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Leiden, Netherlands

Chaowasku T.,Leiden University | Kessler P.J.A.,Hortus Botanicus Leiden
Nordic Journal of Botany | Year: 2013

Seven new species of the genus Miliusa are described from Thailand (M. fragrans, M. hirsuta, M. intermedia, M. nakhonsiana, M. sessilis, M. thailandica, and M. umpangensis). A key to the 19 species of Miliusa in Thailand is provided. In addition, the complete taxonomic nomenclature of all known species of Miliusa in Thailand is given, with several new proposed synonyms. The new as well as the known species of Miliusa in Thailand are classified into four morphological groups on the basis of a combination of flower and/or inflorescence position and inner petal morphology proposed earlier. © 2013 The Authors. Source

Hoang V.S.,Hanoi University | Baas P.,National Herbarium of the Netherlands | Kessler P.J.A.,Hortus Botanicus Leiden | Slik J.W.F.,CAS Xishuangbanna Tropical Botanical Garden | And 2 more authors.
Journal of Tropical Forest Science | Year: 2011

In order to understand the influence of human disturbance and the physical environment on plant biodiversity in Ben En National Park, Vietnam, we analysed species composition and density in forest plots with diverse soils and varying degrees of human disturbance. Soil factors significantly influenced tree species composition, although they only explained 5.7% of the observed data variance. Human factors (disturbance) were second most important in explaining species composition and density, accounting for 4.4% of variance. Changes in species composition related to human disturbance varied mostly independently of soils. The species composition of slightly and heavily disturbed forest differed significantly, with species of low conservation value being most common in heavily disturbed forest, while endangered species and important timber trees were most common in least disturbed forest. Density of treelets was higher in limestone forest than in non-limestone forest. Timber trees and other useful plant species used for a whole range of non-timber forest products (NTFPs) were more abundant in the less disturbed plots, which were located far away from villages and roads. Basal area in less disturbed forest was also larger than in heavily disturbed forest, indicating that the pressures of illegal logging and harvesting were closely connected to travel distances to nearest villages. Limiting the accessibility to forest resources should therefore be a priority in forest conservation as a first step to safeguard the rich biodiversity and stocks of useful plants in the park. © Forest Research Institute Malaysia. Source

Vollering J.,Naturalis Biodiversity Center | Schuiteman A.,Herbarium | de Vogel E.,Naturalis Biodiversity Center | van Vugt R.,Hortus Botanicus Leiden | Raes N.,Naturalis Biodiversity Center
Journal of Biogeography | Year: 2016

Aim: The aims of this study were (1) to assess the spatial distribution of orchid species richness in New Guinea, and (2) to examine patterns of species turnover in the orchid community through phytogeographical regionalization. We aimed to achieve these goals using botanical collection records, species distribution models (SDMs) and partitioning around medoids (PAM) clustering. Location: New Guinea, the Bismarck Archipelago and surrounding islands. Methods: We combined 6760 collection records of 532 orchid species with 16 uncorrelated environmental predictor variables, to model species distributions at 5 arc-min resolution, using the presence-only modelling algorithm, Maxent. All SDMs were tested for significant deviation from random expectation using bias-corrected null models. The results from significant SDMs were stacked to create a map of orchid species richness. The same significant SDMs were used to derive phytogeographical regions through a PAM cluster analysis. Results: Of the 532 modelled species distributions, 283 showed significantly stronger correlation with environmental conditions than expected by chance alone. It is inferred that the central mountain ranges of eastern New Guinea, including part of the Papuan Peninsula, harbour the highest levels of orchid species richness. The study area was divided into eight phytogeographical regions that maximized internal community similarity among orchids. Two of these regions are found almost exclusively in western New Guinea, while the remainder are more evenly distributed. Main conclusions: Our study provides an objective assessment of the distribution of relative orchid species richness in New Guinea. The eight derived phytogeographical regions are largely consistent with existing knowledge of the island's internal biogeography. These findings give insight into one of the global hotspots of orchid diversity, and improve our understanding of the phytogeography of New Guinea. © 2016 John Wiley & Sons Ltd. Source

Chaowasku T.,Leiden University | Kessler P.J.A.,Hortus Botanicus Leiden
Nordic Journal of Botany | Year: 2014

The genus Miliusa in Cambodia and Vietnam is reviewed. Cambodia and Vietnam each harbors six species of Miliusa, including three which are described as new to science: one from Cambodia (Miliusa cambodgensis sp. nov.), the other two from Vietnam (M. astiana and M. ninhbinhensis spp. nov.). In addition, a complete nomenclature and relevant information about the Miliusa species previously known from Cambodia and Vietnam are provided, including keys to the Cambodian and Vietnamese species, the designation of a lectotype for M. baillonii and the synonymization of M. balansae var. elongatoides, M. chunii and M. sinensis with M. balansae. © 2014 The Authors. Source

Couvreur T.L.P.,IRD Montpellier | Maas P.J.M.,Wageningen University | Meinke S.,Hortus Botanicus Leiden | Meinke S.,Leiden University | And 3 more authors.
Botanical Journal of the Linnean Society | Year: 2012

Identification keys are provided for all genera currently recognized in Annonaceae. Separate keys are presented for the Neotropics (34 genera), Africa-Madagascar (40 genera) and Asia-Australasia (42 genera). These keys are based on a combination of vegetative and fertile characters. © 2012 The Linnean Society of London. Source

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