Global patterns of vascular plant alpha diversity.

Global patterns of regional (gamma) plant diversity are relatively well known, but whether these patterns hold for local communities, and the dependence on spatial grain, remain controversial. Using data on 170,272 georeferenced local plant assemblages, we created global maps of alpha diversity (local species richness) for vascular plants at three different spatial grains, for forests and non-forests. We show that alpha diversity is consistently high across grains in some regions (for example, Andean-Amazonian foothills), but regional 'scaling anomalies' (deviations from the positive correlation) exist elsewhere, particularly in Eurasian temperate forests with disproportionally higher fine-grained richness and many African tropical forests with disproportionally higher coarse-grained richness. The influence of different climatic, topographic and biogeographical variables on alpha diversity also varies across grains. Our multi-grain maps return a nuanced understanding of vascular plant biodiversity patterns that complements classic maps of biodiversity hotspots and will improve predictions of global change effects on biodiversity.

Species-area relationships in the Andaman and Nicobar Islands emerge because rarer species are disproportionately favored on larger islands.

The island species-area relationship (ISAR) describes how the number of species increases with increasing size of an island (or island-like habitat), and is of fundamental importance in island biogeography and conservation. Here, we use a framework based on individual-based rarefaction to infer whether ISARs result from passive sampling, or whether some processes are acting beyond sampling (e.g., disproportionate effects and/or habitat heterogeneity). Using data on total and relative abundances of four taxa (birds, butterflies, amphibians, and reptiles) from multiple islands in the Andaman and Nicobar archipelago, we examine how different metrics of biodiversity (total species richness, rarefied species richness, and abundance-weighted effective numbers of species emphasizing common species) vary with island area. Total species richness increased for all taxa, as did rarefied species richness controlling for a given sampling effort. This indicates that the ISAR did not result because of passive sampling, but that instead, some species were disproportionately favored on larger islands. For birds, frogs, and lizards, this disproportionate effect was only associated with species that were rarer in the samples, but for butterflies, both more common and rarer species were affected. Furthermore, for the two taxa for which we had plot-level data (reptiles and amphibians), within-island ß-diversity did not increase with island size, suggesting that within-island compositional effects were unlikely to be driving these ISARs. Overall, our results indicate that the ISARs of these taxa are most likely driven by disproportionate effects, that is, where larger islands are important sources of biodiversity beyond a simple sampling expectation, especially through their influence on rarer species, thus emphasizing their role in the preservation and conservation of species.

Phylogenetic classification of the world's tropical forests.

Knowledge about the biogeographic affinities of the world's tropical forests helps to better understand regional differences in forest structure, diversity, composition, and dynamics. Such understanding will enable anticipation of region-specific responses to global environmental change. Modern phylogenies, in combination with broad coverage of species inventory data, now allow for global biogeographic analyses that take species evolutionary distance into account. Here we present a classification of the world's tropical forests based on their phylogenetic similarity. We identify five principal floristic regions and their floristic relationships: (i) Indo-Pacific, (ii) Subtropical, (iii) African, (iv) American, and (v) Dry forests. Our results do not support the traditional neo- versus paleotropical forest division but instead separate the combined American and African forests from their Indo-Pacific counterparts. We also find indications for the existence of a global dry forest region, with representatives in America, Africa, Madagascar, and India. Additionally, a northern-hemisphere Subtropical forest region was identified with representatives in Asia and America, providing support for a link between Asian and American northern-hemisphere forests.

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.

The potential for crop to wild hybridization in eggplant (Solanum melongena; Solanaceae) in southern India.

UNLABELLED: • PREMISE OF THE STUDY: In India and elsewhere, transgenic Bt eggplant (Solanum melongena) has been developed to reduce insect herbivore damage, but published studies of the potential for pollen-mediated, crop- to- wild gene flow are scant. This information is useful for risk assessments as well as in situ conservation strategies for wild germplasm.• METHODS: In 2010-2014, we surveyed 23 populations of wild/weedy eggplant (Solanum insanum; known as wild brinjal), carried out hand-pollination experiments, and observed pollinators to assess the potential for crop- to- wild gene flow in southern India.• KEY RESULTS: Wild brinjal is a spiny, low-growing perennial commonly found in disturbed sites such as roadsides, wastelands, and sparsely vegetated areas near villages and agricultural fields. Fourteen of the 23 wild populations in our study occurred within 0.5 km of cultivated brinjal and at least nine flowered in synchrony with the crop. Hand crosses between wild and cultivated brinjal resulted in seed set and viable F1 progeny. Wild brinjal flowers that were bagged to exclude pollinators did not set fruit, and fruit set from manual self-pollination was low. The exserted stigmas of wild brinjal are likely to promote outcrossing. The most effective pollinators appeared to be bees (Amegilla, Xylocopa, Nomia, and Heterotrigona spp.), which also were observed foraging for pollen on crop brinjal.• CONCLUSION: Our findings suggest that hybridization is possible between cultivated and wild brinjal in southern India. Thus, as part of the risk assessment process, we assume that transgenes from the crop could spread to wild brinjal populations that occur nearby.

Genetic diversity and population structure of wild/weedy eggplant (Solanum insanum, Solanaceae) in southern India: implications for conservation.

