Demography and selection analysis of the incipient adaptive radiation of a Hawaiian woody species.

Ecological divergence in a species provides a valuable opportunity to study the early stages of speciation. We focused on Metrosideros polymorpha, a unique example of the incipient radiation of woody species, to examine how an ecological divergence continues in the face of gene flow. We analyzed the whole genomes of 70 plants collected throughout the island of Hawaii, which is the youngest island with the highest altitude in the archipelago and encompasses a wide range of environments. The continuous M. polymorpha forest stands on the island of Hawaii were differentiated into three genetic clusters, each of which grows in a distinctive environment and includes substantial genetic and phenotypic diversity. The three genetic clusters showed signatures of selection in genomic regions encompassing genes relevant to environmental adaptations, including genes associated with light utilization, oxidative stress, and leaf senescence, which are likely associated with the ecological differentiation of the species. Our demographic modeling suggested that the glaberrima cluster in wet environments maintained a relatively large population size and two clusters split: polymorpha in the subalpine zone and incana in dry and hot conditions. This ecological divergence possibly began before the species colonized the island of Hawaii. Interestingly, the three clusters recovered genetic connectivity coincidentally with a recent population bottleneck, in line with the weak reproductive isolation observed in the species. This study highlights that the degree of genetic differentiation between ecologically-diverged populations can vary depending on the strength of natural selection in the very early phases of speciation.

Phylogeographical evidence for historical long-distance dispersal in the flightless stick insect Ramulus mikado.

Exploring how organisms overcome geographical barriers to dispersal is a fundamental question in biology. Passive long-distance dispersal events, although infrequent and unpredictable, have a considerable impact on species range expansions. Despite limited active dispersal capabilities, many stick insect species have vast geographical ranges, indicating that passive long-distance dispersal is vital for their distribution. A potential mode of passive dispersal in stick insects is via the egg stage within avian digestive tracts, as suggested by experimental evidence. However, detecting such events under natural conditions is challenging due to their rarity. Therefore, to indirectly assess the potential of historical avian-mediated dispersal, we examined the population genetic structure of the flightless stick insect Ramulus mikado across Japan, based on a multifaceted molecular approach [cytochrome oxidase subunit I (COI) haplotypes, nuclear simple sequence repeat markers and genome-wide single nucleotide polymorphisms]. Subsequently, we identified unique phylogeographic patterns, including the discovery of identical COI genotypes spanning considerable distances, which substantiates the notion of passive long-distance genotypic dispersal. Overall, all the molecular data revealed the low and mostly non-significant genetic differentiation among populations, with identical or very similar genotypes across distant populations. We propose that long-distance dispersal facilitated by birds is the plausible explanation for the unique phylogeographic pattern observed in this flightless stick insect.

Temporal and interspecific dietary variation in wintering ducks in agricultural landscapes.

Farmlands are becoming more important as waterfowl foraging habitats, while natural wetlands are being lost globally. However, it is unclear how waterfowl coexist in agricultural landscapes by resource partitioning. We evaluated the diets of seven sympatric dabbling ducks foraging in rice paddy and lotus fields around Lake Kasumigaura, the second largest lake in Japan, during two wintering seasons (from November to February) by faecal DNA metabarcoding using chloroplast trnL and mitochondrial CO1 region sequences. We examined 420 faecal samples and found different patterns of dietary diversity and composition among the duck species. The pattern also differed between plant and invertebrate food. Dietary niche partitioning was clear in plant food. Large-bodied ducks intensively use crop plants, and other ducks might mediate competition by using terrestrial and aquatic plants that are suitable for their foraging behaviours or microhabitats. Dietary segregation among species was the most apparent in February, when the abundance of foraging ducks was the largest. This study illustrated the complex pattern of dietary niche partitioning of dabbling ducks in agricultural landscapes, which might be difficult to evaluate by conventional approaches. The availability of crop plants, as well as other plant food resources in flooted areas and farmland dikes, may enable ducks to coexist by spatial or behavioural resource partitioning.

Genetic and demographic signatures accompanying the evolution of the selfing syndrome in Daphne kiusiana, an evergreen shrub.

