10.5061/DRYAD.2V6WWPZJG
Allen, Warwick
0000-0002-1859-1668
University of Canterbury
Wainer, Ralph
University of Canterbury
Tylianakis, Jason
University of Canterbury
Barratt, Barbara
AgResearch (New Zealand)
Shadbolt, Marcus-Rongowhitiao
University of Canterbury
Waller, Lauren
Lincoln University
Dickie, Ian
University of Canterbury
Community-level direct and indirect impacts of an invasive plant favour
exotic over native species
Dryad
dataset
2020
apparent competition
Cytisus scoparius
indirect facilitation
Lepus europaeus
Multi-trophic interactions
plant-fungi interactions
nurse plant
Tertiary Education Commission
https://ror.org/05xhe5a74
Centre of Research Excellence funding to the Bio-Protection Research Centre
Royal Society of New Zealand
https://ror.org/04tajb587
Hutton Fund
2020-05-27T00:00:00Z
2020-05-27T00:00:00Z
en
https://doi.org/10.1111/1365-2745.13433
78367 bytes
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CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
1. Indirect interactions mediated by shared enemies or mutualists (i.e.,
apparent competition) can influence whether invasive plants harm or
benefit co-occurring species. However, studies to date have largely
examined single pairwise interactions, limiting our understanding of the
interplay among different types of interactions and whether indirect
impacts systematically favour native or exotic species. Predicting
indirect interaction strength has also proven challenging, and it remains
unclear whether the strengths of different indirect interactions are
correlated. 2. We conducted a field experiment in a grassland invaded by
Scotch broom (Cytisus scoparius) to compare the strength of its indirect
impacts, via both soil fungi or herbivores, on 21 native and exotic legume
species growing in pots buried in the ground. Direct interactions of
plants with soil fungi were controlled using nylon mesh pot windows of
differing porosity (1 or 38 µm) to prevent or allow soil fungi hyphal
growth. Arthropod herbivores were controlled through spraying pyrethrum
pesticide. To assess indirect impacts, interactions were compared between
plants adjacent to or 50 m away from an extensive Scotch broom invasion.
We measured plant performance (survival, height, and biomass), arthropod
and hare herbivory, and rhizobia nodulation. 3. Despite increasing
arthropod herbivory of both native and exotic plant species, Scotch broom
had a net positive impact on their survival and growth, through sheltering
them from abiotic stress, and indirectly via beneficial soil fungi and
release from hare browsing. Soil fungi also increased arthropod herbivory,
decreased rhizobia nodulation, and disproportionately promoted the growth
of exotic plants. Overall, exotic plants experienced stronger
interactions, which favoured them with beneficial soil fungi and rhizobia
but not hare browsing. Finally, indirect interaction strength was not
correlated among indirect interactions mediated by different interaction
partners. 4. Synthesis: We demonstrate that invaders affect their
competitors through multiple interacting indirect pathways that were
stronger than direct ‘nurse plant’ effects, emphasising the importance of
a community-level approach to studying biological invasions. Exotic
species experienced stronger positive and negative impacts than natives,
but were facilitated overall, potentially contributing to exotic dominance
in communities.
Field experiment conducted at Brooksdale Station, Canterbury, New Zealand.
See methods of published article in Journal of Ecology for details.