Acacia Drepanolobium Research Articles

Ethnobotany of traditional cosmetics among the Oromo women in Madda Walabu District, Bale Zone, Southeastern Ethiopia

Traditional cosmetics play a significant role in the cultural practices and personal hygiene of many ethnic groups worldwide. The Oromo, an indigenous community in Ethiopia, has a rich history of utilizing local plants for cosmetic purposes. However, the use of plants as traditional cosmetics has only been poorly investigated as more emphasis was given to traditional medicines. The study thus aimed to identify and document plant species, and parts used in traditional cosmetics and associated knowledge, and practices among Oromo women in the Madda Walabu district, Southeastern Ethiopia. A total of 150 Oromo women were interviewed to gather ethnobotanical information including the plant species used for cosmetics, their preparation methods, and their applications. Ethnobotanical indices were computed to determine the most important species used by the women. A total of 48 plant species belonging to 31 families used as sources of traditional cosmetics were recorded. Most of these plants were trees. Leaves were the most commonly used plant part in traditional cosmetics, and maceration and decoction were the most common preparation methods applied to prepare traditional cosmetics. Topical application of traditional cosmetics was the most common, while oral infusions were rarely reported type of administration. All categories had high informant consensus factor (ICF) values, ranging from 0.80 to 0.98. The highest ICF value was found for skin treatment, followed by the hair, and face mask. Overall, Commiphora habessinica, Gnidia stenophylla, Kalanchoe lanceolata, Mimusops kummel, Sesamothamnus rivae, Terminalia brownii, T. laxiflora, Acacia drepanolobium, A. mellifera, and Aloe citrina were the most frequently cited and culturally important plants by Oromo women for traditional cosmetics in the area. The study highlights the importance of local plant resources for maintaining cultural practices and personal hygiene. However, the cultural heritage associated with traditional cosmetics is facing threats from various factors. Therefore, a continuous effort to document and disseminate knowledge about traditional cosmetics practices to ensure their preservation and transmission and awakening younger generations about the importance of traditional cosmetics and their role in cultural heritage is crucial.

Assessment of plant ecological variability and heavy metal accumulation potential in naturally growing plant species of Pakhar bauxite mine site, Jharkhand, India

Abandoned bauxite mine (ABM) soil generally contains an unacceptable number of heavy metals (HMs), causing several ecological and environmental issues. The present study was conducted with a similar objective to assess the HM accumulation potential of the naturally growing plant species from Pakhar ABM site. Vegetation communities were studied using quadrat methods for plant species at both ABM and the control site (near the ABM site). A total of 21 (9 at the ABM site and 12 at the control site) plant species were recorded in the present study belonging to 10 families. Vegetation study revealed that the dominant plant species were Ammophila arenaria and Lantana camara at ABM site and Lantana camara at the control site. The concentration of HMs in soil at the ABM site, were 66180.00 mg kg−1 Al, 62.20 mg kg−1 Cr, 22.60 mg kg−1 Cu, 346800.00 mg kg−1 Fe, 780.80 mg kg−1 Mn, and 39.80 mg kg−1 Zn while in the soil of site located nearby taken as the control showed 56500.00 mg kg−1 Al, 4.40 mg kg−1 Cu, 51120.00 mg kg−1 Fe, 58.20 mg kg−1 Mn, 13.00 mg kg−1 Zn. Ammophila arenaria, Miscanthus sinensis, Acacia drepanolobium and Rumex pulcher exhibited the highest metal accumulation at the ABM site, while Ocimum campechianum, Lantana camara, Panicum virgatum L., Euphorbia hirta and Holcus lanatus, Cerastium glomeratum thuill and Shorea robusta exhibited the highest metal accumulation at control site. Plant Lantana camara showed considerable TF values for Pb, Al and Fe, from the ABM soil while Shorea robusta showed high TF values for Al, Cu, Zn, and Fe from the control soil. The BAF for Cu, Mn and Zn from ABM soil were observed in Acacia drepanolobium whereas Cerastium glomeratum thuill exhibited maximum BAF values for Zn and Cu from control soil.

Symbiotic ant traits produce differential host-plant carbon and water dynamics in a multi-species mutualism.

