Succulent Karoo Biome Research Articles

The phylogenetically isolated South African endemic diving beetle Caperhantus cicurius (Fabricius, 1787): redescription and range extensions (Coleoptera, Dytiscidae, Colymbetinae)

New distribution records and a redescription are presented for Caperhantus cicurius (Fabricius, 1787), a diving beetle endemic to the Cape region of South Africa, which is only distantly related to other Afrotropical dytiscids. We show that the species is much more widely distributed than previously recognized and present details of occupied habitats for the first time. Caperhantus cicurius occurs throughout the winter rainfall zone in South Africa, from Namaqualand to the Eastern Cape Province, particularly in temporary waters in the Fynbos and Succulent Karoo biomes.

Vegetation change on mine sites in the most arid part of the Succulent Karoo Biome and their implications for mine closure

Restoring biodiversity is an important component of mine site rehabilitation. It needs to be evaluated regularly to assess success or failure of restoration methods and compliance with mine closure completion criteria. Yet vegetation dynamics in the driest part of the Succulent Karoo Biome are poorly understood. This study contributes to the question whether succession theory applies in this ecosystem by investigating 40 sites in a completely altered mining landscape and accompanying reference sites in the southern Namib within a 17-year time interval. Plant cover and species composition of the same site were compared between a field survey in 2005 and 2022. Multivariate analyses indicated that the importance of investigated environmental variables shifted between the survey periods, affecting the secondary vegetation on altered landforms as well as the undisturbed reference sites. This complicated the interpretation of perceived changes between the 2005 and 2022 surveys, making it difficult to detect successional trends. A drying of the general area is indicated which reduced species richness and cover overall and may have precipitated a change in habitat from stabilised to shifting dunes with concomitant changes to more sand-tolerant species in the southern part of the study area. These changes in both natural and secondary vegetation pose challenges when deciding on appropriate measures for restoration monitoring and setting completion criteria for mine closure.

Karoo dwarf tortoises (Chersobius boulengeri) prefer and disperse doll's roses (Hermannia spp.)

Tortoises inhabit arid regions where they may represent a significant herbivorous component, but are among the most threatened of tetrapod groups. Studying tortoise diets can help predict potential trophic disruptions following extinctions of tortoise populations, and inform conservation. We studied the diet of Karoo dwarf tortoises (Chersobius boulengeri), an endangered endemic of the arid Nama and Succulent Karoo biomes in South Africa, using vegetation analysis, DNA metabarcoding, morphological evaluation of faeces, a germination trial, and focal feeding observations. DNA metabarcoding was highly successful in the identification of dietary items. Karoo dwarf tortoises fed on a broad diet, including approximately 10 taxa eaten frequently. Specifically, doll's roses (five species in the genus Hermannia) were eaten more frequently than would be expected based on their availability, whereas grasses were rejected, for a dietary Proportional Similarity Index of 0.31–0.38. Dietary selection was likely related to water and nutrient contents of plant taxa. At least four plant species (including doll's roses) germinated from faecal samples, suggesting mutualistic relationships with Karoo dwarf tortoises. The habitat preference of Karoo dwarf tortoises (i.e., well-structured rocky terrain) may provide germination microsites with ample shade and run-off water to benefit seedling recruitment in an arid environment.

Modelling land condition to augment Land Degradation Neutrality assessments - The succulent Karoo biome of South Africa as a case study

Land degradation is a threat to ecosystems and to already vulnerable people who live in dryland environments. The United Nations Convention to Combat Desertification (UNCCD) has been tasked with addressing the global challenges posed by land degradation. Although the complexities around land degradation have more recently been acknowledged, spatial modelling of this phenomenon remains a global challenge. In this study, measures of productivity derived from Landsat 8 and Sentinel-2A data have been integrated with local climate, land use, and socio-economic data to provide a more meaningful regional conceptual framework for land degradation. We create a novel method to map land condition utilising a set of 26 biological, topographic, climatic and land use covariates. The model results can be viewed in isolation as a measure of vegetation cover but are more useful when interpreted within the context of the environmental covariates. This can be accomplished through the Succulent Karoo Land Condition Inspector Google Earth Engine application. The data are intended to assist conservation planners in providing spatial data related to the current condition of the land in the biome, as well as to highlight areas where biodiversity is potentially at greater threat and where restoration initiatives or climate change adaptation are most needed.

