Mashau, A. C. | Search bioRxiv

bioRxiv2023

Global analysis of Poales diversification - parallel evolution in space and time into open and closed habitats

O_LIPoales are one of the most species-rich, ecologically and economically important orders of plants and often characterise open habitats, enabled by unique suites of traits. We test the hypotheses that Poales species are assembled into distinct phyloregions, with centres of high phylogenetic diversity and endemism clustered in tropical regions, and that cosmopolitan families show parallel transitions into open and closed habitats at different times. C_LIO_LIWe sampled 42% of Poales species and obtained taxonomic and biogeographic data from the World Checklist of Vascular Plants database, which was combined with open/closed habitat data scored by taxonomic experts. A dated supertree of Poales was constructed. We integrated spatial phylogenetics with regionalization analyses, historical biogeography, ancestral state estimations, and models of contingent evolution. C_LIO_LIDiversification in Poales and assembly of open and closed habitats result from dynamic evolutionary processes that vary across lineages, time, space, and traits, most prominently in tropical and southern latitudes. Our results reveal parallel and recurrent patterns of habitat and trait transitions in the species-rich families Poaceae and Cyperaceae, yet other smaller families display unique evolutionary trajectories. C_LIO_LIThe Poales have achieved global dominance via parallel evolution in open habitats, with notable, spatially and phylogenetically restricted divergences into strictly closed habitats. C_LI

ecology↗

bioRxiv2021

Limits to resilience of Afroalpine vegetation to grazing and burning: a case study of grasses from the Drakensberg Mountain Centre, southern Africa

O_LIHigh-elevation Afroalpine ecosystems of the Drakensberg Mountain Centre (DMC) of Lesotho and South Africa, renowned for their high endemism and key ecosystem services, are socio-ecological systems that have seen human activity for millennia. However, their responses to land management practices are understudied. Controversy over their natural state has also led to conflicting policies and management emphases. C_LIO_LIFocusing on the crucial ecosystem-modulating component, grasses (Poaceae), we evaluate the response of DMC Afroalpine vegetation to human impact through grazing and burning. Grass species associations were recorded from grassland, shrubland and wetland-riparian-seep ecotypes across a range of grazing and fire regimes to document relationships between abiotic conditions, disturbance, and taxonomic diversity and composition. C_LIO_LICCA of grass community composition retrieved a large cluster of plots of mixed grazing and burning regimes with no particular environmental vector correlated with them. Other smaller groups of plots separated from these were associated to heavy grazing, bioclimatic variables, slope gradient, and aspect. Indicator species analyses found DMC endemic grasses were associated to low grazing, while alien grasses were associated to heavy grazing. GLMs found little difference between ecotype-disturbance categories with regards plant species richness, mean alpha hull=2 range-size of native and sub-Saharan endemic grasses, and site-level Sorensen beta diversity ({beta}sor). Some differences were noted, including the highest cover and proportion of DMC endemics being found in low-grazed grassland, and highest cover and proportion of alien grasses and highest plot-level {beta}sor being found in heavily grazed ecotypes. Relative importance analyses found grazing regime to be the main influence on cover and proportion of DMC endemic and alien grasses. Partial Mantel tests found mean annual temperature and grazing regime to be the main influence on plot-level {beta}sor. C_LIO_LISynthesis: Taxonomic diversity and composition of DMC Afroalpine grasslands was relatively unaffected by moderate grazing and intense burning, although heavy grazing had a largely detrimental impact, with its ubiquity across the DMC a major cause for concern. High levels of endemism, coupled with the above data emphasizing the robustness of DMC grasslands to disturbance, also supports Afroalpine grasslands as a natural component of the DMC. This research reinforces the natural grass-dominated nature of the DMC as a social-ecological system where sustainable management is possible thanks to its resilience to grazing and burning, although current widespread overgrazing requires urgent attention. C_LI

ecology↗