Cooperative interactions may frequently be reinforced by "partner fidelity feedback," in which high- or low-quality partners drive positive feedbacks with high or low benefits for the host, respectively. Benefits of plant-animal mutualisms for plants have been quantified almost universally in terms of growth or reproduction, but these are only two of many sinks to which a host-plant allocates its resources. By investigating how partners to host-plants impact two fundamental plant resources, carbon and water, we can better characterize plant-partner fidelity and understand how plant-partner mutualisms may be modulated by resource dynamics. In Laikipia, Kenya, four ant species compete for Acacia drepanolobium host-plants. These ants differ in multiple traits, from nectar consumption to host-plant protection. Using a 5-year ant removal experiment, we compared carbon fixation, leaf water status, and stem non-structural carbohydrate concentrations for adult ant-plants with and without ant partners. Removal treatments showed that the ants differentially mediate tree carbon and/or water resources. All three ant species known to be aggressive against herbivores were linked to benefits for host-plant resources, but only the two species that defend but do not prune the host, Crematogaster mimosae and Tetraponera penzigi, increased tree carbon fixation. Of these two species, only the nectivore C. mimosae increased tree simple sugars. Crematogaster nigriceps, which defends the tree but also castrates flowers and prunes meristems, was linked only to lower tree water stress approximated by pre-dawn leaf water potential. In contrast to those defensive ants, Crematogaster sjostedti, a poor defender that displaces other ants, was linked to lower tree carbon fixation. Comparing the effects of the four ant species across control trees suggests that differential ant occupancy drives substantial differences in carbon and water supply among host trees. Our results highlight that ant partners can positively or negatively impact carbon and/or water relations for their host-plant, and we discuss the likelihood that carbon- and water-related partner fidelity feedback loops occur across ant-plant mutualisms.

Demographic consequences of mutualism disruption: Browsing and big-headed ant invasion drive acacia population declines.

Across the globe, biological invasions have disrupted mutualisms, producing reverberating consequences for ecosystems. Although invasive species frequently trigger mutualism disruptions, few studies have quantified the demographic mechanisms by which mutualism breakdown may generate population effects. In a Kenyan savanna, the invasive big-headed ant (Pheidole megacephala) has disrupted a foundational mutualism between the monodominant whistling-thorn tree (Acacia drepanolobium) and native ants (Crematogaster spp.) that deter browsing by large mammalian herbivores. We conducted experiments to quantify the demographic consequences of this mutualism disruption in the presence and absence of large mammalian herbivores. Invasion by P. megacephala exacerbated population declines of A. drepanolobium, primarily through decreased survival and reproduction of adult trees. However, these fitness reductions were small compared to those resulting from the presence of large mammalian herbivores, which negatively impacted growth and survival. Contrary to expectation, the expulsion of metabolically costly Crematogaster mutualists by P. megacephala did not result in higher population growth rates for trees protected from large mammalian herbivores. Our results suggest that invasive P. megacephala may impose a direct metabolic cost to trees exceeding that of native mutualists while providing no protection from browsing by large mammalian herbivores. Across landscapes, we expect that invasion by P. megacephala will reduce A. drepanolobium populations, but that the magnitude and demographic pathways of this effect will hinge on the presence and abundance of browsers.

A soil‐nesting invasive ant disrupts carbon dynamics in saplings of a foundational ant–plant

Abstract Nearly every terrestrial ecosystem hosts invasive ant species, and many of those ant species construct underground nests near roots and/or tend phloem‐feeding hemipterans on plants. We have a limited understanding of how these invasive ant behaviours change photosynthesis, carbohydrate availability and growth of woody plants. We measured photosynthesis, water relations, carbohydrate concentrations and growth for screenhouse‐reared Acacia drepanolobium saplings on which we had manipulated invasive Pheidole megacephala ants and native Ceroplastes sp. hemipterans to determine whether and how soil nesting and hemipteran tending by ants affect plant carbon dynamics. In a field study, we also compared leaf counts of vertebrate herbivore‐excluded and ‐exposed saplings in invaded and non‐invaded savannas to examine how ant invasion and vertebrate herbivory are associated with differences in sapling photosynthetic crown size. Though hemipteran infestations are often linked to declines in plant performance, our screenhouse experiment did not find an association between hemipteran presence and differences in plant physiology. However, we did find that soil nesting by P. megacephala around screenhouse plants was associated with >58% lower whole‐crown photosynthesis, >31% lower pre‐dawn leaf water potential, >29% lower sucrose concentrations in woody tissues and >29% smaller leaf areas. In the field, sapling crowns were 29% smaller in invaded savannas than in non‐invaded savannas, mimicking screenhouse results. Synthesis. We demonstrate that soil nesting near roots, a common behaviour by Pheidole megacephala and other invasive ants, can directly reduce carbon fixation and storage of Acacia drepanolobium saplings. This mechanism is distinct from the disruption of a native ant mutualism by P. megacephala, which causes similar large declines in carbon fixation for mature A. drepanolobium trees. Acacia drepanolobium already has extremely low natural rates of recruitment from the sapling to mature stage, and we infer that these negative effects of invasion on saplings potentially curtail recruitment and reduce population growth in invaded areas. Our results suggest that direct interactions between invasive ants and plant roots in other ecosystems may strongly influence plant carbon fixation and storage.

