Climate constrains the establishment and proliferation of Anthonomus santacruzi,a flower-feeding biological control agent of the invasive weed Solanum mauritianum in South Africa

The flowerbud-feeding weevil Anthonomus santacruzi Hustache (Coleoptera: Curculionidae) was released in South Africa in 2008 for the biological control of the invasive tree Solanum mauritianum Scopoli (Solanaceae). The weevil was widely deployed throughout KwaZulu-Natal province, which supports large S. mauritianum infestations, and has become well established in its warmer coastal regions. The aim of this study was to provide field evidence that climate is constraining the weevil’s distribution in South Africa. Solanum mauritianum populations were sampled at 23 sites across an altitudinal gradient in KwaZulu-Natal to determine A. santacruzi densities in relation to food availability and climatic variables. Despite significantly higher amounts of floral material on S. mauritianum at the higher altitude inland sites, A. santacruzi numbers were significantly higher at the lower altitude coastal sites. There was thus a significant negative relationship between A. santacruzi numbers and altitude and significant positive relationships between A. santacruzi numbers and both temperature and humidity. Neither rainfall nor food availability influenced A. santacruzi numbers, although lower amounts of floral material at the coastal sites may well have been caused by higher weevil densities at these sites. Anthonomus santacruzi was absent at only three sites, all at higher altitudes, further demonstrating that conditions in coastal or low-altitude regions are favourable for establishment and population proliferation. Future release efforts in KwaZulu-Natal, but also in other South African provinces, should thus be focused on coastal regions and inland regions that are below 1000 m above sea level.     

Persistence of the flowerbud weevil Anthonomus santacruzi in optimal versus marginal areas: implications for the biological control of the invasive tree Solanum mauritianum in South Africa

Anthonomus santacruzi Hustache (Coleoptera: Curculionidae) was released in South Africa to offset the extensive reproductive output of the invasive tree Solanum mauritianum Scopoli (Solanaceae). Widespread establishment has occurred predominantly in the coastal areas of KwaZulu-Natal province, with limited success in higher-altitude inland areas. Irrespective of location, populations exhibit peaks in the austral autumn and decline during winter. In this study, we evaluated the persistence of A. santacruzi populations in climatically-optimal coastal areas versus climatically-marginal inland areas. The weevil’s pre- and post-winter abundance was surveyed at six coastal and six inland sites during 2018, and compared between areas and seasons. The 2018 pre-winter data were also compared to 2016 pre-winter data collected at the same sites. During 2018, pre- and post-winter numbers were six times and 22 times higher, respectively, at optimal sites than at marginal sites, with substantial winter declines at all sites. Post-winter weevil numbers at optimal sites were significantly higher than pre-winter numbers at marginal sites. Pre-winter numbers at optimal sites were not significantly different between 2016 and 2018, but at marginal sites were significantly lower in 2018. Inflorescences of S. mauritianum at marginal sites contained significantly more floral material and fruit than those at optimal sites, during both seasons in 2018. Significant negative correlations between A. santacruzi numbers and floral/fruit production suggest some impact on the reproductive output of S. mauritianum. Since A. santacruzi populations are barely persisting in marginal areas, releases in other South African provinces should target locations that are below 300?m in altitude.     

Beetle assemblages of indigenous and alien decomposing fruit in subtropical Durban,South Africa

Ecological theory predicts that insect assemblages on indigenous plants will be more diverse than those on alien plants. However, this theory refers primarily to herbivores, and its applicability to decomposers is unclear. Here, we compare beetle assemblages from the fallen fruit of the two most common plants producing large fleshy fruit at our study site in Durban, South Africa: one indigenous African plant (the toad tree, Tabernaemontana ventricosa, Apocynaceae) and one invasive tropical American one (the granadilla, Passiflora edulis, Passifloraceae), at various stages of the decomposition process, thus spanning a continuum between herbivory and detritivory. Beetles found on the two plants included both alien (some categorized as pests of stored fruit) and indigenous species (including some localized endemics). We found that the mean diversity and abundance were not significantly different between the two plant species (with nine beetles from four morphospecies in the average sample) and that the beetle assemblages from the two plant species largely overlap. Statistical analyses suggested that other factors such as stage of fruit decomposition and seasonality could have greater influence on diversity and abundance than the provenance of the plant species. We conclude that insect–plant interactions in the emerging ecosystems that include indigenous and alien species in both groups are complex and that the importance of interactions between species of different provenances may have previously been underestimated.     