Vegetation dynamics over 18 years in response to seasonal climatic conditions and land use in the Kamiesberg mountains of the succulent Karoo, South Africa

Projections of vegetation change in response to future global change conditions are challenged by the lack of long-term, empirical data on how vegetation responds to the variability in climatic conditions. This is particularly true for biodiverse systems that are threatened by climate change such as the winter-rainfall Succulent Karoo biome of southern Africa. In this study we analyse long-term data (2002–2019) of two biodiversity observatories from the Kamiesberg Mountains in the Succulent Karoo. We employed the R package GLMMtmb to analyse counts of abundance and estimated cover values of vegetation as response variables and seasonal Standardised Precipitation-Evapotranspiration Index (SPEI), annual livestock density, topography and soil surface structure as predictors for the interannual change of life forms under low and high land use intensity. We compared the life form composition at the two contrasting land use types and found the cover and abundance of leaf succulents to be higher under low grazing intensity and that of stem succulents to be higher under high grazing intensity. The cover and abundance of herbaceous life forms varied over the years depending on the seasonal weather conditions. Our GLMM results reveal counts of abundance to be a sensitive predictor for population dynamics in various herbaceous and shrub life form types. Estimated cover values showed less of a response to interannual differences in the environmental drivers. All life forms responded strongly to high humid and cool conditions in the second half of the winter rainfall period, when the temperatures increase again. The abundance of leaf-succulent and non-succulent shrubs also responded positively to moderate conditions towards the end of the dry season. The extensive and hot dry summer season in turn had a significant negative effect on the survival of particularly young plants with low cover. Cover values showed no response to the conditions of the late dry season and were generally less sensitive to the variance in seasonal climatic conditions. Our results suggest that future changes in interannual patterns in climatic conditions will affect life form composition of the vegetation.

Entheseal changes and activity patterns in southern African hunter-gatherer/herders from the Holocene.

Activity patterns and lifeways in southern African hunter-gatherer/herders (sAHGH) during the Holocene were dynamic, with subsistence activities and mobility varying through space and time. In this study, spatial and temporal variations in entheseal changes (ECs) are assessed as physical activity markers in sAHGH from the Holocene. The Coimbra method was used to assess fibrocartilaginous ECs in the upper and lower limbs of 118 sAHGH from the Holocene. Descriptive statistics and generalized estimating equations were used to explore the association between ECs, sex, age, ecological biomes, and temporality. A total of 118 individuals were sampled, comprising 67 males, and 42 females, mostly from the fynbos (59/118), forest (30/118) and succulent karoo biomes (16/118). ECs were identified in 94% of the sample. Interobserver scoring suggests our findings are likely to underrepresent the extent of EC score differences in sAHGH. Findings indicate a complex pattern of physical activity in sAHGH with differences attributable to regional ecology rather than age or sex. More prominent ECs were identified in individuals from the forest biome, relative to the fynbos and succulent karoo biomes. These were consistent with resource search and processing costs, and terrain differences in these ecozones. ECs were only detected temporally relative to the infiltration of pastoralism (at 2000 BP) when the data were stratified by ecological biome. This study provides evidence that regional ecology plays a central role in driving activity patterns regardless of social or cultural organization. Ecological biomes provide a gradient along which the temporal impact of resource limitations on human biology, activity patterns and sociocultural behaviors can be studied.

What Is Wrong with Frankenia nodiflora Lam. (Frankeniaceae)? New Insights into the South African Sea-Heaths.

The taxonomic identity and phylogenetic relationships of several southern African perennial taxa related to Frankenia repens are discussed. In particular, F. nodiflora Lam., a misunderstood species described from the Cape region and synonymised to F. pulverulenta, is restored for plants endemic to salt-pans and riverbeds in the coastal lowlands across the Cape Flats (Western Cape province, South Africa). Further, a revision of morphologically close plants, usually identified as F. pulverulenta or F. repens, also occurring in similar saline ecosystems of the inland western South Africa revealed the existence of two distinct new entities not matching any described taxa of the genus. Molecular analyses of nuclear ribosomal (ITS1-5.8S-ITS2 region) DNA sequence data together with morphological divergence allow recognition of those taxa at species rank, within an independent lineage close to F. repens. In consequence, two new sea-heath species are described in the so-called "F. repens group": F. nummularia from the Nama-Karoo Biome (Western Cape and Northern Cape provinces), and F. anneliseae from the Succulent Karoo Biome (Northern Cape province). Full morphological description and type designation are reported for each accepted species as well as data on ecology, habitat, distribution, and taxonomic relationships to other close relatives are given. Further, an identification key is presented to facilitate recognition of the southern African taxa of Frankenia.

