Interactions between the invasive brown spruce longhorn beetle, Tetropium fuscum (Fabricius) (Coleoptera: Cerambycidae), and its native congener, Tetropium cinnamopterum (Kirby)

Abstract

Tetropium fuscum (TF) (Coletopetra: Cerambycidae) is a European spruce borer established in Nova Scotia since at least 1990. I tested whether TF displaces a native congener, T. cinnamopterum (TC), in red spruce. Stressed trees, 24 girdled and 24 felled, were selected for natural colonization: 28 inside the invaded zone and 20 outside. Both Tetropium species and their parasitoid wasps emerged exclusively from felled trees. Combined Tetropium density (inside invaded zone = 0.34 ± 0.07 vs. outside = 0.63 ± 0.19 per m2; P = 0.070) and overall parasitism rates (inside invaded zone = 31% vs. outside = 44%; P = 0.111) did not statistically differ inside vs. outside the invasion zone, but TC density was significantly greater outside the invasion zone (0.63 ± 0.19 compared to 0.18 ± 0.05 m2; P = 0.001), suggesting TF may displace TC where they are sympatric.