Biology, host specificity and risk assessment ofGargaphia decoris, the first agent to bereleased in South Africa for the biological control ofthe invasive tree Solanum mauritianum

The South American tree Solanummauritianum is a major environmental weed in thehigh-rainfall regions of South Africa and has beentargeted for biological control since 1984. Althoughhost ranges of imported agents determined duringquarantine tests have resulted in the rejection ofeight of the 11 candidate agents tested so far, theleaf-sucking lace bug Gargaphia decoris,imported from Argentina in 1995, displayed anacceptably narrow host range in captivity. No-choicetests showed that G. decoris is confined to Solanum species and cannot survive on solanaceouscrops outside that genus. Although these tests alsoindicated that G. decoris colonies could surviveand reproduce on cultivated eggplant (aubergine) andat least five native South African Solanumspecies, all but one native species proved to beinferior hosts in terms of adult survival andoviposition potential. During paired choice andmultichoice tests in small and larger cagesrespectively, G. decoris displayed very strongfeeding and oviposition preferences for S. mauritianum. Analyses of the risk of attack onnon-target Solanum plants revealed that, withone possible exception, none were likely to suffermore than incidental damage in the field. Host recordsfrom South America have also indicated that G. decoris has not been recorded on any Solanumspecies other than S. mauritianum, providingfurther evidence of its host specificity. The resultsof this study were accepted by the regulatoryauthorities and in February 1999, G. decorisbecame the first agent to be released in South Africafor the biological control of S. mauritianum.     

The viability and germination characteristics of exhumed Solanum mauritianum seeds buried for different periods of time

The site, depth and duration of burial significantly influenced the viability and state of dormancy of Solanum mauritianum seeds. Burial at a depth of 15 cm was most effective in reducing the level of conditional dormancy. Secondary dormancy was not induced at any of the environmental (burial) sites when seeds were maintained at 15 cm, where light and temperature fluctuations were minimal. When buried at 4 cm or maintained on the soil surface secondary dormancy was induced, particularly at the inland sites where environmental conditions such as temperature and moisture were more extreme. Conditional dormancy could generally be overcome by incubating seeds at 15/30 °C in the light, even after prolonged burial at unfavourable germination conditions. Gibberellic acid (500 mg l^–1) was very effective in breaking secondary dormancy of seeds induced by storage under unfavourable conditions after burial. These results have important implications for the control of this week in commercial forests.     

The comparative growth rates of indigenous street and garden trees in Grahamstown,South Africa

Urban forestry is advocated worldwide as a means of enhancing the liveability of towns and cities, and mitigating some of the anticipated impacts of climate change. Optimisation of the benefits of trees in urban areas is dependent upon knowledge of tree form, growth, and the products and benefits that trees provide. Growth rates are a vital variable for modelling benefits, yet there is a significant gap in knowledge pertaining to growth rates of trees in urban areas, especially indigenous species in developing world countries. Here we report on growth rates of indigenous street and garden trees in Grahamstown, South Africa, using two approaches; tree ring counts on increment cores and mean rates from trees of known planting age. Growth equations for both street and garden trees were derived. There was no significant difference in mean growth rates determined via the two methods. For both methods street trees grew approximately 30% slower than trees in gardens.     

Biology and host range of Platyphora semiviridis, a leaf beetle evaluated as a potential biological control agent for Solanum mauritianum in South Africa

