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Evolutionary Diversity Patterns in the Cape Flora of South Africa: Applications and Challenges in Biodiversity Science

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Evolutionary Diversity Patterns in the Cape Flora of South Africa: Applications and Challenges in Biodiversity Science

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Abstract

The Greater Cape Floristic Region of South Africa is a relatively small area found in the south-western corner of the African continent. It is characterised by a Mediterranean-type climate and harbours an incredible floral diversity with almost 11,500 species of plants, of which more than three-quarters are found nowhere else in the world. The floristic composition of the region is very distinctive with families not dominant in other floras, such as Iridaceae, Aizoaceae, Ericaceae, Proteaceae and Restionaceae. In addition, small-leaved, sclerophyllous low shrubs and geophytes are by far the predominant growth forms with a low proportion of tree and annual species present. Understandably, this flora has attracted a lot of interest, and many have pondered what environmental and ecological factors could be responsible for its richness and uniqueness and the resulting biodiversity patterns observed today. In this chapter, the current state of knowledge of large-scale evolutionary patterns, investigated using phylogenetic diversity metrics, within the Cape region are reviewed. As well as published works, we report on ongoing studies examining biodiversity patterns using phylogenetic diversity, phylogenetic endemism and phylobetadiversity, both in plants and animals. We also review how these phylogeny-based approaches have been used to address applied questions (e.g. biodiversity surrogates, phytogeographical delimitations).

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... Here, we present a unified flora of these coastal calcareous habitats of the CFR and analyse the flora to assess its size, taxonomic composition, growth-form mix, biological traits, biogeographic affinities and endemism. We further sketch a brief scenario of the flora's assembly, with a focus on the Pleistocene-a period whose dynamic sea levels and vacillating climate had a profound impact on the geography and diversification of floras in the Cape (Cowling et al., 2017;Forest, Colville & Cowling, 2018;Colville et al., 2020), especially along the coast (Grobler et al., 2020). ...
... 19-20,000 km 2 , increased the available habitat for limestone fynbos at least eight-fold . By invoking age-and-area theory, which explains much of the diversity patterns observed in the CFR (Cowling et al., 2017;Forest, Colville & Cowling, 2018;Colville et al., 2020), we argue that these expansive areas of calcareous habitat, exposed at length during Pleistocene glacials (Jouzel et al., 2002;Waelbroeck et al., 2002;Fisher et al., 2010), enabled the evolution of a rich coastal flora in the Cape (Grobler et al., 2020). Age-and-area theory posits that high levels of biodiversity amass in habitats characterized by sufficiently large areas to support viable biotic populations and by high environmental stability over evolutionary timescales, synergistically resulting in reduced extinction rates and increased speciation rates, and ultimately leading to the accumulation of species from both ancient lineages and more recent radiations (Dynesius & Jansson, 2000;Jansson & Dynesius, 2002;Ricklefs, 2006;Fine, 2015;Schluter, 2016). ...
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The Cape Floristic Region (CFR) is globally recognized as a hotspot of plant diversity and endemism. Much of this diversity stems from radiations associated with infertile acid sands derived from sandstones of the geologically ancient Cape Fold Belt. These ancient montane floras acted as the source for most subsequent radiations on the Cape lowlands during the Oligocene (on silcretes) and Mio-Pliocene (on shales). The geomorphic evolution of the CFR during the Plio-Pleistocene led to the first large-scale occurrence of calcareous substrata (coastal dunes and calcarenites) along the Cape coast, providing novel habitats for plant colonization and ensuing evolution of the Cape coastal flora-the most recent diversification event in the Cape. Few studies have investigated the CFR's dune and calcarenite floras, and fewer still have done so in an evolutionary context. Here, we present a unified flora of these coastal calcareous habitats of the CFR and analyze the taxonomic, biological and geographical traits of its component species to gain insights into its assembly. The Cape coastal flora, comprising 1,365 species, is taxonomically dominated by the Asteraceae, Fabaceae and Iridaceae, with Erica, Aspalathus and Agathosma being the most speciose genera. In terms of growth-form mix, there is a roughly equal split between herbaceous and woody species, the former dominated by geophytes and forbs, the latter by dwarf and low shrubs. Species associated with the Fynbos biome constitute the bulk of the flora, while the Subtropical Thicket and Wetland biomes also house a substantial number of species. The Cape coastal flora is a distinctly southern African assemblage, with 61% of species belonging to southern African lineages (including 35% of species with Cape affinity) and 59% being endemic to the CFR. Unique among floras from the Cape and coastal Mediterranean-climate regions is the relatively high proportion of species associated with tropical lineages, several of which are restricted to calcareous substrata of the CFR. The endemic, calcicolous component of the flora, constituting 40% of species, represents 6% of the Cape's regional plant diversity-high tallies compared to other biodiversity hotspots. Most coastal-flora endemics emerged during the Plio-Pleistocene as a product of ecological speciation upon the colonization of calcareous substrata, with the calcifugous fynbos floras of montane acid substrata being the most significant source of this diversification, especially on the typically shallow soils of calcarenite landscapes. On the other hand, renosterveld floras, associated with edaphically benign soils that are widespread on the CFR lowlands, have not been a major source of lineages to the coastal flora. Our findings suggest that, over and above the strong pH gradient that exists on calcareous substrata, soil depth and texture may act as important edaphic filters to incorporating lineages from floras on juxtaposed substrata in the CFR.
... Specifically, southwestern CFR biome stability created higher species diversity originating in the Pleistocene, with recent environmental instability explaining lower diversity in the eastern CFR (Cowling et al., , 2017Forest et al., 2018;Goldblatt, 1997;Manne et al., 2007;Proçhes et al., 2006). Other than studies of species richness, this latter hypothesis has seen support from fossil analyses (Cowling et al., 1999;Rector & Verrelli, 2010;Sauquet et al., 2009) and phylogenetics (Linder & Hardy, 2004;Pirie et al., 2016;Richardson et al., 2001;Valente et al., 2010). ...
... In fact, geographic distance explains a significant, yet small, overall proportion of population genetic structure on broad-scales (9% of cpDNA, and 15% of nuDNA diversity, Table S5). As previously noted (e.g., Cowling et al., 2017;Forest et al., 2018), and predicted here, phylogeographic evolutionary analyses show lineages from the southwestern CFR exhibit higher genetic structure and older estimated ages than lineages found across the most distantly geographically separated locales in the CFR. That is, a simple isolation-by-distance model cannot explain patterns of genetic divergence observed here for either marker type. ...
