Aquatic beetle assemblage in natural habitats of Agusan Marsh, Mindanao, Philippines

Abstract

This paper describes the species composition of aquatic beetles in major habitats of Agusan Marsh and determines their distribution, abundance and diversity. Aquatic beetles are among the dominant insects in freshwater wetlands occupying the base of the food webs in the ecosystem. Several species of aquatic beetles are ubiquitous in the marsh. A total of 27 species of aquatic beetles was collected. Of this, 14 species belong to Family Hydrophilidae, 11 species belong to Family Dytiscidae, and 1 species each belonging to Family Noteridae and Hydraenidae. Of the habitat types, the sedge-dominated swamp has the highest diversity of aquatic beetles, while the sago forest has the lowest. Hydrophilids especially the Berosus sp., Helochares sp. and Enochrus sp. are the most common species collected in the various habitats. However, certain species are found unique in specific habitats in the Agusan Marsh. Eretes sticticus was only collected in the Sago forest, while Sternolophus rufipes was only found in the Terminalia forest. Two species, Cercyon sp. and Platynectes sp. were also unique to the sedge-dominated swamp. The sedge-dominated swamp and Terminalia forest appeared to be the most preferred habitats of some unique species of aquatic beetles. The existence of unique species indicates the presence of distinct habitat characteristics which is a crucial consideration for biodiversity management and conservation.