We are only beginning to gain insight into the importance of genetic variation to the long-term success of clonal populations. In some species of seagrass (Z. marina), there appears to be a strong relationship between genetic diversity and plant vigor (Williams, 2001), while others maintain vast sexual populations that have almost no detectable genetic variation (Am-phibolis antarctica; Waycott et al., 1996; Waycott et al., Chapter 2). Understanding the role of seeds in the long-term dynamics of seagrass populations has taken on an extra sense of urgency with predictions of present and future global change (Short andNeck-les, 1999; Ferriere et al., 2000; Twilley et al., 2001; Scavia et al., 2002; Johnson et al., 2003; Kenwor-thy et al., Chapter 25) and with the fragmentation of habitats into isolated patches that theoretically could result in lower overall seed sets (Reusch, 2003). The emerging importance of seeds to the long-term dynamics of seagrass populations, and perhaps even more importantly in creating new patches distant from parent stock or in the recolonization of disturbed areas rather than maintaining existing, well-established beds (Olesen, 1999; Olesen et al., 2004), means that scientists and managers must place greater emphasis on conserving existing beds to provide a seed bank, and possibly in exploring ways to use seeds to restore areas that may have lost seagrass and are far away from potential seed sources.
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