Differences in the sexual aposymbiotic phase of the reproductive cycles of Parmelina carporrhizans and P. quercina. Possible implications for their reproductive biology

Our knowledge of ontogenetic development and reproductive biology in lichen-forming fungi is rather poor. Here, we aim to advance our understanding of the reproductive biology of Parmelina carporrhizans and P. quercina for which mycobiont fungi of both species were cultured in aposymbiotic conditions from ascospores. For P. carporrhizans 48 hours were necessary for 98·6% of apothecia to eject spores, while for P. quercina 100% of apothecia ejected spores in the first 24 hours. In P. quercina, large apothecia ejected more spores than smaller ones. In both species the percentage of spores germinating seemed independent of apothecium size. The percentage germination was higher in P. carporrhizans (72·4%) than in P. quercina (14·3%). Moreover, P. carporrhizans was grown more successfully on culture media than P. quercina. These results suggest that these species have different reproductive strategies, given that P. carporrhizans expels larger spores and in greater numbers than P. quercina as well as having different nutritional requirements (since P. carporrhizans grew successfully in the selected media but P. quercina did not). These characteristics may explain the sympatric speciation of these species.