Seed banks of invasive Australian Acacia species in South Africa: Role in invasiveness and options for management

Despite impressive efforts at clearing stands of invasive Australian Acacia species in South Africa, insufficient attention has been given to understanding the role of seed banks in the invasiveness and long-term persistence of populations. We review information on seeds of these species, considering seed production, seed rain, and the dynamics of seeds in three layers: leaf litter, and upper and lower seed banks in the soil. Many factors affect the accumulation and susceptibility to destruction of seed banks and thus the opportunities for intervention to reduce seed numbers for each of these components. Reduction of seed banks is crucial for the overall success of the multi-million dollar management initiatives against these species. Classical biological control of buds, flower and young pods has reduced the seed production of many Australian acacias in South Africa. Fire can be applied to reduce seed numbers in the leaf litter and upper seed bank in some cases, although there are serious problems associated with high fire intensities in dense acacia stands. Other options, e.g. soil inversion and solarisation, exist to exercise limited reduction of seed numbers in some situations. There is little prospect of meaningful reduction of seed numbers in the lower seed bank. Preventing the accumulation of seed banks by limiting seed production through biological control is by far the most effective means, and in almost all cases the only practical means, of reducing seed numbers. This must be an integral part of management strategies. Several invasive Australian acacias are already under effective biological control, and further work to identify additional potential agents for all the currently invasive species and potentially invasive alien species is the top priority for improving the efficiency of management programmes.     

Patterns of stem photosynthesis in two invasive legumes (Spartium junceum,Cytisus scoparius) of the California coastal region

Stem assimilation of Spartium junceum and Cytisus scoparius was measured over diurnal cycles during four time periods of 1992 in California. Spartium junceum plants were growing at an inland, coastal mountain site while the C. scoparius plants were growing at a coastal bluff habitat. Both species had positive stem assimilation that resulted in approximately 200 mmol m ² day^-1 carbon dioxide accumulation. Daily carbon gain decreased from spring to fall for S. junceum due to a decrease in shoot water potential. Although C. scoparius had the same relationship between assimilation and shoot water potential as that of S. junceum, carbon gain and water potential did not decrease during the year for C. scoparius. The major limitation for carbon gain of C. scoparius was light intensity because the coastal site was characterized by lower temperature, higher humidity, and more fog than the inland site. Although these species grew in habitats that had a different vapor pressure and temperature, the assimilation response to vapor pressure was similar between the species. Water use efficiency was higher and intercellular carbon dioxide was lower for S. junceum compared to C. scoparius. Although the leaves of both species are ephemeral, the canopy has a constant positive carbon balance because of stem assimilation. The constant carbon gain throughout the year, from stem assimilation, may enhance the growth capacity of these invasive species in disturbed habitats.     

Paranthodon africanus (broom) a stegosaurian dinosaur from the Lower Cretaceous of South Africa

The holotype of Paranthodon africanus (Broom) from the Kirkwood Formation (Lower Cretaceous) of the Algoa Basin, Cape Province, South Africa consists of a partial skull, the bones of which are very similar to those of Stegosaurus. Both sides of the maxillary tooth crowns have a bulbous cingulum and a very prominent central vertical ridge above the large apical denticle that is bordered anteriorly and posteriorly by four to seven smaller denticles. Diagnostically stegosaurian material is also known from the Lower Cretaceous of England (Craterosaurus) and China (Wuerhosaurus) and the Upper Cretaceous of India (Dravidosaurus).     

In pursuit of environmentally friendly straws: a comparative life cycle assessment of five straw material options in South Africa

The International Journal of Life Cycle Assessment - The increasing global concern surrounding plastic pollution has resulted in a spotlight being placed on major contributors. Straws have been...     

