Significant Spatial Structure Research Articles

Characteristics of the urban environmental regulation network and its impact on carbon emission efficiency in China

On the basis of 2007–2019 data covering 254 cities in China, we analyze the overall and individual characteristics of the environmental regulation network (ERN) using a modified gravity model and social network analysis (SNA) method and investigate the effect of the degree centrality of the EGN on carbon emission efficiency (CEE). The results suggest that, first, China’s municipal environmental regulations exhibit a significant and complex spatial correlation structure. However, the cities are not connected well to each other, resulting in a loose network structure. Second, cities in the Yangtze River Delta, such as Wuxi, Suzhou, and Shanghai, occupy the center of the network, and the degree centrality of approximately 20% of the cities exceeds the average level. Third, the degree centrality of the ERN increases CEE significantly, but its direction and intensity differ significantly according to geographical location, resource endowment and urban size. Fourth, degree centrality improves CEE by reducing the energy intensity of cities. Green innovation and foreign direct investment can strengthen the positive effect of degree centrality on CEE. Degree centrality enhances the CEE of a region but reduces the CEE of neighboring cities through the spatial spillover effect. Therefore, we should focus on promoting low-carbon and green lifestyles, formulate carbon reduction regulations tailored to local conditions, encourage enterprises to apply green technologies, and strengthen cooperation between cities.

Temporal changes in spatial scale and autocorrelation structure of forest openings based on taxonomic, phylogenetic, and functional turnover

ContextDuring European settlement, Illinois grasslands were converted for agricultural purposes. Remaining natural areas in southern Illinois include natural xeric forest openings, with communities representative of remnant grasslands and adjacent hardwood forests. Previous research in these openings shows plant communities are driven by edaphic conditions. ObjectivesThe first objective aimed to characterize spatial scale and autocorrelation structure of these openings based on climatic, environmental, and diversity variables. The second objective was to predict taxonomic, phylogenetic, and functional turnover between 1988 and 2019, using climatic and environmental variables. MethodsSurveys were conducted to calculate taxonomic, phylogenetics and functional trait metrics and analyses of these dimensions of diversity. Randomization tests were used to assess phylogenetic and functional clustering and over-dispersion at each site. Spatially-explicit climatic and environmental variables were included from earlier surveys and data repositories. Global Moran's I and spatial autocorrelograms were used to assess spatial structure of climatic, environmental, and diversity variables and generalized dissimilarity modeling was used to characterize taxonomic, phylogenetic, and functional turnover based on environmental variables. ResultsSoil depth was the only environmental variable which exhibited significant global spatial autocorrelation. Overall, sandstone sites were phylogenetically over-dispersed while loess sites were phylogenetically clustered. Climate variables and diversity metrics exhibited significant spatial structure during surveys. Generalized dissimilarity models showed that geographic distance between openings was the most influential driver of turnover across surveys. ConclusionsPrevious glacial events explained the spatial structure of soil depth across sites, due to Quaternary loess deposition in loess sites. High diversity values were clustered in the southeastern portions of the study area. Functional generalized dissimilarity models best predicted turnover in these openings compared to taxonomic and phylogenetic models.

Genetic composition of green sea turtles (Chelonia mydas) at coastal feeding areas of Uruguay

The highly migratory and marine nature of species such as green sea turtles (Chelonia mydas) may hinder understanding of basic life history and impact ensuing management and conservation applications across their full range. To elucidate the linkages between juvenile green turtles foraging in coastal waters of Uruguay in the Southwestern Atlantic Ocean to their future nesting or feeding grounds, this study investigated their genetic composition . A total of 201 tissue samples were collected from turtles that had stranded or were intentionally captured for scientific research along the Uruguayan coast (ca. 33°–35°S) during two sampling periods (2003–2005 and 2009–2014). Samples were pooled for analysis. Twelve mitochondrial control region haplotypes and ten subhaplotypes were identified, all of which had been previously detected at Atlantic or Caribbean nesting beaches. Mixed Stock Analysis revealed that most turtles traced to the Ascension Island rookery, representing a substantial connection to the remote mid-Atlantic island thousands of kilometers distant. Other nesting areas, such as Guinea Bissau in Africa and Trindade Island in Brazil, represented less significant sources. There was no significant temporal or spatial genetic structure within Uruguayan waters, suggesting dispersion along this coast. Despite the geographic distance from the nesting beach, the significant connection to the Ascension Island rookery underscores the importance of considering rookery population size and ocean current influences in understanding source contributions. These findings emphasize the need for conservation efforts, including the maintenance of existing protected areas and the creation of new ones, to ensure the long-term conservation of green turtles connected to various nesting colonies and feeding grounds.

