Amphibian diversity and endemism in the swamp forests of Agusan Marsh, Agusan del Sur, Philippines

摘要

Agusan Marsh, an ecologically significant wetland in the Philippines, consists of an extensivefloodplain heavily dissected by numerous rivers and streams making it a very important source offreshwater, storing more than 15% of the nation’s freshwater resource in the form of swamp forests.Since amphibians are very good indicators of climate change and ecosystem health, species diversity andendemism were assessed in sago swamp, terminalia, mixed swamp, and peat swamp forests in AgusanMarsh using a combination of cruising, pitfall trap and quadrat methods. Seventeen species with 41%endemism were recorded. Of the seven endemic species, five are Mindanao endemic. The twoundescribed species of Oreophryne and one Philautus could be new species and were observed in theterminalia, sago, and mixed swamp forests but not in the peat swamp forest. The peat swamp forestwhere the invasive Rhinella marina was abundant, had the least species richness owing to habitatdisturbance brought about by human encroachment. The highest species richness and abundance wereobserved in the terminalia forest primarily due to the presence of suitable microhabitats. Four vulnerablespecies were recorded in the marsh. Most of the vulnerable and endemic species were documented in theterminalia and mixed swamp forests. High diversity and more or less even distribution were observed inall sites. Three amphibian species are considered socio-economically important and are hunted for foodand bait for fish. The presence of endemic and vulnerable species indicates that Agusan Marsh is a keyconservation site. Logging and widespread mining, discharging tons of mine tailings into the rivers whichfind their way into the swamp forests are just some of the threats to the amphibians in the marsh.Conservation action is necessary to protect the endemic and vulnerable species in the swamp forests andthe Agusan marsh in general.