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Plant populations persist under recurrent fire via resprouting from surviving tissues (resprouters) or seedling recruitment (seeders). Woody species are inherently slow maturing, meaning that seeders are confined to infrequent fire regimes. However, for grasses, which mature faster, the relationships between persistence strategy and fire regime remain unknown. Globally, we analysed associations between fire regimes experienced by hundreds of grass species and their persistence strategy, within a phylogenetic context. We also tested whether persistence strategies are associated with morphological and physiological traits. Resprouters were associated with less frequent fire than seeders. Whilst modal fire frequencies were similar (fire return interval of 4-6yr), seeders were restricted to regions with more frequent fire than resprouters, suggesting that greater competition with long-lived resprouters restricts seeder recruitment and survival when fire is rare. Resprouting was associated with lower leaf N, higher C:N ratios and the presence of belowground buds, but was unrelated to photosynthetic pathway. Differences between the life histories of grasses and woody species led to a contrasting prevalence of seeders and resprouters in relation to fire frequency. Rapid sexual maturation in grasses means that seeder distributions, relative to fire regime, are determined by competitive ability and recruitment, rather than time to reproductive maturity.

Process-based vegetation models attempt to represent the wide range of trait variation in biomes by grouping ecologically similar species into plant functional types (PFTs). This approach has been successful in representing many aspects of plant physiology and biophysics but struggles to capture biogeographic history and ecological dynamics that determine biome boundaries and plant distributions. Grass-dominated ecosystems are broadly distributed across all vegetated continents and harbour large functional diversity, yet most Land Surface Models (LSMs) summarise grasses into two generic PFTs based primarily on differences between temperate C3 grasses and (sub)tropical C4 grasses. Incorporation of species-level trait variation is an active area of research to enhance the ecological realism of PFTs, which form the basis for vegetation processes and dynamics in LSMs. Using reported measurements, we developed grass functional trait values (physiological, structural, biochemical, anatomical, phenological, and disturbance-related) of dominant lineages to improve LSM representations. Our method is fundamentally different from previous efforts, as it uses phylogenetic relatedness to create lineage-based functional types (LFTs), situated between species-level trait data and PFT-level abstractions, thus providing a realistic representation of functional diversity and opening the door to the development of new vegetation models.

Supplementary Figures 1 – 4, Tables 1 – 3

Tropical savannas cover over 20% of land surface. They sustain a high diversity of mammalian herbivores and promote frequent fires, both of which are dependent on the underlying grass composition. These habitats are typically dominated by relatively few taxa, and the evolutionary origins of the dominant grass species are largely unknown. Here, we trace the origins of the genus Themeda, which contains a number of widespread grass species dominating tropical savannas. Complete chloroplast genomes were assembled for seven samples and supplemented with chloroplast and nuclear ITS markers for 71 samples representing 18 of the 27 Themeda species. Phylogenetic analysis supports a South Asian origin for both the genus and the widespread dominant T. triandra. This species emerged ~1.5 Ma from a group that had lived in the savannas of Asia for several million years. It migrated to Australia ~1.3 Ma and to mainland Africa ~0.5 Ma, where it rapidly spread in pre-existing savannas and displaced other species. Themeda quadrivalvis, the second most widespread Themeda species, is nested within T. triandra based on whole chloroplast genomes, and may represent a recent evolution of an annual growth form that is otherwise almost indistinguishable from T. triandra. The recent spread and modern-day dominance of T. triandra highlight the dynamism of tropical grassy biomes over millennial time-scales that has not been appreciated, with dramatic shifts in species dominance in recent evolutionary times. The ensuing species replacements likely had profound effects on fire and herbivore regimes across tropical savannas.

