Tropical Ecology and Conservation [Monteverde Institute]


Angela Braun



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Publication Date

September 2000


Non-native species tend to proliferate in disturbed areas and may be well-suited to the conditions found there (Noss and Csuti, 1997). The effect of an exotic species, Impatiens walleriana, on plant species diversity at path edges was examined in the San Luis Valley, Monteverde, Costa Rica. Morphospecies of plants in 1m x 1m plots were collected and abundances for each recorded for 19 paired plots (38 total) with and without I. walleriana. Shannon-Wiener Diversity Indices were calculated twice for the plots with I. walleriana (accounting and discounting for the presence of I. walleriana) and once without I. walleriana (mean H’ values – 1.534, 1.754, and 1.767 respectively). No significant difference was found between the mean H’ values for the plots with I. walleriana (either accounting for or discounting for their abundance) and the plots without I. walleriana using a Paired Sign Test. An overall H’ was also calculated and compared with a modified t-test. A significant difference was found between the plots with I. walleriana (including their abundance) and the plots without, suggesting that the presence of I. walleriana affects the local species diversity. Additionally, light intensity and soil temperature were recorded a minimum of three times per plot at morning, noon and evening time periods. Only morning temperature exhibited any significant differences, but significant differences were found for all light measurements at all time periods with plots containing I. walleriana receiving higher amounts of light.


Una especie exotica, Impatiens walleriana (Balsaminaceae) tiene efectos en la composición de plantas en el Valle de San Luis, Monteverde, Costa Rica. Se registraron las morfo-especies de plantas y las cantidades en cada una en parcelas de 1m x 1m. Se registraron un total de 38 parcelas, 19 eran en el tratamiento con I. walleriana y 19 sin I. walleriana. El Indice de diversidad Shannon-Wiener fue calculado dos veces en las parcelas con I. walleriana (incluyendo esta especie y sin incluirla) y una vez por las parcelas sin I. walleriana. No hubo una diferencia significativa en H’ entre las parcelas con I. walleriana (incluyéndolas o sin incluirlas) y cuando no estaba presente (Paired Sign Test). Un H’ total fue calculada y se comparo con un Modified t-test. Hubo una diferencia significativa entre las parcelas con I. walleriana (incluyendo esta especie y sin incluirla) y las parcelas sin I. walleriana. Este resultado indica, que la presencia de I. walleriana afecta negativamente la diversidad de especies de plantas. La intensidad de luz y la temperatura de la tierra fue medida por cada parcela en la mañana, al medio día y en la tarde. Solamente la temperatura por la mañana exhibía una diferencia significativa, pero las diferencias significativas fueron encontradas por periodos de tiempo de intensidad de luz; las parcelas con I. walleriana reciben más intensidad de luz.


9 pages

Holding Location

Monteverde Institute


English; Spanish

Media Type



Digital Only





Impatiens walleriana (Balsaminaceae): Its effects on plant diversity and its abiotic habitat characteristics, September 2000



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