Beta diversity across scales
Overall, turnover (Multisite βSIM) was lower at the
archipelago scale (large, 0.25) than within islands and within habitats
within islands (intermediate and small scale respectively, fig. 2).
Regarding the within islands scale, multisite βSIMvalues ranged from 0.7 in Flores to 0.94 in São Miguel (mean = 0.82)
(fig. 2). Moreover, 95% confidence intervals from the standardization
with 20 cells indicated that São Miguel had the highest turnover, being
significantly different from the rest of the islands except Terceira
(fig. 3A). Flores was the island with the lowest turnover, but it was
also not significantly different from any other island except São
Miguel. Turnover calculated between pairs of islands (Pairwise
βSIM) was very low and ranged from 0.06 between Faial
and São Jorge, to 0.17 between São Miguel and São Jorge (mean = 0.11)
(fig. 2), supporting the results obtained with Multisite
βSIM at large scale.
Turnover (Multisite βSIM) within habitats showed very
contrasting patterns. In native forests, the turnover value in Terceira
was twice the value as in Flores (0.81, and 0.41 respectively; fig. 2
and fig. 3B), and the 95% confidence intervals from the standardization
at 20 cells indicated that this difference was significant (fig. 3B).
For naturalized vegetation, strong variations between islands were also
found with turnover values ranging from 0.86 for São Miguel to 0.23 for
Pico. Thus, the 95% confidence intervals from the standardization at 20
cells indicated that βSIM of São Miguel was
significantly higher than βSIMof Pico and São Jorge (fig
3B). In contrast, turnover values for seminatural pastures were
consistently high across all islands being 0.90 for São Miguel and São
Jorge (fig. 3B). Interestingly, as in the case of between pairs of
islands, turnover between pairs of habitats (Pairwise
βSIM) was found to be very low within islands, as all
βSIM values were lower than 0.3 (fig. 2).