Lack of enemy release for an invasive leafroller in California: temporal patterns and influence of host plant origin

The enemy release hypothesis posits that the success of invasive species can be attributed to their escape from natural enemies. Invading hosts are expected to encounter an enemy assemblage consisting of fewer species, with lower representation of specialists, and to experience less mortality as a r...

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Bibliographic Details
Published in:Biological invasions 2014-05, Vol.16 (5), p.1021-1034
Main Authors: Bürgi, Linda P., Mills, Nicholas J.
Format: Article
Language:English
Subjects:
Animal, plant and microbial ecology
Applied ecology
Biological and medical sciences
Biomedical and Life Sciences
Braconidae
Conservation, protection and management of environment and wildlife
Developmental Biology
Ecology
Epiphyas postvittana
Flowers & plants
Freshwater & Marine Ecology
Fundamental and applied biological sciences. Psychology
General aspects
Ichneumonidae
Life Sciences
Malus
Meteorus
Original Paper
Parasitic diseases
Parks, reserves, wildlife conservation. Endangered species: population survey and restocking
Plant diseases
Plant Sciences
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Summary:The enemy release hypothesis posits that the success of invasive species can be attributed to their escape from natural enemies. Invading hosts are expected to encounter an enemy assemblage consisting of fewer species, with lower representation of specialists, and to experience less mortality as a result. In this study, we examined parasitism of the Light Brown Apple Moth (LBAM), Epiphyas postvittana (Walker), in California, an exotic leafroller that is native to southeastern Australia. From 2008 to 2011 we monitored parasitoid species richness, representation of the more specialized koinobiont parasitoids, and parasitism rates of LBAM collected three times per year from four plant species of Australian origin and six plant species of non-Australian origin, at two locations in coastal California. We found the resident parasitoid assemblage of LBAM in California to have comparable levels of species richness, to have a similar representation of koinobionts versus idiobionts, and to inflict similar parasitism rates as in its native range. The two dominant parasitoids were Meteorus ictericus (Braconidae) and Enytus eureka (Ichneumonidae). Parasitoid species richness varied with season and plant origin and decreased slowly, but significantly, over the 4 year period. Parasitism rates were lowest in spring and highest on plants of Australian origin, but did not change with year. Hyperparasitism rates were higher on E. eureka (36.5 %) compared with M. ictericus and other parasitoids combined (3.3 %) and were highest on plants of Australian origin. We subsequently discuss the lack of both apparent enemy reduction and realized enemy release for LBAM in California and the unique finding that a shared plant origin enhanced the parasitism of this exotic leafroller by resident parasitoids.
ISSN:1387-3547
1573-1464
DOI:10.1007/s10530-013-0554-4