Genetics helps reveal invasion histories

(Text modified from Press Release from NIMBioS)

New tool could help in controlling biological invasions, such as the emerald ash borer, the Asian beetle which is now advancing on the East Coast after having wiped out up to 80 percent of ash trees in the Midwest. USDA

Asian carp. Hemlock woolly adelgid. Destructive pests that raise the hackles of fisherman, farmers, and wildlife managers everywhere they invade.

But how do they establish themselves and take over non-native species so effectively and efficiently?  Specifically, what is happening early on in invasions, before we take notice of them?

Knowing answers to these questions could help experts manage and control invasive species.  And genetic data from invasives can help reveal the answers.

In research from the National Institute for Mathematical and Biological Synthesis (NIMBioS) and the University of Ferrara, Italy, scientists have devised a new method for investigating the factors that contribute to biological invasions of non-native species.

In the new study, published in the journal Heredity, researchers used genetic data to analyze multiple waves of a single biological invasion. Tested on simulated data across a large range of realistic invasive situations, the study’s method was able to successfully use genetic data to correctly distinguish a two-wave invasion from a single-wave invasion. The method also correctly estimated the number of individuals that were introduced, and to some degree, the timing of introductions.  These are key variables of the early process of invasions that would be hard to know without genetic data, because invasions start small and sometimes take a long time to really get going.

Understanding these factors could advance ecological understanding of biological invasions, such as why many non-natives take a long time before rapidly increasing. Being able to differentiate between waves could also help in the management and control of them.  “Knowledge of whether second, or even third or fourth waves occurred in invading populations can help us better understand the dynamics of invasions. If second waves are common, managers could use this information to decide whether, how and when to isolate or eliminate small introduced populations,” said corresponding author and NIMBioS postdoctoral fellow Sean Hoban.

Prior to this work, some researchers had suggested it might not be possible to distinguish multiple waves from a single source. This study—the first to examine this type of invasion— shows otherwise.

In addition, the results have implications for plant and animal product inspection and interception of non-native species. According to the research, strict inspection could be important to continue even after first establishment to prevent further waves. For example, recent public messages from the Great Smoky Mountains National Park aim to prevent further waves of establishment of emerald ash borer by prohibiting people from bringing firewood into the park from outside.

In general, the authors emphasize that their approach could benefit much future invasive species work.

Citation: Benazzo A, Ghirotto S, Torres Vilaca ST, Hoban S. 2015. Using ABC and microsatellite data to detect multiple introductions of invasive species from a single source. Heredity. [Online]

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