Plot-based sampling and rearing of adult lepidoptera from lowland rainforest in Wanang, Papua New Guinea

Study Extent

Two 1ha lowland humid tropical rainforest plots were sampled around Wanang Village, Madang, Papua New Guinea. (145°81'55'' E, 58°13'51'' S). Sampling occurred between XXX XXX

Sampling

We coordinated our sampling with local landowners who were planning to clear the sites for subsistence gardens. Each 100 x 100 m plot was subdivided into 20 x 20 m subplots. For each subplot, the understory (i.e., all vegetation ,1.4 m in height) was cleared followed by removal of all trees ,5 cm diameter with machetes while taking care to minimize disturbance to the remaining vegetation. Orderly felling of trees 5 cm in diameter with a chain saw proceeded one tree at a time from the midstory to the canopy by severing lianas and dropping trees into artificial gaps created during the course of subplot removal. This procedure minimized the disturbance of remaining vegetation as much as could be expected during logging. Immediately upon felling, trees were inspected for the presence of caterpillars and leaf miners by a team of eight field workers. Live caterpillars were hand-collected and placed in plastic vials for processing, whereas leaves containing miners were collected and stored in plastic bags. Caterpillar and leaf miner abundance per tree were obtained by summing total numbers of live insects. Following inspection of the foliage for herbivores, eight field workers manually stripped all leaves from each felled tree and weighed the total leaf biomass in kilograms. Specific leaf area (SLA), defined as fresh leaf area divided by dry leaf mass, was estimated from leaf disks punched from multiple individuals for all species in the survey plots with the dual purpose of DNA collection. Disks were collected from fully expanded, mature leaves without obvious signs of pathogen or herbivore damage. The disks had a diameter of 2.3 cm and were punched from fresh leaves in the field, temporarily stored in paper envelopes over silica gel, and subsequently stored in a -80C frozen tissue collection at the University of Minnesota (St. Paul, Minnesota, USA). Mean SLA per species was obtained by averaging multiple samples per species. The presence or absence of exudates including latex and resin was also noted. Leaves were sampled from up to four individuals per tree species for the measurement of foliar nitrogen. Three randomly chosen leaf samples per tree were bulked and ground by hand in liquid nitrogen or in a Tissuelyzer (Qiagen, Valencia, California, USA). Analysis was carried out at the University of Nebraska (Lincoln, Nebraska, USA) using dry combustion gas chromatography on a Costech analytical elemental combustion system ESC 4010 (Costech, Valencia, California, USA). This method yields the mass of an element that is subsequently converted to a percentage of the total mass of the sample.

Method steps

1. Full details can be found- Whitfeld, Timothy JS, et al. "Predicting tropical insect herbivore abundance from host plant traits and phylogeny." Ecology 93.sp8 (2012): S211-S222.

The study took place close to Wanang Village, Madang. The two plots were 800 m apart in a mosaic of primary and secondary rain forest vegetation at 100–200 m above sea level in an extensive mixed evergreen forest on latosols in the Ramu River basin.