Browsing wildlife and heavy grazing indirectly facilitate sapling recruitment in an East African savanna.

Management of tree cover, either to curb bush encroachment or to mitigate losses of woody cover to over-browsing, is a major concern in savanna ecosystems. Once established, trees are often "trapped" as saplings, since interactions among disturbance, plant competition, and precipitation delay sapling recruitment into adult size classes. Saplings can be directly suppressed by wildlife browsing and competition from adjacent plants, and indirectly facilitated by grazers, such as cattle, which feed on neighboring grasses. Yet few experimental studies have simultaneously quantified the effects of cattle and wildlife on sapling growth, particularly over long time scales. We used a series of replicated 4-ha herbivore-manipulation plots to investigate the net effects of wildlife and moderate cattle grazing on Acacia drepanolobium sapling growth over 10years that encompassed extended wet and dry periods. We also simulated more intense cattle grazing using grass removal treatments (0.5-m radius around saplings), and we quantified the role of intraspecific tree competition using neighborhood tree surveys (trees within a 3-m radius). Wildlife, which included elephants, had a positive effect on sapling growth. Wildlife also reduced neighbor tree density during the 10-yr study, which likely caused the positive effect of wildlife on saplings. Although moderate cattle grazing did not affect sapling growth, grass removal treatments simulating heavy grazing increased sapling growth. Both grass removal and neighbor tree effects on saplings were strongest during above-average rainfall years following drought. This highlights that livestock-driven reductions in grass cover and catastrophic wildlife damage to trees during droughts present a need, or an opportunity, for targeted management of sapling growth and woody plant cover during ensuing wet periods.

Naïve plant communities and individuals may initially suffer in the face of reintroduced megafauna: An experimental exploration of rewilding from an African savanna rangeland.

Excluding large native mammals is an inverse test of rewilding. A 25-year exclosure experiment in an African savanna rangeland offers insight into the potentials and pitfalls of the rewilding endeavor as they relate to the native plant community. A broad theme that has emerged from this research is that entire plant communities, as well as individual plants, adjust to the absence of herbivores in ways that can ill-prepare them for the return of these herbivores. Three lines of evidence suggest that these "naïve" individuals, populations, and communities are likely to initially suffer from herbivore rewilding. First, plots protected from wild herbivores for the past 25 years have developed rich diversity of woody plants that are absent from unfenced plots, and presumably would disappear upon rewilding. Second, individuals of the dominant tree in this system, Acacia drepanolobium, greatly reduce their defences in the absence of browsers, and the sudden arrival of these herbivores (in this case, through a temporary fence break), resulted in far greater elephant damage than for their conspecifics in adjacent plots that had been continually exposed to herbivory. Third, the removal of herbivores favoured the most palatable grass species, and a large number of rarer species, which presumably would be at risk from herbivore re-introduction. In summary, the native communities that we observe in defaunated landscapes may be very different from their pre-defaunation states, and we are likely to see some large changes to these plant communities upon rewilding with large herbivores, including potential reductions in plant diversity. Lastly, our experimental manipulation of cattle represents an additional test of the role of livestock in rewilding. Cattle are in many ways ecologically dissimilar to wildlife (in particular their greater densities), but in other ways they may serve as ecological surrogates for wildlife, which could buffer ecosystems from some of the ecological costs of rewilding. More fundamentally, African savannah ecosystems represent a challenge to traditional Western definitions of "wilderness" as ecosystems free of human impacts. We support the suggestion that as we "rewild" our biodiversity landscapes, we redefine "wildness" in the 21st Century to be inclusive of (low impact, and sometimes traditional) human practices that are compatible with the sustainability of native (and re-introduced) biodiversity.

