| In this study coevolution between the Ascomycetous lichen fungi in section Cladonia and its chlorophyte algal partner Trebouxia was evaluated by comparing phylogenetic trees of each symbiont. Phylogenetic trees were produced from the internal transcribed spacer (ITS) regions and the 5.8S nuclear ribosomal DNA (rDNA) sequences in algal and fungal partners of 17 species of Cladonia section Cladonia and 21 others. These sequences were obtained using primers designed in conserved regions flanking the ITS regions that are specific to each of the fungal or algal rDNA.; Results revealed that fungal species complexes were polyphyletic. Four Trebouxia species (T. glomerata, T. pyriformis, T. magna and T. erici) are associated with lichens of genus Cladonia in Manitoba. There was no evidence of cospeciation in section Cladonia. However an isolated event of cospeciation was observed in Cladonia section Cladonia (in C. macrophyllodes and C. pocillum) as well as an algal switch by C. pyxidata. Algal switching may be very common in lichens. In addition, existence of cryptic and ecological species within section Cladonia may obscure cospeciation in this section.; Results from this study indicate that further investigation is required to examine a larger number of individuals within each fungal species. This may reveal existence of cryptic species. In addition, the effect of microenvironmental conditions on algal selection requires more study. |
