Many caterpillars in a montane rain forest in Ecuador are not classical herbivores

Abstract

Abstract:Lepidopteran caterpillars are typically classified as herbivorous insects. Other feeding associations have been known for a long time but are often neglected in the ecological literature. In samples from 194 shrubs belonging to 16 species of Piperaceae and Asteraceae, which were taken in a montane forest and succession habitats in southern Ecuador, caterpillar assemblages included an unexpectedly large fraction not feeding on the living biomass of their putative ‘host’. Feeding trials revealed them to instead feed on foliose lichens, dead leaves and epiphylls (lichen, algae, bryophytes). These ‘alternative feeders’ accounted for 22.5% of the whole dataset and up to 80% of the caterpillars on individual plant species. Densities of alternative feeders were very similar across shrub species within each plant family, but differed strongly between Asteraceae in succession and Piperaceae in forest habitats. Herbivore caterpillars showed the opposite pattern with strong differences between individual plant species, but overall similar densities on both plant families.

Caterpillar assemblages on Chusquea bamboos in southern Ecuador: abundance, guild structure, and the influence of host plant quality

“…This supports the assumption of Bodner et al . () that feeding‐guild fractions strongly depend on the focal plant taxon. All observed alternative feeders encountered in our study belonged to families which are known to include non‐herbivores, especially detritus or epiphyll feeders.…”

“…(, ), who showed that feeding guilds other than strict herbivores make up a considerable fraction of tropical caterpillar assemblages in comparison to temperate zones. However, the non‐herbivore fraction on Chusquea bamboos (41.6%) in the montane rain‐forest zone was significantly higher than on various species of Piper and Asteraceae in the same area (22.5%: Bodner et al ., ). This supports the assumption of Bodner et al .…”

“…In line with recent findings in the same area by Bodner et al . (), we further expect that feeding guilds other than strict herbivores comprise a substantial fraction of the caterpillar assemblage associated with these climbing bamboos. Finally, we test whether caterpillar assemblages differ along ecological gradients, as environmental parameters affect foliage quality, nutritional availability, and insect herbivory (Werner & Homeier, ).…”

“…These alternative food resources are exploited by a considerable fraction of species within several Lepidoptera clades. Detritivorous caterpillars are not restricted to the leaf litter layer, but may also occur above‐ground on herbaceous or woody plants, where they feed on dead plant biomass (Bodner et al ., ). Epiphyll grazing caterpillars scrape algae, mosses, and lichens from leaves (Moskowitz & Westphal, ; Bodner et al ., , ).…”

Moth assemblages in Costa Rica rain forest mirror small‐scale topographic heterogeneity

“…Moreover, due to the high relative humidity in the forest understory along the creeks, leaves are very quickly overgrown by epiphylls (lichens, algae, and fungi) and hence not acceptable to many herbivores which predominantly prefer fresh leaves (Coley & Barone, ; Coley, Kursar & Machado, ; Toomey, Roberts & Nelson, ). Recent studies have shown that, in tropical mountain forests, caterpillars that feed on dead plant parts or graze on epiphylls play a very substantial role (Bodner, Brehm & Fiedler, ; Seifert, Lehner, Bodner & Fiedler, ), but it remains to be shown how important these particular caterpillar guilds are in tropical lowlands. Furthermore, the moist microclimate of the creek forests might facilitate the activity and spread of pathogens, thereby increasing early life stage mortality and finally leading to a lower moth abundance (Hilt, Brehm & Fiedler, ; Intachat, Holloway & Staines, ): (b) Lower plant species richness at creek sites might constrain moth species richness.…”