RESEARCH ARTICLE s

Full list of author information is available at the end of the articleHybridization between species is a relatively common phenomenon that has been well documented in both animals [1] and plants [2] and may play an important role in the process of speciation. In plants, hybridization has been hypothesized to be especially extensive, and it has recently been shown that in plant families with two or more species, nearly half of those surveyed were found to have hybrids (48.5 %, [2]). Ultimately, the pend on the nature of the reproductive barriers that act to reduce gene flow between the hybridizing species pairs; the rate of F1 hybrid formation will be directly affected by the number (and strength) of pre-zygotic iso-lating barriers, while post-zygotic isolating barriers will act directly on F1 and later-generation hybrids to further reduce the likelihood of gene flow. Normally, a combin-ation of pre- and post-zygotic isolating barriers act in concert to affect the total isolation observed between taxa [3,4]. However, even in cases where the total isola-tion measured is near-complete (e.g. F hybridization * Correspondence