Background/Question/Methods Biological invasions are becoming increasingly common due to globablization, but we still have a limited understanding of the mechanisms underlying their success. Propagule pressure, the number of separate introductions, and the availability of suitable habitat have all been shown to increase the ability of non-native species to colonize novel habitats. Recent studies even suggest that the match between the phenotypic traits of the colonizers and the novel environment also contributes to establishment success. Therefore, both propagule pressure and genetic diversity of the propagule pool may be expected to influence colonization. Using two study systems (Arabidopsis thaliana and Panicum virgatum), we explored the effects of genotypic identity, genetic diversity, propagule pressure, and habitat suitability on establishment success and/or effects of novel non-native and native colonists on native community members. To investigate the direct and interactive effects of propagule pressure and genetic diversity on colonization success of non-native A. thaliana, we manipulated propagule pressure (8, 48, 96, 248, 496, or 1000 seeds), genetic diversity (1, 4, or 8 genotypes), and microsite variation (ambient or reduced competition). Similarly, to examine how genotype identity and genetic diversity influence assimilation into a natural community and effects on co-occurring native community members, we performed a second experiment using 6 native and 6 agriculturally cultivated populations of P. virgatum, which is increasingly being planted for biofuel crops, thus enhancing the likelihood of dispersal of novel genotypes into natural communities.

Results/Conclusions Preliminary results have indicated that genotype origin influences colonization success. A. thaliana genotypes from northern latitudes are better invaders into SW Michigan; however, this latitudinal effect was evident only at high propagule numbers (p=0.03). We also found that genetic diversity does not influence the number of individuals observed in a plot (p>0.10), but does increase the probability that the plot is successfully colonized by at least one individual (p<0.01). Furthermore, in A. thaliana, higher propagule pressure and higher levels of available habitat (bareground) result in greater colonization, influencing both the number of individuals observed and the probability of at least one individual establishing (all p<0.01). Together these results suggest that there may be intraspecific variation in invasiveness and that increasing both propagule pressure and the genetic diversity of colonizing species may enhance their likelihood of success, especially in disturbed habitats. Therefore, our study further supports the importance of considering the role that individual genotypes and genetic diversity can have in driving invasions and community dynamics.