Can alien plants support generalist insect herbivores?

Abstract

Simple rearing experiments were conducted to address two questions relevant to understanding how generalist lepidopteran herbivores interact with alien plants. Yellow-striped armyworm (Spodoptera ornithogalli), luna moth (Actias luna), bagworm (Thyridopteryx ephemeraeformis) and white-marked tussock moth (Orgyia leucostigma) were reared from egg to 5th instar on excised foliage in the laboratory to determine the degree to which highly polyphagous lepidopteran herbivores are physiologically capable of surviving and developing on the suite of alien plants naturalized in the midAtlantic. Actias luna larvae from a single population were similarly reared on a representative of each of the 25 native plant genera recorded as hosts for this species to compare the diet breadth of a local population with that listed over the entire geographic range of the species. With few exceptions, all four generalists either quickly starved or grew at an unsustainably low rate on alien foliage. Actias luna larvae survived for 18 days on only 44% of the native plants recorded as hosts over the entire range of this insect and thrived on only 7%. The data suggest that (1) alien plants are unlikely to produce as much generalist insect biomass as the native plants they replace and (2) Lepidoptera that qualify as generalists when host breadth is considered over their entire geographic range may express a far more specialized diet within local populations. Both of these conclusions support the hypothesis that alien plant invasions may seriously disrupt terrestrial food webs by reducing the insect biomass required by insectivores in higher trophic levels.

Biodiversity, photosynthetic mode, and ecosystem services differ between native and novel ecosystems

“…There are also several ecosystem services that remain to be fully explored. Insect herbivores and predators (Tallamy et al 2010) as well as other animals in addition to bees should be compared between native and exotic grasslands in future studies.…”

Non‐native plants reduce abundance, richness, and host specialization in lepidopteran communities

“…However, even the most generalized insect herbivores use only a small fraction of the plants in their environments (Tallamy and Shropshire 2009). Moreover, many generalists are far more specialized locally than their geographic host breadth indicates (Fox and Morrow 1981, Scriber 1983, Tallamy et al 2010.…”

Exotic Plant Invasion in the Context of Plant Defense against Herbivores

“…Due to lack of specialist herbivores, exotic plants may have better growth and reproduction (EICA), higher production of less costly defense compounds (SDH), and competitive abilities in terms of higher production of chemicals novel for the invaded community (NWH; see also Supplemental Box S1). Exotic plants may face less attack from generalist herbivores of introduced ranges because of the preference of generalist herbivores toward native plants (Tallamy et al, 2010), and exotic plants can be more resistant to generalist herbivores compared to their native congeners (Leger and Forister, 2005). Apparent competition (Orrock et al, 2008(Orrock et al, , 2010 and facilitation with native plants (Cushman et al, 2011) are two mechanisms related directly to interaction with other plants but also indirectly reallocate resources to influence defense against generalist herbivores.…”

“…Some generalist herbivores prefer native plants over exotic plants (Cappuccino and Carpenter, 2005;Han et al, 2008;Ridenour et al, 2008;Tallamy et al, 2010). Herbivores from Portuguese coast, including gastropods (Gibbula umbilicalis, Gibbula pennanti), sea hare (Aplysia punctata), and sea urchin (Paracentrotus lividus) prefer native seaweeds, Laminaria ochroleuca, Bifurcaria bifurcata, Mastocarpus stellatus, Chondrus crispus, and Osmundea osmunda, and avoid the invasive Sargassum muticum (Monteiro et al, 2009).…”