Bottom‑up impact on the cecidomyiid leaf galler and its parasitism in a tropical rainforest
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Date
2014
Journal Title
Journal ISSN
Volume Title
Publisher
Oecologia
Abstract
The relative importance of host-plant resources,
natural enemies or their interactions in controlling the
population of galling insects and their parasitism is poorly
known for tropical gallers. In this study, we assessed the
impacts of plant quality and density of host trees in regulating
the densities of a galler species, the cecidomyiid
leaf galler (Cecidomyiini sp. 1EJV) and its parasitoids and
inquilines on Neoboutonia macrocalyx trees in Uganda.
We manipulated the nutritional quality (or vigour) and the
resource concentration with four levels each of fertilization
and the group size of host tree. We then recorded the
effects of these treatments on the growth rate and total leaf
area of host plants, the density of gallers and their mortality
by parasitoids and inquilines. Higher levels of fertilization
and host density resulted in significantly higher total
leaf area than did ambient nutrient levels, and lowest tree
densities, respectively. Fertilization also caused significant
change in the growth rate of leaf area. Both higher fertilization
and host density caused higher density of gallers. Total leaf area was positively associated with galler density,
but within galled replicates, the galled leaves were larger
than the ungalled leaves. Although highest levels of fertilization
and density of host trees caused significant change
in the densities of parasitoids, the rate of parasitism did not
change. However, tree-density manipulations increased
the rate of inquilinism, but on a very low level. Our results
demonstrate a trophic cascade in the tropical galler and its
parasitoids as a response to bottom-up effects.
Description
Keywords
Plant quality, Plant vigour, Resource concentration, Trophic cascade, Tropical gallers
Citation
Malinga, G. M., Valtonen, A., Nyeko, P., Vesterinen, E. J., & Roininen, H. (2014). Bottom-up impact on the cecidomyiid leaf galler and its parasitism in a tropical rainforest. Oecologia, 176(2), 511-520. DOI 10.1007/s00442-014-3024-5