African Olive Research Articles

Can the impacts of invasive African Olive on native Cumberland Plain Woodland plants be mitigated through bioinoculation?

SummaryInvasive plants often impact the abiotic and biotic conditions of the ecosystems they invade. These impacts can persist after the removal of the invader as legacy effects that may hamper restoration. We assessed whether the invasion of Cumberland Plain Woodland in Australia by African Olive impacts the performance of native species through legacy effects. We also tested whether the addition of soil inocula from uninvaded Cumberland Plain Woodland and rhizosphere soils can mitigate the effects of invaded soils on native plant performance. To do this, we grew four native Cumberland Plain Woodland species (Australian Indigo, Climbing Saltbush, Hickory Wattle, Wedge‐leaf Hop‐bush) in mesocosms containing either uninvaded Cumberland Plain Woodland soil, African Olive‐invaded Cumberland Plain Woodland soil or invaded Cumberland Plain Woodland soil inoculated with uninvaded or native rhizosphere soil. We found invaded soils to not consistently impact the growth of the Cumberland Plain Woodland species studied. In invaded soil, Hickory Wattle produced lower above and belowground biomass, Climbing Saltbush produced lower belowground biomass and Australian Indigo had a lower root to shoot ratio compared to plants grown in Cumberland Plain Woodland soil. The nodulation of Australian Indigo did not differ between soil treatments, while that of Hickory Wattle responded positively to inoculation. Our results suggest that the addition of native soil biota may improve the outcomes of ecological restoration projects on a species‐specific basis.

The impacts of invasive African olive on native Australian legumes via altered soil conditions do not persist as legacy effects

The impacts of invasive African olive on native Australian legumes via altered soil conditions do not persist as legacy effects

Decreased diversity and connectivity of endophytic fungal assemblages within cultivated European olive trees compared to their native African counterpart

Host identity and location help shape fungal endophyte assemblages in plants. Hosts act as uptake filters from the environment and closely related hosts in the same location may harbour similar assemblages. We assessed the influence of host identity and geographic location on endophytic fungal assemblages within the native African olive and cultivated European olive in South Africa using high throughput sequencing. As hypothesised, the two hosts were found to share many endophytic species, but alpha diversity was lower within the European olive. The two hosts had significantly dissimilar endophyte assemblages. Distance between sites positively correlated with endophyte assemblage dissimilarities, demonstrating a strong effect of the surrounding environment on endophyte assemblages. African olive individuals had highly connected endophyte assemblages, unlike those within the European olive. Microbiome sharing and disconnected assemblages may have negative impacts on the health of the cultivated host.

Land use change rather than surrounding vegetation affects fungal endophyte assemblages in the African wild olive

ContextLand use change can significantly affect plant-fungal interactions.ObjectivesWe assessed how fungal endophytes within African wild olive (Olea europaea subsp. cuspidata) twigs are influenced by different levels of land use change and differences in surrounding vegetation types.MethodsTwigs were sampled in the Western Cape Province (South Africa) and their fungal endophyte assemblages were characterised using culture-independent DNA metabarcoding. We assessed the effects of land use change (natural, semi-natural and planted (completely transformed)) and differences in surrounding vegetation types (grasses/low-growing plants versus shrubs/trees versus other olives) using fungal endophyte alpha and beta diversity measures. Co-occurrence networks were constructed to assess assemblage connectivity under different scenarios and to identify OTUs of potential ecological significance.ResultsOTU richness, but not abundance, was significantly influenced by both land use change and differences in the surrounding vegetation types. Planted African olives and those surrounded by heterospecific trees harboured the highest OTU richness. Only levels of land use change significantly influenced fungal endophyte assemblage composition. Specifically, fungal assemblages from natural habitats were distinct from those in planted and semi-natural habitats, which were similar to each other. Co-occurrence network analyses revealed that cohesive and species rich networks could only be maintained within the natural habitats.ConclusionThese findings suggest that although the African olive is widespread, the identity and composition of their associated fungal assemblages are particularly sensitive to land use change. This study highlights the importance of conserving natural habitats, not just for the plants, but also for the maintenance of their associated fungal endophytes.

