The frequency with which bryophytes transition between sexual states is unmatched by their vascular plant relatives. Yet, the ecological and evolutionary mechanisms that drive the evolution of separate and combined sexes in mosses remain somewhat obscure. Here, we re-evaluate the evolutionary ecology of sex in mosses. To do so, we use the largest sexual state database of mosses to date, the most comprehensive species-level phylogeny of mosses, and a massive geographic database to uncover the patterns and processes governing moss reproduction. We employed Hidden-State Speciation and Extinction analysis (HiSSE) to uncover the ancestral sexual state in mosses, and to test the expectation that monoicous lineages have higher rates of diversification. We then used ancestral state reconstructions of moss chromosome numbers to test the hypothesis that increases in chromosome number coincide with transitions to monoicy. We used generalized dissimilarity modelling to determine the ecological drivers of turnover in moss communities partitioned by sexual state. Finally, we test the long-held hypothesis that monoicous lineages have larger ranges as a consequence of long-distance dispersal by spores. We found that the ancestral state in mosses is dioicy, as demonstrated by previous studies. We also verify using the most modern techniques that monoicy is associated with higher rate of diversification, but our results suggest a much higher value than those previously reported in mosses. Most importantly, we demonstrate that monoicous lineages do not have larger range sizes, but instead have smaller ranges with low range overlap between closely related species. We interpret this as a phenomenon in which monoicous species likely experience a ‘sweet-spot’ in the frequency of long-distance dispersal of spores. Here, LDD contributes to the formation of nascent selfing populations, but is insufficient to maintain gene flow between daughter and parent populations, resulting in many incipient lineages that diverge allopatrically.