Origin of the apogamous Japanese fern Dryopteris yakusilvicola (Dryopteridaceae)

The Japanese apogamous fern Dryopteris yakusilvicola was previously thought to be a hybrid of D. sabaei and D. sparsa var. sparsa based on morphological characterization and enzyme electrophoresis. However, the phylogenetic relationships with D. hayatae, D. melanocarpa var. melanocarpa, D. melanocarpa var. elegans, and D. sparsa var. ryukyuensis have been unclear. We performed a molecular phylogenetic analysis of the DNA sequences of two plastid (trnL-F, rbcL) and one low-copy nuclear marker (AK1) of Dryopteris yakusilvicola and related species. The origin of D. yakusilvicola is not a hybrid between D. sparsa var. sparsa and D. sabaei, but the parents appear to have been undetected species closely related to D. melanocarpa var. elegans and D. sabaei. Analysis of additional species of the D. sparsa complex around Southeast Asia and additional nuclear markers are needed to clarify the relationships of this complex.