Insect diversity in the Cape Floristic Region

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.     

Root trait variation along water gradients in the Cape Floristic Region

Questions

Roots are responsible for essential plant functions including water uptake. However, the extent to which root traits (size and structure) determine plant presence in water-limited environments is still poorly understood. Here we investigated how root traits vary across water availability gradients within a dry South African biome.

Location

South Africa.

Methods

We measured six below-ground (root) and eight above-ground (leaf + stem) traits of 124 individuals of nine dominant woody shrub species from wetter and drier sites (600–700 vs 250–300 mm annual precipitation) in the Fynbos biome of the Cape Floristic Region. Within sites, we sampled from recently burnt and unburnt/more mature vegetation and at three locations along topographical gradients.

Results

Drier regions showed greater maximum rooting depth, length, root dry matter content and root to shoot ratio. These trait patterns were consistent at an intraspecific level, along locally drier topographical locations and in post-fire environments. Roots accounted for significant whole-plant trait variation. Additionally, in drier conditions, we found increased root allocation deviating from expected global allometric relationships. Our study also demonstrates that the combination of fire and drought in the driest locations results in poor above-ground vegetation recovery in terms of plant size, cover and individual counts with only resprouters persisting.

Conclusions

Our research suggests that root investment in Fynbos shrubs will likely be key for coping with a drier and warmer future and should be a focus of more research for dryland biomes.     

Ants, altitude and change in the northern Cape Floristic Region

Aim Climate‐modelling exercises have demonstrated that the Cape Floristic Region is highly sensitive to climate change and will apparently lose much of its northern limits over the next few decades. Because there is little monitoring of diversity in this area, ant assemblage structure was investigated within the main vegetation types in the Greater Cederberg Biodiversity Corridor. In particular, we sought to determine how ant assemblage structure differs between the main vegetation types, how restricted ants – and in particular the major myrmecochores – are to the major vegetation types, and which environmental variables might underlie differences in the ant assemblages and in the specificity of species to particular areas. Location Northern Cape Floristic Region, Western Cape, South Africa. Methods Sampling was undertaken during October 2002 and March 2003 across an altitudinal gradient ranging from sea level (Lambert's Bay) to c. 2000 m a.s.l. (Sneeukop, Cederberg) and down again to 500 m a.s.l. (Wupperthal) in the Western Cape, South Africa. Pitfall traps were used to sample ants at 17 altitudinal bands, stretching over three vegetation types (Strandveld, Mountain Fynbos and Succulent Karoo). Biotic and abiotic environmental variables were collected at each sampling site. Generalized linear models were used to determine the relationships between species richness, density, abundance and the abundance of the major myrmecochores, and the environmental variables. Redundancy analysis was used to determine the relationship between ant assemblage structure and the environmental variables. The Indicator Value Method was used to identify characteristic ant species for each vegetation type and altitudinal site. Results Temperature explained significant proportions of the variation in species density and abundance, and, together with area and several vegetation variables, contributed significantly to the separation of the assemblages in the major vegetation types and biomes. Four major myrmecochores were identified [Anoplolepis sp. (cf. custodiens), Anoplolepis sp. (cf. steinergroeveri), Camponotus niveosetosus, Tetramorium quadrispinosum]. The abundances of the two Anoplolepis species were related to vegetation variables, while the abundance of the other two species showed opposite relationships with temperature variables. Fourteen ant species were characteristic of certain vegetation types and altitudes. Several of these species contributed to the differences between the assemblages. Main conclusions There are likely to be substantial and complex changes to ant assemblages as climates change in the northern Cape Floristic Region. Moreover, the importance of ants for ecosystem functioning suggests that these responses are not only likely to be a response solely to vegetation changes, but might also precipitate vegetation changes. The changes that are predicted to take place in the next 50 years in the Cape Floristic Region could be substantially exacerbated by such synergistic effects, which have major implications for long‐term conservation plans. Ongoing monitoring of this transect will reveal the nature and pace of the change as it unfolds.     

