Molecular phylogeny and taxonomy of the Hydrangea serrata complex (Hydrangeaceae) in western Japan, including a new subspecies of H. acuminata from Yakushima

According to the contemporary classification of Hydrangea native to Japan, H. serrata is a polymorphic species including six varieties. We discovered a plant identified as H. serrata, but morphologically distinct from previously known varieties, in Yakushima island where approximately 50 endemic species are known. To determine the relationship of this plant with previously known varieties, we examined morphology and constructed a highly resolved phylogeny of H. serrata and its relatives using three chloroplast genomic regions, rbcL, trnL intron, psbA-trnH, and two nuclear genomic regions, ITS1 and ITS2, and Multiplex ISSR genotyping by sequencing (MIG-seq). Based on these morphological and phylogenetic observations, we describe Hydrangea acuminata subsp. yakushimensissubsp. nov. as a newly discovered lineage in Yakushima, Japan and propose Hydrangea minamitaniistat. nov. and Hydrangea acuminata subsp. australisstat. nov. which were previously treated as varieties of H. serrata.

Influence of environmental parameters on habitat use by sympatric freshwater eels, Anguilla marmorata and A. japonica on Yakushima Island, Japan

It is known that environmental parameters, such as water depth, size of substrate material, and current velocity influence the organization of stream fish communities. However, few studies have investigated the effects of these parameters on sympatric freshwater eels. Here, the habitat use of two anguillid eels, Anguilla marmorata Quoy and Gaimard, 1824 and A. japonica Temminck and Schlegel, 1846, coexisting in the same river systems in Japan was investigated. It was found that the tropical species A. marmorata exclusively utilized habitats with larger substrate materials, fewer fallen leaves and less leaf detritus, higher current velocity, and lower turbidity than the temperate species A. japonica, and the distributions of the two anguillid eels were clearly segregated. Thus, when both species co-occur in the same river systems, clear flowing mainstems and tributaries are preferred habitats for A. marmorata, while stagnant muddy estuaries, backwater areas, irrigation channels, and reservoirs are preferred habitats for A. japonica. These habitat segregations were consistent through body-size increases and life-stage developments from elver to yellow eel and did not show ontogenetic shifts. The findings indicated that both species had strong habitat preferences, and these environmental parameters must be considered in the conservation of anguillid eels in sympatric zones.

The genus Rhyacophila Stephens (Trichoptera, Rhyacophilidae) in Yakushima Island, northern Ryukyu, southwestern Japan

This study revises the caddisfly genus Rhyacophila Stephens, Rhyacophilidae, for Yakushima Island within the northern Ryukyu Archipelago in southwestern Japan. Four new species are described based on adults: Rhyacophila yakushima sp. nov. of the R. anatina Species Group, R. arakawa sp. nov. of the R. lieftincki Species Group, R. miyanoura sp. nov. of the R. yosiiana Species Group, and R. nagata sp. nov. of the R. ulmeri Species Group. Additionally, two species are recorded for the island for the first time: R. brevicephala Iwata 1927, a Japanese species, and R. shikotsuensis Iwata 1927, an East Asian species.

Tourism and Counterurbanization in a Low-Amenity Peripheral Island: A Longitudinal Study at Yakushima Island in Kagoshima, Japan

This research explored the long-term relation between tourism development and counterurbanization in a remote island in Japan, as the longevity of in-migrants’ role in low-amenity tourism destinations has been questioned. Using data collected over 10 years at Yakushima Island, the study investigated the island’s population trend, in-migrants’ motivation for relocation, their contributions to tourism, and the lives on the island. The results showed that the trend of population growth differed among Yakushima’s 24 villages likely because of accessibility, proximity to tourism attractions, the weather, and housing availability. Yakushima’s natural environment was the key factor in in-migrants’ migration choice. Encounters and connections with people on the island were found to be another important factor. In-migrants introduced ecotours as an innovation in the 1990s, and thereafter, many in-migrants moved to Yakushima with high aspirations of becoming tour guides. Tourism stagnated starting in 2008, and some in-migrants began moving out of the island. Despite the overall downward trend of tourism, an increase in international tourists created a niche market before the COVID-19 pandemic, attracting foreign in-migrants as tourism entrepreneurs in recent years. Similar to the main driver for Japanese in-migrants’ relocation, nature was also the main motivation for international tourists’ relocation.

