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We report the results of systematic vascular plant and bird surveys in
Seasonally Dry Tropical Forest (SDTF) across leeward and windward
elevation gradients (31– 884 masl) in the Sierra Martín García (SMG),
Dominican Republic. We expected to see gradual, systematic changes in
plant distributions with elevation owing to the strong effect of
topoclimate. In contrast, we predicted bird community composition to be
related only weakly to elevation, because we expected bird distributions
to be more strongly related to vegetation structure than composition.
Based on 48 vegetation transects, we identified seven groups that differed
in their species composition, which was correlated with elevation and
precipitation. The most distinctive vegetation community occurs in dry,
warm, low elevations on the leeward slope, featuring large numbers of
non-woody indicator species (those species found frequently within one
group but not in other groups) even though most of its trees and shrubs
represent species that are widespread. Low rainfall and shale bedrock
(rather than limestone) may be the primary drivers of distinctiveness in
the low elevation leeward plots. On the leeward slope, where we also
surveyed the birds, the vegetation community changes gradually with
elevation at mid- to high elevations. The most distinctive bird community
also was associated with the low-elevation forest on shale bedrock and was
dominated by widespread species. At higher elevations, but still within
leeward SDTF, the bird communities had a stronger component of species
endemic either to Hispaniola or to Caribbean islands, and species turnover
did not correspond to the elevation gradient.
213 views reported since publication in 2019.