Fungal radiation in the Cape Floristic Region: an analysis based on Gondwanamyces and Ophiostoma

The Cape Floristic Region (CFR) displays high levels of plant diversity and endemism, and has received focused botanical systematic attention. In contrast, fungal diversity patterns and co-evolutionary processes in this region have barely been investigated. Here we reconstruct molecular phylogenies using the ITS and beta-tubulin gene regions of the ophiostomatoid fungi Gondwanamyces and Ophiostoma associated with southern African Protea species. Results indicate that they evolved in close association with Protea. In contrast to Protea, Ophiostoma species migrated to the CFR from tropical and subtropical Africa, where they underwent subsequent radiation. In both Gondwanamyces and Ophiostoma vector arthropods probably facilitated long-distance migration and shorter-distance dispersal. Although ecological parameters shaped most associations between ophiostomatoid fungi and Protea, there is congruence between fungal-host-associations and the systematic classification of Protea. These results confirm that the entire biotic environment must be considered in order to understand diversity and evolution in the CFR as a whole.     

Coexistence theory in the Cape Floristic Region: revisiting an example of leaf niches in the Proteaceae

Competition in plant communities is often a contentious issue because the mechanisms of competitive interactions are not obvious. We sought evidence that Proteaceae communities are competing along two leaf niche axes as observed in a previous study. Two functional characters, leaf size and leaf shape were measured on numerous individuals per species per plot of six communities from two different regions. Patterns of overdispersion along these leaf trait axes between species were observed, similar to the earlier study. The observed results were compared with the patterns expected under a null model using standard and novel indices to test the significance of trait dispersion between species within a plot. Competition and niche differentiation in the observed plots were not supported as the observed trait overlaps were not significantly different from the null expectation. Our results do not support the theory that Proteaceae communities compete along the two proposed functional leaf traits.     

Influence of fire on critically endangered Swartland Shale Renosterveld in the Cape Floristic Region

Questions

The degree to which renosterveld shrublands are fire‐dependent is currently unclear. To address this issue, the following questions were asked: (1) does smoke stimulate germination of soil‐stored seeds in renosterveld; (2) does recently‐burned renosterveld display changed composition and higher diversity than unburned vegetation; and (3) how do the species compositions of renosterveld soil seed banks and standing vegetation compare?

Location

Swartland, Cape Floristic Region, South Africa.

Methods

Soil seed bank samples from a north‐ and south‐facing slope were smoke‐treated and germinated to test for smoke‐stimulated germination. Burned standing vegetation was surveyed 16 months post‐fire, as was unburned vegetation on the same slopes. Seed bank species richness and density were compared between smoke‐treated and untreated samples within and between slopes. Burned and unburned standing vegetation were compared within and between slopes in terms of species richness, abundance and aerial cover. Compositional similarity of the seed banks and standing vegetation was assessed.

Results

Seed banks were dominated by annuals and graminoids. Smoke treatment had no effect, except for driving significantly higher species richness and seedling density in south‐facing slope perennial shrubs. Species richness and seedling density were significantly higher in seed banks on the south‐facing slope compared to the north‐facing slope. Burned standing vegetation exhibited significantly higher diversity than unburned vegetation. Annuals and graminoids displayed significantly higher species richness and aerial cover in burned renosterveld. The north‐facing slope contained less than half the number of species/m² compared to the south‐facing slope. The seed banks and standing vegetation showed low to intermediate similarity (Sørensen = 31%–53%), but grouped close together on an NMDS plot, suggesting intermediate similarity overall.

Conclusions

Elevated germination of perennial shrubs in smoke‐treated seed bank samples and increased diversity of post‐fire standing vegetation suggest the renosterveld in this study shows elements of a fire‐driven system. Certain species only recruited in burned sites, suggesting fire‐stimulated germination. Aspect had a major influence on plant community composition, with the mesic south‐facing slope being more diverse than the xeric north‐facing slope. The similarity between the seed banks and standing vegetation was higher than previously shown for renosterveld, and appears to be higher than for fynbos.     

