SOURCES OF THE ARCTIC FLORA: ORIGINS OF ARCTIC SPECIES IN RANUNCULUS AND RELATED GENERA.

Area of Science:

• * Botanical evolution and arctic biome origins.
• * Phylogenetic and molecular analyses of plant speciation.

Background:

• * The Arctic biome is a young ecosystem with approximately 2300 vascular plant species.
• * The genus Ranunculus serves as a model for understanding arctic flora origins and evolution.

Purpose of the Study:

• * To investigate the origin and evolutionary pathways of arctic flora using the genus Ranunculus.
• * To determine the phylogenetic relationships and divergence times of arctic Ranunculus taxa.

Main Methods:

• * Molecular phylogenetic analyses using nuclear ITS and chloroplast matK-trnK DNA sequences.
• * Clock analyses were performed on 194 taxa of Ranunculus and related genera.
• * Comparative analysis of morphology, karyology, life form, and ecological traits.

Main Results:

• * Arctic Ranunculus taxa originated from seven distinct phylogenetic lineages, including genera Coptidium and Halerpestes.
• * Two clades, Ranunculus sect. Ranunculus and R. sect. Auricomus, are species-rich in the Arctic due to microtaxa and agamospermic complexes.
• * Wetland/aquatic adapted lineages show limited radiation, except for sectt. Hecatonia/Xanthobatrachium.
• * Few high-mountain lineages contributed to arctic flora; R. glacialis and R. chamissonis are exceptions.
• * Arctic and non-arctic Ranunculus taxa show no fundamental differences in morphology, karyology, life form, or ecological traits.
• * Diversification occurred at an even rate throughout the Tertiary, with no significant acceleration or impediment from Pliocene/Quaternary climate changes.

Conclusions:

• * Arctic migration involved diverse Ranunculus lineages at different times, without developing unique arctic adaptations.
• * The pattern in Ranunculus contrasts with other arctic genera like Artemisia, which exhibit specialized adaptations.
• * Range expansion of pre-adapted, wet-habitat species favored by the arctic biome's origin.
• * The study highlights recurrent patterns in arctic plant colonization and evolution.