Figure 1.

Population structure in switchgrass inferred from neighbour-joining tree (a) and PCoA (b, c, d). Colour corresponds to inferred ecotype (b) or regional gene pool (a, c, d), and shape corresponds to ploidy (c, d). The Panicum amarum and P. amarulum samples are labelled individually (a–c), and their ploidy in unknown. (a) Neighbour-joining tree of all switchgrass samples, P. amarum and P. amarulum. (b) PCoA with samples from (a). Note that P. amarum and P. amarulum cluster with lowland ecotype samples. (c) PCoA with lowland ecotype samples, P. amarum and P. amarulum shows three lowland regional gene pools. (d) PCoA with upland ecotype samples shows three upland regional gene pools.