Soil seed bank and among-years genetic diversity in arid populations of Eruca sativa Miller (Brassicaceae)

Populations of Eruca sativa from arid environments exhibit greater physiological dormancy than those that originated in more favorable ones. We tested the possible relative contribution of the soil seed bank (SSB) to the aboveground cohorts in desert and semiarid populations. Seedlings that emerged from the SSB under controlled irrigation were distinguished from those that emerged after exposure of the remaining ungerminated SSB to gibberellic acid as constituting non-dormant and dormant SSBs, respectively. On average, the total SSB was significantly larger in the semiarid than in the desert population. In both sites, the aboveground and SSB cohorts exhibited closely similar genetic diversity, and in the aboveground cohorts similar year-to-year genetic diversity was found. These results indicate continuous recruitment from the SSB to the aboveground cohorts. Nevertheless, Ne estimates indicated that the SSB can contribute to enlarging the aboveground effective populations in both habitats. Furthermore, Nei's genetic distances suggested that the non-dormant SSB contributed more than the dormant SSB to the aboveground cohorts. These results highlight the potential of the SSB to maintain a genotype reservoir that protects annual populations in arid environments. (C) 2013 Elsevier Ltd. All rights reserved.