The palm family occurs in all tropical and sub-tropical regions of the world. Palms are of high ecological and economical importance, and display complex spatial patterns of species distributions and diversity. This review summarizes empirical evidence for factors that determine palm species distributions, community composition and species richness such as the abiotic environment (climate, soil chemistry, hydrology and topography), the biotic environment (vegetation structure and species interactions) and dispersal. The importance of contemporary vs. historical impacts of these factors and the scale at which they function is discussed. Finally a hierarchical scale framework is developed to guide predictor selection for future studies. Determinants of palm distributions, composition and richness vary with spatial scale. For species distributions, climate appears to be important at landscape and broader scales, soil, topography and vegetation at landscape and local scales, hydrology at local scales, and dispersal at all scales. For community composition, soil appears important at regional and finer scales, hydrology, topography and vegetation at landscape and local scales, and dispersal again at all scales. For species richness, climate and dispersal appear to be important at continental to global scales, soil at landscape and broader scales, and topography at landscape and finer scales. Some scale–predictor combinations have not been studied or deserve further attention, e.g. climate on regional to finer scales, and hydrology and topography on landscape and broader scales. The importance of biotic interactions – apart from general vegetation structure effects – for the geographic ecology of palms is generally underexplored. Future studies should target scale–predictor combinations and geographic domains not studied yet. To avoid biased inference, one should ideally include at least all predictors previously found important at the spatial scale of investigation.

1 Current discussions about the structure and functioning of tropical plant communities revolve around whether tropical forests are dominated by sets of widespread and locally abundant species and the relative importance of environmental variation and geographical distance as determinants of variation in species composition. We explored these questions by examining diversity and dominance patterns of palm communities in lowland rain forests in the western Amazon basin (Yasuni National Park, Ecuador and Iquitos-Pebas region, Peru). 2 We used multiple regression to analyse floristic similarity between sites as a function of environmental differences (in topographic position, elevation difference, amount of exchangeable cations and soil texture) and geographical distance. We studied dominance patterns by quantifying the correlations between local abundance and landscape frequency of species within and between the regions. 3 We found floristic composition to be highly variable and more strongly related to geographical distance than to environmental differences. Together, geographical distance and environmental differences explained 70–85% of the variation in floristic similarity. 4 Species abundant in one region were also often abundant in the other, although some dominant species in Iquitos-Pebas did not occur in Yasuni. Local dominance was more pronounced in Yasuni, where the dominant species formed a larger and less variable proportion of all individuals within transects. 5 Limited dispersal and, to a lesser extent, local environmental variation appear to act as determinants of floristic variation in the western Amazon basin. Oligarchic dominance patterns were observed, particularly in Yasuni. 6 Our results lend support to the hypothesis that dispersal across broader spatial scales plays a strong role in the assembly of local ecological communities, but indicate that such limitation supplements, rather than replaces, local ecological determinism.

The use of medicinal plants for treatment of humans and animals is entrenched in the Maasai culture and traditional knowledge related to it is passed on from one generation to the next. A handful of researchers have in the past decades documented this knowledge. No single study has documented medicinal plant uses of the Maasai community as a whole. This review provides a consolidated database of the diversity and uses of medicinal plants among the Maasai in Kenya. The study will help conserve traditional medicinal plant knowledge that is valuable for the development of modern medicine. Relevant information on medicinal plants used by the Maasai of Kenya was extracted from journals, books, M.Sc., and Ph.D. dissertations. We found evidence of 289 plant species used by the Maasai of Kenya in traditional medicine. Most species were used to treat health conditions in the categories gastrointestinal and respiratory system disorders. The most used families were Leguminosae, Asteraceae, Malvaceae, Euphorbiaceae, and Lamiaceae. Medicines were commonly prepared as a decoction and administered through oral ingestion, with roots reported to be the preferred plant part for medication. The Maasai preference for roots compared to other plant parts may be unsustainable and could threaten species availability in the future.

The turnover of phylogenetic clades across space is a fundamental biodiversity pattern that may depend on long-term evolutionary processes, and that has downstream effects on other aspects of diversity including species richness and community structure. Limited niche evolution and limited dispersal are two major processes causing spatial restriction, and thus turnover, of clades. We studied the determinants of clade turnover within the World's richest floristic kingdom, the Neotropics, using the palm family (Arecaceae) as a model. We show that continental-scale clade turnover is driven by a combination of limited niche evolution — with respect to temperature and soil tolerances — and limited dispersal. These findings are consistent with strong dispersal barriers within the Neotropics, and the observation that some palm lineages are most diverse in certain biomes or climates. The importance of such deep-time effects suggest that palms might be slow to adapt or disperse in response to anthropogenic climate change.