Population Structure Of Species Research Articles

On species delimitation, hybridization and population structure of cassava whitefly in Africa

The Bemisia cassava whitefly complex includes species that cause severe crop damage through vectoring cassava viruses in eastern Africa. Currently, this whitefly complex is divided into species and subgroups (SG) based on very limited molecular markers that do not allow clear definition of species and population structure. Based on 14,358 genome-wide SNPs from 62 Bemisia cassava whitefly individuals belonging to sub-Saharan African species (SSA1, SSA2 and SSA4), and using a well-curated mtCOI gene database, we show clear incongruities in previous taxonomic approaches underpinned by effects from pseudogenes. We show that the SSA4 species is nested within SSA2, and that populations of the SSA1 species comprise well-defined south-eastern (Madagascar, Tanzania) and north-western (Nigeria, Democratic Republic of Congo, Burundi) putative sub-species. Signatures of allopatric incipient speciation, and the presence of a ‘hybrid zone’ separating the two putative sub-species were also detected. These findings provide insights into the evolution and molecular ecology of a highly cryptic hemipteran insect complex in African, and allow the systematic use of genomic data to be incorporated in the development of management strategies for this cassava pest.

The intensity of kelp harvesting shapes the population structure of the foundation species Lessonia trabeculata along the Chilean coastline

Kelp are foundation species that support high levels of biodiversity and, either directly or indirectly provide a wide range of ecological goods and services to human society. In recent decades, due to the high demand for kelp-derived products such as alginate, commercial wild harvesting has increased, leading to declines of kelp biomass in some regions. Chile accounts for 40% of the global kelp harvest, with the subtidal kelp, Lessonia trabeculata being one of the main target species. Currently, however, there is a lack of information on how different degrees of harvesting intensity, governed by distinct management regimes and their enforcement influences L. trabeculata populations. Here we examined the effect different management regimes, characterised by distinct levels of exploitation of kelp and kelp-associated fauna, have on L. trabeculata density and morphology along ~ 1600 km of the Chilean coastline. The findings demonstrated that harvesting intensity likely influences both L. trabeculata density and morphology. Juvenile density of L. trabeculata was five times higher in the most harvesting-affected areas, while kelp morphology values, including holdfast diameter, number of stipes and total length, were always higher in the less-intensively harvested areas. Our study suggests that different degrees of protection can influence density and morphology of subtidal L. trabeculata populations, which in turn has important implications for the conservation of the kelp forest ecosystems and management of this important fishery.

Changes in the Market of Precious Wood: A Case Study of Submission System in Poland

A timber market occupies a very particular position within the economic reality. Trading of commodities such as precious timber is, indeed, strongly conditioned by the carrying capacity and the silvicultural potential of the forest ecosystem. Timber markets in Poland are characterized by a controlling position of the State Forests, and one of the possible forms of wood sale is the system of submission. A submission usually implies that small quantities of wood with unusual features are being offered to a specific group of customers. The paper presents the sale results and prices of veneer wood commercialized in submission systems and in other forms of timber sale in the territory of Krosno during the years 2000−2019. It is one of the oldest submission markets in Poland, where the most expensive log ever in Poland was sold (13,000 USD/log—close to 7000 USD/m3). The Regional Directorate of State Forest (RDSF) of Krosno is located in the south-eastern part of Poland and manages a forest area of approximately 400,000 hectares. Annual timber harvesting amounts to 2 million m3, of which less than 2000 m3 annually is allocated to the submissions. The data cover a 20-year continuous time series and allow tracing changes in the wood volume offered to the market, the species population structure, and price trends for individual species. The data are being discussed against the background of the economic situation and in relation to the average prices obtained from other methods of sale. Beech was the most sold, but the demands for oak and sycamore appeared to be particularly high during the period of observation. The unity prices can be very variable even for wood from the same species, especially for sycamore. The prices are generally demand-driven and show strong influences from furniture industries and fashion. A rising demand for high quality timber and logs of big dimensions has been noticed. The submission system results in substantial economic benefits for the forest management and the region as a whole.

