AMPHIBIANS IN HUMID TROPICAL ECOSYSTEMS OF SRI LANKA: THREATS

AND NEEDS FOR CONSERVATION

Thilina Dilan SurasingheDepartment of Zoology

University of Sri JayewardenepuraSri Lanka

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TROPICAL HUMID AMPHIBIANS OF SRI LANKA

Sri Lanka’s tropical humid ecosystems are rich in amphibian diversity and endemism

78% of islands’ amphibian fauna are confined to humid tropics

Family Ranidae of Sri Lanka is exceptional with 70 of 82 species are restricted to the humid tropics

97% of tropical humid amphibians are endemic

Three endemic genera Adennmus, Nannophrys, Lankanectes

One endemic subfamily – Lankanectinae

Local tropical humid amphibian hotspots… Central Highlands, Knuckles Range, Sabaragamuwa Range

Habitats of the tropical humid amphibians: Tropical moist lowland forestsMoist savanna High-altitude grasslands

Tropical moist montane forests Tropical swamp forests Wet grasslands

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WHY SO DIVERSE…? Absences of climate change in last 31000 years in rainforest

refugea Relatively stable environment Minimal climate induced extinction

Speciation via geographical disjunction of distribution Isolated large mountain-peaks and Long spanned mountain-ranges Geography-specific vegetation

Favorable climatic features Favorable optimum habitat conditions High year round precipitation High relative humidity Optimum temperature - 24-28 ºC

Heterogeneity in terrestrial, aquatic and arboreal habitats High niche spaces and partitions Vegetation complexity High microhabitat availability and diversification Elaborated hydrology and stream morphology

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THREATENED STATUS OF TROPICAL HUMID AMPHIBIANS

30 species gone extinct from humid tropics in past 10 years Adenomus kandianus, Nannophrys guentheri, Philautus adspersus

All falls under Red-List Categories Critically Endangered – 11 (Adenomus dasi, Microhyla karunaratnei) Endangered – 35 (Philautus zorro, Polypedates longinasus) Vulnerable – 6 (Ichthyophis pseudangularis, Rana aurantiaca) Near Threatened – 5 (Rana temporalis, Ramnella nagaoi)

All the Red-Listed Sri Lankan amphibians are restricted to the humid tropics Tropical moist lowland/motane forests

Most are spot endemics Ph. simba, Ph. lunatus, Polypedatus fastigo: Morningside Ph. mooreorum, Ph. fulvus, Ph. hoffmanni, N. marmorata: Knuckles

Hills Ph. limbus, Ph. nemus: Haycock Hill Ph. Alto, Ph. frankenbergi: Horton Plains

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THREATS TO THE AMPHIBIANSDeforestation and habitat destruction

Only 750 km2 are covered with tropical humid forestsSeverely disunited into 100km2 fragments or lessDeclining of population sizes Increased inbreeding within small forest patchesSeverely confront edge effect in small habitat patchesHigher vulnerability for disturbancesLower colonization and recovery rates Inbreeding drastically reduces the reproductive fitness/success

Inbreeding depression Inability to avoid predatorsLow diseases-resistanceHigh rates of juvenile mortality

Reduced genetic variationAccumulation of deleterious

mutations Small clutch sizes

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Invasion by alien species and domestic/village species imposes threats by… Direct predation and competitionHabitat alteration

Parasites and pathogens hamper the growth, reproductive success, physical

fitness and results direct mass mortality

Climate change Reduced amphibians’ distribution, abundance, feeding

nichesDisappearance of cloud-born mist with warming trend

dispels the humid environment for montane amphibians Modification in vegetation structure - conversion of

forests into bushlands and semi-arid torn forests

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Human-induced disturbances Extraction of forestry resources – Firewood & timber Encroachments into forests for cultivations

“Deniya” cultivation

Agro-chemicals and other environmental pollutants Adverse/harmful genetic mutations

Anatomical malformations Functional abnormalities

Chronic and acute physiological disorders Reduced reproductive output and low juvenile survival Mass mortalities due to direct toxicity Food scarcity due to destruction of forest insect communities by

pesticides

Acid depositions Predisposition for diseases: fungus Forest diebacks - Horton Plains Direct mortality in adults & tadpoles due to high acidity in water

Accidental causes Road kills

Fragmentation of extensive habitats by motor ways Operation of agricultural machinery

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CONSERVATIONExtension of protected area network

Recognition of gaps in protected areas Hanthana, Knuckles foothills, Central massif foothills

Recognition of local amphibian-hotspots Eg: Eastern Sinharaja and surrounding habitats Agra-Bopath Sanctuary

Extenuate degradation of core-forestEstablishment of buffer zonesRules and regulation enforcements to minimize disturbancesStrict physical protection Introduce alternatives for resource overexploitation

Prevention and elimination of invasions Bio-control mechanisms for eradication of invasive speciesContinuous monitoring for re-invasion

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Efficient ecosystem management Introduction of preferred native vegetationPlantation & conservation of gallery forestsProvision of ideal hydrological featuresEnhancing the landscape & macrohabitat diversity Management of microhabitat features – small

creeks, cascades, small forest pools, artificial phytotelms, talus, and crevice

Linkage of forest/habitat fragmentsSuitable habitat corridors to establish population

processes and metapopulationsRestoration of degraded habitats

Reforestation with native speciesEnrichment-plantation

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Adopting eco-friendly agricultural practices Agro-forestry and organic farming

Solutions for road mortality Road crossing structures: tunnel systems, wildlife bridges,

underpasses, viaducts

Species-based approaches: ex-situ conservation Re-introductions and translocations Intensive recovery management for critically endangered

species Clutch manipulation Provision of artificial nesting sites

Elimination or mitigation of species specific threats Disease prevention by quarantine regulations Elimination of disease/parasite hosts/reservoirs Medical provisions Captive maintenance of healthy populations Captive breeding/artificial propagation and releasing to the wild Establishing a genome resource bank

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SOME TROPICAL HUMID AMPHIBIAN HABITATS OF SRI LANKA

Agra-Bopath Sanctuary Kanneliya Forest Reserve

Sinharaja MAB Reserve Knuckles Conservation Forest