BACKGROUND AND AIMS: The evolution of mating systems from outcrossing to self-fertilization is a common transition in flowering plants. This shift is often associated with the 'selfing syndrome', which is characterized by less visible flowers with functional changes to control outcrossing. In most cases, the evolutionary history and demographic dynamics underlying the evolution of the selfing syndrome remain poorly understood. METHODS: Here, we characterize differences in the demographic genetic consequences and associated floral-specific traits between two distinct geographical groups of a wild shrub, Daphne kiusiana, endemic to East Asia; plants in the eastern region (southeastern Korea and Kyushu, Japan) exhibit smaller and fewer flowers compared to those of plants in the western region (southwestern Korea). Genetic analyses were conducted using nuclear microsatellites and chloroplast DNA (multiplexed phylogenetic marker sequencing) datasets. KEY RESULTS: A high selfing rate with significantly increased homozygosity characterized the eastern lineage, associated with lower levels of visibility and herkogamy in the floral traits. The two lineages harboured independent phylogeographical histories. In contrast to the western lineage, the eastern lineage showed a gradual reduction in the effective population size with no signs of a severe bottleneck despite its extreme range contraction during the last glacial period. CONCLUSIONS: Our results suggest that the selfing-associated morphological changes in D. kiusiana are of relatively old origin (at least 100 000 years ago) and were driven by directional selection for efficient self-pollination. We provide evidence that the evolution of the selfing syndrome in D. kiusiana is not strongly associated with a severe population bottleneck.

Effects of fruit dimorphism on genetic structure and gene flow in the coastal shrub Scaevola taccada.

BACKGROUND AND AIMS: Plant propagules often possess specialized morphologies that facilitate dispersal across specific landscapes. In the fruit dimorphism of a coastal shrub, Scaevola taccada, individual plants produce either cork-morph or pulp-morph fruits. The former is buoyant and common on sandy beaches, whereas the latter does not float, is bird-dispersed, and is common on elevated sites such as slopes on sea cliffs and behind rocky shores. We hypothesized that beach populations bridge the heterogeneous landscapes by serving as a source of both fruit types, while dispersal is biased for the pulp morph on elevated sites within the islands and for the cork morph between beaches of different islands. Based on this hypothesis, we predicted that populations in elevated sites would diverge genetically over time due to isolation by distance, whereas beach populations would maintain high genetic similarity via current gene flow. METHODS: The genetic structure and gene flow in S. taccada were evaluated by investigating genome-wide single nucleotide polymorphisms in plants from 17 sampling sites on six islands (belonging to the Ryukyu, Daito and Ogasawara Islands) in Japan. KEY RESULTS: Geographical isolation was detected among the three distant island groups. Analyses within the Ryukyu Islands suggested that sandy beach populations were characterized by genetic admixture, whereas populations in elevated sites were relatively isolated between the islands. Pairwise FST values between islands were lowest between sandy beaches, intermediate between sandy beaches and elevated sites, and highest between elevated sites. CONCLUSIONS: Dispersal across the ocean by cork morphs is sufficiently frequent to prevent genetic divergence between beaches of different islands. Stronger genetic isolation of elevated sites between islands suggests that bird dispersal by pulp morphs is restricted mainly within islands. These contrasting patterns of gene flow realized by fruit dimorphism provide evidence that fruit characteristics can strongly mediate genetic structure.

Inferring historical survivals of climate relicts: the effects of climate changes, geography, and population-specific factors on herbaceous hydrangeas.