Composition and community structure of Olea ferruginea Royle forests in Jammu and Kashmir, India

ABSTRACT Olea ferruginea Royle is a wild Olive species commonly known as Indian or African Olive. In India, it is distributed in the Northwestern Himalaya, from Jammu and Kashmir to Uttarakhand, at an altitude of up to 2400 m amsl. The present study aims to determine the composition and community structure of Olea L. forests in Jammu and Kashmir, India. During the present study, 21 sites were surveyed from September 2019‒August 2021 and a total of 34 plant species belonging to 32 genera and 22 families were recorded. Fabaceae was the dominant family with five species followed by Moraceae (four species) and Fagaceae, Rosaceae, Malvaceae, Meliaceae, and Salicaceae (two species each). A total of 1333 individuals of trees were recorded including 362 individuals of Olea ferruginea. From the dendrogram resulting from Ward’s cluster analysis of 21 sites based on presence/absence data, five communities were identified on the basis of the Importance Value Index (IVI). The species richness and diversity indices showed great differences from community to community. The present study provides baseline information about the community structure and biological associations of Olea ferruginea.

Proximate and Detergent Fiber Fractions of de-Oiled African Olive (Canarium schweinfurthii Engl.) Residue: A Potential Animal Feedstuff

Proximate and detergent fiber composition of de-oiled African olive (Canarium schweinfurthii) residue were assessed using standard laboratory analytical procedures. Proximate composition showed 17.58 ± 0.21% crude protein, 4.13 ± 0.06% crude fat, 19.99 ± 0.89% crude fiber, 8.11 ± 0.33% ash and 50.20 ± 1.19% soluble carbohydrate. Detergent fiber components were 54.74±0.0745% NDF, 38.35 ± 0.59% ADF, 14.37 ± 0.68% ADL, 23.98 ± 0.10% cellulose and 16.40 ± 0.13% hemicellulose. Quantitative compositions of proximate and detergent fiber fractions were characteristic of roughage. De-oiled African olive pulp residue is relatively fair in protein and a good source of carbohydrate and digestible fiber for animal nutrition.

Antidiabetic Potential and Antioxidant Activity of Olea europaea subsp. Cuspidata (Indian Olive) Seed Extracts.

The aim of the present study was to evaluate the antioxidant and antidiabetic potential of Indian olive seed extracts. Plant seeds were sequentially extracted with n-hexane, chloroform, methanol, and water. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) scavenging and alpha-amylase inhibitory activities of extracts were carried out. Olea europaea methanolic extract (MEOE) and aqueous extract (AEOE) were orally administered to normoglycemic and alloxan-treated diabetic rats so as to determine their hypoglycemic effect. High-performance liquid chromatography (HPLC) analysis showed gallic acid, ferulic acid, quercetin, and vanillic acid in MEOE. It was found that the methanolic and aqueous extracts exhibited the maximum DPPH and alpha-amylase inhibition activities, respectively. MEOE and AEOE exerted a significant decline in the fasting blood sugar in diabetic animals (p < 0.05); however, they did not cause hypoglycemia in nondiabetic animals. Treatment with MEOE and AEOE reduced the aggravated liver and kidney function biomarkers. Aggravated levels of oxidative stress biomarkers including superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), and malondialdehyde (MDA) were restored by treatment with MEOE. Moreover, MEOE improved the count of islets of Langerhans in the pancreas, fatty changes, and enlarged sinusoidal spaces in the liver and necrosis of the glomerulus and tubular cells of the kidney in diabetic rats. This study showed that the African olive seed extract effectively managed experimental diabetes and restored the normal functions and histology of the liver and kidney in diabetic rats through the reduction of oxidative stress.

