The record of plant-insect interactions at the Permian La Golondrina Formation, Santa Cruz, Argentina.

CARIGLINO, BÁRBARA

Conferencia; X International Organization of Paleobotany Conference and XIV International Palynological Congress; 2016

A total of 2549 fossil plant organs from the La Golondrina Formation (Permian, Santa Cruz province, Argentina) were tallied in order to assess the diversity, frequency and composition of insect damage. The typical Glossopteris flora found at the La Golondrina Formation is characterized by several species of glossopterids, ferns and sphenophytes, and to a lesser degree, lycophytes, coniferophytes and cordaitales. Although no evidence of arthropod bodies were found at the basin yet, their past presence is recorded through various types of plant-insect interactions, involving oviposition, external feeding, piercing and sucking, galling, and a potential mine structure. Whenever possible, the interactions were identified and assigned to a previously described damage type (DT); however, some were found different enough to eventually be considered as new DTs. Results showed that at least 171 organs (all of them plant leaves) suffered from some type of insect damage. Oviposition is the predominant interaction (35%), closely followed by generalized external feeding (margin feeding + hole feeding + surface feeding + skeletonization, 34%), piercing and sucking (17%) and galling (11%). The potential presence of a mine is suggested by an interaction on a Glossopteris conspicua var patagonica Archangelsky leaf, where several loops with a central circle repeat contiguously along the margin. If its presence is confirmed, this would represent the first mention for the Paleozoic and the earliest evidence of this type of damage. Herbivory occurred almost exclusively on glossopterid foliage, as expected. Far from the glossopterids as a preferential target (92% vs. 5%), the sphenophytes (Sphenophyllum spp.) and ferns displayed low levels of herbivory, whereas the other plant groups were barely attacked. Among glossopterid leaves, it was common to find more than one type of damage type on the same organ (i.e., oviposition and margin feeding), proving the leaves were exploited for multiple purposes. Qualitatively speaking, the diversity, frequency and composition of the plant-insect interactions at the La Golondrina Formation are similar to those described for other Permian paleofloras in South Africa, Brazil, and Australia. Important patterns, such as seed-plants preferentially targeted over other plant groups and predominance of oviposition over the rest of DTs, replicate in most of these well-studied southern floras.