Sexual reproduction in Daphnia: interspecific differences in a hybrid species complex

摘要: To investigate whether reproductive variation in the Daphnia galeata-cucullata-hyalina hybrid species complex can explain occurrence of hybrids and backcrosses, a total 43 clones from three north German lakes were tested for allocation to sexual reproduction under equal stress conditions. Six replicates per clone followed until seventh adult instar. I used following cues promote reproduction: short photoperiod, water crowded culture, fish-conditioned low food concentration. For each animal, clutch size sex recorded. Ephippia, which empty since animals cultured individually, only produced by D. cucullata x hyalina (26% 6% broods, respectively), whereas almost all taxa males (the range was 2–15%). Intraspecific male ephippial production also found. The fact that show different responses stimuli of-fered may indicate there is isolation between them. This supported field data Tjeukemeer (The Netherlands) shows galeata mostly produces ephippia spring autumn. presence with both seasons, however, backcrossing possible.