Hybridisation is associated with increased fecundity and size in invasive taxa: meta‐analytic support for the hybridisation‐invasion hypothesis

Abstract

The hypothesis that interspecific hybridisation promotes invasiveness has received much recent attention, but tests of the hypothesis can suffer from important limitations. Here, we provide the first systematic review of studies experimentally testing the hybridisation-invasion (H-I) hypothesis in plants, animals and fungi. We identified 72 hybrid systems for which hybridisation has been putatively associated with invasiveness, weediness or range expansion. Within this group, 15 systems (comprising 34 studies) experimentally tested performance of hybrids vs. their parental species and met our other criteria. Both phylogenetic and non-phylogenetic meta-analyses demonstrated that wild hybrids were significantly more fecund and larger than their parental taxa, but did not differ in survival. Resynthesised hybrids (which typically represent earlier generations than do wild hybrids) did not consistently differ from parental species in fecundity, survival or size. Using meta-regression, we found that fecundity increased (but survival decreased) with generation in resynthesised hybrids, suggesting that natural selection can play an important role in shaping hybrid performance – and thus invasiveness – over time. We conclude that the available evidence supports the H-I hypothesis, with the caveat that our results are clearly driven by tests in plants, which are more numerous than tests in animals and fungi.

Contemporary evolution and the dynamics of invasion in crop–wild hybrids with heritable variation for two weedy life–histories

“…). These results are consistent with the hypothesis that crop–wild hybrid biotypes have the potential to displace their wild parent in certain environments (Ellstrand and Schierenbeck ; Hovick and Whitney ).…”

“…; Hendry ; Whitney et al. ) and thus contribute to weedy population growth (Hovick and Whitney ). Therefore, gene flow between genetically distinct crops and sexually compatible weedy relatives may contribute to the evolution of more problematic weeds when gene flow alters phenotypic frequencies and the relative fitness of phenotypes within weed populations.…”

Five decades of invasion genetics

“…Elaborating on this hypothesis, Mark Kirkpatrick provided evidence for a new example in which massive range expansion in the mosquito (and malaria vector) Anopheles gambiae may have been triggered by capture of a cassette of adaptive alleles from the dry-climate adapted A. arabensis. Mixing of genetic material from divergent (but not too divergent) populations within a species can also improve performance, as was shown by Katrina Dlugosch (University of Arizona, These patterns match recent trends in the literature: both intraspecific and interspecific admixture are commonly associated with performance increases in invasive plants, animals, and fungi (see syntheses in Rius & Darling, 2014;Hovick & Whitney, 2014). However, a fundamental question is still up for grabs: how critical is such admixture for invasive success?…”

Lantana camara L. (sensu lato): an enigmatic complex

“…With time, many cultivars escaped cultivation, spread beyond the ornamental confines of the garden and became weeds (Spies 1984, Swarbrick 1985, Palmer and Pullen 1995. Studies have identified hybridization to contribute substantially to invasiveness, weediness and/or range expansion (Brown and Marshall 1981, Ellstrand and Schierenbeck 2000, Hovick and Whitney 2014. Likewise, innumerable intentional as well as unintentional hybridization events in Lantana led to remarkable increase in its complexity.…”