The absence of bumblebees on an oceanic island blurs the species boundary of two closely related orchids.

Oceanic islands offer valuable natural laboratories for studying evolution. The Izu Islands, with their recent geological origin, provide an exceptional opportunity to explore the initial evolution on oceanic islands. Another noteworthy aspect is the absence of bumblebee species on most Izu Islands.

Morphological, ecological, and molecular phylogenetic approaches reveal species boundaries and evolutionary history of (Orchidaceae, Orchidoideae) and its closely related taxa.

Species delimitation within the genus is challenging among closely related species, because of phenotypic plasticity, ecological variation, and hybridization that confound identification methods based solely on morphology. In this study, we investigated the identity of H.-J.

Polyploid progeny from triploid hybrids of Phegopteris decursivepinnata (Thelypteridaceae).

Phegopteris decursivepinnata includes diploids, tetraploids, and triploid hybrids based on x = 30. We obtained polyploid progeny from triploid hybrids through selfing and crossing experiments. Triploids occasionally formed well-filled spores.

Evidence of genetic segregation in the apogamous fern species Cyrtomium fortunei (Dryopteridaceae).

In apogamous ferns, all offspring from a parent are expected to be clonal. However, apogamous 'species' frequently demonstrate a large amount of morphological and genetic variations. Cyrtomium fortunei composed of four varieties (C.

Two types of partial fertility in a diploid population of the fern Thelypteris decursive-pinnata (Thelypteridaceae).

Two types of abnormal sporophytes were observed in a population of diploid Thelypteris decursive-pinnata. Most sporophytes in this population exhibited regular chromosome pairing, resulting in the formation of 30 bivalents in meiosis I; however, they produced abortive spores to various degrees. Some formed large globose spores at low frequencies, most likely to be unreduced diplospores.