Species richness of arachnids associated with Protea nitida (Proteaceae) in the Cape fynbos.

Regular counts of Arachnida on Protea nitida Mill. were made in three study areas in the western Cape over a period of one year. They were also investigated in the rest of the natural distribution area of P. nitida in the southern and western Cape. Collections were made according to three standardized methods. Five arachnid orders were collected, of which the Araneae (spiders) were dominant. Thirty-two spider species (653 individuals) representing 18 families were collected, of which five families and eight genera (eight species) were recorded for the first time on the Proteaceae in the Cape fynbos. Four non-Araneae orders were collected. A microhabitat preference was observed in some families. Numbers of immature spiders peaked in autumn. Adults and immatures did not always have the same habitat distribution and did not always peak during the same season. Families also showed differences in seasonal abundance. Plant architecture and distribution influenced the number of species collected. Protea nitida hosted more spider species than less complex plants with smaller distributions. The implications of these findings are discussed in terms of biodiversity and invertebrate conservation.     

Insect diversity in Cape fynbos and neighbouring South African vegetation

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.     

Reproductive traits of two closely related species-pairs on adjacent,different soil types in South African Fynbos

High levels of edaphic endemism and soil-related beta-diversity in Agulhas Plain fynbos communities suggest that reproductive traits of plants growing on different fynbos soils would be related to differences in soil regime. We investigated reproductive traits in two closely related Proteaceae species-pairs growing on adjacent soil types: Protea obtusifolia and Leucadendron meridianum occurring in shallow pockets of limestone-derived soils, and P. susannae and L. coniferum on the adjacent, uniformly deep colluvial sands.We found that species growing on the limestone soil comprised smaller plants, with fewer cones and seeds per plant, than species on the colluvial sands. These differences suggest that the small soil pockets of limestone soil limit plant size, in turn limiting the number of reproductive structures. Annual variation in cones and seed was the same in all species. There were no consistent trends in degree of serotiny, or sex allocation across soil types. The higher cone and seed predation levels of both limestone species than the colluvial sands species were ascribed to the higher plant densities of the former leading to lower insect search times. It was concluded that there were no overall patterns in reproductive traits that could be ascribed to differences in soil regime, other than through size-related effects. Fire regime is likely to have played a more important role in determining reproductive traits.Department of Statistical Sciences, University of Cape Towm     

Stimulation of seed germination in South African species of Restionaceae by plant-derived smoke

The Restionaceae is one of the three major families defining fynbos, the characteristic vegetation type of the Cape Floristic Region. Periodic fires with a frequency of 5 to 40 years are a natural phenomenon in fynbos vegetation. Fire-stimulated seed germination has been reported for a variety of fynbos species, and species in the Asteraceae, Ericaceae, Proteaceae and Restionaceae have shown a germination response to smoke and/or aqueous smoke extracts. In the present study seed of 32 species was screened to obtain an indication of how important the smoke cue is for germination in the South African Restionaceae. The results of the present study represents the first occasion that comparative germination data for South African species in this family have ever been obtained. Twenty-five of the 32 species tested showed a statistically significant improvement in germination following smoke treatment. Untreated seeds of 18 of the species responding, showed a high degree of dormancy with only 0.1% to 2.0% germination. These results suggest that under natural conditions smoke from fynbos fires may provide an important cue for triggering seed germination in this family. The degree of improvement in germination following smoke treatment ranged from 147% in the case of Restio festuciformis to 25300% in the case of Rhodocoma capensis. It is suggested that the 16 species which showed a 1000% or more increase in germination following smoke treatment form a group in which smoke is likely to be the major cue for germination. In those species in which there is a lesser response, smoke may be one of a number of germination cues which include heat, and possibly alternating high and low incubation temperatures. The four species that did not germinate were all myrmecochorus, nut-fruited species. More information is needed concerning the fire survival strategy of South African Restionaceae species and many more will have to be investigated in the nursery and in the field, before the full pattern of response within the family and its significance can be elucidated.     

Host‐associated genetic differentiation in pecan leaf phylloxera

Host‐associated differentiation (HAD) is the formation of genetically distinct host‐associated populations. One of the genotypic signatures of HAD is that populations exhibit stronger differentiation by host‐plant species than by geographic isolation. HAD, as a mechanism promoting ecological speciation, has been invoked to explain phytophagous insect diversity. Two traits proposed to promote HAD are endophagy and parthenogenesis. Using amplified fragment length polymorphisms (AFLPs), we tested for the presence of HAD in pecan leaf phylloxera, Phylloxera notabilis Pergande (Hemiptera: Phylloxeridae), an endophagous, gall inducing, and cyclically parthenogenetic insect on sympatric pecan and water hickory at a geographic mesoscale. This species shows strong HAD. Whereas the effect of collecting site was significant, accounting for 7.3% of molecular variation, host‐plant species identity accounted for 63.5%. In addition, a choice test indicated that pecan leaf phylloxera originating from water hickory showed weak but significant preference for leaflets of the natal host, whereas pecan leaf phylloxera originating from pecan did not. This is the first such study of a species of arboreal Phylloxeridae, a poorly known insect group. This is also the first endophage and the second parthenogen shared by these two hickory species to show evidence of HAD. This hickory system could be a good parthenogen‐rich counterpoint to the goldenrod system in the study of HAD in insect communities.     

