Two populations of Tisbe bulbisetosa from brackish environments were examined, the first from the mouth of the port-entrance of Grado, the second from a more inward position, from the Scardovari embayment on the Po delta. Comparisons were made with a third population from Malamocco, in the lagoon of Venice, which was studied in a previous work. The three localities differed in terms of chemical and physical parameters, and in the composition of benthic communities. The mean nauplius to adult survival of outcrossed invididuals differs in the three populations, the value being highest in Malamocco and lowest in Scardovari. Concealed genetic variability was calculated from estimates of the genetic load (number of lethal equivalents) based on depression of survival with progressive inbreeeding; the highest values were found in the population of Grado, the lowest in that of Scardovari. These data suggest there is a relationship between environmental stability, biological heterogeneity, and the genetic variability of T. bulbisetosa as determined by the number of lethal equivalents.
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Con il contributo del Ministero per i Beni e le Attività Culturali