Genome size and brain cell density in birds

Birds exhibit small, constrained genome sizes relative to many other vertebrates. This has often been attributed to the metabolic constraints of powered flight, which requires small cells for efficient gas exchange. Small cells, in turn, are achieved in part by limiting nucleus size, and thus DNA content. However, metabolism is not the only organismal trait that correlates with genome size in birds; relationships have also been reported with body size (positive) and relative brain size (inverse). In this study, a recent dataset on cell numbers in the brains of birds was combined with available data on genome sizes to demonstrate a relationship between genome size and the density of cells per gram of brain tissue. This suggests that small genomes are relevant not only in the evolution of avian flight, but may also be associated with the extraordinary behavioural complexity shown by birds.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author