Woodiness and succulence of the Canary Islands flora

Aim: Oceanic islands possess unique floras with high proportions of
endemic species. Island floras are expected to be severely affected by
changing climatic conditions as species on islands have limited
distribution ranges, small population sizes and face the constraints of
insularity to track their climatic niches. We aimed to assess how ongoing
climate change affects the range sizes of oceanic island plants,
identifying species of particular conservation concern. Location: Canary
Islands, Spain. Methods: We combined species occurrence data from
single-island endemic, archipelago endemic and non-endemic native plant
species of the Canary Islands with data on current and future climatic
conditions. Bayesian Additive Regression Trees were used to assess the
effect of climate change on species distributions; 71%
(n = 502 species) of the native Canary Island
species had models deemed good enough. To further assess how climate
change affects plant functional strategies, we collected data on woodiness
and succulence. Results: Single-island endemic species were projected to
lose a greater proportion of their climatically suitable area (x̃ = ‑0.36)
than archipelago endemics (x̃ = ‑0.28) or non-endemic native species (x̃ =
‑0.26), especially on Lanzarote and Fuerteventura, which are expected to
experience less annual precipitation in the future. Moreover, herbaceous
single-island endemics were projected to gain less and lose more
climatically suitable area than insular woody single-island endemics. In
contrast, we found that succulent single-island endemics and non-endemic
natives gain more and lose less climatically suitable area. Main
conclusions: While all native species are of conservation importance, we
emphasise single-island endemic species not characterised by functional
strategies associated with water use efficiency. Our results are
particularly critical for other oceanic island floras that are not
constituted by such a vast diversity of insular woody species as the
Canary Islands.