Woody Species Composition, Structure and Regeneration Status in Higelely Dry Forest, Eastern Ethiopia: Implication for Conservation Priority

Dry forests are potentially contributed for the local community livelihood, microclimate stability and biodiversity conservation. However, appropriate emphasis has not given for its sustainability management. Our study aims to study the woody species diversity, vegetation structure, and recruitment and regeneration status in Higelely dry forest of Somali National Regional State of Ethiopia for the purpose of conservation priority. Systematic sampling following the transect lines and sample plots employed to collect all necessary data. Data were analyzed using access software which was designed for the purpose of forest genetic resource conservation database and data analysis tool. Forty two woody species belongs to 21 genera and 15 families were recorded. The richest families were Fabaceae and Burseraceae (represented by 11 and 7 species each). 1112.97 individuals of woody species per ha was recorded in Higelely forest. Acacia oerfota and Acacia mellifera were the top specie with higher stem numbers per ha. More than 67% of the individuals in the forest had DBH/DSH ≤ 7.5 cm and 90% of the individuals had a height ≤ 5 m. The most ecologically important species in Higelely forest were Acacia oerfota, Acacia mellifera, and Acacia bussie. Whereas, Ipomoea donaldsonii, Commiphora africana, and Acacia drepanolobium were the most threatened species in all criteria’s of IVI, population structure and regeneration status and are the first prioritized for conservation measures. The total density of 1047.3 seedling and 3033.77 sapling individuals per ha was recorded in Higelely forest. In general, the vegetation structure, population recruitment and regeneration status of some species indicates, Higelely forest is under poor conservation status. Therefore, for the conservation of woody species in Higelely dry forest, appropriate conservation measures such as in-situ (to allow natural regeneration) and cold room seed storage methods are recommended.

Frenemy at the gate: Invasion by Pheidole megacephala facilitates a competitively subordinate plant ant in Kenya

Biological invasions can lead to the reassembly of communities and understanding and predicting the impacts of exotic species on community structure and functioning are a key challenge in ecology. We investigated the impact of a predatory species of invasive ant, Pheidole megacephala, on the structure and function of a foundational mutualism between Acacia drepanolobium and its associated acacia-ant community in an East African savanna. Invasion by P. megacephala was associated with the extirpation of three extrafloral nectar-dependent Crematogaster acacia ant species and strong increases in the abundance of a competitively subordinate and locally rare acacia ant species, Tetraponera penzigi, which does not depend on host plant nectar. Using a combination of long-term monitoring of invasion dynamics, observations and experiments, we demonstrate that P. megacephala directly and indirectly facilitates T. penzigi by reducing the abundance of T. penzigi's competitors (Crematogaster spp.), imposing recruitment limitation on these competitors, and generating a landscape of low-reward host plants that favor colonization and establishment by the strongly dispersing T. penzigi. Seasonal variation in use of host plants by P. megacephala may further increase the persistence of T. penzigi colonies in invaded habitat. The persistence of the T. penzigi-A. drepanolobium symbiosis in invaded areas afforded host plants some protection against herbivory by elephants (Loxodonta africana), a key browser that reduces tree cover. However, elephant damage on T. penzigi-occupied trees was higher in invaded than in uninvaded areas, likely owing to reduced T. penzigi colony size in invaded habitats. Our results reveal the mechanisms underlying the disruption of this mutualism and suggest that P. megacephala invasion may drive long-term declines in tree cover, despite the partial persistence of the ant-acacia symbiosis in invaded areas.

Browsing impacts on Acacia drepanolobium Sjostedt and associated ant guilds in Ol Pejeta Conservancy, Kenya.

The numbers of Acacia drepanolobium trees are declining over much of Africa and large mammals particularly more prone and vulnerable to loss of habitat owing to human settlement encroachment. In Ol pejeta conservancy a sanctuary for the protection of the endangered black rhino, there is significant browse and vegetation pressure on the habitat particularly on the Acacia drepanolobium tree population. This study aimed to investigate the Acacia drepanolobium and ants’ interaction under different browsing intensities, determine effect of prescribed burnings on Crematogaster ants and Acacia drepanolobium interaction, investigate the tenancy dynamics of ants under varying morphological characteristics of Acacia drepanolobium trees, and finally to determine if Crematogaster ants’ communities/ colonization on Acacia drepanolobium change over time. Twelve (12) randomly chosen plots (keyed in a waypoint on the GPS) with fifty or more Acacia drepanolobium trees were studied for the study as follows, two (2) in a Chimpanzee Sanctuary where elephant, giraffe and rhino are excluded (control), six (6) in the reserve and four (4) in the Ranch. Two (2) plots treated with prescribed burning (fire) were compared with two un-burnt plots. All data collected was fed and entered into Excel spreadsheet and Statistical Package for the Social Science version 20 for analysis. The data were then processed into quantitative tables to give a comparative analysis for response obtained. Size class distributions of the reserve, Ranch and control were compared by means of Analysis of Variance (ANOVA) and other relevant parametric statistics. The result shows that in Ol pejeta conservancy browsing levels has statistically significant effect on Crematogaster ants and Acacia drepanolobium interaction. There was a strong and notable distinction between the four acacia ant species in the overall extends and levels of tenancy while responding to varied browsing pressures; Crematogaster mimosae and Tetraponera penzigi were found to be the most abundant/frequently observed ant species occupying trees in the reserve where there is intensive browsing (Reserve) and the ranch with medium browsing intensity. From this research experimental evidence explains the ability of trees to re-induce greater spine and gall numbers and that ant tenancy in A. drepanolobium is influenced by the tree’s morphological characteristics. The findings and results also indicated that prescribed burning significantly affected the type of ant inhabiting the A. drepanolobium tree. Going by the results of this paper, it was concluded that this mutualism is a key component of Ol pejeta biodiversity and ecosystem function. The study recommends that the results in this research should be used in determining ecological factors that influence conservation sustainability and predict the consequences of heavy browsing pressure, morphological characteristics and prescribed burning on the health of Acacia drepanolobium.