Genetic resources of common ash (Fraxinus excelsior L.) in Poland

BackgroundKnowledge of genetic structure and the factors that shape it has an impact on forest management practices. European ash (Fraxinus excelsior L.) has declined dramatically throughout its range as a result of a disease caused by the fungus Hymenoscyphus fraxineus. Despite the need for conservation and restoration of the species, genetic data required to guide these efforts at the country level are scarce. Thereofore, we studied the chloroplast and nuclear genetic diversity of 26 natural common ash populations (1269 trees) in Poland.ResultsChloroplast polymorphisms grouped the populations into two geographically structured phylogenetic lineages ascribed to different glacial refugia (the Balkans and the Eastern Alps). However, the populations demonstrated high genetic diversity (mean AR = 12.35; mean Ho = 0.769; mean He = 0.542) but low differentiation based on nuclear microsatellites (FST = 0.045). Significant spatial genetic structure, consistent with models of isolation by distance, was detected in 14 out of 23 populations. Estimated effective population size was moderate-to-high, with a harmonic mean of 57.5 individuals per population.ConclusionsGenetic diversity was not homogeneously distributed among populations within phylogenetic gene pools, indicating that ash populations are not equal as potential sources of reproductive material. Genetic differences among populations could be related to their histories, including founder effects or gene flow between evolutionary lineages (admixture). Our results suggest that ash stands across Poland could be treated as two main management units (seed zones). Therefore, despite the homogenizing effect of pollen gene flow known for this species, the genetic structure should be taken into account in the management of the genetic resources of the common ash. Although ash dieback poses an additional challenge for the management of genetic resources, efforts should be directed towards protecting populations with high genetic diversity within defined phylogenetic units, as they may be an important source of adaptive variation for future stands.

Factors determining fine-scale spatial genetic structure within coexisting populations of common beech (Fagus sylvatica L.), pedunculate oak (Quercus robur L.), and sessile oak (Q. petraea (Matt.) Liebl.)

Key messageNaturally regenerating populations of common beech, pedunculate, and sessile oaks develop strong spatial genetic structures at adult and seedling stages. Significant genetic relationship occurs between individuals growing up to 60 m apart. This indicates the minimum distance separating trees from which seeds used for reforestation should be harvested to avoid the adverse effects of excessive relatedness among offspring.ContextSpatial genetic structure is an inherent characteristic of naturally regenerating plant populations and has practical implications in forests for the management of genetic resources.AimsWe investigated the extent of spatial genetic structure in three broad-leaved forest tree species (common beech—Fagus sylvatica L.; pedunculate oak—Quercus robur L.; and sessile oak—Q. petraea (Matt.) Liebl.) coexisting in the same nature reserve, explored its variation among species and different life stages (adults/offspring), and tested its possible determinants.MethodsWe explored patterns of spatial distribution of individuals, and using microsatellites, we estimated parameters of spatial genetic structure based on kinship relationships, considering possible sources of variation.ResultsIn adults, the strongest spatial genetic structure was found for Q. petraea (Sp = 0.0187), followed by F. sylvatica (Sp = 0.0133), and the weakest in Q. robur (Sp = 0.0080). It was uniform across different age classes in pedunculate oak but decreased with age in sessile oak. No apparent relationship between age and spatial genetic structure was found in beech. Offspring exhibited significant spatial genetic structure (ranging from 0.0122 in beech to 0.0188 in sessile oak). The cohorts of seedlings having both parents present within the study site had stronger spatial genetic structures than cohorts of seedlings with only one local parent.ConclusionSpatial genetic structure is strong in naturally regenerating populations of heavy-seeded forest trees. Pollen immigration from outside of a local forest stand can significantly decrease the extent of spatial genetic structure in offspring generations.