Climate relicts hold considerable importance because they have resulted from numerous historical changes. However, there are major interspecific variations among the ways by which they survived climate changes. Therefore, investigating the factors and timing that affected population demographics can expand our understanding of how climate relicts responded to historical environmental changes. Here, we examined herbaceous hydrangeas of genus Deinanthe in East Asia, which show limited distributions and a remarkable disjunction between Japan and central China. Chloroplast genome and restriction site-associated DNA sequencing revealed that speciation event occurred in the late Miocene (ca. 7-9 Mya) in response to global climate change. Two lineages apparently remained not branched until the middle Quaternary, and afterwards started to diverge to regional population groups. The narrow endemic species in central China showed lower genetic diversity (He = 0.082), as its population size rapidly decreased during the Holocene due to isolation in montane refugia. Insular populations in the three Japanese islands (He = 0.137-0.160) showed a genetic structure that was inconsistent with sea barriers, indicating that it was shaped in the glacial period when its range retreated to coastal refugia on the exposed sea floor. Demographic modelling by stairway-plot analysis reconstructed variable responses of Japanese populations: some experienced glacial bottlenecks in refugial isolation, while post-glacial range expansion seemingly exerted founder effects on other populations. Overall, this study demonstrated the involvement of not just one, but multiple factors, such as the interplay between climate changes, geography, and other population-specific factors, that determine the demographics of climate relicts.

Genomic insights on the contribution of balancing selection and local adaptation to the long-term survival of a widespread living fossil tree, Cercidiphyllum japonicum.

'Living fossils' are testimonies of long-term sustained ecological success, but how demographic history and natural selection contributed to their survival, resilience, and persistence in the face of Quaternary climate fluctuations remains unclear. To better understand the interplay between demographic history and selection in shaping genomic diversity and evolution of such organisms, we assembled the whole genome of Cercidiphyllum japonicum, a widespread East Asian Tertiary relict tree, and resequenced 99 individuals of C. japonicum and its sister species, Cercidiphyllum magnificum (Central Japan). We dated this speciation event to the mid-Miocene, and the intraspecific lineage divergence of C. japonicum (China vs Japan) to the Early Pliocene. Throughout climatic upheavals of the late Tertiary/Quaternary, population bottlenecks greatly reduced the genetic diversity of C. japonicum. However, this polymorphism loss was likely counteracted by, first, long-term balancing selection at multiple chromosomal and heterozygous gene regions, potentially reflecting overdominance, and, second, selective sweeps at stress response and growth-related genes likely involved in local adaptation. Our findings contribute to a better understanding of how living fossils have survived climatic upheaval and maintained an extensive geographic range; that is, both types of selection could be major factors contributing to the species' survival, resilience, and persistence.

Genetic consequences of plant edaphic specialization to solfatara fields: Phylogenetic and population genetic analysis of Carex angustisquama (Cyperaceae).

Edaphic specialization is one of the main drivers of plant diversification and has multifaceted effects on population dynamics. Carex angustisquama is a sedge plant growing only on heavily acidified soil in solfatara fields, where only extremophytes can survive. Because of the lack of closely related species in similar habitats and its disjunct distribution, the species offers ideal settings to investigate the effects of adaptation to solfatara fields and of historical biogeography on the genetic consequences of plant edaphic specialization to solfatara fields. Here, genome-wide single nucleotide polymorphisms were used to reveal the phylogenetic origin of C. angustisquama, and 16 expressed sequence tag-simple sequence repeat markers were employed to infer population demography of C angustisquama. Molecular phylogenetic analysis strongly indicated that C. angustisquama formed a monophyletic clade with Carex doenitzii, a species growing on nonacidified soil in the sympatric subalpine zone. The result of population genetic analysis showed that C. angustisquama has much lower genetic diversity than the sister species, and notably, all 16 loci were completely homozygous in most individuals of C. angustisquama. Approximate Bayesian computation analysis supported the model that assumed hierarchical declines of population size through its evolutionary sequence. We propose that the edaphic specialist in solfatara fields has newly attained the adaptation to solfatara fields in the process of speciation. Furthermore, we found evidence of a drastic reduction in genetic diversity in C. angustisquama, suggesting that the repeated founder effects associated with edaphic specialization and subsequent population demography lead to the loss of genetic diversity of this extremophyte in solfatara fields.

Turnover of southern cypresses in the post-Gondwanan world: extinction, transoceanic dispersal, adaptation and rediversification.

