Abstract
Beta diversity patterns are essential for understanding how biological
communities are structured. Geographical and environmental factors, as
well as species dispersal ability, are important drivers of beta
diversity, but their relative importance may vary across spatial scales.
In this study, we evaluate whether beta diversity changes across
geographical scales and analyse how different drivers affect turnover
patterns of native seed plants in an oceanic archipelago, the Azores
(Portugal). Using a 500 x 500 m resolution grid, we selected cells that
are covered by one of the following habitats: native forest, naturalized
vegetation and seminatural pastures. We calculated species turnover at
three spatial scales: i) between islands, ii) between cells within each
island, and finally iii) between cells of each of the habitats of
interest in each island. We then calculated the contribution of
dispersal syndromes (endozoochory, epizoochory, hydrochory and
anemochory) to turnover at each of the scales. Lastly, we assessed the
relationship between geographical and climatic distances and habitat
composition with turnover. Turnover was higher at the smallest scale,
particularly in seminatural pastures, and decreased with increasing
spatial scales, a pattern potentially associated with the historical
fragmentation and current patchy distribution of native forest and
seminatural habitats in the Azores. Dispersal syndromes and habitat
composition had a negligible effect on turnover at all scales.
Geographical distance had a positive effect on turnover at all scales,
increasing with scale. The relationship between turnover and climatic
distance was only significant at the intermediate and small scales in
specific islands and habitats. Scale plays an important role at
determining the effect of the drivers of turnover, in particular
geographical and climatic distance. These results highlight the need to
carefully select the scale of analysis when studying turnover patterns,
as well as identifying the potential drivers associated with each scale.