Use of Isotopic Analysis of Insect and Freshwater Crustacean Chitin from Quaternary Sediments for Reconstruction of Past Natural Environments

An analysis of the isotopic composition of chitin (oxygen and nitrogen) was made for the first time for terrestrial and freshwater Pleistocene arthropods from the localities at the Old Crow River in northwestern Yukon, representing an interval from the middle Pleistocene to the Holocene. About a hundred fragments of arthropods were tested among the fossils, including the weevils Lepidophorus lineaticollis (Coleoptera, Curculionidae), some ground beetles (Coleoptera, Carabidae), as well as the ephippia of freshwater crustacean Daphnia cf. pulex (Branchiopoda, Daphniidae). An isotope analysis of extant representatives of the same arthropods from different regions of the Yukon was made for comparison. Isotopic lines show differences between terrestrial and freshwater animals. The isotopic composition of freshwater crustaceans shows the difference between cold and warm time intervals. Herbivorous beetles show a more complex picture, possibly associated with the adaptation to different biotopes and host plants, which allowed the species to survive during climatic and environmental fluctuations.