The ecology of sprouting in South African forests, savannas and fynbos

Sprouting has only recently received attention as a key life history strategy, especially in less disturbance prone environments. The aims of this thesis were to explore the ecological role of sprouting in selected South African biomes. In particular, to explore the biogeographic, community and individual level consequences of adopting sprouting as a life history strategy. The thesis is broadly divided into 4 sections. The first three dealing with the ecology of sprouting in forests, fynbos and savannas respectively; and the fourth undertakes to determine whether sprouting is considered in plant ecological strategy schemes. Chapter 1 and 2 deals with the role of sprouting in forests in relation to reseeding as key regeneration strategies in southern Cape forests. Sprouting has been largely been ignored as a regeneration strategy in favour of reseeding in southern African forests. I found that tall forests are dominated by reseeding species, while sprouting species dominate shorter canopied forests. The relative dominance of sprouters has an effect on forest canopy species richness: as sprouter abundance increases, with decreasing canopy height, canopy species richness decreases. Sprouters are able to retain their in situ position in the forests for longer periods of time than do reseeders, which reduces individual and species turnover, and hence canopy species richness. In Chapter 3 and 4, I explore Proteaceae Life History strategies in relation to fire. Sprouting ability and bark thickness are used as key traits in defining Proteaceae life history strategies. Five functional groups are described and are broadly divided into two categories resisters and non-resisters. Resisters include thick barked fire resisting and epicormic sprouting species and non-resisters basal sprouting and thin barked non-resistant species. Sprouting strategy and bark thickness were also found to influence plant architecture and hence individual and stand flammability. Non-resisting species tend to display a more ramified architecture, resulting in a more flammable state. Conversely, thick barked species tend to display a less ramified and therefore more fire resistance architecture. In Chapter 5 I explore how changes in disturbance regime affect Acacia life history strategies in Hluhluwe-Umfolozi Park, KwaZulu Natal, South Africa. Four functional groups are defined based on sprouting ability, bark thickness, seed mass, plant height and wood density. The functional groups are seen to reflect local disturbance regimes: Acacia species found in mesic, frequently burnt portions of the park sprout strongly as adults and/or are fire resistant, but are poorly defended against herbivory. Conversely, species found in more xeric portions, where fire frequency is lower, and herbivore densities higher, are fire-sensitive, well defended against herbivory and sprout weakly as adults. Chapter 6 addresses whether plant ecological strategy schemes take sprouting into account as a key life history strategy. Westoby's LHS scheme, which comprises specific leaf area (SLA), plant height and seed mass, is of the more practicable existing plant ecological strategy schemes. I show that the LHS scheme does not consistently identify sprouting across genera or families. In general, basal sprouters tended to be shorter than congeneric reseeders, but there were no consistent patterns for SLA or seed mass. The results suggest that sprouting ability is mostly orthogonal to other life history traits and should be therefore considered as a separate attribute. A published paper, which is ancillary to the main themes of the thesis, has been included as an appendix

Reproductive biology of the sausage tree (Kigelia africana) in Kruger National Park, South Africa

Kigelia africana has large flowers that are vertebrate pollinated and very large fruits that are likely to be vertebrate dispersed. Our field surveys of size–class distributions of K. africana in the southern Kruger National Park (KNP) suggest a lack of recruitment. This is possibly the result of a failure of mutualistic relationships with vertebrate dispersers and/or pollinators. Breeding system experiments indicated that K. africana is an obligate out-crosser. Despite being primarily adapted for bat pollination, in KNP that K. africana is presently mainly pollinated by a diversity of largely facultatively nectarivorous bird species. Fruit-set is high, although trees isolated by > 50 m were found to suffer depressed seed output. Our preliminary investigation of dispersal suggests that fruits are largely ignored and are thus weakly attractive to potential dispersers. Seedlings placed out in the field in KNP suffered high levels (> 50%) of mortality compared to 17.5% in control plots. This threefold difference is the result of herbivory over a 2-month period. In summary, the adult centric population structure is probably not because of pollen or seed limitation but may result from dispersal limitation or excessive herbivory

Sustaining the University of Johannesburg and Western Sydney University partnership in the time of COVID : a qualitative case study

Abstract: This article offers a qualitative case study of how COVID has changed an existing international education partnership between the University of Johannesburg (UJ) in South Africa and Western Sydney University (WSU) in Australia which involves collaboration with the not-for-profit Nsasani Trust and focuses on sustainability. Before COVID, both universities ran joint student mobility programs in the Kruger National Park (KNP) and were developing further plans for staff mobility and co-developed post- grad programs involving residency in both countries. These plans changed as a result of the COVID pandemic, which started in early 2020. Societal responses to the COVID pandemic, including national border closures, have forced academics, administrators and students to reconsider how internationalisation programs function during and after the pandemic. Using a qualitative case study based on personal experience, we argue that pre-existing university-to-university connections built before COVID will sustain linkages, but that the previous structure of engagement – based on physical mobility – can shift to new arrangements that can be run fully digitally or used to support limited mobility when international travel resumes in the future. We position the UJ-WSU relationship in the historical context of internationalisation to both highlight the enduring nature of international engagements and suggest that changes are required to make international education sustainable