Genetic inference of orchid colonization of a Costa Rican lava flow

AbstractThe dispersal and colonization of plant populations allow species to occupy novel habitats, migrate, and undergo range shifts in response to changing environmental factors and, as such, are fundamental ecological processes for ensuring the long‐term persistence of species. Natural landscape disturbance often generates habitats available for colonization. Patterns of colonization and population expansion can be inferred from the levels and partitioning of genetic variation of plant populations with known disturbance histories, such as recent volcanic eruptions. We sampled and mapped 496 individuals from two populations of the colonizing terrestrial orchid, Sobralia chrysostoma, on the 1992 lava flow of Volcán Arenal in central Costa Rica. We used neutral co‐dominant markers to genotype individuals and estimate population genetic statistics. Both populations had high mean levels of genetic diversity (P = 100%; AP = 3.31; He = 0.259) suggesting that the lava flow was colonized by numerous individuals that likely originated from multiple source populations. However, significant spatial genetic structure (SGS) was only present in one population at the smallest distance class (≤2 m) and was low (r = 0.032). That these large and genetically diverse populations had such low SGS and an absence of SGS, respectively is contrary to expectations and differs significantly from the pattern in Epidendrum radicans (Orchidaceae), with which S. chrysostoma is growing sympatrically. Our results suggest that these two populations either consist primarily of immigrant individuals or that seeds produced in situ dispersed over longer distances, thereby producing larger seed shadows and greater overlap of seed shadows.

Genomic, Phenotypic, and Ecological Data Provide Decisive Support for Multiple Species in the Seriphium plumosum Complex (Gnaphalieae: Asteraceae)

Parallel advances in next-generation sequencing and the development of analytical tools that use sequence data from multiple, unlinked loci have, over the past decade, shifted species discovery and delimitation firmly into the genomic sphere. While most recent analytical applications are underpinned by the Multi-Species Coalescent (MSC), the assumption that species conform to Wright-Fisher populations compromises the ability of this model to resolve species which are loosely knit, metapopulation-like entities that display significant spatial genetic structure. In this paper, we therefore employ a suite of analytical methods (MSC-based species discovery, DISSECT/STACEY; sparse Non-negative Matrix Factorisation, sNMF; discriminant analysis of principal components, DAPC) to thousands of massively parallel-sequenced loci, generated via Genotyping-by-Sequencing, for the purpose of resolving metapopulation-like species in the taxonomically recalcitrant Seriphium plumosum L. (Asteraceae; Gnaphalieae) species complex. These methods are complementary in illuminating different characteristics of the entities being resolved (e.g., monophyly, gene pool exclusivity) and so testing different aspects of a species hypothesis. In our study, these methods display remarkable congruence in terms of the groups they reveal, together yielding a set of 12 consensus population clusters which correspond to putative taxonomic species. Using linear discriminant analyses and tests of isolation-by-distance, we further assess whether these entities are phenotypically and ecologically distinct and, where possible, whether they describe a common spatial field of gene exchange. Based on our results, we find evidence of at least eight independent species in the S. plumosum complex, most of which are not truly cryptic, and at least five of which maintain their genetic distinctness in sympatry and so qualify as biological species. Our findings corroborate previous work suggesting a need for diverse tools to properly circumscribe the species-level diversity of South Africa’s Cape flora.