Cupressaceae subfamily Callitroideae has been an important exemplar for vicariance biogeography, but its history is more than just disjunctions resulting from continental drift. We combine fossil and molecular data to better assess its extinction and, sometimes, rediversification after past global change. Key fossils were reassessed and their phylogenetic placement for calibration was determined using trait mapping and Bayes Factors. Five vicariance hypotheses were tested by comparing molecular divergence times with the timing of tectonic rifting. The role of adaptation to fire (serotiny) in its spread across a drying Australia was tested for Callitris. Our findings suggest that three transoceanic disjunctions within the Callitroideae probably arose from long-distance dispersal. A signature of extinction, centred on the end-Eocene global climatic chilling and drying, is evident in lineages-through-time plots and in the fossil record. Callitris, the most diverse extant callitroid genus, suffered extinctions but surviving lineages adapted and re-radiated into dry, fire-prone biomes that expanded in the Neogene. Serotiny, a key adaptation to fire, likely evolved in Callitris coincident with the biome shift. Both extinction and adaptive shifts have probably played major roles in this chronicle of turnover and renewal, but better understanding of biogeographical history requires improved taxonomy of fossils.

Genomic reconstruction of 100 000-year grassland history in a forested country: population dynamics of specialist forbs.

Grassland ecosystems worldwide have been extensively converted to other land uses and are globally imperiled. Because many grasslands have been maintained by human activities, understanding their origin and history is fundamentally important to better contemporary management. However, existing methods to reconstruct past vegetation can produce contrasting views on grassland history. Here, we inferred demographic histories of 40 populations of four grassland forb species throughout Japan using high-resolution genome sequences and model-flexible demographic simulation based on the site frequency spectrum. Although two species showed a slight decline in population size between 100 000-10 000 years ago, our results suggest that population sizes of studied species have been maintained within the range of 0.5-2.0 times the most recent estimates for at least 100 000 years across Japan. Our results suggest that greater than 90% declines in Japanese grasslands and subsequent losses of grassland species in the last 100 years are geologically and biologically important and will have substantial consequences for Japanese biota and culture. People have had critical roles in maintaining disturbance-dependent grassland ecosystems and biota in this warm and wet forested country. In these contexts, disturbances associated with forest harvesting and traditional extensive farming have the potential to maintain grassland ecosystems and can provide important opportunities to reconcile resource production and conservation of grassland biodiversity.

Environmental DNA Collected from Snow Tracks is Useful for Identification of Mammalian Species.

Noninvasive genetic analysis is being used increasingly in field surveys. However, detecting large and middle-sized mammals, such as Carnivora species, using noninvasive samples, such as scat or hair, is time- and labor-intensive due to their low densities and elusive behaviors. As snow tracks are the most frequently encountered natural signs of terrestrial mammals in winter, we employed several methods to recover environmental DNA (eDNA) from snow tracks. We performed both DNA metabarcoding and Sanger sequence analyses, in combination with universal primers on the mitochondrial 12S rRNA gene for mammals and taxon-specific primers on the mitochondrial NADH dehydrogenase subunit 2 gene for Martes species (martens and sables in Mustelidae). Snow samples of four Martes melampus tracks, one Cervus nippon track, one Vulpes vulpes track, and the track of an unidentified Carnivora species were collected from a snowfall area in Kyoto, Japan, in February 2018. Regarding DNA metabarcoding analyses, the sequences of three Carnivora species (M. melampus, V. vulpes, and Canis lupus familiaris) and a deer (C. nippon) were obtained from their respective snow tracks. Using Sanger sequencing, eDNA on snow tracks was recovered at the species level except for M. melampus using universal primers, while eDNA of M. melampus was sequenced using Martes-specific primers. Snow track surveys in combination with eDNA techniques could dramatically improve the efficiency of monitoring and conservation of mammals.

Historical changes in grassland area determined the demography of semi-natural grassland butterflies in Japan.

Semi-natural grassland areas expanded worldwide several thousand years ago following an increase in anthropogenic activities. However, semi-natural grassland habitat areas have been declining in recent decades due to changes in landuse, which have caused a loss of grassland biodiversity. Reconstructing historical and recent demographic changes in semi-natural grassland species will help clarify the factors affecting their population decline. Here we quantified past and recent demographic histories of Melitaea ambigua (Lepidoptera; Nymphalidae), an endangered grassland butterfly species in Japan. We examined changes in demography over the past 10,000 years based on 1378 bp of mitochondrial COI gene. We then examined changes in its genetic diversity and structure during the last 30 years using nine microsatellite DNA markers. The effective population size of M. ambigua increased about 3000-6000 years ago. In contrast, the genetic diversity and effective population sizes of many populations significantly declined from the 1980s to 2010s, which is consistent with a recent decline in the species population size. Our data suggest that the M. ambigua demography can be traced to changes in area covered by semi-natural grasslands throughout the Holocene.

