Dispersal distance and recruitment survival comparison of introduced and native species on a broad scale under natural conditions

Background/Question/Methods

We aimed to test the widely held idea that introduced species have dispersal and recruitment advantages over native species. We compiled data on mean and maximum dispersal distance for 56 introduced and 367 native species, and data on survival through germination (seed to seedling survival), early seedling survival (survival through one week from seedling emergence) and survival to adulthood (seedling emergence to reproductive maturity) for 285 native and 63 introduced species.

Results/Conclusions

Contrary to expectations, there was no significant difference in mean or maximum dispersal distance between native and introduced species. These results remained non-significant once we accounted for the effects of plant height, seed mass, dispersal syndrome, site to site variation and their interactions. Further, we found that introduced and native species do not significantly differ in survival to germination, early seedling survival or survival to adulthood. These comparisons remained non-significant after accounting for longevity, seed mass and including a term for site to site variation. Thus, our data do not support the idea that introduced species have higher dispersal distance or higher recruitment success than do native species. Perhaps any advantages of introduced species (such as enemy release) are counterbalanced by the fact that native species have had longer to adapt to their environment.