Savanna is characterised by a C4 grass understorey and a discontinuous overstorey of trees, and occurs across the globe in regions of high mean annual temperature, and intense seasonality in rainfall and productivity. An understanding of the patterns of tree biomass in mesic savannas has remained an ecological conundrum, largely due to the complexity and spatio-temporal heterogeneity of these environments. Yet, understanding the dynamics of these systems is of substantial applied and theoretical significance. I therefore aimed to answer the question: What determines the spatial pattern of tree biomass in Australian tropical mesic savannas? To answer this question, I focussed on a savanna system dominated by Eucalyptus tetrodonta, which occupies 450, 000 km2 of north Australia and accounts for 3% of global savanna lands. I combined use of remote sensing, landscape ecology, data syntheses and statistical modelling. Further, I aimed to investigate this question at four spatial scales: sub-continental (1000’s km); regional (100’s km); landscape (10’s km) and the level of the individual. Investigating this problem from different perspectives enabled to me to attempt to quantify the relative roles of rainfall, fire, mega-herbivory and resource-limitation in determining patterns of savanna tree biomass. At the sub-continental scale, and from 700 -1700 mm mean annual rainfall (MAR), I found tree biomass increased with MAR; MAR limited potential savanna tree biomass yet, this potential was not often realised. Further, I found evidence consistent with the role of disturbance in generating spatial variability in savanna biomass. As an example, areas subjected to experimental fire treatments showed tree biomass could change by +/- 50% over 25 years under a variety of fire regimes. At the regional scale, across a geographically restricted rainfall gradient (1200 - 1600 mm MAR) in Kakadu National Park, and over a 40 year period of observation, the greater variability in fire activity and the inherently higher tree cover in more mesic areas resulted in a greater dynamism of tree cover compared to the drier end of the rainfall gradient. Fire was an important process determining deviations in tree cover below a MAR determined potential. At the landscape scale (10’s km), and over a 40 year period of observation, change in tree cover tracked inter-annual variation in rainfall. Controlling for rainfall, I showed that frequent fire led to declines in tree cover and biomass and large-mammal herbivory promoted an increase in tree cover, likely via the altered spatial and temporal patterning of fire due to changes in grass fuel loads. Fire is a pervasive feature of these ecosystems, modifying vegetation structure and biodiversity. The most important way in which fire limits savanna tree cover is thought to be via its effects on sapling trees, which need several years without fire to grow large enough to enter the canopy. I found evidence for a recruitment bottleneck in four savanna tree species including E. tetrodonta. Further, I found a positive interaction between treetree competition and fire on the recruitment of saplings. This was evidence for the importance of fire in driving cycles of canopy growth and renewal. Across a range of spatial and temporal scales tree cover and biomass in E. tetrodonta dominated savannas is highly spatially and temporally variable, primarily in response to rainfall, fire and their interaction. The historical and spatial perspective provided by this thesis shows the importance of fire in maintaining this savanna system. In the light of this knowledge I make a number of recommendations to help achieve fire management regimes that maintain heterogeneity and population viability of these systems.

In the last couple decades, several viral outbreaks resulting in epidemics and pandemics with thousands of human causalities have been witnessed. The current Covid-19 outbreak represents an unprecedented crisis. In stopping the virus' spread, it is fundamental to have personal protective equipment and disinfected surfaces. Here, the development of a TiO(2)nanowires (TiO(2)NWs) based filter is reported, which it is believed will work extremely well for personal protective equipment (PPE), as well as for a new generation of air conditioners and air purifiers. Its efficiency relies on the photocatalytic generation of high levels of reactive oxygen species (ROS) upon UV illumination, and on a particularly high dielectric constant of TiO2, which is of paramount importance for enhanced wettability by the water droplets carrying the germs. The filter pore sizes can be tuned by processing TiO(2)NWs into filter paper. The kilogram-scale production capability of TiO(2)NWs gives credibility to its massive application potentials.

Madagascar’s unique biota is heavily impacted by human activity and under intense threat. Here, we review the current state of knowledge on the conservation status of Madagascar’s terrestrial and freshwater biodiversity by presenting data and analyses on documented and predicted species-level conservation status, the most prevalent and relevant threats, ex situ collections and programs, and the coverage and comprehensiveness of protected areas. The existing terrestrial protected area network in Madagascar covers 10.4% of its land area and includes at least part of the range of thmajority of described native species of vertebrates with known distributions (97.1% of freshwater fishes, amphibians, reptiles, birds and mammals combined) and plants (67.7%). The overall figures are higher for threatened species (97.7% of threatened vertebrates and 79.6% of threatened plants occurring within at least one protected area). IUCN Red List assessments and Bayesian neural network analyses for plants identify overexploitation of biological resources and unsustainable agriculture as the most prominent threats to biodiversity. We highlight five opportunities for action at multiple levels to ensure that conservation and ecological restoration objectives, programs and activities take account of complex underlying and interacting factors and produce tangible benefits for the biodiversity and people of Madagascar.