title: High-resolution food webs based on nitrogen isotopic composition of amino acids.
abstract: Food webs are known to have myriad trophic links between resource and consumer species. While herbivores have well-understood trophic tendencies, the difficulties associated with characterizing the trophic positions of higher-order consumers have remained a major problem in food web ecology. To better understand trophic linkages in food webs, analysis of the stable nitrogen isotopic composition of amino acids has been introduced as a potential means of providing accurate trophic position estimates. In the present study, we employ this method to estimate the trophic positions of 200 free-roaming organisms, representing 39 species in coastal marine (a stony shore) and 38 species in terrestrial (a fruit farm) environments. Based on the trophic positions from the isotopic composition of amino acids, we are able to resolve the trophic structure of these complex food webs. Our approach reveals a high degree of trophic omnivory (i.e., noninteger trophic positions) among carnivorous species such as marine fish and terrestrial hornets.This information not only clarifies the trophic tendencies of species within their respective communities, but also suggests that trophic omnivory may be common in these webs.
authors.affiliation: Japan Agency for Marine-Earth Science and Technology 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan.
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Chikaraishi
authors.affiliation: USDA-ARS Vegetable Crops Research Unit, 1630 Linden Dr., Department of Entomology, University of Wisconsin Madison, WI, 53706, USA.
authors.forename: Shawn A
authors.initials: SA
authors.lastname: Steffan
authors.affiliation: Japan Agency for Marine-Earth Science and Technology 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan.
authors.forename: Nanako O
authors.initials: NO
authors.lastname: Ogawa
authors.affiliation: Japan Agency for Marine-Earth Science and Technology 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan.
authors.forename: Naoto F
authors.initials: NF
authors.lastname: Ishikawa
authors.affiliation: Japan Agency for Marine-Earth Science and Technology 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Sasaki
authors.affiliation: Japan Agency for Marine-Earth Science and Technology 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Tsuchiya
authors.affiliation: Japan Agency for Marine-Earth Science and Technology 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan.
authors.forename: Naohiko
authors.initials: N
authors.lastname: Ohkouchi
keywords: Carnivores; compound-specific isotope analysis; ecosystem; herbivores; omnivores; predators; primary producers; trophic position