Identification of two mutations that cause defects in the ligninolytic system through an efficient forward genetics in the white-rot agaricomycete Pleurotus ostreatus.

White-rot fungi play an important role in the global carbon cycle because they are the species that almost exclusively biodegrade wood lignin in nature. Lignin peroxidases (LiPs), manganese peroxidases (MnPs) and versatile peroxidases (VPs) are considered key players in the ligninolytic system. Apart from LiPs, MnPs and VPs, however, only few other factors involved in the ligninolytic system have been investigated using molecular genetics, implying the existence of unidentified elements. By combining classical genetic techniques with next-generation sequencing technology, they successfully showed an efficient forward genetics approach to identify mutations causing defects in the ligninolytic system of the white-rot fungus Pleurotus ostreatus. In this study, they identified two genes - chd1 and wtr1 - mutations in which cause an almost complete loss of Mn2+ -dependent peroxidase activity. The chd1 gene encodes a putative chromatin modifier, and wtr1 encodes an agaricomycete-specific protein with a putative DNA-binding domain. The chd1-1 mutation and targeted disruption of wtr1 hamper the ability of P. ostreatus to biodegrade wood lignin. Examination of the effects of the aforementioned mutation and disruption on the expression of certain MnP/VP genes suggests that a complex mechanism underlies the ligninolytic system in P. ostreatus.

Effects of pex1 disruption on wood lignin biodegradation, fruiting development and the utilization of carbon sources in the white-rot Agaricomycete Pleurotus ostreatus and non-wood decaying Coprinopsis cinerea.

Peroxisomes are well-known organelles that are present in most eukaryotic organisms. Mutant phenotypes caused by the malfunction of peroxisomes have been shown in many fungi. However, these have never been investigated in Agaricomycetes, which include white-rot fungi that degrade wood lignin in nature almost exclusively and play an important role in the global carbon cycle. Based on the results of a forward genetics study to identify mutations causing defects in the ligninolytic activity of the white-rot Agaricomycete Pleurotus ostreatus, we report phenotypes of pex1 disruptants in P. ostreatus, which are defective in two major features of white-rot Agaricomycetes: lignin biodegradation and mushroom formation. Pex1 disruption was also shown to cause defects in the hyphal growth of P. ostreatus on certain sawdust and minimum media. We also demonstrated that pex1 is essential for fruiting initiation in the non-wood decaying Agaricomycete Coprinopsis cinerea. However, unlike P. ostreatus, significant defects in hyphal growth on the aforementioned agar medium were not observed in C. cinerea. This result, together with previous C. cinerea genetic studies, suggests that the regulation mechanisms for the utilization of carbon sources are altered during the evolution of Agaricomycetes or Agaricales.

The population genomic signature of environmental association and gene flow in an ecologically divergent tree species Metrosideros polymorpha (Myrtaceae).

Genomewide markers enable us to study genetic differentiation within a species and the factors underlying it at a much higher resolution than before, which advances our understanding of adaptation in organisms. We investigated genomic divergence in Metrosideros polymorpha, a woody species that occupies a wide range of ecological habitats across the Hawaiian Islands and shows remarkable phenotypic variation. Using 1659 single nucleotide polymorphism (SNP) markers annotated with the genome assembly, we examined the population genetic structure and demographic history of nine populations across five elevations and two ages of substrates on Mauna Loa, the island of Hawaii. The nine populations were differentiated into two genetic clusters distributed on the lower and higher elevations and were largely admixed on the middle elevation. Demographic modelling revealed that the two genetic clusters have been maintained in the face of gene flow, and the effective population size of the high-altitude cluster was much smaller. A FST -based outlier search among the 1659 SNPs revealed that 34 SNPs (2.05%) were likely to be under divergent selection and the allele frequencies of 21 of them were associated with environmental changes along elevations, such as temperature and precipitation. This study shows a genomic mosaic of M. polymorpha, in which contrasting divergence patterns were found. While most genomic polymorphisms were shared among populations, a small fraction of the genome was significantly differentiated between populations in diverse environments and could be responsible for the dramatic adaptation to a wide range of environments.

