Global Drivers of Non-native tree invasions
Determining the drivers of non-native plant invasions is important to adequately manage native ecosystems and limit the spread of invasive species. Tree invasions in particular have been relatively overlooked, with most studies focused on herbaceous plant species. In this project, we use a large global tree database (Global Forest Biodiversity Initiative; GFBI) combined with an invasion status database (Global Naturalized Alien Flora; GloNAF) and the Crowther lab environmental composite database to explore how the phylogenetic and functional diversity of native tree communities, human pressure and the environment influence the establishment of non-native tree species and invasion severity (number of invaders and the basal area they represent). We also assess non-native tree invasion strategy: do non-native species invade by being phylogenetically or functionally similar or dissimilar to the native community? Although not all non-native tree species will become invasive, the tens rule suggests that about 10% will become invasive. If we understand what might limit invasion of non-native species and what species are most likely to invade in different environments, this will take us one step further to preventing invasions instead of choosing which ones we can spend limited resources eradicating.
Map showing the probability of non-native tree invasions worldwide.
Microbially-mediated plant invasions
Whether mycorrhizal plant species may be limited by their mutualists in the context of invasion is currently not known. Are mycorrhizal plants only successful invaders when their resident community harbors the mutualists they rely on? Alternatively, because the dominant type of mycorrhizal fungi is arbuscular mycorrhizal (AM) and these may be very abundant in most terrestrial systems, it may be that only less common ectomycorrhizal (EM) plants are limited substantially by their mutualist compatibility. Further, anthropogenic disturbance may alter these expectations, as disturbed sites show degraded mycorrhizal communities. This could in turn limit invasion by any mycorrhizal plants. Together, this would lead to the expectation that more intact communities are more likely to be invaded by the same mycorrhizal type, while heavily disturbed sites are more likely to be invaded by non-mycorrhizal species. This work has major implications for improved conservation of native systems through a better understanding of invasion risks of both plant types and microbes themselves that have direct effects on plant success.