Asymmetry in fitness-related traits of later-generation hybrids between two invasive species

Premise: Most studies on the importance of hybridisation to invasions have focused on the comparison of fitness-related traits between F1 hybrids and their parents whilst different fitness landscapes could emerge in later generations after hybrids cross with each other (i.e. F2) or backcross with their parents.

Methods: In this study, artificial crosses were conducted to generate F1, F2 and backcrosses between two invasive species: Cakile edentula (self-compatible) and Cakile maritima (self-incompatible). Putative hybrids were also collected from the sympatric zone and compared with their co-occurring parents for phenotypic and genetic differences.

Results: Genetic data provided evidence of hybridisation happening in the wild and phenotypic comparisons showed that natural hybrids had intermediate traits between the two species but showed more similarity to C. maritima than to C. edentula. The asymmetry was further identified in artificial generations for several phenotypic charact...