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At best, conservation decisions can only be made using the data available at the time. For plants and especially in the tropics, natural history collections remain the best available baseline information upon which to base conservation assessments, in spite of well‐documented limitations in their taxonomic, geographic, and temporal coverage. We explore the extent to which changes to the plant biological record over 20 years have changed our conception of the conservation importance of 931 plant taxa, and 114 vegetation samples, recorded in forest reserves of the southwest Ghana biodiversity hotspot. 36% of species‐level assessments changed as a result of new distribution data. 12% of species accepted in 2016 had no assessment in 1996: of those, 20% are new species publications, 60% are new records for SW Ghana, and 20% are taxonomic resolutions. Apparent species ranges have increased over time as new records are made, but new species publications are overwhelmingly of globally rare species, keeping the balance of perceived rarity in the flora constant over 20 years. Thus, in spite of considerable flux at the species record level, range size rarity scores calculated for 114 vegetation samples of the reserves in 1996 and 2016 are highly correlated with each other: r(112) = 0.84, p <.0005, and showed no difference in mean score over 20 years: paired t(113) = −0.482, p =.631. This consistency in results at the area level allows for worthwhile conservation priority setting over time, and we argue is the better course of action than taking no action at all. [ABSTRACT FROM AUTHOR]

Aim: Existing phytogeographical frameworks for tropical Africa lack either spatial completeness, unit definitions smaller than the regional scale or a quantitative approach. We investigate whether physical environmental variables can be used to interpolate floristically defined vegetation units, presenting an interpolated, hierarchical, quantitative phytogeographical framework for tropical Africa, which is compared to previously defined regions. Location: Tropical mainland Africa 24°N to 24°S. Taxon: 31,046 vascular plant species and infraspecific taxa. Methods: We calculate a betasim dissimilarity matrix from a comprehensive whole‐flora database of plant species distributions. We investigate environmental correlates of floristic turnover with local non‐metric multidimensional scaling. We derive a hierarchical biogeographical framework by clustering the dissimilarity matrix. The framework is modelled using a classification decision tree method and 12 physical environmental variables to interpolate and increase the resolution of the framework across the study region. Results: Floristic turnover is related strongly to water availability and temperature, with smaller contributions from land cover, topographic ruggedness and lithology. Region can be predicted with 90% accuracy by the model. We define 19 regions and 99 districts. We find a novel arrangement of the arid regions. Regional subdivision within the savanna biome is supported with minor variation to borders. Within the forests of west and central Africa, our whole‐flora gridded regionalization supports the divisions identified by a previous analysis of trees only. Main conclusions: Physical environmental variables can be used to predict floristically defined vegetation units with very high accuracy, and the approach could be pursued for other incompletely sampled taxa and areas outside of tropical Africa. Geographical coherence is higher than in previous quantitative phytoregional definitions. For most tropical African vascular plant species, we provide predictions of which species will occur within each mapped district and region of tropical Africa. The framework should be useful for future studies in ecology, evolution and conservation. [ABSTRACT FROM AUTHOR]

Degradation, a reduction of the ecosystem's capacity to supply goods and services, is widespread in tropical forests and mainly caused by human disturbance. To maintain the full range of forest ecosystem services and support the development of effective conservation policies, we must understand the overall impact of degradation on different forest resources. This research investigates the response to disturbance of forest structure using several indicators: soil carbon content, arboreal richness and biodiversity, functional composition (guild and wood density), and productivity. We drew upon large field and remote sensing datasets from different forest types in Ghana, characterized by varied protection status, to investigate impacts of selective logging, and of illegal land use and resources extraction, which are the main disturbance causes in West Africa. Results indicate that functional composition and the overall number of species are less affected by degradation, while forest structure, soil carbon content and species abundance are seriously impacted, with resources distribution reflecting the protection level of the areas. Remote sensing analysis showed an increase in productivity in the last three decades, with higher resiliency to change in drier forest types, and stronger productivity correlation with solar radiation in the short dry season. The study region is affected by growing anthropogenic pressure on natural resources and by an increased climate variability: possible interactions of disturbance with climate are also discussed, together with the urgency to reduce degradation in order to preserve the full range of ecosystem functions. [ABSTRACT FROM AUTHOR]

We evaluated the relative importance of annual rainfall, temperature and their seasonality to tree species distribution in Ghana. We used species presence/absence data from 2505 1-ha plots systematically distributed over Ghana's forests. Logistic regression was used to determine species responses to four climatic variables generated from the Worldclim database. The distribution of 95% of 20 species was significantly associated with annual rainfall, 60% with rainfall seasonality, 45% with isothermality and 40% with temperature seasonality. Annual rainfall explained on average most of the variation (17%, range = 0.5–52%) in species distribution, followed by rainfall seasonality 5% (range = 0.5–27%), isothermality 4% (range = 0.8–24%) and temperature seasonality 1% (range = 0.4–4.5%). Our results suggest that, out of the climatic variables investigated, rainfall is the main factor determining tree species distribution in Ghana; temperature also influences the distribution of a number of species, although it explains much less of the variation. The reduction in annual rainfall that prevailing climate-change scenarios predict for the region will result in a shift in the distribution of most species, whereas the predicted increase in temperature variation is likely to have little effect. [ABSTRACT FROM PUBLISHER]