Assessment of metals content of widely used traditional toothbrushes in Addis Ababa, Ethiopia

ABSTRACT. Traditional toothbrushes are used by the vast majority of people who cannot afford to buy the commercial toothbrush and toothpaste. The traditional toothbrushes are generally obtained from any slim woody part of a toothbrush tree. The main purpose of this study was to determine selected metals (Ca, Fe, Mg, Al, Cu, Cr, Ni, Zn, Mn, Pb, and Cd) in traditional toothbrushes obtained from three plants including Ligustrum vulgare L., Phoenix reclinata and Olea africana, which are extensively used in Addis Ababa, Ethiopia, by using microwave plasma-atomic emission spectroscopy (MP-AES) after wet digestion. Recoveries of the metals in spiked samples varied from 90.4–107%. The overall mean concentrations determined (mg/kg, dry weight) were in the ranges of Ca (4267–36514) &gt; Fe (131–318) &gt; Al (81.6 –224) &gt; Mg (45.6–122) &gt; Zn (27.2–175) &gt; Mn (20.1–29) &gt; Cu (6.6–20.3) &gt; Cr (6.7–8.9) &gt; Ni (2.6–7.9). Analysis of variance at 95% indicated significant differences in the metals’ contents of three toothbrushes. The results indicated that the selected traditional toothbrushes are good sources of essential metals and free from Pb and Cd. Therefore, the investigated Ethiopian traditional toothbrushes are found to be safe for human use.&#x0D; &#x0D; KEY WORDS: Metal contents, Traditional toothbrushes, Wild privet (Ligustrum vulgare), Wild date palm (Phoenix reclinata), African wild olive (Olea africana), Ethiopia&#x0D; &#x0D; Bull. Chem. Soc. Ethiop. 2021, 35(2), 257-272.&#x0D; DOI: https://dx.doi.org/10.4314/bcse.v35i2.4

Survey of Trunk Pathogens in South African Olive Nurseries.

Several fungal trunk pathogens are associated with olive trunk diseases in South Africa. Little is known regarding the inoculum sources of these pathogens in the olive industry, and no specific management strategies are in place. The aim of this study was to investigate the status of olive nurseries in South Africa, with regard to the presence of trunk pathogens in olive plant material, to determine whether nursery material can be considered inoculum sources contributing to long-distance dispersal of these pathogens. Isolations were made from asymptomatic cuttings from mother blocks (stage 1), asymptomatic and symptomatic rooted cuttings (stage 2), and 1- to 2-year-old trees (stage 3) of eight cultivars in two nurseries. Known olive trunk pathogens of Nectriaceae, Diaporthaceae, Botrysphaeriaceae, Togniniaceae, Phaeomoniellaceae, and Pleurostomataceae were recovered. Neofusicoccum australe was detected in a single stage 1 cutting. Stage 3 material showed the highest incidence of fungi from these families, with Pleurostoma richardsiae having the highest incidence in both nurseries (82.2 and 36.7% of the 1- to 2-year-old trees). Phaeoacremonium parasiticum was present in 28.9% of the trees from one nursery (stage 3). The remaining pathogens occurred in ≤13.3% of the material. These results indicate that nursery propagation material from mother blocks harbors low levels of trunk pathogens and that additional infections occur during the nursery process. Management strategies should focus on the prevention and elimination of infections in mother blocks as well as during the propagation process to ensure that pathogen-free material is delivered to producers.

‘The child that tiire doesn't give you, God won't give you either.’ The role of Rotheca myricoides in Somali fertility practices

ABSTRACTThe paper introduces the Baanashada Dumarka, a Somali fertility therapy carried out by a spirit medium, known locally as ‘Alaqad. Baanashada is aimed at women whose fertility issues are believed to be caused by spirits. The study also explores a component of the Baanashada, namely, the use of tiire (Rotheca myricoides), or the butterfly bush. Although Rotheca myricoides is known to possess a number of medicinal components as confirmed by studies of modern science, so far, there exist no studies on its potential (or lack of) fertility effects. Hence, the alleged fertility benefits of the butterfly bush need examining. The author is aware of at least one recent case that a Somali woman from Europe died of herbs placed in her cervix by a traditional healer in Somaliland. This piece of information indicated not only the role of herbal medicine in fertility practices, but also the popularity of traditional reproductive medicine beyond border, class or educational background. Yet, current research into Somali women's health focuses mainly on Female Genital Mutilation (FGM), examined often without the context of wider cultural practices. This paper, however, suggests that rituals, beliefs and material culture play a paramount role in women's practices. For example, as explored elsewhere, the wagar, a wooden and sacred object made of the African olive, is critical for fertility practices. The current paper illuminates further the significance of reproduction practices in Somali society and the potential continuity of traditions associated with the perpetuation of kinship. It concludes that fertility rituals are part of a wider context of interaction with sacred landscapes, objects and archaeological sites, often associated with past legends in the Horn of Africa.

