Figure 1From: Phylogenetic review of tonal sound production in whales in relation to socialityOptimizations of tonal sounds (a) and whistles (b) versus sociality using the broad concept approach [see additional file 1]. A brief glance at the black branches (indicating presence of tonal sounds/whistles and 'complex' sociality) on each side does not suggest detailed correspondence of acoustic structure with sociality. In other words whistles have a different phylogenetic distribution than does complex sociality etc, indicating that their co-evolutionary history (if any) may be more complicated than previously thought.Back to article page