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Dryad

Soil and climate contribute to maintenance of a flower color polymorphism

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Jan 21, 2025 version files 10.84 MB

Abstract

Premise of the Study: Floral pigments such as anthocyanins are well-known to influence pollinator attraction, yet they also confer tolerance to abiotic stressors such as harsh soils, extreme temperatures, low precipitation, or UV radiation. In such cases, environmental variation in abiotic stressors over space or time could lead to the maintenance of flower color variation within species. Under this scenario, flower color in natural populations should covary with environmental stressors.

Methods: Using a comparative approach, we test whether abiotic variables predict flower color in Leptosiphon parviflorus, a species with pink and white flower color morphs. We conduct in-depth field studies to assess morph frequency, soil chemistry, and climate. We then employ community scientist-powered iNaturalist observations to examine patterns across even larger spatial scales.

Key Results: Across 21 field sites we find that L. parviflorus has a higher frequency of pink morphs in sites with serpentine soil, higher average annual temperatures, and higher average climatic water deficit (a proxy for drought stress). iNaturalist observations support this finding—the probability of flowers being pink is greater in locations with serpentine-derived soil, especially when the local average UV radiation and climatic water deficit are higher.

Conclusions: Spatial variation in abiotic stressors may contribute to the maintenance of flower color variation across the geographic range of L. parviflorus and other clade members.  Future studies will examine mechanisms by which flower color affects stress tolerance and will assess whether fitness tradeoffs in contrasting habitats are associated with flower color.