Hello bioconductor list, This is a clarification on MULTI SPECIES COMPARISONS filters in Ensembl Genes Mart raised by an user query. Currently (release 58) the only filters available restrict on the genes retrieved by only including or excluding homolog and paralog genes. As far as I concerned this limitation will be the same on biomaRt. Thus I don't think it's possible to filter in biomaRt by for instance 'dN', 'dS' which currently are only present in Ensembl Genes Mart as attributes. Hope this helps. Many thanks, Jorge.