Fynbos Biome Research Articles

<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.

New macropterous leafhopper genera and species within the tribe Bonaspeiini from the Fynbos biome of South Africa (Insecta, Hemiptera, Auchenorrhyncha, Cicadellidae)

Two new genera of macropterous leafhoppers, tentatively included in the tribe BonaspeiiniZahniser and Dietrich (2013) from the Fynbos biome of south-western parts of South Africa, are described. These are Retevolatusgen. nov. with type species R. flexiverpussp. nov., R. semicurviverpussp. nov. and R. subspiniverpussp. nov. and Flavorubivolatusgen. nov. with type species F. glabriverpussp. nov. and F. tensiverpussp. nov. and F. curtiverpussp. nov. Collection records and distribution modelling confirmed that species of both genera occur within a confined region of south-western parts of South Africa.

A re-evaluation of Penicillium section Canescentia, including the description of five new species.

A survey of Penicillium in the fynbos biome from South Africa resulted in the isolation of 61 species of which 29 were found to be new. In this study we focus on Penicillium section Canescentia, providing a phylogenetic re-evaluation based on the analysis of partial beta-tubulin (BenA), calmodulin (CaM) and RNA polymerase II second largest subunit (RPB2) sequence data. Based on phylogenies we show that five fynbos species are new and several previously assigned synonyms of P. canescens and P. janczewskii should be considered as distinct species. As such, we provide descriptions for the five new species and introduce the new name P. elizabethiae for the illegitimate P. echinatum. We also update the accepted species list and synonymies of section Canescentia species and provide a review of extrolites produced by these species. Citation: Visagie CM, Frisvad JC, Houbraken J, et al. 2021. A re-evaluation of Penicillium section Canescentia, including the description of five new species. Persoonia 46: 163-187. https://doi.org/10.3767/persoonia.2021.46.06.

Germination success of habitat specialists from the Succulent Karoo and Renosterveld on different soil types

South African quartz fields in the Succulent Karoo and adjacent biomes are special habitats for a range of highly specialized dwarf succulents, many of which belong to the Aizoaceae. The soil chemistry of the quartz fields ranges from very acidic to slightly alkaline and from moderately to highly saline, and drives species turnover. The soil conditions are therefore critical for the vegetation composition. The aim of our study is to better understand the role of the regeneration niche of habitat specialists from different quartz-field habitats to inform conservation planning and ecological restoration. We tested germination responses to soil chemistry of 14 Aizoaceae species from quartz fields in the Succulent Karoo (Knersvlakte) and the Fynbos (Overberg) biome of South Africa. For each of the two sites we sampled species from two different quartz-field habitats. The seeds from 14 species were germinated under greenhouse conditions for 79 days on their home soils and on the natural soils of the three other habitat types as well as on salinized and acidified horticultural standard substrate and a standard substrate as control.Germination success in the control differed between the species from the two biomes. Of the seven species from the Knersvlakte, six species germinated rapidly, with 38–86% success. Only Dicrocaulon brevifolium germinated with merely 17% success. Of the seven species from Overberg only Gibbaeum hartmannianum germinated at a high percentage (83%). The other species germinated below 20% or not at all.Natural soils and manipulated substrates limited germination of all species to <20%. No seeds germinated on natural saline soils from the Knersvlakte until from day 46 to day 50, when an excess supply of rainwater diluted the ion content of the soil. The subsequent recovery of the seeds resulted in a germination percentage of 4–35% for seven species from different habitat types. Quartz fields provide a plant-adverse environment. Their soils contain a range of toxic ions at high concentrations. High volume and prolonged rainfall events that leach the soils temporarily seemed to be a requisite for successful germination.

Post-pollination barriers enable coexistence of pollinator-sharing ornithophilous Erica species.

