Correlation between endemism and local ecoclimatic stability documented bycomparing Andean bird distributions and remotely sensed land surface data

Relationships between large-scale patterns of biodiversity and ecoclimatic variability were examined using distributions of 789 Andean birds; recorded in 15' x 15' grid cells, and interannual differences in Normalized Differe nce Vegetation Index and Brightness Surface Temperature, calculated month b y month and resampled to 15' cells. Following the east Andean treeline from 1 degrees N to 18 degrees S; there is no evidence of a latitudinal gradien t in species richness, but a considerable local variation reflecting the ha bitat complexity in individual cells. The mean endemism (inverse range-size for all species present in a given cell) shows well marked peaks. Pairwise comparisons of 'peaks' and adjacent 'lows' of endemism provide strong evid ence for linking peaks of endemism with local ecoclimatic stability. The mo st important single factor responsible for this correlation could be orogra phic moderation of the impacts a south polar winds. Presently manifested as occasional winter freezes in the southern part of the tropical zone, these winds may have been a major determinant of vegetational changes during Ple istocene glacial periods. The correlations suggest that most endemics are r elict populations which survived periods of global climatic change in place s where these impacts were moderated. It is suggested that, by retaining re lict populations, these places play a significant role in the recruitment t o the regional species pool. The stable places were also centres of Andean cultures and have dense human populations. The current conservation strateg y of reserving areas with few people therefore needs to be supplemented wit h actions to secure sustainable landuse in certain densely populated areas.