Gilbertiodendron tonkolili Burgt & Estrella sp. nov. (Leguminosae-Caesalpinioideae) is described and illustrated. The new species is endemic to a small area in central Sierra Leone. Gilbertiodendron tonkolili is characterised by leaves bearing 4-6 pairs of leaflets; stipules comprising a lower auriculate and an upper linear part, cream-white coloured bracteoles and a pale yellow adaxial petal. The fruits have a single longitudinal vein (sometimes a second partial vein). We assess G. tonkolili here as 'Critically Endangered' (CR) under the 2001 criteria of IUCN. We judge it to be morphologically closest to G. bilineatum which we confirm here as 'Vulnerable' (VU) and for which we also provide a full description and an illustration. A table of characters useful in differentiating the two species is given and a distribution map of both species is included. [ABSTRACT FROM AUTHOR]

ABSTRACT Plant morphological and physiological traits affect the way plants tolerate environmental stresses and therefore play an important role in shaping species distribution patterns in relation to environmental gradients. Despite our growing knowledge on the role of functional traits in structuring plant communities, few studies have tested their importance at large scales in the wet tropics. Here, we describe the distribution patterns of the most important West African rain forest timber species along the regional rainfall gradient and relate them to their functional traits. We found that the distribution patterns of 25 out of the 31 studied species (80%) were significantly related to mean annual rainfall. Shade tolerance and drought resistance were identified as the main strategy axes of variation. Wood density and leaf deciduousness emerged as the best predictor traits of species position along the rainfall gradient, explaining respectively 32 and 15 percent of the variation. Species traits tended to show stronger relationships with estimated optimum annual rainfall for each species than to the extreme rainfall conditions where they occur. The significant role of rainfall in shaping timber species distribution and the strong relationships between species traits and rainfall indicate that changes in climate, especially declining rainfall, could have strong effects on species composition and abundance in these tropical forests. [ABSTRACT FROM AUTHOR]

Our aim was to evaluate the extent to which we can predict and map tree alpha diversity across broad spatial scales either by using climate and remote sensing data or by exploiting spatial autocorrelation patterns. Tropical rain forest, West Africa and Atlantic Central Africa. Alpha diversity estimates were compiled for trees with diameter at breast height ≥ 10 cm in 573 inventory plots. Linear regression (ordinary least squares, OLS) and random forest (RF) statistical techniques were used to project alpha diversity estimates at unsampled locations using climate data and remote sensing data [Moderate Resolution Imaging Spectroradiometer (MODIS), normalized difference vegetation index (NDVI), Quick Scatterometer (QSCAT), tree cover, elevation]. The prediction reliabilities of OLS and RF models were evaluated using a novel approach and compared to that of a kriging model based on geographic location alone. The predictive power of the kriging model was comparable to that of OLS and RF models based on climatic and remote sensing data. The three models provided congruent predictions of alpha diversity in well-sampled areas but not in poorly inventoried locations. The reliability of the predictions of all three models declined markedly with distance from points with inventory data, becoming very low at distances > 50 km. According to inventory data, Atlantic Central African forests display a higher mean alpha diversity than do West African forests. The lower tree alpha diversity in West Africa than in Atlantic Central Africa may reflect a richer regional species pool in the latter. Our results emphasize and illustrate the need to test model predictions in a spatially explicit manner. Good OLS or RF model predictions from inventory data at short distance largely result from the strong spatial autocorrelation displayed by both the alpha diversity and the predictive variables rather than necessarily from causal relationships. Our results suggest that alpha diversity is driven by history rather than by the contemporary environment. Given the low predictive power of models, we call for a major effort to broaden the geographical extent and intensity of forest assessments to expand our knowledge of African rain forest diversity. [ABSTRACT FROM AUTHOR]

The intermediate disturbance hypothesis (IDH) predicts local species diversity to be maximal at an intermediate level of disturbance. Developed to explain species maintenance and diversity patterns in species-rich ecosystems such as tropical forests, tests of IDH in tropical forest remain scarce, small-scale and contentious. We use an unprecedented large-scale dataset (2504 one-hectare plots and 331 567 trees) to examine whether IDH explains tree diversity variation within wet, moist and dry tropical forests, and we analyse the underlying mechanism by determining responses within functional species groups. We find that disturbance explains more variation in diversity of dry than wet tropical forests. Pioneer species numbers increase with disturbance, shade-tolerant species decrease and intermediate species are indifferent. While diversity indeed peaks at intermediate disturbance levels little variation is explained outside dry forests, and disturbance is less important for species richness patterns in wet tropical rain forests than previously thought. [ABSTRACT FROM AUTHOR]

