Flora 204 (2009) 270–277 Presence of cushion plants increases community diversity in the high equatorial Andes Petr Sklena´rˇ Department of Botany, Charles University, Bena´tska´ 2, 128 01 Prague 2, Czech Republic Received 10 December 2007; accepted 14 April 2008 Abstract Cushion plants are a common growth form in the equatorial pa´ramo vegetation and their surfaces are often colonized by other plants. This paper analyzes the effect of the cushion plants on the community diversity at 4650 m on the eastern slope of the Iliniza volcano in Ecuador. Ninety sample plots of 1 m 2 size were located in the study area and were divided into 25 subplots in which presence and abundance of plant species was recorded. The community diversity was expressed as species richness, Simpson’s diversity index, and evenness. Correlation between the cushion species and the composition of the colonists was measured with the CCA ordination analysis, correlation between the cushion cover and community diversity was measured by means of correlation analysis. Randomized species–area curves were used to compare richness of plant communities with and without the cushions. A total of 32 species were found including five cushion plants. Most species preferred to grow on the cushion surface whereas only a few species were able to colonize open ground. Species richness and Simpson’s index were significantly correlated to the cushion area but no correlation was found for evenness. The cushions were usually composed of more than one species which hampered the examination of the cushion–colonist specific relationships. Nevertheless, cushions of Azorella and Arenaria seemed to provide more favorable habitat for colonization than the other cushion species. Comparison with an earlier study made on Iliniza indicates that the presence of the cushions significantly increases the richness of the plant community. r 2008 Elsevier GmbH. All rights reserved. Keywords: Ecuador; Nurse plant; Pa´ramo; Plant community diversity; Species richness; Tropical alpine Introduction Cushion plants are a successful growth form in high altitude and high latitude ecosystems of the world (Ko¨rner, 2003). They are remarkably diverse in the southern hemisphere, including temperate and equator- ial Andes of South America (Badano and Cavieres, 2006a; Cleef, 1978; Godley, 1978; Heilborn, 1925). The cushion growth form is known to ameliorate the physical environment of the plant. Dead organic material which accumulates inside the cushion and provides nutrient storage in a form of slowly decom- posing tissues (Halloy, 1983; Svoboda, 1977) may be the major advantage of this growth form in harsh and unproductive alpine environments (Ko¨rner, 2003). Beside the organic material, water is preserved inside and below the cushion which may reduce the risk of water shortage to the plant (Benoist, 1935; Cavieres et al., 1998; Heilborn, 1925). The temperature of the cushion surface is usually several degrees above that of ARTICLE IN PRESS www.elsevier.de/flora 0367-2530/$ - see front matter r 2008 Elsevier GmbH. All rights reserved. doi:10.1016/j.flora.2008.04.001 E-mail address: petr@natur.cuni.cz.