Ionomic Responses of Local Plant Species to Natural Edaphic Mineral Variations.

Leaf ionome indicates plant phylogenetic evolution and responses to environmental stress, which is a critical influential factor to the structure of species populations in local edaphic sites. However, little is known about leaf ionomic responses of local plant species to natural edaphic mineral variations. In the present study, all plant species and soil samples from a total of 80 soil sites in Shiozuka Highland were collected for multi-elemental analysis. Ioniomic data of species were used for statistical analysis, representing 24 species and 10 families. Specific preferences to ionomic accumulation in plants were obviously affected by the phylogeny, whereas edaphic impacts were also strong but limited within the phylogenetic preset. Correlations among elements resulted from not only elemental synergy and competition but also the adaptive evolution to withstand environmental stresses. Furthermore, ionomic differences of plant families were mainly derived from non-essential elements. The majority of variations in leaf ionome is undoubtedly regulated by evolutionary factors, but externalities, especially environmental stresses also have an important regulating function for landscape formation, determining that the contributions of each factor to ionomic variations of plant species for adaptation to environmental stress provides a new insight for further research on ionomic responses of ecological speciation to environmental perturbations and their corresponding adaptive evolutions.

North-south and climate-landscape-associated pattern of population structure for the Atlantic Forest White Morpho butterflies

Atlantic Forest White Morpho butterflies, currently classified as Morpho epistrophus and M. iphitus, are endemic to the Atlantic Forest, where they are widely distributed throughout heterogeneous environmental conditions. Studies with endemic butterflies allow to elucidate questions on both patterns of diversity distribution and current and past processes acting on insect groups in this biodiversity hotspot. In the present study, we characterized one mtDNA marker (COI sequences) and developed 11 polymorphic loci of microsatellite for 22 sampling locations distributed throughout the entire Atlantic Forest domain. We investigated both the taxonomic limits of taxa classified as White Morpho and the structure and distribution of the genetic diversity throughout their populations. Genetic markers and distribution data failed to identify species diversification, population structure, or isolation among subpopulations attributed to different taxa proposed for the White Morpho, suggesting that the current distinction between two species is unreasonable. The Bayesian coalescent tree based on COI sequences also failed to recover monophyletic clades for the putative species, and pointed instead to a north–south oriented pattern of genetic structure, with the northern clade coalescing later than the southern clade. Northern samples also showed more intragroup structure than southern samples based on mtDNA data. Clustering tests based on microsatellites indicated the existence of three genetic clusters, with turnover between the states of Paraná and São Paulo. The north–south pattern found for the White Morpho populations is showed for the first time to a endemic AF insect and coincides with the two different bioclimatic domains previously described for vertebrates and plants. Population structure observed for these butterflies is related to climate- and landscape-associated variables, mainly precipitation and elevation.

Diversity, population structure and regeneration status of woody species in different habitats in Maun Educational Park, northern Botswana

ABSTRACT The diversity and population structure of woody species at Maun Educational Park (MEP) was investigated from June to July 2018. A total of 23, 18 and 30 quadrats of 20 × 20 m size were laid down at 50 m intervals along a transect line at riparian, seasonal floodplain and upland habitat, respectively. The Shannon diversity index and evenness were 1.87 and 1.54 in the riparian habitat, 2.01 and 0.77 in the seasonal floodplain habitat, 0.71 and 0.80 in the upland habitat. The species richness was 22, 14 and 19 in riparian, seasonal floodplain and upland habitat, respectively. The patterns of population structures of the woody species revealed that 32% and 21% of the woody species recorded in riparian and upland habitat, respectively, had a “reverse J-shaped” distribution, indicating a healthy or good regeneration. Vachellia tortilis and Combretum imberbe showed healthy regeneration in both riparian and upland habitat. Healthy regeneration in these species was attributable to their adaptive and defence mechanisms to herbivory. Most of the woody species showed either hampered seedling recruitment or hampered regeneration as a result of anthropogenic disturbance and herbivory. Almost all of the woody species (86%) in the seasonal floodplain habitat exhibited relatively good seedling recruitment and discontinued regeneration in the subsequent middle and higher diameter classes, suggesting that flooding inhibited regeneration of woody species.

