“…(2012) suggested that WEM was possibly a “hybrid swarm.” One of those features is the observation of increased fitness that should allow for ecological success to translate into evolutionary success (see, e.g., Pereira et al., 2014 for a marine example)—which could reflect adaptive introgression promoting the maintenance of hybrids (Hedrick, 2013; Martin, Bouck, & Arnold, 2006). Patterns of survival of the WEM × WEM cross go against high fitness of these “hybrids.” Adaptive introgression patterns or “swarming” at the center of the distribution of parental forms seems relatively common in other fish species (e.g., Machado‐Schiaffino, Juanes, & Garcia‐Vazquez, 2010; Roques, Sévigny, & Bernatchez, 2001; Sinama et al., 2013; Stemshorn, Reed, Nolte, & Tautz, 2011; Walters et al., 2008). However, while those studies described hybridization patterns using molecular markers, we are not aware of studies that reported fitness differences as carried out for WEM in the present study.…”