“…One consequence of the intraspecific release of mutator activity is that high levels of rare genetic variants observed in hybrid zones (Hunt and Selander, 1973;Avise and Smith, 1974;Kilpatrick and Zimmerman, 1976;Gould and Woodruff, 1978;Sage and Selander, 1979;Smith, 1979;Moran et a!., 1980;Greenbaum, 1981;Hafner, 1982;Peters, 1982;Barton et aL, 1983) may be due to increased rates of mutation (Woodruff et aL, 1979;Thompson and Woodruff, 1980), although intragenic recombination could also explain these variants (Golding and Strobeck, 1983). Support for increased rates of mutation as the cause of the increased genetic variation in hybrid zones comes from the observation that high frequencies of novel chromosome re-arrangements are observed in hybrid zones of grasshoppers and the re-arrangements are derived only from hybrid parents (Shaw et aL, 1983).…”