The effects of bush control methods on encroaching woody plants in terms of die-off and survival in Borana rangelands, southern Ethiopia

A study on the effect of bush control methods on encroaching woody species, namely Acacia drepanolobium, Acacia mellifera and Acacia reficiens was conducted for a 2 years’ time. A 3 ha of land was divided into two plots. Each replication with an area of 300 m × 50 m was again sub-divided into six plots (each 50 m × 50 m) to accommodate six treatments. Bush control treatments were assigned randomly to the plots and replicated two times across sites of similar topography. During the post-treatment period, responses of woody species to different treatments in terms of mortality and coppicing were monitored. Data was analysed using R software and Tukey’s studentized range tests for comparisons of means. The applied treatments significantly influenced (P < 0.05) encroaching woody species. The finding showed that five out of the six bush control treatments greatly promoted woody mortality, however with species-specific differences. The stem-burning, tree cutting with fire–browse combination, cutting and fire, cutting and browsing, and cutting treatments greatly increased species mortality compared to the control treatment. Responses due to treatment effect also varied significantly (P < 0.05) among encroaching woody species. Accordingly, mortality was higher in A. reficiens than in the other two species, indicating that A. reficiens is greatly susceptible to the applied treatments. The significant finding was that woody species exhibited greater mortality in response to selective cutting/thinning and post-management techniques. Post-thinning management measures would sustain savanna ecology, if implemented at certain intervals.

Woody Encroachment Extent and Its Associated Impacts on Plant and Herbivore Species Occurrence in Maswa Game Reserve, Tanzania

Habitat degradation caused by woody plant encroachment has been a common phenomenon in savanna ecosystems. An increasing woody plant cover in open grassland reduces grazing grounds and, consecutively, impacts mammalian herbivores, but structural changes and their associated impact have rarely been assessed and quantified. We analyzed the extent of woody plant encroachment via remote sensing and used transects and plots to assess encroaching woody plant species and their associated impacts on herbaceous plant and herbivore species in Maswa Game Reserve, Tanzania. We found that woody plant cover had increased by 0.5% to 2.6% per annum over the last thirty years, while in other parts of the park it has decreased by 0.5% to 1.5% per annum. Acacia drepanolobium was the dominant encroaching woody species, and the number of stems in heavily encroached sites was seven times and three times higher than in open grassland and at medium encroached sites, respectively. In encroached plots, grazer and mixed feeder species occurrence were reduced while the presence of browser species was slightly elevated. Furthermore, our finding shows that bare ground cover is positively correlated with an increase of woody plant cover. Additionally, the number of herbaceous species slightly increased with the increase of woody plant encroachment, while the herbaceous cover was negatively correlated with the increase of woody plant cover. We suggest that fire regimes should be taken up to suppress the ongoing encroachment processes while strongly encroached sites might need mechanical intervention to control dense vegetation. This emphasis is on fire, particularly prescribed fire as a management tool of vegetation in Savanna ecosystem. We conclude that, woody plant encroachment is driven by different factors such as fire, mega-herbivores and topology that may interactively trigger woody plant encroachment in Savanna ecosystem.

