Phylogeny and size distribution of substrate samples. Bayesian phylogeny of 22 populations of E. tynerensis. Topology is based on a majority rule consensus of 50,000 trees (5 × 106 generations sampled every 100 generations). Branch lengths were averaged across 50,000 trees. Posterior probabilities indicate node support, and only those ≥ 50% are shown. Histograms show proportions of substrate in each size class for each locality. Boundaries of the three size categories: sand and granule (0 to <2 mm), small/medium gravel (>2 to < 12 mm) and large gravel (≥ 12 mm) are indicated with dotted lines.