Positive plant–plant interactions expand the upper distributional limits of some vascular plant species

Abstract

ETH Z€ urich, Z€ urich 8092 Switzerland Citation: Raath-Kr€ uger, M. J., M. A. McGeoch, C. Sch€ ob, M. Greve, and P. C. le Roux. 2019. Positive plant-plant interactions expand the upper distributional limits of some vascular plant species.Abstract. Biotic 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.

Positive cascading effects of epiphytes enhance the persistence of a habitat‐forming macroalga and the biodiversity of the associated invertebrate community under increasing stress

“…We showed that the persistence of the subtidal macroalga, H. incurva , and its ability to support invertebrate biodiversity in shallow‐water habitats rely upon light stress reduction by the epiphytic coralline alga, J. rubens . Thus, our work, together with previous studies in terrestrial and intertidal systems (Afkhami et al., 2014; He & Bertness, 2014; He & Cui, 2015; Peterson & Bell, 2012; Raath‐Krüger et al., 2019), provides evidence for the critical role of facilitation in shaping patterns of species distribution and acting as a structuring force of communities across multi‐trophic levels.…”

“…Few studies, however, have assessed how small‐scale positive interactions may scale up to regulate species distribution at broader scales (e.g. landscape or regional scales; but see Afkhami et al., 2014; Raath‐Krüger et al., 2019; Uyà et al., 2019). For example, in terrestrial systems, mutualistic endophytic fungi can expand the geographic range of their grass host by thousands of square kilometres towards drier regions (Afkhami et al., 2014).…”

Molecular evidence for hybridization in the aquatic plant Limosella on sub-Antarctic Marion Island

“…In more recent floristic surveys on the island, R . moseleyi has not been found (Raath-Krüger et al 2019, P. le Roux, personal communication 2020), and the species was left off a recent plant list for Marion Island (Chau et al 2020).…”

Effects of Soil Heterogeneity and Species on Plant Interactions

“…Many parameters can be applied to quantify plants interactions (Weigelt and Jolliffe, 2003), where relative competition intensity (RCI) is a widely used one. Previous studies found that plant interactions vary with species identity (Catorci et al, 2011;Raath-Krüger et al, 2019) and their growing stages (Yang and Rudolf, 2010;. Plant interaction at the early growing stage is crucial for plant establishment in plant populations and communities (Lortie and Turkington, 2008;Hart et al, 2018), and warrants more research.…”