Ecological effects of increasing time since invasion by the exotic African olive (Olea europaea ssp. cuspidata) on leaf-litter invertebrate assemblages

Invasive African olive, Olea europaea ssp. cuspidata (Wall. ex G.Don) Cif., forms increasingly dense stands between initial and mature stages of invasion, leading to a progressive decline in native plant diversity. Here, we examined the response of leaf-litter invertebrates to increasing time since olive invasion. We compared invertebrate assemblages among early-stage olive (0–7 years since invasion, scattered olive shrubs and seedlings in native woodland), mature olive (>15 years, uniform olive stands dominated by multi-trunked trees) and uninvaded native grassy woodland habitats (both mature stands and edges) in a critically endangered ecological community of south-eastern Australia. Invertebrate species richness was significantly reduced in mature olive compared with early-stage olive and mature native woodland habitats. Species richness did not differ significantly between early-stage olive habitat and mature native woodland, demonstrating resistance in species richness to initial invasion. Invertebrate species composition of native woodlands differed significantly from both mature olive and early-stage olive habitats, demonstrating a lack of resistance in species composition to initial olive invasion. Compositional differences were principally driven by reduced abundances within Coleoptera, Hymenoptera and Polyxenida in mature olive habitat compared with mature native woodland. These changes were significantly correlated with an increase in bare ground, plant canopy cover and litter depth, and higher moisture and lower temperature within leaf litter, in mature olive habitat. Our findings show that negative ecological impacts of invasive African olive extend beyond plants to leaf-litter invertebrate assemblages and that significant impacts on invertebrate species assemblage composition occur early in the invasion process.

Evaluating Production Performance of Tigray Highland Sheep Supplemented with Air Dried Foliages of African Wild Olive and Red Thorn: A Case Study of Carcass Production

An experiment was conducted at Wukro St. Mary Agricultural, Technical, Vocational Education and Training College to determine effect of feeding foliages from African wild olive and Red thorn on growth performance and carcass production of Tigray Highland sheep and to assess their economic benefits. Chemical composition and supplementation effect of foliages of these indigenous tree species on growth performance of Tigray Highland sheep is available on line. Including air dried foliages of the multipurpose trees as protein supplement to grass hay improved carcass production. Supplemented sheep had significantly (P<0.05) higher slaughter weight, empty body weight, hot carcass weight and dressing percentage on slaughter weight basis than the control treatment. It was economically feasible to poor smallholder sheep owners in the area, but supplementing T4 (mixed air dried foliages) was found as cost-effective with its high net income. The results obtained indicated that feeding foliages from the multipurpose trees alone or mixing at different proportions had potential as protein supplement with less expense.

An ecological and evolutionary perspective on the parallel invasion of two cross-compatible trees.