Genetic structure and effective population size of Sydney rock oysters in eastern Australia

Oyster reef habitats are critical to coastal biodiversity and their decline has prompted restoration efforts in Australia. Knowledge gaps exist regarding the population structure and diversity of key species in these habitats. This may be critical information for the design of effective restoration programs. Sydney rock oysters (Saccostrea glomerata) are the dominant reef-forming bivalve in eastern Australia. Wild populations of S. glomerata have declined due to overharvesting, disease outbreaks, coastal development and reduced water quality. Here, we use genetic markers identified by genome-wide sequencing to investigate the genetic structure and diversity of wild Sydney rock oysters throughout their distribution in eastern Australia. We examine evidence for past population bottlenecks and spatial genetic structure associated with the East Australian Current. Analysis of 3, 400 neutral single-nucleotide polymorphisms (SNPs) revealed a single population, and an overlap with two other Saccostrea sp. at the northernmost boundary of the distribution. We detected signals of asymmetric gene flow consistent with the direction of the East Australian Current, and spatial structure patterns of limited genetic isolation by distance and spatial autocorrelation in the northern region (which experiences stronger effects of the East Australian Current) but not in the southern region of the distribution. We found no evidence of significant recent bottlenecks, with high effective population size throughout the species’ range. This information will provide a baseline against which to assess the impact of restoration projects, and guide strategies for sourcing stock for the enhancement of wild oyster populations. Our results provide a positive outlook for the resilience and adaptive capacity of Sydney rock oysters, and highlight wild populations as valuable resources for aquaculture and restoration initiatives.

Genetic assessment of captive red pandas (Ailurus fulgens) in American zoos to address management separation by putative subspecies.

Red pandas (Ailurus fulgens) are small charismatic mammals native across montane southern Asia, now endangered by human impacts. They are considered "living fossils" as the sole member of a distinct family, warranting higher conservation priority. Therefore, ex situ breeding programs were initiated to prevent extinction and act as genetic reservoirs for reintroduction, although complicated by apparent taxonomic subdivision. This study investigated whether the separation of captive red pandas in the North American Species Survival Plan® by putative subspecies was justified. A 383-bp segment of mitochondrial DNA control region was therefore sequenced from 67 members representing matriarchal lineages of both groups. A network analysis placed the 11 haplotypes found into separate but closely connected clusters, with one group more strongly related than the other. Statistical analyses and diversity indices corroborated differentiation between the two management units. Phylogenetic analyses employing multiple outgroups confirmed, although not robustly, reciprocal monophyly of the four- and seven-haplotype clades representing putative subspecies Ailurus fulgens fulgens and Ailurus fulgens styani, respectively. These empirical results are adequate to justify continued independent management of these zoo subpopulations, but cannot be definitive for taxonomic classification due to limited sampling from their native range. They will, however, be useful in evaluating long-term genetic diversity changes, focusing management efforts on newly revealed evolutionary limitations, and comparing with an assessment of wild red pandas to determine how representative zoo populations are for reintroduction purposes. Maintaining genetic diversity and population structure of endangered species is essential to protect evolutionary potential and adaptations for long-term sustainability.