Testing host‐associated differentiation in a quasi‐endophage and a parthenogen on native trees

Host‐associated differentiation (HAD) is the formation of genetically divergent host‐associated sub‐populations. Evidence of HAD has been reported for multiple insect herbivores to date, but published studies testing more than one herbivore for any given host‐plant species pair is limited to herbivores on goldenrods. This limits the number of pair‐wise comparisons that can be made about insect life‐history traits that might facilitate or inhibit host‐race development in general. Two traits previously proposed to facilitate HAD include endophagy and parthenogenesis. We tested for HAD in two herbivores, a quasi‐endophagous caterpillar and a parthenogenetic aphid, feeding on two closely related species of hickories. We found that the quasi‐endophage is panmictic, whereas the parthenogen exhibits HAD on their sympatric host plants, pecan and water hickory, at a geographic mesoscale. This is an important first step in the characterization of HAD in multiple insect herbivores using North American hickories, a host‐plant system with many shared parthenogens.     

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.     

Plant characteristics determine insect borer assemblages on Protea species in the Cape Fynbos, and importance for conservation management

The influence of regional climate, biotope and host-plant variables on the frequency of occurrence of insect borers associated with infructescences of Protea species in the species-rich flora of the Cape Fynbos was investigated. Large samples of infructescences (n=1000) were collected on a seasonal basis and borers identified and quantified. Data were analysed using DECORANA and CANOCO so as to correlate environmental variables with borer occurrence. Distinct differences in frequency of occurrence of the various insect taxa were recorded on the various plant species studied. These differences were primarily accounted for by physical host-plant characteristics (infructescence and seed set variables), and secondarily, by biotope variables and climatic factors. Fynbos plant characteristics therefore play a major role in determining insect abundance. Plant diversity in the Fynbos is maintained by burning. These management burns, however, should not be applied too frequently or over areas large enough to extirpate any borer species. As these borers are excellent umbrellas for many other insects, their conservation covers Fynbos insect diversity in general.     

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.     

Herbivores,but not other insects,are scarce on alien plants

Abstract Understanding how the landscape‐scale replacement of indigenous plants with alien plants influences ecosystem structure and functioning is critical in a world characterized by increasing biotic homogenization. An important step in this process is to assess the impact on invertebrate communities. Here we analyse insect species richness and abundance in sweep collections from indigenous and alien (Australasian) woody plant species in South Africa's Western Cape. We use phylogenetically relevant comparisons and compare one indigenous with three Australasian alien trees within each of Fabaceae: Mimosoideae, Myrtaceae, and Proteaceae: Grevilleoideae. Although some of the alien species analysed had remarkably high abundances of herbivores, even when intentionally introduced biological control agents are discounted, overall, herbivorous insect assemblages from alien plants were slightly less abundant and less diverse compared with those from indigenous plants – in accordance with predictions from the enemy release hypothesis. However, there were no clear differences in other insect feeding guilds. We conclude that insect assemblages from alien plants are generally quite diverse, and significant differences between these and assemblages from indigenous plants are only evident for herbivorous insects.     

Concentration of ultraviolet-B radiation absorbing compounds in leaves of a range of fynbos species

Leaves from 38 species representing 17 families were collected from contrasting elevations (100 to 824 m above sea level) in sclerophyllous mountain fynbos vegetation near Hermanus, South Africa, and the leaf percentage dry mass (PDM), specific leaf mass (SLM) and ultraviolet-B (UV-B, 280 to 320 nm) absorbance properties determined. Leaf PDM, SLM and UV-B absorbance were generally high compared to mesophyllous plants. Leaves collected at high elevation exhibited higher absorbances per unit dry mass at both 280 and 320 nm than those from the same species at low elevation. No differences in absorbance per unit leaf area were observed. UV-B absorbance properties differed between families, with high values obtained for the Apiaceae, Asteraceae, Cyperaceae, Ericaceae, Penaeaceae and Proteaceae, but lower values for the Anacardiaceae, Fabaceae and Geraniaceae. A positive correlation was found between absorbance at 280 nm per unit leaf area and SLM. It was concluded that most fynbos species, on account of their highly sclerophyllous leaves and large accumulation of UV-B absorbing compounds (flavonoids and related phenolics) may be well protected against future increases in UV-B radiation.     

