Gametophyte and sporophyte morphology are phylogenetically correlated in mosses, indicating coadaptation and parent–offspring conflict

Parent-offspring relationships present a paradox wherein parents must balance limited resources between provisioning their offspring to increase their chances of survival and maturation, and reserving resources for their own survival and future reproduction. Bryophytes provide a unique system to explore this relationship due to the dependency of sporophytes on parental gametophytes throughout their lifespan. We investigate the morphological evolution of gametophyte and sporophyte characters to test for evidence of coadaptation in the Dicranaceae Schimp. and Grimmiaceae Arn. We also examine these morphological features in Grimmiaceae species with different sexual systems to test for higher levels of parent-offspring conflict in species that are exclusively outcrossing. Our study is the first to test this prediction with empirical data. Our study reveals significant correlations between parental gametophyte and offspring sporophyte morphology, which provides evidence of coadaptation. We found that species with unisexual gametophytes have larger calyptrae, which may decrease offspring resource acquisition, as well as larger capsules and larger setae, which may increase resource acquisition, than species with bisexual gametophytes. These findings suggest that the sexual system influences the relationship between gametophyte and sporophyte morphology, indicating higher levels of parent-offspring conflict in outcrossing species.