Fig. 1

The mean proportion of non-ecological reproductive barriers of Daphnia across the four main cross categories: conspecific Daphnia pulex (px x px) and Daphnia pulicaria (pc x pc), and heterospecific D. pulex female x D. pulicaria male (px x pc) and the reciprocal cross D. pulicaria female x D. pulex male (pc x px). Shown in the panels are (a) mating-fertilization success, b F1 zygotic mortality, c F1 hatching success, and d F1 survivorship. Vertical bars are (±) standard errors. Asterisks (*) show significance (p < 0.05) between the different groups (shown in bars) based on a post-hoc Tukey test