EGG DIAPAUSE AND CLONAL STRUCTURE IN PARTHENOGENETIC POPULATIONS OF HETEROCYPRIS INCONGRUENS (OSTRACODA)

A study of the clonal structure of parthenogenetic populations of Hete rocypris incongruens from rice-fields in Northern Italy carried out ov er two-year period is summarized. Significantly different levels of ge netic polymorphism were found among populations. The coexistence of di fferent electrophoretic clones and similar patterns of clonal seasonal succession have been observed in at least two different rice fields. The clone or group of clones present in fall, winter and early spring is substituted by other multilocus genotypes in late spring and summer . Different egg diapause induction mechanisms drive the clonal substit ution in different clones. Here we report a new laboratory experiment designed to test the effect of temperature and photoperiod found in wi nter (12 degrees C 8:16 L:D), spring (24 degrees C 12:12 L:D) and summ er (28 degrees C 16:8 L:D) conditions on the deposition and hatching o f diapausal eggs in different multilocus genotypes. Clones respond in a way compatible with their sustained presence in the field in differe nt seasons.