Habitat Suitability of Megalopteran Communities in Thailand: Conservation Implications Under Climate Change

Members of the insect order Megaloptera (alderflies, fishflies, dobsonflies) are ecologically important freshwater insects and valuable biological indicators in freshwater biomonitoring programs, yet their spatial patterns and vulnerability to climate change in Southeast Asia remain poorly understood. We compiled 116 occurrence records representing 23 species across seven genera from the Global Biodiversity Information Facility (GBIF) database, published literature, and our field surveys. We examined the distribution of megalopterans across freshwater ecoregions in Thailand, assessed genus-level associations with climatic, topographic, and landscape variables, and projected habitat suitability under current and future climate scenarios. Our results showed significant differences among genera in elevation, proximity to river and canal networks, and climatic factors, including temperature, humidity, and precipitation. Using a range of modeling approaches based on 19 bioclimatic variables from the WorldClim database, we found that habitat suitability for megalopterans is most strongly driven by the mean temperature of the driest quarter (BIO9), precipitation of the wettest month (BIO13), and maximum temperature of the warmest month (BIO5). Our results indicated that approximately 40% of Thailand (209,170 km2) currently provides suitable habitat for megalopterans overall. However, future climate scenarios predict substantial habitat loss, with moderate- and high-suitability areas declining sharply by the 2050s and nearly disappearing by the 2090s under high-emission pathways. Our findings underscore the vulnerability of megalopterans in Thailand to climate warming and seasonality, emphasizing the urgent need for freshwater ecosystem conservation and global mitigation efforts to protect tropical aquatic insect diversity.