Are exotic species red queens?

Abstract

We combined two general hypotheses from the fields of invasion biology and evolutionary biology, the enemy release hypothesis and the Red Queen hypothesis, into the new invasive queens hypothesis. This hypothesis predicts that if species with the principal ability to reproduce both sexually and asexually are introduced to an exotic range, they show a shift towards asexual reproduction in the exotic range. The reasoning behind this hypothesis is that (1) species tend to leave behind their natural enemies when being introduced to an exotic range (enemy release hypothesis) and (2) sexual reproduction is less advantageous in the absence of natural enemies due to its high costs (inverted Red Queen hypothesis). We tested the invasive queens hypothesis against data from 70 animal species, based on information from the literature and unpublished information provided by 105 experts from various continents. As predicted, the investigated species showed a significant shift towards asexual reproduction in their exotic as compared to their native range.

KEY WORDS:

• Baker’s rule
• biological invasions
• enemy release hypothesis
• William D. Hamilton
• invasive alien species
• invasive queens hypothesis
• non-native species
• Red Queen hypothesis

ACKNOWLEDGEMENTS

We would like to warmly thank Francesca Gherardi for her great contributions to the field of invasion biology. J.M. Jeschke first met Francesca a decade ago when he started to work on this topic. Since then, they repeatedly met over the years, either in the US or in Europe, always having a good time and talking about science or other things. The scientific conversations often focused on concepts and hypotheses in invasion biology (see also Heger et al. 2013), which is why we have chosen this manuscript as a contribution to this special issue. We thank Piero Genovesi and David Holdich for inviting us to contribute to this issue, and we will always keep Francesca in the best memories. Concerning the invasive queens hypothesis, Manfred Milinski talked to J.M. Jeschke in May 2008 about invasive species and mentioned an idea by the late William D. Hamilton that he described in one of his last talks. Since we heard about this idea, we further developed it and named it the invasive queens hypothesis, as described here. Unfortunately, we do not have a transcript of Hamilton’s talk in which he outlined the idea, so we do not know if he referred to another researcher, but he might be the intellectual father of the invasive queens hypothesis for which we warmly thank him. We are also very grateful to Manfred Milinski for mentioning the idea to us. Furthermore, we highly appreciate the input by 105 experts without whom this study would not have been possible (their names are given in Online Appendix A). The Deutsche Forschungsgemeinschaft provided financial support (JE 288/4-1).