cpDNA and mtDNA Reveal Two Cryptic Lineages of Blechnum occidentale (Blechnaceae) in Viçosa, Brazil

Based on cpDNA sequences of rbcL gene and trnL-trnF spacer, we provide evidence of two cryptic lineages of Blechnum occidentale occurring in Viçosa, Brazil, which we name α and β. The specimens from α lineage have cpDNA identical to specimens of B. occidentale from elsewhere in the Neotropics, whereas the β lineage is apparently endemic to Viçosa. The putative hybrid B. × confluens, involving B. occidentale × B. polypodioides, has cpDNA identical to the B. occidentale α lineage. In the absence of data suggesting cpDNA is paternally inherited in ferns, we infer that the B. occidentale α lineage is the maternal progenitor of B. ×confluens. The paternal parent—Blechnum polypodioides—is inferred from morphological evidence. Within the B. occidentale β lineage there are specimens identified as B. occidentale var. laceratum, with unique irregular, pinnate-pinnatifid leaves—a character otherwise rare in the genus. The specimens of the B. occidentale β lineage and B. occidentale var. laceratum have identical cpDNA. The mtDNA sequences of atp1 gene are identical among the specimens of the B. occidentale α lineage, B. occidentale β lineage, B. ×confluens, and B. occidentale var. laceratum, but they differ from those of B. polypodioides. These findings suggest that in these ferns the mtDNA inheritance follows the cpDNA inheritance (maternal, in the absence of data suggesting otherwise), and that this mtDNA gene has a lower substitution rate than the rbcL gene.