Evolution in Helianthemum oelandicum (Cistaceae) – evidence of Holocene differentiation in morphology on the Baltic island of Öland, south-eastern Sweden

Research on Helianthemum oelandicum subsp. oelandicum, a model species for studying rapid evolutionary diversification, reveals significant morphological differentiation linked to environmental adaptations on Öland's alvar habitats. The study found that hair traits (pubescence) act as markers of adaptation to drought and periodic flooding, with genetic analysis showing up to 10 times greater differentiation in hair alleles compared to allozymes. Two plastid DNA haplotypes (H1 and H2) were identified, with var. canescens exclusively possessing H1, while var. oelandicum contains both. The restricted distribution of H1 in central Öland suggests it represents the post-glacial arrival route of the species. This research highlights the interplay between genetic variation and environmental pressures in shaping biodiversity on this UNESCO-listed agricultural landscape.

Widén, B., Soubani, E., Hedrén, M., Löfgren, O., & Widén, M. (2023). Evolution in Helianthemum oelandicum (Cistaceae) – evidence of Holocene differentiation in morphology on the Baltic island of Öland, south-eastern Sweden. Botanical Journal of the Linnean Society, 202(2), 270–293. https://doi.org/10.1093/botlinnean/boac047