Do plant families with contrasting functional traits show similar patterns of endemism? A case study with Central African Orchidaceae and Rubiaceae

Biodiversity and Conservation - Tập 20 - Trang 1507-1531 - 2011
Vincent Droissart1,2,3, Bonaventure Sonké4,5,3, Olivier J. Hardy5, Murielle Simo4, Hermann Taedoumg4, Charlemagne K. Nguembou4, Tariq Stévart2,3,6
1Unité Mixte de Recherche AMAP—Botanique et Bioinformatique de l’Architecture des Plantes, Institut de Recherche pour le Développement (IRD), Montpellier Cedex 5, France
2Herbarium et Bibliothèque de Botanique africaine, Faculté des Sciences, Université Libre de Bruxelles, Brussels, Belgium
3Missouri Botanical Garden, Africa and Madagascar Department, St. Louis, USA
4Laboratoire de Botanique Systématique et d’Ecologie, Département des Sciences Biologiques, Ecole Normale Supérieure, Université de Yaoundé I, Yaoundé, Cameroon
5Service Evolution Biologique et Ecologie, Faculté des Sciences, Université Libre de Bruxelles, Brussels, Belgium
6National Botanic Garden of Belgium, Domein van Bouchout, Meise, Belgium

Tóm tắt

The influence of functional traits on floristic patterns remains poorly understood in tropical rain forests. This contribution explores whether patterns of endemism of plant species are influenced by their life form and mode of dispersal. We used a comprehensive dataset of 3650 georeferenced plant specimens collected in Cameroon belonging to 115 taxa of Orchidaceae and 207 Rubiaceae endemic to Atlantic Central Africa. Species diversity of each family was compared using raw species richness (SR) and an index of species diversity (S k ) using subsampling procedure to correct for sampling bias. Measures were compared at three scales (square grids of one half-degree and one-degree per side and ecoregions) and according to elevation and continentality gradients. Species similarity between grid cells was measured using the sample-size corrected NNESS index. For both families, SR and S k decreased along the continentality gradient. In forest habitats below 1500 m altitude, both Orchidaceae and Rubiaceae show similar endemism patterns, but they differ in intensity. At higher altitudes, S k is higher for orchids due to the presence of endemic terrestrial taxa in grasslands, where the endemic Rubiaceae flora is rather poor. Substantial endemism observed at the ecoregion level and turnover analysis supported the role of the Sanaga River as a phytogeographical boundary. Similar endemism patterns were observed in lowland forests for Orchidaceae and Rubiaceae, even though Orchidaceae are assumed to have better long distance dispersal capabilities. The dispersal ability of Orchidaceae could be limited by the need of specific mycorhizal fungi for seed germination or host specificity for epiphytic orchids.

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