Linking genome size variation to phenotypic selection on target traits.

Area of Science:

• Evolutionary Biology
• Plant Genomics
• Ecology

Background:

• Genome size (GS) exhibits significant variation across and within angiosperm species.
• This variation is often linked to phenotypic traits, suggesting indirect selection on GS evolution.
• Microevolutionary processes driving GS changes within species are less understood compared to broad phylogenetic scales.

Purpose of the Study:

• To investigate how selective pressures shape genome size (GS) evolution at the microevolutionary level within recently diverged lineages.
• To link microevolutionary patterns of GS variation to macroevolutionary processes by studying two Dianthus rupicola lineages.
• To identify ecological factors and selective pressures driving GS and associated phenotypic trait evolution.

Main Methods:

• Flow cytometry was used to estimate genome size (GS) in Dianthus rupicola populations.
• Leaf and floral traits were measured, and allometric relationships with GS were analyzed.
• Environmental factors and plant reproductive success were quantified to identify selective pressures.

Main Results:

• Substantial GS variation was observed within and between the two Dianthus rupicola lineages.
• GS showed a strong allometric relationship with leaf traits (stomata area, epidermal cell dimension) and floral traits (style length).
• Leaf traits indicated local adaptation to edaphic environments, while style length variation was linked to divergent biotic pressures, including a seed predator.

Conclusions:

• Ecological factors significantly influence traits that covary with genome size (GS).
• This study provides a framework for understanding the interplay between microevolutionary and macroevolutionary processes in GS evolution.
• Selection on phenotypic traits, driven by ecological interactions, can indirectly shape genome size evolution within and among species.