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As human‐induced change eliminates natural habitats, it impacts genetic diversity and population connectivity for local biodiversity. The South African Cape Floristic Region (CFR) is the most diverse extratropical area for plant biodiversity, and much of its habitat is protected as a UNESCO World Heritage site. There has long been great interest in explaining the underlying factors driving this unique diversity, especially as much of the CFR is endangered by urbanization and other anthropogenic activity. Here, we use a population and landscape genetic analysis of SNP data from the CFR endemic plant Leucadendron salignum or “common sunshine conebush” as a model to address the evolutionary and environmental factors shaping the vast CFR diversity. We found that high population structure, along with relatively deeper and older genealogies, are characteristic of the southwestern CFR, whereas, low population structure and more recent lineage coalescence depicts the eastern CFR. Population network analyses show genetic connectivity is facilitated in areas of lower elevation and higher seasonal precipitation. These population genetic signatures corroborate CFR species‐level patterns consistent with high Pleistocene biome stability and landscape heterogeneity in the southwest, but with coincident instability in the east. Finally, we also find evidence of human land‐usage as a significant gene flow barrier, especially in severely‐threatened lowlands where genetic connectivity has been historically the highest. These results help identify areas where conservation plans can prioritize protecting high genetic diversity threatened by contemporary human activities within this unique cultural UNESCO site.
... Deducing from the Pleistocene disturbance hypothesis, we further predict that CFR dunes would not show the westeeast decline of plant diversity described above. This gradient mirrors a Cenozoic-wide diversification gradient, with more stable environments in the west resulting in lower extinction rates and an accumulation of endemic clades, while in the less stable east, higher rates of extinction reduce phylogenetic and species diversity Forest et al., 2018). We posit that constraints on immigration and persistence of plant species in the edaphically unique and dynamic dune environment would override the evolutionary diversity patterns evident elsewhere in the CFR. ...
... Consequently, Holocene dune floras of the CFR should not reflect the westeeast diversity macro-gradient evident in interior habitats of the region, where the west supports double the number of species than equal-sized areas of the east Cowling and Lombard, 2002). This longitudinal decline in diversity reflects a gradient of environmental stability dating back to the Neogene (Cowling et al., 2009(Cowling et al., , 2015Huntley et al., 2016), with the more stable west experiencing lower extinction rates and an accumulation of endemic clades, while in the east, more dynamic environments resulted in higher extinction rates, thereby reducing species diversity Forest et al., 2018). Our results are consistent with this prediction of the Pleistocene disturbance hypothesis: interior lowland floras in the CFR exhibit a decline in diversity along a westeeast gradient (cf. ...
Article
Coastal dune landscapes are subject to harsh environmental conditions and, owing to Pleistocene sea-level fluctuations, comprise small, fragmented features. These environments present several challenges for plant colonization and persistence, and dune floras are therefore likely to be species-poor but endemic-rich. Here, we explore an explicitly historical hypothesis — the Pleistocene disturbance hypothesis — to explain patterns of plant diversity on Holocene dunes of the Cape Floristic Region (CFR). This hypothesis predicts that: (1) dunes would not show the west–east decline in diversity evident in inland habitats as the unique selective regime of the dune environment would override the evolutionary diversity patterns evident elsewhere in the CFR; (2) dune diversity would be lower than in adjacent, inland habitats that were not exposed to extreme disturbance regimes during the Pleistocene. We tested this by compiling regional-scale plant species diversity data from dune and interior lowland habitats of the southwestern and southeastern CFR and subjecting the data to species–area analysis. Our results were consistent with the Pleistocene disturbance hypothesis: diversity patterns of dunes did not differ between the southwestern and southeastern subregions, and interior sites were richer in species than dune sites. However, the difference in diversity between interior and dune sites (1.42×) was remarkably marginal. We propose that this is a consequence of the CFR's glacial physiography, where a large expanse of dune habitat was exposed at length along the Palaeo-Agulhas Plain during Pleistocene sea-level lowstands. This vast habitat area would have facilitated the development of a species-rich dune flora.
... Support for this hypothesis comes from both MCs and TCs evaluated in our study. Thus, patterns of plant diversity among MC regions are well predicted by biome stability (Cowling et al. 2015, Rundel et al. 2016, as are patterns within the hyperdiverse Cape MC (Cowling et al. 2017, Forest et al. 2018, Colville et al. 2020, Mazijk et al. 2021. Biome stability might have likely also played an important role in establishing the relatively species-poor Afrotropics as the "odd man out" (Richards 1973) among TCs. ...
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Mediterranean- and tropical-climate regions harbour the richest regional-scale floras globally. Until recently, however, comparisons of their diversities have been hindered by a lack of comprehensive inventories of tropical floras. Using taxonomically verified floras, we analyse area-adjusted plant diversities of five Mediterranean- and 35 tropical-climate regions to determine which are the most species-rich regions on Earth. On average, the Neotropics and tropical Southeast Asia support the most diverse floras globally. However, the area-adjusted diversities of the richest floras in these tropical regions are matched by those of two Mediterranean-climate floras, namely the Cape (second richest) and Mediterranean Basin (sixth richest). Except for Madagascar and Burundi, the Afrotropical regions were substantially less diverse than other tropical floras and half of the Afrotropical floras were poorer than the least diverse Mediterranean-climate region, namely Central Chile. We evaluate the likely ecological and evolutionary drivers of these plant diversity patterns in terms of three hypotheses that are apposite for global scale comparisons, namely water-energy dynamics, biome stability, and ecological heterogeneity. Water-energy dynamics appear to have little influence in explaining these diversity patterns: nodes of high global plant diversity are associated with climates that support year-round plant production (tropical climates) and those where the growing season is constrained by a winter rainfall regime (Mediterranean-type climates). Moreover, while the Afrotropics have higher primary production than the Neotropics and Southeast Asian tropics, they have markedly lower plant diversity. Instead, these patterns appear to be consistent with the hypothesis that the synergy of historical biome stability (reducing extinction rates) and high ecological heterogeneity (promoting speciation rates) better explain global patterns of regional-scale plant diversity.
... For a clear view of the isolate groupings with reference type strains, separate phylogenies of Rhizobium and Mesorhizobium were constructed (Figs. 3,4,5,6). Due to incompatibility of the primer pairs some isolates did not constantly appear in all phylogenies. ...
