Organism
Appendix S7.Results ofANCOVA's across species,testing the effectcentromeric vs.telomeric location (location),the 
total number ofcoding base-pairs (Exon),the total number ofbase pairs in introns between coding exons (Intron),and 
their interactions.One transcriptper gene was chosen randomly.In all species exceptopossum,X-linked genes had 
significantly lower codon usage bias compared to autosomal genes.