The assemblages of root-feeding chrysomelid larvae from 21 locally common tree species were studied in a secondary tropical forest in New Guinea and compared with confamilial larvae and adults feeding on the foliage. Fieldwork was performed in an approximately 6-km2 mosaic of secondary and primary forest vegetation near Ohu Village.
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The study was conducted in a mosaic of primary and secondary lowland humid rainforest near Ohu Village, Madang province, Papua New Guinea, at an elevation average of 150– 200 m a.s.l. and an annual rainfall of 3558 mm with low seasonal variation. The diverse vegetation is classified as mixed evergreen hill forest.
|Bounding Coordinates||South West [-5.25, 145.668], North East [-5.239, 145.686]|
The assemblages of root-feeding chrysomelid larvae from 21 locally common tree species were studied in a secondary tropical forest in New Guinea and compared with confamilial larvae and adults feeding on the foliage. Larval host plants were inferred from adults emerging from the soil containing the roots of known tree species. In total, 2495 chrysomelids from 100 species were reared from the roots. Almost 90% of adults in the forest canopy recruited from the species with root-feeding larvae, while species with leaf-feeding larvae represented 1% of individuals (the feeding guild for the remaining 9% was unknown). The root-feeding larvae were thus more important in tropical than temperate forests, possibly because of predation pressure by ants on tropical vegetation. The number of chrysomelids emerging annually from the soil in 1 ha of the forest was approximately 0.2 million. Root-feeding larvae were polyphagous as their modal host range included three or four from the six plant families studied. The lack of correlation between the phylogenetic distance of tree species and the similarity of their chrysomelid assemblages indicated that host choice was not constrained by plant phylogeny. The host range of larvae feeding on roots was as wide as that of the conspecific adults feeding on the foliage. The density and species composition of larval and adult assemblages on the studied trees were not correlated. These results suggest that even studies restricted to adult assemblages, which represent a majority of chrysomelid studies, can be informative, as the composition of adult assemblages is not necessarily constrained by larval host-plant selection.
|Title||Host specialization and species richness of root-feeding chrysomelid larvae (Chrysomelidae, Coleoptera) in a New Guinea rain forest|
|Funding||The study was funded by the Darwin Initiative for the Survival of Species (162/10/030), U.S. National Science Foundation (DEB-97-07928, 02-11591) and the Czech Academy of Sciences (A6007106).|
|Study Area Description||The study area was situated in the Madang Province of Papua New Guinea. It has a humid tropical climate with average annual rainfall of 3558 mm, a moderate dry season from July to September, and mean air temperature 26.5 ◦C. Fieldwork was performed in an approximately 6-km2 mosaic of secondary and primary forest vegetation near Ohu Village (145 ° 41' E, 5 °14' S, 200m asl). The study was conducted in a 5–30-y-old succession forest (described in Novotny et al. 2004b) bordered by primary lowland hill forest. Succession typically starts in abandoned garden clearings after traditional swidden agriculture, but similar succession follows natural disturbance events such as tree falls and landslides (Johns 1986, Leps et al. 2001). Vegetation from a 1-ha area included 6848 stems taller than 1.5m from 171 species, 120 genera and 54 families.|
|Design Description||The assemblages of root-feeding chrysomelid larvae from 21 locally common tree species were studied in a secondary tropical forest in New Guinea and compared with confamilial larvae and adults feeding on the foliage. Larval host plants were inferred indirectly, based on the adults that emerged from the soil that included predominately or exclusively roots of the putative host tree species. Host specificity of chrysomelids was analysed using two data sets with the number of traps and the length of their exposure standardized for all tree species. Host specificity was quantified as the percentage of individuals (P) feeding on a single, most preferred host-plant species from those studied. The species with P≥90% of individuals feeding on a single host were considered specialized to this host (Thomas 1990). Although arbitrary, we preferred this threshold to the strict definition, requiring that all individuals feed on a particular plant taxon as some of the reared individuals may have fed on roots other than those of the target tree species. The proportion of chrysomelid species specialized to a single plant species, genus and family was determined from data sets including potential alternative hosts from respectively the same genus, different confamilial genus, and different family. The following data sets were used: (1) four Ficus species, (2) three Macaranga species, and single representatives of (3) four Euphorbiaceae genera, (4), four Malvaceae genera, (5) two Moraceae genera, (6) two Verbenaceae genera and (7) six plant families.|
The personnel involved in the project:
Sample included eighty mature trees, 2–12 per tree species, from 21 tree species were selected for the study. Vegetation within a 5-m radius around each target tree was cleared and a trap designed to collect insects emerging from the ground was placed within a 2-m radius of each target tree. The trap was a 1 × 1-m square, 15-cm-high wooden frame embedded5cmdeep in the soil and covered with strong black cloth on top. Single transparent plastic containers partly filled with 70% ethanol were inserted in two opposite sides of the frame. Insects emerging from the 1-m2 area of the soil within the trap were attracted by light to the containers where they were collected in ethanol. Traps were emptied at weekly intervals. All collected chrysomelids were mounted, sorted to morphospecies and identified as far as possible by Samuelson. Voucher specimens are deposited at the National Agriculture Research Institute in Port Moresby and Bishop Museum in Honolulu. The traps were run in three consecutive series: the S1 series comprised eight traps run for 6mo (1 May– 31 October 2002), the S2 series comprised 36 traps run for 11 months (21 November 2002 –21 October 2003), and the S3 series comprised 36 traps run for 6 months (22 December 2003–22 June 2004). A different tree was used for each trap and series and the trees from different species were intermingled within the study area to avoid pseudoreplication.
|Study Extent||The study area was situated in the Madang Province of Papua New Guinea. It has a humid tropical climate with average annual rainfall of 3558 mm, a moderate dry season from July to September, and mean air temperature 26.5 °C (McAlpine et al. 1983). Fieldwork was performed in an approximately 6-km2 mosaic of secondary and primary forest vegetation near Ohu Village (145°41' E,5°14' S, 200m asl). Sample included eighty mature trees, 2–12 per tree species, from 21 tree species were selected for the study.|
Method step description:
- Full details can be found- Pokon, Rapo, Vojtech Novotny, and G. A. Samuelson. "Host specialization and species richness of root-feeding chrysomelid larvae (Chrysomelidae, Coleoptera) in a New Guinea rain forest." Journal of Tropical Ecology 21.6 (2005): 595-604.
- R. Pokon, V. Novotny, and G. Samuelson, “Host specialization and species richness of root-feeding chrysomelid larvae (Chrysomelidae, Coleoptera) in a New Guinea rain forest,” Journal Of Tropical Ecology, vol. 21, no. Part 6, pp. 595–604, Nov. 2005. https://doi.org/10.1017/S0266467405002567