Paraphyly of organelle DNAs in Cycas Sect. Asiorientales due to ancient ancestral polymorphisms

<p>Abstract</p> <p>Background</p> <p>This study addresses the apportionment of genetic diversity between <it>Cycas revoluta </it>and <it>C. taitungensis</it>, species that constitute the section <it>Asiorientales </it>and represent a unique, basal lineage of the Laurasian genus <it>Cycas</it>. Fossil evidence indicates divergence of the section from the rest of <it>Cycas </it>at least 30 million years ago. Geographically, <it>C. taitungensis </it>is limited to Taiwan whereas <it>C. revoluta </it>is found in the Ryukyu Archipelago and on mainland China.</p> <p>Results</p> <p>The phylogenies of ribosomal ITS region of mtDNA and the intergenic spacer between <it>atp</it>B and <it>rbc</it>L genes of cpDNA were reconstructed. Phylogenetic analyses revealed paraphyly of both loci in the two species and also in the section <it>Asiorientales</it>. The lack of reciprocal monophyly between these long isolated sections is likely due to persistent shared ancestral polymorphisms. Molecular dating estimated that mt- and cp DNA lineages coalesced to the most recent common ancestors (TMRCA) about 327 (mt) and 204 MYA (cp), corresponding with the divergence of cycad sections in the Mesozoic.</p> <p>Conclusion</p> <p>Fates of newly derived mutations of cycads follow Klopfstein et al.'s surfing model where the majority of new mutations do not spread geographically and remain at low frequencies or are eventually lost by genetic drift. Only successful 'surfing mutations' reach very high frequencies and occupy a large portion of a species range. These mutations exist as dominant cytotypes across populations and species. Geographical subdivision is lacking in both species, even though recurrent gene flow by both pollen and seed is severely limited. In total, the contrasting levels between historical and ongoing gene flow, large population sizes, a long lifespan, and slow mutation rates in both organelle DNAs have all likely contributed to the unusually long duration of paraphyly in cycads.</p

Microtrichomanes digitatum (Sw.) Copel. (Hymenophyllaceae), a New Record from Taiwan

Microtrichomanes digitatum (Sw.) Copel., a filmy fern species, was discovered in the southern Taiwan during the botanical inventory of past decade. It represents a new record for the fern flora of Taiwan. Microtrichomanes digitatum can be distinguished from its congener, M. nitidulum (v. d. Bosch) Copel., in bearing short, stiff, simple, and dark-brown setae on the leaf margins. The present study provides taxonomic description, photographs, and a distribution map. The problems of taxonomy, ecology, conservation, distribution and phytogeography are also discussed

Hymenophyllum pilosissimum C. Chr. (Hymenophyllaceae), a New Recorded Fern from Taiwan

Volume: 100Start Page: 180End Page: 18

Supplements to the Pteridophytes in Taiwan (II): A Newly Recorded Species Diplazium crassiusculum Ching (Athyriaceae)

A newly recorded species, Diplazium crassiusculum Ching, in northern Taiwan is described and illustrated in this paper. It can be distinguished from other congeners by its coriaceous fronds, free terminal pinna, serrate margins, oblong-lanceolate pinnae, and sori solely formed at the acroscopic side of the first veinlet in each venous set. A key is provided to distinguish the morphologically related species of Taiwan. This species is apparently rare and is known only in one location in Taiwan

Deparia Longipes (Woodsiaceae) Native to Taiwan

Volume: 96Start Page: 96End Page: 9

Supplements to the Lycophytes in Taiwan (I): A newly Recorded Species Selaginella lutchuensis Koidz. (Selaginellaceae)

This paper reports a new recorded lycophyte, Selaginella lutchuensis Koidz., collected from eastern Taiwan. This species can be distinguished from other congeners by its resupinate strobili, long-tailed apex of ventral (lateral) trophophyll and distinctly white-callous margin of dorsal (median) one. In the present work, taxonomic description, distribution information, line drawing, and photographs of this newly recorded species are provided. A key is also provided to distinguish the morphologically related species of Taiwan