Data from: Riders in the sky (islands): using a mega-phylogenetic approach to understand plant species distribution and coexistence at the altitudinal limits of angiosperm plant life

Aim: Plants occurring on high-alpine summits are generally expected to
persist due to adaptations to extreme selective forces caused by the
harshest climates where angiosperm life is known to thrive. We assessed
the relative effects of this strong environmental filter and of other
historical and stochastic factors driving plant community structure in
very high-alpine conditions. Location: European Alps, Écrins National
Park, France. Methods: Using species occurrence data collected from
floristic surveys on 15 summits (2,791–4,102 m a.s.l.) throughout the
Écrins range, along with existing molecular sequence data obtained from
GenBank, we used a mega-phylogenetic approach to evaluate the phylogenetic
structure of high-alpine plant species assemblages. We used three nested
species pools and two null models to address the importance of
species-specific and species-neutral processes for driving coexistence.
Results: Compared with the entire species pool of the study region, alpine
summits exhibited a strong signal of phylogenetic clustering. Restricting
statistical sampling to environmentally and historically defined species
pools reduced the significance of this pattern. However, we could not
reject a model that explicitly incorporates neutral colonization and local
extinction in shaping community structure for dominant plant orders.
Between summits, phylogenetic turnover was generally lower than expected.
Environmental drivers did not explain overall phylogenetic patterns, but
we found significant geographical and climatic structure in phylogenetic
diversity at finer taxonomic scales. Main conclusions: Although we found
evidence for strong phylogenetic clustering within alpine summits, we were
not able to reject models of species-neutral processes to explain patterns
of floristic diversity. Our results suggest that plant community structure
in high-alpine regions can also be shaped by neutral processes, and not
through the sole action of environmental selection as traditionally
assumed for harsh and stressful environments.