Comparative richness patterns of range sizes and life forms of Apocynaceae along forest–savanna transitions in Brazil.

This article investigates species richness patterns in the ecotones—transition zones—between Brazilian moist forests and savannas, using the Apocynaceae family (milk-weed family) as a model. The study finds that species occurring in these ecotones tend to have wider geographical ranges and broader environmental tolerances than species restricted to either forests or savannas, suggesting that ecotonal richness arises mainly from overlapping distributions of widespread species rather than from locally adapted endemics. Both lianas and other life forms (trees, shrubs, herbs) show similar richness patterns, with ecotones exhibiting the highest area-weighted species richness despite forests having the greatest absolute number of species. These results support viewing biomes and ecotones as dynamic environmental gradients rather than sharply defined ecological units, with implications for conservation strategies under climate change and land-use disturbances.