Multifunctionality of angiosperm floral bracts: a review

Area of Science:

• Botany
• Evolutionary Biology
• Plant Ecology

Background:

• Floral bracts are leaf-like structures subtending flowers, with varied forms and functions across diverse species.
• Despite extensive study, the adaptive significance of floral bracts remains incompletely understood due to a narrow focus on single selective pressures.

Purpose of the Study:

• To synthesize current knowledge on the multifaceted roles and evolutionary drivers of floral bracts.
• To highlight the need for integrative approaches considering multiple selection agents in bract evolution.

Main Methods:

• Literature review of studies on floral bract function and evolution.
• Analysis of selection pressures including pollinators, herbivores, abiotic factors, and photosynthesis.

Main Results:

• Bracts are multifunctional, influenced by pollinators (attraction, reward signaling), herbivores (defense), seed dispersal, and abiotic stress amelioration.
• Bracts contribute to photosynthesis, supporting fruit and seed development, especially when leaves senesce.
• Selection pressures on bracts vary across species and developmental stages, often interacting antagonistically or synergistically.

Conclusions:

• Floral bract evolution is driven by a complex interplay of multiple selection agents.
• Understanding bracts necessitates considering their diverse roles and the cumulative effects of various selection pressures throughout the plant life cycle.