Sex-specific variation in physiological and morphological features of the moss Ceratodon purpureus

Background/Question/Methods

Sexual dimorphism is widespread among plants. The two sexes often co-exist within an ecosystem, sharing phylogeny, geology, and ecology, allowing an examination of the functional significance of sexual dimorphism in plants. In bryophytes, sexual dimorphism is common, but little information is available on how physiological and morphological traits diverge between the sexes within and among populations. These data are critical to understanding how selection acts on sexual dimorphism in bryophytes, and whether sexual dimorphism is maintained by sexual selection (selection for mating success) or natural selection (selection for survival). Here, we assessed cellular, leaf, and canopy level traits in males and females of three Oregon populations of Ceratodon purpureus, a cosmopolitan moss species with separate sexes. Plants were collected from the field and grown in the greenhouse through the protonemal stage to reduce environmental bias.

Results/Conclusions

We found consistent sex-specific differences at the cellular and leaf level in all three populations of Ceratodon purpureus. Canopy level variation between the sexes fluctuated among populations. The most significant canopy differences between males and females were found in the genotype of C. purpureus originating from a rural location while less variance was observed between the sexes in the urban genotypes. Cellular and leaf structural differences could indicate differential resource acquisition and storage and are most likely genetically determined. These data suggest that the two sexes of this moss either do not respond uniformly to environmental stressors at the canopy level or possess population level differences in life-history traits. Advancing our understanding of plant form and function, these findings contribute a much needed base from which future sex-specific physiological research on bryophytes can continue. Ecologically, sex-specific research on bryophytes assists in our understanding of the adaptive response of these plants to environmental stressors which serves to elucidate vital preservation and restoration measures.