A clue to invasion success: genetic diversity quickly rebounds after introduction bottlenecks

Peter Kaňuch,Anna Cassel-Lundhagen,Åsa Berggren

doi:10.1007/s10530-020-02426-y

Abstract

One of the fundamental questions in invasion biology is to understand the genetic mechanisms behind success or failure during the establishment of a species. However, major limitations to understanding are usually a lack of spatiotemporal population data and information on the populations’ colonisation history. In a large-scale, detailed study on the bush-cricket Metrioptera roeselii 70 groups of founders were introduced in areas outside the species’ distribution range. We examined how (1) the number of founders (2–32 individuals), (2) the time since establishment (7 or 15 years after introduction) and (3) possible gene flow affected establishment success and temporal genetic changes of the introduced populations. We found higher establishment success in introductions with larger propagule sizes but genetic diversity indices were only partly correlated to propagule size. As expected, introduced populations were more similar to their founder population the larger the propagule size was. However, even if apparent at first, most of the differentiation in the small propagule introductions disappeared over time. Surprisingly, genetic variability was regained to a level comparable to the large and outbreeding founder population only 15 generations after severe demographic bottlenecks. We suggest that the establishment of these populations could be a result of several mechanisms acting in synergy. Here, rapid increase in genetic diversity of few introductions could potentially be attributed to limited gene flow from adjacent populations, behavioural adaptations and/or even increased mutation rate. We present unique insights into genetic processes that point towards traits that are important for understanding species’ invasiveness.

Highlights

With expanding trade routes, species are given additional ways to colonise new areas
A clue to invasion success: genetic diversity quickly rebounds propagule sizes and there were no systematic differences across the study area (Fig. 1)
We found lower genetic diversity (AR and unbiased HE) in most examined introductions 7 years after introduction compared to the founder population (Fig. 2a, b)

Summary

Introduction

Species are given additional ways to colonise new areas. The likelihood of establishment is expected to increase if the species possesses traits that enable it to cope with novel environments and to overcome negative effects arising from low number of individuals at the initial stage (Puillandre et al 2008; Blackburn et al 2009). Such traits may, for example, be the ability of individuals to adjust their behaviour by increasing their movement to compensate for the effects of few close-mating opportunities (Kindvall et al 1998; Wissmann et al 2009). In spite of a suitable environment and biological traits, establishment may still fail due to genetic factors such as lack of adaptive genetic variation in the arriving individuals (Lee 2002; Puillandre et al 2008; Lawson Handley et al 2011), or fitness consequences from inbreeding depression (Fowler and Whitlock 1999; Ayroles et al 2009)

Objectives

Methods

Results

Discussion

Conclusion