Trophic structure of ground-dwelling insects in the coastal zone of a salt lake in southern Siberia based on the data of isotopic analysis

The trophic structure of a ground-dwelling insect community has been studied in the coastal zone of a salt lake in the southern forest-steppe (Novosibirsk oblast). Five contrasting habitats along a 170-m catena with an altitude drop of 1.8 m were studied. In each habitat, the soil, as well as dominant insect and plant species, were sampled: phytophages, saprophages, and predators. According to a stable-isotope analysis of carbon and nitrogen (δ13C and δ15N), phytophagous insects (the locust Epachromius pulverilentus and carabid beetle Dicheirotrichus desertus) are closely connected to their food objects and hardly migrated along the catena. Saprophages (the mole cricket Gryllotalpa unispina and earwig Labidura riparia) use various food resources; some of them (mole crickets) tend to migrate between the biotopes. Predatory beetles (carabid imagoes) can be separated into three trophic guilds: (1) highly mobile active predators, including the tiger beetles Cephalota chiloleuca and C. elegans; (2) small generalist predators of Pogonini tribe (Pogonus cumanus, P. transfuga, Pogonistes rufoaeneus, and Cardiaderus chloroticus); and (3) relatively large consumers of soil saprophages and aquatic organisms (Curtonotus propinquus and Cymindis equestris). The trophic niche overlap of different predators is partially compensated by their confinement to different habitats.