Effects of experimental host-plant switching on the life cycle of a fern spore-feeding micromoth of the genus Stathmopoda

Abstract

Fern-feeding insects have not received much attention because ferns have been considered herbivore-resistant plants. However, ferns are attacked by herbivorous insects, including specialized spore feeders. For a better understanding of host specialization, we investigated the effect of experimentally transferred larvae of a spore-feeding moth, Stathmopoda sp. (Lepidoptera: Stathmopodidae), from its original fern host Amauropelta linkiana (C. Presl) Pic. Serm., to three closely related species [Amauropelta rudis (Kunze) Pic. Serm, Amauropelta oligocarpa (Humb. & Bonpl. ex Willd.) Pic. Serm., and Amauropelta resinifera (Desv.) Pic. Serm.], and one alien fern species, Macrothelypteris torresiana (Gaudich.) Ching (all Thelypteridaceae). After experimental host-plant transfer, we measured spore consumption of the larvae, and the survival and duration of each developmental stage. Once larvae were transferred to alternative hosts, they were still able to complete their life cycle, but consumed more spores, required more time to reach the adult stage, and had lower survival rates than on their original host, or even skipped the fifth instar on alternative hosts. Thus, our results suggested a strong adaptation of this moth species on its original host plant. We discuss some traits of experimental hosts, as the spores may contain fewer nutrients, or higher concentrations of toxic agents for larval development, thus restricting successful host-plant switching. Further studies to measure the frequency and successful colonization of alternative hosts in nature are needed, by assessing variation in the chemical composition of spores between original and alternative hosts.