The effects of habitat loss and fragmentation on the relative abundance and conservation of Ludwig’s Bustard Neotis ludwigii in South Africa

Ludwig’s Bustard Neotis ludwigii is near-endemic to the semi-arid shrublands of southwestern southern Africa and is listed as Endangered. The primary threat to this species is collisions with overhead powerlines; however, loss and fragmentation of its habitat may contribute to its population decline. The 1990 and 2020 land-use land-cover (LULC) maps prepared for South Africa were used to determine the LULC categories that best describe suitable habitat for Ludwig’s Bustard using beta regressions and data on exact localities, as recorded in the real-time BirdLasser logging app. Optimized Hot Spot Analysis was used to determine the priority areas for conserving Ludwig’s Bustard and its habitat. Beta regression models were compiled using the reporting rate for this bird and the total surface area of suitable habitat, and three other landscape metrics, calculated using the per pentad LULC categories considered suitable habitat for the bird. These analyses revealed that, between the first and second Southern African Bird Atlas Projects, the distribution range of Ludwig’s Bustard increased by 153 quarter-degree grid cells, whereas the reporting rate for the species declined by 5.6%, along with a small net decline in its quarterdegree-grid-cell-based area of occupancy, its pentad-based area of occupancy and habitat. The habitat of Ludwig’s Bustard is dominated by shrubland with limited grassland, in primarily the Nama Karoo and Succulent Karoo biomes, and the Grassy Karoo Biome in the eastern part of its distribution. In the relative abundance hot spot of Ludwig’s Bustard, there does not currently appear to be any significant loss or fragmentation (distance between patches) of its habitat. A landscape-based approach to conserving Ludwig’s Bustard can be achieved by expanding the current network of protected areas and conserving critical biodiversity areas and ecosystem support areas, especially in the bird’s relative abundance hot spots in the Nama Karoo and Succulent Karoo biomes.

An evaluation of different approaches which use Google Street View imagery to ground truth land degradation assessments.

Member states of the United Nations Convention to Combat Desertification are required to report on the proportion of land that is degraded in their countries, a requirement that is also tied into the UN Sustainable Development Goals (SDGs). National land degradation assessments are often conducted with the use of remote sensing data which are not always ground truthed. Google Street View (GSV) provides high resolution, panoramic imagery across large parts of the world that has the potential to be used to ground truth land degradation assessments. We apply three different methodologies (visual interpretation of GSV images, GSV image classification and vegetation index extraction) to derive vegetation cover estimates from Google Street View imagery for the Hardeveld bioregion of the Succulent Karoo biome in South Africa. Visual estimates of cover best predict known habitat condition values (adjusted R2 = 0.86), whilst estimates derived from an unsupervised classification of GSV images also predict habitat condition relatively well (adjusted R2 = 0.52). These results show the potential for using GSV imagery, and other large collections of ground-level landscape photographs, as a rough ground-truthing tool, especially in instances where more traditional ground-truthing approaches are not possible.

Three new species in the genus Ficinia (Cyperaceae, tribe Cypereae) from the Greater Cape Floristic Region of South Africa

Despite over 300 years of botanical inventory, new species continue to be discovered within the Greater Cape Floristic Region of South Africa. Recent field work in the ecotone of the Fynbos and Succulent Karoo biomes has revealed three species of Ficinia that are new to science. Based on field observation and comparison with existing material in major herbaria, we describe and name F. bolusiana, F. stirtonii and F. swartruggensis.

Environmental influences on human innovation and behavioural diversity in southern Africa 92-80 thousand years ago.