Ocean connectivity and habitat characteristics predict population genetic structure of seagrass in an extreme tropical setting

AbstractUnderstanding patterns of gene flow and processes driving genetic differentiation is important for a broad range of conservation practices. In marine organisms, genetic differentiation among populations is influenced by a range of spatial, oceanographic, and environmental factors that are attributed to the seascape. The relative influences of these factors may vary in different locations and can be measured using seascape genetic approaches. Here, we applied a seascape genetic approach to populations of the seagrass, Thalassia hemprichii, at a fine spatial scale (~80 km) in the Kimberley coast, western Australia, a complex seascape with strong, multidirectional currents greatly influenced by extreme tidal ranges (up to 11 m, the world's largest tropical tides). We incorporated genetic data from a panel of 16 microsatellite markers, overwater distance, oceanographic data derived from predicted passive dispersal on a 2 km‐resolution hydrodynamic model, and habitat characteristics from each meadow sampled. We detected significant spatial genetic structure and asymmetric gene flow, in which meadows 12–14 km apart were less connected than ones 30–50 km apart. This pattern was explained by oceanographic connectivity and differences in habitat characteristics, suggesting a combined scenario of dispersal limitation and facilitation by ocean current with local adaptation. Our findings add to the growing evidence for the key role of seascape attributes in driving spatial patterns of gene flow. Despite the potential for long‐distance dispersal, there was significant genetic structuring over small spatial scales implicating dispersal and recruitment bottlenecks and highlighting the importance of implementing local‐scale conservation and management measures.

ISSR-assisted spatial genetic structure, population admixture, and biodiversity estimates across locally adopted saffron ecotypes from 18 different provenances of Iran

Here, genetic variability and spatial genetic structure patterns governing on a 90-sample collection of Iranian saffron ecotype gathered from 18 provenances were scrutinized using 20 ISSR markers. 17 out of 20 ISSR primers exhibited polymorphism with 130 polymorphic amplicons from 4 to 15 bands per primer, with an average of 7.647. Considering maximum values of PIC (0.37), discrimination power (D; 0.71), and expected heterozygosity (H; 0.497), both ISSR-7 and ISSR-9 primers were nominated to generate maximal discrimination and heterozygosity. Based on phylogenetic tree and PCoA, the ecotypes were classified into two major groups, but inconsistent with the geographical distribution. Similarly, via applying Bayesian population structure clustering, two sub-populations (K = 2) were observed, four ecotypes were admixture (Q < 0.70), and the rest were pure ecotypes (Q ≥ 0.70). Sub-population 1 was less genetically diverse (FST = 0.1658) than sub-population 2 (FST = 0.5593). As to AMOVA, 56.563% and 43.436% of total genetic variation were partitioned into inter- and intra-population variation, respectively. Based on spatial PCA (sPCA), robust signals of “global” and “local” structures were recognized, only the former was statistically significant (p < 0.001). Significant IBD patterns were also observed via Mantel test calculated between original/unbiased Nei’s genetic distances and geographic distances (p < 0.001) across full dataset. The results revealed ISSR capabilities in saffron DNA fingerprinting and biodiversity assessment, moderate-high genetic variability alongside significant global spatial genetic structure among saffron ecotypes, followed by low levels of gene flow (Nm = 0.2801) and admixture patterns.

Analysis on the Influence of Industrial Structure on Energy Efficiency in China: Based on the Spatial Econometric Model.

Compared with other developed countries, China's energy efficiency level is not optimal, but it has indeed made remarkable achievements in its long-term development, mainly due to efforts targeting the adjustment of industrial structure. This research, therefore, uses a spatial econometric model to study the energy efficiency of 30 provinces in China with data from the panel from 2004 to 2019, and studies the impact of industrial structure on energy efficiency from the overall sample, for different time periods and across the three regional scales of eastern, central and western regions. The following conclusions are drawn from the empirical analysis. (1) China's energy efficiency indicators have significant geographic spatial correlation and regional spatial structure differences. (2) In the full sample condition, the industrial structure has a positive impact on the energy efficiency of China's provinces, but it also shows a significant negative spatial spillover effect. (3) Industrial structure was positively correlated with energy efficiency from 2004 to 2011. (4) The industrial structure in the east promotes energy efficiency, while the industrial structure in the central and western regions inhibits energy efficiency improvement. (5) Government intervention and scientific and technological innovation have had a spatial impact on energy efficiency in China's provinces, while marketization and the average income of residents have had no significant impact.