Some evolutionary radiations produce a number of closely-related species that continue to coexist. In such plant systems, when pre-pollination barriers are weak, relatively strong post-pollination reproductive barriers are required to maintain species boundaries. Even when post-pollination barriers are in place, however, reproductive interference and pollinator dependence may strengthen selection for pre-pollination barriers. We assessed whether coexistence of species from the unusually speciose Erica genus in the fynbos biome, South Africa, is enabled through pre-pollination or post-pollination barriers. We also tested for reproductive interference and pollinator dependence. We investigated this in natural populations of three bird-pollinated Erica species (Erica plukenetii, E. curviflora and E. coccinea), which form part of a large guild of congeneric species that co-flower and share a single pollinator species (Orange-breasted Sunbird Anthobaphes violacea). At least two of the three pre-pollination barriers assessed (distribution ranges, flowering phenology and flower morphology) were weak in each species pair. Hand-pollination experiments revealed that seed set from heterospecific pollination (average 8%) was significantly lower than seed set from outcross pollination (average 50%), supporting the hypothesis that species boundaries are maintained through post-pollination barriers. Reproductive interference, assessed in one population by applying outcross pollen three hours after applying heterospecific pollen, significantly reduced seed set compared to outcross pollen alone. This may drive selection for traits that enhance pre-pollination barriers, particularly given that two of the three species were self-sterile, and therefore pollinator dependent. This study suggests that post-pollination reproductive barriers could facilitate the coexistence of congeneric species, in a recent radiation with weak pre-pollination reproductive barriers.

Seasonal and Agricultural Response of Acidobacteria Present in Two Fynbos Rhizosphere Soils

The Acidobacteria is one of the most abundant phyla in most soil types. Fynbos plants are endemic to South Africa, and these soils provide the ideal habitat for Acidobacteria, because of its low pH and oligotrophic properties. However, little is known about their distribution in the fynbos biome and the impact of cultivation of plants on Acidobacterial diversity. Therefore, the aim of this study was to determine the effect of seasonal changes and cultivation on the relative abundance and diversity of Acidobacteria associated with Aspalathus linearis (rooibos) and Cyclopia spp. (honeybush). This study was based on rhizosphere soil. A total of 32 and 31 operational taxonomic units (OTUs) were identified for honeybush and rooibos, respectively. The majority of these were classified as representatives of subdivisions 1, 2, 3, and 10. Significant differences in community compositions were observed between seasons for both honeybush and rooibos, as well as between the cultivated and uncultivated honeybush. Acidobacteria had a significantly positive correlation with pH, C, Ca2+, and P. In this study, we have shown the effect of seasonal changes, in summer and winter, and cultivation farming on the relative abundance and diversity of Acidobacteria present in the soil of rooibos and honeybush.

Small ratios of anabolic to catabolic soil nutrients constrain invasive alien trees in the Western Cape, South Africa

Invasion by invasive alien trees is a major threat to the biodiversity of the fynbos biome in South Africa. The environmental factors influencing the intensity of invasion are, however, largely unknown. In particular, the effects of soil nutrients on the invasion of alien trees in the fynbos biome have not been investigated. The Catabolic Theory predicts that trees will be more competitive than shrubs and herbaceous plants where anabolic nutrients (e.g. Mg, Mn and B) are comparatively more abundant than catabolic nutrients (e.g. P, Cu and Zn). We tested this theory at seven study sites by comparing soil nutrient concentrations in non-invaded and adjacent invaded sub-sites. Soil samples from 275 plots across 17 sub-sites were analysed for pH, Na, Mg, K, Ca, P, S, C, B, Mn, Cu and Zn. The results corroborated the Catabolic Theory. An index of anabolic to catabolic nutrients was greater in all ten sub-sites invaded by invasive alien trees than in sub-sites without invasion. Nutrients strongly related to tree invasion included B and P. As per the Catabolic Theory, poverty of B at certain sites is likely to constrain anabolism and consequently tree establishment. Some non-invaded sites had B concentrations of 0.02 mg kg−1, which is an order of magnitude less than critical deficiency thresholds in an agronomic context. By contrast, richness of P (as a result of prior fertilization) in fallow agricultural fields would, as per the Catabolic Theory, promote catabolism and the competitive strength of shrubs and/or herbaceous plants relative to trees. Practical implications of these findings include: 1) the mapping of soil properties such as B and P to reveal the inherent propensity of landscapes in the Western Cape to be invaded by trees; and 2) the application of B-binding substances such as illite and vermiculite to constrain invasion of trees in fynbos.