Africa's Middle Stone Age preserves sporadic evidence for novel behaviours among early modern humans, prompting a range of questions about the influence of social and environmental factors on patterns of human behavioural evolution. Here we document a suite of novel adaptations dating approximately 92-80 thousand years before the present at the archaeological site Varsche Rivier 003 (VR003), located in southern Africa's arid Succulent Karoo biome. Distinctive innovations include the production of ostrich eggshell artefacts, long-distance transportation of marine molluscs and systematic use of heat shatter in stone tool production, none of which occur in coeval assemblages at sites in more humid, well-studied regions immediately to the south. The appearance of these novelties at VR003 corresponds with a period of reduced regional wind strength and enhanced summer rainfall, and all of them disappear with increasing winter rainfall dominance after 80 thousand years before the present, following which a pattern of technological similarity emerges at sites throughout the broader region. The results indicate complex and environmentally contingent processes of innovation and cultural transmission in southern Africa during the Middle Stone Age.

Variability in soil and foliar stable carbon and nitrogen isotope compositions in the winter rainfall biomes of South Africa

We present the stable carbon and nitrogen isotope compositions of 204 plants and 99 soils from South Africa's Fynbos and Succulent Karoo biomes, from which we assess variability in δ13C and δ15N within and between the biomes. Higher foliar δ13C in the Succulent Karoo (−22.4 ± 4.7‰) primarily reflects a greater abundance of CAM photosynthesis relative to Fynbos (−25.7 ± 3.5‰). For C3 plants within the Fynbos Biome, there is no statistically significant relationship between δ13C and climate, suggesting that within the present sampling framework, local-scale variability masks expected climatic controls on C3 plant δ13C. Soil and foliar δ15N are highly variable, but foliar δ15N is significantly higher in the Succulent Karoo (7.7 ± 3.9‰) compared to the Fynbos (4.4 ± 3.3‰). Soil and foliar δ15N correlate, with soils 3 ± 1‰ more enriched in 15N. Both soil and foliar δ15N show stronger correlations with climate than δ13C, and they accord with the previously observed tendency for higher δ15N with greater aridity. The relationship between δ15N and mean annual rainfall is, however, relatively steep (2.4 ± 0.6‰ per 100 mm rainfall), potentially implying additional controls on δ15N variability. These data provide a benchmarking of contemporary isotopic variability, anticipated to support future archaeological, palaeoenvironmental and C and N cycling research.

Rhizosphere Diazotrophs and Other Bacteria Associated with Native and Encroaching Legumes in the Succulent Karoo Biome in South Africa.

Total and diazotrophic bacteria were assessed in the rhizosphere soils of native and encroaching legumes growing in the Succulent Karoo Biome (SKB), South Africa. These were Calobota sericea, Lessertia diffusa, Vachellia karroo, and Wiborgia monoptera, of Fabaceae family near Springbok (Northern Cape Province) and neighboring refugia of the Fynbos biome for C. sericea for comparison purposes. Metabarcoding approach using 16S rRNA gene revealed Actinobacteria (26.7%), Proteobacteria (23.6%), Planctomycetes, and Acidobacteria (10%), while the nifH gene revealed Proteobacteria (70.3%) and Cyanobacteria (29.5%) of the total sequences recovered as the dominant phyla. Some of the diazotrophs measured were assigned to families; Phyllobacteriaceae (39%) and Nostocaceae (24.4%) (all legumes), Rhodospirillaceae (7.9%), Bradyrhizobiaceae (4.6%) and Methylobacteriaceae (3%) (C. sericea, V. karroo, W. monoptera), Rhizobiaceae (4.2%; C. sericea, L. diffusa, V. Karroo), Microchaetaceae (4%; W. monoptera, V. karroo), Scytonemataceae (3.1%; L. diffusa, W. monoptera), and Pseudomonadaceae (2.7%; V. karroo) of the total sequences recovered. These families have the potential to fix the atmospheric nitrogen. While some diazotrophs were specific or shared across several legumes, a member of Mesorhizobium species was common in all rhizosphere soils considered. V. karroo had statistically significantly higher Alpha and distinct Beta-diversity values, than other legumes, supporting its influence on soil microbes. Overall, this work showed diverse bacteria that support plant life in harsh environments such as the SKB, and shows how they are influenced by legumes.

