Genetic Variation in the Apogamous Fern Cyrtomium fortunei (Dryopteridaceae)
In apogamous ferns, all offspring from a parent are expected to be clonal. However, apogamous species frequently show a large amount of morphological and genetic variation. Cyrtomium fortunei and its relatives, which are distributed throughout Japan, are reported to be apogamous triploids, but show large and continuous morphological variation. Four varieties of C. fortunei have been recognized. We sought to determine whether an apogamous species has genetic variation, and if so, whether this variation relates to morphological variation within local populations. Among 224 individuals growing in four distantly located populations in Japan, where several varieties grow together, two rbcL types (α and β) and eight allozyme types (A-H) were identified. Several different genetic clones were detected in the local populations examined. Only individuals that could be morphologically identified as C. fortunei var. intermedium, based on bicolored indusia, had rbcL β and allozyme type H, and thus, were genetically differentiated by their nuclear and plastid genomes from the other three varieties of C. fortunei. The other three varieties shared the same rbcL (α), making correlation between allozyme types and varieties, especially genetic differences between var. fortunei and var. clivicola, unclear.