Sex assignment in a non-model organism in the absence of field records using Diversity Arrays Technology (DArT) data

Conservation genomics research often relies on accurate sex information to make inferences about species demography, dispersal, and population structure. However, field determined sex data are not always available and can be subject to human error, while laboratory sex assignment methods such as PCR assays can often be costly and challenging for non-model species. Conservation genomics programs increasingly use reduced-representation genome sequencing to assess neutral and functional genetic diversity, population structure, gene flow and pedigrees in threatened species. Here we demonstrate that sex can be determined from reduced-representation sequencing data produced by the increasingly popular Diversity Arrays Technology sequencing workflow (DArT-seq) using a program originally designed for application to shotgun data. This program—sexassign—compares the “dosage” of sequencing reads mapping to autosomes versus the X chromosome. In the present study, sexassign was used to identify the sex of 60 field-collected Greater Stick-Nest Rat (Leporillus conditor) samples, despite the absence of an annotated reference genome for the species. This “read-dosage” approach is not only more accurate and affordable than traditional sex assignment methods, but can be applied to any diploid organism with a heterogametic sex determination system—including non-model and understudied species of conservation importance—by using FASTQs generated by DArT.

Sea ice decline drives biogeographical shifts of key Calanus species in the central Arctic Ocean.

In recent decades, the central Arctic Ocean has been experiencing dramatic decline in sea ice coverage, thickness and extent, which is expected to have a tremendous impact on all levels of Arctic marine life. Here, we analyze the regional and temporal changes in pan-Arctic distribution and population structure of the key zooplankton species Calanus glacialis and C. hyperboreus in relation to recent changes in ice conditions, based on historical (1993-1998) and recent (2007-2016) zooplankton collections and satellite-based sea ice observations. We found strong correlations between Calanus abundance/population structure and a number of sea ice parameters. These relationships were particularly strong for C. glacialis, with higher numbers being observed at locations with a lower ice concentration, a shorter distance to the ice edge, and more days of open water. Interestingly, early stages of C. hyperboreus followed the same trends, suggesting that these two species substantially overlap in their core distribution area in the Arctic Ocean. Calanus glacialis and C. hyperboreus have been historically classified as shelf versus basin species, yet we conclude that both species can inhabit a wide range of bottom depths and their distribution in the Arctic Ocean is largely shaped by sea ice dynamics. Our data suggest that the core distribution patterns of these key zooplankton are shifting northwards with retreating sea ice and changing climate conditions.

Temporal and spatial variation in population structure among brooding sea stars in the genus Leptasterias.

Temporal genetic studies of low‐dispersing organisms are rare. Marine invertebrates lacking a planktonic larval stage are expected to have lower dispersal, low gene flow, and a higher potential for local adaptation than organisms with planktonic dispersal. Leptasterias is a genus of brooding sea stars containing several cryptic species complexes. Population genetic methods were used to resolve patterns of fine‐scale population structure in central California Leptasterias species using three loci from nuclear and mitochondrial genomes. Historic samples (collected between 1897 and 1998) were compared to contemporary samples (collected between 2008 and 2014) to delineate changes in species distributions in space and time. Phylogenetic analysis of contemporary samples confirmed the presence of a bay‐localized clade and revealed the presence of an additional bay‐localized and previously undescribed clade of Leptasterias. Analysis of contemporary and historic samples indicates two clades are experiencing a constriction in their southern range limit and suggests a decrease in clade‐specific abundance at sites at which they were once prevalent. Historic sampling revealed a dramatically different distribution of diversity along the California coastline compared to contemporary sampling and illustrates the importance of temporal genetic sampling in phylogeographic studies. These samples were collected prior to significant impacts of Sea Star Wasting Disease (SSWD) and represent an in‐depth analysis of genetic structure over 117 years prior to the SSWD‐associated mass die‐off of Leptasterias.

Impact of disturbance on community structure, biomass and carbon stock in montane evergreen forests of Meghalaya, northeast India