Parasitoids ofPlutella xylostella (Lep.: Plutellidae) in South Africa: An annotated list

Larvae and pupae of diamondback moth,Plutella xylostella (L.) (Lepidoptera: Plutellidae), were collected weekly for two years on unsprayed cabbage plots. Samples were taken to the laboratory and parasitoids that emerged were identified and their incidence determined. Parasitoids were active throughout the year and parasitism was high (reaching 90–100%) except in the winter months of June–August when it was low. Twenty one species were reared: the egg-larval parasitoidsChelonus curvimaculatus Cameron and Chelonus sp. (Braconidae); the larval parasitoidsApanteles eriophyes Nixon,Cotesia plutellae (Kurdjumov),Habrobracon brevicornis (Wesmael) (Braconidae) andPeribaea sp. (Tachinidae); the larvalpupal parasitoidsDiadegma sp.,Itoplectis sp. (Ichneumonidae) andOomyzus sokolowskii (Kurdjumov) (Eulophidae); the pupal parasitoidsBrachymeria sp.,Hockeria sp. (Chalcididae),Diadromus collaris Gravenhorst (Ichneumonidae) andTetrastichus howardi (Olliff) (Eulophidae); and the hyperparasitoidsAphanogmus fijiensis (Ferrière) (Ceraphronidae),Brachymeria sp.,Hockeria sp.Proconura sp. (Chalcididae),Mesochorus sp. (Ichneumonidae),Pteromalus sp. (Pteromalidae),Eurytoma sp. (Eurytomidae) andTetrastichus sp. (Eulophidae).     

Preliminary exposure assessment of deoxynivalenol and patulin in South Africa

Deoxynivalenol (DON) and patulin (PAT) are mycotoxins widely regulated internationally. DON is frequently found in cereals, whereas PAT is commonly found in apple juices. A survey of South African commercial products was conducted on DON levels in maize meal and wheat flours, and on PAT levels in apple juices. DON levels in 23 wheat flour samples (mean of 16 positives, 29 μg/kg) were equal to or below 100 μg/kg and in wheat consumers contributed 6–13% of the provisional maximum tolerable daily intake (PMTDI; 1 μg/kg body weight per day) for DON set by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). Sixteen of 18 maize meal samples were contaminated, with a mean for positive samples of 294 μg/kg, and the probable daily intakes ranged from 3.67 μg/kg body weight per day in rural infants to 1.39 μg/kg body weight per day in urban adults. PAT levels in 20 of 30 apple-juice samples were below the detection level of 10 μg/l. Mean of positive samples was 210 μg/l, with three samples exceeding the South African legal limit of 50 μg/l and the highest level (1,650 μg/l) showing the possibility of a brief but high exposure of 37 μg/kg body weight per day (or 9,250% of the JECFA PMTDI of 0.4 μg/kg body weight per day) in young children.     

Status of life cycle assessment and engineering research in South Africa

In view of the upcoming 2002 World Summit in Johannesburg, sustainable development is a topic of high priority in South Africa. Although the South African competency in Life Cycle Assessment (LCA) and Life Cycle Engineering (LCE) has grown to some extent over the last ten years, South African industry and government have been slow to realise the benefit of LCAs and LCE as tools to support cleaner production and sustainable development. However, the local application of these tools, as well as considerations during their use, differs from practices in developed countries. The applications of LCAs and LCE, the type of organisations involved and the limitations and common problems associated with these tools in South Africa are discussed.     

Developing a systems approach for Sternochetus mangiferae (Coleoptera: Curculionidae) in South Africa

Sternochetus mangiferae (F.) (Coleoptera: Curculionidae) is a quarantine pest of mango, Mangifera indica L., in South Africa. The aim of the study was to test cultural and chemical control measures in a systems approach for risk mitigation of S. mangiferae in South Africa. A large-scale experiment, using a randomized block design with three replicates, was undertaken on 'Tommy Atkins' mangoes in South Africa. Five treatment combinations were applied over two seasons: (1) untreated control; (2) sanitation and physical removal of egg-infested fruit (P+S); (3) thiamethoxam, P+S; (4) thiamethoxam, fipronil, P+S; and 5) thiamethoxam, two fenthion applications, P+S. A weekly random sample of eight fruit from 40 trees per orchard was taken from 5 wk to harvest over two harvest periods. In total, 57,600 fruit were sampled. In a separate experiment, the same variety was used to test the efficacy of covering fruit with paper bags over one season in a completely randomized design. In both trials, all the pests were recorded from internal and external fruit inspections. In trial 1, results after the first season showed >98% control in the three chemical combination treatments. In the second season, treatment 2 provided 19% and treatment 3 99.9% control, whereas no fruit were infested with S. mangiferae in treatments 4 and 5. Trial two showed that fruit bagging significantly reduced S. mangiferae infestation. The data showed that a systems approach for S. mangiferae control in South Africa can be effective and that bagging can be an effective organic control option.     

