Mag. Dr. Florian Bodner


PhD Thesis

PDF at the University of Vienna

Caterpillar communities on shrubs in the montane forest zone of southern Ecuador

Caterpillar communities were studied on 16 shrub species from the family Asteraceae and the genus Piper (Piperaceae) in the Andean montane rainforest zone of southern Ecuador. The applied sampling methodology was evaluated and found well suited for sampling of caterpillars, especially with focus on resampling.

During standardized sampling, a total of 18890 specimens were collected in 11 field surveys between August 2007 and June 2009. Overall, samples were dominated by gregarious early instars and egg clutches of Altinote dicaeus albofasciata (Nymphalidae) on Erato polymnioides (Asteraceae). Those and all other such groups and egg clutches were down-weighted for analyses to their cubic root to balance against their overrepresentation in the data set. Trophic associations of caterpillars were confirmed by feeding trials. A substantial fraction of more than 22% of the encountered caterpillars (and up to 80% on individual shrub species) was found not to be trophically linked to the living biomass of the shrubs themselves (“non-herbivores”), but rather feed on dead leaves and epiphylls.

Abundance of non-herbivores differed strongly between the two studied plant families, but was very similar on different shrub species within these families. Abundance of herbivorous caterpillars, to the contrary, differed hardly between plant families, but varied strongly between individual plant species.

Herbivores were almost entirely comprised of ectophagous folivores, while florivores (2.3%) and semi-endophagous folivores (leaf rollers and tiers; 6.0%) were unexpectedly rare. Absolute species richness of herbivorous caterpillars was high, with a total of 191 Lepidoptera species on the studied 16 shrub species, but varied up to 40fold between individual plant species. Rarefied species numbers were more similar among plant species, but still showed a 15fold difference between the most species rich and most species poor community. Communities on Piper species were characterized by low effective species numbers (measured as exponential Shannon entropy) and high dominance of one or two species of the Geometridae genus Eois. E. polymnioides featured a similar structure dominated by A. dicaeus albofasciata.

Communities on the other two Asteraceae (Ageratina dendroides and Baccharis latifolia), to the contrary, were found to have high effective species numbers and low dominance. In conclusion, while Piper species and E. polymnioides feature caterpillar communities defined by small, predictable sets of core herbivores, these defining sets do not exist for the other two of the studied Asteraceae species.

Communities on Piper were also more specialized, with 62.8% of the caterpillar species considered monophagous at plant species level, than on Asteraceae with only 11.6% monophagous species.

The observed diversity patterns point mainly to shaping by (chemical) plant-herbivore-defense, while geographic range and local abundance of host plants appear to have only limited and varying influence on the associated caterpillar communities.

Diploma Theses

PDF at the University of Vienna

Early stages and feeding ecology of loopers (Lepidoptera: Geometridae) in a south Ecuadorian montane rainforest.

Early stages and feeding ecology of loopers (Lepidoptera: Geometridae) in a south Ecuadorian montane rainforest Abstract During four months of field su rveys at the Reserva Biológica San Francisco in the south Ecuadorian Andes, caterpillars of 64 Geometridae species were collected in a montane rainforest between 1800 and 2800m altitude and reared to adulthood. The resulting data on host plant affiliations of these species is listed and compared with published literature records on species and genus level.

Data on larval and pupal morphology is presented, together with data on rearing success and on the proportion of parasitoid infestation. Characteristic features of larval morphology and behaviour are described. For 56 species these are the first records ever to be assembled of their early stages, and for another 5 species the data significantly extend known host plant ranges. Most larvae were collected on woody plants (64% of species).

The most important host plant families were Melastomataceae (12 species recorded) followed by Asteraceae and Piperaceae (eight species each), and Dennstaedtiaceae (seven species). Unusual host plant affiliations recorded during this study were a quite high number of seven (11%) fern feeding species (mainly on Dennstaedtiaceae) and 3 (5%) lichen feeding species. The genus Eois was confirmed as being bound to larval host plants in the genus Piper. Overall, 17% of all larvae (and 34% if only considering those that were reared until the emergence of an adult moth or a parasitoid) died as a consequence of parasitoid infestation, mostly by braconid wasps (41%) and tachinid flies (20%), but also by representatives of the hymenopterous families Ichneumonidae, Chalcididae and Eulophidae.

Solitary parasitoids were far more prevalent than gregarious ones. Four geometrid species (6%) were proven to be polyphagous as larvae, for another five (8%) circumstantial evidence suggests that these are also polyphagous, and only six species (9%) are good candidates for true (local) monophagy. As many as 35 species (55%) were only recorded in single individuals. Host plant data from this study in combination with records from literature and internet databases cover now 9.1% of the 1266 geometrid species known from the study area, and even 10.9% of the 972 species 3 recorded from the elevational belt of 1800-2200m a.s.l. around the Estación Científica San Francisco.

Thus, four months of survey allowed to double the available knowledge on host plant relationships in this particular insect group, relative to the study site. Colour plates depict both the preimaginal stages of 63 and adult stages of 64 species to allow for further comparison and assist with identifications.