Ploidy influences rarity and invasiveness in plants

Abstract

Summary1. The factors associated with plant species' endangerment and (conversely) invasiveness are of broad interest due to their potential value in explaining the causes and consequences of population status. While most past work has focussed on ecological variables, recent work suggests that genetic attributes may be strongly associated with plant species status. 2. We collated data on chromosome numbers for 640 endangered species (worldwide) and their 9005 congeners, and for 81 invasive species and their 2356 congeners. We related ploidy (diploid versus polyploid) to endangerment and invasiveness. We also related chromosome number (absolute number and relative to the minimum recorded for the genus) to endangerment and invasiveness with a randomization test, taking the variation of reported chromosome numbers into account. All analyses considered the relatedness of the taxa. 3. We found that endangered plants are disproportionately likely to be diploid and to have lower ploidy ratios, whilst invasive plant species are generally found to have high chromosome counts and to be polyploid. 4. While considering the effect of relatedness, being endangered is c. 8% less likely as ploidy ratio doubles and 14% less likely for polyploids compared with diploids. Being invasive is 12% more likely as chromosome number doubles and 20% more likely for polyploids compared with diploids. There was no significant effect of raw chromosome number on endangerment or of ploidy ratio on invasiveness.5. Our findings demonstrate the importance of genomic attributes as risk factors of vulnerability to endangerment or invasiveness in higher plant species, and raise interesting questions as to potential causes of the pattern. 6. Synthesis. Our findings generate new hypotheses on plant rarity and invasiveness influenced by genomic attributes and further our understanding of the role of ploidy in rarity and invasiveness in higher plants. The cause of these relationships are potentially complex, requiring further research; ultimately, understanding the mechanistic basis of population status could aid conservation programs seeking to identify potentially endangered or invasive species.

Can enemy release explain the invasion success of the diploid Leucanthemum vulgare in North America?

“…Polyploidy has been proposed to be associated with invasiveness in plants (Müller-Schärer et al 2004;Pandit et al 2011Pandit et al , 2014te Beest et al 2012;Hahn et al 2012a), through, for instance, increased phenotypic variation, fixed heterosis or reduced inbreeding depression, which may pre-adapt polyploids to become invasive or increase their ability to adapt to novel conditions post-introduction (Soltis and Soltis 2000;Comai 2005; te Beest et al 2012, Hahn et al 2012b. Polyploidy has been found to be overrepresented in invasive plants (Pandit et al 2011(Pandit et al , 2014 and in various taxa with more than one ploidy level in the native range, only polyploids have become invasive (e.g.…”

The time lag between introduction and escape from cultivation of alien woody plant species decreases with polyploidization

“…Polyploids are on average more successful invaders (e.g. Stebbins, 1971;Lee, 2002;Pandit et al, 2006Pandit et al, , 2011Hijmans et al, 2007;Stenberg et al, 2003;Schlaepfer et al, 2008). A number of mutually non-exclusive mechanisms have been proposed to explain this observation (Soltis and Soltis, 2000): (i) polyploid species generally maintain higher levels of heterozygosity than their diploid relatives providing the evolutionary potential to evolve adaptive and competitive genotypes.…”

“…For instance polyploids invest more in the production of shoots and rhizomes increasing competitiveness (Schlaepfer et al, 2010). Thus, it is not surprising that the world's worst weeds are polyploids (Brown and Marshall, 1981) and that polyploids occur in higher frequencies among alien plants (Pandit et al, 2006(Pandit et al, , 2011te Beest et al, 2012).…”

The polyploid nature of Cenchrus ciliaris L. (Poaceae) has been overlooked: new insights for the conservation and invasion biology of this species – a review

“…Indeed, the lack of strong correlations observed between geographical structure and either the AFLP data or the heritable phenotypes, the existence of genotypic variations within offspring and the various origins of pentaploids, suggest that long-distance gene exchange, hybridisation and genomic evolution processes all occur in C. ciliaris. This new evidence provides insights into the genetic diversity of C. ciliaris supporting the complex and highly dynamic nature of polyploid plants (Soltis and Soltis 2000), which is a key element in restoration ecology, and also in the context of invasion biology (Pandit 2006;Ainouche et al 2009;Hull-Sanders et al 2009;Treier et al 2009;Pandit et al 2011). In this context, te Beest et al (2012) demonstrated that polyploidy might increase the adaptive potential of invasive species in their novel habitat.…”

“…Polyploidy could give introduced species an important advantage in negotiating novel habitats during the colonisation process (Richardson et al 2000). In this context, Pandit et al (2011) and te Beest et al (2012) suggest that the success of invasive plants can be enhanced by polyploidisation (whole genome duplication), where polyploids have a higher survival rate and fitness than diploids. Until now, the polyploid nature of C. ciliaris has been neglected in the programs of conservation and restoration in the native range of the species and also in the context of biological invasion.…”