Parasite Release and Biological Invasions

The loss of genetic diversity due to population bottlenecks during invasion can reduce the fitness of introduced species. Despite this, introduced species often perform better in their introduced range. This conundrum, referred to as the genetic paradox of biological invasions, remains unanswered despite extensive research over the past decades. In this chapter, we propose that parasite release could provide a clue to disentangling the paradox. Along with reducing genetic diversity, population bottlenecks also serve to reduce co-invasion of parasites, resulting in parasite release among introduced populations. Across 27 taxonomically diverse animal species, we found a positive correlation between genetic diversity loss and parasite release. Since these two factors can affect the survival, fecundity and growth in opposing directions, the observed correlation indicates that parasite release could potentially compensate for the negative effects of genetic depletions in the introduced species. We, therefore, posit that parasite release provides an additional explanation for the genetic paradox of biological invasions.