New species of Crotonia (Acari: Oribatida) from South Africa

Four new species of oribatid mites of the genus Crotonia , ( C. pauropelor sp. nov., C. dicella sp. nov., C. lyrata sp. nov. and C. ecphylla sp. nov. ) are described from soil and plant litter from South Africa. Crotonia pauropelor, C. dicella and C. ecphylla are allied to the 'capistrata' species-group, previously known only from Queensland, Australia, in that they possess the full complement of c setae on the notogaster. They differ in having eight pairs rather than nine pairs of genital setae. In addition, C. ecpylla is unusual in the genus Crotonia in that it appears to possess two pairs of setae on each of the second epimera. Crotonia lyrata has only two pairs of c setae and is allied to the 'cophinaria' species-group. This is only the second published record of the genus Crotonia from South Africa, and the first of any named species. A key to the African Crotonia species is provided, which includes the only two previously known species C. alluaudi and C. rothschildi (Berlese, 1916).     

An analysis of the mole rats (Mammalia: Rodentia) from Langebaanweg (Mio-Pliocene, South Africa)

A study of the taphonomy and age profiles of the mole rat population from Langebaanweg ‘E’ Quarry was undertaken in order to see if these subterranean rodents had been accumulated by predation (coprocoenosis hypothesis) or as a result of drowning in their burrows during a flood event (catastrophocenosis hypothesis). Previous research has cited the bathyergids as being the most common rodent at Langebaanweg, however, a comprehensive study of new micromammal material indicates that murids, rather than mole rats, dominate most of the assemblages. The concentration of mole rat remains in many of the fossil-bearing levels at Langebaanweg is, nevertheless, still extremely high compared to other fossil sites or predation assemblages in the area. A taphonomic examination of mole rat incisor surfaces indicates that digestion occurs on between 44% and 54% of incisors in the different assemblages, and this, together with the degree of digestion suggests that category 1 and category 2 predators had been responsible for the accumulation of the fossil mole rat assemblages. The absence of rounding, polishing or weathering on the fossils indicates that there has been little or no transport by water, and that burial of the bones was rapid. Breakage and damage to the anterior portion of many of the mandibles made it impossible to accurately assess the age of the older mole rats, and the majority of mandibles could provide only a minimum age of the animal at the time of death. The age profile indicates that very young individuals are missing from the assemblages. This allows for refutation of the previously made suggestion that flooding was responsible for the death of the majority of Langebaanweg mole rats and also introduces the possibility that Bathyergus hendeyi may have been a social animal, unlike extant bathyergids which are solitary.     

Sustainable utilization of woodrose-producing mistletoes (Loranthaceae) in South Africa

Pedistylis galpinii and Erianthemum dregei produce woodrose outgrowths at attachment points with host trees. In some rural areas of southern Africa, woodroses are sold as curios. The socio-economics related to woodrose harvesters were investigated via interview schedules and field survey. Harvesting is not detrimental to hosts as only branches infected with mistletoes are cut. Over half the harvesters interviewed reported harvesting both live and dead mistletoes while 20% used only dead ones. The density of dead mistletoes could satisfy present demand. Such sustainable harvesting practices (only using dead woodroses) allow for woodrose harvesting according to calculated quotas. The median gross income per month generated from woodroses was estimated to be between US $38 and 90. Eleven percent of harvesters relied on woodroses as their only source of income. Marketing was relatively haphazard, involving informal selling at roadsides and unscheduled visits to retailers. The market for woodroses can be expanded and the potential exists to increase supply considerably on a sustainable basis.     