Invasive trees are generally seen as ecosystem-transforming plants that can have significant impacts on native vegetation, and often require management and control. Understanding their history and biology is essential to guide actions of land managers. Here, we present a summary of recent research into the ecology, phylogeography and management of invasive olives, which are now established outside of their native range as high ecological impact invasive trees. The parallel invasion of European and African olive in different climatic zones of Australia provides an interesting case study of invasion, characterized by early genetic admixture between domesticated and wild taxa. Today, the impact of the invasive olives on native vegetation and ecosystem function is of conservation concern, with European olive a declared weed in areas of South Australia, and African olive a declared weed in New South Wales and Pacific islands. Population genetics was used to trace the origins and invasion of both subspecies in Australia, indicating that both olive subspecies have hybridized early after introduction. Research also indicates that African olive populations can establish from a low number of founder individuals even after successive bottlenecks. Modelling based on distributional data from the native and invasive range identified a shift of the realized ecological niche in the Australian invasive range for both olive subspecies, which was particularly marked for African olive. As highly successful and long-lived invaders, olives offer further opportunities to understand the genetic basis of invasion, and we propose that future research examines the history of introduction and admixture, the genetic basis of adaptability and the role of biotic interactions during invasion. Advances on these questions will ultimately improve predictions on the future olive expansion and provide a solid basis for better management of invasive populations.

Recovery after African Olive invasion: can a ‘bottom‐up’ approach to ecological restoration work?

SummaryAfrican Olive (Olea europaea ssp. cuspidata) is a densely crowned evergreen small tree, native to eastern Africa that is highly invasive in areas where it has been introduced, including Hawaii and Australia. Invasion by African Olive threatens Cumberland Plain Woodland, a critically endangered grassy eucalypt woodland from western Sydney, Australia, through the formation of a dense mid‐canopy excluding the regeneration of native species. We established a 3‐year field experiment to determine the effectiveness of direct seeding and fire, as techniques for early stage restoration of a 2 ha historically cleared and degraded Cumberland Plain Woodland site after the removal of African Olive. Direct seeding was able to re‐establish a native perennial grass cover which was resistant to subsequent weed invasion and could be managed as an important first stage in woodland restoration with fire and selective herbicide. Fire was able to stimulate some germination of colonising native species from the soil seed bank after 15 years of African Olive invasion; however, germination and establishment of native shrubs from the applied seed mix was poor. We propose a ‘bottom‐up’ model of ecological restoration in such highly degraded sites that uses a combination of direct seeding and stimulation of the soil seed bank by fire, which could be applicable to other degraded grassy woodland sites and plant communities.

Sequence analysis of single-copy genes in two wild olive subspecies: nucleotide diversity and potential use for testing admixture.

The wild olive distribution extends from the Mediterranean region to south Asia and Austral Africa. The species is also invasive, particularly in Australia. Here, we investigated the sequence variation at five nuclear single-copy genes in 41 native and invasive accessions of the Mediterranean and African olive subspecies. The nucleotide diversity was assessed and the phylogenetic relationships between alleles were depicted with haplotype networks. A Bayesian clustering method (STRUCTURE) was applied to identify the main gene pools. We found an average of 18.4 alleles per locus. Native Mediterranean and African olives only share one allele, which testifies for ancient admixture on the Red Sea hills. The presence of divergent alleles in the Mediterranean olive, as well as the identification of two main genetic clusters, suggests a complex origin with two highly differentiated gene pools from the eastern and western Mediterranean that recently admixed. In the invasive range, relatively high nucleotide diversity is observed as a consequence of the introduction of alleles from two subspecies. Our data confirm that four invasive individuals are early-generation hybrids. Finally, the utility of single-copy gene sequences in olive population genomic and phylogenetic studies is briefly discussed.

Olive Schreiner, Epistolary Practices and Microhistories

ABSTRACTFocusing on the letters of the South African feminist writer and social theorist Olive Schreiner (1855–1920), this article explores Schreiner's strategic uses of letter-writing as a key tool in her work as a cultural entrepreneur in a number of different social and political contexts. In advocating a microhistory approach which recognizes that macro and micro are interconnected and should be seen as lenses of perspective rather than as separate spheres, we examine various strands of Schreiner's ‘cultural project’ and consider how her epistolary activities articulated and furthered this.

