we now include new citations in relationship to different problems: Butlin et al. (2009), Cohan (2011), Cohan (2013), Cohan & Aracena (2012), Diekmann et al. (2004), Nosil (2012), Vos (2011), Wiedenbeck & Cohan (2011).
Given that both reviewers commented on this issue, we tried to clarify our aims and included a sentence at the end of the introduction, in order to clarify the point.