Why does pollen morphology vary? Evolutionary dynamics and morphospace occupation in the largest angiosperm order...

Area of Science:

• Botany
• Evolutionary Biology
• Biodiversity Research

Background:

• Morphological diversity (disparity) is crucial for biodiversity.
• Pollen grain morphologies are diverse, yet controls on pollen disparity and morphospace occupation are understudied.
• Few studies integrate pollen disparity and morphospace occupation within a phylogenetic framework.

Purpose of the Study:

• Analyze morphospace occupation, disparity, and morphological evolution rates in Asterales pollen.
• Investigate the phylogenetic structure of pollen morphology within Asterales.
• Examine potential drivers of pollen morphological evolution, such as whole-genome duplication.

Main Methods:

• Phylogenetic analysis of 113 Asterales taxa.
• Pollen morphology described using 28 discrete characters.
• Assessment of morphospace occupation, disparity, and evolutionary rates.

Main Results:

• Asterales pollen morphospace is phylogenetically structured, with morphological evolution occurring in bursts.
• No significant differences in pollen disparity were found among Asterales groups, irrespective of species richness or range.
• Evidence for whole-genome duplication as a driver of pollen morphological evolution in Asterales is mixed.

Conclusions:

• Evolutionary history significantly structures pollen morphospace in Asterales.
• Biodiversity parameters can be decoupled, highlighting the need to study disparity independently.
• Pollen disparity is a key botanical metric that warrants focused research.