Herbivory in ancient aquatic ecosystems: the case of Miocene Salvinia species from the Northwestern of Argentina

Abstract

Herbivory traces found on Salvinia graui Herbst and Anzótegui, 1987 and Salvinia cf. minima Baker, 1886 were analysed herein. These ichnofossils were collected from Quebrada de Alfredo outcrop in sediments corresponding to the Palo Pintado Formation (Late Miocene, at the Northwest of Argentina). Among the traces identified, one of them became interesting: a new type of leaf-mining that never have been recorded in these fossil plants. The leaf-mining are linear and branched like fingers, pointing to a particular behaviour from the insect producer. Likewise, other damage types corresponding to marginal, non-marginal and window excisions and one gall were found. The fossil traces were assigned to five ichnospecies, of which three are novelties. Moreover, these damages were compared with modern specimens collected at the Northeast of Argentina and possible producers were inferred. This study demonstrates that interactions between Salvinia and their associated insects were already established 8 Ma ago, without suffering significant changes. Our results also constitute the second evidence of plant-insect interactions of aquatic ferns during the Neogene in both South America and worldwide as well as enrich the understanding of the ecological dynamics and diversity of insect feeding strategies in aquatic environments at different times in the past.