Thrips pollination of Mesozoic gymnosperms

Area of Science:

• Paleobotany
• Entomology
• Evolutionary Biology

Background:

• Modern gymnosperms exhibit diverse pollination strategies, with conifers and Ginkgo being wind-pollinated, while gnetaleans and cycads often rely on insect pollination.
• Thrips are recognized as specialized pollinators for cycads in extant plant groups.

Purpose of the Study:

• To investigate the pollination mechanisms of Early Cretaceous gymnosperms.
• To provide direct fossil evidence of specialized insect pollination in cycads.

Main Methods:

• Analysis of four female thrips from the family Melanthripidae preserved in Early Cretaceous Spanish amber.
• Examination of pollen grains (Cycadopites) covering the thrips specimens.
• Morphological analysis of specialized setae on the thrips, interpreted as pollen-collecting structures.

Main Results:

• The fossil thrips were covered in abundant Cycadopites pollen, indicative of cycad pollen.
• Unique ring setae were observed on the thrips, functionally analogous to pollen-collecting structures in modern bees.
• These findings suggest specialized pollen collection and transportation by these ancient thrips.

Conclusions:

• The discovery provides direct fossil evidence of specialized pollen collection and likely gymnosperm pollination by thrips dating back to 110-105 million years ago.
• The specialized structures suggest parental food provisioning for larvae, indicating early subsocial behavior in thrips.
• This research sheds light on the co-evolutionary relationships between insects and gymnosperms in the Cretaceous period.