Hybrid apomicts trapped in the ecological niches of their sexual ancestors

Significance Ecological-niche differentiation in diploid sexual–polyploid asexual complexes has been observed within and among many taxa, yet the relative contributions of reproductive system and ploidy are not fully understood. Here, we assess niche characteristics of sexual diploid, apomictic (asexual) diploid, and triploid Boechera (Brassicaceae) lineages. We find strong evidence for widespread hybridization and, to a lesser degree, ploidy variation as factors that together overcome the adaptive disadvantages of apomictic (i.e., asexual) reproduction. When controlling for ploidy, we find only modest evidence for putatively asexually driven ecological-niche divergence among reproductive systems, a finding that contradicts the well-supported patterns of geographic parthenogenesis.