PLANT-INSECT INTERACTION ON A GLOSSOPTERIS LEAF FROM THE PERMIAN OF PATAGONIA: EARLIEST EVIDENCE OF LEAF MINING?

CARIGLINO, B

Congreso; 4th International Paleontological Congress; 2014

Plant-insect interactions are widely known from the fossil record, evidence which extends back in time to the Late Silurian. Six out of a total of seven extant functional feeding strategies (external foliage feeding, piercing-and-sucking, boring, galling, seed predation, and oviposition) have been recorded since the Paleozoic, leaf mining being the only interaction still not convincingly recognized. Here, a plant-insect interaction potentially assignable to a leaf mine is documented on a Glossopteris conspicua var. patagonica Archangelsky leaf from the La Golondrina Formation (Permian), Argentina. At least 3 curvilinear and contiguous traces, of constant width but varying length, are displayed on the right margin of the Glossopteris leaf. These bear central circular marks (exit holes?). More basally along the leaf?s margin, there are what appear to be aborted mines, based on their smaller size and absence of the circular marks. The interaction here described is considered a leaf mine based on the following features: (1) curved linear trace forming an almost continuous loop-pattern, (2) trace delimits a necrotic zone where leaf veins are still visible, although less defined than the robust veins on the rest of the leaf blade, implying that the cuticle is left intact, (3) presence of circular marks (exit holes?) in the loops. However, other diagnostic characteristics are missing: no frass is observed and the trace does not show an obvious increase in size as a result of the larva?s growth.