Trophic ecology of a tropical aquatic and terrestrial food web: insights from stable isotopes ( 15 N)

Weusedstableisotopeanalysis( 15 N/ 14 N)tocharacterizethetrophicrelationshipsofconsumercommunities of an aquatic food web (a permanent pond) and the adjacent terrestrial food web (secondary dry dipterocarp forest) fromaseasonaltropicalfieldsiteinnorth-easternThailand.Ingeneral, isotopicsignaturesofaquaticvertebrates were higher (δ 15 N range =4.51-9.90‰) than those of invertebrates (δ 15 N range =1.10-6.00‰). High 15 N signatures identifiedwatersnakesandswampeelsastoppredatorsinthepondfoodweb.Intheterrestrialfoodweb 15 Nsignatures ofsaprophagouslitterinvertebrates(diplopods,earthworms),termites,antsandbeetlelarvaewerelowerthaninthose ofpredatoryinvertebrates(scolopendrids,scorpions,whipspiders).Predatoryterrestrialfrogsandcaecilianshadlower 15 N signatures than snakes, indicating that snakes are among the top predators in the terrestrial web. Based on the distribution of isotopic signatures, we estimated five trophic levels for both the aquatic and terrestrial food web. The foodchainsofaseasonaltropicalsitestudiedwererathershort,whichimpliessimilaritiestothestructureoftemperate food webs.