Fig. 5
From: Polygyny is linked to accelerated birdsong evolution but not to larger song repertoires
Detecting correlated evolution of mating systems and syllable repertoire size. We tested the correlated evolution of syllable repertoire size and polygyny using BayesTraits, with syllable repertoire size made binary based on a threshold delineating smaller vs. larger syllable repertoires. Each value of syllable repertoire was used as the threshold for 100 runs of BayesTraits per threshold. For each plot, there are eight possible transitions between the four trait pairs, shown by arrows. a–c We generated transition plots by calculating the mean rate and 95% confidence interval (in parentheses) for each of the eight transitions. a When the threshold between smaller and larger syllable repertoires is in the lowest third of observed values (24 unique thresholds ≥1 and <11 syllables, red arrows), polygyny is unstable with small syllable repertoires. b When the threshold between smaller and larger syllable repertoires is in the middle third of observed values (24 unique thresholds ≥11 and <35.1 syllables, yellow arrows), the transitions between smaller and larger syllable repertoires do not appear to be elevated in either monogamy or polygyny. c When the threshold between smaller and larger syllable repertoires is in the highest third of observed values (24 unique thresholds ≥35.1 and <2400 syllables, blue arrows), the combination of large syllable repertoires and polygyny is unstable, with the highest transition rate pointing to a decrease in repertoire size in the presence of polygyny. These results were robust to jackknife resampling across families (Supplementary Figure 30). d For each run of BayesTraits, we performed a likelihood-ratio test to assess whether the model of correlated evolution between mating system and syllable repertoire size was a significantly better fit to the data than the independent evolution model; p-values are plotted against the syllable repertoire size values defining the threshold
