AQUATIC TRANSITIONS AND INTERSPECIFIC RELATIONSHIPS IN FISSIDENS MOSSES

Embryophytes have undergone numerous re-invasions to aquatic habitats, impacting their morphological evolution. Despite the prominence of these transitions, their phylogenetic implications and morphological adaptations are just beginning to be investigated, especially as molecular methodologies become more accessible. We investigate these phenomena using the genus Fissidens, a diverse group of mosses encompassing both terrestrial and aquatic species. Our study integrates phylogenetic methods with morphological analyses to elucidate the evolutionary patterns within Fissidens and explore correlations between habitat transitions and morphological traits. Through extensive taxon sampling from herbarium specimens, DNA extraction, and sequencing, we construct robust phylogenetic trees using concatenated and coalescence methods. Our results reveal the non-monophyly of historically defined subgroups within the genus Fissidens, challenging prior classifications. Furthermore, ancestral state reconstructions suggest there have been multiple independent transitions to aquatic environments within the genus. Morphological analyses indicate that although variations in leaf length correlated with habitat moisture, phylogenetic relatedness diminishes this correlation. These findings better our understanding of the complexity of evolutionary transitions in embryophytes and emphasizes the need for further studies to refine taxonomic classifications and better understand morphological changes in response to ecological shifts. This study contributes to wider discussions on the evolutionary dynamics of aquatic transitions in both bryophytes and, more broadly, embryophytes and their ecological significance.