Key processes for Cheirolophus (Asteraceae) diversification on oceanic islands inferred from AFLP data

Area of Science:

• Botany and Evolutionary Biology
• Island Biogeography
• Molecular Ecology

Background:

• The genus Cheirolophus (Asteraceae) exhibits rapid diversification in Macaronesia, with 20 species, 9 threatened.
• Previous studies indicated diversification began less than 2 million years ago, but low molecular marker variability limited phylogenetic resolution.

Purpose of the Study:

• To evaluate species boundaries within Macaronesian Cheirolophus.
• To infer evolutionary relationships using highly polymorphic markers.
• To investigate genetic diversity patterns and their role in the radiation process.

Main Methods:

• Analysis of 172 individuals from all Macaronesian Cheirolophus species.
• Utilized 249 Amplified Fragment Length Polymorphism (AFLP) loci for high polymorphic resolution.
• Examined species boundaries, evolutionary relationships, and genetic diversity.

Main Results:

• Geographic isolation significantly influenced the radiation, driven by limited gene flow and successful long-distance colonization.
• Evidence of introgression and incipient ecological adaptation was detected.
• Current IUCN Red List threat categories may not align with the evolutionary significance of species.

Conclusions:

• Geographic isolation, limited gene flow, and long-distance dispersal are key drivers of Cheirolophus radiation.
• Introgression and ecological adaptation may have further fueled diversification.
• Conservation assessments should incorporate evolutionary relevance alongside threat status.