Author
Rajaonera E Tahina
University of Antananarivo, Faculty of Sciences, Department of Entomology
Antananarivo, Madagascar
Coauthors
Simon Fowler, Bioeconomy Science Institute – Manaaki Whenua – Landcare Research Group, Lincoln, New Zealand
Chantal Probst, Bioeconomy Science Institute – Manaaki Whenua – Landcare Research Group, Auckland, New Zealand
Luise schulte, Bioeconomy Science Institute – Manaaki Whenua – Landcare Research Group, Auckland, New Zealand
Marc Rabenjamina, University of Antananarivo, Faculty of Sciences, Department of Entomology, Antananarivo, Madagascar
Abstract
Decalobanthus peltatus is an invasive vine that suppresses native vegetation in the Pacific region, but its ecology as a native plant in Madagascar remains understudied. We inventoried insects associated with D. peltatus across its Malagasy range, assessing their damage and identifying potential biocontrol agents. Field surveys were conducted at 45 sites in Analanjirofo, Antsinanana and SAVA regions. At each site, 30 leaves were sampled and visually assessed for six damage types. Insects were collected through 20-min intensive searches and 72-h Malaise trapping. Adults were morphologically identified; larvae were reared on D. peltatus and also tested on related plants. In total, 131 insect species from 59 families were identified, show D. peltatus as a host for diverse entomofauna, mainly Coleoptera and Lepidoptera. SAVA had the highest insect richness (87 spp.) and Sainte Marie the lowest (30 spp.) suggesting spatial variability in herbivore pressure on this plant. Limacodidae larvae caused up to 63.5% defoliation, with general defoliation being the most prevalent damage (65% in Sainte Marie) indicating strong biotic resistance against D. peltatus in its native range.
The presence of high defoliation suggest D. peltatus faces strong biotic resistance in Madagascar. Although causing high levels of damage, Limacodidae are not suitable biocontrol candidates due to their toxic, spiny larvae and uncertain host specificity. This study provides the first comprehensive assessment of D. peltatus herbivores in Madagascar, revealing a diverse entomofauna.
Keywords
Biological control
invasive species
Decalobanthus peltatus
herbivory
Madagascar
Highlights
131 insect species associated with Decalobanthus peltatus in Madagascar, revealing its role as a key host plant by insect species.
The presence of Limacodidae larvae, which can cause defoliation up to 36.5%, exhibits significant biotic resistance but is not suitable for biological control due to ecological risks.
The variation in pressure varies by region (SAVA has three times more insects than Sainte-Marie), suggesting ecological dynamics at the landscape scale.