Fig. 1. The relationship between heart mass (g) and body mass (g) for hummingbirds: (A) raw species data (y=0.02x+0.01, r²=0.93, P<0.0001); (B) independent contrasts (y=0.957x, r²=0.79, P<0.0001). The regression using independent contrasts is forced through the origin (Garland et al., 1992). The phylogenetic hypothesis used to calculate independent contrasts contains 73 hummingbird taxa and was generated using Bayesian phylogenetic analysis (Larget and Simon, 1999; Huelsenbeck and Ronquist, 2001). Two nuclear genes (AK1, ND2) and one mitochondrial gene (Beta-fibrinogen) were sequenced and analysed using a general time-reversible (GTR) plus site-specific gamma model of evolution (J. A. McGuire and D. L. Altshuler, unpublished data).

Return to article