Flower colour polymorphism in the Mediterranean Basin: occurrence, maintenance and implications for speciation

Area of Science:

• Evolutionary biology
• Plant genetics
• Ecology

Background:

• Flower colour polymorphism (FCP) is the presence of multiple flower colour variants within a single population.
• Research has extensively studied FCP maintenance and evolutionary impacts, but spatial variation in morph frequencies across populations is a newer focus.
• Understanding geographic variation in FCP is crucial for insights into speciation processes.

Purpose of the Study:

• To summarize the biochemical and genetic underpinnings of FCP.
• To review factors maintaining FCP, including pollinator and non-pollinator selection, genetic drift, and gene flow.
• To examine the incidence and geographic patterns of FCP in the Mediterranean Basin and its role in speciation.

Main Methods:

• Literature review of FCP biochemical and genetic bases.
• Analysis of factors contributing to FCP maintenance.
• Review of FCP incidence and geographic variation in the Mediterranean Basin.

Main Results:

• Nearly 88% of Mediterranean FCP species exhibit anthocyanin-based polymorphisms.
• Multiple evolutionary mechanisms, including pollinator/non-pollinator selection, genetic drift, gene flow, selfing, and clonal reproduction, contribute to FCP maintenance.
• Mediterranean polymorphic species predominantly feature monomorphic populations, creating clinal or mosaic geographic patterns of FCP variation.

Conclusions:

• Anthocyanin-based polymorphisms are common in Mediterranean FCP.
• A combination of evolutionary processes, including reproductive strategies like selfing and clonal reproduction, maintains FCP.
• Geographic patterns of FCP in the Mediterranean are diverse, ranging from clinal to mosaic, reflecting varied evolutionary pressures.