An estimate of the number of tropical tree species

The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher’s alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between ∼40,000 and ∼53,000, i.e. at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of ∼19,000–25,000 tree species. Continental Africa is relatively depauperate with a minimum of ∼4,500–6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa

Climatic stability drives latitudinal trends in range size and richness of woody plants in the Western Ghats, India.

Understanding the determinants of range location and size is fundamental to our understanding of spatial patterns in species richness. Here, we aimed to test the role of 'climatic stability' in determining latitudinal trends in range size and as a consequence on species richness of tropical woody plants. Using primary data from 156 (0.06 ha) plots comprising 20,400 occurrences of more than 400 species of tropical woody plants, we built a biome-wide species database that covers the entire latitudinal extent of the wet-evergreen forests of the Western Ghats (8o to 20o N), India. We consolidated this database using secondary data from other published species inventories. We then calculated the range sizes and climatic niche width of woody plants to test the predictions of the climatic stability hypothesis and examined the relationship between range position and climatic tolerance of species. Our results show a significant latitudinal gradient in species richness and turnover where local and regional species richness increase monotonically from higher latitudes to lower latitudes of the Western Ghats. We found strong support for Rapoport's Rule with an increase in range size from lower to higher latitudes; our results are consistent with the predictions of the climatic stability hypothesis, where species at higher latitudes exhibited greater tolerance to temperature and rainfall seasonality. Contrary to earlier work, our findings suggest that Rapoport's Rule and the climatic stability hypothesis can operate over regional scales, and even at lower latitudes. We suggest that latitude associated climatic seasonality through its influence on species ranges, can influence latitudinal patterns in species turnover as well as species richness

Environment and dispersal influence changes in species composition at different scales in woody plants of the Western Ghats, India

QuestionWhat are the relative roles of environmental and spatial factors in influencing variation in species composition of tropical woody plants at different spatial scales? LocationTropical evergreen forests, Western Ghats, South India. MethodsUsing a plot-based species inventory spanning the entire latitudinal extent (1,200km) of the Western Ghats' wet evergreen forests, we collected primary data on spatial variation in species composition of woody plants. Each plot was characterized by a set of environmental descriptors consisting of topographic, edaphic and climatic variables, while eigenvector-based spatial variables and plot coordinates were used as spatial descriptors. We used ordination-based as well as distance-based variation partitioning techniques to partition the variation in species composition into components uniquely and jointly explained by environmental and spatial factors. ResultsThe compositional similarity of woody plants largely showed a linear decline with log-geographic distance. However, this relationship was spatially structured. After controlling for the differences in environment, compositional similarity was found to be strongly associated with geographic distance only at the smallest spatial scale. Variation partitioning analysis revealed that environmental variables explained a much larger proportion of variation in species composition overall compared to spatial variables. Among environmental variables, climatic variables emerged as the most important predictors of variation in species composition at regional and landscape scales. ConclusionsStrong association between compositional similarity and geographic distance at local scales indicates the influence of dispersal limitation, while niche differentiation seems to be a more important driver of variation in species composition at larger spatial scales. Overall, our results provide evidence for scale-dependent shifts in the relative importance of factors that are responsible for variation in species composition

A new species of Reissantia (Celastraceae) from coastal Karnataka, India

Reissantia N. Halle (1958: 466) is a small but widespread genus distributed in the Old World tropics of Africa and Indo-Malaya (Ramamurthy and Naithani, 2000). Members of Reissantia are climbing, scandent or erect shrubs with decussate leaves. They are characterised by small flowers borne in dichotomous cymes or panicles with accessory branches, small calyx and corolla with imbricate aestivation, inconspicuous disc that is mostly fused with the ovary, 3 stamens inserted at the base of the carpel, 3-locular ovary and 3-fascicled capsular fruit with seeds that have a basal membranous wing. Reissantia was formerly placed under the family Hippocrateaceae but is now long considered as belonging to the major family Celastraceae as the members of Hippocrateaceae were found to be nested within Celastraceae sensu stricto (Robson et al., 1994, Savolainen et al., 1997, Takhtajan, 1997). Parsimony tree searches based on the taxon sampling used by Coughenour et al. (2010) showed all members of the tribe Hippocrateoideae to form a monophyletic group. Hippocrateaceae, as traditionally defined (e. g., Smith, 1940; Halle, 1962; Cronquist, 1981), is supported as a clade nested within a paraphyletic Celastraceae s. s. (Simmons et al., 2001a, Simmons et al., 2001b). Coughenour et al., (2011) established the monophyly of Reissantia using plastid and nuclear genes and morphological characters. Six species of Reissantia are currently recognised (Coughenour et al., 2011) of which three species, R. indica (Willd. 1797: 193) N. Halle (1958: 466), R. grahamii (Wight1839: 139) Ding Hou (1963: 33) and R. arborea (Roxb. 1811: 4) Hara (1965: 327) are reported in India. Globally, R. indica shows a wide distribution ranging from Africa, India, Sri Lanka to Philippines, Indonesia, Malaysia and Timor while R. grahamii is found in India, Vietnam, Philippines and New Guinea. R. arborea has been reported from India and China. Within India, R. indica and R. grahamii are distributed in South India while R. arborea is found in Northeast India. Here, we describe a new species of Reissantia that is morphologically distinct from the rest of its congeners with respect to multiple characters. Detailed comparisons of the new species with its morphologically most closely related species and genera is provided along with a key to the species of Reissantia reported from India (Almeida, 1996; Matthew 1982; Matthew, 1999)

Mucuna laticifera, a new species from north-eastern India

Mucuna laticifera, a new species of Fabaceae from Sikkim state of India is described and illustrated here. It can be distinguished from its closely related species by the presence of a watery latex, uniformly green to pale yellow corolla, glabrous standard and wings and parallel pod margins

The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project

The PREDICTS project—Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)—has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity