Systematics/Phytogeography / Taxonomie/ Section
Philbrick, C. Thomas , Bove, Claudia P. .
Endemism in Podostemaceae in Central and S. America.
Podostemaceae are restricted to habitats often heavily impacted by human activities: tropical river-rapids and waterfalls. Damming of rivers (e.g., hydroelectric power) changes water flow and results in loss of Podostemaceae populations. It is widely reported in the literature that “most” species of Podostemaceae have narrow geographic distributions. This study assesses the degree of species endemism in the Americas. Though endemism can be defined at varying scales, it was defined narrowly for this study – a species documented from a single river (single-river endemics). Incidence of endemism was calculated for two overlapping datasets. Dr. P. van Royen’s 3-part monograph (early 1950s) was used as a standard against which to contrast current understanding of species and their distributions. Species known only from a single collection were scored as “endemic.” Based on Royen’s treatment, there were 19 genera and 172 taxa (spp., var. forms) in the Americas, 86 of which (50%) were endemics. Presently, 20 genera and 158 taxa are recognized, 62 (39%) of which are endemics. Twelve species have been described since Royen; six endemics. Reliable estimates of endemism can be developed for some genera, but not others. Examples from recent monographs of Castelnavia and Podostemum will be presented. Reduction in levels of endemism in these genera derive from two sources: documentation of broader species ranges and taxonomic change. Though few species in these genera are single-river endemics, most have relatively small geographic ranges. Many species in other genera remain known only from their type collection (e.g., Apinagia, Jenmaniella, Oserya, Rhyncholacis). Confident assessment of endemism in these genera remains elusive because of inadequate collections from many regions and poor taxonomic understanding.
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1 - Western Connecticut State University, Biological & Environmental Sciences, 181 White Street, Danbury, Connecticut, 06810, USA
2 - Universidade Federal do Rio de Janeiro, Departamento de Botânica, Museu Nacional, Quinta da Boa Vista, Rio de Janeiro, Brazil
Presentation Type: Oral Paper:Papers for Sections
Date: Wednesday, July 30th, 2008
Time: 1:30 PM