Drought limits large trees in African savannas with or without elephants

DATA AVAILABILITY STATEMENT : The data that support the findings of this study will be made openly available once accepted for publication in Figshare.Consumers, including megaherbivores and fire, are considered important limiting forces for woody plants and canopy closure in African savannas. However, climatic events like drought can also play a significant role in limiting trees and maintaining tree-grass coexistence in savannas. The extent to which top-down control (e.g. megaherbivores) and bottom-up resource limitation through drought and competition interact to influence savanna tree mortality and woody structure is unclear. Here, we compared the change in the number of large trees before and after a severe drought in a savanna with elephants (Loxodonta africana) and one without elephants. Elephants and drought both limited the number of large trees at our sites, but contrary to our predictions, there was no interactive effect of these drivers on overall changes in tree densities. However, there was a synergistic effect on the dominant tree species, Senegalia nigrescens, such that tree loss post-drought was greater where elephants were present compared to where they were absent. Hence, our results suggest that species-specific differences in drought resistance, as well as density-dependent factors, likely impact the severity of drought effects on savanna tree communities. In savannas, drought has the potential to exert strong control on tree survival and prevent canopy closure, thus partially filling the role of megaherbivores in limiting large trees when these consumers are absent. As drought severity and frequency are predicted to increase in the future, the influence of drought on savanna vegetation structure becomes increasingly important to consider.NSF IRES Grants, NSF Graduate Research Fellowship Program and U.S. National Institute of Food and Agriculture.https://wileyonlinelibrary.com/journal/aechj2023Mammal Research InstituteZoology and Entomolog

Frightened of giants : fear responses to elephants approach that of predators

DATA ACCESSIBILITY : Data and code to reproduce the analyses provided in the electronic supplementary material [46].Animals are faced with a variety of dangers or threats, which are increasing in frequency with ongoing environmental change. While our understanding of fearfulness of such dangers is growing in the context of predation and parasitism risk, the extent to which non-trophic, interspecific dangers elicit fear in animals remains less appreciated. We provide an experimental test for fear responses of savannah ungulates to a dominant and aggressive megaherbivore, the African bush elephant (Loxodonta africana), and contrast responses to an apex predator known to elicit fear in this system. Using an automated behavioural response system, we contrast vigilance and run responses of ungulates to elephant, leopard (Panthera pardus), and control (red-chested cuckoo Cuculus solitarius) vocalizations. Overall, we find that ungulates responded to elephant calls, both in terms of an increase in run and vigilance responses relative to controls. The magnitude of most behavioural responses (four of six considered) to elephant vocalizations were not significantly different than responses to leopards. These results suggest that megaherbivores can elicit strong non-trophic fear responses by ungulates and call to broaden frameworks on fear to consider dominant species, such as megaherbivores, as key modifiers of fear-induced interactions.The National Science Foundation.https://royalsocietypublishing.org/journal/rsblam2024Mammal Research InstituteZoology and EntomologySDG-15:Life on lan

Understanding the limits to generalizability of experimental evolutionary models.

Post print version of article deposited in accordance with SHERPA RoMEO guidelines. The final definitive version is available online at: http://www.nature.com/nature/journal/v455/n7210/abs/nature07152.htmlGiven the difficulty of testing evolutionary and ecological theory in situ, in vitro model systems are attractive alternatives; however, can we appraise whether an experimental result is particular to the in vitro model, and, if so, characterize the systems likely to behave differently and understand why? Here we examine these issues using the relationship between phenotypic diversity and resource input in the T7-Escherichia coli co-evolving system as a case history. We establish a mathematical model of this interaction, framed as one instance of a super-class of host-parasite co-evolutionary models, and show that it captures experimental results. By tuning this model, we then ask how diversity as a function of resource input could behave for alternative co-evolving partners (for example, E. coli with lambda bacteriophages). In contrast to populations lacking bacteriophages, variation in diversity with differences in resources is always found for co-evolving populations, supporting the geographic mosaic theory of co-evolution. The form of this variation is not, however, universal. Details of infectivity are pivotal: in T7-E. coli with a modified gene-for-gene interaction, diversity is low at high resource input, whereas, for matching-allele interactions, maximal diversity is found at high resource input. A combination of in vitro systems and appropriately configured mathematical models is an effective means to isolate results particular to the in vitro system, to characterize systems likely to behave differently and to understand the biology underpinning those alternatives

Reflecting on research produced after more than 60 years of exclosures in the Kruger National Park

