Comparative Patterns of Sex Expression and Sex Ratios in Island and Continental Bryophyte Populations

Reproductive biology patterns are crucial for understanding the dynamics and evolution of plants. This is particularly relevant in bryophytes, where sex expression and reproductive success can vary significantly with environmental conditions. Islands, with their isolated and diverse environments, provide natural laboratories to explore these dynamics. In this study, we investigate sex expression, the phenotypic sex ratio, and sporophyte production in one moss (Exsertotheca intermedia) and three liverwort species (Frullania polysticta, Frullania teneriffae, Porella canariensis) across their entire distribution range. Depending on the species, the geographic range includes the Canary Islands, Madeira, the Azores, the Iberian Peninsula, the British Isles, and the Faroe Islands. For the non-Macaronesian endemic species (F. teneriffae, P. canariensis) higher levels of sex expression and males were found in the Macaronesian archipelagos. In leafy liverworts, females appear to be correlated with lower temperatures and higher precipitation levels, while males seem to be associated with higher temperatures and relatively lower precipitation levels. In this study, we demonstrated that bryophyte populations from Macaronesia exhibited higher levels of sex expression compared to their continental counterparts, suggesting that the distinct environmental conditions of these islands play a crucial role in shaping their reproductive patterns.