Figure 3.

Regional comparisons of the temperature overlap of geographically isolated sister species and the absence locations separating their geographical ranges. Boxes enclose the mean and its 95% confidence limits; vertical bars indicate the standard deviation. (a) Temperate sister species show significantly greater overlap in their temperature regimes with each other than they do with their intervening absence locations (suggesting speciation through niche conservatism). (b) Tropical sister species show no greater overlap with each other than they do with absence locations separating their geographical ranges (suggesting speciation through niche divergence). See text for results of statistical analyses.