Simultaneous multiple‐calf allonursing by a wild Masai giraffe

1 INTRODUCTION Allonursing is when mothers nurse young that are not their own. It is rarely seen in wild giraffes (Giraffa camelopardalis). Pratt and Anderson (1979) reported that of 860 observations of nursing attempts, 37 were by an unrelated calf, and just one succeeded in sustained nursing. Saito and Idani (2018) documented only five of 76 allonursing attempts resulted in sustained nursing. Typically, the mother appeared unaware that the nursing calf was not her own, and thus, these studies concluded that the instigators of allonursing were unrelated calves stealing milk from unwitting mothers. Here, we report an instance of simultaneous allonursing by three giraffe calves in Tarangire National Park, Tanzania. This case is unusual in that the lactating female appeared to be aware of all three nursing calves and allowed nursing for an extended period of time (>1 min). 2 METHODS Since 2011, we systematically collected data on giraffes during 6 road‐transect surveys per year in a 1,500‐km2 area of the Tarangire Ecosystem, northern Tanzania, between latitude 3.27–4.08°S and longitude 35.73–36.23°E. The main vegetation communities are Acacia tortilis parkland, Acacia‐Commiphora woodland, gall Acacia drepanolobium woodland, Combretum‐Dalbergia woodland and open grassland (Lamprey, 1963). We identified individual giraffes from photographs using their unique and unchanging coat patterns (Foster, 1966) with the aid of pattern recognition software (Bolger, Morrison, Vance, Lee, & Farid, 2012). We did not genetically assign calves to mothers, but we assumed mother–calf pairs from extended suckling behaviour (>5 s) without rejection. 3 RESULTS AND DISCUSSION We documented 82 extended nursing bouts during 45 surveys from 2011 to 2019. All previous bouts were a single female and single calf. On 27 January 2019, we witnessed a remarkable case of simultaneous multiple‐calf allonursing. An adult female moved towards a group of calves (<1 year of age), and three of the calves immediately ran over and began suckling from her. We were not certain whether any of the calves were her offspring nor whether the calves were related to each other or to the female. The calves were slightly different sizes, and thus, we presumed different ages, and two were females, and one was a male (Figure 1). The adult female allowed this nursing for over a minute and did not actively reject the nursing calves. She appeared to be aware of the situation as all three calves approached her from the front and were in her view during nursing (Figure 1).

Tree resprout dynamics following fire depend on herbivory by wild ungulate herbivores

Abstract Savanna tree cover is dynamic due to disturbances such as fire and herbivory. Frequent fires can limit a key demographic transition from sapling to adult height classes in savanna trees. Saplings may be caught in a ‘fire trap’, wherein individuals repeatedly resprout following fire top‐kill events. Saplings only rarely escape the cycle by attaining a fire‐resistant height (e.g. taller than the minimum scorch height) during fire‐free intervals. Large mammalian herbivores also may trap trees in shorter size classes. Browsing herbivores directly limit sapling height, while grazing herbivores such as cattle facilitate sapling growth indirectly via grass removal. Experimental studies investigating how meso‐wildlife, megaherbivores and domestic livestock affect height of resprouts following fire are rare, but necessary for fully understanding how herbivory may reinforce (or counteract) the fire trap. In our study system, interactive fire–herbivore effects on transitions from sapling (&lt;1 m) to adult tree (&gt;1 m) height classes may be further influenced by plant defences, such as symbiotic ants. We used the Kenya Long‐term Exclosure Experiment (KLEE) to investigate how post‐fire resprout size of a widespread monodominant East African tree, Acacia drepanolobium was influenced by (a) herbivory by different combinations of cattle, meso‐wildlife (15–1,000 kg) and megaherbivores (&gt;1,000 kg) and (b) the presence of acacia–ant mutualists that confer tree defences. We sampled height, stem length and ant occupancy of resprouts exposed to different herbivore combinations before and after controlled burns. Resprout height of saplings that were short prior to fire (&lt;1 m) was reduced primarily by meso‐wildlife. Negative effects of elephants on post‐fire resprout height increased with pre‐fire tree size, suggesting that resprouts of the tallest trees (with the greatest potential to escape the fire trap cycle) were preferentially browsed and reduced in height by elephants. There were no significant cattle effects. Synthesis. We provide experimental evidence for two potential pathways through which large herbivores exert control over sapling escape from the fire trap: (a) post‐fire meso‐wildlife browsing of short (&lt;1 m) resprouts and (b) elephant browsing of the largest size class of resprouts, which would otherwise be most likely to escape the fire trap.