The South American tree Solanum mauritianum is a major environmental weed in the high-rainfall regions of South Africa and has been targeted for biological control. Potential agents included five species of the genus Platyphora, which were imported from South America in 1994. Platyphora species associated with Solanaceae reputedly have very specific habitat requirements and host plant preferences in the field. Despite this, host-specificity tests on one species, Platyphora semiviridis, revealed a broad physiological host range. Although laboratory tests showed that P. semiviridis is confined to Solanum species and cannot survive on solanaceous crops outside that genus, it developed on potato and cultivated eggplant (aubergine) as well as on 10 native South African Solanum species. With few exceptions, there were no consistent differences in survival and duration of development on these compared with S. mauritianum. Furthermore, at least six of these non-target species, including potato and eggplant, supported breeding colonies of the beetles in cages. During choice tests in both small and larger cages, P. semiviridis avoided potato but did not consistently discriminate between S. mauritianum, eggplant and six native solanums for larviposition. Despite these findings, P. semiviridis has never been recorded on either potato or eggplant in South America, where it was only observed to feed on S. mauritianum. Although there are several reasons why P. semiviridis is unlikely to attack non-target Solanum species in the field, it will not be released in South Africa because there are other imported agents which have displayed narrower physiological host ranges and which may be more effective.     

Biology, host specificity and risk assessment of the leaf-mining flea beetle, Acallepitrix sp. nov., a candidate agent for the biological control of the invasive tree Solanum mauritianum in South Africa

The South American tree Solanum mauritianum, a major environmentalweed in the high-rainfall regions of SouthAfrica, has proved to be a difficult target forbiological control. Artificially expanded hostranges of candidate agents during quarantinehost-specificity tests, have resulted in therelease of only one agent species which has sofar had a negligible impact on the weed. Thenecessity for additional agents resulted in theimportation of a leaf-mining flea beetle, anunidentified species of Acallepitrix,from Brazil in 1997. No-choice tests inquarantine showed that potential host plantsare confined to the genus Solanum.Although several non-target plants, includingcultivated eggplant (aubergine) and some nativeSouth African Solanum species, sustainedfeeding, oviposition and the development oflarval leaf mines, most of these were inferiorhosts. These results were confirmed by pairedchoice tests, where Acallepitrix sp. nov.displayed significant feeding and ovipositionpreferences for S. mauritianum and where,with few exceptions, more larval leaf mineswere initiated on S. mauritianum.Interpretation of the host-specificity testswas facilitated by a risk assessment matrixwhich suggested that the risk of feeding andoviposition on non-target Solanum plants,including eggplant cultivations, was relativelylow. These and other considerations, such asthe lack of evidence of damage inflicted oncultivated Solanaceae in South America, suggestthat Acallepitrix sp. nov. could beconsidered for release against S. mauritianum in South Africa. However, the results of the host-specificity tests remain ambiguous and until more compelling evidence is obtained from field surveys and open-field trials in Brazil, an application for permission to release the flea beetle in South Africa will not be considered.     

Inflorescence-inhabiting spiders do not threaten the survival and fecundity of Anthonomus santacruzi (Curculionidae), a florivorous biocontrol agent of Solanum mauritianum (Solanaceae) in South Africa

The florivorous weevil Anthonomus santacruzi is being released in South Africa to reduce the reproductive capacity of the invasive tree, Solanum mauritianum. Initiated to allay concerns about biotic interference, our study suggests that inflorescence-inhabiting spiders pose no risk to the survival and proliferation of A. santacruzi populations in the field.     

Fruit nutritional composition and non-nutritive traits of indigenous South African tree species

Frugivorous animals play a major role in dispersing tropical, and to a lesser extent, temperate tree species. In order to attract potential seed dispersers, plants generally offer a reward of fleshy fruit pulp. Criteria for fruit choice by avian frugivores are influenced by a number of non-nutritive (e.g. fruit size and colour) factors; and nutritional composition of the fruit. There is a paucity of nutritional composition and other fruit trait data of indigenous South African fruit. This information is necessary in order to determine which frugivores are likely to ingest which fruits and consequently act as potential seed dispersal agents. This information would provide us with an understanding of the inter-relationships between indigenous fruit and frugivores in South Africa. Consequently nutritional composition was investigated in various indigenous fruit species that avian frugivores feed on. Fruits were collected from 38 indigenous tree species found in KwaZulu-Natal Afromontane and coastal forests. Pulp was freeze-dried to constant mass and then analysed for sugar, lipid and protein content; and for water content determination. Fruit width in this study ranged from 4 mm (Searsia rehmanniana and Trema orientalis) to 40 mm (Annona senegalensis, Ficus sur and Xylotheca kraussiana). Of the fruits examined in this study 29% were black and 43% were red when ripe. Most (84%) fruit species analysed for sugar content were hexose dominant with 50% being fructose and 34% being glucose dominant. Only 16% of the fruit species analysed were sucrose dominant. Fruits in this study were generally observed to be high (mean: 68.1 ± 3.3%; n = 30) in water content; and low in protein and lipid content respectively (mean: 8.2 ± 0.5%; 9.3 ± 2.2%; n = 30) indicating that these fruit species could be considered as nutrient-dilute. Future studies need to determine the nutritional composition of the remaining indigenous South African fruit in order to develop a comprehensive database as well as examining non-nutritive factors.     

