Convergence without divergence in North American red-flowering Silene

Area of Science:

• Evolutionary Biology
• Plant Sciences
• Ecology

Background:

• Convergent evolution frequently results in correlated floral traits across angiosperms, driven by pollinator selection to optimize reproduction.
• While some plant groups exhibit distinct pollination syndromes, others display less predictable trait combinations, necessitating further investigation into floral trait divergence.

Purpose of the Study:

• To investigate patterns of floral trait evolution, specifically color and morphology, in the North American Silene section Physolychnis.
• To determine the extent to which pollinator-mediated selection drives diversification by examining correlated trait evolution and its relationship with phylogenetic distance and geographic overlap.

Main Methods:

• Analysis of floral trait evolution, focusing on color and morphology, within the North American Silene section Physolychnis.
• Assessment of phylogenetic history and geographic overlap to explain patterns of floral trait variation.
• Comparison of trait values between red-flowering species and white/pink-flowering species.

Main Results:

• Little clustering of North American Silene into distinct floral morphospace was observed, contrary to divergent pollination syndrome expectations.
• Phylogenetic history and geographic overlap showed minimal influence on patterns of floral diversity.
• Red-flowering species exhibited less phenotypic disparity and clustered tightly in morphospace, aligning with hummingbird pollination syndromes, yet overlapped with some white and pink species.

Conclusions:

• Convergent evolution may not always involve comparative phenotypic divergence but can arise from the sorting of standing ancestral variation.
• Floral trait evolution in North American Silene is complex, with red coloration potentially driven by hummingbird selection, but without a complete separation into distinct syndromes.