Jan Divíšek1,2, Milan Chytrý 1, Brian Beckage3, Nicholas J. Gotelli 4, Zdeňka Lososová 1, Petr Pyšek5,6, David M. Richardson7 and Jane Molofsky3
1Department of Botany and Zoology, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
2Department of Geography, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
3Department of Plant Biology, University of Vermont, Burlington, VT 05405, USA
4Department of Biology, University of Vermont, Burlington, VT 05405, USA
5Department of Invasion Ecology, Institute of Botany, The Czech Academy of Sciences, 252 43 Průhonice, Czech Republic
6Faculty of Science, Department of Ecology, Charles University, 128 43 Praha 2, Czech Republic
7Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Matieland 7602, South Africa
There is an ongoing debate on how alien plant species become integrated into native communities and what makes them invasive. These questions were often addressed using functional trait analyses, which became an important tool in invasion ecology (Pyšek & Richardson 2007). Recently, Divíšek et al. (2018) showed that invasive plant species across all major habitat types in the Czech Republic (grasslands, ruderal and weed vegetation, rock and scree vegetation, wetlands, scrub vegetation and forests) are functionally different from both native and naturalized species, while the latter two groups are functionally very similar. Nevertheless, this comparison was done for habitat species pools, but we still do not know whether the observed differences also play a role at the fine scale of individual communities, in terms of square meters, where species actually interact. We hypothesize that alien species integrate themselves into the margin of the trait distribution if the trait values of alien species are considerably different from the mean values for the native community. If so, alien species are probably filling empty niches in the community. Conversely, if the trait values of alien species do not differ considerably from the mean value of the community, alien species are integrating themselves into the mean of the trait distribution and then they may be competing with other resident species. We addressed these hypotheses using vegetation plot data from the Czech National Phytosociological Database and the data on maximum height, specific leaf area and seed weight of each species. We applied randomization tests to test for functional trait differences between native and alien species in vegetation plots classified into the six above-mentioned habitat types. According to our very preliminary results, traits of alien species are in most plots statistically indistinguishable from the mean trait of native species in the community. However, there was always some proportion of plots where traits of alien species were further from this mean than expected at random, and these plots were considerably more frequent than those where alien species were significantly closer to the mean. This pattern seems to be consistent across all considered traits and habitat types. In future analyses, we will divide alien species according to the introduction-naturalization-invasion concept (Richardson et al. 2000) to non-invasive naturalized species and invasive species to explore trait differences between these two groups.
Divíšek J., Chytrý M., Beckage B., Gotelli N. J., Lososová Z., Pyšek P., Richardson D. M. & Molofsky J. (2018) Similarity of introduced plant species to native ones facilitates naturalization, but differences enhance invasion success. Nat. Comm. 9: 4631.
Pyšek P. & Richardson D. M. (2007) Traits associated with invasiveness in alien plants: where do we stand? In: Nentwig W. (ed.), Biological invasions. Ecological studies (Analysis and synthesis), Vol. 193, p 97–125, Springer, Berlin, Heidelberg.
Richardson D. M., Pyšek P., Rejmánek M., Barbour M. G., Panetta F. D. & West C. J. (2000) Naturalization and invasion of alien plants: concepts and definitions. Diversity Distrib. 6: 93–107.