Mountains of the Mist: A first plant checklist for the Bvumba Mountains, Manica Highlands (Zimbabwe-Mozambique).

The first comprehensive plant checklist for the Bvumba massif, situated in the Manica Highlands along the Zimbabwe-Mozambique border, is presented. Although covering only 276 km2, the flora is rich with 1250 taxa (1127 native taxa and 123 naturalised introductions). There is a high proportion of Orchidaceae and Pteridophyta, with both groups showing a higher richness than for adjacent montane areas, which may be due to the massif’s relatively high moisture levels as a result of frequent cloud cover. However, in contrast to other mesic montane regions in southern Africa, there are relatively few near-endemic or range-restricted taxa: there is only one local endemic, Aeranthes africana, an epiphytic forest orchid. This is likely to be an effect of the massif having limited natural grassland compared to forest, the former being the most endemic-rich habitat in southern African mountains outside of the Fynbos Biome. Six other near-endemic taxa with limited distribution in this portion of the Manica Highlands are highlighted. The high number of invasive species is probably a result of diverse human activities in the area. The main species of concern are Acacia melanoxylon, a tree that is invading grassland and previously cultivated land, the forest herb Hedychium gardnerianum which in places is transforming forest understorey with an adverse effect on some forest birds, and the woody herb Vernonanthura polyanthes which invades cleared forest areas after fire. Future botanical work in the massif should focus on a more detailed exploration of the poorly known Serra Vumba on the Mozambican side and on the drier western slopes. This will allow for a more detailed analysis of patterns of endemism across the Manica Highlands.

Description of the female of Xiphodontus endroedyi Bartolozzi, 2005 (Coleoptera: Lucanidae)

The female of Xiphodontus endroedyi Bartolozzi, 2005 is described for the first time. The new locality record for this species shows that it actually has a wide distribution range across the Cape Floral Region, in the Fynbos Biome. Both larvae and adults were found boring into dead wood at the base of senescent trunks of a variety of Proteaceae species, including the alien invasive Hakea sericea.

Population structure and survival of the critically endangered cycad Encephalartos latifrons in South Africa

This study investigates the population structure and life history traits of the Critically Endangered cycad, Encephalartos latifrons. Populations of E. latifrons have been considered functionally extinct because no natural recruitment has been observed in the wild for almost 30 years. The discovery of a previously undocumented population of E. latifrons has made it possible to build on previous research into the life history and regeneration capabilities of the species. This new population was censused annually over 5 years; between 2013 and 2017. Population characteristics of this ‘new’ population were compared to earlier studies in 2010 of a well-known and intensively managed population. Results of the censuses show that the newly discovered population of E. latifrons appears to be increasing under current environmental conditions through natural recruitment. The discovery of a ‘new’ E. latifrons population has uncovered many more questions and further research is needed. Information on the life history of E. latifrons, particularly its response to fire, should be used to inform conservation management decisions at a time where the impact of climate change is predicted to have a major influence in the Fynbos Biome.

Both Alpha- and Beta-Rhizobia Occupy the Root Nodules of Vachellia karroo in South Africa.

Vachellia karroo (formerly Acacia karroo) is a wide-spread legume species indigenous to southern Africa. Little is known regarding the identity or diversity of rhizobia that associate with this plant in its native range in South Africa. The aims of this study were therefore: (i) to gather a collection of rhizobia associated with V. karroo from a wide range of geographic locations and biomes; (ii) to identify the isolates and infer their evolutionary relationships with known rhizobia; (iii) to confirm their nodulation abilities by using them in inoculation assays to induce nodules under glasshouse conditions. To achieve these aims, soil samples were collected from 28 locations in seven biomes throughout South Africa, which were then used to grow V. karroo seedlings under nitrogen-free conditions. The resulting 88 bacterial isolates were identified to genus-level using 16S rRNA sequence analysis and to putative species-level using recA-based phylogenetic analyses. Our results showed that the rhizobial isolates represented members of several genera of Alphaproteobacteria (Bradyrhizobium, Ensifer, Mesorhizobium, and Rhizobium), as well as Paraburkholderia from the Betaproteobacteria. Our study therefore greatly increases the known number of Paraburkholderia isolates which can associate with this southern African mimosoid host. We also show for the first time that members of this genus can associate with legumes, not only in the Fynbos biome, but also in the Albany Thicket and Succulent Karoo biomes. Twenty-six putative species were delineated among the 88 isolates, many of which appeared to be new to Science with other likely being conspecific or closely related to E. alkalisoli, M. abyssinicae, M. shonense, and P. tropica. We encountered only a single isolate of Bradyrhizobium, which is in contrast to the dominant association of this genus with Australian Acacia. V. karroo also associates with diverse genera in the Grassland biome where it is quite invasive and involved in bush encroachment. Our findings therefore suggest that V. karroo is a promiscuous host capable of forming effective nodules with both alpha- and beta-rhizobia, which could be a driving force behind the ecological success of this tree species.

