Niche shifts and localized competitive dynamics influence the persistence and distribution of polyploids in the genus Achillea (Asteraceae).

Background and aims: Competition with sympatric diploid progenitor(s) hinders the persistence of polyploids. The hypothesis that polyploids escape from competition through niche shifts has been widely tested; however, niche escape is unlikely to completely avoid competition. Given species growing in less favourable environments probably have weaker competitive abilities, we hypothesize that polyploid populations tend to persist in areas where their progenitors have relatively low habitat suitability.

Methods: This study investigated two sibling allopolyploid species, Achillea alpina and A. wilsoniana of the daisy family, which originated independently from the same two parental species. We explored the patterns of niche shifts between the polyploids and their progenitors by using several ecoinformatics analyses in environmental and geographical spaces, and performed ecological niche modelling to estimate the historical distribution of these species as well as the potential regions for persistence of allopolyploids.

Key results: The niche shift patterns of the two polyploids were not completely consistent: A. alpina showed niche expansion, while A. wilsoniana exhibited a trend towards niche novelty. Their potential suitable areas were both more likely to overlap with regions where the habitat suitability values of their parental species became low.

Conclusions: The present results support our hypothesis that populations of polyploids tend to persist in areas that are less suitable for their diploid progenitors. Meanwhile, niche shifts may promote the success of polyploids. These findings contribute to our understanding of the ecological processes involved in the maintenance and persistence of polyploids.