On the origin of southern African subtropical thicket vegetation

Cowling, Richard M.; Procheş, Şerban; Vlok, Jan; Staden, J. Van

doi:10.1016/s0254-6299(15)30144-7

Cited by 105 publications

(131 citation statements)

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“…However, this argument is contradicted by the presence in Africa of thicket from the early Eocene (29). Thicket is a low, dense woody vegetation with intermediate light level between forests and savannas that supports a high diversity of spiny trees (29). The early appearance of thicket and the much later appearance of spiny plants in our analysis, thus, suggest that the evolution of spinescence is linked to the arrival of bovids in Africa during the Neogene.…”

Section: Discussionmentioning

confidence: 70%

“…The rarity of spines in modern forests could imply that a more forested environment in the Paleogene may have inhibited spine development. However, this argument is contradicted by the presence in Africa of thicket from the early Eocene (29). Thicket is a low, dense woody vegetation with intermediate light level between forests and savannas that supports a high diversity of spiny trees (29).…”

Section: Discussionmentioning

confidence: 99%

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Spiny plants, mammal browsers, and the origin of African savannas

Charles‐Dominique

Davies

Hempson

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

149

154

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Savannas first began to spread across Africa during the Miocene. A major hypothesis for explaining this vegetation change is the increase in C 4 grasses, promoting fire. We investigated whether mammals could also have contributed to savanna expansion by using spinescence as a marker of mammal herbivory. Looking at the present distribution of 1,852 tree species, we established that spinescence is mainly associated with two functional types of mammals: large browsers and medium-sized mixed feeders. Using a dated phylogeny for the same tree species, we found that spinescence evolved at least 55 times. The diversification of spiny plants occurred long after the evolution of Afrotherian proboscideans and hyracoids. However, it is remarkably congruent with diversification of bovids, the lineage including the antelope that predominantly browse these plants today. Our findings suggest that herbivore-adapted savannas evolved several million years before fire-maintained savannas and probably, in different environmental conditions. Spiny savannas with abundant mammal herbivores occur in drier climates and on nutrient-rich soils, whereas fire-maintained savannas occur in wetter climates on nutrient-poor soils.Africa | Bovidae | coevolution | mammalian herbivory | savanna T he origin and spread of savannas have been topics of intensive research, but many questions remain. The C 4 grasses that dominate savannas emerged in the late Oligocene (∼30 Ma), but savannas only began to emerge as one of the world's major biomes in the late Miocene more than 20 My later (1). What changed to roll back the forests, allowing the rapid spread of grasslands? Ehleringer et al. (2) first linked the rise of savannas to a drop in atmospheric CO 2 , which would favor C 4 grasses over their C 3 grass predecessors. Low CO 2 can also reduce woody cover by increasing the risk of recruitment failure in woody plants whether from drought, fire, or browsing (3). However, the timing of the onset of low CO 2 is much earlier than the spread of savannas; therefore, although low CO 2 may have contributed to savanna expansion, it cannot explain the long time lag between C 4 origins and savanna spread. Climate change is the usual explanation for changing vegetation over time. Increased aridity in the late Miocene has been shown to cause the retreat of forests in North America and Eurasia, allowing grasslands to spread in their place (4, 5). However, large areas of extant savannas occur in climates that are wet enough to support forests and other closed woody types (6-8). Fires are frequent in high-rainfall savannas and have been considered the major agents accounting for open ecosystems in climates that can support forests. Fossil charcoal, mostly from marine cores, shows a surge in fire activity from the late Miocene correlated with the spread of savannas (9, 10). Phylogenetic studies have shown the emergence of fire-adapted woody plants from the late Miocene through to the Pleistocene in both Brazil and Africa, consistent with fossil evidence for increasing f...

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Section: Discussionmentioning

confidence: 70%

Section: Discussionmentioning

confidence: 99%

Spiny plants, mammal browsers, and the origin of African savannas

Charles‐Dominique

Davies

Hempson

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

149

154

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“…The reserve lies within the thicket biome of the Eastern Cape Province (Cowling et al 2005) and is considered to be a good habitat for the black rhinoceros (Lent and Fike 2003), as evidenced by the rapid increase of the population (Heilmann et al 2006). The fieldwork was, for logistical reasons, concentrated on the western side of the Great Fish River, the area with the highest rhino density.…”

Section: Study Areamentioning

confidence: 99%

A comparison of faecal analysis with backtracking to determine the diet composition and species preference of the black rhinoceros (Diceros bicornis minor)

et al. 2009

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The diet of black rhinoceros (Diceros bicornis minor) was studied using backtracking and faecal analysis in South Africa. Both methods yielded different results, with a large bias for dominant species. Results of backtracking showed that the rhinos browsed on 80 plant species. Grasses comprised 4.5% of the diet in the faecal analysis, but were not recorded during the backtracking. The backtracking method, along with a measure of forage availability, was used to identify two groups of plant species, those species taken in a higher proportion than available in the field and those taken in a lower proportion. Chemical analyses showed that these two species groups were similar in in vitro digestibility, macro-elements and fibre constituents. Mean bite size and species contribution to the diet were not correlated with any of the forage quality parameters, indicating that rhinos were not maximising nutrient intake or minimising fibre intake of these consumed plant species.

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“…Madagascar rather than tropical Africa Cretaceous sites (Bamford, 2004 (Richardson andCowling, 1992, Manders, 1990), the Proto-Fynbos probably occurred in a 155 mosaic with subtropical forest and thicket and not, as proposed by Scholtz (1985), as a forest 156 understorey (Cowling et al, 2005). Probable Palaeocene deposits at Koingnaas (Namaqualand) 157 contain Araucariaceae and Podocarpaceae pollen (De Villiers and Cadman, 2001).…”

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confidence: 95%