Importance of self-compatibility and auto-fertility for establishment and persistence of plants in novel environments
Final Report Abstract
Due to human activity and global movements, many plant species have been introduced to nonnative regions where they experience novel abiotic and biotic conditions. Some of these alien species manage to establish reproducing naturalized populations, and some naturalized alien species subsequently become invasive. A major objective in ecology is to explain why some introduced species can establish and become invasive, while others fail to do so. In this project, we compiled a quantitative breeding-system database of 1752 species from 116 regions around the globe, and combined with data on species’ native range size and global naturalization success. Consistent with Baker’s Law, our results show that selfing ability (selfcompatibility and autofertility) is positively related to naturalization success. The effects are both direct and indirect, as native range size increases with selfing ability, which in turn has a positive effect on naturalization. We thus demonstrated that selfing ability contributes to naturalization, which strongly suggests that a lack of mates and pollinators is an important barrier to the establishment of alien plant species. To test whether alien plant naturalization is related to the ability to attract resident pollinators in non-native regions, we did a comparative study on flower visitation of 185 native, 37 naturalized alien and 224 non-naturalized alien plant species in the Botanical Garden of Bern, Switzerland. Our phylogenetically-informed analysis showed that non-naturalized alien species received fewer flower visits than both naturalized alien and native species. We thus provided the first evidence that the capacity to attract flower visitors in non-native regions is different for naturalized and nonnaturalized alien plants, which strongly suggests that naturalization is related to flower visitation. Finally, to test whether pollen limitation and low autofertility are important constraints to invasion, we performed a common garden breeding-system experiment. Using pollination treatments (pollen supplementation, open pollination, and pollinator exclusion), we assessed the degrees of pollen limitation and autofertility of 24 native and alien (both invasive and non-invasive, but naturalized) plant species (eight confamilial or congeneric triplets). The three plant groups had low degrees of pollen limitation and were almost all autofertile to some degree. The groups did not differ in their degrees of pollen limitation or autofertility. Because invasive alien species did not suffer lower pollen limitation and did not have higher autofertility than non-invasive aliens, our results suggest that pollen limitation and low autofertility may not play a major role in the spread of alien plants, once they have become naturalized. Originally, we had also planned an experiment to assess the plasticity in the breeding system of species in response to environmental change. However, as the other studies took longer than anticipated, this study could not be done. Taken together, our findings strongly suggest that reproductive characteristics contribute to alien plant naturalization. Thus, a lack of mates and pollinators may be an important barrier to establishment in new non-native regions. A breeding system that favors uniparental reproduction and the ability to attract suitable pollinators may help alien plants successfully found and maintain reproducing populations in non-native ranges. However, once the alien plant species becomes naturalized, reproductive characteristics may no longer play an important role.
Publications
- (2013) Effects of native pollinator specialization, self-compatibility and flowering duration of European plant species on their invasiveness elsewhere. Journal of Ecology 101:916-923
Chrobock T, Weiner CN, Werner M, Blüthgen N, Fischer M & van Kleunen M
(See online at https://doi.org/10.1111/1365-2745.12107) - (2013) The cobblers stick to their lasts: Pollinators prefer native over alien plant species in a multi-species experiment. Biological Invasions 15:2577-2588
Chrobock T, Winiger P, Fischer M & van Kleunen M
(See online at https://doi.org/10.1007/s10530-013-0474-3) - (2014) The more the merrier: multi-species experiments in ecology. Basic and Applied Ecology 15:1-9
van Kleunen M, Dawson W, Bossdorf O & Fischer M
(See online at https://doi.org/10.1016/j.baae.2013.10.006) - (2015) Non-naturalized alien plants receive fewer flower visits than naturalized and native plants in a Swiss botanical garden. Biological Conservation 182:109-116
Razanajatovo M, Föhr C, Fischer M, Prati D, & van Kleunen M
(See online at https://doi.org/10.1016/j.biocon.2014.11.043) - (2016) Non-invasive naturalized alien plants were not more pollen limited than invasive aliens and natives in a common garden. Functional Ecology
Razanajatovo M & van Kleunen M
(See online at https://doi.org/10.1111/1365-2435.12633)
