Floral evolution by simplification in Monanthotaxis (Annonaceae) and hypotheses for pollination system shifts

Area of Science:

• Botany
• Evolutionary Biology
• Plant Systematics

Background:

• Angiosperm floral evolution frequently involves simplification through reduction, often linked to reproductive biology.
• The Annonaceae family typically features flowers with six petals and numerous stamens/carpels.
• The genus Monanthotaxis exhibits significant deviations, including flowers with only three petals and three stamens.

Purpose of the Study:

• To reconstruct the phylogeny of the genus Monanthotaxis using molecular data.
• To map the evolution of floral characters onto the established phylogeny.
• To investigate the drivers of floral diversity and reduction within Monanthotaxis.

Main Methods:

• DNA sequencing of five chloroplast and two nuclear markers for 72 Monanthotaxis species.
• Phylogenetic reconstruction to identify well-supported clades within the genus.
• Mapping of quantitative (4) and qualitative (2) floral traits onto the phylogeny.

Main Results:

• A robust phylogeny revealed distinct clades within Monanthotaxis.
• Floral evolution analysis demonstrated significant reduction in flower size and part number.
• Variation in stamen morphology, correlations between petal/stamen/carpel numbers, and non-gradual evolution were observed.

Conclusions:

• Floral reduction and diversity in Monanthotaxis are linked to pollination system switches.
• Sympatric co-occurrence of distinct clades suggests rapid diversification.
• The findings highlight the role of reproductive shifts in driving angiosperm floral evolution.