Late Lunch Talks: Revisiting the taxon-level effect in brain evolution: insights from a large data across vertebrates by Masahito Tsuboi
Late Lunch Talks on brain evolution in vertebrates by Masahito Tsuboi from CEES.
Revisiting the taxon-level effect in brain evolution: insights from a large data across vertebrates
The close association between brain size and body size in vertebrates is a well-documented example of evolutionary constraints at higher taxonomic levels. At the same time, studies of domesticated and experimental animals provide evidence that brain size can undergo selection independent of body size within short evolutionary time-scales. Theory of multivariate quantitative genetics suggests that the structure of genetic variance-covariance may explain the mismatch in brain-body allometric scaling across different time scales, which is known for the taxon-level effect (TLE). Here, I use data on over 20,000 observations of brain and body size across 4,589 species to show a stark contrast between mammalian/avian lineages and other vertebrate taxa in the TLE. In highly encephalized mammals and birds, evolutionary allometric slope at higher taxonomic levels (evolutionary allometry) decays as the scale of comparison shifts from class to within-species, supporting the TLE. On the contrary, in less encephalized amphibians, boney fishes, cartilaginous fishes and reptiles, brain-body allometric slopes are essentially invariant at all temporal levels. This pattern support the idea that the genetic de-coupling of brain size and body size represents a key evolutionary change that facilitated the exceptional encephalization of mammals and birds. In my late lunch talk, I will show figures and results to discuss my finding about the TLE. I will then introduce my ideas and results that aims to challenge the interface between micro- and macroevolution.
The attached photo is actually a figure. It is a figure drawn by Harry Jerison in the ’70 when he studied brain-body relationship across vertebrates (and fossil animals). My study essentially starts as an update of this figure, and extends further to the detail of allometric constraints.