Feeding and Mobility Traits Influence Grasshopper Vulnerability to Agricultural Production in the Cape Floristic Region Biodiversity Hotspot.

To be able to foretell which species will be at risk of extinction from possible expansion of agriculture into natural areas, we need to determine how land use affects animal groups especially insects with different life history traits. Intuitively, we can predict that the proportion of specialist versus generalist grasshoppers and widespread versus localised species can be an indicator of change in vegetation patterns in a landscape. As a result, the study examined the relationship between the extent of range distribution and mobility of grasshoppers and land-use type in the Cape Floristic Region (CFR) biodiversity hotspot. It aimed at examining grasshopper assemblage composition in association with different land uses. We specifically related the number and type of sites occupied by grasshopper species to their mobility and distribution type to find out which characters improve species survival under highly modified habitats. Grasshopper assemblages were dominated by highly mobile generalists that tolerated transformed landscapes, and mostly geographically widespread. This contrasts with the low- to medium-mobile, range-restricted specialists, which make up close to 30% of the total collection, with a lower tolerance for anthropogenically modified landscapes in the CFR. This study also reveal that the fynbos biome is an important habitat for low-mobility and range-restricted species, and hence require conscious conservation efforts to conserve such species to prevent possible future biotic erosion and homogenisation in this hotspot. This result can be used to assess the possible extent of biotic erosion or otherwise in order to recommend better conservation efforts in the CFR.

Potential insect vectors and alternative host plants of phytoplasmas inthe Fynbos and Succulent Karoo biomes in South Africa

Potential insect vectors and alternative host plants of phytoplasmas inthe Fynbos and Succulent Karoo biomes in South Africa

Rethinking catastrophe? Historical trajectories and modelled future vegetation change in southern Africa

Abstract Most projections of climate change for southern Africa describe a hotter and drier future with catastrophic consequences for the environment and socio-ecological sustainability of the region. This study investigated whether evidence of the projections for the climate and vegetation of the subcontinent is already evident. Analysis of the climate record indicate that the historical trend of increasing temperature is consistent with future projections for the region. Rainfall, however, apparently has not changed significantly. Results from analysis of 1321 repeat historical photographs indicate broad trends in vegetation trajectories in the major biomes of southern Africa. The Savanna biome has experienced a rapid increase in woody plant at rates un-anticipated by the models. Contrary to early projections for the Succulent Karoo biome, biomass and cover have increased, largely in response to changes in land-use practices. Cover in the fire-adapted Fynbos biome has remained stable or increased over time with unanticipated expansion of forest species, particularly in localities protected from fire for long periods. The shrub-dominated Nama-karoo biome has increased in grass cover. Rather than contracting, as suggested in the early models, the Grassland biome has apparently expanded westwards into former Nama-karoo biome sites. The Savanna biome has experienced a rapid increase in woody plants at rates not anticipated by the models. The broad trends in historical trajectories illustrate how land-use management has influenced vegetation change in the past. They also provide a useful context for evaluating future changes and developing mitigation strategies for some of the worst impacts of climate change in the future.

