Fig. 2: Major shifts in the relative size and evolutionary rate of the mushroom body in Heliconiini butterflies.

A, B Phylogenetic shifts in the scaling relationship between the volume of the mushroom body (MB) and the rest of the central brain (rCBR) across 41 Heliconiini taxa (posterior probability > 0.5). Relative to outgroup Heliconiini (blue), MB volumes are twice as large in Eueides (purple) and Dryadula phaetusa (green) and four times as large in Heliconius (red). Solid points = species means; faded points = individuals. Estimated ancestral states for each group shown by density maps. C, D The branch leading to Heliconius shows a marked increase in the evolutionary rate of MB volume, with a slightly less elevated rate along the branch leading to Heliconius + Eueides. E–H Shifts in MB size and evolutionary rate are not reflected in either the antennal lobe or the medulla. The butterfly image is from Wikimedia commons, released under CC-BY-SA 4.0. Source data files: A Heliconiini.trees and Heliconiini_neuro_species.csv; B Heliconiini_neuro_individuals.csv and Heliconiini_neuro_species.csv; C Heliconiini.trees and Heliconiini_neuro_species.csv; D–H Heliconiini_neuro_species.csv.