Insect-feeding traces in Eucalyptus leaves from the Eocene of Patagonia and their biogeographic connections to modern-day Australia
Restricted (Penn State Only)
- Author:
- Giraldo Ceron, Luis
- Graduate Program:
- Geosciences
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- May 30, 2023
- Committee Members:
- Donald Fisher, Program Head/Chair
Peter Daniel Wilf, Thesis Advisor/Co-Advisor
Mark E Patzkowsky, Committee Member
Sarah J Ivory, Committee Member - Keywords:
- biogeography
Gondwana
paleoecology
host-specialized interactions
host-tracking
biogeography
Gondwana
paleoecology
host-specialized interactions
host-tracking
leaf mining
Patagonia
Myrtaceae - Abstract:
- Understanding the assembly of insect herbivore communities through evolutionary time is crucial to the study of ecology and evolution. However, direct fossil evidence of long-term associations originating in deep time and persisting to the modern day is scant. In this study, we report insect-mediated and pathogenic damage on Eucalyptus frenguelliana leaves from the early Eocene Laguna del Hunco fossil rainforest locality in Argentinean Patagonia. To determine if insects established long-term, host-specialized associations with Eucalyptus, we compared the leaf damage observed on the fossil E. frenguelliana specimens with that seen on extant, rainforest-associated Eucalyptus species. In the fossil material, we identified a diverse suite of insect-mediated and pathogenic damage, including external foliage feeding, piercing-and-sucking marks, galls, oviposition scars, pathogenic traces, and ten distinctive mine types that, to the best of our knowledge, represent the highest richness of mines reported for a single plant host in the fossil record. Nearly identical suites of damage were observed in extant Eucalyptus herbarium specimens, suggesting that the associated insect herbivore assemblages likely tracked and radiated on multiple species of their host genus through time and space. Our representative survey of the literature revealed that although hundreds of insect herbivore species are associated with Eucalyptus hosts, most of the extant analogs for the insect herbivore damage seen in the fossils are made by still-unknown culprits, pointing to previously unrecognized biodiversity and evolutionary history of herbivorous insects on Australia’s iconic Eucalyptus. The undescribed insect culprits can be sought at the surviving locations where the herbarium vouchers were collected.