Phenology and plant invasions: Do invaders occupy novel temporal niches?

Authors: E. M. Wolkovich, Davis, C. C. & E. E. Cleland

Background/Question/Methods

The role of phenology in assembling and assorting plant communities has a long research history in ecology. Only recently, however, have researchers began to examine if phenology may contribute to the success of non-native and invasive species in their introduced communities. In particular there are many reports of invaders which appear to occupy very early or late positions in the growing seasons of their introduced habitats. Here we use a new database of plant communities in the Northern Hemisphere to examine if--across sites--invaders appear to occupy distinct temporal niches compared to local native species.

Results/Conclusions

We find that in temperate systems non-native species tend to flower earlier than natives and are often more plastic in their phenologies. Our results are robust when considering evolutionary relatedness, and indicate that non-natives bloom much earlier than native species to which they are most closely related. Across other systems where temperature control is less dominant—e.g., tallgrass prairies and alpine meadows—results suggest some non-native species exhibit distinct phenologies from native species but may not track temperature more closely compared with native species. We discuss whether global warming—by climatically extending temperate growing seasons—may have provided novel temporal niche space at the start of spring, which the earliest and most phenologically plastic species have exploited. These findings provide support for two foundational theories of invasion biology—vacant niches and the importance of  trait plasticity—and they further suggest that phenology is an important trait to consider for predicting and understanding plant invasions.