Morphological traits of the flora of the Canary Islands

Aim: Functional traits can help elucidate biogeographical and ecological
processes driving assemblage structure. We analysed the functional
diversity of plant species of different evolutionary origins across an
island archipelago, along environmental gradients and across geological
age, to assess functional aspects of island biogeographic theory.
Location: Canary Islands, Spain. Major taxa studied: Spermatophytes. Time
period: Present-day. Methods: We collected data for four traits (plant
height, leaf length, flower length and fruit length) associated with
resource acquisition, competitive ability, reproduction and dispersal
ability of 893 endemic, non-endemic native and alien plant species
(~43 % of the Canary Island flora) from the literature. Linking
these traits to species’ occurrences and composition across a
500 m x 500 m grid, we calculated functional diversity
for endemic, non-endemic native and alien assemblages using
multi-dimensional functional hypervolumes and related the resulting
patterns to climatic (humidity) and island biogeographic (geographical
isolation, topographic complexity, geological age) gradients. Results:
Trait space of endemic and non-endemic native species overlapped
considerably, while alien species added novel trait combinations,
expanding the overall functional space of the Canary Islands. We found
that functional diversity of endemic plant assemblages was highest in
geographically isolated and humid grid cells. Functional diversity of
non-endemic native assemblages was highest in less isolated and humid grid
cells. In contrast, functional diversity of alien assemblages was highest
in arid ecosystems. Topographic complexity and geological age only had a
subordinate effect on functional diversity across floristic groups. Main
conclusions: We found that endemic and non-endemic native island species
possess similar traits, while alien species tend to expand functional
space in ecosystems where they have been introduced. The spatial
distribution of the floristic groups’ functional diversity is very
distinct across environmental gradients, indicating that species
assemblages of different evolutionary origins functionally thrive in
dissimilar habitats.