Altitudinal Patterns of Insect Pest and Natural Enemy Diversity in Tidore Chili Pepper (Capsicum frutescens L.): A Qualitative Systematic Review Protocol

Background and rationale: Altitude is a key environmental gradient influencing insect pest diversity and natural enemy communities in agricultural ecosystems. Tidore chili pepper (Capsicum frutescens L.), widely cultivated across different elevation zones on Tidore Island, provides an important model for understanding elevation-related ecological dynamics. However, existing studies are fragmented across regions and systems. A systematic synthesis is necessary to identify general patterns and ecological mechanisms affecting pest and natural enemy diversity along altitudinal gradients, particularly in tropical island agroecosystems. Objectives: This systematic review aims to synthesize published ecological evidence on how altitude influences insect pest diversity, natural enemy communities, and pest–natural enemy interactions in chili pepper agroecosystems. Primary research question: How does altitude affect insect pest diversity in chili pepper agroecosystems? Secondary questions: 1. How do natural enemies (predators and parasitoids) respond to altitudinal gradients? 2. How do pest–natural enemy interactions vary across elevation zones? 3. What ecological mechanisms explain elevation-related diversity patterns? Eligibility criteria: Inclusion criteria: • Studies reporting ecological field data on insect pests and/or natural enemies • Studies conducted in chili pepper (Capsicum frutescens L. or Capsicum spp.) or comparable crops • Studies examining elevation or altitude gradients • Studies reporting diversity metrics (abundance, richness, diversity indices) • Studies conducted in tropical or subtropical agroecosystems • Peer-reviewed journal articles Exclusion criteria: • Studies without primary ecological data • Studies lacking clear sampling or identification methods • Molecular-only studies without ecological interpretation • Non-insect organisms • Duplicate publications • Unavailable full text Search strategy: Literature searches will be conducted using the following databases: • Scopus • Web of Science • ScienceDirect • DOAJ • Google Scholar • SINTA-indexed journals • Institutional repositories Search keywords will include combinations of: “Capsicum frutescens”, “Tidore chili pepper”, “Capsicum spp.”, “insect pest”, “insect diversity”, “natural enemies”, “predators”, “parasitoids”, “altitude”, “elevation gradient”, “agroecosystem”, “tropical agriculture”. Boolean operators (AND, OR) will be used. Study selection process: Study selection will follow PRISMA 2020 guidelines: 1. Identification 2. Screening (title and abstract) 3. Eligibility (full-text review) 4. Inclusion Data extraction: Data extracted will include: • Author and year • Study location • Elevation range • Crop type • Insect taxa • Diversity indices • Environmental variables • Pest–natural enemy interactions Quality assessment: Study quality will be evaluated using modified Critical Appraisal Skills Programme (CASP) and Joanna Briggs Institute (JBI) criteria adapted for ecological research. Data synthesis: A qualitative narrative synthesis will be conducted. Studies will be grouped into elevation categories: • Low elevation: 0–200 m asl • Mid elevation: 200–400 m asl • High elevation: 400–700 m asl Meta-analysis will not be performed due to heterogeneity in study design and ecological metrics. Timeline: Protocol registration: 2026 Literature search: 2026 Screening and extraction: 2026 Manuscript preparation: 2026 Keywords: Capsicum frutescens, Tidore chili pepper, insect pest, natural enemies, altitude, elevation gradient, agroecosystem, systematic review