Niche Variation in Burying Beetles (Nicrophorus spp.) Associated with Marine and Terrestrial Carrion

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Ecological opportunity can influence niche variation within and among species. Forensic reconstruction of diet has been made possible with the now widespread use of stable isotope analysis, although it has not to date been applied to communities based on carrion resources. Within a salmon-bearing watershed in coastal British Columbia, we reconstructed the dietary niches of two burying beetle species (Silphidae: Nicrophorus investigator Zetterstedt, 1824 and Nicrophorus defodiens Mannerheim, 1846) using stable isotopes (δ15N, δ13C). We separated available carrion sources for beetles of chum salmon (Oncorhynchus keta (Walbaum, 1792)) and pink salmon (Oncorhynchus gorbuscha (Walbaum, 1792)), the shrew Sorex monticolus Merriam, 1890, songbirds (Troglodytes troglodytes (L., 1758), Catharus ustulatus (Nuttall, 1840), Catharus guttatus (Pallas, 1811)), and black-tailed deer (Odocoileus hemionus hemionus (Rafinesque, 1817)) into three isotopically homogeneous subsets: (1) salmon, (2) shrews and songbirds, and (3) deer. The majority (86.5%) of N. investigator individuals were raised on a diet of salmon carrion, while 100% of N. defodiens individuals had a larval diet consistent with carrion from shrews and songbirds. Larger isotopic variance predicts wider dietary niches, which may be useful for testing functional ecological variation within and among species.