The elevational gradient in Andean bird species richness at the local scale: a foothill peak and a high-elevation plateau

摘要: A monotonic decline in species richness with increasing elevation has often been considered a general pattern, but recent evidence suggests that the dominant pattern is hump-shaped maximum occurring at some mid-elevation point. To analyse relationship between and local scale we surveyed birds from lowlands to timberline Bolivian Andes. We divided transect into 12 elevational belts of 250 m standardized each belt both individual- sample-based rarefaction estimation. The empirical data were then correlated four explanatory variables: 1) area per belt, 2) (also representing ecosystem productivity), 3) mid-domain effect (MDE) null model geometrically constrained range sizes, 4) derived empirically for South American regional pool hypothesis. Local peaked ca 1000 elevation, declined sharply 1750 m, remained roughly constant. Elevation was best single predictor, accounting 78-85% variance data. multiple regression area, MDE explained 85-90% variance. Monte Carlo simulations showed peak result an overlap two distinct avifaunas (lowland highland) correlation likely spurious. recommend complementing analyses involving predictions examination distribution midpoints. steep mid-elevations mainly due rapid loss lowland species. high-elevation plateau striking unexpected, also found previously. It cannot be present exemplifies despite several decades research gradients are still not well understood.