Integrative taxonomy reveals multiple lineages of the spider genus Cybaeus endemic to the Ryukyu Islands, Japan (Arachnida : Araneae : Cybaeidae)

The epigean spiders of the genus Cybaeus L. Koch, 1868 are known to have diversified in western North America and the Japanese Archipelago. To date, ~80 species of Cybaeus are known from Japan, but they have not previously been recorded from the Ryukyu Islands that harbour a diversity of endemic species. Here we describe eight new species of Cybaeus from the Ryukyu Islands, extending the range of Cybaeus southward to the central Ryukyus. Both sexes of each of the new species are described, and their phylogenetic relationships are estimated using nuclear and mitochondrial gene markers. Although Cybaeus okumurai, sp. nov. and C. kumadori, sp. nov. possess genital features that are common in the other Japanese congeners, the other six species (C. yakushimensis, sp. nov., C. kodama, sp. nov., C. amamiensis, sp. nov., C. aikana, sp. nov., C. tokunoshimensis, sp. nov., and C. hikidai, sp. nov.) are characterised by an elongated embolus and tubular spermathecae. These unique genital characteristics and the phylogeny recovered here suggest that these features evolved independently among the Japanese and Ryukyu Cybaeus species. Phylogenetic analyses highlight an unusual biogeographical pattern in which C. yakushimensis and C. kodama endemic to Yakushima Island in the northern Ryukyus are related to species distributed in the central Ryukyus. In contrast, our phylogeny suggests that C. okumurai from Tanegashima Island in the northern Ryukyus is sister to C. ashikitaensis (Komatsu, 1968), distributed in Kyushu of the Japanese Archipelago. The retreat constructs and sympatric distribution of Cybaeus found among the Ryukyus are also briefly discussed. ZooBank: urn:lsid:zoobank.org:pub:640D15AA-17F4-48EE-88B4-485CFF8FCD60

Genetic consequences of being a dwarf: do evolutionary changes in life-history traits influence gene flow patterns in populations of the world’s smallest goldenrod?

Background and Aims Contrasting life-history traits can evolve through generations of dwarf plant ecotypes, yet such phenotypic changes often involve decreased plant size and reproductive allocation, which can configure seed dispersal patterns and, subsequently, population demography. Therefore, evolutionary transitions to dwarfism can represent good study systems to test the roles of life-history traits in population demography by comparing genetic structure between related but phenotypically divergent ecotypes. Methods In this study, we examined an ecotypic taxon pair of the world’s smallest goldenrod (stem height 2.6 cm) in alpine habitats and its closely related lowland taxon (30–40 cm) found on Yakushima Island, Japan. Genetic variation in chloroplast DNA sequences, nuclear microsatellites and genome-wide single-nucleotide polymorphisms were used to investigate 197 samples from 16 populations, to infer the population genetic demography and compare local genetic structure of the ecotypes. Key Results We found a pronounced level of genetic differentiation among alpine dwarf populations, which were much less geographically isolated than their lowland counterparts. In particular, several neighbouring dwarf populations (located ~500 m apart) harboured completely different sets of chloroplast haplotypes and nuclear genetic clusters. Demographic modelling revealed that the dwarf populations have not exchanged genes at significant levels after population divergence. Conclusions These lines of evidence suggest that substantial effects of genetic drift have operated on these dwarf populations. The low-growing stature and reduced fecundity (only 3.1 heads per plant) of the dwarf plants may have reduced gene flow and rare long-distance seed dispersal among habitat patches, although the effects of life-history traits require further evaluation using ecological approaches.