Conservation of the insect assemblages of the Cape Peninsula biodiversity hotspot

The Cape Peninsula is an area of outstanding biological importance, not only for to its high levels of floristic diversity and endemism, but also for its number of localised endemic invertebrates. Little is known of the spatial distribution of invertebrates across the Peninsula, or how best to conserve them. Sampling by visual searches assisted by aerial and aquatic hand-nets was undertaken throughout the Peninsula. The most important areas for insect diversity on the Peninsula, and associated environmental variables, were determined. The ‘Peninsula effect’ was also investigated. Nine Red Listed species and five new species for the Peninsula were recorded. This high number of Red Listed species (for those few groups that have been assessed) emphasises the biological importance of the Cape Peninsula. Table Mountain had the most Red Listed species, while Cape Point had many species not found in the other areas. Noordhoek Wetland is very important for aquatic Coleoptera. Small hills on the Peninsula are important for overall insect diversity. Elevation, slope, aspect, distance to water and vegetation structure were the most important environmental variables in determining the insect assemblages. The Peninsula effect appears to have no influence on these particular insect assemblages of the Cape Peninsula. The high number of new Peninsula records for well-known taxonomic groups indicates that still little is known of the insect assemblages across the Peninsula. Nevertheless, areas of conservation priority identified in this study are Table Mountain (for Red Listed species), Noordhoek (for aquatic Coleoptera) and Cape Point and the small hills across the Peninsula (for their unique invertebrate assemblages). Conservation of a variety of elevations, including steep and flat areas, all aspects of mountains, as well as both the wet and dry areas, overall will contribute to the conservation of the insects.     

Nectar sugar preferences and absorption in a generalist African frugivore, the Cape White-eye Zosterops pallidus

Sugar preferences and absorption efficiencies were investigated in the Cape White-eye Zosterops pallidus , a generalist frugivore. Unlike the mainly American frugivorous passerines previously studied, Cape White-eyes preferred 20% (weight: weight) solutions of sucrose to glucose or fructose, and apparently possess high sucrase activity because absorption efficiencies for all three sugars were close to 100%. Cape White-eyes rejected 20% solutions containing a fourth nectar sugar, xylose, recently found in the nectar of Protea and Faurea (Proteaceae). Absorption efficiencies for xylose averaged 61%, but we do not know whether this sugar is utilized by the birds. Cape White-eyes thus resemble specialized southern African nectarivores (Nectariniidae, Promeropidae) in their responses to nectar sugars.     

Diversity,composition and guild structure relationships between soil-stored seed banks and mature vegetation in alien plant-invaded South African fynbos shrublands

We investigated vegetation-seed bank relationships at three fynbos sites on the Cape Peninsula, South Africa, and the impacts to these sites of invasion by the alien tree Acacia saligna. Soil-stored seed banks in uninvaded fynbos were of a similar density to those previously measured in fynbos (ca. 1100–1500 seeds m^-2) and were dominated by mostly short-lived species. Lack of similarity between mature vegetation and seed banks, suggests that seed banks are poor predictors of mature vegetation composition and structure in fynbos. This lack of correspondence was attributed to the ephemerals (present only in the soil seed bank) and the dominance of serotinous (aerial seed bank) and sprouting (soil seed bank low to absent) species, in mature vegetation. Long-lived seeders were among the 10 most abundant species in the seed banks at all sites and at two sites shrub species contributed more to seed bank richness than any other growth form. Soil-stored seed banks, therefore, boost species richness and diversity both in early post-fire and later seral stages.There was a decline in fynbos species richness, diversity and abundance both in the standing vegetation and seed banks with increasing duration of invasion by the alien tree, Acacia saligna. However, the rate of decline was higher for the vegetation than the seed banks, suggesting that many fynbos species have long-term persistent seed banks. At two sites, there was no obvious shift in community composition associated with Acacia invasion: invaded sites were depauperate versions of the uninvaded site. However, at a third site, the vegetation composition shifted towards a community dominated by bird-dispersed thicket species and its seed bank shifted towards a community dominated by wind-dispersed perennials. Community composition of the soil seed banks under dense, recent Acacia was very similar to that of the corresponding uninvaded fynbos at all sites, indicating that there is good potential to return to species-rich fynbos vegetation after removal of the alien Acacia. Most seed bank species persisted in the soil seed bank of the long-invaded fynbos at low frequency and density, indicating high seed longevity in many species. We suggest that either a thick Acacia litter layer or a deep (>5 cm) burial moderated the fire and ambient temperature effects, preventing these seeds from germinating after fire and thus preventing loss from the seed bank.     