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Polhillia , Wiborgia and Wiborgiella species are shrub legumes endemic to the Cape fynbos of South Africa. They have the ability to fix atmospheric N 2 when in symbiosis with soil bacteria called ‘rhizobia’. The aim of this study was to assess the morpho-physiological and phylogenetic characteristics of rhizobia associated with the nodulation of Polhillia , Wiborgia and Wiborgiella species growing in the Cape fynbos. The bacterial isolates from root nodules consisted of a mixture of fast and intermediate growers that differed in colony shape and size. The isolates exhibited tolerance to salinity (0.5–3% NaCl) and pH (pH 5–10) and different antibiotic concentrations, and could produce 0.51 to 51.23 µg mL ⁻¹ of indole-3-acetic acid (IAA), as well as solubilize tri-calcium phosphate. The ERIC-PCR results showed high genomic diversity in the rhizobial population and grouped them into two major clusters. Phylogenetic analysis based on 16S rRNA, atpD , gln II, gyrB , nifH and nodC gene sequences revealed distinct and novel evolutionary lineages related to the genus Rhizobium and Mesorhizobium , with some of them being very close to Mesorhizobium australicum . However, the phylogenetic analysis of glnII and nifH genes of some isolates showed incongruency.
... Phylogenetic diversity in the CFR shows patterns similar to species richness, with a concentration of high values in the western part of the region. Our results confirm that overall, phylogenetic diversity is more evenly distributed in the phylogenetic tree, and generally on longer branches (i.e., overdispersed), in the eastern CFR (45,46). Our finding of a strong positive relationship of phylogenetic diversity with biome stability (Table 1) supports this pattern, which can be explained by the presence in the western part of the CFR of a high number of closely related taxa that accumulated over time in a relatively stable environment (45). ...
Article
Significance What explains global patterns of diversity—environmental history or ecology? Most studies have focused on latitudinal gradients—the decline of diversity from the tropics to the poles. A problem with this is that it conflates predictions of historical and ecological hypotheses: The productive tropics have also experienced high Cenozoic biome stability. Longitudinal diversity gradients can overcome this constraint. We use a longitudinal diversity gradient in the megadiverse Cape Floristic Region to model species and evolutionary diversity in terms of Pleistocene climate stability and ecological heterogeneity. We find that biome stability is the strongest predictor of diversity measures, and argue that stability, in conjunction with measures of ecological opportunity—other than productivity—may provide a general explanation for global diversity patterns.
... Moreover, soils of the biome mostly originated from ancient, weathered, sandstones and shales (Goldblatt and Manning 2002) and have low levels of nitrogen (N) and phosphorus (P) that range between 1 and 2 mg N.g −1 soil and 0.4 and 3.7 μg P.g −1 soil (Cocks and Stock 2001;. Nevertheless, this region contains a diversity of endemic plant species (Cowling and McDonald 1998;Forest et al. 2018). To compensate for the low nitrogen status of the soil, legume species in this region often form effective symbiosis with indigenous rhizobia (Kanu and Dakora 2012;Lemaire et al. 2015;Dludlu et al. 2017). ...
Article
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Species of the genera Polhillia, Wiborgia and Wiborgiella are endemic to the Cape fynbos, South Africa. These plants form root nodules with soil rhizobia that fix atmospheric nitrogen. Little is known about their N and P nutrition, as well as their water-use efficiency in this highly dry and nutrient-poor soil environment. Therefore, the aim of this study was to assess P nutrition and water-use efficiency in natural stands of Polhillia, Wiborgia and Wiborgiella species as well as their dependency on Biological N2 fixation for nutrition. The δ15N natural abundance technique was used to measure the symbiotic performance. The Acid and alkaline phosphatase activities were assayed using p-nitrophenol method. 16S rRNA sequence was used to identify microsymbionts nodulating the test plants. The δ15N study showed a high dependency of the tested species on N2 fixation. The N derived from fixation was 76–84% for Polhillia sps., 73–91% for Wiborgia sps., and 61–68% for Wiborgiella sessilifolia. The species differed in water-use efficiency, with δ13C values of −28.1 to −25.1‰ for Polhillia sps., −28.3 to −25.8 ‰ for Wiborgia sps., and − 27.7 to −27.1‰ for Wiborgiella sessilifolia. The rhizosphere acid and alkaline phosphatase activities were higher in P. brevicalyx and P. pollens, than in the other tested species and this resulted in greater available P in the rhizosphere soils and an increased P uptake and accumulation in the plant shoots. Based on 16S rRNA nucleotide sequence and phylogenetic analysis of root nodule isolates, a diverse and novel Mesorhizobium sps. nodulate the tested plant species in the fynbos ecosystem.
... Edwards, Wakeley, Beerli, & Slowinski, 2002). On the contrary, fast dispersal in protists would blur any such signature and taxonomic or phylogenetic diversity would tend to be distributed randomly and peak in areas with largest extent of favourable habitats (Forest, Colville, & Cowling, 2018). ...
Article
Recent studies show that soil eukaryotic diversity is immense and dominated by microorganisms. However, it is unclear to what extent the processes that shape the distribution of diversity in plants and animals also apply to microorganisms. Major diversification events in multicellular organisms have often been attributed to long‐term climatic and geological processes, but the impact of such processes on protist diversity has received much less attention as their distribution has often been believed to be largely cosmopolitan. Here, we quantified phylogeographic patterns in Hyalosphenia papilio, a large testate amoeba restricted to Holarctic Sphagnum‐dominated peatlands, to test if the current distribution of its genetic diversity can be explained by historical factors or by the current distribution of suitable habitat. Phylogenetic diversity was higher in Western North America, corresponding to the inferred geographical origin of the H. papilio complex, and was lower in Eurasia despite extensive suitable habitat. These results suggest that patterns of phylogenetic diversity and distribution can be explained by the history of Holarctic Sphagnum peatland range expansions and contractions in response to Quaternary glaciations that promoted cladogenetic range evolution, rather than the contemporary distribution of suitable habitats. Species distributions were positively correlated with climatic niche breadth, suggesting that climatic tolerance is key to dispersal ability in H. papilio. This implies that, at least for large and specialized terrestrial microorganisms, propagule dispersal is slow enough that historical processes may contribute to their diversification and phylogeographic patterns and may partly explain their very high overall diversity. This article is protected by copyright. All rights reserved.
... It is interesting to compare patterns of diversity in fynbos clades between the western Cape with a classic MTC regime and the eastern Cape with aseasonal rainfall. Species diversification in fynbos clades has been much higher in the former (Forest et al., 2018). ...
