When historically isolated populations meet during postglacial expansion, a mixed distribution of distinct DNA lineages called contact zones is created. The gradual dissolution of the spatial genetic structures in contact zones should be related to differences in pollen and seed dispersal, given no restriction on gene flow by e.g. reproductive isolation. We aimed to clarify effects of pollen dispersal modes on nuclear DNA (nrDNA) genetic structures of two codistributed species with different pollen dispersal modes, by analyzing nuclear microsatellites of the insect-pollinated Magnolia obovata and the wind-pollinated Carpinus laxiflora, which show highly consistent contact zone locations in terms of chloroplast DNA (cpDNA). The genetic structure based on the nrDNA and that based on the cpDNA were concordant in M. obovata, but not so concordant in C. laxiflora . Pollen dispersal ability is higher in the wind-pollinated C. laxiflora than in M. obovata, resulting in the higher estimated pollen/seed migration ratio in C. laxiflora than in M. obovata. Therefore, the extent of postglacial lineage admixture in nrDNA was predominant in C. laxiflora . Our results suggested that differences in pollen dispersal ability may affect the nrDNA genetic structure between co-distributed species with common migration histories in the same area.
In this report, I describe the morphological characteristics, evolutionary relationships, and taxonomy of a newly discovered perennial Mitella amamiana sp. nov. (section Asimitellaria; Saxifragaceae) on Amami-Oshima Island in the central Ryukyus. The discovery is noteworthy because the genus Mitella has been considered absent from the central and southern Ryukyus. Using phylogenetic analyses based on nuclear ribosomal DNA (ETS and ITS) and the two copies of nuclear Granule-bound starch synthase genes (GBSSI-A1 and GBSSI-A2), M. amamiana appears to have a sister relationship with M. doiana Ohwi, which is endemic to Yakushima island in the northern Ryukyus. Mitella amamiana is morphologically similar to M. doiana but clearly differs in the occasional presence of petals and the size of the leaves. Considering that plants of Mitella have low dispersability, the present discovery provides a valuable opportunity to characterize biogeographic associations across the Tokara gap, an ancient and continuous land break between the central and northern Ryukyus.
Podostemaceae comprise a unique aquatic angiosperm family. Members of the family grow on rock surfaces of waterfalls and rapids in the tropics and subtropics. Recently, chloroplast dimorphism was reported for 13 species from the majority of clades in the subfamily Podostemoideae. Large chloroplasts with well-developed starch grains and small chloroplasts with few starch grains are located separately in the epidermal cells of roots and shoots. Transmission electron microscopy (TEM) analysis revealed that the large chloroplast is comparable to a typical, ordinary chloroplast, while the small chloroplast does not, but is specialized. To investigate whether chloroplast dimorphism is common in Podostemaceae, we conducted TEM and light microscopy of six species from two subfamilies, Tristichoideae and Weddellinoideae. All samples examined had uniform chloroplasts of the same size. Evaluation of their ultrastructure indicated they had normal grana and starch grains. These findings suggest that chloroplast dimorphism is a trait limited to Podostemaceae subfamily Podostemoideae.
Psychotria serpens (Rubiaceae) is usually distylous in floral morphology, but uncertainty still remains as to whether the two morphs of the species have self- and intramorph-incompatibility system and also on the efficiency of pollinators. We examined self- and intramorph-incompatibility as well as efficiency in flower visitors to carry out pollination in natural populations. Pollination experiments indicated that P. serpens is self- and intramorph-incompatible, as in other typical distylous species. Flowers of the two morphs produced nectar from the base of the corolla tube and attracted various insects, such as short-tongued wasps, bees, hoverflies, butterflies, etc. Among the flower visitors, the short-tongued wasps, bees and hoverflies were considered to be efficient pollinators for P. serpens in the Ryukyu Islands.
A new species, Garcinia bokorensis H. Toyama & Yahara (Clusiaceae), is described from Bokor National Park, Cambodia. We provide a description, illustration and photographs of the new species, and update the key to identify the species of Garcinia sect. Oxycarpus in Indochina.
A new color variant of Gastrodia fontinalis f. albiflora from Takeshima Island, Kagoshima Prefecture, Japan, is described. The new form, G. fontinalis f. albiflora , is separated from G. fontinalis f. fontinalis only by coloration of the outer surface of the perianth tube (white vs. pale brown), the inflorescence (pale greenish brown vs. dark greenish brown), hypochile (whitish orange vs. red), and the epichile (whitish orange vs. brownish red). The ecological significance of this whitish form of Gastrodia fontinalis is also discussed.
Oreorchis coreana Finet, discovered in Nasushiobara-shi, Tochigi Prefecture, Honshu, is a new addition to the flora of Japan. Until now, Oreorchis coreana was thought to be endemic to Jeju Island, Korea. This finding is a remarkable case of disjunct distribution.