Data from: Climate vs. topography – spatial patterns of plant species diversity and endemism on a high-elevation island

1. Climate and topography are among the most fundamental drivers of plant
diversity. Here, we assess the importance of climate and topography in
explaining diversity patterns of species richness, endemic richness and
endemicity on the landscape scale of an oceanic island, and evaluate the
independent contribution of climatic and topographic variables to spatial
diversity patterns. 2. We constructed a presence/absence matrix of
perennial endemic and native vascular plant species (including subspecies)
in 890 plots on the environmentally very heterogeneous island of La Palma,
Canary Islands. Species richness, endemic richness and endemicity were
recorded, interpolated and related to climate (i.e. variables describing
temperature, precipitation, variability and climatic rarity) and
topography (i.e. topographic complexity, solar radiation, geologic age,
slope and aspect). We used multi-model inference, spatial autoregressive
models, variance partitioning and linear regression kriging as statistical
methods. 3. Species richness is best explained by both climatic and
topographic variables. Topographic variables (esp. topographic complexity
and solar radiation) explain endemic richness and climatic variables (esp.
elevation/temperature and rainfall seasonality) explain endemicity.
Spatial patterns of species richness, endemic richness and endemicity were
in parts geographically decoupled from each other. 4 .Synthesis. We
identify several topography-dependent processes ranging from evolutionary
processes (micro-refugia, in situ speciation, pre-adaptation to rupicolous
conditions, dispersal limitations) to human-induced influences (introduced
herbivores, fire, land use) that possibly shape the endemic richness
pattern of La Palma. In contrast, climate mainly drives endemicity, which
is connected to ecological speciation and specialisation to local
conditions. We highlight the importance of incorporating climatic
variability into future studies of plant species diversity and endemism.
The spatial incongruence in hotspots of species richness, endemic richness
and endemicity emphasize the need for an integrated conservation approach
acknowledging different diversity measures to protect the complete
spectrum of diversity. High-elevation islands such as La Palma are highly
suitable to study drivers of diversity and endemism, as they offer
environmental gradients of continental magnitude on the landscape scale of
a single climatic mini-continent and a large array of in situ-speciated
endemics.