UNLABELLED: • PREMISE OF THE STUDY: Crop wild relatives represent important genetic resources for crop improvement and the preservation of native biodiversity. Eggplant (Solanum melongena), known as brinjal in India, ranks high among crops whose wild gene pools are underrepresented in ex situ collections and warrant urgent conservation. Knowledge of outcrossing rates and patterns of genetic variation among wild populations can aid in designing strategies for both in situ and ex situ preservation.• METHODS: We used 14 microsatellite (simple sequence repeat) markers to examine genetic diversity, population structure, and outcrossing in 10 natural populations of wild/weedy eggplant (S. insanum = S. melongena var. insanum) and three cultivated populations in southern India.• KEY RESULTS: Multilocus FST analyses revealed strong differentiation among populations and significant isolation by distance. Bayesian model-based clustering, principal coordinate analysis, and hierarchical cluster analysis grouped the wild/weedy populations into three major clusters, largely according to their geographic origin. The three crop populations were similar to each other and grouped with two wild/weedy populations that occurred nearby. Outcrossing rates among the wild/weedy populations ranged from 5-33%, indicating a variable mixed-mating system.• CONCLUSION: Geographic isolation has played a significant role in shaping the contemporary patterns of genetic differentiation among these populations, many of which represent excellent candidates for in situ conservation. In two cases, close genetic affinity between cultivars and nearby wild/weedy populations suggests that gene flow has occurred between them. To our knowledge, this is the first study investigating population-level patterns of genetic diversity in wild relatives of eggplant.

Do developmental initiatives influence local attitudes toward conservation? A case study from the Kalakad-Mundanthurai Tiger Reserve, India.

We evaluated the conservation attitudes of the local villagers living adjacent to the Kalakad-Mundanthurai Tiger Reserve in southern India 6 years after implementation of a World Bank funded eco-development project. We assessed attitudes towards three facets of conservation: the tiger, an emblematic species signifying India's commitment to wildlife conservation; the forest, a principle source of fuel-wood and other products; and the Forest Department, which manages the forest. More specifically we predicted that (i) attitudes would be an effective predictor of resource use interest in the forest and (ii) benefits obtained from the EDP would create more favorable attitudes towards conservation and the protected area employees. Twelve villages located within 3 km from the reserve boundary were chosen and 2-3% of the households interviewed with regard to their attitudes towards these three facets of conservation, their household resource use patterns, wealth, sex, age and length of residency. We found significant associations between wealth, sex, age and both tiger and forest conservation. Providing benefits has not changed the underlying attitudes of the communities. The poorer sections of society, whether receiving benefits or not, tended to support tiger conservation because conserving wildlife did not affect their livelihood in any way, whereas both the rich and poor had misgivings about forest conservation due to dependency on forest products. We conclude that the eco-development project has not effectively addressed the most important of the local concerns.

Pollination systems of trees in Kakachi, a mid-elevation wet evergreen forest in Western Ghats, India.

A long-term survey (1990-2000) of pollination modes of 86 tree species was carried out at Kakachi, a mid-elevation wet forest site in southern Western Ghats, India. Observations were made on 86 tree species. This comprises 80% of the total arborescent species present in the site. Approximately 75% of these species were specialized to a single pollinator group such as bee, beetle, or moth. Pollinators from diverse groups pollinate the remaining 25% of the tree species. Global comparison with other wet forest sites showed that diversity and specialized pollination modes observed in Kakachi bore closer resemblance to other lowland than montane forest sites described so far. However, the number of pollinators involved in pollination was comparable with montane sites. We examine the consequences that might have led to selection of the observed pollination modes in Kakachi. We discuss the conservation implications of these results.

Determinants of fruit and seed set in Pavonia dasypetala (Malvaceae).

Female reproductive success (fruit and seed set) in Pavonia dasypetala (Malvaceae) was only weakly related to pollinator attentiveness (number of pollinator visits and number of pollen grains deposited on stigmas). This result has implications for field studies of pollination: observational measures of pollinator attentiveness do not necessarily provide an, accurate basis for inferring reproductive success. Further, these results indicate that, although pollination is essential for seed set in this species, reproduction is not limited by pollination. Many flowers that were visited numerous times by hummingbirds and that received pollen in excess of the number of ovules per flower failed to produce fruits. If pollen is limiting, it is pollen quality rather than quantity that is inadequate. Patterns of reproduction in this species were as predicted if resource availability limits seed set (Stephenson 1981): (1) among mature fruits there was an excess of fruits with full seed set (4 or 5 seeds) and (2) probability of fruit, set decreased over the reproductive season. However, resource availability was not the only determinant of seed set in this species: there was also variation among individuals that seems unrelated to either pollen or resource availability. Reproductive success thus appears to be determined by several factors and cannot be described as simply pollen or resource limited.

Birds and neotropical mistletoes: effects on seedling recruitment.

Two groups of neotropical mistletoes differ in fruit structure and consequently in the manner their seeds are deposited by avian frugivores. Birds defecate seeds of one group in clumps, but deposit seeds of the other group singly by regurgitation. A significant proportion of adult plants of both species were found growing alone, indicating a higher mortality with seed clumping.