Dated Plant Phylogenies Resolve Neogene Climate and Landscape Evolution in the Cape Floristic Region

In the context of molecularly-dated phylogenies, inferences informed by ancestral habitat reconstruction can yield valuable insights into the origins of biomes, palaeoenvironments and landforms. In this paper, we use dated phylogenies of 12 plant clades from the Cape Floristic Region (CFR) in southern Africa to test hypotheses of Neogene climatic and geomorphic evolution. Our combined dataset for the CFR strengthens and refines previous palaeoenvironmental reconstructions based on a sparse, mostly offshore fossil record. Our reconstructions show remarkable consistency across all 12 clades with regard to both the types of environments identified as ancestral, and the timing of shifts to alternative conditions. They reveal that Early Miocene land surfaces of the CFR were wetter than at present and were dominated by quartzitic substrata. These conditions continue to characterize the higher-elevation settings of the Cape Fold Belt, where they have fostered the persistence of ancient fynbos lineages. The Middle Miocene (13–17 Ma) saw the development of perennial to weakly-seasonal arid conditions, with the strongly seasonal rainfall regime of the west coast arising ~6.5–8 Ma. Although the Late Miocene may have seen some exposure of the underlying shale substrata, the present-day substrate diversity of the CFR lowlands was shaped by Pliocene-Pleistocene events. Particularly important was renewed erosion, following the post-African II uplift episode, and the reworking of sediments on the coastal platform as a consequence of marine transgressions and tectonic uplift. These changes facilitated adaptive radiations in some, but not all, lineages studied.     

Developmental Plasticity of the Prospective Dermatome and the Prospective Sclerotome Region of an Avian Somite

The ventro-medial wall of a somite gives rise to the sclerotome and then to cartilaginous axial skeleton, while the dorso-lateral wall differentiates into the dermomyotome to form dermal mesenchyme and muscle. Although previous studies suggested pluri-potency of somite cell differentiation, apparent pluri-potency may be the result of migration of predetermined cells. To investigate whether the developmental fate of any region is determined, I isolated fragments of a region of a quail somite and transplanted them into chick embryos. When a fragment of the ventral wall of a quail somite, the prospective sclerotome, was transplanted into a chick embryo between the ectoderm and a newly formed somite, the transplanted quail cells were shown to form myotome and mesenchyme in 4-day chimera embryos and to form muscle and dermal tissue in 9-day chimeras. On the other hand, when a fragment of the dorsal wall of a quail somite, the prospective dermomyotome, was transplanted into a chick embryo between the neural tube and a newly formed somite, the graft gave rise to mesenchyme around the neural tube and notochord and then to vertebral cartilage. Thus the developmental fate of a region of a somite was shown not to be determined at the time of somite segmentation, confirming previous observations.     

Montane Refugia for Endemic and Red Listed Dragonflies in the Cape Floristic Region Biodiversity Hotspot

One of the features of many endemic organisms is that they are highly spatially restricted, and habitat specialists. The Kogelberg Biosphere Reserve (KBR) is a major centre of plant endemism within a global hotspot, the Cape Floristic Region (CFR). Dragonflies in this botanical hotspot have a range of habitat specialization from narrow-range specialists to widespread generalists, with an unusually strong bias towards the specialists. A huge 53% of dragonfly individuals and 26% of taxa recorded are national endemics, and three species are Red Listed. Thus, a group of predatory insects, which are largely not dependent on plant composition, mirrors the level of habitat specialization and restricted distributions of the plants at the spatial scale of the whole reserve. Although some studies caution the use of one taxon as a surrogate for another, the results here show that at the reserve scale in this global hotspot there can be remarkable concordance, suggesting further studies on other taxa should be carried out to determine the full extent of taxonomic concordance in this irreplaceable area.     

