Feddes Repertorium 123 (2012) 1, 55 – 66 © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 0014-8962/12/102-0055 Research Paper Nanism and ephemerism as reasons for a hidden abundance in vernal pool plants: The example of Lepuropetalon spathulatum in Chile MIGUEL ALVAREZ *,1 ; JOSÉ SAN MARTÍN 2 & ULRICH DEIL 3 1 INRES-Vegetation Ecology, University of Bonn, Germany 2 Instituto de Biología Vegetal y Biotecnología, Universidad de Talca, Chile 3 Faculty of Biology, Dept. of Geobotany, University of Freiburg, Germany Keywords: antitropical disjunction, Mediterranean biome, Nanojuncetea australis, wetland ecology * Corresponding author: INRES-Vegetation Ecology, University of Bonn, Nussallee 9, 53115 Bonn, Germany; Phone: +49-(0)228-73-1669; Fax: +49-(0)228-73-2489, E-mail: malvarez@uni-bonn.de Accepted for publication: September 16 th , 2012 DOI 10.1002/fedr.201200016 Abstract Minute size (nanism) and short live cycle (ephemer- ism) are characteristic features of many plants living in seasonal wetlands in Mediterranean biomes. Lepu- ropetalon (Celastraceae) is a monotypic genus with an antitropical distribution (disjunct in temperate regions of both Americas). L. spathulatum is the smallest vascular plant of Chile, not recorded in herbaria for decades. Its distribution, ecology and phytosociology were studied based on herbarium vouchers and field observations. L. spathulatum occurs in the fringes of vernal pools, on oligotrophic sandy soils and in grazed Acacia caven pseudo- savannas. Its distribution is linked to the Mediterra- nean and Submediterranean bioclimates. Associated species are other dwarfish annuals, many of them originating from the Western Palearctic subkingdom and characteristic for the class Isoëto-Nanojuncetea. Other floristic elements are Chilean endemics and species with a disjunction to California (character species of the Nanojuncetea australis). L. spathula- tum is not a rare plant in Chile, but is often over- looked because of its dwarfish and ephemeral habit. Although most populations occurred in secondary habitats and the species can tolerate disturbance, intensification of agriculture, forest plantations and modification of the hydrological conditions may threaten the species in the long term. 1 Introduction Even today, the study of vascular plants in sea- sonal wetlands can result in the discovery of new taxa (see for example Juncus maroccanus, Juncaceae, in KIRSCHNER et al. 2004). One reason is that many species in this habitat are dwarfish and therefore easily overlooked. Diels (1906) already coined the terminus “Zwerg- flora” (dwarf flora) when studying floodplain vegetation in SW Australia. Another reason is that the species in this environment can escape the observation because they are very short living annuals, or perennials with a very brief appearance above ground. Nanism and ephe- merism are characteristic features of the sea- sonal wetland flora, especially in Mediterra- nean biomes. These wetlands, filled with rain- water in winter and desiccating in early sum- mer, are named vernal pools, because the main vegetation period is springtime (DEIL 2005). Still more often these habitats allow new findings of already known plant species, even in floristically well explored areas (e.g. J. ma- roccanus was first documented for Europe in 2011 by RUDNER & DEIL). Another example