Article
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Despite decades of broad interest in global patterns of biodiversity, little attention has been given to understanding the remarkable levels of plant diversity present in the world’s five Mediterranean-type climate (MTC) regions, all of which are considered to be biodiversity hotspots. Comprising the Mediterranean Basin, California, central Chile, the Cape Region of South Africa, and southwestern Australia, these regions share the unusual climatic regime of mild wet winters and warm dry summers. Despite their small extent, covering only about 2.2% of world land area, these regions are home to approximately one-sixth of the world vascular plant flora. The onset of MTCs in the middle Miocene brought summer drought, a novel climatic condition, but also a regime of recurrent fire. Fire has been a significant agent of selection in assembling the modern floras of four of the five MTC regions, with central Chile an exception following the uplift of the Andes in the middle Miocene. Selection for persistence in a fire-prone environment as a key causal factor for species diversification in MTC regions has been under-appreciated or ignored. Mechanisms for fire-driven speciation are diverse and may include both directional (novel traits) and stabilizing selection (retained traits) for appropriate morphological and life-history traits. Both museum and nursery hypotheses have important relevance in explaining the extant species richness of the MTC floras, with fire as a strong stimulant for diversification in a manner distinct from other temperate floras. Spatial and temporal niche separation across topographic, climatic and edaphic gradients has occurred in all five regions. The Mediterranean Basin, California, and central Chile are seen as nurseries for strong but not spectacular rates of Neogene diversification, while the older landscapes of southwestern Australia and the Cape Region show significant components of both Paleogene and younger Neogene speciation in their diversity. Low rates of extinction suggesting a long association with fire more than high rates of speciation have been key to the extant levels of species richness.
... It is interesting to compare patterns of diversity in fynbos clades between the western Cape with a classic MTC regime and the eastern Cape with aseasonal rainfall. Species diversification in fynbos clades has been much higher in the former (Forest et al., 2018). ...
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Modern attempts to produce biogeographic maps focus on the distribution of species, and the maps are typically drawn without phylogenetic considerations. Here, we generate a global map of zoogeographic regions by combining data on the distributions and phylogenetic relationships of 21,037 species of amphibians, birds, and mammals. We identify 20 distinct zoogeographic regions, which are grouped into 11 larger realms. We document the lack of support for several regions previously defined based on distributional data and show that spatial turnover in the phylogenetic composition of vertebrate assemblages is higher in the Southern than in the Northern Hemisphere. We further show that the integration of phylogenetic information provides valuable insight on historical relationships among regions, permitting the identification of evolutionarily unique regions of the world.
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We suggest Milankovitch climate oscillations as a common cause for geographical patterns in species diversity, species' range sizes, polyploidy, and the degree of specialization and dispersability of organisms. Periodical changes in the orbit of the Earth cause climatic changes termed Milankovitch oscillations, leading to large changes in the size and location of species' geographical distributions. We name these recurrent changes "orbitally forced species' range dynamics" (ORD). The magnitude of ORD varies in space and time. ORD decreases gradual speciation (attained by gradual changes over many generations), increases range sizes and the proportions of species formed by polyploidy and other "abrupt" mechanisms, selects against specialization, and favor dispersability. Large ORD produces species prone neither to extinction nor gradual speciation. ORD increases with latitude, This produces latitudinal patterns, among them the gradient in species diversity and species' range sizes (Rapoport's rule). Differential ORD and its evolutionary consequences call for new conservation strategies on the regional to global scale.
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Aim To test whether it is possible to establish a common biogeographical regionalization for plants and vertebrates in sub-Saharan Africa (the Afrotropical Region), using objective multivariate methods. Location Sub-Saharan Africa (Afrotropical Region). Methods We used 1° grid cell resolution databases for birds, mammals, amphibians and snakes (4142 vertebrate species) and c. 13% of the plants (5881 species) from the Afrotropical Region. These databases were analysed using cluster analysis techniques to define biogeographical regions. A β(sim) dissimilarity matrix was subjected to a hierarchical classification using the unweighted pair-group method with arithmetic averages (UPGMA). The five group-specific biogeographical regionalizations were compared against a regionalization developed from a combined database, and a regionalization that is maximally congruent with the five group-specific datasets was determined using a consensus classification. The regionalizations were interpreted against measures of spatial turnover in richness and composition for the five datasets as well as the combined dataset. Results We demonstrate the existence of seven well-defined and consistent biogeographical regions in sub-Saharan Africa. These regionalizations are statistically defined and robust between groups, with minor taxon-specific biogeographical variation. The proposed biogeographical regions are: Congolian, Zambezian, Southern African, Sudanian, Somalian, Ethiopian and Saharan. East Africa, the West African coast, and the transitions between the Congolian, Sudanian and Zambezian regions are unassigned. The Cape area in South Africa, Afromontane areas and the coastal region of East Africa do not emerge as distinct regions but are characterized by high neighbourhood heterogeneity, rapid turnover of species and high levels of narrow endemism. Main conclusions Species distribution data and modern cluster analysis techniques can be used to define biogeographical regions in Africa that reflect the patterns found in both vertebrates and plants. The consensus of the regionalizations between different taxonomic groups is high. These regions are broadly similar to those proposed using expert opinion approaches. Some previously proposed transitional zones are not recognized in this classification.
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The winter-rainfall region of southern Africa, covered largely by the fynbos and succulent karoo biomes, harbours the world's greatest concentration of geophyte species. Species diversity is greatest in the south-west, where more than 500 species co-occur in one quarter-degree square; in the south-east the values are generally around 100, and in the arid north-west, always less than 50 (more often less than 10). In at least three species-rich genera (Moraea, Eriospermum and Oxalis), the size of storage organs (bulbs, corms, tubers) varies inversely, with the largest average values occurring in the species-poorer areas — both in the north-western, and in the south-eastern parts of the region. This negative correlation between average storage organ size and species diversity is, however, only observed at relatively large spatial scales, which suggests that there is no direct relationship between storage organ size and species diversity. More likely, both these measures are driven by winter rainfall amount and reliability, both of which peak in the south-western Cape. We suggest that reliable winter rainfall makes large storage organs unnecessary and depresses extinction rates, thus leading to the accumulation of species.
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The genus Erica L., with more than 600 species, and a high number of endemics, represents the most remarkable example of floristic diversity in the Cape Floristic Region (CFR). It is largely confined to nutrient-poor, acidic, sandy soils, being one of the most characteristic element of fynbos. The ability to survive fires, resprouting from a lignotuber, is a common trait among Euro-mediterranean Erica species. In contrast, resprouting is fairly uncommon among ericas in the CFR (less than 10%). Most of them are killed by fire, regenerating only but readily by seed germination. An extensive survey on the resprouting ability of South African Erica species was carried out and the pattern of geographical distribution of resprouters and seeders in the CFR was determined. The geographical distribution of these two regeneration classes was related to a climatic gradient of seasonality along the CFR. A pattern of higher proportions of resprouter species towards the mediterranean, strongly seasonal northwestern CFR and the non-seasonal eastern CFR and summer rainfall area outside the CFR was identified. The number of resprouter species reaches a maximum in the eastern CFR and is lower in the southwestern CFR despite the overall higher concentration of species in this subregion. Summer drought strongly influences the effectiveness of post-fire regeneration and growth (i.e. new recruits plus survivors) of Erica species, and is the major selective force accounting for the pattern of distribution of seeders and resprouters in the CFR. A mild mediterranean climate with reliable autumn-winter rains and a short summer drought, typical of the mountain areas of the southwestern CFR, favours recruitment of seeders but hampers recruitment of resprouters. Resprouter species persist and become dominant under harsh conditions for recruitment (severe summer drought) and would coexist with seeders under situations of no summer stress. Diversification is associated with seeder lineages. Hence, number of seeder species will be higher than number of resprouters, especially in the southwestern CFR, where favourable conditions for recruitment allow a massive concentration of seeder species, many of them narrow endemics.
