Pioneering polyploids: the impact of whole-genome duplication on biome shifting in New Zealand Coprosma (Rubiaceae) and Veronica (Plantaginaceae)

<p>The role of whole-genome duplication in facilitating shifts into novel biomes remains unknown. Focusing on two diverse woody plant groups in New Zealand, <i>Coprosma </i>(Rubiaceae) and <i>Veronica </i>(Plantaginaceae), we investigate how biome occupancy varies with ploidy level, and test the hypothesis that whole-genome duplication increases the rate of biome shifting.</p> <p>Ploidy levels and biome occupancy (forest, open, and alpine) were determined for indigenous species in both clades. The distribution of low ploidy (<i>Coprosma</i>: 2<i>x</i>, <i>Veronica</i>: 6<i>x</i>) vs high ploidy (<i>Coprosma</i>: 4–10<i>x</i>, <i>Veronica</i>: 12–18<i>x</i>) species across biomes was tested statistically. Estimation of the phylogenetic history of biome occupancy and whole-genome duplication was performed using time-calibrated phylogenies and the R package BioGeoBEARS. Trait-dependent dispersal models were implemented to determine support for an increased rate of biome shifting among high ploidy lineages.</p> <p>We find support for a greater than random portion of high ploidy species occupying multiple biomes. We also find strong support for high ploidy taxa showing a three to eight-fold increase in the rate of biome shifts. These results suggest that whole-genome duplication promotes ecological expansion into new biomes.</p>