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 characters. Furthermore, backcrosses exhibited different pattern of variation, with backcrosses to C. maritima having high reproductive output than their counterparts.

Conclusions: Our study suggests that hybridisation and introgression (backcrossing) in Cakile species is asymmetric and most likely to favour the proliferation of C. maritima genes in the mixed population and thus help its establishment, a finding that could not be predicted by characterizing F1 hybrids.

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 for phenotypic charcters at two stages (harvest 1 and 2) in a common garden experiments. Data include measurments of various traits on individual plants. 

Data files for phenotypic traits recorded and comparisons between different plant populations/families in "Asymmetry in fitness-related traits of later-generation hybrids between two invasive species"

For the first common garden experiment, there were two rounds of experiments, i.e., early stages (harvest1) and late stages (harvest2):

Harvest1

-Original data file for the phenotypic traits recorded in the first round of the first common experiment. Details about units and abbreviations can be found in TABLE 1 of the associated paper.

Harvest2

-Original data file for the phenotypic traits recorded in the second round of the first common experiment. Details about units and abbreviations can be found in TABLE 2 of the associated paper.

pca_eign_hyb_harvest1

- PCA eign values for “Harvest1”, as present in Figure 4A.

pca_eign_hyb_harvest2

- PCA eign values for “Harvest2”, as present in Figure 4B.

pca_scores_hyb_harvest1

-PCA scores for “Harvest1”

pca_scores_hyb_harvest2

-PCA scores for “Harvest2”

For the second common garden experiment about artificially produced hybrids and their parental species, the following file is available:

Chengjun_Experiment

-Original data file for the phenotypic traits recorded in the second common experiment. Details about units and abbreviations can be found in APPENDIX S2 “Traits measured in the first and second common garden experiments”.