Are exotic species red queens?

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tested the invasive queens hypothesis against data from 70 animal species, based on information from the literature and unpublished information provided by 105 experts from various continents.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.