Local pre‐adaptation to disturbance and inbreeding–environment interactions affect colonisation abilities of diploid and tetraploid Centaurea stoebe

Primary colonization in invasive ranges most commonly occurs in disturbed habitats, where anthropogenic disturbance may cause physical damage in plants. The tolerance to such damage may differ between cytotypes and among populations as a result of differing population histories (adaptive differentiation between ruderal vs. natural habitats). Moreover, founder populations often experience inbreeding depression, the effects of which may increase through physical damage due to inbreeding-environment interactions. We aimed at understanding how such colonization processes differ between diploid and tetraploid Centaurea stoebe populations, with a view to understanding why only tetraploids are invasive. We conducted a clipping experiment (freq.: 0, 1 or 2 times in the growing season) on inbred vs. outbred offspring originating from 37 C. stoebe populations of varying cytotype, range and habitat type (natural vs. ruderal). Aboveground biomass was harvested at the end of the vegetation period while re-sprouting success was recorded the following spring. Clipping reduced re-sprouting success and biomass, which was significantly more pronounced in natural than in ruderal populations. Inbreeding depression was not detected under benign conditions, but became increasingly apparent in biomass when plants were clipped. The effects of clipping and inbreeding did not differ among cytotypes. Adaptive differentiation in disturbance tolerance was greater among populations than between cytotypes, which highlights the potential of pre-adaptation in ruderal populations during early colonization on anthropogenically disturbed sites. While the consequences of inbreeding increased through clipping-mediated stress, they were comparable between cytotypes, and do consequently not contribute to understanding the cytotype shift in the invasive range. This article is protected by copyright. All rights reserved.