Mosses are some of Earth’s most species rich, ancient, and stress-tolerant “ecosystem engineers”. Although traditionally lumped into one functional category, mosses are incredibly functionally, physiologically and chemically diverse. Although mosses appear to have an extensive arsenal of chemical defenses, bryophyte herbivory by invertebrates is remarkably poorly characterized, creating a fundamental gap in our basic understanding of plant-animal interactions and the ecology of Earth’s earliest terrestrial plants. Here, we used food choice assays and survival experiments with larvae of the large yellow underwing moth (Noctua pronuba L.), an invasive generalist herbivore, to determine the relative effects of moss species and a control on herbivore food choice and survival. We used three moss species, Ceratodon purpureus, Polytrichum juniperinum,and Racomitirium lanuginosum, and a grass species, Poa annua, that are commonly found in N. pronuba habitat with N. pronubaherbivory.
We analyzed carbon and nitrogen levels for each food type as well as for N. pronuba frass. N. pronuba larvae were observed to feed on both grass and moss tissue, however survival rates were highest for N. pronuba larvae feeding on the grass P. annua and the moss C. purpureus and lowest for individuals feeding on the moss R. lanuginosum. Relative growth rate of the larvae was significantly influenced by food choice, and its attendant C:N ratio. Despite our relatively poor understanding of the role of herbivory in bryophyte ecology, here we show that mosses may be an important alternative food source for Noctua pronuba larvae, although strong moss species-specific effects may influence this plant-animal interaction.