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depending on w hether phenotypes are beneficial or deleterious, or even to develop new life
attributes a nd s trategy. For e xample, in N orth A merica, p ollinator-mediated s election h as
been f ound t o be acting on f loral t raits s uch as s tamen di morphism, a nther e xertion, a nd
flower size of wild radish (Conner et al. 1996; 2003).
Wild radish (Raphanus raphanisrum, RrRr, 2n=18) is a member of the Brassicaceae, a
family o f w orld-wide d istribution. It is a s elf-incompatible, a nnual t o bi ennial br oadleaved
species, growing on de ep and rather low-pH soils. Wild radish has successfully colonized a
variety of locations, leading to its naturalization on all continents except Antarctica (Holm et
al. 1997) , a nd i t is o ften a m ajor a gricultural weed (Sahli e t a l. 20 08). S tudies on t he
geographic di stribution of t he genetic va riability and m orphological t raits ha ve s hown t hat
divergences among wild radish populations did not correspond to a geographic pattern due to
distance (Tokunga and Ohnishi 1992; Kercher and Conner 1996; Sahli et al. 2008). Kercher
and C onner (1996) h ave t entatively ex plained th is b y: (1) th e s elf-incompatibility o f w ild
radish that promoted gene flow, (2) the long-distance movement of radish seeds, and (3) the
introgression from the cultivated radish (R. sativus).
There are some evidences that the long-term introgression from cultivated radish to
wild radish has caused concerns on morphology and reproduction divergences of introgressed
descendants (Kercher and Conner 1996; Snow et al. 2001; Campbell et al. 2006; Hedge et al.
2006). Campbell e t a l. ( 2006) s howed t hat h ybrid r adish popul ations after c rop gene
introgression ha d greater f ecundity a nd s urvival t han w ild popul ations, w hich c ould
eventually l ead t o t he replacement of their p arents if th e introgression succeeded. Using
morphological a nd allozyme e vidences, Hedge e t a l. (2006) found t hat h ybrids-derived
descendants supplanted t he t wo l ocal Raphanus species i n C alifornia, suggesting t he
aggressive colonizing behavior of the hybrids, and that California wild radish separated from
both of its parents as an evolutionary entity. The flowering phenology and leaf length of these
plants were intermediate between those of the wild and cultivated radishes (Hedge et al. 2006),
indicating introgression-caused morphology divergence.
In t his s tudy, w e w onder i f h ybridization of w ild r adish w ith oi lseed r ape, Brassica
napus, c ould r esult i n l ong t erm i ntrogression a nd m orphological di vergence. S pontaneous
hybridization b etween t hese t wo s pecies w as demonstrated t o o ccur at l ow f requency
(Darmency et al. 1998; Chèvre et al. 2000) although it success could depends on the genotype
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