Location: Biological Control of Pests ResearchTitle: Inferring the origin of populations introduced from a genetically structured native range by approximate Bayesian computation: case study of the invasive ladybird Harmonia axyridis) Author
|Lawson Handley, Lori|
|Van Lenteren, Joop|
Submitted to: Molecular Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2011
Publication Date: N/A
Citation: N/A Interpretive Summary: New envasive pests costs countries billions of dollars annually. The management technique of choice is classical biological control, in which the area of pest origin is identified, and key natural enemies are collected and studied for possible release in the invaded area to permanently reduce impact. But often the native area is unknown or mistakenly identified. New techniques like molecular biology have greatly improved the ability to match exotic organisms to their original counterparts, but have limitations. Using a combination of population genetic statistics and simulated modeling to determine the native area of the envasive Asian Multicolored Ladybeetle. It was found that there is both an east and west Asian source of envasive beetle populations. The U.S. population come from both Asian areas, and that this mixture probably helped the insect to invade other continents such as Europe and Africa.
Technical Abstract: The correct identification of the source population of an invasive species is a prerequisite for defining and testing different hypotheses concerning the environmental and evolutionary factors responsible for biological invasions. The native area of invasive species may be large, barely known and/or genetically structured. As a consequence, studies relying on molecular markers may reach wrong conclusions about the origin of introduced populations because the actual source population may not have been sampled. In this study, we first characterized the genetic structure of the invasive ladybird Harmonia axyridis (HA) in its native area by using Bayesian clustering methods as well as more classical population genetic statistics and methods (e.g. FST and Neighbor-joining trees). Our analyses inferred a genetic structure of HA native area consisting of two distinct geographic clusters with (i) Kazakhstan and central Siberia in the West and (ii) China, Korea and Japan in the East. We then performed approximate Bayesian computation (ABC) analyses on controlled simulated microsatellite data sets to evaluate: (i) the risk of selecting incorrect introduction scenarios, including admixture between sources, when the native area is genetically structured, and sampling is incomplete, (ii) the ability of ABC analysis to minimize such a risk by explicitly including unsampled populations in the compared scenarios. Finally, we performed new ABC analyses on real microsatellite data sets to retrace the origin of biocontrol and invasive populations of HA, taking into account the possibility that the structured native area may have been incompletely sampled. We found that the Eastern North American invasive population, which is the bridgehead of the worldwide invasion of HA, was probably formed by an admixture between the native Eastern and Western clusters with an approximately equal genetic contribution of both. This admixture may have facilitated adaptation of the bridgehead population, and therefore has important implications for understanding invasion success of HA.