Insect herbivory, plant defense, and early Cenozoic climate change

Area of Science:

• Paleobotany
• Paleoecology
• Insect-Paleoecology

Background:

• Fossil leaves from the Central Rocky Mountains offer insights into insect-plant interactions.
• Herbivore responses to climate and vegetation shifts are documented across the late Paleocene, early Eocene, and middle Eocene.
• Previous research indicates that long-lived, thick leaves are more resistant to insect herbivory.

Purpose of the Study:

• To document insect damage on fossil leaves to understand herbivore responses to changing climates and vegetation.
• To compare herbivory patterns across distinct Paleocene and Eocene climatic and vegetation regimes.
• To investigate the relationship between leaf traits (lifespan, texture) and insect resistance over geological time.

Main Methods:

• Analysis of insect damage (e.g., galling, mining) on fossil leaf assemblages.
• Classification of fossil leaf taxa based on inferred lifespan and texture.
• Correlation of herbivory patterns with paleoclimatic and paleoenvironmental data from the Central Rocky Mountains.

Main Results:

• Greater herbivory was observed on short-lived leaf taxa compared to long-lived taxa across all studied periods.
• Herbivory frequency and diversity peaked in the middle Eocene, with distinct syndromes for palatable deciduous and resistant evergreen leaves.
• Leaf galling increased, while leaf mining decreased during the middle Eocene, potentially linked to moisture availability and leaf traits.

Conclusions:

• Leaf lifespan and texture were significant factors influencing insect herbivory during the Paleocene-Eocene.
• Climate and vegetation changes drove shifts in herbivore pressure and feeding strategies.
• The study highlights the adaptive strategies of plants and herbivores in response to environmental fluctuations.