Evidence that regional differences in ecological niche space for an invasive plant species are due to macroclimatic variation

Background/Question/Methods

Robust ecological niche models are crucial for modeling species’ geographic distributions and are increasingly used to predict invasive potential at the regional scale. Evidence suggests that the ecological niche space occupied across a geographic range, particularly for wide-ranging species, may vary for a variety of evolutionary and non-evolutionary reasons. Yet, few studies have explicitly investigated the drivers of regional niche variation. We developed Bayesian hierarchical niche models to examine the extent to which macroclimatic variation explains changes in species-environment relationships for  Microstegium vimineum, an exotic invasive plant species. We modeled the relationship between plant performance and environmental characteristics using data from four climatically distinct sites across the eastern deciduous forests of North America. 

Results/Conclusions

We found strong evidence for regional variation in species-environment relationships. Effects of light availability on M. vimineum performance varied by site, with the more temperate sites showing a positive relationship between light and aboveground biomass (mean slope = 0.029 and 0.044, sd= 0.011 and 0.016; >99% confidence in a positive relationship), and the less temperate sites showing no relationship between light and aboveground biomass (mean slope = -0.0063 and 0.0066, sd=  0.059 and 0.018). These site-level differences were negatively correlated with regional temperature and positively correlated with precipitation such that light availability influenced M. vimineum performance at only the colder, wetter sites. This study suggests that macroclimatic variation partly explains regional variation in the ecological niche space of an invasive plant. For wide-ranging species, a hierarchical modeling approach may improve niche model predictions where regional niche variation occurs.