Fig. 4From: More endemic birds occur in regions with stable climate, more plant species and high altitudinal range in ChinaHuman population density (inhabitants/km2) of the 54 cities with the highest endemic species ratio (first quarter) in 1900, 1950 and 2000. The letters above the boxplots mean significant differences among these periods, computed by the ‘glht’ function in the ‘multcomp’ R package (Hothorn et al. 2013)Back to article page