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

• Published in: Biological invasions 2013-07, Vol.15 (7), p.1573-1589
• Main Authors: Vindstad, O. P. L., Schott, T., Hagen, S. B., Jepsen, J. U., Kapari, L., Ims, R. A.
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Biomedical and Life Sciences; Birch trees; Comparative studies; Conservation, protection and management of environment and wildlife; Developmental Biology; Ecology; Ecology: 488; Epirrita autumnata; Forestry; Forests; Freshwater & Marine Ecology; Fundamental and applied biological sciences. Psychology; General aspects; General forest ecology; Generalities. Production, biomass. Quality of wood and forest products. General forest ecology; Indigenous species; Invasive species; Life Sciences; Matematikk og Naturvitenskap: 400; Mathematics and natural science: 400; Mountain forests; Original Paper; Parasites; Parasitism; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking; Plant Sciences; Species richness; VDP; Zoologiske og botaniske fag: 480; Zoology and botany: 480; Økologi: 488
• ISSN: 1387-3547; 1573-1464
• DOI: 10.1007/s10530-012-0393-8

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.