Introduction to “Ecological and Evolutionary Consequences after Invaders Hybridize”

Abstract

The motivation for this special issue was a symposium organized by Ayres and Schierenbeck at the 2006 American Botanical Society annual meeting that took its title from Ellstrand and Schierenbeck’s highly cited 2000 paper in Proceedings of the National Academy of Science, ‘‘Hybridization as a Stimulus for the Evolution of Invasiveness’’. Ellstrand was the keynote speaker. As explored previously by Ellstrand and Schierenbeck (2000), the mixing of divergent genotypes can result in the creation of populations of hybrids that are more invasive than the parental species. The symposium sparked such interest in the participants and audience that Ellstrand suggested we collaborate on a special issue. Here we revisit the earlier examples (Schierenbeck and Ellstrand 2009), and in a series of papers, present case studies examining the ecological and evolutionary consequences of hybridization in plants which range from hybridization between cultivars in ornamental pears (Culley and Hardiman 2008), to introgressive hybridization between species (Gaskin and Kazmer 2008; Sloop et al. 2009), to the formation of diploid (Abbott et al. 2008) and allopolyploid hybrid species (Ainouche et al. 2008; Ayres et al. 2008). We also consider the interplay between sexual and clonal reproduction in invaders (Bailey et al. 2008) whether hybrid plants are by their nature more invasive than non-hybridized taxa in a meta-analysis (Whitney et al. 2008), and outline approaches to modeling hybrid population dynamics (Hall and Ayres 2008). The case studies should serve as cautionary tales against the casual introduction of nonnative taxa into areas occupied by conspecifics or congeners while this special issue illustrates the potential for hybrid studies to increase our understanding of evolution.