Fungal endophytes of proteaceae, with particular emphasis onBotryosphaeria proteae

Fungal endophytes occurring in leaves and stems of three species of Proteaceae,Protea cynaroides, Leucospermum cordifolium andLeucadendron salignum×laureolum were investigated on farms in three locations in the Western Cape province of South Africa. The aims of this study were to determine ifBotryosphaeria proteae, a fungus that has been recorded from leaf spots ofProtea spp., was mostly restricted to leaf tissue, and whether it could occur as an endophyte in different members of Proteaceae. In this studyB. proteae was routinely isolated inProtea andLeucospermum, although it was not a dominant taxon and did not occur inLeucadendron. Botryosphaeria proteae occurred mostly in leaves, rather than stems, suggesting that it is not important as a stem canker pathogen.     

Effects of alien pine plantations on small mammal community structure in a southern African biodiversity hotspot

Commercial plantations and alien tree invasions often have substantial negative impacts on local biodiversity. The effect of plantations on faunal communities in the fire‐adapted fynbos vegetation of the Cape Floristic Region biodiversity hotspot is not yet well quantified. We studied small mammal community structure in alien Pinus radiata plantations and adjacent fynbos regenerating after clear‐felling of plantations on the Cape Peninsula, South Africa. Small mammal sampling over 1,800 trap‐nights resulted in 480 captures of 345 individuals (excluding recaptures) representing six species. Significantly more species, individuals (12 X) and biomasses (29 X) of small mammals occurred on recovering fynbos sites compared to plantations. This was commensurate with a higher diversity of plant growth forms, vegetation densities and live vegetation biomass. Only one small mammal species, the pygmy mouse (Mus minutoides), was consistently trapped within plantations. Fynbos sites were dominated by three small mammal species that are ecological generalists and early successional pioneer species, rendering the recovering fynbos slightly depauperate in terms of species richness and evenness relative to other studies done in pristine fynbos. We make three recommendations for forestry that would facilitate the restoration of more diverse natural plant communities and progressively more diverse and dynamic small mammal assemblages in a key biodiversity hotspot.     

Spatial and temporal variation in species-area relationships in the Fynbos biological hotspot

Species-area relations (SARs) are among the few recognized general patterns of ecology, are empirical relations giving the number of species found within an area of a given size and were initially formulated for island environments. The use of SARs has been extended to mainland environments, and to give baseline estimates of extinction rates attending habitat loss. Using current species distributions based on atlas data, we examined the spatial variation of rates of species accumulation and species-area curves for Proteaceae species for all one-minute by one-minute areas within the Cape Floristic Region, South Africa. We compared SARs for current distributions to those generated from modeled future Protea distributions following climate change. Within one biome and for two different scales, there exists a very large spatial variation in turnover rates for current Proteaceae distributions, and we show that these rates will not remain constant as climate warming progresses. As climate changes in coming years, some areas will gain species due to migration, as other areas lose species, and still other areas maintain current rates of species accumulation/turnover. Both current and future distributions show highly variable rates of species accumulation across the landscape. This means that an average species-area relationship will hide a very large interval of variation among SARs, for both current and future Proteaceae distributions. The use of species-area relations to estimate species extinctions following loss of current habitat, or loss of future climatically-suitable area is likely to result in erroneous predictions.     

The influence of pollinators and seed predation on seed production in dwarf grassland Protea “sugarbushes” (Proteaceae)

Flowers of many plant species are visited by both birds and insects, making it necessary to establish their relative contributions to seed set. In Protea, available evidence points to an overwhelming preponderance of bird-pollination systems in the genus, but the scented flowers of several dwarf grassland “sugarbush” species suggest that some Protea species may be adapted for insect pollination. In this study, we used both selective exclusion of vertebrates and complete exclusion of all visitors to investigate whether the insects that visit the scented flowerheads of three Protea species (Protea dracomontana, Protea simplex and Protea welwitschii) in KwaZulu-Natal, South Africa contribute to seed production. We also performed supplemental hand pollinations to test for pollen limitation. Seed set was generally higher in inflorescences subjected to vertebrate exclusion than in those from which all visitors were excluded, suggesting that fertile cross-pollen was deposited by insects, but these differences were slight because of high levels of self-fertilization in the study species. Pollen deposition and pollen tube growth were similar for vertebrate-excluded and open-pollinated inflorescences. Supplemental hand-pollination treatments revealed that seed set in P. simplex and P. welwitschii was not pollen-limited. Overall seed set was low, typical of the family Proteaceae, and infructescences were highly predated by lepidopteran larvae. We conclude that insects are likely to contribute to seed set of the study species, but further studies using molecular markers are required to establish the actual level of insect-mediated outcrossing.