(Not) far from home: No sex bias in dispersal, but limited genetic patch size, in an endangered species, the Spotted Turtle (Clemmys guttata).

Sex-biased dispersal is common in many animals, with male-biased dispersal often found in studies of mammals and reptiles, including interpretations of spatial genetic structure, ostensibly as a result of male-male competition and a lack of male parental care. Few studies of sex-biased dispersal have been conducted in turtles, but a handful of studies, in saltwater turtles and in terrestrial turtles, have detected male-biased dispersal as expected. We tested for sex-biased dispersal in the endangered freshwater turtle, the spotted turtle (Clemmys guttata) by investigating fine-scale genetic spatial structure of males and females. We found significant spatial genetic structure in both sexes, but the patterns mimicked each other. Both males and females typically had higher than expected relatedness at distances <25 km, and in many distance classes greater than 25 km, less than expected relatedness. Similar patterns were apparent whether we used only loci in Hardy-Weinberg equilibrium (n=7) or also included loci with potential null alleles (n=5). We conclude that, contrary to expectations, sex-biased dispersal is not occurring in this species, possibly related to the reverse sexual dimorphism in this species, with females having brighter colors. We did, however, detect significant spatial genetic structure in males and females, separate and combined, showing philopatry within a genetic patch size of <25 km in C.guttata, which is concerning for an endangered species whose populations are often separated by distances greater than the genetic patch size.

Spatio-Temporal Modelling Informing Wolbachia Replacement Releases in a Low Rainfall Climate.

Simple SummaryAedes aegypti is a mosquito that is responsible for spreading viral diseases including dengue fever, Zika, and chikungunya. Disease spread can be reduced by releasing mosquitoes containing bacteria known as Wolbachia, which inhibit transmission. Before such releases, it is important to collect data about where Ae. aegypti occur in urban landscapes and how populations vary over space and time. In this study, we present a pre-release analysis of mosquito populations using ovitraps (traps that provide a substrate for female mosquitoes to lay eggs), in Jeddah, Saudi Arabia. Our study contains a number of important findings. Firstly, we showed that there was no difference in the numbers of eggs laid between basement and non-basement locations. Secondly, we showed that, for some study sites, there was significant spatial structure to populations, meaning that where numbers of eggs were high (or low) they tended to remain high (or low) on average for many hundreds of meters. We also found that when mosquitoes are present in an area during the dry season, they tend to remain into the wet season; however, regions of high egg production could change between seasons. This suggests that in Jeddah’s arid environment, the quality of breeding environments is inconsistent over time.Releases of Aedes aegypti carrying Wolbachia bacteria are known to suppress arbovirus transmission and reduce the incidence of vector-borne diseases. In planning for Wolbachia releases in the arid environment of Jeddah, Saudi Arabia, we collected entomological data with ovitraps across a 7-month period in four locations. Herein, we show that mosquito presence in basements does not differ from that of non-basement areas of buildings. In modelling mosquito presence across the study sites, we found the spatial structure to be statistically significant in one of the four sites, while a significant spatial structure was found for egg production data across three of the four sites. The length scales of the spatial covariance functions fitted to the egg production data ranged from 143 m to 574 m, indicating that high productivity regions can be extensive in size. Rank-correlation analyses indicated that mosquito presence tended to persist from the dry to wet season, but that egg production ranks at locations could reverse. The data suggest that, in Jeddah, the quality of the local environment for breeding can vary over time. The data support the feasibility of dry season releases but with release numbers needing to be flexible depending on local rates of invasion.

