Search

Climate change poses significant threats to forests globally. Understanding the relationship between environmental variables and species distribution is crucial for evaluating the vulnerability of tree species assemblies to anticipated climate change. Here, we address whether projected future changes in climate suitability are related to the structural stability of the old-growth forest community in Japan. We hypothesize that even with the expected changes in climate, the structural stability of the species assembly will remain unchanged until the end of this century. We modeled the influence of climate change on the spatial distribution of major tree species in a temperate deciduous forest reserve using local and regional presence data. We used the Maxent model and QGIS software to project potential habitat changes. Focusing on the period 2081–2,100, we used the MRI-ESM2-O general circulation model under baseline (SSP5–8.5) and mitigation (SSP1–2.6) future climate scenarios. This revealed that winter temperature is the most crucial factor affecting the distribution of tree species in the temperate landscape. Canopy tree species such as Acer pictum and Castanea crenata are projected to remain stable under SSP5–8.5 in 2100. Our results also suggest that the distribution of Quercus serrata , the dominant species in the forest studied, will expand, particularly under extreme climate conditions in 2100. However, there may be potential reductions in the abundance of subcanopy species, indicating a change in the structure of the forest stand. In this sense, the stability of forest ecosystems and local species diversity may be vulnerable under future climate change scenarios. Exploring the future species distribution and stand structure can improve understanding of habitat changes in temperate landscapes and requires more focused research efforts. [ABSTRACT FROM AUTHOR]

A glacial relict, a remnant of a cold‐adapted species or population from a postglacial retreat, is essential for understanding the formation processes of present‐day vegetation. Although past distributions have been reconstructed for several woody species in Japan, few studies have focused on the cold‐adapted woody species that survive in the Japanese Archipelago. Betula costata Trautv., a species considered a glacial relict, is a common canopy tree in the cool‐cold temperate forests in Northeast Asia. However, B. costata is rare and has a disjunct distribution in the Japanese Archipelago, and the reasons for its rarity and disjunction in Japan remain poorly understood. Therefore, we investigated the distribution of B. costata in Northeast Asia since the last glacial maximum (LGM; between ca. 27,000 and 19,000 years ago) using species distribution models (SDMs). We tested the working hypothesis that B. costata was once abundant in the Japanese Archipelago during the LGM. However, postglacial climate warming caused it to become a disjunct and relict. Two types of SDMs, Maxnet and Random Forest, predicted suitable habitats for the species with three time periods: The LGM, mid‐Holocene, and present. The resulting maps of suitable habitats during the LGM showed extensive distribution across continental Asia and the Japanese Archipelago. By the mid‐Holocene and the present, suitable habitats expanded northward in continental Asia but retreated in the Japanese Archipelago due to increases in the minimum coldest quarter temperature and precipitation. These simulation results support the hypothesis that the Japanese population of B. costata is a glacial relict. [ABSTRACT FROM AUTHOR]

Summary: 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.We used ecological, morphological, and molecular data to investigate the impact of bumblebee absence on the evolution of two closely related orchid species, Goodyera henryi and Goodyera similis, focusing on Kozu Island, the Izu Islands.Our investigation revealed that while G. henryi exclusively relies on a bumblebee species for pollination on the mainland, G. similis is pollinated by scoliid wasps on both the mainland and the island. Intriguingly, all specimens initially categorized as G. henryi on Kozu Island are hybrids of G. henryi and G. similis, leading to the absence of pure G. henryi distribution on the island. These hybrids are pollinated by the scoliid wasp species that also pollinates G. similis on the island.The absence of bumblebees might result in sporadic and inefficient pollination of G. henryi by scoliid wasps, consequently promoting hybrid proliferation on the island. Our findings suggest that the absence of bumblebees can blur plant species boundaries. [ABSTRACT FROM AUTHOR]

Warm‐edge populations, that is, those usually small and isolated populations at the boundary of species maximum temperature range limit, are of particular scientific and conservation interest. This is especially the case for those that have long been geographically isolated, possibly through multiple glaciations, as they can contribute significantly to species' overall genetic diversity. However, distinguishing between glacial relict and more recently established warm‐edge populations is difficult especially in the absence of a continuous fossil record. In this study, we investigate the origin of anomalously low‐elevation warm‐edge populations of the dominant cool temperate Japanese tree Fagus crenata in the northeast Kanto (NEK) region. We sought to determine whether these populations are glacial relicts or, rather, were established via dispersal in the Holocene using chloroplast and nuclear genetic data, species distribution modeling and comparison with populations in a well‐established glacial refugia (south‐central Kyushu [SCK]) and of mid‐late Holocene age (southern Hokkaido [SH]). Whole chloroplast genome "mining" revealed a similar amount of haplotype diversity in NEK and SCK while there was no chloroplast variation in SH. Populations in NEK, particularly the lowest elevation sites, harbored unique haplotypes providing evidence for their persistence since the Last Glacial Maximum as supported by species distribution models under two of three general circulation models. NEK populations also lacked the genetic signatures of recent expansion that characterize the most northern‐edge populations in SH. We conclude that warm‐edge populations in NEK are most likely relicts of glacial refugia and should be given high priority for conservation. [ABSTRACT FROM AUTHOR]

Within their natural distribution ranges, plant species exhibit a genetic structure that has been created by global climate change and natural selection over long periods. This genetic structure needs to be conserved for sustainable use of genetic resources. To conserve local forests with different genetic structures, genetic guidelines for seed and seedling transfer in individual species are necessary. Genetic guidelines have been published for 43 Japanese tree species using population genetic data; however, for practical use, more detailed genetic borders between important genetic lineages should be clarified to inform seed collection and planting. Thus, we investigated in detail the genetic borders between two important Japanese oak species, Quercus serrata and Quercus crispula, in the Chubu region of Japan using chloroplast and nuclear DNA markers, and we discuss the factors that influenced border creation using the results of species distribution modeling (SDM). The chloroplast DNA (cpDNA) haplotype was clearly different within the Chubu region of Japan but the difference in nuclear DNA between northern and southern haplotype populations was very small, both in Q. serrata and Q. crispula. The results of SDM showed that during the last glacial maximum (LGM) Q. serrata was distributed mostly along the coastline but Q. crispula was distributed not only along the coast but also in mountainous areas further inland. The cpDNA genetic borders of these two oak species are complex and seem to have been influenced by topography and their distribution during the LGM. We propose and discuss genetic guidelines for these two oak species based on the results of this study. [ABSTRACT FROM AUTHOR]