Forest ecosystems play an important role in regulating global carbon cycle. There are very few studies on biomass and carbon (C) stock from the community managed montane evergreen forests of India. In the present study three traditional forests: Sacred forests (SF), Restricted forests (RF) and Village forests (VF) were studied to analyze the level of disturbance, species diversity, stand characteristics, biomass and C stock. In each forest a belt transect of 20 m wide and 250 m long (0.5 ha) was laid for enumeration of all woody individuals having a diameter at breast height (dbh) of ≥ 5 cm. Species richness, density, basal area and population structure varied between the traditional forest types. The aboveground biomass (AGB) was 273 ± 55.5 in the SF, 195 ± 32.12 in the RF and 75.3 ± 17.1 Mg ha−1 in the VF whereas, the corresponding belowground biomass (BGB) was 59.53 ± 8.4, 44.48 ± 7.5 and 19.9 ± 4.3 Mg ha−1, respectively. Overall, there was a 30% reduction of AGB in RFs and 70% in VFs as compared to the SFs. The mean AGBC stock was 129 ± 26.3, 92.49 ± 15.2 and 39 ± 5.7 Mg C ha−1 in SF, RF and VF. The BGBC ranged from a minimum of 6 to 34 Mg C ha−1 in the study sites. The AGB accumulation was greater in intermediate diameter classes (26 − 45.9 cm) in the RFs and VFs whereas in SFs the diameter class >65cm accounted to about 27-69% of the total AGB. Human disturbance had a strong influence on the species richness and stand characteristics that in turn influence the biomass and C stock in the community forests. It is emphasized that the village forests need to be provided with adequate protection for increasing the C storing potential.

Anthropogenic Pressure on Tree Species Diversity, Composition, and Growth of Balanites aegyptiaca in Dinder Biosphere Reserve, Sudan.

Anthropogenic disturbances, such as illegal harvesting and livestock browsing, often affect natural forests. However, the resulting tree species diversity, composition, and population structure have rarely been quantified. We assessed tree species diversity and importance value indices and, in particular, Balanites aegyptiaca (L.) Del. population structure, across 100 sample plots of 25 m × 40 m in disturbed and non-disturbed sites at the Dinder Biosphere Reserve, Sudan, from April 2019 to April 2020. We found that the tree species diversity in non-disturbed sites was more than double that of disturbed sites (p < 0.001, T = 32.6), and seedlings and saplings comprised more than 72% of the entire tree population (F2,48 = 116.4, p = 0.034; F2,48 = 163.2, p = 0.021, respectively). The tree density of B. aegyptiaca in the disturbed site was less than half that of the non-disturbed site (p = 0.018, T = 2.6). Balanites aegyptiaca was seven times more aggregated in disturbed sites compared to more regularly spaced trees in non-disturbed sites (T = 39.3 and p < 0.001). The poor B. aegyptiaca population status of the disturbed site shows that the conservation of this vulnerable species is essential for a sustainable management and utilization scheme.

A metapopulation model of social group dynamics and disease applied to Yellowstone wolves

The population structure of social species has important consequences for both their demography and transmission of their pathogens. We develop a metapopulation model that tracks two key components of a species' social system: average group size and number of groups within a population. While the model is general, we parameterize it to mimic the dynamics of the Yellowstone wolf population and two associated pathogens: sarcoptic mange and canine distemper. In the initial absence of disease, we show that group size is mainly determined by the birth and death rates and the rates at which groups fission to form new groups. The total number of groups is determined by rates of fission and fusion, as well as environmental resources and rates of intergroup aggression. Incorporating pathogens into the models reduces the size of the host population, predominantly by reducing the number of social groups. Average group size responds in more subtle ways: infected groups decrease in size, but uninfected groups may increase when disease reduces the number of groups and thereby reduces intraspecific aggression. Our modeling approach allows for easy calculation of prevalence at multiple scales (within group, across groups, and population level), illustrating that aggregate population-level prevalence can be misleading for group-living species. The model structure is general, can be applied to other social species, and allows for a dynamic assessment of how pathogens can affect social structure and vice versa.