Surface-active arthropods in organic vineyards,integrated vineyards and natural habitat in the Cape Floristic Region

The Cape Floristic Region (CFR), South Africa, is a biodiversity hotspot challenged by intensive wine production. Innovative approaches are being explored to optimize wine production without compromising biodiversity. As organic farming enhances biodiversity conservation in many other regions, the aim here was to assess the potential of organic vineyard management for conserving CFR soil surface arthropod diversity. Pitfall traps were used to sample arthropods in three study areas, each of which included an organic vineyard, an integrated vineyard and a natural vegetation reference habitat. Overall arthropod morphospecies richness was highest in natural sites, followed by organic vineyards and then integrated vineyards. The same trend was seen for predators, saprophages and phytophages. The ability of organic vineyards to sustain more morphospecies than integrated vineyards were partially due to higher non-crop vegetation complexity and less intense management in the organic vineyards. Arthropod assemblages were similar in organic and integrated vineyards, while both land-uses differed greatly from natural sites. Variation among natural vegetation assemblages in different study areas was also much greater than among assemblages of cultivated sites. Organic vineyard management has the potential to make an important contribution to arthropod conservation in the CFR at the field scale. However, at the landscape scale, natural habitat supports a much wider variety of morphospecies, and the preservation of natural fragments in the vineyard landscape may be the most effective measure to increase biodiversity in the winelands.     

Evolutionary History of Lagomorphs in Response to Global Environmental Change

Although species within Lagomorpha are derived from a common ancestor, the distribution range and body size of its two extant groups, ochotonids and leporids, are quite differentiated. It is unclear what has driven their disparate evolutionary history. In this study, we compile and update all fossil records of Lagomorpha for the first time, to trace the evolutionary processes and infer their evolutionary history using mitochondrial genes, body length and distribution of extant species. We also compare the forage selection of extant species, which offers an insight into their future prospects. The earliest lagomorphs originated in Asia and later diversified in different continents. Within ochotonids, more than 20 genera occupied the period from the early Miocene to middle Miocene, whereas most of them became extinct during the transition from the Miocene to Pliocene. The peak diversity of the leporids occurred during the Miocene to Pliocene transition, while their diversity dramatically decreased in the late Quaternary. Mantel tests identified a positive correlation between body length and phylogenetic distance of lagomorphs. The body length of extant ochotonids shows a normal distribution, while the body length of extant leporids displays a non-normal pattern. We also find that the forage selection of extant pikas features a strong preference for C₃ plants, while for the diet of leporids, more than 16% of plant species are identified as C₄ (31% species are from Poaceae). The ability of several leporid species to consume C₄ plants is likely to result in their size increase and range expansion, most notably in Lepus. Expansion of C₄ plants in the late Miocene, the so-called ‘nature’s green revolution’, induced by global environmental change, is suggested to be one of the major ‘ecological opportunities’, which probably drove large-scale extinction and range contraction of ochotonids, but inversely promoted diversification and range expansion of leporids.     

Potential impact of viticulture expansion on habitat types in the Cape Floristic Region, South Africa

The wine industry in the Western Cape, South Africa has expanded over the past decade, particularly since the lifting of trade sanctions in 1992. Wine grapes are cultivated on fertile soils upon which threatened biodiversity habitat units of the Cape Floristic Region occur naturally. There is a concern as to whether further expansion of the wine industry, which would benefit the economy through increased foreign exchange, would encroach on the little remaining vegetation in vineyard-producing areas. Predictive land use modeling using logistic regression techniques was applied to determine suitable areas for vineyard cultivation according to climatic, topographic, and soil/geology variables. Of the most threatened habitats, 14849 hectares are particularly suitable for vineyards. Breede fynbos/renosterveld mosaic was the habitat most likely to be converted, and was considered 89.3% irreplaceable to current conservation goals. Also vulnerable are Ashton inland renosterveld and Boland coast renosterveld, the latter being 100% irreplaceable. Although the high rate in vine replanting suggests that the need for untransformed land will not be great immediately, an economic analysis showed that protection of these areas against future ploughing will be vital if targets of adequately representing each habitat in the Cape Floristic Region are to be met. Land use change modeling, especially if done in a spatially explicit and integrated manner with expert input, was shown to be an important technique for the extrapolation of historical patterns to understand the forces that shape landscapes, allowing for the assessment of management alternatives, and testing our understanding of key processes in land use changes that effect conservation planning.     