Genetic diversity and population structure of Nuphar submersa (Nymphaeaceae), a critically endangered aquatic plant endemic to Japan, and implications for its conservation.

Nuphar submersa (Nymphaeaceae) is a critically endangered freshwater macrophyte indigenous to central Japan, with only four small extant populations represented across its entire range. We investigated the genotypic and genetic diversity as well as the genetic structure of all extant individuals of N. submersa based on analysis of 15 microsatellite loci. Among 278 individual ramets, 52 multilocus genotypes were detected: 30 genotypes in Nikko City (NIK), 18 in Nasukarasuyama City (NAS), 3 in Mooka City (MOK), and 1 in Sakura City (SAK). The average number of alleles per locus ranged from 1.20 to 1.93, whereas the observed and expected heterozygosities ranged from 0.11 to 0.33 and from 0.10 to 0.24, respectively. With the exception of SAK, all populations contained multiple clones, but our results indicated low levels of within-population genetic diversity. The populations NIK and NAS comprised few large or middle-sized genets and many small genets. The populations NIK and NAS were suggested to comprise large old, old fragmented, and/or young small genets resulting from seedling establishment. All four populations were differentiated, and gene flow between the populations was restricted (average level of gene flow (Nm) = 0.122, G' ST  = 0.639). Of the total genetic diversity, 67.20 and 9.13% were attributable to inter- and intra-population diversity, respectively. STRUCTURE analysis revealed two or three well-differentiated groups of populations. Cluster I comprised one population (NIK) and cluster II comprised the remaining populations at K = 2. The populations NIK, NAS, and the remaining populations were assigned to clusters I, II, and III, respectively, at K = 3. For conservation practices, we recommend that each cluster be regarded as a different management unit. We further suggest that artificial gene flow among MOK and SAK populations is an appropriate option, whereas NIK should not be reinforced with genotypes from the remaining populations.

Chloroplast DNA sequencing and detailed microsatellite genotyping of all remnant populations suggests that only a single genet survives of the critically endangered plant Rehmannia japonica.

Rehmannia japonica (Thunb.) Makino ex T. Yamaz. is an endangered perennial herb species in Japan. Although earlier the Japanese considered it a variety of R. glutinosa, recent Japanese taxonomists have consistently regarded it as an independent species. According to the historical literature, Rehmannia japonica seems to have been known in China and Japan in the past. However, Chinese taxonomists do not recognize R. japonica at present. In Japan, only two populations are known, and although these populations flower every year, seed reproduction has not been observed. In this study, we aimed to reveal the phylogenetic relationships and levels of genetic diversity of R. japonica. A haplotype network based on two chloroplast DNA regions (trnL-trnF and rps16) showed that the sequences of R. japonica were distinguishable by three or four sites of indels from the most closely related species, R. chingii, consistent with the separate species status of R. japonica. An analysis of genetic diversity using twelve microsatellite loci showed that all of the ramets of R. japonica collected from two geographically isolated populations had an identical multilocus genotype, including identical heterozygous genotypes at six loci. This result indicated asexual origin of all sampled ramets. This study also suggests that the absence of sexual reproduction of R. japonica is explained by self-incompatibility combined with only a single genet remaining in the R. japonica populations.

Complex pollination of a tropical Asian rainforest canopy tree by flower-feeding thrips and thrips-feeding predators.