Solitary invasive orchid bee outperforms co-occurring native bees to promote fruit set of an invasive Solanum

Our understanding of the effects of introduced invasive pollinators on plants has been exclusively drawn from studies on introduced social bees. One might expect, however, that the impacts of introduced solitary bees, with much lower population densities and fewer foragers, would be small. Yet little is known about the potential effects of naturalized solitary bees on the environment. We took advantage of the recent naturalization of an orchid bee, Euglossa viridissima, in southern Florida to study the effects of this solitary bee on reproduction of Solanum torvum, an invasive shrub. Flowers of S. torvum require specialized buzz pollination. Through timed floral visitor watches and two pollination treatments (control and pollen supplementation) at three forest edge and three open area sites, we found that the fruit set of S. torvum was pollen limited at the open sites where the native bees dominate, but was not pollen limited at the forest sites where the invasive orchid bees dominate. The orchid bee’s pollination efficiency was nearly double that of the native halictid bees, and was also slightly higher than that of the native carpenter bee. Experiments using small and large mesh cages (to deny or allow E. viridissima access, respectively) at one forest site indicated that when the orchid bee was excluded, the flowers set one-quarter as many fruit as when the bee was allowed access. The orchid bee was the most important pollinator of the weed at the forest sites, which could pose additional challenges to the management of this weed in the fragmented, endangered tropical hardwood forests in the region. This specialized invasive mutualism may promote populations of both the orchid bee and this noxious weed. Invasive solitary bees, particularly species that are specialized pollinators, appear to have more importance than has previously been recognized. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Initiation of and solasodine production in hairy root cultures of Solanum mauritianum Scop.

Initiation and establishment of hairy root cultures from leaf or seedling hypocotyl explants of Solanum mauritianum Scop., using six strains of Agrobacterium rhizogenes was attempted. Success was only achieved following hypocotyl inoculation with strain LBA 9402. Transformation frequency was very low, with only one instance out of a possible 90 being recorded. Resultant hairy root cultures grew rapidly and could be maintained using a Murashige and Skoog (1962) medium supplemented with 0.1 g L^–1 myo-inositol and 3% sucrose, either as a solid or liquid culture. Under these conditions, the roots had a solasodine content of 126 g g^–1 DW. Lower levels of solasodine and decreased root growth rates were recorded when the medium strength was reduced by half or 3% glucose substituted for the 3% sucrose.Abbreviations MS Murashige and Skoog's (1962) medium     

不同居群准噶尔无叶豆果实和种子特性及种子萌发差异

研究准噶尔无叶豆(Eremosparton songoricum) 6个居群间果实和种子特性及种子萌发差异, 以揭示异质生境下准噶尔无叶豆果实和种子的生态适应机制。结果显示: 居群间准噶尔无叶豆的植株距离(F = 2.34, p = 0.03)和植株冠幅(F = 8.49, p < 0.01)存在显著差异, 沙漠北缘E、F居群和沙漠腹地C居群(受人类干扰剧烈)的植株距离和植株冠幅高于沙漠腹地A、B、D居群; 居群间准噶尔无叶豆果实和种子的长度、宽度、厚度、重量存在显著差异, 居群E、F和C的大部分参数显著高于其他沙漠腹地居群; 居群间果实多子性(F = 6.96, p < 0.01)也存在显著差异, 居群C的果实多子性最高((32.50 ± 4.79)%); 萌发结果表明, 居群间新鲜的成熟种子萌发不存在显著差异, 且萌发率都低于15%; 所有居群的大部分种子都存在物理性休眠现象, 人为划破种皮能显著提高种子萌发率, 但在低温(15/5 ℃)条件下, 所有居群的种子萌发率都较低, 说明低温抑制了种子萌发; 经人为划破种皮解除物理休眠后, 种子的休眠没有完全释放, 居群C、E和F (大种子居群)的种子萌发率显著高于居群A、B和D (小种子居群) (F = 30.77, p < 0.01), 说明准噶尔无叶豆种子不仅存在物理性休眠现象, 也可能存在生理休眠现象。不同程度的种子复合休眠可能是准噶尔无叶豆不同居群适应古尔班通古特沙漠的重要生存策略。     

