The invasive Opuntia ficus-indica homogenizes native plant species compositions in the highlands of Eritrea

Yohannes B Tesfay,Juergen Kreyling

doi:10.1007/s10530-020-02373-8

Abstract

Invasion by exotic species is recognized as one of the major threats to biodiversity. The effects of invasion by Opuntia ficus-indica (Cactaceae) on the species diversity, richness and composition of invaded communities were studied at three sites in the highlands of Eritrea, East Africa. This paper investigates whether the presence of O. ficus-indica causes a negative effect on the native biodiversity in a region rarely studied so far. The vegetation in invaded and uninvaded plots with similar habitat conditions was sampled and differences in the species composition, diversity and richness were compared between the plots. The overall plant species composition differed significantly with invasion by O. ficus-indica. The invasion by O. ficus-indica also led to a significant homogenization of community compositions. The species richness and Shannon diversity index did not differ significantly between the invaded and uninvaded plots. Nevertheless, we still detected species with significantly lower occurrence in the invaded plots (Psiadia punctulata), but also species which preferred invaded plots (Plectranthus hadiensis). We conclude that O. ficus-indica exerts a negligible effect on the species diversity and richness but that it affects species composition and that there are species which suffer due to its presence. Due to the continuous pressure of the invasion by O. ficus-indica on the species composition and dry climates, further homogenization in the native species diversity is to be expected in the future for the highlands of Eritrea.

Highlights

Invasion by introduced exotic species is recognized as one of the major environmental problems and threats to biodiversity (Di Castri et al 1989; Di Castri and Hansen 1990; Williamson 1996)
Our results showed that species composition of the plant communities was significantly homogenized by the presence of O. ficus-indica while species richness and Shannon diversity were not significantly affected by the presence of O. ficus-indica
Chen et al (2013), for example, found that Solidago canadensis invasions have resulted in community homogenization across diverse habitats and landscapes which were formerly dominated by different species

Summary

Introduction

Invasion by introduced exotic species is recognized as one of the major environmental problems and threats to biodiversity (Di Castri et al 1989; Di Castri and Hansen 1990; Williamson 1996). Invasion by exotic plant species can significantly alter the native plant community composition and ecosystem processes Even though some studies argue that plant invasions rarely cause biodiversity loss (Sax et al 2002; Gurevitch and Padilla 2004; Maskell et al 2006; Stohlgren et al 2008), others have shown significant declines in biodiversity due to introduced invasive plants (Wilcove et al 1998; Pimentel et al 2001; Pauchard and Shea 2006). Biotic homogenization is the process of increasing similarity among previously distinct communities within a specific region (Olden and Rooney 2006; Smart et al 2006) and plant invasions may cause homogenization of the natural habitats by adapting to the new environmental conditions and dominating the native vegetation (Van Kleunen et al 2010; Sol et al 2012; Morri et al 2019)

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Conclusion