“…Under temperate conditions, usual in the Mediterranean basin, parthenogenetic diploid brine shrimp strains show physiological responses and demographic traits theoretically superior when facing competition with Mediterranean and Old World bisexual species (Amat 1983;Browne and Halanych Browne, 1989;Browne, 1992;Barata et al, 1996;Browne and Wanigasekera, 2000). But whilst in general, parthenogenetic reproduction associates to very effective and rapid dispersal and colonization mechanisms, the real picture shows the American bisexual A. franciscana going beyond its original range and reaching the Old World, spreading from western to eastern (Van Stappen et al, 2007) geographical extremes. Under the same climatic conditions prevailing in the Mediterranean area, this allochthonous species has been able to develop improved physiological responses and demographic traits in comparison to bisexual and parthenogenetic native species and strains, as several authors have experimentally demonstrated (Varó et al, 2000;Sarabia et al, 2002;Browne and Wanigasekera, 2000;Browne et al, 2002;Amat et al, 2007), ultimately becoming an invasive NIS.…”