Editor: Janne Soininen
Consequences of the introduction of exotic and translocated species and future extirpations on the functional diversity of freshwater fish assemblages
Article first published online: 27 MAY 2013
© 2013 John Wiley & Sons Ltd
Global Ecology and Biogeography
Volume 22, Issue 9, pages 1071–1082, September 2013
How to Cite
Matsuzaki, S.-i. S., Sasaki, T. and Akasaka, M. (2013), Consequences of the introduction of exotic and translocated species and future extirpations on the functional diversity of freshwater fish assemblages. Global Ecology and Biogeography, 22: 1071–1082. doi: 10.1111/geb.12067
- Issue published online: 12 AUG 2013
- Article first published online: 27 MAY 2013
- Environment Research and Technology Development Fund (S9) of the Ministry of the Environment, Japan
- Tohoku University's Global COE program (no. J03) from the Ministry of Education, Culture, Sports, Science and Technology of Japan
- Ecosystem functioning;
- fish assemblages;
- functional traits;
- limiting similarity;
- species introductions;
- species loss;
- trait divergence
To explore the effects of the introduction of exotic and translocated species and possible future extirpation of native species on the functional diversity (FD) of freshwater fish assemblages.
We examined spatio-temporal changes in species richness, FD, functional richness (the number of trait-based functional groups), and the functional group composition between historical and current fish assemblages for 27 eco-regions, and compared the relative effects of the introduction of exotic and translocated species on FD. We also used a null model approach to determine the assembly patterns and the extent of functional redundancy. Finally, we determined the effect of the loss of endangered species on FD by comparing the observed losses with simulated random loss.
Through the introductions of non-native species, the species richness, FD and functional richness of the fish assemblages increased 2.4-, 1.6- and 2.1-fold, respectively. The functional group composition also changed largely through the additions of new functional groups. Exotic species had a significantly greater effect size than translocated species, but there were no differences in the overall net effects of exotic and translocated species. Null modelling approaches showed that the observed FD was higher than expected by chance (i.e. trait divergent) in both historical and current assemblages. There was also low functional redundancy. In our simulation, FD decreased in proportion to the loss of species, independent of whether the species were endangered.
We demonstrated that both exotic and translocated species may change FD and functional group composition, which might have dramatic consequences for ecosystem processes. We suggest that the future extirpation of even a few native species can cause a substantial loss of FD. Our findings emphasize the need to improve conservation strategies based on species richness and conservation status, and to incorporate translocated species into targets of the management of non-native species.