PREMISE OF THE STUDY: In tropical rainforests of Southeast Asia, a highly fecund thrips (Thrips spp.) responds rapidly to the mass flowering at multiple-year intervals characteristic of certain species such as the canopy tree studied here, Shorea acuminata, by feeding on flower resources. However, past DNA analyses of pollen adherent to thrips bodies revealed that the thrips promoted a very high level of self-pollination. Here, we identified the pollinator that contributes to cross-pollination and discuss ways that the pollination system has adapted to mass flowering. METHODS: By comparing the patterns of floral visitation and levels of genetic diversity in adherent pollen loads among floral visitors, we evaluated the contribution of each flower visitor to pollination. KEY RESULTS: The big-eyed bug, Geocoris sp., a major thrips predator, was an inadvertent pollinator, and importantly contributed to cross-pollination. The total outcross pollen adhering to thrips was approximately 30% that on the big-eyed bugs. Similarly, 63% of alleles examined in S. acuminata seeds and seedlings occurred in pollen adhering to big-eyed bugs; about 30% was shared with pollen from thrips. CONCLUSIONS: During mass flowering, big-eyed bugs likely travel among flowering S. acuminata trees, attracted by the abundant thrips. Floral visitation patterns of big-eyed bugs vs. other insects suggest that these bugs can maintain their population size between flowering by preying upon another thrips (Haplothrips sp.) that inhabits stipules of S. acuminata throughout the year and quickly respond to mass flowering. Thus, thrips and big-eyed bugs are essential components in the pollination of S. acuminata.

A quantitative analysis of phenotypic variations of Metrosideros polymorpha within and across populations along environmental gradients on Mauna Loa, Hawaii.

Metrosideros polymorpha, a dominant tree species in the Hawaiian Islands, shows an extreme phenotypic polymorphism both across gradients of climatic/edaphic conditions and within populations, making it a potentially useful model species for evolutionary study. In order to understand how the phenotypic diversity is maintained within populations as well as across populations, we examined the diversities of several leaf and stem functional traits across five elevations and two soil substrates on the volcanic mountain of Mauna Loa, on the island of Hawaii. Leaf dry mass per area (LMA), a key leaf functional trait, was particularly focused on and analyzed in relation to its underlying components-namely, tissue LMA and trichome LMA (LMA = tissue LMA + trichome LMA). Across populations, tissue LMA increased linearly with elevation while trichome LMA showed unimodal patterns with elevation, which were better correlated with temperature and rainfall, respectively. Substantial phenotypic variations were also found within populations. Interestingly, the variations of tissue LMA were often negatively correlated to trichome LMA within populations, which contrasts with the cross-populations pattern, where a strong positive correlation between tissue LMA and trichome LMA was found. This suggests that phenotypic variations within populations were substantially influenced by local ecological processes. Soil depth (an indicator of local water availability) and tree size (an indicator of colonized timing) modestly explained the within-population variations, implying other local environmental factors and/or random processes are also important in local phenotypic diversity. This study provides an insight about how phenotypic diversity of plant species is maintained from local to landscape levels.

Predominance of a single clone of the most widely distributed bamboo species Phyllostachys edulis in East Asia.

Phyllostachys edulis, one of the most dominant bamboo species with the leptomorph rhizome system, has been asexually expanding its range into adjacent natural forest sites by shooting new culms. The resulting ecological problems include simplification of stand structure and decline in the species diversity of local flora. In this study, the genetic diversity of P. edulis for the entire distribution range from Japan to China was analyzed using 16 microsatellite markers. Among these, 12 loci were fixed by a single allele, whereas only two alleles were detected for each of the remaining 4 loci; all adult samples shared the same genotype at all loci including the four heterozygous loci. These observations indicate that all current samples from Japan and China comprise an identical clone. The clone is distributed over more than 2,800 km with an estimated biomass of approximately 6.6 × 10(11) kg, which is exceptionally large. Among seedlings from flowering events in 2005 and 2006, 20 different genets were generated by recombination through selfing of a single flowering genet. Predominance of a single clone in the wild and a diverse composition of genets among seedlings suggest that the intermittent flowering of P. edulis in the wild has produced a variety of clones through recombination. However, the resulting seedlings cannot compete with other tree species or adult P. edulis, and almost all adult P. edulis growing in Japan and China likely propagated through vegetative reproduction of a single clone by human transplantation, and subsequently expanded into adjacent forest sites by shooting young sprouts. The relatively small size of the flowering area and rapid culm reproduction has led to the stability of P. edulis communities. However, the low genetic diversity is an important consideration for the long-term management of this prevailing bamboo species.