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Aim It has often been suggested that South Africa's Cape fynbos shrublands, although extremely rich in plant species, are poor in insects, thus representing a notable exception from the broad plant–insect diversity relationship. The aims of this study were to compare the diversity patterns of plant-inhabiting insects in fynbos and the vegetation of three neighbouring biomes (grassland, subtropical thicket, and Nama-karoo), and to test for a general relationship between plant diversity and insect diversity across these biomes. Location South-western to south-eastern South Africa. Methods We conducted seasonal plant surveys and sweep insect sampling in 10 × 10 m plots in the Baviaanskloof Conservation Area (Eastern Cape), where all four biomes occur. We also conducted once-only collections in the core area of each biome. Results Fynbos plots had insect diversity values similar to those of grassland and subtropical thicket (a dense, evergreen and spinescent shrubland with a high abundance of succulents and climbers), and significantly higher than Nama-karoo (an open, semiarid shrubland). A remarkably strong positive relationship was found between plant and insect species richness. Main conclusions Previous generalizations were based on a few insect groups (e.g. butterflies, under-represented in fynbos), but ignored published results on other groups (e.g. galling insects, which are in fact over-represented in this vegetation). We show that, overall, insect diversity in fynbos is comparable to that of neighbouring biomes. Fynbos vegetation does not represent a significant exception from the broad positive relationship between plant diversity and insect diversity.
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The Cape Floristic Region (CFR) is characterized by exceptionally high plant species richness and it is yet to be determined whether this is matched by an equally high diversity of insect fauna associated with these plants. In an attempt to do this, data from the literature on the number of insects for various taxa found at different sites in the CFR were compared with equivalent data from other areas in South Africa and elsewhere. Results indicate that the herbivorous insect fauna of the CFR is not particularly rich in species, perhaps except for the small guild of endophagous insects. It is speculated that this is the result of CFR vegetation being a poor food source for herbivores, particularly in view of its sclerophyllous nature. Plant defence mechanisms, such as a pronounced cyanogenic ability of the leaves coupled with the relatively simple architecture of the plants are possible contributing factors. La Région Floristique du Cap (CFR) se caractérise par une richesse exceptionnelle en espèces végétales, et il reste à déterminer si elle abrite aussi une diversitééquivalente en espèces d'insectes, associées à ces plantes. Afin de le savoir, on a comparé les données trouvées dans la littérature portant sur le nombre d'insectes des différents taxons trouvés sur les différents sites de la CFR avec les données équivalentes pour d'autres régions d'Afrique du sud et d'ailleurs. Les résultats indiquent que la faune des insectes herbivores de la CFR n'est pas particulièrement riche en espèces, à l'exception peut-être de la petite guilde des insectes endophages. On suppose que cette situation est le résultat du fait que la végétation de la CFR est une maigre source de nourriture pour les herbivores, spécialement en ce qui concerne sa nature sclérophylle. Les mécanismes de défense des plantes, tels que la capacité cyanogène prononcée des feuilles, couplés à l'architecture relativement simple des plantes, sont de possibles éléments contributeurs.
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Aim The Cape Floristic Region (CFR) (Cape Floristic Kingdom) is currently narrowly delimited to include only the relatively mesic Cape fold mountains and adjacent intermontane valleys and coastal plains. We evaluate the floristic support for expanding the delimitation to include the whole winter-rainfall area (arid and mesic climates) into a Greater CFR. Location Southern Africa, particularly the south-western tip. Methods The initial divisive hierarchical classification analysis twinspan used the presence/absence of vascular plant genera to obtain major floristic groupings in southern Africa. For the more detailed analyses, we scored the flora as present/absent within a set of centres, among which the floristic relationships were investigated (agglomerative methods, upgma and minimum spanning trees). These analyses were conducted with species, genera and families separately. The centres were grouped into five regions. The species richness and endemism was calculated for the centres, regions and combination of regions. The dominant floristic components of each region were sought by calculating the percentage contribution of each family to the flora. Results The divisive method showed that the winter-rainfall areas are floristically distinct from the rest of southern Africa. The species- and generic-level analyses revealed five regions: CFR, Karoo Region, Hantam-Tanqua-Roggeveld Region, Namaqualand Region and Namib-Desert Region. The CFR has the highest endemism and richness. However, the combination of the CFR, the Hantam-Tanqua-Roggeveld Region and the Namaqualand Region results in a higher total endemism. Combined, these three regions almost match the region delimited by the twinspan analysis, and together constitute the Greater CFR. Main conclusions The CFR constitutes a valid floristic region. This is evident from the endemism and the distinctive composition of the flora. However, the total endemism is higher for the whole winter-rainfall area, and this supports the recognition of the larger unit. If floristic regions are to be delimited only on endemism, then the Greater CFR is to be preferred. If floristic regions are delimited on the composition of their floras at family level, then the support for such a grouping is weaker.
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Southern Africa is certainly not a naturally bounded area so that there are several possibilities for delineating it and concepts about its extent. Wellington* discussed the various possibilities for delineation and suggested that one line stands out more clearly and definitely as a physical boundary than any other, namely the South Equatorial Divide, the watershed between the ZaIre, Cuanza and Rufiji Rivers on the one hand and the Z ambezi, Cunene and Rovuma Rivers on the other. This South Equatorial Divide is indeed a major line of separation for some organisms and is also applicable in a certain geographical sense, though it does not possess the slightest significance for many other groups of organisms, ecosystems or geographical and physical features of Africa. The placing of the northern boundary of southern Africa differs in fact strongly per scientific dis­ cipline and is also influenced by practical considerations regarding the possibilities of scientific work as subordinate to certain political realities and historically grown traditions. This is illustrated, for example, in such works as the Flora of Southern Africa, where the northern boundary of the area is conceived as the northern and eastern political boundaries of South West Africa, South Africa and Swaziland. Botswana, traditionally included in the area covered by the Flora Zambesiaca, thus forms a large wedge in 'Southern Africa'.
