Color polymorphism in Anemone coronaria: Correlations with soil, climate, and flowering phenology.

Premise: Flower color polymorphism (FCP) is thought to be driven by multiple selection agents. Although widely associated with visual attraction of multiple pollinators, FCP is also often correlated with abiotic factors. We explored the links between abiotic conditions, flowering phenology, and FCP in the winter-flowering geophyte Anemone coronaria L., which forms color-polymorphic or red-only populations.

Methods: We mapped the geographical distribution of color diversity in A. coronaria in Israel using citizen-science data. We recorded the phenology and density of red and non-red flowers during two flowering seasons in 18 plots along a rainfall gradient. We related the spatiotemporal data to soil and climate measures.

Results: Color-polymorphic populations are restricted to Mediterranean sites (>450 mm annual rainfall, >60% soil saturation), whereas red populations are found in Mediterranean and in semiarid sites, and in soils with high (>15%) soil calcium carbonate (CaCO) content. Greater soil electrical conductance (salts and water) was predictive of earlier first flowers. Flowering started earlier in Mediterranean than in semiarid plots, and earlier in non-red than in red flowers. Temperature and soil potassium concentrations (for non-red flowers) or sand content (for red flowers) were predictive of the timing of peak flowering.

Conclusions: The spatiotemporal patterns of FCP in A. coronaria may reflect adaptation of red flowers to stressful semiarid abiotic conditions and to pollinator preferences. Abiotic conditions that delay flowering may benefit red anemones by enhancing their probability of encountering glaphyrid beetles, their specialized pollinators.