Regional land degradation assessment for dryland environments: The Namaqualand Hardeveld bioregion of the Succulent Karoo biome as a case‐study

AbstractThere is growing consensus that land degradation assessments should occur at local to regional scales, as global assessments fail to capture the complexity of land degradation processes, and how they manifest in different social‐ecological contexts. We have tested a statistically rigorous method for regional land degradation assessment in drylands, using fuzzy classification theory and techniques, that results in the creation of a habitat condition archetype for the Namaqualand Hardeveld bioregion of the Succulent Karoo biome in South Africa. The methodology initially groups field data into classes based on known indicators of land degradation, before predicting observed field cover with 16 remote sensing variables, derived from both LANDSAT 8 and SENTINEL‐2A satellite data. Using fuzzy classification techniques, projections of field cover from the resulting model are combined with variables representing a potential change in cover to produce a map of the habitat condition of the bioregion. Approximately 17% of the bioregion had habitat condition values less than one standard deviation smaller than the mean and could therefore be considered degraded. To provide context, this map is presented with potential drivers of change for the bioregion. The map, and accompanying drivers of change, is ultimately presented in a Google Earth Engine app for easy interpretation and use.

Health assessment of wild speckled dwarf tortoises, CHERSOBIUS SIGNATUS

BackgroundIn free-ranging reptile populations, bacterial, fungal, viral and parasitic pathogens may affect hosts through impairment in movements, thermoregulation, reproduction, survival, and population dynamics. The speckled dwarf tortoise (Chersobius [Homopus] signatus) is a threatened species that is mostly restricted to the Succulent Karoo biome in South Africa, and little information on pathogens of this species is available yet. We derived baseline parameters for five males and five females that were captured to genetically enhance a conservation breeding program in Europe. Upon collection of the tortoises, ticks were removed and identified. Immediately upon arrival in Europe, ocular, nasal, oral and cloacal swabs were taken for viral, bacteriological and mycological examinations. Fecal samples were collected before and 1 month after fenbendazole treatment, and analyzed for parasites. A panel of PCR, aiming to detect herpesviruses, adenoviruses and iridoviruses, was carried out.ResultsSamples were negative for viruses, while bacteriological examination yielded detectable growth in 82.5% of the swabs with a mean load of 16 × 107 ± 61 × 108 colony forming units (CFU) per swab, representing 34 bacterial species. Cloacal and oral swabs yielded higher detectable growth loads than nasal and ocular swabs, but no differences between sexes were observed. Fungi and yeasts (mean load 5 × 103 ± 13 × 103 CFU/swab) were detected in 25% of the swabs. All pre-treatment fecal samples were positive for oxyurid eggs, ranging from 200 to 2400 eggs per gram of feces, whereas after the treatment a significantly reduced egg count (90–100% reduction) was found in seven out of 10 individuals. One remaining individual showed 29% reduction, and two others had increased egg counts. In five tortoises, Nycthocterus spp. and coccidian oocysts were also identified. Soft ticks were identified as Ornithodoros savignyi.ConclusionsOur baseline data from clinically healthy individuals will help future studies to interpret prevalences of microorganisms in speckled dwarf tortoise populations. The study population did not appear immediately threatened by current parasite presence.

A 14000 year multi-proxy alluvial record of ecotone changes in a Fynbos-Succulent Karoo transition in South Africa

To address long-standing questions concerning Southern Hemisphere climate dynamics and palaeoecological change in southern Africa, a Late Glacial-Holocene alluvial sediment sequence from the relatively dry interior year-round rainfall zone in South Africa was investigated. The study site borders the Fynbos biome and Succulent Karoo biome ecotone, and comprises a rare stratified sequence of sandy and organic-rich silt deposits, shown to span the last 14,000 years. A high resolution multi-proxy record of ecological change was derived using pollen, phytoliths and organic geochemical analyses. For the period 14–11 ka, significant valley aggradation occurred under relatively drier conditions, followed, during the early and middle Holocene, by alternating phases of humid and dry events with higher stream energy, slower accumulation or subtle seasonality changes. A transition from relatively humid to more arid conditions at 4–3 ka is identified and is consistent in timing with several interior year-round rainfall zone records. Results revealed alternations of fynbos and karroid elements and C3/C4 grasses throughout the last fourteen thousand years, but did not suggest large-scale biome shifts. The record joins a growing number of sites contributing to debate over the complex atmospheric-oceanic drivers of palaeoclimate in this region. These data broadly fit to the regional pattern for the southernmost interior of South Africa in showing alternating influences from the westerly winter rain systems in the early Holocene, with a greater contribution from subtropical summer rain system during the middle and later Holocene.