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Protected areas buffer species from anthropogenic threats and provide places for the processes that generate and maintain biodiversity to continue. However, genetic variation, the raw material for evolution, is difficult to capture in conservation planning, not least because genetic data require considerable resources to obtain and analyze. Here we show that freely available environmental and geographic distance variables can be highly effective surrogates in conservation planning for representing adaptive and neutral intraspecific genetic variation. We obtained occurrence and genetic data from the IntraBioDiv project for 27 plant species collected over the European Alps using a gridded sampling scheme. For each species, we identified loci that were potentially under selection using outlier loci methods, and mapped their main gradients of adaptive and neutral genetic variation across the grid cells. We then used the cells as planning units to prioritize protected area acquisitions. First, we verified that the spatial patterns of environmental and geographic variation were correlated, respectively, with adaptive and neutral genetic variation. Second, we showed that these surrogates can predict the proportion of genetic variation secured in randomly generated solutions. Finally, we discovered that solutions based only on surrogate information secured substantial amounts of adaptive and neutral genetic variation. Our work paves the way for widespread integration of surrogates for genetic variation into conservation planning.
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It has been known for many decades that the diversity of clades endemic to the Greater Cape Floristic Region (GCFR) declines along a longitudinal (west-east) gradient, in concert with a reduction in the proportion of winter rainfall. In honour of the pioneering work by Margaret Levyns, we recognise this pattern as Levyns’ Law, and illustrate it with distribution data for 23 speciose endemic clades. All patterns were consistent with Levyns’ Law. Here we assess explanations for Levyns’ Law in terms of theories invoked to explain the evolution of diversity patterns along other diversity macro-gradients. Neither the metabolic nor the ecological opportunity hypotheses convincingly explain Levyns’ Law. Surprisingly, almost no research has been done on the evolutionary opportunities associated with the Mid Miocene onset of a winter-rainfall regime in the western GCFR, despite this phenomenon being frequently invoked to explain the diversification of many GCFR clades. In all other respects, niche space both now and historically shows no major differences between the western, winter rainfall, and the eastern, year-round rainfall regions of the GCFR. We suggest that higher Pleistocene climatic and biome stability in the western GCFR – the age and area hypothesis – best explains Levyns’ Law. Pronounced instability in the east reduced diversification rates via increased rates of extinction of lineages. Testing the age and area hypotheses will require, inter alia, proxy data for Pleistocene environmental and biotic dynamics, an analysis of diversification rates in relation to rainfall seasonality, and an assessment of the patterns of phylogenetic diversity in the GCFR.
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Legacies of paleoclimates in contemporary biodiversity patterns have mostly been investigated with global datasets, or with weakly dispersive organisms, and as a consequence been interpreted in terms of geographical or physical constraints. If paleoclimatic legacies also occurred at the regional scale in the distributions of vagile organisms within biomes, they would rather suggest behavioral constraints on dispersal, i.e., philopatric syndromes. We examined 1) the residuals of the regression between contemporary energy and passerine species richness in South African biomes and 2) phylogenetic dispersion of passerine assemblages, using occupancy models and quarter-degree resolution citizen science data. We found a northeast to southwest gradient within mesic biomes congruent with the location of Quaternary mesic refugia, overall suggesting that as distance from refugia increased, more clades were lacking from local assemblages. A similar but weaker pattern was detected in the arid Karoo Biomes. In mobile organisms such as birds, behavioral constraints on dispersal appear strong enough to influence species distributions thousands of years after historical range contractions.
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Although existing bioregional classification schemes often consider the compositional affinities within regional biotas, they do not typically incorporate phylogenetic information explicitly. Because phylogeny captures information on the evolutionary history of taxa, it provides a powerful tool for delineating biogeographical boundaries and for establishing relationships among them. Here, we present the first vegetation delineation of the woody flora of southern Africa based upon evolutionary relationships.
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The rugged topography of the Cape Floristic Region (CFR), South Africa, is frequently invoked to explain the spectacular radiation of the Cape flora, but the mechanisms involved remain unclear. Where recent authors emphasize the importance of elevation gradients as stimuli for ecological speciation, earlier workers stressed the role of topography as an isolating mechanism, particularly in montane lineages. Using six Cape plant lineages, we tested whether elevation niches are phylogenetically conserved. We then assessed whether high-elevation species are more consistently range-restricted than low-elevation species, and whether high-elevation sisters show stronger range exclusivity (allopatry) and weaker ecological and phenotypic differentiation, suggestive of nonecological speciation. Elevation niches tend to be phylogenetically conserved. Also, high-elevation species are more consistently range-restricted than low-elevation species, potentially explaining the generally stronger range exclusivity of high-elevation sisters. While the high-elevation zone is less homogeneous ecologically, more data are required to demonstrate that high-elevation sister species show generally weaker ecological and phenotypic differentiation. Topographic complexity promotes geographical isolation at high elevations, thereby providing opportunities for nonecological, vicariant speciation. While recognizing the need for additional data, we suggest that the upland and lowland floras of the CFR may differ with regard to predominant speciation mode. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.
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The patterns of species richness in the south-western Cape Province, South Africa, at a quarter-degree scale are documented for several plant taxa typical of the Cape flora, i.e. Restionaceae, Ericaceae, Proteaceae, Pentaschistis (Nees) Stapf (Poaceae) and Aspalathus L. (Fabaceae). The patterns of species richness are very similar for all taxa investigated. These patterns are correlated to a range of environmental factors: precipitation, altitude, substratum and vegetation type. It is shown that total precipitation is the best predictor for the patterns of species richness, but that this is to some extent correlated with the range of precipitation and the altitude range. To test for the effect of individual factors, selected samples in which One environment factor varied, were compared. This clearly showed that rainfalls is the best predictor. The number of substrate types, curiously, is not strongly correlated to the patterns of species richness.
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Recent species definitions have placed emphasis on "diagnostic characters" rather than isolating mechanisms. Such characters can be informative about the evolutionary processes which lead to speciation in highly diversified plant groups, such as those found in the Cape floral region of South Africa. Rampant speciation in the Cape flora has often been attributed to heterogeneity of the physical environment, yet many large Cape genera show radiation in floral, rather than vegetative, characters, which suggests that adaptation to pollinators has played a major role in speciation. Selection for more efficient pollination systems in a pollinator-limited context, rather than isolating mechanisms, is suggested to be the primary driving force behind floral evolution in the Cape flora.
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Southern Africa, including Namibia (South West Africa), South Africa, Lesotho, Swaziland, and Botswana, covers an area of ca. 2.5 million km2. The flora comprises ca. 18,500 species in 1,930 genera. There are 10 endemic families, while 80% of the species and 29% of the genera are endemic. Of the five phytogeographic regions recognized, the Cape Floristic Region is the richest and most distinctive, and in this small area there are some 8,550 species in 957 genera. Most of the subcontinent is arid to semiarid. Its rich and diverse flora, contrasting with the relatively depauperate tropical African flora, is believed to have evolved gradually since the early to mid-Tertiary at the southern edge of the tropics as Africa became progressively drier, partly from an ancient southern African temperate flora and partly from a tropical African forest flora. The large number of species in the Cape Region and adjacent arid areas probably evolved recently in the last 1-2 million years as the climate fluctuated violently during the Pleistocene. Peculiarities of the flora include an unusually high proportion of petaloid monocots, a wealth of succulents, mainly in winter rainfall arid areas, large numbers of sclerophyllous to microphyllous shrubs, and very few annuals.
