3D pollination biology using micro-computed tomography and geometric morphometrics in Theobroma cacao

Area of Science:

• Botany and Plant Science
• Evolutionary Biology
• Imaging Technology

Background:

• Floral morphology in herkogamous species like Theobroma cacao presents physical barriers (bottlenecks) that restrict pollinator access to reproductive organs.
• Understanding these pollination bottlenecks is crucial for predicting effective pollinators and improving crop yield in cacao.

Purpose of the Study:

• To apply micro-computed tomography (micro-CT) and 3D geometric morphometrics (GMM) for quantifying pollinator functional size limits in Theobroma cacao.
• To identify the primary floral bottleneck restricting pollinator access and to assess potential pollinators based on their morphological fit.

Main Methods:

• Generated micro-CT datasets of Theobroma cacao flowers and potential pollinator specimens.
• Utilized 3D Slicer for landmark placement and geomorph R for GMM analysis to compare floral dimensions.
• Identified the petal side door as the main bottleneck and compared its dimensions with pollinator morphology.

Main Results:

• Quantified pollinator functional size limits using micro-CT and GMM analysis of floral dimensions.
• Identified the petal side door as the critical bottleneck for pollinator entry.
• Categorized potential pollinators into three likelihood levels based on morphological fit through the bottleneck.
• Discovered previously unclear details about floral reward microstructures.

Conclusions:

• Micro-CT and GMM offer a novel approach to studying 3D pollination biology and predicting unknown pollinators for cacao.
• Integrating floral geometry and reward characteristics enhances plant-pollinator trait matching models for cacao and other species.