A global review and network analysis of phytophagous insect interactions with ferns and lycophytes

Luis Javier Fuentes-Jacques,Cecilia Díaz-Castelazo,Paul Hanson-Snortum,Klaus Mehltreter,Vicente Hernández-Ortiz

doi:10.1007/s11258-021-01187-5

Luis Javier Fuentes-Jacques, Cecilia Díaz-Castelazo + Show 3 more

Open Access

https://doi.org/10.1007/s11258-021-01187-5

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Abstract

Ferns and lycophytes are the second and third largest lineages of vascular plants, yet our understanding of their interactions with phytophagous insects is very limited. In this study, we reviewed herbivorous insects, their feeding habits and host preferences on these two plant groups, searched for any evidence of coevolution, and discussed possible biases of our current knowledge on fern–insect interactions. We analyzed 2318 records of fern–insect interactions from 122 literature sources, based on the feeding habit of insects, fern taxa, and geographic location. We report interactions comprising 809 insect species (mainly Hemiptera, Lepidoptera, and Coleoptera) and 382 fern species (mainly Dennstaedtiaceae, Dryopteridaceae, and Pteridaceae). Leaf-chewers comprised over 50% of the species, followed by sap-sucking insects (29.1%) and spore feeders (6.5%). The overall interaction analyses revealed that the entire network was not significantly nested and had relatively low levels of specialization (H2′ = 0.24). The interaction networks of Coleoptera were the most specialized at family (H2′ = 0.40) and genus level (H2′ = 0.65), whereas six out of 10 most specialized insect families were Lepidoptera (d′ ≥ 0.44). At the genus level, all networks had a plant-biased asymmetry. Although insect specialists were common, few cases of coevolutionary radiation have been documented. We discuss the possible biases of our dataset, which also highlight gaps to fill in future research and suggest that many more fern-feeding insects remain to be discovered, especially sap-sucking, gall-forming, and spore-feeding insects on modern fern groups.

Highlights

Herbivory is the process through which plant-feeding animals assimilate carbon and other nutrients into their bodies and food chains, and approximately 18% of all plant biomass is lost to herbivory in any given terrestrial environment (Cyr and Face 1993)
We know of 423,569 phytophagous insect species (Wiens et al 2015) feeding on 308,374 vascular plant species (Christenhusz & Byng, 2016) of which 3.86% are ferns (PPG I, 2016)
Based only on our current knowledge, we would expect that each vascular plant is attacked by an average of 1.37 insect species and that at least 16,000 insect species may feed on ferns alone

Summary

Introduction

Herbivory is the process through which plant-feeding animals assimilate carbon and other nutrients into their bodies and food chains, and approximately 18% of all plant biomass is lost to herbivory in any given terrestrial environment (Cyr and Face 1993). Evidence of insect herbivory from plant fossils dates back to the late Silurian (Labandeira 2007), but most of the insect diversity developed together with a specialization of their mouthparts and in coevolution with their host plant species (Nel et al 2018). Insects are often highly specialized plant feeders, for example, gall-formers, and frequently radiated and co-evolved with their host plants (Whitney and Glover 2013). The ubiquitous nature of insects, found in all terrestrial ecosystems (Grimaldi and Engel 2005), implies that every plant species is the food source of at least one herbivorous insect species, and even when this herbivore has not been directly observed, its presence can be inferred by observing the damage caused to the plant tissues

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