A 7000-year record of insect communities from a peatland environment, southern Québec

Abstract

:We present a detailed paleoentomological analysis of a 4-m peat section sampled in a paludified dunefield in the St. Lawrence Lowland, Québec, and covering the last 7000 years. A minimum of 907 insect individuals were recovered, representing 133 taxa (53 identified to the species level) in 26 families and 5 orders. Four insect zones were identified. Zone 1 (6800-4130 years BP) was insect-rich, including many ground beetle species from wet and dry environments. Aquatic and rove beetles were abundant. Zone 2 (ca 3800 years BP) was very poor in insects. This zone was a sand layer associated with erosion of the dune slope during a short period of high water level in a beaver pond. Zone 3 (3800-3300 years BP) contained many aquatic beetles and ants, and some bark beetles. Zone 4 (3300 years BP to present) was mainly characterized by the abundance of rove beetles, the presence of two introduced species in the upper (50 cm) layer of the peat section, and the abundance of the bark beetle Polygraphus rufipennis. The study site falls within the known modern range of all but one of the identified species. In general, the relationship between the species composition of the vegetation and the insect communities remained obscure through the 7000-year sequence. However, changes in the insect communities were in agreement with information on their ecological requirements documented in the literature. The stability of the paleoentomofauna indicates that most insects were not influenced by the overall climatic fluctuations of the last 7000 years.