Birds as predators of ticks (Ixodoidea) in South Africa

A total of 7,334 crop and/or stomach contents from 239 species of South African birds were examined for ticks. Only 36 ticks were found: 24 in 21 cattle egret (Bubulcus ibis), four in four helmeted guineafowl (Numida meleagris), one in a crowned plover (Vanellus coronatus) and seven in a single lilacbreasted roller (Coracias caudata). In most cases identification of the ticks was not possible although the genera Boophilus, Hyalomma and Rhipicephalus were represented. With the exception of the oxpeckers which were not represented in this survey, we conclude that predation by birds on ticks is uncommon in South Africa.     

Beetle pollination of peacock moraeas (Iridaceae) in South Africa

The peacock moraeas are South African geophytes withIris-like flowers that are characterized by broad outer tepals with iridescent spots. Three of the seven species were studied and found to be exclusively visited and pollinated by beetles. The primary pollinators were hopliine (Scarabaeidae) beetles in the generaPeritrichia, Monochelus, Anisonyx andAnisochelus. These beetles visit flowers for nectar, pollen and mating.Peritrichia rufotibialis was the primary pollinator ofMoraea villosa, P. abdominalis was the primary pollinator ofM. tulbaghensis, whileMonochelus sp. nov. was the primary pollinator of the third species,M. neopavonia. High levels of fruit set attest to the effectiveness of these beetles as pollinators. Average fruit set ranged from 83.5 ± 34.8% (M. villosa) to 97.2 ± 11.6% (M. tulbaghensis). Average seed set in the various populations was more variable, but was also quite high, ranging from 77.3 ± 40.8 (M. villosa) to 342.2 ± 115.0 (M. neopavonia) seeds per capsule. Although hopliine beetles are abundant and diverse in southern Africa and commonly visit flowers, this is the first well-documented report of pollination by these beetles.     

An economic assessment of the contribution of biological control to the management of invasive alien plants and to the protection of ecosystem services in South Africa

This study is a first attempt at a holistic economic evaluation of South African endeavours to manage invasive alien plants using biological control. Our focus was on the delivery of ecosystem services from habitats that are invaded by groups of weeds, rather than by each individual weed species. We established the net present value of the weed biological control efforts, and derived benefit:cost ratios by comparing this value (a cost) to the estimated value of ecosystem services protected by weed biological control. We identified four major functional groupings of invading alien plants, and assessed their impact on water resources, grazing and biodiversity. We estimated the area that remained free of invasions due to all historic control efforts in South Africa, and the proportion that remained free of invasion as a result of biological control (which was initiated in 1913). The estimated value of potential ecosystem services amounted to 152 billion South African rands (ZAR—presently, about US$ 19.7 billion) annually. Although an estimated ZAR 6.5 billion was lost every year due to invading alien plants, this would have amounted to an estimated additional ZAR 41.7 billion had no control been carried out, and 5–75% of this protection was due to biological control. The benefit:cost ratios ranged from 50:1 for invasive sub-tropical shrubs to 3,726:1 for invasive Australian trees. Benefit:cost ratios remained positive and our conclusion, that biological control has brought about a considerable level of protection of ecosystem services, remains robust even when our estimates of the economic impacts of key variables (i.e. sensitivity analyses of indeterminate variables) were substantially reduced.     

A new species of Polystichum (Pteridophyta: Dryopteridaceae) from South Africa

A new Polystichum (Pteridophyta: Dryopteridaceae) species, P. incongruum J.P.Roux sp. nov. from the Western and Eastern Cape Provinces from Soudi Africa is described. This variable species is related to P. pungens (Kaulf.) C.Presl but differs from it in pinnule morphology, the frequent occurrence of glandular cells along the sporangium stalk, the (more rare) occurrence of clavate unicellular glands along the indusium margin and a chromosome number of 2 n = 164.     

