Endophytic insect oviposition traces in deep time

Abstract

Interactions between the two most abundant groups of organisms on Earth, insects and plants, are especially relevant in evolutionary studies. We review different aspects related to endophytic eggs laid by insects in plants for more than 300 Myrs, from the Carboniferous to the Miocene. This work provides a meta-analysis of endophytic insect oviposition in the fossil record, based on the plant group used as host, the number of oviposition traces on a single leaf, their trace pattern, and the morphometry of the individual egg traces. Our results show that Pinophyta and “pteridosperms” are the host-plant groups most frequently reported up to the Early Cretaceous, and Magnoliophyta (=Angiospermae) from the Cretaceous. The highest number of bibliographic records are from the Permian, while the Mesozoic Era shows the highest richness of trace patterns. No relation was detected between the trace pattern and the host-plant group used for oviposition. Our observations support the proposal that the trace pattern would be insect-specific and does not depend on the host-plant group on which the egg-laying occurs. From the Carboniferous to the Miocene, a gradual increase in the frequency of “Curved” type patterns and a decrease in “Straight” type patterns is observed. Two reduction events of the length of the traces are established, during the Permian, which could be explained by environmental causes, and during the Cretaceous by the emergence and selective predation by birds.