Measuring the "importance" of plants and vegetation to people is a central concern in quantitative ethnobotany. A common tool to quantify otherwise qualitative data in the biological and social sciences is an index. Relative cultural importance (RCI) indices such as the "use values" developed by Prance et al. (1987) and Phillips and Gentry (1993a, 1993b) are applied in ethnobotany to calculate a value per folk or biological plant taxon. These approaches can provide data amenable to hypothesis-testing, statistical validation, and comparative analysis. The use of RCI indices is a growing trend in ethnobotanical research, yet there have been few attempts to compile or standardize divergent methods. In this review, we compare RCI indices in four broad categories and present a step-by-step guide to some specific methods. Important background topics are addressed, including ethnographic methods, use categorization, sampling, and statistical analysis. We are concerned here only with "value" as a non-monetary concept. The aspiring and veteran researcher alike should find this paper a useful guide to the development and application of RCI indices. IntroductionThe scientific rigor of ethnobotanical research has increased dramatically in the past two decades due to the adoption of quantitative methods (Phillips 1996). By and large, ethnobotanists have recognized and responded to the need for research based upon hallmarks of the scientific method, including testable hypotheses, reproducible methods, and statistical measures of variation. A primary challenge in this quantitative trend is how to produce values that are reliable and comparable measures of less tangible qualitative data. Borrowing from the social sciences and ecology, considerable advances have been made through the development and application of relative cultural importance (RCI) 1 indices that produce numerical scales or values per plant taxon (Alexiades & Sheldon 1996, Kvist et al. 1995, Lykke et al. 2004, Martin 2004, Phillips & Gentry 1993a, 1993b, Phillips et al. 1994, Phillips 1996, Prance et al. 1987, Reyes-García et al. 2006a, Turner 1988).The application of RCI indices in ethnobotany began during the late 1980s. Boom (1990) determined the percentage of plants used by Panare indigenous informants within a 1 hectare forest plot in Venezuela. His research was an important starting point for quantitative inter-cultural comparisons of plant knowledge. Recognizing that not all uses are equal, Prance et al. (1987), applied weighted indices of 1.0 for "important" uses and 0.5 for "minor" uses. This approach was aimed at capturing relative degrees of "importance", but did not address informant variation. Gentry and Phillip's (1993aPhillip's ( , 1993b) publication on RCI "use values" was a watershed event in quantitative ethnobotany. These last authors evaluated variation among informants based upon use-citation frequencies, considering each as a statistical "event."Since the methods of Prance et al.

We coordinated biogeographical comparisons of the impacts of an exotic invasive tree in its native and non-native ranges with a congeneric comparison in the non-native range. Prosopis juliflora is taxonomically complicated and with P. pallida forms the P. juliflora complex. Thus we sampled P. juliflora in its native Venezuela, and also located two field sites in Peru, the native range of Prosopis pallida. Canopies of Prosopis juliflora, a native of the New World but an invader in many other regions, had facilitative effects on the diversity of other species in its native Venezuela, and P. pallida had both negative and positive effects depending on the year, (overall neutral effects) in its native Peru. However, in India and Hawaii, USA, where P. juliflora is an aggressive invader, canopy effects were consistently and strongly negative on species richness. Prosopis cineraria, a native to India, had much weaker effects on species richness in India than P. juliflora. We carried out multiple congeneric comparisons between P. juliflora and P. cineraria, and found that soil from the rhizosphere of P. juliflora had higher extractable phosphorus, soluble salts and total phenolics than P. cineraria rhizosphere soils. Experimentally applied P. juliflora litter caused far greater mortality of native Indian species than litter from P. cineraria. Prosopis juliflora leaf leachate had neutral to negative effects on root growth of three common crop species of north-west India whereas P. cineraria leaf leachate had positive effects. Prosopis juliflora leaf leachate also had higher concentrations of total phenolics and L-tryptophan than P. cineraria, suggesting a potential allelopathic mechanism for the congeneric differences. Our results also suggest the possibility of regional evolutionary trajectories among competitors and that recent mixing of species from different trajectories has the potential to disrupt evolved interactions among native species.

Grasses are widespread on every continent and are found in all terrestrial biomes. The dominance and spread of grasses and grassland ecosystems have led to significant changes in Earth′s climate, geochemistry, and biodiversity. The abundance of DNA sequence data, particularly chloroplast sequences, and advances in placing grass fossils within the family allows for a reappraisal of the family′s origins, timing, and geographic spread and the factors that have promoted diversification. We reconstructed a time‐calibrated grass phylogeny and inferred ancestral areas using chloroplast DNA sequences from nearly 90% of extant grass genera. With a few notable exceptions, the phylogeny is well resolved to the subtribal level. The family began to diversify in the Early–Late Cretaceous (crown age of 98.54 Ma) on West Gondwana before the complete split between Africa and South America. Vicariance from the splitting of Gondwana may be responsible for the initial divergence in the family. However, Africa clearly served as the center of origin for much of the early diversification of the family. With this phylogenetic, temporal, and spatial framework, we review the evolution and biogeography of the family with the aim to facilitate the testing of biogeographical hypotheses about its origins, evolutionary tempo, and diversification. The current classification of the family is discussed with an extensive review of the extant diversity and distribution of species, molecular and morphological evidence supporting the current classification scheme, and the evidence informing our understanding of the biogeographical history of the family.

Current morphometric methods that comprehensively measure shape cannot compare the disparate leaf shapes found in seed plants and are sensitive to processing artifacts. We explore the use of persistent homology, a topological method applied as a filtration across simplicial complexes (or more simply, a method to measure topological features of spaces across different spatial resolutions), to overcome these limitations. The described method isolates subsets of shape features and measures the spatial relationship of neighboring pixel densities in a shape. We apply the method to the analysis of 182,707 leaves, both published and unpublished, representing 141 plant families collected from 75 sites throughout the world. By measuring leaves from throughout the seed plants using persistent homology, a defined morphospace comparing all leaves is demarcated. Clear differences in shape between major phylogenetic groups are detected and estimates of leaf shape diversity within plant families are made. The approach predicts plant family above chance. The application of a persistent homology method, using topological features, to measure leaf shape allows for a unified morphometric framework to measure plant form, including shapes, textures, patterns, and branching architectures.

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