Shifts in floral traits related to the Jimsonweed (Datura stramonium) worldwide invasion.

Transitions from an outcrossing to a selfing mating system may represent an advantage during plant invasions, enabling the production of offspring even in cases of unstable pollinator environments or mate limitation. In this study, we explore the shifts in floral traits associated to the mating system across the distribution range of Datura stramonium, a cosmopolitan invasive weed native from Mexico and surrounding regions. We recorded seven floral traits of 1,945 flowers from 77 populations (12 native and 65 non-native) throughout the world distribution range to analyze their differentiation between the native and non-native ranges. Non-native populations of D. stramonium presented lower herkogamy than native populations, in agreement with the hypothesis of reproductive assurance under non-reliable pollinator environments. Corollas were unexpectedly larger in the non-native than in the native range, which could be attributed to high nutrient and water inputs in agroecosystems, the most common habitat of non-native populations. The phenotypic variation within populations was lower in the non-native range, which is congruent with the occurrence of founder events during the introduction or subsequent drift. Floral color showed a significant differentiation between native and non-native populations, probably due to founder events. The lack of association between floral color and herkogamy indicates that their differentiation between ranges is due to different and independent processes. Future studies involving experimental populations grown under different environmental conditions at each range, and population genetic and phylogeographic studies, will help to identify the selective factors and evolutionary processes determining the phenotypic patterns depicted across native and non-native populations of D. stramonium.