Spatiotemporal dynamics of genetic variation at the quantitative and molecular levels within a natural Arabidopsis thaliana population

Abstract Evolutionary change begins at the population scale. Therefore, understanding adaptive variation requires the identification of the factors maintaining and shaping standing genetic variation at the within‐population level. Spatial and temporal environmental heterogeneity represent ecological drivers of within‐population genetic variation, determining the evolutionary trajectory of populations along with random processes. Here, we focused on the effects of spatiotemporal heterogeneity on quantitative and molecular variation in a natural population of the annual plant Arabidopsis thaliana. We sampled 1093 individuals from a Spanish A. thaliana population across an area of 7.4 ha for 10 years (2012–2021). Based on a sample of 279 maternal lines, we estimated spatiotemporal variation in life‐history traits and fitness from a common garden experiment. We genotyped 884 individuals with nuclear microsatellites to estimate spatiotemporal variation in genetic diversity. We assessed spatial patterns by estimating spatial autocorrelation of traits and fine‐scale genetic structure. We analysed the relationships between phenotypic variation, geographical location and genetic relatedness, as well as the effects of environmental suitability and genetic rarity on phenotypic variation. The common garden experiment indicated that there was more temporal than spatial variation in life‐history traits and fitness. Despite the differences among years, genetic distance in ecologically relevant traits (e.g. flowering time) tended to be positively correlated to genetic distance among maternal lines, while isolation by distance was less important. Genetic diversity exhibited significant spatial structure at short distances, which were consistent among years. Finally, genetic rarity, and not environmental suitability, accounted for genetic variation in life‐history traits. Synthesis. Our study highlighted the importance of repeated sampling to detect the large amount of genetic diversity at the quantitative and molecular levels that a single A. thaliana population can harbour. Overall, population genetic attributes estimated from our long‐term monitoring scheme (genetic relatedness and genetic rarity), rather than biological (dispersal) or ecological (vegetation types and environmental suitability) factors, emerged as the most important drivers of within‐population structure of phenotypic variation in A. thaliana.

Large-scale genetic structure of Quercus robur in its eastern distribution range enables assignment of unknown seed sources

Abstract Pedunculate oak is seen as an alternative to other tree species for reforestation and mitigation programs in the face of climate change. Thus, the identification of suitable, well-adapted seed sources is of high priority. We perform a genetic inventory on 970 trees from 97 locations in Russia, Belarus, Ukraine and Latvia representing the eastern part of the natural species range. All samples were screened with a set of 348 gene markers covering the nuclear (n = 327) and the organelle genomes (chloroplast: n = 14, mitochondria: n = 7) using a genotyping-by-sequencing method. We identified 10 plastidial haplotypes, which showed a strong spatial pattern with a highly significant autocorrelation up to a range of 600 km. After excluding 47 potentially selected markers, significant spatial genetic structure up to 800 km was also observed at the selectively neutral nuclear loci. Bayesian clustering analysis indicated a sub-division into two gene pools present at all locations but with a shift of proportion from West to East. The genetic diversity was negatively correlated with longitude, showing higher values in the West and Centre and lower values at the northern, eastern and southeastern edges of the natural distribution range. We sub-divided the sampled area into six geographic regions and used the genetic composition of all samples in each region as a genetic reference for assignment tests. Self-assignment of groups of 10 individuals to their region of origin showed an average assignment success of 93 per cent. Samples of three artificial plantations of pedunculate oak in Siberia could be clearly assigned to the East–North and Centre–South regions. We discuss the implications of our results for the forest practice and in particular the proofing of seed sources.

Limited-Distance Pollen Dispersal and Low Paternal Diversity in a Bird-Pollinated Self-Incompatible Tree.