Economic analysis of emerald ash borer (Coleoptera: Buprestidae) management options

Emerald ash borer, Agrilus planipennis (Fairmaire) (Coleoptera: Buprestidae), plays a significant role in the health and extent of management of native North American ash species in urban forests. An economic analysis of management options was performed to aid decision makers in preparing for likely future infestations. Separate ash tree population valuations were derived from the i-Tree Streets program and the Council of Tree and Landscape Appraisers (CTLA) methodology. A relative economic analysis was used to compare a control option (do-nothing approach, only removing ash trees as they die) to three distinct management options: 1) preemptive removal of all ash trees over a 5 yr period, 2) preemptive removal of all ash trees and replacement with comparable nonash trees, or 3) treating the entire population of ash trees with insecticides to minimize mortality. For each valuation and management option, an annual analysis was performed for both the remaining ash tree population and those lost to emerald ash borer. Retention of ash trees using insecticide treatments typically retained greater urban forest value, followed by doing nothing (control), which was better than preemptive removal and replacement. Preemptive removal without tree replacement, which was the least expensive management option, also provided the lowest net urban forest value over the 20-yr simulation. A no emerald ash borer scenario was modeled to further serve as a benchmark for each management option and provide a level of economic justification for regulatory programs aimed at slowing the movement of emerald ash borer.     

The role of geomorphology in evaluating remediation options for floodplain wetlands: the case of Ramsar-listed Seekoeivlei,eastern South Africa

The range of benefits bestowed by wetlands is today increasingly recognized, and remediation of degraded wetlands is being carried out around the world. Many degraded wetlands are associated with river floodplains, and an essential requirement for their remediation planning is a comprehensive knowledge of the geomorphological functioning of the river channel and floodplain. Here, we review previous geomorphological investigations of the Ramsar-listed Seekoeivlei floodplain wetlands, Free State Province, South Africa, and demonstrate how the knowledge gained is playing a key role in evaluating remediation options that are needed following more than a century of direct and indirect human impacts. Faunal and floral changes, coupled with channel modifications, have altered the flow and sediment regime and initiated major changes to erosional and depositional patterns, including promoting rapid headward growth of a new channel and abandonment of a former channel. These changes have led to further management interventions, including installation of weirs and erosion control structures. In an ideal world, remediation would strive to return a wetland to its natural, pre-impact state but, in reality, other management goals have to be taken into consideration. In the case of Seekoeivlei, these include maintaining current habitat and biodiversity (this has the added advantage of promoting local tourism, especially bird watching), and using the wetlands for water quality enhancement. Attempts to return the wetlands to their pre-impact state (e.g. by removing exotic trees and erosion control structures) would in fact further reduce habitat and biodiversity, permanently in the case of some avian species, and for centuries in the case of some aquatic species, because of the very slow natural rates of channel and floodplain change. Alternative options will all require ongoing intervention, albeit of variable intensity, but in effect will mean that the wetland will never return to its pre-impact state. Remediation will thus create an essentially ‘artificial’ wetland complex that restores some of the ecological and hydrological functions but that is likely to remain very far from its natural geomorphic condition.     

Molecular and morphological evidence for a new species from South Africa: Carex rainbowii (Cyperaceae)

Carex rainbowii (Cariceae, Cyperaceae), a new species from the Drakensberg mountains (KwaZulu-Natal province), is described and illustrated. It was found in the shady understory of the Afromontane forest in the Cathedral Peak area. An additional, nearby population was also identified based on previously collected herbarium material. Morphological and molecular (cpDNA 5′trnK intron and nrDNA ITS and ETS sequences) data were used to evaluate the taxonomic status of these populations and shed light on their systematic placement. Our data strongly support their taxonomic identity and inclusion in Carex sect. Sylvaticae. The new species can be readily distinguished from other related taxa mainly by the frequently androgynecandrous terminal spike, dense female spikes, hyaline glumes, as well as by some quantitative features. This finding implies a considerable biogeographic disjunction from the mainly Eurasian-North African range of the remaining species of sect. Sylvaticae, a pattern also found in the related sections Ceratocystis, Rhynchocystis and Spirostachyae. Comments are provided on previous misidentifications of C. rainbowii as the closely related Carex sylvatica. Data pertinent to the conservation status of the species are provided.