Phylogenetic signal and traits
In addition to the functional and phylogenetic clustering with increasing elevation, there was a significant phylogenetic signal in some of the functional traits of river birds as indicated by K and K* values (p < 0.05) for body mass (K=1.2332), bill size (K=1.4098) and tarsus length (K= 1.0725) (Table 1). In other words, similarities in these traits between species reflected strong phylogenetic effects. Among these three traits with a strong phylogenetic signal, community-weighted mean values for body mass and bill length declined with elevation, but there was no such effect in tarsus length (Fig. 3). In contrast, K values for body size, tail length and breeding traits indicated more substantial variation among related taxa, though only for body size was this effect formally significant (Table 1). Judged on Moran’s I values, tarsus length and body mass had positive values while bill length had a negative autocorrelation with phylogenetic distance (Fig. S5).