Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Do alien plant invasions cause biotic homogenization of terrestrial ecosystems in the Kashmir Valley, India?

Abstract

Habitat characteristics and the species attributes that determine the rate of spread of alien plant species are likely to be pivotal in determining the extent of homogenization, particularly at regional level. In order to determine which habitats are more likely to be homogenized and which groups of alien plant species promote homogenization, we sampled seven sites of each of the three habitats namely forests, grasslands, and roadsides for presence-absence of plant species. We calculated a Jaccard similarity index separately for native, alien, and native + alien species. We used the average of Jaccard dissimilarity index (1- Jaccard index) of all paired localities as a measure of the mean overall beta diversity and mean beta diversity of alien and native species for each set of localities examined in an analysis. We used a homogenization index to quantify the homogenization or differentiation effect. For habitats, we found that biotic homogenization followed the order: roadsides > grasslands > forests. The various categories of plants varied in bringing about homogenization and the following order in respect of homogenization was recorded: invasive > naturalized > casual; perennial > annual/biennial; herbs > shrubs/subshrubs/lianas > trees. Beta diversity, based on alien species, was lower for roadsides; invasive, perennial and herbaceous alien plants, than their counterparts (i.e. grasslands, forests; casual, naturalized; annual/biennial and shrubs/subshrubs/lianas and trees alien plants, respectively). Our study clearly shows that extent of biotic homogenization depends upon habitat type, and alien plant species differ in their homogenization potential depending upon stage of invasion of alien species, life span and growth form. These observations assume significance in conservation biology to predict the impact of alien plant species on ecosystems.