Litter decomposition variation across a degradation gradient and two seasons in a critically endangered vegetation type within the Fynbos biome, South Africa

Litter decomposition is an ecosystem function essential for nutrient cycling; however until very recently it was considered of minor importance within the fire-prone Fynbos Biome. To investigate decomposition rate and litter nutrient dynamics, litterbags containing materials from three plant species from different functional types were placed in sites across a degradation gradient and over two seasons. Litterbags were removed after three and six months for both seasons to determine decomposition rates and change in nutrient concentration. Decomposition varied greatly among the species and was strongly correlated to initial nutrient values of the litter. The most nutrient rich litter type, the alien herbaceous Medicago spp., lost 65% of its original mass after six months while the most nutrient poor, the indigenous grass Pentameris eriostoma, lost 18%. Litter from Dicerothamnus rhinocerotis, an indigenous shrub, lost 27% of its original mass. For all litter types, the majority of the loss occurred during the first three months of the experiment. Season was found to significantly affect litter decomposition; however the exact mechanism behind this is unclear. Degradation level, at least defined by the metrics of this study, did not significantly affect litter decomposition rate. The faster decomposition rate shown in Medicago spp. suggests that in degraded areas where significant proportions of the species invade, nutrient cycling will be accelerated in comparison to pristine land; however broadening the species of study to include additional plant functional types, such as indigenous annuals, would help give insight into this hypothesis. This study affirms the notion that litter decomposition is an important ecosystem function within the Fynbos Biome with litter type acting as a strong controlling variable.

Local and landscape level variables influence butterfly diversity in critically endangered South African renosterveld

Severe losses in biodiversity hotspots reduce global insect diversity. Renosterveld is a critically endangered and biologically diverse ecosystem occurring only in the fynbos biome of the Cape Floristic Region (CFR), a recognized global biodiversity hotspot. Following agricultural intensification, less than 5% natural renosterveld vegetation remains in the Swartland of South Africa’s Western Cape. Remaining renosterveld is highly fragmented and confined to land less suited to agriculture, including steep slopes and rocky outcrops. These fragments vary in their environmental conditions at the local (e.g. microhabitat, floral diversity and density) and the landscape (e.g. patch size, habitat connectivity and surrounding crop cover) level. The influence of these environmental variables on butterfly diversity at a landscape scale in the CFR is not fully understood. We selected 32 sites across the Swartland and surveyed for butterflies to determine the effect of environmental variables on butterfly diversity, specifically butterfly species richness, abundance and composition. Overall, we found 2861 individuals of 27 species. Our findings suggest that crop cover in the surrounding landscape affects butterfly diversity at a small landscape scale (< 500 m radius) in the CFR. Flower species richness and microhabitat type impact species richness and abundance. Patch size is a key predictor of species diversity particularly for endemics and site quality may influence species composition. All renosterveld patches regardless of size and site quality can be considered valuable for butterflies in this highly fragmented landscape.

A Holocene “Frozen Accident”: Sediments of Extreme Paleofloods and Fires in the Bedrock-Confined Upper Huis River, Western Cape, South Africa

Wildfires and flooding events are common and are forceful intrinsic controls over landscape evolution, biodiversity, and preserved sediment architecture in dryland environments. Charcoal-bearing Holocene flood sediments of the upper Huis River provide a rare perspective on the powerful and episodic sedimentary processes in a bedrock-confined fluvial setting in the tectonically stable SW Cape Fold Belt in South Africa. The sediments described in this paper are associated with high-magnitude, debris-flow-dominated paleofloods, and their charcoal content is linked to a series of radiocarbon-dated Holocene paleofires that occurred from ∼ 2165 ± 37 BP to ∼ 653 ± 35 BP. The five sedimentary facies associations are documented as products of: a) noncohesive pseudoplastic debris flows; b) transitional, high-matrix-strength debris flows with heterogeneous fluid content and flow behavior; c) low-cohesion debris flows; d) hyperconcentrated flows; and e) fluvial channel flow in the upper Huis River. The last is interpreted mainly from massive, subrounded to subangular boulder bars, which provide key evidence for the dramatic scouring of the upper Huis valley. The paleofloods, which not only filled the valley with debris-flow sediments up to 12 m thick, but also subsequently flushed it out nearly to the bedrock, had estimated extreme discharges of few thousands of m3/s. In summary, the upper Huis River sediments are exceptional because they preserve the geological record of recurring fires, and at least three extreme paleofloods (i.e., massive sedimentation events) over a period of ∼ 1500 years in an area typified by the fire-prone and fire-dependent Fynbos Biome. Furthermore, this study provides insights into what the gaps in the commonly fragmented bedrock-confined alluvial stratigraphic record would be like, should there be “more record than gap.”