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There is increased evidence that incorporating evolutionary history directly in conservation actions is beneficial, particularly given the likelihood that extinction is not random and that phylogenetic diversity (PD) is lost at higher rates than species diversity. This evidence is even more compelling in biodiversity hotspots, such as Madagascar, where less than 10% of the original vegetation remains. Here, we use the Leguminosae, an ecologically and economically important plant family, and a combination of phylogenetics and species distribution modelling, to assess biodiversity patterns and identify regions, coevolutionary processes and ecological factors that are important in shaping this diversity, especially during the Quaternary. We show evidence that species distribution and community PD are predicted by watershed boundaries, which enable the identification of a network of refugia and dispersal corridors that were perhaps important for maintaining community integrity during past climate change. Phylogenetically clustered communities are found in the southwest of the island at low elevation and share a suite of morphological characters (especially fruit morphology) indicative of coevolution with their main dispersers, the extinct and extant lemurs. Phylogenetically over-dispersed communities are found along the eastern coast at sea level and may have resulted from many independent dispersal events from the drier and more seasonal regions of Madagascar. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
Article
Aim Biodiversity hotspots have important roles in conservation prioritisation, but efficient methods for selecting among them remain debated. Location Southern Africa. Methods In this study, we used data on the dated phylogeny and geographical distribution of 1400 tree species in southern Africa to map regional hotspots of species richness (SR), phylogenetic diversity (PD), phylogenetic endemism (PE), species endemism (CWE), and evolutionary distinctiveness and global endangerment (EDGE). In addition, we evaluated the efficiency of hotspots in capturing complementary areas of species richness and phylogenetic diversity. We examined the spatial overlap among hotspots for each metric, and review how well one metric may serve as a surrogate for others. We then evaluated the effectiveness of current conservation areas in capturing these different facets of diversity and complementary areas. Lastly, we explored the environmental factors influencing the distribution of these diversity metrics in southern Africa. Results We reveal large spatial incongruence between biodiversity indices, resulting in unequal representation of PD, SR, PE, CWE and EDGE in hotspots and currently protected areas. Notably, no hotspot area is shared among all five measures, and 69% of hotspot areas were unique to a single diversity metric. Areas selected using complementarity are even more dispersed, but capture rare diversity that is overlooked by the hotspot approach. Main conclusions An integrative approach that considers multiple facets of biodiversity is needed if we are to maximise the conservation of tree diversity in southern Africa.
Article
The origin of fire-adapted lineages is a long-standing question in ecology. Although phylogeny can provide a significant contribution to the ongoing debate, its use has been precluded by the lack of comprehensive DNA data. Here, we focus on the ‘underground trees’ (=geoxyles) of southern Africa, one of the most distinctive growth forms characteristic of fire-prone savannas. We placed geoxyles within the most comprehensive dated phylogeny for the regional flora comprising over 1400 woody species. Using this phylogeny, we tested whether African geoxyles evolved concomitantly with those of the South American cerrado and used their phylogenetic position to date the appearance of humid savannas.� We found multiple independent origins of the geoxyle life-form mostly from the Pliocene, a period consistent with the origin of cerrado, with the majority of divergences occurring within the last 2 million yr. When contrasted with their tree relatives, geoxyles occur in regions characterized by higher rainfall and greater fire frequency. Our results indicate that the geoxylic growth form may have evolved in response to the interactive effects of frequent fires and high precipitation. As such, geoxyles may be regarded as markers of fire-maintained savannas occurring in climates suitable for forests.
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ABSTRACT Comprising a land area of ca. 90,000 km,, less than one twentieth (5%) the land area of the southern African subcontinent, the Cape Floristic Region (CFR) is, for its size, one of the world’s richest areas of plant species diversity. A new synoptic flora for the Region has made possible an accurate reassessment of the flora, which has an estimated 9030 vascular plant species (68.7% endemic), of which 8920 species are flowering plants (69.5% endemic). The number of species packed,into so small an area is remarkable,for the temperate,zone and compares,favorably with species richness for areas of similar size in the wet tropics. The Cape region consists of a mosaic,of sandstone,and shale substrata with local areas of limestone. It has a highly dissected, rugged topography, and a diversity of climates with rainfall mostly falling in the winter months and varying from 2000 mm,locally to less than 100 mm. Ecological gradients are steep as a result of abrupt differences in soil, altitude, aspect, and precipitation. These factors combine to form an unusually large number of local habitats for plants. Sandstone-derived soils have characteristically low nutrient status, and many plants present on such soils have low seed dispersal capabilities, a factor promoting localized distributions. An unusual family composition includes Iridaceae, Aizoaceae, Ericaceae, Scrophulariaceae, Proteaceae, Restionaceae, Rutaceae, and Orchidaceae among the 10 largest families in the flora, following Asteraceae and Fabaceae, as the most speciose families. Disproportionate radiation has resulted in over 59.2% species falling in the 10 largest families and 77.4% in the largest 20 families. Twelve genera have more than 100 species and the 20 largest genera contribute some 31% of the total species. Species richness of the Cape flora is hypothesized to be the result of geographic and parapatric radiation in an area with a mosaic of different habitats due to local soil, climate, and altitudinal differences that combine,to produce steep ecological gradients. Also contributing to the diversity has been a relatively stable geological history since the end of the Miocene that saw the establishment,of a semi-arid and extreme seasonal climate at the southwestern,part of southern Africa. Key words: floristics, Mediterranean-type climate, phytogeography, plant diversity, southern Africa, speciation. Situated at the southwestern tip of the African
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The floras of mediterranean SW Australian shrublands (kwongan) and SW Cape fynbos have evolved under conditions of low soil nutrients and recurrent fire. The vegetation of both regions (Gondwanan shrublands) is broadly convergent in structure and functioning. In particular these shrublands have high species diversity at all levels. Populations respond differentially to varying components of the fire regime and post-fire population extinction is not uncommon. Since each fire is a unique event, high alpha richness could be maintained by the creation of fire-induced transient niches resulting in differential establishment. Under this form of 'lottery' recruitment, competitive effects are weakened and many species of the same guild can coexist. Recurrent fire is probably a major driving force in the massive speciation of the Gondwanan shrubland floras. Small demes would be isolated in peculiar habitats after fire-induced population fragmentation. Strong disruptive selection would result in the rapid evolution of isolated populations into distinct and specialized species. -from Author
