Insect herbivore and fungal communities on Agathis (Araucariaceae) from the latest Cretaceous to Recent

Abstract

Agathis (Araucariaceae) is a genus of broadleaved conifers that today inhabits lowland to upper montane rainforests of Australasia and Southeast Asia. A previous report showed that the earliest known fossils of the genus, from the early Paleogene and possibly latest Cretaceous of Patagonian Argentina, host diverse assemblages of insect and fungal associations, including distinctive leaf mines. Here, we provide complete documentation of the fossilized Agathis herbivore communities from Cretaceous to Recent, describing and comparing insect and fungal damage on Agathis across four latest Cretaceous to early Paleogene time slices in Patagonia with that on 15 extant species. Notable fossil associations include various types of external foliage feeding, leaf mines, galls, and a rust fungus. In addition, enigmatic structures, possibly armored scale insect (Diaspididae) covers or galls, occur on Agathis over a 16-million-year period in the early Paleogene. The extant Agathis species, throughout the range of the genus, are associated with a diverse array of mostly undescribed damage similar to the fossils, demonstrating the importance of Agathis as a host of diverse insect herbivores and pathogens and their little-known evolutionary history.

Middle Jurassic insect mines on gymnosperms provide missing links to early mining evolution

“…These mines, in turn, are similar to the Early Cretaceous Yixian mine of DT280 on the unaffiliated pinalean Liaoningocladus boii and czekanowskialean Solenites orientalis Sun, Zheng et Mei, and DT88 of the Paleogene araucariacean pinopsid Agathis sp. (Labandeira, 2006; Ding et al ., 2014; Labandeira et al ., 2018; Santos et al ., 2022; Xiao et al ., 2022c; Donovan et al ., 2023). This broad grouping of mine morphologies, although sufficiently different in detail to be segregated into separate DTs, nevertheless exhibits similarities, such as confinement of the mine to major, parallel, adjacent, veins, a linear and mostly sinusoidal frass trail, and termination of either in a modest chamber or at the leaf margin without a chamber.…”