Feeding guilds in Collembola based on nitrogen stable isotope ratios

Abstract

in soil a high number of species co-exist without extensive niche differentiation, which was assigned as 'the enigma of soil animal species diversity'. In particular, the detritivores are regarded as food generalists. We have investigated nitrogen stable isotope ratios (N-15/N-14) of a major decomposer group, the Collembola, to evaluate trophic relationship and determine feeding guilds. Additionally, the delta(15)N values of potential food sources such as mosses, lichens and other plant derived material (bark, nuts, leaves) were analysed. The natural variation in nitrogen isotopes was assessed in 20 Collembola taxa from three deciduous forest stands. The delta(15)N signature formed a continuum from phycophages/herbivores to primary and secondary decomposers, reflecting a gradual shift from more detrital to more microbial diets. The delta(15)N gradient spanned over 9 delta units, which implies a wide range in food sources used. Assuming a shift in N-15 of about 3 parts per thousand per trophic level, the results indicate a range of three trophic levels. These variations in 15 NI 14 N ratios suggest that trophic niches of Collembola species differ and this likely contributes to Collembola species diversity. (c) 2005 Elsevier Ltd. All rights reserved.