Scapania undulata is an aquatic dioicous liverwort growing in shallow streams in boreal to subtropical zones. We studied the expressed sex ratio, sex-specific differences in shoot architecture and possible trade-off between sexual and asexual reproduction in ten populations of S. undulata by surveying 100 plots in ten streams in southern Finland. The expressed sex ratio was male biased, in contrast with the sex ratio in most dioicous bryophytes. It was also highly variable between the streams, but individual plots frequently comprised shoots from only one sex. The overproduction of males might be a strategy to overcome sperm dilution and ensure fertilization over longer distances in water. No size differences between females and males were detected, but they differed in branching patterns. Evidence for a higher cost of sexual reproduction in females than males can be seen from the following: the male-biased sex ratio; low number of sex-expressing female shoots in female-only plots; no co-occurrence of gemmae and female sex organs on a single branch, and no more than one sexual branch per female shoot. In contrast, high gemma production of male and female sex-expressing shoots indicates a minimal trade-off between sexual and asexual reproduction.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.