Original Paper

Biological Invasions

, Volume 15, Issue 7, pp 1573-1589

Open Access This content is freely available online to anyone, anywhere at any time.

How rapidly do invasive birch forest geometrids recruit larval parasitoids? Insights from comparison with a sympatric native geometrid

  • O. P. L. VindstadAffiliated withDepartment of Arctic and Marine Biology, University of Tromsø Email author 
  • , T. SchottAffiliated withDepartment of Arctic and Marine Biology, University of Tromsø
  • , S. B. HagenAffiliated withDepartment of Arctic and Marine Biology, University of TromsøBioforsk Soil and Environment, Svanhovd, Norwegian Institute for Agricultural and Environmental Research
  • , J. U. JepsenAffiliated withDepartment of Arctic and Marine Biology, University of TromsøNorwegian Institute for Nature Research, Fram Centre
  • , L. KapariAffiliated withDepartment of Arctic and Marine Biology, University of Tromsø
  • , R. A. ImsAffiliated withDepartment of Arctic and Marine Biology, University of Tromsø

Abstract

Two related issues in studies of biological invasions are how quickly the enemy complexes of invasive species become as species-rich and efficient as those of native species and how important enemy release is for the establishment and spread of invaders. We addressed these issues for the geometrid moths Operophtera brumata and Agriopis aurantiaria, who invaded the coastal mountain birch forest of northern Norway by range expansion approximately a century and 15 years ago, respectively. This was done by comparing larval parasitoid species richness and prevalence among the invaders and the native geometrid Epirrita autumnata. We found that E. autumnata and O. brumata both hosted seven parasitoid species groups, whereas A. aurantiaria hosted only one. Several parasitoid groups were shared between two or more of the geometrids. Total larval parasitism rates were similar in all three geometrid species, and comparison with published studies on larval parasitism in Western Europe suggested that O. brumata and A. aurantiaria do not suffer lower parasitism rates in our study region than in their native ranges. Our results indicate that accumulation of larval parasitoids on invasive geometrids in coastal mountain birch forest may reach completion within a few decades to at least a century after the invasion, and that establishment and spread of such invaders is unlikely to be facilitated by release from larval parasitism. Our investigations also uncovered a high degree of spatiotemporal synchrony between the total larval parasitism rates of O. brumata and A. aurantiaria, suggesting that larval parasitism of different geometrid species in the study system is governed by some common external factor.

Keywords

Agriopis Altitudinal gradient Enemy release Geometrid Invasion Parasitoid Range expansion