<strong><em>Crassula ×mortii</em> (Crassulaceae subfam. Crassuloideae), a new natural hybrid between<em> C. perforata</em> and <em>C. rubricaulis</em> from South Africa’s southern Cape</strong>

In terms of species-level diversity, the genus Crassula Linnaeus (1753: 282) is by far the most diverse in the Crassulaceae within the Flora of Southern Africa region [Namibia, Botswana, Eswatini (formerly Swaziland), Lesotho, South Africa] (Tölken 1977a, b, 1985). In this region diversity is highest in the Fynbos and Succulent Karoo Biomes, both of which straddle the southern Cape, an area represented in the Western and Eastern Cape provinces.

Othonna koos-bekkeri, a new succulent shrub from northern Namaqualand and southern Richtersveld, (N. Cape Province, South Africa)

Othonna koos-bekkeri is a new shrubby Othonna from the mountains of the western escarpment in the Northern Cape. It is immediately recognized by its ascending rod-like stems and lateral ascending spreading spur-shoots and sub-umbellate yellow flower heads, the latter flowering during autumn when the plants are leafless. In the past, it was often confused with Othonna arbuscula, a smaller species widespread in the Succulent Karoo Biome.

Implications of potential biome boundary shifts for small mammal assemblages in the arid zone of South Africa

AbstractDesertification deteriorates the landscape functionality of rangelands, affecting the resilience of biome boundaries and this has a cascading effect on vegetation and animal communities. This study aimed to assess landscape functionality along the biome boundary of two arid biomes and its relationship to small mammal assemblages. The study further aimed to provide a landscape perspective of the current desertification process and projected expansion of the Desert biome in South Africa. Three Desert biome, ecotone and Succulent Karoo biome sites were selected to assess landscape functionality and small mammal assemblages over a one‐year period. The difference in landscape functionality between the three areas was assessed to determine the resilience of the biome boundary to desertification. Our results showed that the vegetation of the ecotone had higher desert‐like affinities while the soils seemed resilient and remained closely related to the Succulent Karoo biome. High livestock grazing pressure, as evident in the pastoral rangeland, may further deteriorate vegetation parameters and expose the soil to erosion, thereby advancing desertification. During both winter and summer, small mammal surveys using live Sherman traps were conducted and over the total 3204 trapping nights, 119 small mammal captures were recorded from three species. Desmodillus auricularis, Elephantulus rupestris and Gerbillurus paeba all had significantly higher densities in the Succulent Karoo biome. Our study supports the view that G. paeba would be the only species able to thrive in the less diverse Desert biome. This might have implications for the ecosystem services provided by the other two small mammal species in the landscape. As the trajectory for projected desertification appears to be on track, concerted efforts in improving rangeland management are required to maintain landscape functionality and stabilise small mammal assemblages.

Fifteen-year resilience against further degradation of Succulent Karoo vegetation in South Africa

The Tankwa Karoo National Park (TKNP) is part of a renowned arid biome with unrivaled diversity in succulents. The park has been subject to anthropogenic pressures such as heavy grazing with climate change a recent threat. This study investigated changes in vegetation productivity between 2000 and 2014 across six vegetation types using rainfall and satellite data. The park is broadly divided into a plain at low altitude (316 m) receiving less rain and a wetter, higher terrain (1640 m). Long-term rainfall varied from 265 mm y-1 in the highland areas to 100 mm y-1 in the plains. There was a significant corresponding rise in NDVI from the low to the highlands (p < 0.001). Our analyses suggest that vegetation has stabilised since the park was proclaimed in 1984 because 81% of the area has remained uniform, on average, despite considerable variation on a vegetation type basis. Only 18% of the park had increasing productivity while just 2% experienced a decline. The patterns also suggest vegetation was principally controlled by rainfall, rather than a shift in land-use from rangeland to conservation. This implies that much of the presumably endemic degradation in the Succulent Karoo Biome is not evident in the Tankwa.