Grasses, by their high productivity even under very low pCO2, their ability to survive repeated burning and to tolerate long dry seasons, have transformed the terrestrial biomes in the Neogene and Quaternary. The expansion of grasslands at the cost of biodiverse forest biomes in Madagascar is often postulated as a consequence of the Holocene settlement of the island by humans. However, we show that the Malagasy grass flora has many indications of being ancient with a long local evolutionary history, much predating the Holocene arrival of humans. First, the level of endemism in the Madagascar grass flora is well above the global average for large islands. Second, a survey of many of the more diverse areas indicates that there is a very high spatial and ecological turnover in the grass flora, indicating a high degree of niche specialization. We also find some evidence that there are both recently disturbed and natural stable grasslands: phylogenetic community assembly indicates that recently severely disturbed grasslands are phylogenetically clustered, whereas more undisturbed grasslands tend to be phylogenetically more evenly distributed. From this evidence, it is likely that grass communities existed in Madagascar long before human arrival and so were determined by climate, natural grazing and other natural factors. Humans introduced zebu cattle farming and increased fire frequency, and may have triggered an expansion of the grasslands. Grasses probably played the same role in the modification of the Malagasy environments as elsewhere in the tropics.

Ethnopharmacological relevance Given the increasing coverage of antiretroviral therapy (ART) for HIV/AIDS treatment as well as the high utilization of herbal medicine, many persons living with HIV/AIDS in sub-Saharan Africa are thought to practice medical pluralism, or the adoption of more than one medical system for their care and treatment. Using a cross-sectional study we sought to document and identify the herbal medicines used by persons living with HIV/AIDS on Mfangano Island, Suba District, Nyanza Province, Kenya. Materials and Methods We interviewed herbalists and knowledgeable mothers to obtain information regarding medicinal plants, particularly for HIV/AIDS-related symptoms, HIV/AIDS, and chira (an illness concept with similarities to HIV/AIDS regarding sexual transmission and wasting symptoms). Using systematic sampling, 67 persons living with HIV/AIDS (49 of whom were receiving ART) were selected from an Mfangano Island health clinic and participated in semi-structured interviews. Results Interviews with herbalists and mothers identified 40 plant species in 37 genera and 29 families that a person with HIV/AIDS or chira could use for herbal remedies. Overall, 70.1% of persons living with HIV/AIDS had used medicinal plants after HIV diagnosis, most commonly to treat symptoms related to HIV/AIDS. In addition to common vegetables and fruits that can serve medicinal purposes, Azadirachta indica A.Juss. (Meliaceae), Carissa edulis (Forssk.) Vahl (Apocynaceae), and Ximenia americana L. (Olacaceae) were the most frequently cited medicinal plants used by persons living with HIV/AIDS. Conclusions Collaboration and communication between biomedical clinicians and herbalists should be encouraged given high rates of concomitant ART-herb usage. Pharmacological, toxicological, and ART-herb interaction studies based on the plants identified in this study and their constituent ingredients should be considered.

The phenomenon of sharp boundaries between distinctive vegetation types occurring under the same climatic conditions has often been interpreted by plant ecologists to characterise alternative stable states (ASS). The phenomenon may be relevant in explaining two strikingly different vegetation formations (broad‐leaved nonspiny Combretum and fine‐leaved spiny Acacia) co‐occurring in mesic savannah of southeastern Kenya. We hypothesise that the two vegetation within southeastern Kenya ecosystems represent ASS whose transition may be a response to soil characteristics switch. To explore our hypothesis, we analysed empirical field data of woody species and soil characteristics from 57 plots that included 25 from Combretum and 32 from Acacia vegetation formations. We compared floristic composition and soil characteristics between the two systems and correlated edaphic statuses and vegetation states. We encountered 2,749 woody plant individuals, representing 115 species, 87 genera and 40 families. We found that the two vegetation had discrete woody species composition and soil characteristics, and also a significant species–edaphic association. The results are consistent with the ASS theory demonstrating that soil characteristics are among the important micro‐environmental filters driving and maintaining woody vegetation mosaics in the tropics. Importantly, understanding ASS has ramifications for sustainable utilisation of woody plant resources in East African savannahs.

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A trade-off between structural and chemical defences against herbivory in woody plants is alleged to depend on edaphic factors in African savannas. We studied anti-herbivory traits, in an edaphic mosaic of fertile and infertile soils within a savanna landscape in East Africa, towards elucidating herbivory defence traits expressions in woody plants of African savannas. We used data of 81 plants for 8 species from 8 sites — four sites from fertile soils (42 plants) and another four sites from infertile soils (39 plants). We did not find a general divide between structural and chemical strategies in our data. Instead, we found a range of defence traits combinations. Our results highlight that in woody plants of African savannas, chemical and structural defences can augment each other, and not necessarily trade-off. The diversity of herbivores, ranging from insects to mesobrowsers, may have driven the evolution of multiple defence strategies within the African savannas.