2.2 Sex ratio investigation
To reveal the geographical distribution of parthenogenetic
(female-dominant) and sexual populations of S. lomentaria , sex
ratios of the 38 populations (localities; Table 1) were investigated.
Sex of S. lomentaria gametophytes, which is morphologically
indistinguishable, was identified by sex-check PCR and/or crossing
experiments. In the sex-check PCR, partial sequences of the sex-specific
non-recombining region on the sex chromosome (female U chromosome and
male V chromosome) of S. lomentaria were used as sex markers and
were amplified as in Hoshino et al. (2019). The sex of each samples was
confirmed by the presence/absence of PCR products in 1% agarose-gel
electrophoresis. In the crossing experiments, gametes of each sample
were crossed with male and female gametes from sexual populations using
culture strains following the methods outlined in Hoshino et al. (2018).