Bats of Southern and Central Africa. Ara Monadjem
Examples include the association of Rhinolophus sakejiensis with relictual Guineo-Congolian forest, and Plerotes anchietae with moist miombo woodlands of the Zambesian phytochorion.
The fynbos biome, also known as the Cape Floristic Region, is situated at the southern tip of Africa. Centred on the Cape Fold Belt mountains, with its origins in the late Oligocene, this biome is recognised as one of the main centres of plant diversity and endemism in Africa (van Wyk and Smith 2001, Hoffmann et al. 2015). While this biome supports a remarkably high endemism of plants and some animals, its bat fauna is distinctly depauperate, and only one species, Rhinolophus capensis, can be considered a partial endemic to this region.
To the west of the subcontinent, arid and semi-arid biotas characterise the Namib Desert, succulent Karoo and the Nama Karoo (often referred to as semi-arid scrub vegetation). The southern African arid region hosts at least 17 bat species, representing eight families, of which three are endemic to the region (Rhinolophus denti, Laephotis namibensis and Cistugo seabrae) and one is vagrant (the fruit bat Eidolon helvum) (Monadjem et al. 2018a). Local-scale landscape features (e.g. habitat structure) might be more important than aridity in driving bat species richness, and an unknown factor (possibly temperature limiting the availability of insects flying high above the ground) may restrict the diversity of the open-air foragers throughout the region (Monadjem et al. 2018a).
Grassland
The high-lying central plateau (‘Highveld’) of South Africa and the Drakensberg mountains are dominated by grasslands and (in the Drakensberg and its foothills) small patches of Afromontane forest. Montane grassland–forest mosaics also characterise the Eastern Highlands of Zimbabwe and the central Angolan Highlands. Grasslands also constitute the most widespread vegetation unit mapped across south-central Africa, where they represent a ‘wetland archipelago’ of seasonally inundated floodplains: its islands extend from the Okavango Swamps in Botswana, to lakes Bangweulu and Mweru in Zambia, and the Kamalondo Depression in the Katanga Province of the DRC. These valley grasslands are widespread in the catchments of the Chambeshi, Cubango, Upper Kafue, Kasai, Upper Lualaba, Upper Kunene and Upper Zambezi rivers across the Kalahari Plateau (White 1983).
Figure 34. (a) Interior of dense gallery forest that includes Guinean–Congolian plant species, at the source of the Zambezi River, Ikelenge Pedicle, Mwinilunga District, northwestern Zambia; (b) dense riparian forest (East African Coastal Mosaic) with emergent palms, Zambezi Delta, Mozambique.
Savanna
The savanna biome is characterised by widely spaced trees that form an open canopy, allowing sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of grasses. This biome originated in the early Neogene (de la Estrella et al. 2017) and expanded in the Late Miocene (∼7 Ma) (Bouchenak-Khelladi and Hodkinson 2011). Much of the southern African region is covered by such savanna woodlands, which support the greatest species richness of bats (Gelderblom et al. 1995, Schoeman et al. 2013). Second only to rodents, bats are also one of the most species-rich groups of mammals occurring in the southern savanna biome (Grubb 1999).
Miombo woodlands – the world’s most extensive dry forests – cover a large portion of southern Africa north and east of the 600 m annual rainfall isohyet.
Miombo occurs from Angola in the west across Katanga (DRC), Zambia and Malawi to Tanzania, most of Mozambique, and much of Zimbabwe (Frost 1996). The southern limit of miombo just reaches South Africa near the Luvuvhu River and on the Soutpansberg massif. Bat species encountered in mesic miombo include the molossid Mops niveiventer and the vespers Mimetillus thomasi and Scotoecus hindei/albigula. The southernmost limits of many Congo basin vertebrate species are associated with gallery forests that penetrate mesic miombo woodlands (Cotterill 2002a, b). These include the fruit bats Myonycteris angolensis and M. torquata.
There are also extensive miombo woodlands on deep Kalahari sands in the western regions of Zambia, eastern Angola and the southern DRC. Although much of the southern portion of this belt receives rainfall characteristic of semi-arid savannas, these tall woodlands depend on groundwater in deep Kalahari sediments. This edaphic control on the vegetation is exemplified in the Cryptosepalum evergreen forests (Mavunda) on Kalahari sediments in western Zambia and eastern Angola (White 1983), and equally in the hardwood Zambezi teak forests dominated by Baikiaea plurijuga, with their distribution centred on the Four Corners Region (Huckaby 1986, Frost 1996).
Mopane woodlands, dominated by the emergent Colophospermum mopane, are associated with particular soil formations, largely on alluvium at lower altitudes throughout the middle and lowveld of Zimbabwe, and also in large parts of southern Zambia, central and southern Mozambique, northern South Africa, northern and eastern Botswana, as well as northern Namibia and southwestern Angola (Cole 1986). Mopane woodlands are of singular significance to bat biogeography, because the hollows in mature trees, the aptly named cathedral mopane, offer plentiful roosting sites for bats. Woodland degradation, whether by elephants or humans (e.g. wholesale clearing for cotton plantations in northwestern Zimbabwe), destroys the larger trees and has highly negative effects on the abundance and species richness of bat assemblages (Fenton et al. 1998a, McCleery et al. 2018) (Figure 32).
Thorny acacia (genera Vachellia and Senegalia) savannas dominate large parts of southern Zimbabwe, northern South Africa, Botswana and Namibia, extending into the Kalahari. Cavities in these large trees, and cavities under bark, support tree-roosting bats.
The community structure of savanna bat assemblages arises from abiotic and biotic processes operating at local and regional scales (Schoeman and Monadjem 2018). At a regional scale, speciation mediated by historic geomorphic and climatic events has shaped the bat diversity of the regional species pool. The high taxonomic and phylogenetic bat diversity in the savanna biome is maintained by the stable wet and warm climate and high habitat heterogeneity. Processes at the mesoscale probably play a minor role because the high mobility of bats enables them to select habitat patches even in human-dominated urban and agricultural landscapes. Multiple biotic processes, including competition and prey defences, operate at a local scale, but non-random patterns are not ubiquitous within and across ecomorphological variables (Schoeman and Jacobs 2008, 2011).
Forest
The northernmost reaches of the region covered in this book interface, in complex, historically derived patterns, with the southern margin of the main belt of moist tropical forests, which extend from the Congo basin into West Africa. This transition zone comprises a forest–savanna mosaic, whose southern limits are represented by the gallery forests that fringe drainage lines in northern Angola, Katanga and northern Zambia (Figures 27, 28, 34). Locally termed mushitu in Zambia or mihulu in Katanga, these gallery forests constitute important habitats for forest-adapted species, including bats. Alongside several species of fruit bats, at least one endemic bat, Rhinolophus sakejiensis, occurs here (Cotterill 2002a, b, 2005, 2006).
Coastal forest mosaic associations extend along the eastern seaboard from Tanzania into the Eastern Cape and KwaZulu-Natal in South Africa.
High-altitude Afromontane forest occurs as ‘islands’ in the Eastern Cape and Drakensberg mountains, the Chimanimani-Nyanga in Zimbabwe, and Gorongosa in Mozambique, and the highlands of Malawi. Relatively few endemic mammals are associated with these forests in southern Africa: a recently described crocidurine shrew (Taylor et al. 2013d) and a golden mole (Carpitalpa arendsi)