Hottentot Buttonquail Turnix hottentottus: Endangered or just overlooked?

SummaryThere is remarkably little documented information in the scientific literature on any of the 18 species of buttonquail as they are very difficult to observe in the wild. This lack of information has hampered informed conservation decision making. We undertook the first biome-wide survey for the fynbos endemic Hottentot Buttonquail Turnix hottentottus, using flush transect surveys covering 275 km. We used location data for sightings as well as from records reported by the bird-watching community and modelled distribution using MaxEnt. Encounters were restricted to the fynbos biome, and the top contributors to our prediction of suitable habitat were habitat transformation, slope and time since fire. We obtained a density estimate of 0.032 individuals per hectare which, across an estimated median range of 27,855 km2, provides a population estimate of 89,136 individuals. Given the extent of the range and the population estimate we suggest the IUCN Red List status could be ‘Vulnerable’, rather than ‘Endangered’. Agricultural and alien-vegetation encroachment means that the future of the species is certainly under threat and further studies are needed to inform conservation management.

Horizontal gene transfer among rhizobia of the Core Cape Subregion of southern Africa

This study determined the extent of horizontal gene transfer among rhizobial genera in the Core Cape Subregion (CCR) of South Africa and reconstructed the ancestral symbionts of the legumes. Phylogenies of two chromosomal genes (16S rRNA and recA) and one nodulation gene (nodA) of rhizobia, isolated from diverse legumes in the CCR, were reconstructed using Bayesian and Maximum Likelihood techniques. A cophylogenetic analysis was used to test for congruence between the chromosomal and the nodA phylogenies. Five genera of rhizobia (Bradyrhizobium, Burkholderia, Mesorhizobium, Rhizobium and Sinorhizobium) were studied. A phylogeny of the legumes was reconstructed from matK and rbcL DNA sequences and it was used to reconstruct their ancestral rhizobia, using Bayesian methods. The chromosomal phylogeny of the rhizobia was mostly incongruent with that of nodA, indicating potential horizontal inheritance of the latter. The nodA genes of Burkholderia, Mesorhizobium and Rhizobium had different evolutionary histories from their counterparts in other parts of the globe. Burkholderia was reconstructed as the ancestral symbionts of the CCR legumes. Evidence of co-diversification between the legumes and their symbionts was observed and this highlights a potential role of the legume-rhizobia interaction to the high diversity of legumes in the CCR. Finally, the availability of compatible rhizobia and their competitive ability are discussed as possible drivers for the lack of shared legumes between the Fynbos biome and the Kwongan of Australia.

Microsatellite marker applications in Cyclopia (Fabaceae) species

Cyclopia species, from which honeybush tea is made, are endemic to the Fynbos Biome of South Africa. Despite its commercial importance, no molecular resources are available to characterise this genus. The polyploid nature of the genus furthermore complicates the use of molecular markers. The Agricultural Research Council (ARC) maintains a field gene bank for several species. A set of six microsatellite markers was developed from C. subternata. These were used to characterise the accessions, thereby facilitating the management of the gene bank, such as keeping track of clones for seed orchards or commercial release and the avoidance of duplicates. In addition, the genetic diversity of three C. subternata wild populations was investigated and compared to the accessions. The C. subternata accessions were representative of the wild samples, excluding those from the genetically distinct Haarlem population. The microsatellite markers developed in this study can be used in the characterisation of wild populations of other species that could be included in the field gene bank and to detect, for example, gene flow between cultivated material and wild populations of Cyclopia. Further conservation strategies include the monitoring of wild harvesting as well as the inclusion of samples from the Haarlem population into the gene bank for the conservation of this genetically distinct population.