Impacts of a mineral lick-centred land use system on woody vegetation cover in an East African Savannah

Evaluation of woody vegetation changes with distance from a salt crater was conducted in the semi‐arid rangelands of southern Ethiopia. Data on live woody plants were collected over three seasons at 0, 1, 4, 6, 9 and 12 km from the salt crater. The density and diversity of woody plants differed significantly (p < .01) along the distance gradient. Six woody plant families were identified of which Fabaceae and Burseraceae were the dominant families. Acacia drepanolobium, Acacia nilotica, Commiphora africana and Acacia mellifera were among the severely encroaching woody species. There were high proportions of seedlings and saplings recorded closer to the salt crater showing a vigorous recruitment by woody plants. Woody plant encroachment along the 12‐km transect ranged from a low to severe encroachment, which could be translated into poor rangeland condition. Changes in soil characteristics increased grazing pressure and sedentary settlement around the salt crater, and the breakdown of traditional institutions seems to be major contributing factors to these vegetation changes. We suggest that severely encroached areas could be improved through a combination of methods such as bush clearing, prescribed fire, browsing animals and proper grazing management.

Economy of scale: third partner strengthens a keystone ant-plant mutualism.

While foundation species can stabilize ecosystems at landscape scales, their ability to persist is often underlain by keystone interactions occurring at smaller scales. Acacia drepanolobium is a foundation tree, comprising >95% of woody cover in East African black-cotton savanna ecosystems. Its dominance is underlain by a keystone mutualistic interaction with several symbiotic ant species in which it provides housing (swollen thorns) and carbohydrate-rich nectar from extra-floral nectaries (EFN). In return, it gains protection from catastrophic damage from mega-herbivores. Crematogaster mimosae is the ecologically dominant symbiotic ant in this system, also providing the highest protection services. In addition to tending EFN, C.mimosae tend scale insects for carbohydrate-rich honeydew. We investigated the role of scale insects in this specialized ant-plant interaction. Specifically, does this putatively redundant third partner strengthen the ant-plant mutualism by making the ant a better protector of the tree? Or does it weaken the mutualism by being costly to the tree while providing no additional benefit to the ant-plant mutualism? We coupled observational surveys with two scale-manipulation experiments and found evidence that this third partner strengthens the ant-plant mutualism. Trees with scale insects experimentally removed experienced a 2.5X increase in elephant damage compared to trees with scale insects present over 10 months. Reduced protection was driven by scale removal causing a decrease in ant colony size and per capita baseline activity and defensive behavior. We also found that ants increased scale-tending and the density of scale insects on trees when EFN were experimentally reduced. Thus, in this system, scale insects and EFN are likely complementary, rather than redundant, resources with scale insects benefitting ants when EFN production is low (such as during annual dry periods in this semi-arid ecosystem). This study reveals that a third-partner strengthens an ant-plant mutualism that serves to stabilize a whole ecosystem.

Polygyny does not explain the superior competitive ability of dominant ant associates in the African ant-plant, Acacia (Vachellia) drepanolobium.

The Acacia drepanolobium (also known as Vachellia drepanolobium) ant‐plant symbiosis is considered a classic case of species coexistence, in which four species of tree‐defending ants compete for nesting space in a single host tree species. Coexistence in this system has been explained by trade‐offs in the ability of the ant associates to compete with each other for occupied trees versus the ability to colonize unoccupied trees. We seek to understand the proximal reasons for how and why the ant species vary in competitive or colonizing abilities, which are largely unknown. In this study, we use RADseq‐derived SNPs to identify relatedness of workers in colonies to test the hypothesis that competitively dominant ants reach large colony sizes due to polygyny, that is, the presence of multiple egg‐laying queens in a single colony. We find that variation in polygyny is not associated with competitive ability; in fact, the most dominant species, unexpectedly, showed little evidence of polygyny. We also use these markers to investigate variation in mating behavior among the ant species and find that different species vary in the number of males fathering the offspring of each colony. Finally, we show that the nature of polygyny varies between the two commonly polygynous species, Crematogaster mimosae and Tetraponera penzigi: in C. mimosae, queens in the same colony are often related, while this is not the case for T. penzigi. These results shed light on factors influencing the evolution of species coexistence in an ant‐plant mutualism, as well as demonstrating the effectiveness of RADseq‐derived SNPs for parentage analysis.

Influence of neighboring plants on the dynamics of an ant-acacia protection mutualism.