All data, in this case works of literature reviewed have been summarised in Online Appendix 2.Herbivores are a main driver of ecosystem patterns and processes in semi-arid savannas, with their effects clearly observed when they are excluded from landscapes. Starting in the 1960s, various herbivore exclosures have been erected in the Kruger National Park (KNP), for research and management purposes. These exclosures vary from very small (1 m2) to relatively large (almost 900 ha), from short-term (single growing season) to long-term (e.g. some of the exclosures were erected more than 60 years ago), and are located on different geologies and across a rainfall gradient. We provide a summary of the history and specifications of various exclosures. This is followed by a systematic overview of mostly peer-reviewed literature resulting from using KNP exclosures as research sites. These 75 articles cover research on soils, vegetation dynamics, herbivore exclusion on other faunal groups and disease. We provide general patterns and mechanisms in a synthesis section, and end with recommendations to increase research outputs and productivity for future exclosure experiments. CONSERVATION IMPLICATIONS : Herbivore exclosures in the KNP have become global research platforms, that have helped in the training of ecologists, veterinarians and field biologists, and have provided valuable insights into savanna dynamics that would otherwise have been hard to gain. In an age of dwindling conservation funding, we make the case for the value added by exclosures and make recommendations for their continued use as learning tools in complex African savannas.South African Environment Observation Network (SAEON).http://www.koedoe.co.zaam2023Paraclinical Science

Principal molecular axis and transition dipole moment orientations in liquid crystal systems: an assessment based on studies of guest anthraquinone dyes in a nematic host

An assessment of five different definitions of the principal molecular axis along which molecules align in a nematic liquid crystal system has been made by analysing fully atomistic molecular dynamics (MD) simulations of a set of anthraquinone dyes in the cyanobiphenyl-based nematic host mixture E7. Principal molecular axes of the dyes defined by minimum moment of inertia, minimum circumference, minimum area, maximum aspect ratio, and surface tensor models were tested, and the surface tensor model was found to give the best description. Analyses of MD simulations of E7 alone showed that the surface tensor model also gave a good description of the principal molecular axes of the host molecules, suggesting that this model may be applicable more generally. Calculated dichroic order parameters of the guest-host systems were obtained by combining the surface tensor analysis with fixed transition dipole moment (TDM) orientations from time-dependent density functional theory (TD-DFT) calculations on optimised structures of the dyes, and the trend between the dyes generally matched the trend in the experimental values. Additional analyses of the guest-host simulations identified the range of conformers explored by the flexible chromophores within the dyes, and TD-DFT calculations on corresponding model structures showed that this flexibility has a significant effect on the TDM orientations within the molecular frames. Calculated dichroic order parameters that included the effects of this flexibility gave a significantly improved match with the experimental values for the more flexible dyes. Overall, the surface tensor model has been shown to provide a rationale for the experimental alignment trends that is based on molecular shape, and molecular flexibility within the chromophores has been shown to be significant for the guest-host systems: The computational approaches reported here may be used as a general aid in the predictive design of dyes with appropriate molecular shapes and flexibilities for guest-host applications

WMO assessment of weather and climate mortality extremes : lightning, tropical cyclones, tornadoes, and hail

A World Meteorological Organization (WMO) Commission for Climatology international panel was convened to examine and assess the available evidence associated with five weather-related mortality extremes: 1) lightning (indirect), 2) lightning (direct), 3) tropical cyclones, 4) tornadoes, and 5) hail. After recommending for acceptance of only events after 1873 (the formation of the predecessor of the WMO), the committee evaluated and accepted the following mortality extremes: 1) ''highest mortality (indirect strike) associated with lightning'' as the 469 people killed in a lightning-caused oil tank fire in Dronka, Egypt, on 2 November 1994; 2) ''highest mortality directly associated with a single lightning flash'' as the lightning flash that killed 21 people in a hut in Manica Tribal Trust Lands, Zimbabwe (at time of incident, eastern Rhodesia), on 23 December 1975; 3) ''highest mortality associated with a tropical cyclone'' as the Bangladesh (at time of incident, East Pakistan) cyclone of 12-13 November 1970 with an estimated death toll of 300 000 people| 4) ''highest mortality associated with a tornado'' as the 26 April 1989 tornado that destroyed the Manikganj district, Bangladesh, with an estimated death toll of 1300 individuals| and 5) ''highest mortality associated with a hailstorm'' as the storm occurring near Moradabad, India, on 30 April 1888 that killed 246 people. These mortality extremes serve to further atmospheric science by giving baseline mortality values for comparison to future weather-related catastrophes and also allow for adjudication of new meteorological information as it becomes available.https://www.ametsoc.org/ams/index.cfm/publications/journals/weather-climate-and-society2018-01-30hj2017Geography, Geoinformatics and Meteorolog

Low-coordinate first-row transition metal complexes in catalysis and small molecule activation

Enforcing unusually low coordination numbers on transition metals with sterically demanding ligands has long been an area of interest for chemists. Historically, the synthesis of these challenging molecules has helped to elucidate fundamental principles of bonding and reactivity. More recently, there has been a move towards exploiting these highly reactive complexes to achieve a range of transformations using cheap, earth-abundant metals. In this Perspective, we will highlight selected examples of transition metal complexes with low coordination numbers that have been used in catalysis and the activation of small molecules featuring strong bonds (N2, CO2, and CO)