History of the invasive African olive tree in Australia and Hawaii: evidence for sequential bottlenecks and hybridization with the Mediterranean olive

Humans have introduced plants and animals into new continents and islands with negative effects on local species. This has been the case of the olive that was introduced in Australia, New Zealand and Pacific islands where it became invasive. Two subspecies were introduced in Australia, and each successfully invaded a specific area: the African olive in New South Wales (NSW) and the Mediterranean olive in South Australia. Here, we examine their origins and spread and analyse a large sample of native and invasive accessions with chloroplast and nuclear microsatellites. African olive populations from the invaded range exhibit two South African chlorotypes hence supporting an introduction from South Africa, while populations from South Australia exhibit chlorotypes of Mediterranean cultivars. Congruently, nuclear markers support the occurrence of two lineages in Australia but demonstrate that admixture took place, attesting that they hybridized early after introduction. Furthermore, using an approximate Bayesian computation framework, we found strong support for the serial introduction of the African olive from South Africa to NSW and then from NSW to Hawaii. The taxon experienced successive bottlenecks that did not preclude invasion, meaning that rapid decisions need to be taken to avoid naturalization where it has not established a large population yet.

The Transnational Circulation of Dissent: Olive Schreiner and the Colonial Counter-flows of Unitarian Freethinking

Most work on pioneering South African novelist Olive Schreiner foregrounds the shaping of her work by the relationship between Great Britain and South Africa, and Schreiner’s own shuttling between those two countries. Elleke Boehmer’s call for “cross-national” readings of “anticolonial interdiscursivity” challenges us to examine Schreiner’s intellectual development, particularly her religious freethinking, her literary originality, and her political radicalism in a more globally transnational light. This paper picks up that challenge by tracing some of the colonial counterflows of Unitarian dissent from Rammohun Roy in early nineteenth -century Bengal through Ralph Waldo Emerson in mid-nineteenth-century Boston to Schreiner and the formal establishment of Unitarianism in Cape Town.

Ecological impacts of invasive African olive (Olea europaea ssp. cuspidata) in Cumberland Plain Woodland, Sydney, Australia

AbstractAfrican olive (Olea europaea ssp. cuspidata) is a small evergreen tree which has become highly invasive at a landscape scale in the western Sydney and Hunter Valley regions of New South Wales, Australia. African olive invasion results in the formation of a dense and permanent mid‐canopy in grassy woodland vegetation. We investigated the relationship between African olive and native species establishment, abundance and diversity, using field surveys and a manipulative shading experiment. There were 78% fewer native species beneath African olive canopy in the field compared to uninvaded woodland sites. The shading experiment showed that simulated dense African olive shade levels produced the lowest dry weight for the three native species studied, with simulated canopy edge light providing optimal conditions for the native shrub Bursaria spinosa and African olive. Dense African olive shade levels produced the highest mortality rate for native species; however, African olive was able to maintain an 88% survival rate under dense canopy shade. This study confirms the adaptability of African olive and its capacity to decrease native plant diversity and substantially modify native vegetation at the community level.

Seed ecology of the invasive woody plant African Olive (Olea europaea subsp. cuspidata): implications for management and restoration

Knowledege of the seed ecology of invasive exotic species, including soil seedbank dynamics, is essential to understanding key factors in successful invasion and in identifying management opportunities. African Olive, Olea europaea L. subsp. cuspidata, is an exotic invasive woody plant in Hawaii, Norfolk Island and eastern Australia, and is now well established in the Cumberland Plain region of western Sydney, Australia. In the present study, the key aspects of the seed ecology of African Olive were determined for populations in western Sydney. Extracted seed germinated at a wide range of temperatures, consistent with tolerance of a wide range of climatic conditions. A seed-burial experiment indicated a slow decrease in viability down to 70.3% during the first year, followed by a rapid decline down to 14.7% in the second year. Probit analysis indicated that under field conditions, seed persistence in the soil was ~29 months (2.4 years). In situ germination was low (3.3%) and did not occur until the mechanical constriction of the endocarp was released through decomposition. The woody seed endocarp was found to be permeable to water, indicating that physical dormancy was not imposed by providing a barrier to water uptake. Within its invasive range, African Olive produces abundant seed. However, the rapid loss of viability of soil-stored seed results in a narrow window of opportunity for germination. The short persistence of seed in the soil may provide an opportunity for managers to achieve control of African Olive once mature plants are removed.