Has pollination mode shaped the evolution of ficus pollen?

Area of Science:

• Evolutionary biology
• Plant reproductive morphology
• Co-evolutionary studies

Background:

• The fig-fig wasp mutualism is a 75-million-year-old obligate relationship.
• This system exhibits both passive and active pollination modes.
• Investigating pollination mode shifts offers insights into pollen evolution.

Purpose of the Study:

• To examine the relationship between pollination mode and pollen morphology in Ficus species.
• To understand how co-evolutionary processes shape pollen traits.

Main Methods:

• Pollen morphology was analyzed using scanning electron microscopy (SEM) for 25 Ficus species.
• Pollination modes were determined by the Anther/Ovule ratio.
• Phylogenetic comparative methods, including free regression and correlated evolution tests, were employed.

Main Results:

• Three distinct pollen shape and exine ornamentation types were identified.
• Actively pollinated figs predominantly featured ellipsoid pollen with rugulate, psilate, or granulate-rugulate ornamentation.
• Passively pollinated figs exhibited cylinder and sphere-shaped pollen, all with rugulate ornamentation.

Conclusions:

• Pollen morphology in Ficus is strongly associated with pollination mode.
• This finding underscores the role of pollination strategy in shaping plant reproductive traits within obligate mutualisms.