Attempts to produce solasodine in callus and suspension cultures of Solanum mauritianum Scop.

Callus cultures of Solanum mauritianum Scop. were initiated from green berry explants on a hormone-free Murashige and Skoog (1962) medium excluding glycine, and containing 0.1 g L^–1 myo-inositol and 3% sucrose. Such cultures contained 10.08±0.59 g g^–1 DW of solasodine, which is equivalent to that in the leaves of mature S. mauritianum plants, but far less than that extracted from the green berries (185 g g^–1 DW). In vitro solasodine productivity could be increased by reducing the strength of the medium by half, substituting 3% glucose for 3% sucrose as carbon source, or by the addition of certain combinations of BA and NAA. Phosphate limitation and alterations in the carbon: nitrogen ratio were not able to increase solasodine productivity. Suspension cultures of S. mauritianum were initiated and maintained in a Murashige and Skoog (1962) medium with the RT vitamins of Khanna and Staba (1968), 0.1 g L^–1 myo-inositol, 3% sucrose and 1 mg L^–1 2,4-D. No solasodine was detectable in these cultures, or slight modifications thereof.Abbreviations BA benzyladenine - NAA naphthaleneacetic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - MS Murashige and Skoog's (1962) medium     

Comparison of LCI studies in South Africa and Germany

This article investigates the possibilities for and potential applications of Life Cycle Assessments (LCA’s) and specifically of Life Cycle Inventories (LCI’s) in developing countries (e.g. South Africa). The situation in South Africa is compared to that prevailing in Germany, a highly developed country. Although South Africa is unique concerning the different degrees of development within the industry, most of the principles discussed in this article can be applied similarly to other developing countries. No significant full LCI studies have yet been performed in South Africa. Although the immediate local needs for the South Africa enonomy are solving labour problems, creating jobs, building houses, the industries should seriously consider performing LCA and related studies for their products. The concept of quality should be extended to include the environmental performance of a product, process or service.     

Distribution of cancer mortality rates by province in South Africa

IntroductionCancer mortality rates are expected to increase in developing countries. Cancer mortality rates by province remain largely unreported in South Africa. This study described the 2014 age standardised cancer mortality rates by province in South Africa, to provide insight for strategic interventions and advocacy.Methods2014 deaths data were retrieved from Statistics South Africa. Deaths from cancer were extracted using 10th International Classification of Diseases (ICD) codes for cancer (C00-C97). Adjusted 2013 mid-year population estimates were used as a standard population. All rates were calculated per 100 000 individuals.ResultsNearly 38 000 (8%) of the total deaths in South Africa in 2014 were attributed to cancer. Western Cape Province had the highest age standardised cancer mortality rate in South Africa (118, 95% CI: 115–121 deaths per 100 000 individuals), followed by the Northern Cape (113, 95% CI: 107–119 per 100 000 individuals), with the lowest rate in Limpopo Province (47, 95% CI: 45–49 per 100 000). The age standardised cancer mortality rate for men (71, 95% CI: 70–72 per 100 000 individuals) was similar to women (69, 95% CI: 68–70 per 100 000). Lung cancer was a major driver of cancer death in men (13, 95% CI: 12.6–13.4 per 100 000). In women, cervical cancer was the leading cause of cancer death (13, 95% CI: 12.6–13.4 per 100 000 individuals).ConclusionThere is a need to further investigate the factors related to the differences in cancer mortality by province in South Africa. Raising awareness of risk factors and screening for cancer in the population along with improved access and quality of health care are also important.