Phylogenetics, divergence times and diversification from three genomic partitions in monocots

Resolution of evolutionary relationships among some monocot orders remains problematic despite the application of various taxon and molecular locus sampling strategies. In this study we sequenced and analysed a fragment of the low-copy, nuclear phytochrome C (PHYC) gene and combined these data with a previous multigene data set (four plastid, one mitochondrial, two nuclear ribosomal loci) to determine if adding this marker improved resolution and support of relationships among major lineages of monocots. Our results indicate the addition of PHYC to the multigene dataset increases support along the backbone of the monocot tree, although relationships among orders of commelinids remain elusive. We also estimated divergence times in monocots by applying newly evaluated fossil calibrations to our resolved phylogenetic tree. Inclusion of early-diverging angiosperm lineages confirmed the origin of extant monocots c. 131Mya and strengthened the hypothesis of recent divergence times for some lineages, although current divergence time estimation methods may inadequately model rate heterogeneity in monocots. We note significant shifts in diversification in at least two monocot orders, Poales and Asparagales. We describe patterns of diversification in the context of radiation of other relevant plant and animal lineages.