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For a new approach to the phytogeography of the Namib region three sets of data are analyzed, (a) distribution data of ca. 1700 taxa, (b) habitat informations of a large number of taxa, collected in course of an extensive phytosociological survey, (c) distribution data of characteristic life form spectra and plant formations. In this paper, as a first step of a comprehensive phytochorological analysis, phytochoria and their limits are proposed as derived from frequently observed areas of distribution, while a numerical analysis of the complete flora of these phytochoria is in preparation. Considering with emphasis the flora of zonal habitats (Walter 1986), two major phytochorological units are recognized: 1. The Succulent Karoo Region (Greater Cape Flora) 1.1 Namaqualand-Namib Domain 1.2 Southern Karoo Domain 2. The Nama Karoo Region (Palaeotropis) 2.1 Namaland Domain 2.2 Eastern Karoo Domain 2.3 Damaraland-Kaokoland Domain
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Taxonomic, edaphic and biological aspects of endemism were studied in a phanerogamous flora from the Agulhas Plain, a coastal lowland area of the Cape Floristic Region. Of the 1751 species in the flora, 23.6% were regional endemics and 5.7% were local endemics. Families which were over-represented in terms of endemics included the Ericaceae, Rutaceae, Proteaceae and Polygalaceae. Under-represented families included the Poaceae, Cyperaceae, Scrophulariaceae and Orchidaceae. Highest levels of local endemism were recorded on limestone and colluvial acid sand. Sixty-nine percent of regional endemics and 85% of local endemics were confined to a single substratum. An analysis of the frequency of biological traits associated with species with different categories of endemism enabled the establishment of a biological profile of a local endemic: a dwarf to low, non-sprouting shrub with soil stored seeds which are ant-dispersed and/or form a symbiotic relationship with microbes. It is argued that lineages with these characteristics are vulnerable to severe population reduction or even local extinction. An effect of this would be the promotion of rapid, edaphic speciation as a result of catastrophic selection. Thus, certain traits (e.g. non-sprouting) prevail or even predominate in the flora not because of any adaptive advantage but because high speciation rates of lineages which possess them, overwhelm low survival rates.
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This paper investigates the role of heterogeneity and speciation/extinction history in explaining variation in regional scale (c. 0.1–3000 km2) plant diversity in the Cape Floristic Region of south-western Africa, a species- and endemic-rich biogeographical region. We used species-area analysis and analysis of covariance to investigate geographical (east vs. west) and topographic (lowland vs. montane) patterns of diversity. We used community diversity as a surrogate for biological heterogeneity, and the diversity of naturally rare species in quarter degree squares as an indicator of differences in speciation/extinction histories across the study region. We then used standard statistical methods to analyse geographical and topographic patterns of these two measures. There was a clear geographical diversity pattern (richer in the west), while a topographic pattern (richer in mountains) was evident only in the west. The geographical boundary coincided with a transition from the reliable winter-rainfall zone (west) to the less reliable non-seasonal rainfall zone (east). Community diversity, or biological heterogeneity, showed no significant variation in relation to geography and topography. Diversity patterns of rare species mirrored the diversity pattern for all species. We hypothesize that regional diversity patterns are the product of different speciation and extinction histories, leading to different steady-state diversities. Greater Pleistocene climatic stability in the west would have resulted in higher rates of speciation and lower rates of extinction than in the east, where for the most, Pleistocene climates would not have favoured Cape lineages. A more parsimonious hypothesis is that the more predictable seasonal rainfall of the west would have favoured non-sprouting plants and that this, in turn, resulted in higher speciation and lower extinction rates. Both hypotheses are consistent with the higher incidence of rare species in the west, and higher levels of beta and gamma diversity there, associated with the turnover of species along environmental and geographical gradients, respectively. These rare species do not contribute to community patterns; hence, biological heterogeneity is uniform across the region. The weak topography pattern of diversity in the west arises from higher speciation rates and lower extinction rates in the topographically complex mountains, rather than from the influence of environmental heterogeneity on diversity.
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Coastal South Africa draws interdisciplinary interests due to the co-occurrence of a rich record for early human behavioral modernity, hyper-diverse vegetation with very high endemism (the Cape Floral Region), and globally influential oceanic and climate systems. High resolution and continuous climate and environmental records are needed to provide the context for the evolution of behavioral modernity and this diverse flora. Here we present the first such record for climate and environmental change from 90 000 to 53 000 years ago from the southern Cape coast. This important time span covers a burst of expression of several indicators of human behavioral modernity, as well as several key cycles in global climate change. Our research location is ideally placed near the location of several critical archaeological sites, near the boundary of the winter and summer rainfall regimes, and close to isotopically distinct floral zones. We used isotopic analysis of precisely dated speleothems to document shifting vegetation and rainfall, and show that the presence of winter rain and C3 grasses waxes and wanes in response to Southern Hemisphere shifts in SSTs and global temperature. When proxies of global temperatures indicate warmer conditions, δ18O and δ13C indicate more winter rain and more C3 grasses, respectively, and vice versa. This record displays abrupt and short-term changes previously undocumented. It is often argued that the Cape Floral Region partially owes its high diversity to relative climatic stability. Our record shows isotopic variability that at least matches that displayed in the Levantine Mediterranean system, so climatic stability may not have characterized the south coast. One short-lived phase of human technological innovation (the Still Bay) associated with early evidence for behavioral modernity occurs synchronous with an abrupt environmental perturbation. Early modern humans in this region confronted a variable climate and adapted quickly in a manner similar to behaviorally modern humans.
Article
The Cape Peninsula is a well known area of exceptional plant diversity and endemism within the Cape Floristic Region, but an accurate and complete listing of the endemic seed plant species has been lacking. Here, we present a list of the 158 species and 3 subspecies that are currently regarded as Cape Peninsula endemics, with discussion on the profile of the endemic flora, plant hotspots within the area, and conservation issues. Endemics constitute 7% of the total Peninsula flora. 76% of the endemic species fall within only 10 families, with Erica being the genus with the greatest number of endemic species on the Peninsula (39). The Peninsula is identified as a centre of endemism for Roella, Tetraria, Serruria, and Muraltia. Many families are notably under-represented in terms of endemic species on the Peninsula, including Geraniaceae, Oxalidaceae, Thymelaeaceae, Apiaceae, Hyacinthaceae, Poaceae, Rhamnaceae, Rutaceae, Orchidaceae, and Asteraceae. 62% of the endemics are shrubs or dwarf shrubs. 41% of the endemics are currently Red Data Book listed, but the Table Mountain National Park conserves a large percentage of the montane habitat, as well as significant lowland habitat in the extreme south.