Abstract
AbstractBiotic interactions can shape species’ distributions through their impact on species’ realized niches, potentially constraining or expanding the range of conditions under which species occur. We examine whether fine‐scale plant–plant interactions scale up to shape broad‐scale species’ distributions, using Azorella selago, a widespread cushion plant that facilitates other species, and the rest of the vascular flora of sub‐Antarctic Marion Island as a model system. We compared the upper elevational distributional limit of each species when growing on vs. away from A. selago to test how the interaction with this cushion plant species affects species’ ranges. Three out of 19 vascular plant species occurred at higher altitudes in the presence of A. selago than in the absence of A. selago: Acaena magellanica (+26 m higher), Colobanthus kerguelensis (+37 m higher), and Lycopodium saururus (+19 m higher). Therefore, A. selago's fine‐scale impacts scaled up to shape the distribution of a subset of the vascular flora of Marion Island. Plant–plant interactions thus have the potential to expand species upper distributional limits by increasing the niche space that a species can occupy, although the influence of these interactions may be strongly species‐specific.
Highlights
Biotic interactions among species, which vary from competitive to facilitative, may strongly shape ecological communities (Bruno et al 2003, Armas et al 2011) and influence species–environment relationships (Lopez et al 2018)
The range of environmental conditions that a species occupies in the presence of a positive interaction may be larger than the conditions occupied by that species in the absence of that interaction
We show that 3 out of 19 vascular plant species, that is, the shrub Ac. magellanica, the cushion-forming C. kerguelensis and the clubmoss L. saururus occurred at higher altitudes in the presence of Azorella than in the absence of Azorella
Summary
Biotic interactions among species, which vary from competitive to facilitative, may strongly shape ecological communities (Bruno et al 2003, Armas et al 2011) and influence species–environment relationships (Lopez et al 2018). Empirical evidence suggests that positive interactions could potentially expand the realized niche of a species (Bruno et al 2003, He and Bertness 2014, He and Cui 2015, Filazzola et al 2018), there is still a paucity of field-quantified data to explicitly test the impact of positive inter-specific interactions on species’ occurrence patterns at broad scales across representative samples of assemblages (but see, e.g., Badano and Cavieres 2006, Badano and Marquet 2009). The prevailing view that species’ distributions are determined by the physical environment and negative inter-specific interactions alone is changing, as evidenced by the growing recognition of the importance of including positive interactions into ecological theories of community structure and organization (Bertness and Callaway 1994, Bruno et al 2003, Jones and Gilbert 2016)
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