Numerous linear taxon sequences can be generated from large phylogenetic trees raising questions about what criteria should be used to select an optimal sequence for collections of specimens and published taxonomic outputs including field guides. Possible criteria and ways to implement them are discussed in relation to the sequence of Angiosperm families proposed by Haston & al. (2007). We define a particular spatial arrangement in one or more dimensions of the terminal nodes of a tree as a projection of that tree; a projection method is the set of rules by which the projection is achieved. We show that the projection of the Angiosperm phylogeny to a linear sequence, proposed by Haston & al. (2007), is not ideal because it is incompletely optimized for incompletely specified criteria. Tree projection methods that promote stability and incorporation of morphological data used in herbaria and other identification guides are proposed. [ABSTRACT FROM AUTHOR]

1. Comparative analyses of diversity variation among and between regions allow testing of alternative explanatory models and ideas. Here, we explore the relationships between the tree α-diversity of small rain forest plots in Africa and in Amazonia and climatic variables, to test the explanatory power of climate and the consistency of relationships between the two continents. 2. Our analysis included 1003 African plots and 512 Amazonian plots. All are located in old-growth primary non-flooded forest under 900 m altitude. Tree α-diversity is estimated using Fisher's alpha calculated for trees with diameter at breast height ≥ 10 cm. Mean diversity values are lower in Africa by a factor of two. 3. Climate-diversity analyses are based on data aggregated for grid cells of 2.5 × 2.5 km. The highest Fisher's alpha values are found in Amazonian forests with no climatic analogue in our African data set. When the analysis is restricted to pixels of directly comparable climate, the mean diversity of African forests is still much lower than that in Amazonia. Only in regions of low mean annual rainfall and temperature is mean diversity in African forests comparable with, or superior to, the diversity in Amazonia. 4. The climatic variables best correlated with the tree α-diversity are largely different in the African and Amazonian data, or correlate with African and Amazonian diversity in opposite directions. 5. These differences in the relationship between local/landscape-scale α-diversity and climate variables between the two continents point to the possible significance of an array of factors including: macro-scale climate differences between the two regions, overall size of the respective species pools, past climate variation, other forms of long-term and short-term environmental variation, and edaphics. We speculate that the lower α-diversity of African lowland rain forests reported here may be in part a function of the smaller regional species pool of tree species adapted to warm, wet conditions. 6. Our results point to the importance of controlling for variation in plot size and for gross differences in regional climates when undertaking comparative analyses between regions of how local diversity of forest varies in relation to other putative controlling factors. [ABSTRACT FROM AUTHOR]

1 Competition for light is a central issue in ecological questions concerning forest tree differentiation and diversity. Here, using 213 106 individual stem records derived from a national survey in Ghana, West Africa, we examine the relationship between relative crown exposure, ontogeny and phylogeny for 109 canopy species. 2 We use a generalized linear model (GLM) framework to allow interspecific comparisons of crown exposure that control for stem-size. For each species, a multinomial response model is used to describe the probabilities of the relative canopy illumination classes as a function of stem diameter. 3 In general, and for all larger stems, canopy-exposure increases with diameter. Five species have size-related exposure patterns that reveal local minima above 5 cm d.b.h., but only one, Panda oleosa, shows a local maximum at a low diameter. 4 The pattern of species exposures at 10 cm diameter is consistent with two overlapping groups, of which the smaller (21 species, including most pioneers) is generally better exposed. 5 Relative illumination rankings amongst species are significantly maintained over a wide range of stem sizes. Species that are well exposed at small diameters are therefore also more likely to be well exposed at larger diameters, although two species in the most exposed 25% of species at 10 cm d.b.h. drop to the lowest illumination quartile at 40 cm d.b.h., and three demonstrate the opposite (low-to-high) pattern. 6 Species capable of achieving the largest diameters are generally recorded less frequently in shade than are smaller species, even when compared as saplings, suggesting that species achieving large mature sizes are generally shade intolerant when small. Controlling for phylogeny reveals that this relationship holds across independent lineages. 7 We also find evidence that the range of strategies encountered is influenced by disturbance regimes. 8 We interpret our results as indicating a continuum of strategies that reflect an evolutionary trade-off between a species’ mature size and its general shade-tolerance, in combination with differentiation based on disturbance based opportunities. Species that appear similar can therefore remain ecologically distinct over their lifetimes. [ABSTRACT FROM AUTHOR]

Elephant populations have declined greatly in the rain forests of Upper Guinea (Africa, west of the Dahomey Gap). Elephants have a number of well-known influences on vegetation, both detrimental and beneficial to trees. They are dispersers of a large number of woody forest species, giving rise to concerns that without elephants the plant diversity of Upper Guinean forest plant communities will not be maintained. This prospect was examined with respect to four sources of inventory and research data from Ghana, covering nearly all (more than 2000) species of forest plant. Evidence supporting the hypothesis that plant populations are collapsing without elephants is conspicuously absent in these datasets, although Balanites wilsoniana is likely to suffer dramatically on a centennial scale in the absence of forest elephants. A few other species are likely to decline, although at an even slower rate. In the context of other processes current in these forests, loss of elephants is an insignificant concern for plant biodiversity. Elephant damage of forests can be very significant in Africa, but loss of this influence is more than compensated for by human disturbance. Elephants have played a significant part in the shaping of West African rain forest vegetation. However, it is the conservation of elephants that should be of primary concern. Tree populations should be managed to promote them, rather than vice versa. [ABSTRACT FROM PUBLISHER]