Novel seed protection in the recently evolved invasive, California wild radish, a hybrid Raphanus sp. (Brassicaceae)

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Interspecific hybridization may have considerable effects on plant structural defenses that can contribute to the success of invasive hybrid lineages. Changes in fruit structural and material properties are predicted to have key effects on predispersal granivory.•

Here, we asked whether plant structure can increase the fitness of a hybrid invasive relative to its progenitors. We compared fruit traits of the hybrid-derived lineage, California wild radish, with its progenitors, cultivated radish and jointed charlock.•

The hybrid lineage is significantly different from one or both ancestors in fruit length, mass, diameter, volume, shape, wall strength, and internal seed distribution. We experimentally exposed the fruits of both hybrid and wild progenitor to avian granivores and found (1) different types and degrees of damage at the different fruit sections and (2) significant differences in the inflicted damage at different sections of the fruit.•

Combining our descriptive and experimental data, we conclude that the novel seed protection of the hybrid California wild radish is an important defense mechanism. It offers differential protection to its seeds and according to our findings, better protection of seeds that have been found to be better competitors. We suggest then that the fruit has enabled, at least in part, the successful replacement of the parental species by the hybrid lineage.