Restoration of invaded Cape Floristic Region riparian systems leads to a recovery in foliage-active arthropod alpha- and beta-diversity

The Cape Floristic Region of South Africa is a global biodiversity hotspot threatened by invasive alien plants (IAPs). We assessed the effect of plant invasions, and their subsequent clearing, on riparian arthropod diversity. Foliage-active arthropod communities were collected from two native and one invasive alien tree species. Alpha- and beta-diversity of their associated arthropod communities were compared between near pristine, Acacia-invaded and restored sites. Arthropod alpha-diversity at near pristine sites was higher than at restored sites, and was lowest at invaded sites. This was true for most arthropod taxonomic groups associated with all native tree species and suggests a general trend towards recovery in arthropod alpha-diversity after IAP removal. Overall, arthropod species turnover among sites was significantly influenced by plant invasions with communities at near pristine sites having higher turnover than those at restored and invaded sites. This pattern was not evident at the level of individual tree species. Although arthropod community composition was significantly influenced by plant invasions, only a few significant differences in arthropod community composition could be detected between restored and near pristine sites for all tree species and arthropod taxonomic groups. Assemblage composition on each tree species generally differed between sites with similar degrees of plant invasion indicating a strong turnover of arthropod communities across the landscape. Results further suggest that both arthropod alpha- and beta-diversity can recover after IAP removal, given sufficient time, but catchment signatures must be acknowledged when monitoring restoration recovery.     

Floristic diversity in the Cape Flora of South Africa

Comprising a land area of ca 90000 km2, less than 4% of the total land area for the Southern African subcontinent, the Cape Floristic Province is one of the world's richest areas in terms of botanical diversity for its size. An estimated 8650 species of vascular plants occur in this area, about 65% of which are endemic. This is about 42% of the estimated total for all of southern Africa. The number of species packed into so small an area is remarkable for the temperate zone, and compares closely with species totals for areas of comparable size in the wet tropics. The Cape Region consists of a mosaic of sandstone and shale substrates that give rise to soils of quite different types, and in addition local areas of limestone add to the edaphic diversity. Climates across the region are extremely variable, and the predominant orographic rainfall pattern ranges from 2000mm locally to less than 100mm, often with extremely steep gradients, the result of a mountainous landscape. The edaphic diversity resulting from a mosaic of different soils is compounded by sharp local gradients in precipitation that creates an unusual number of local habitats. A feature of the some of the soils in the Region is low nutrient levels and many of the plants on such soils have low seed dispersal capabilities, a factor important in explaining the high levels of local endemism. Species richness in the Cape Region is hypothesized to have resulted from the presence of a complex mosaic of diverse habitats and steep ecological gradients against a background of relatively stable climate and geology after the mediterranean climate was established there sometime after the beginning of the Pliocene. A local or ecological mode of speciation may have been more important under these conditions than allopatric speciation.     

Microbial Metabolism as an Evolutionary Response: The Cybernetic Approach to Modeling

ABSTRACT:?

The growth and metabolic capabilities of microorganisms depend on their interactions with the culture medium. Many media contain two or more key substrates, and an organism may have different preferences for the components. Microorganisms adjust their preferences according to the prevailing conditions so as to favor their own survival. Cybernetic modeling describes this evolutionary strategy by defining a goal that an organism tries to attain optimally at all times. The goal is often, but not always, maximization of growth, and it may require the cells to manipulate their metabolic processes in response to changing environmental conditions.

The cybernetic approach overcomes some of the limitations of metabolic control analysis (MCA), but it does not substitute MCA. Here we review the development of the cybernetic modeling of microbial metabolism, how it may be combined with MCA, and what improvements are needed to make it a viable technique for industrial fermentation processes.

IMTECH communication no.001/2001