SSR-based population structure, molecular diversity and identity cards of Ziziphus species from Pakistan and China

Research work on the genetic diversity within Pakistani and Chinese Ziziphus species is limited, and to date, no single report on the application of DNA barcoding attempt for identification of Ziziphus species is available in literature. Therefore, the current study was designed to assess diversity and relationships among Ziziphus species genotypes and to develop a unique identity card and for their conservation. The study has used 99 simple sequence repeats (SSR) markers for gaining insights into the genetic diversity within 200 genotypes of four Ziziphus species. Successful amplification was achieved with 59 SSRs; and was applied for understanding the population structure and relationships among the Ziziphus species/genotypes. Unique SSR fingerprints of three highly polymorphic loci were used for developing molecular identity cards for each genotype. A total of 158, 165, 168, 157 and 168 alleles were amplified from Z. jujuba Mill., Z. nummularia (Burm.f.) Wight & Arn., Z. oxyphylla Edgew. (Pakistani origin), Z. mauritiana Lam. and Z. jujuba Mill., (Chinese origin) respectively. Alleles per locus ranged from 2 to 6, averaging 2.83, 2.82, 3.366, 2.80 and 3.09. Analysis of molecular variance (AMOVA) revealed high genetic variability (83%) whereas; fixation index (0.014) and gene flow estimates (1.32) indicated frequent gene flow within Ziziphus species. STRUCTURE and PCA analysis resolved all genotypes into five populations. Further, molecular identity cards were developed for all genotypes. The overall results indicated prevalence of genetic variability and relationships among Ziziphus species; yet the same Z. jujuba species across geographical boundaries has retained unique alleles and this may facilitate development of agronomically desirable and genetically improved Ziziphus cultivars.

Contrasting patterns of population structure in commercially fished sawsharks from southern Australian waters

In the waters of southeast Australia, two species of sawshark—the common (Pristiophorus cirratus) and southern (Pristiophorus nudipinnis) sawshark—are frequent by-catch in commercial fisheries. While harvesting of both species is currently considered sustainable, there has been no investigation of whether P. cirratus and P. nudipinnis display genetically distinct populations throughout their ranges. Such information is necessary for effective management of these species in commercial fisheries. This study examined population structure in both sawshark species through analysis of two mitochondrial genes: cytochrome b (Cyt-b) and NADH dehydrogenase subunit 5 (ND5). Results indicated contrasting levels of population structure, with P. cirratus consisting of two, possibly three, genetically distinct populations with two mitochondrial lineages and P. nudipinnis consisting of a single population. Tests for population expansion also highlighted differences between the two species. Population expansion was detected for the entire P. nudipinnis population, whereas this was only the case for one mitochondrial lineage in P. cirratus. The entire P. cirratus population displayed signals of demographic stability. It is hypothesised that the opening and closing of Bass Strait during glacial-interglacial cycles played a major role in shaping the population structure and expansion signatures observed in this study. Mitochondrial data also suggest that patterned and uniform brown P. cirratus are the same species. Fisheries managers should consider adopting two management units in southern Australia—one along the east coast (for the eastern P. cirratus population) and one along the south coast (for the southern P. cirratus population and the single P. nudipinnis population).

Using gradient Forest to predict climate response and adaptation in Cork oak.

Climate change is impacting locally adapted species such as the keystone tree species cork oak (Quercus suber L.). Quantifying the importance of environmental variables in explaining the species distribution can help build resilient populations in restoration projects and design forest management strategies. Using landscape genomics, we investigated the population structure and ecological adaptation of this tree species across the Mediterranean Basin. We applied genotyping by sequencing and derived 2,583 single nucleotide polymorphism markers genotyped from 81 individuals across 17 sites in the studied region. We implemented an approach based on the nearest neighbour haplotype 'coancestry' and uncovered a weak population structure along an east-west climatic gradient across the Mediterranean region. We identified genomic regions potentially involved in local adaptation and predicted differences in the genetic composition across the landscape under current and future climates. Variants associated with temperature and precipitation variables were detected, and we applied a nonlinear multivariate association method, gradient forest, to project these gene-environment relationships across space. The model allowed the identification of geographic areas within the western Mediterranean region most sensitive to climate change: south-western Iberia and northern Morocco. Our findings provide a preliminary assessment towards a potential management strategy for the conservation of cork oak in the Mediterranean Basin.