Ant-plant protection symbioses, in which plants provide food and/or shelter for ants in exchange for protection from herbivory, are model systems for understanding the ecology of mutualism. While interactions between ants, host plants, and herbivores have been intensively studied, we know little about how plant-plant interactions influence the dynamics of these mutualisms, despite strong evidence that plants compete for resources, that hosting ants can be costly, and that host-plant provisioning to ants can therefore be constrained by resource availability. We used field experiments in a semiarid Kenyan savanna to examine interactions between the ant-plant Acacia drepanolobium, neighboring grasses, and two species of symbiotic acacia-ants with divergent behaviors: Crematogaster mimosae, an aggressive symbiont that imposes high costs to host trees via consumption of extrafloral nectar, and Tetraponera penzigi, a less-protective symbiont that imposes lower costs because it does not consume nectar. We hypothesized that by competing with acacias for resources, neighboring grasses (1) reduce hosts' ability to support costly C.mimosae, while having little or no effect on the ability of hosts to support low-cost T.penzigi, and (2) reduce sapling growth rates irrespective of ant occupant. We factorially manipulated the presence/absence of grasses and the identity of ant occupants on saplings and evaluated effects on colony survivorship and sapling growth rates over 40weeks. Contrary to prediction, the high-cost/high-reward nectar-dependent mutualist C.mimosae had higher colony-survival rates on saplings with grass neighbors present. Grasses appear to have indirectly facilitated the survival of C.mimosae by reducing water stress on host plants; soils under saplings shaded by grasses had higher moisture content, and these saplings produced more active nectaries than grass-removal saplings. Consistent with prediction, survival of low-cost/low-reward T.penzigi did not differ significantly between grass-removal treatments. Saplings occupied by low-cost/low-reward T.penzigi grew 100% more on average than saplings occupied by high-cost/high-reward C.mimosae, demonstrating that mutualist-partner identity strongly and differentially influences demographic rates of young plants. In contrast, contrary to prediction, grass neighbors had no significant net impact on sapling growth rates. Our results suggest that neighboring plants can exert strong and counterintuitive effects on ant-plant protection symbioses, highlighting the need to integrate plant-plant interactions into our understanding of these mutualisms.

Time Series Monitoring of Bush Encroachment by &amp;lt;i&amp;gt;Euclea divinorum&amp;lt;/i&amp;gt; in Ol Pejeta Conservancy Laikipia, Kenya

Bush encroachment refers to the invasion of woody species in Savannah ecosystems driven by either anthropogenic and/or natural factors. This study sought to examine land cover changes and topographic features attributable to patterns of encroachment in Ol Pejeta Conservancy (OPC) where, <i>Euclea divinorum</i> unpalatable woody species has colonised former grasslands and other habitats which provide grazing grounds for herbivore wildlife species. Here, we monitored vegetation cover trends in the period 1987-2016 using five vegetation classes on Landsat images acquired during the dry season. Additionally, slope based NDVI maps and digital elevation models were used to identify topographic influences on vegetation change. Results revealed that <i>E. divinorum</i> increased significantly between 1987 and 2016 (Mann Kendall test for trend analysis tau 1, n=6, p&lt; 0.01). On the other hand, <i>Acacia drepanolobium</i> and <i>Acacia xanthophloea</i> decreased from 49.72% and 5.31% in 1987 to 17.00% and 0.29% in 2016 respectively. Further, areas in low elevation were more colonised by <i>E. divinorum</i>. The colonising <i>E. divinorum</i> is unpalatable hence lacks natural predators whilst, <i>A. drepanolobium</i> and <i>A. Xanthophloea</i> which are alternative herbivory species decreased. Understanding dynamics of woody vegetation in savannah is crucial for management of healthy and sustainable ecosystems.

Status of the population of Karamoja Apalis Apalis karamojae in north-eastern Uganda

The distribution of the Karamoja Apalis Apalis karamojae, an East African endemic, has been sparsely documented in Uganda. In October 2011, a survey of the species was carried out near Iriiri in north-eastern Uganda. The main aim was to find out if there is a viable population of the species and to highlight the threats to its population. Sixteen 1-km transects in four sites were surveyed. The survey recorded nine individuals including a pair at an occupied nest, which is not conclusive for determining the viability of the population. The main threats to the species were cutting of the dominant shrub Vachellia drepanolobium (Acacia drepanolobium) in the area, farming and grazing. When we attempted luring the birds using the recorded song of the Karamoja Apalis from Tanzania, these individuals did not respond. We therefore recommend (1) to undertake a more detailed GIS survey to discover the extent of the suitable habitat, (2) to repeat the survey with improved effort to better estimate the viability of this population, (3) to conduct a study to ascertain the successful breeding of the species in the area, (4) to conduct a DNA analysis to compare the Iriiri population with the Tanzanian population, and (5) to record the song of the Ugandan birds for song analysis and to determine the response of Tanzanian birds.