Gall Apparency Drives Parasitoid Richness in a Highly Specialised Gall‐Parasitoid Food Web From a Tropical Rainforest
5 affiliations
- 1Institute of Entomology Biology Centre of the Czech Academy of Sciences Ceske Budejovice Czech Republic
- 2Faculty of Science University of South Bohemia Ceske Budejovice Czech Republic
- 3Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences Menglun, Mengla County Yunnan China
- 4School of Biological and Behavioural Sciences Queen Mary University of London London UK
- 5The New Guinea Binatang Research Centre Madang Papua New Guinea
Abstract
Understanding the complexity of interactions in quantitative terrestrial food webs is a key challenge in ecology, particularly in tropical habitats where reports are scarce. Documenting tri‐trophic interactions in these ecosystems is essential to advance understanding of how community dynamics and specialisation shape network structure. Here we present the largest and most comprehensive plant–gall–parasitoid network to date. We sampled galls and reared parasitoids from three sites in lowland rainforest near Madang, Papua New Guinea, and combined them into a single quantitative tri‐trophic network. Network statistics were calculated, and gall traits (taxon, apparency, openness, plant module, and pubescence) were tested as predictors of parasitoid richness. We also analysed the potential for apparent competition (PAC) among galls. The network comprised 32 host plant species, 78 galling insect species, and 102 parasitoid species represented by 820 individuals. Monophagous species dominated both gallers and parasitoids, producing high specialisation (H2′ = 0.99 for plant–gall and 0.90 for gall–parasitoid subwebs). Gall apparency and gall‐forming taxon significantly predicted parasitoid assemblage size: conspicuous galls formed by Cecidomyiidae hosted more parasitoid species. One third of gall species shared no parasitoids, and the remainder showed very low PAC, suggesting limited interspecific enemy‐mediated interactions but potential for intraspecific density dependence. The existence of highly specialised tri trophic food webs in tropical rainforests has been questioned, given the challenges posed by extreme specificity. Such networks require parasitoids specialised to herbivores that are themselves restricted to single plant species, raising doubts about their feasibility in diverse ecosystems. Our study demonstrates that these networks do occur, with gall forming insects and their parasitoids providing clear evidence of highly specialised tri trophic interactions in tropical forests. We also discuss the potential existence of a latitudinal gradient in gall‐parasitoid specialisation.
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BibTeX
@article{butterill2026gall,
title = {{Gall Apparency Drives Parasitoid Richness in a Highly Specialised Gall‐Parasitoid Food Web From a Tropical Rainforest}},
author = {Philip T. Butterill and Sam Finnie and Katerina Sam and Tom M. Fayle and Inga Freiberga and Vojtech Novotny},
journal = {Ecology and Evolution},
year = {2026},
month = oct,
doi = {10.1002/ece3.74375},
url = {https://onlinelibrary.wiley.com/doi/10.1002/ece3.74375},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Gall Apparency Drives Parasitoid Richness in a Highly Specialised Gall‐Parasitoid Food Web From a Tropical Rainforest
AU - Philip T. Butterill
AU - Sam Finnie
AU - Katerina Sam
AU - Tom M. Fayle
AU - Inga Freiberga
AU - Vojtech Novotny
PY - 2026
DA - 2026/10/06
JO - Ecology and Evolution
DO - 10.1002/ece3.74375
UR - https://onlinelibrary.wiley.com/doi/10.1002/ece3.74375
AB - Understanding the complexity of interactions in quantitative terrestrial food webs is a key challenge in ecology, particularly in tropical habitats where reports are scarce. Documenting tri‐trophic interactions in these ecosystems is essential to advance understanding of how community dynamics and specialisation shape network structure. Here we present the largest and most comprehensive plant–gall–parasitoid network to date. We sampled galls and reared parasitoids from three sites in lowland rainforest near Madang, Papua New Guinea, and combined them into a single quantitative tri‐trophic network. Network statistics were calculated, and gall traits (taxon, apparency, openness, plant module, and pubescence) were tested as predictors of parasitoid richness. We also analysed the potential for apparent competition (PAC) among galls. The network comprised 32 host plant species, 78 galling insect species, and 102 parasitoid species represented by 820 individuals. Monophagous species dominated both gallers and parasitoids, producing high specialisation (H2′ = 0.99 for plant–gall and 0.90 for gall–parasitoid subwebs). Gall apparency and gall‐forming taxon significantly predicted parasitoid assemblage size: conspicuous galls formed by Cecidomyiidae hosted more parasitoid species. One third of gall species shared no parasitoids, and the remainder showed very low PAC, suggesting limited interspecific enemy‐mediated interactions but potential for intraspecific density dependence. The existence of highly specialised tri trophic food webs in tropical rainforests has been questioned, given the challenges posed by extreme specificity. Such networks require parasitoids specialised to herbivores that are themselves restricted to single plant species, raising doubts about their feasibility in diverse ecosystems. Our study demonstrates that these networks do occur, with gall forming insects and their parasitoids providing clear evidence of highly specialised tri trophic interactions in tropical forests. We also discuss the potential existence of a latitudinal gradient in gall‐parasitoid specialisation.
SN - 2045-7758
SN - 2045-7758
ER -