Suspended particulate matter is a key factor shaping the spatial arrangement of Micropogonias furnieri (sciaenidae) population in a Southwestern Atlantic temperate estuary

The relative influence of suspended particulate matter (SPM), sea surface temperature, depth, and type of bottom sediment in the spatial distribution of the Micropogonias furnieri (Sciaenidae) population structure was studied in the Río de la Plata estuary. Eight size-assemblages were defined (Cluster Analysis) showing a significant association with environmental variables. The application of the Boosted Regression Trees model for presence/absence and relative abundance showed that the SPM (46.24% and 34.24%, respectively), followed by the depth (31.47% and 33.50%, respectively) were the most important environmental variable in predicting the spatial distribution. Results showed a population segregation pattern. Juvenile and small adolescent fish increased their probability of occurrence and their relative abundance with increments of SPM and decrease of depth. The large adolescent and adult fish substantially increased their occurrence and relative abundance with the decreasing of SPM concentrations at low values. This study quantified and showed the high importance of the SPM in the spatial distribution pattern of the population structure of an estuarine species. In this context, it proposed that the SPM in the Río de la Plata could be used as an indicator of habitat availability of juveniles/adults within an ecosystem approach for fisheries management.

Characterization, fungicide sensitivity and efficacy of Colletotrichum spp. from chili in Fujian, China

Chili (Capsicum frutescens L.) is an important vegetable crop worldwide because of its abundant vitamins and high capsaicin and capsochrome levels. We collected samples of chili anthracnose in different parts of Fujian Province, China, during 2017–2018. The disease incidence reached 80–90% in severely diseased fields, from which 106 isolates were isolated. The morphological characteristics of the isolates were observed and compared, and a multilocus phylogenetic analysis (ITS, ACT, GAPDH, TUB2 and CHS-1) was performed using representative isolates. Four Colletotrichum species were identified: C. fructicola, C. truncatum, C. aenigma and C. scovillei. Of these, C. aenigma was reported for the first time from chili fruit in Fujian, China. Pathogenicity was confirmed by fulfilling Koch's postulates. All of the isolates obtained were sensitive to pyraclostrobin, pyraclostrobin + salicylhydroxamic acid (SHAM) and difenoconazole based on mycelial growth inhibition (EC50 values of 0.1722–0.9783, 0.0978–0.7785 and 0.1792–2.6672 μg/mL, respectively). In addition, pyraclostrobin, difenoconazole and pyraclostrobin + difenoconazole showed good preventive efficacy against four Colletotrichum species in greenhouse trials. In summary, this study has great importance for understanding the population structure of Colletotrichum species causing anthracnose in chili in Fujian, China, and provides useful information for the effective control of the disease in the field.

Spatial Genetic Structure and Demographic History of the Dominant Forest Oak Quercus fabri Hance in Subtropical China.

Oak trees (Quercus L.) are important models for estimating abiotic impacts on the population structure and demography of long life span tree species. In this study, we generated genetic data for 17 nuclear microsatellite loci in 29 natural populations of Quercus fabri to estimate the population genetic structure. We also integrated approximate Bayesian computation (ABC) and ecological niche analysis to infer the population differentiation processes and demographic history of this oak species. The genetic analyses indicated two genetic clusters across the 29 populations collected, where most approximately corresponded to the intraspecific differentiation among populations from western and eastern China, whereas admixed populations were mainly found in central mountains of China. The best model obtained from hierarchical ABC simulations suggested that the initial intraspecific divergence of Q. fabri potentially occurred during the late Pliocene (ca. 3.99 Ma) to form the two genetic clusters, and the admixed population group might have been generated by genetic admixture of the two differentiated groups at ca. 53.76 ka. Ecological analyses demonstrated clear differentiation among the Q. fabri population structures, and association estimations also indicated significant correlations between geography and climate with the genetic variation in this oak species. Our results suggest abiotic influences, including past climatic changes and ecological factors, might have affected the genetic differentiation and demographic history of Q. fabri in subtropical China.