Macroevolutionary data suggest a role for reinforcement in pollination system shifts.

Area of Science:

• Evolutionary biology
• Speciation research
• Plant reproductive strategies

Background:

• Reproductive isolation is key to speciation, evolving via divergent selection or reinforcement.
• Pollination systems play a crucial role in plant reproductive isolation.
• The Cape flora, with specialized pollination, offers a model for studying speciation.

Purpose of the Study:

• To investigate the role of pollination system shifts in the speciation process.
• To test if pollination shifts contribute to reproductive isolation in the Cape flora.
• To differentiate between divergent selection and reinforcement as drivers of speciation.

Main Methods:

• Comparative analysis of 41 sister-species pairs from Geraniaceae, Iridaceae, and Orchidaceae.
• Utilized available pollinator, edaphic (soil type), and distribution data.
• Examined associations between pollination system shifts and edaphic shifts in sympatric and allopatric species pairs.

Main Results:

• A significant association was found between pollination system shifts and edaphic shifts for sister species with overlapping distributions (sympatric).
• No significant association was observed between pollination system shifts and edaphic shifts for allopatric sister species.
• These findings suggest reinforcement plays a role in speciation.

Conclusions:

• Pollination system shifts, coupled with edaphic shifts, are linked to reinforcement in sympatric species.
• Reinforcement, driven by ecological divergence, appears to be a significant mechanism in the speciation of the Cape flora.
• The study highlights the importance of pollination specialization in driving plant speciation.