12 research outputs found

    Consistent patterns of common species across tropical tree communities

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    Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations 1–6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories 7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees

    Crocins, the active constituents of Crocus Sativus L., counteracted ketamine-induced behavioural deficits in rats

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    Experimental evidence indicates that the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist ketamine impairs cognition and can mimic certain aspects of positive and negative symptoms of schizophrenia in rodents. Crocins are among the active components of the plant Crocus sativus L. and were found to be effective in different models of psychiatric disorders including anxiety and depression. The present study was designed to investigate the ability of crocins to counteract schizophrenia-like behavioural deficits produced by ketamine in rats. Crocin's ability to counteract hypermotility, stereotypies and ataxia induced by ketamine was evaluated in a motor activity cage. The ability of crocins to reverse ketamine-induced memory deficits was assessed using the novel object recognition task (NORT). The social interaction test was used in order to examine the effects of crocins on ketamine-induced social withdrawal. Crocins (50 but not 30 mg/kg, i.p.) attenuated ketamine (25 mg/kg, i.p.)-induced hypermotility, stereotypies and ataxia. In a subsequent study, post-training administration of crocins (15 and 30 mg/kg, i.p.) reversed ketamine (3 mg/kg, i.p.)-induced performance deficits in the NORT. Finally, crocins (50 but not 30 mg/kg, i.p.) counteracted the ketamine (8 mg/kg, i.p.)-induced social isolation in the social interaction test. Our findings show that crocins attenuated schizophrenia-like behavioural deficits induced by the non-competitive NMDA receptor antagonist ketamine in rats

    Effects of the Nitric Oxide Synthase Inhibitor L-NAME on Recognition and Spatial Memory Deficits Produced by Different NMDA Receptor Antagonists in the Rat

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    There is consistent experimental evidence that noncompetitive antagonists of the N-methyl-D-aspartate (NMDA) receptor, such as ketamine, MK-801, and phencyclidine (PCP), impair cognition and produce psychotomimetic effects in rodents. Nitric oxide (NO) is considered as an intracellular messenger in the brain. The implication of NO in learning and memory is well documented. This study was designed to investigate the ability of the NO synthase inhibitor L-NAME to antagonize recognition and spatial memory deficits produced by the NMDA receptor antagonists, MK-801 and ketamine, in the rat. L-NAME (1-3 mg/kg) counteracted MK-801-(0.1 mg/kg) and ketamine (3 mg/kg)-induced performance impairments in the novel object recognition task. L-NAME (10 mg/kg) attenuated ketamine (15 mg/kg)-induced spatial working memory and retention deficits in the radial water maze paradigm. L-NAME, applied at 3 mg/kg, however, disrupted rodents' performance in this spatial memory task. The present findings indicate (1) that L-NAME is sensitive to glutamate hypofunction produced by other than PCP NMDA antagonists such as MK-801 and ketamine and (2) that L-NAME alone differentially affects rodents' spatial memory. Neuropsychopharmacology (2010) 35, 2357-2366; doi: 10.1038/npp.2010.109; published online 21 July 201
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