, are absent. Isolated and fragmented distributions of certain elements attest to relict situations indicative of early, more favourable, widespread distributions.

Flat gecko (Afroedura) diversity, endemism and speciation in the highlands and escarpments of Angola and Namibia

W Conradie, J Lobón-Rovira, FS Becker, A Schmitz, P Vaz Pinto — Fri, 15 Dec 2023 00:00:00 +0000

Nine species of African flat geckos (Afroedura) are known to be associated with the highlands and escarpments of Angola and Namibia (HEAN). Among these, the Afroedura bogerti group is the most speciose (with seven species) and endemic to the HEAN. Phylogenetically, it constitutes a young species group that speciated during the early Pleistocene (∼1.91 mya). Although currently none of these species is regarded as threatened, their distribution falls largely outside protected areas which could compromise their future.

Highland reptiles of Angola and Namibia

AM Bauer, LMP Ceríaco, MP Marques, FS Becker — Sat, 16 Dec 2023 00:00:00 +0000

Approximately 238 species of reptiles are found in the highlands and escarpments of Angola and Namibia (HEAN). Of the 430 species present in the two countries in total, 46 are strictly endemic (or nearly so) to the HEAN and another 16 have extensive portions of their ranges in these areas. Geckos constitute the majority of HEAN endemics with 32 species; in addition, there are nine cordylids, six skinks, four lacertids and one chamaeleon, as well as nine snakes (in five families) and a single tortoise comprising the remainder. Many of these species are substrate specialists and therefore rock types and textures may be a more important determinant of their distributions than elevation per se. Reptile diversity is greatest in the larger highland areas of the Khomas Hochland and Angolan Planalto, but many areas support at least some regional highland endemics including the Marginal Mountain Chain and Central Escarpment, and the Serra do Môco and the Serra da Neve in Angola, and the Karasberge, Waterberg and the Otavi, Erongo, Numib, Tiras, Baynes and Otjihipa mountains as well as numerous inselberg clusters (e.g., Huns–Orange and Huab outliers) in Namibia. The vast majority of the highland taxa have been assessed as Least Concern by the International Union for Conservation of Nature (IUCN), with several taxa considered Data Deficient or Near Threatened and only three Vulnerable. Most highland and escarpment areas in Angola and Namibia remain woefully understudied from a herpetological perspective and the description of 20% of the endemics in the last ten years suggests that true reptile diversity remains underestimated.

The amphibians of the highlands and escarpments of Angola and Namibia

FS Becker, NL Baptista, P Vaz Pinto, R Ernst, W Conradie — Sat, 16 Dec 2023 00:00:00 +0000

The amphibians of the highlands and escarpments of Angola and Namibia are a diverse group containing fifteen highland endemic or associated species. Both species richness and endemism are highest in the central and northern highlands of Angola, corresponding with higher rainfall. The Angolan highlands contain seven highland endemics, while the arid Namibian highlands contain only one. Few baseline data are available for much of the highlands, leading to an inadequate understanding of species occurrence patterns, population trends and conservation status. Recent surveys and phylogenetic revisions have led to the discovery of several previously undescribed species, and new species descriptions are still in progress. Both the species richness and endemism reported here are probably underestimates.

The highlands and escarpment of Angola as an endemism hotspot for African dragonflies and damselflies (Insecta: Odonata)

J Kipping, V Clausnitzer, K-DB Dijkstra — Sat, 16 Dec 2023 00:00:00 +0000

The plateaus and escarpments of Angola are a major centre of Odonata endemism in Africa, rivalling and possibly surpassing the highlands of Ethiopia and South Africa. We discuss 34 likely endemic species and 8 near-endemics found in Angola’s highland area. Remarkably, 20 of these endemics and near-endemics do not occur either along the western escarpment or on the high central plateau, but on the lower sandy plateaus farther east. Despite the western scarp having traditionally received much scientific attention, the first odonatological discoveries were made there only recently. Of the 42 species of interest discussed here, the taxonomy of 21 of them has yet to be fully resolved. Furthermore, many regions, particularly in northeastern Angola, are still to be explored.

Endemism of Arachnida (Amblypygi, Scorpiones and Solifugae) in the highlands and escarpments of Angola and Namibia: current knowledge and future directions

L Prendini, TL Bird — Sat, 16 Dec 2023 00:00:00 +0000

The arachnid fauna of Angola and Namibia is diverse and includes high levels of endemism, much of which is associated with the arid zone, especially the Namib Desert. The endemic arachnid fauna of the highlands and escarpments, including mountain ranges, plateaus and inselbergs, has received less attention. The study presented here is the first to compile existing distributional data for three arachnid orders – whip spiders (Amblypygi Thorell, 1883), scorpions (Scorpiones C.L. Koch, 1837) and solifuges (Solifugae Sundevall, 1833) – occurring in the highlands and escarpments of Angola and Namibia from published literature, online databases and natural history collections. Distribution maps were used, together with available data or expert knowledge of taxon habitat requirements, to prepare a list of described arachnid taxa considered endemic or near-endemic to the western highlands and escarpments of these two countries. In addition, arachnid endemism was assessed more broadly by scoring the presence of described and potential undescribed endemics in relevant highlands and escarpments, tallying the scores for each order, and ranking the highlands and escarpments based on the sum of all three ordinal tallies. These scores provide a rough index of the relative importance of highlands and escarpments in Angola and Namibia for prioritising decisions regarding conservation as well as further survey and inventory from the arachnid perspective. Although the highlands and escarpments of Angola and Namibia probably serve as refugia for taxa requiring cooler, more humid habitats than are available in the surrounding arid lowlands, including palaeoendemics, they appear to contain fewer endemic arachnid taxa than the lowlands. This may be because: (1) the highlands and escarpments of Angola and Namibia are relatively low, on average, providing few opportunities for insular speciation; (2) much arachnid endemism in the arid lowlands is associated with unique substrates that are absent in the highlands, including sand dunes, gravel plains and clays associated with drainage systems, all of which facilitate burrowing to escape the arid conditions and promote diversification; and (3) much of the taxonomy of the arachnids of both countries remains unresolved, and the distributions poorly understood, especially in Angola. More intensive surveys, with an emphasis on collecting genetic samples from disjunct populations across the distributions of each putative species, are needed to better understand arachnid diversity and endemism in the region.

The endemic butterflies of Angola and Namibia and their evolutionary implications

AJ Gardiner, MC Williams† — Sat, 16 Dec 2023 00:00:00 +0000

The currently described endemic butterfly species and subspecies to Angola and Namibia are presented together with their known distributions. This butterfly fauna has been placed into the biogeographic units of Carcasson (1964) and Burgess et al. (2004). Aspects of the evolution and biogeography of the fauna, such as their association with other mountainous areas of Africa and their linkage to dry areas of East Africa, are discussed. The information suggests large gaps in our knowledge of the Angolan highland fauna. The importance of utilising such fauna for identifying conservation priorities in these two countries is highlighted.

The Neuroptera of the highlands and escarpments of Angola and Namibia

MW Mansell — Sat, 16 Dec 2023 00:00:00 +0000

Of the 17 families of Neuroptera (lacewings) worldwide, ten families represented by 148 species have been recorded from Namibia, and five families with 36 species from Angola. In Namibia, 17 endemic species are known, of which two are known from high-elevation escarpment localities. However, very few surveys dedicated specifically to Neuroptera have been carried out in Namibia and none in Angola, so it is therefore not possible to assess the importance of the highlands and escarpments to Neuroptera. Recommendations are made for further surveys and research.