Middle Devonian liverwort herbivory and antiherbivore defence

Area of Science:

• Paleobotany
• Paleoecology
• Evolution of Terrestrial Ecosystems

Background:

• Early terrestrial ecosystems lacked extensive fossil records of plant-arthropod interactions.
• Understanding herbivory's role is crucial for reconstructing early land plant evolution and ecosystem dynamics.

Purpose of the Study:

• To investigate the extent and nature of herbivory in late Middle Devonian terrestrial ecosystems.
• To identify the earliest evidence of external foliage-feeding and galling in the terrestrial fossil record.

Main Methods:

• Examination of compression-impression specimens of the liverwort Metzgeriothallus sharonae from the Catskill Delta deposit.
• Utilizing liquid nitrocellulose film lifts and cedarwood oil microscopy to reveal plant-arthropod damage types (DTs).

Main Results:

• Documented an extensive repertoire of arthropodan-mediated herbivory on M. sharonae, including three functional feeding groups and nine DTs.
• Identified the earliest occurrence of external foliage-feeding and galling in the terrestrial fossil record.
• Evidence suggests thallus oil bodies in M. sharonae may have provided chemical defense against herbivores.

Conclusions:

• Herbivory was a significant ecological interaction in early terrestrial ecosystems, potentially more widespread than previously assumed.
• Devonian arthropod herbivores were likely smaller than their later Paleozoic counterparts, based on plant damage patterns and fossil evidence.
• The findings provide critical insights into the co-evolution of plants and arthropods during the Devonian period.