Sharply increased insect herbivory during the Paleocene-Eocene Thermal Maximum

Area of Science:

• Paleoclimatology
• Paleobotany
• Insect Paleobiology

Background:

• The Paleocene-Eocene Thermal Maximum (PETM) was a period of rapid global warming and increased atmospheric carbon dioxide (CO2).
• Understanding past climate events provides analogues for current anthropogenic climate change.
• Insect herbivory is a key ecological interaction influenced by environmental factors.

Purpose of the Study:

• To investigate the impact of PETM warming and elevated pCO2 on insect herbivory.
• To document changes in insect damage on fossil plant leaves across the PETM.
• To assess the long-term implications of increased pCO2 and warming on plant-insect dynamics.

Main Methods:

• Analysis of 5,062 fossil angiosperm leaves from the Bighorn Basin, Wyoming.
• Fossil collection from sites spanning the pre-PETM, PETM, and post-PETM intervals (59-55.2 Ma).
• Quantification of insect damage, including diversity and specialized damage, on fossil leaves.

Main Results:

• Insect damage on leaves, including specialized herbivory, showed a strong correlation with rising and falling temperatures during the PETM.
• Both the amount and diversity of insect damage peaked during the PETM.
• All plant species from the PETM experienced extensive damage from specialized herbivores.

Conclusions:

• Elevated temperatures and pCO2 during the PETM significantly amplified insect herbivory.
• Fossil evidence suggests a direct link between past climate change and increased insect-plant interactions.
• Anthropogenic climate change may lead to a long-term increase in insect herbivory globally.