Bird pollination in Asia is regarded as an uncommon phenomenon and, therefore, only a few investigations on mating pattern and paternity in fruits of Asian bird-pollinated plants have been conducted. Here, we examined spatial genetic structure, pollen dispersal, and multiple paternity in a natural population of Bombax ceiba (B. ceiba) (Malvaceae) in Hainan Island, South China, using simple sequence repeat (SSR) markers. A low genetic diversity (He = 0.351 ± 0.0341 and 0.389 ± 0.043, respectively, for adults and offspring) and bottleneck effects were observed. Genetic kinship was significant within 400 m or in 1,800–3,800 m. Both the mating pattern and paternity analysis confirmed obligate xenogamy and a low multiple paternity in B. ceiba. There was a strongly negative relationship between the frequency of matings and the distance between mating pairs. The average pollen dispersal distance was 202.89 ± 41.01 m (mean ± SE) and the farthest distance of > 1 km was recorded. Realized mating events showed an extremely leptokurtic distribution within 1,200 m, suggesting that the pollen dispersal distance was consistent with the optimal foraging theory of generalist birds such as Zosterops spp. and Pycnonotus spp. Paternity per tree ranged from two to six and the average effective number of pollen donors per maternal plant was 3.773, suggesting a low level of paternity diversity as compared to other bird-pollinated plants. We concluded that optimal foraging behavior by generalist birds could explain the leptokurtic pollen dispersal distribution and predominantly near-neighbor matings in B. ceiba. The limited pollen dispersal distance and low multiple paternity were consistent with low fruit setting rate (3.27 ± 0.93%) in this self-incompatible tree, which was caused mainly by the restricted flight distance of birds and human disturbances. Low genetic diversity and significant spatial genetic structure might have largely resulted from logging and human collection of fruits.

How Does the Spatial Structure of High-Speed Rail Station Areas Evolve? A Case Study of Zhengzhou East Railway Station, China

The rapid development of high-speed rail (HSR) and station areas has shortened the spatial and temporal distances among cities, improved the accessibility of cities, and affected the spatial agglomeration and diffusion of populations and of social and economic activities. This has led to spatial reconfiguration of production factors within cities, which has the potential to drive the reconstruction of urban spatial structures. Based on POI and land-use data, this paper defines the spatial scope of the HSR station area and explores the characteristics and influencing factors of its spatial structure from the perspective of industry. The study area i is set at 2000 m. Since the opening of the HSR, the industrial distribution has exhibited a significant circular, multi-core, and axial belt spatial structure. The spatial structure of each sub-industry is different. On the whole, internal and external transport and agglomeration economies have significant impacts on the industrial spatial distribution, and land rent has gradually decreased in importance with the development of HSR station areas. The intensity of the effects of different factors varies among different industries. The mechanisms by which the spatial structure of the station area is formed are discussed and include location accessibility, micro-market factors, node station attributes, the availability of a sufficient amount of undeveloped land, the characteristics and needs of HSR passengers, and policies and systems.

Impact of Gene Flow and Introgression on the Range Wide Genetic Structure of Quercus robur (L.) in Europe

As for most other temperate broadleaved tree species, large-scale genetic inventories of pedunculate oak (Quercus robur L.) have focused on the plastidial genome, which showed the impact of post-glacial recolonization and manmade seed transfer. However, how have pollen mediated gene flow and introgression impacted the large-scale genetic structure? To answer these questions, we did a genetic inventory on 1970 pedunculate oak trees from 197 locations in 13 European countries. All samples were screened with a targeted sequencing approach on a set of 381 polymorphic loci (356 nuclear SNPs, 3 nuclear InDels, 17 chloroplast SNPs, and 5 mitochondrial SNPs). In a former analysis with additional 1763 putative Quercus petraea trees screened for the same gene markers we obtained estimates on the species admixture of all pedunculate oak trees. We identified 13 plastidial haplotypes, which showed a strong spatial pattern with a highly significant autocorrelation up to a range of 1250 km. Significant spatial genetic structure up to 1250 km was also observed at the nuclear loci. However, the differentiation at the nuclear gene markers was much lower compared to the organelle gene markers. The matrix of genetic distances among locations was partially correlated between nuclear and organelle genomes. Bayesian clustering analysis revealed the best fit to the data for a sub-division into two gene pools. One gene pool is dominating the west and the other is the most abundant in the east. The western gene pool was significantly influenced by introgression from Quercus petraea in the past. In Germany, we identified a contact zone of pedunculate oaks with different introgression intensity, likely resulting from different historical levels of introgression in glacial refugia or during postglacial recolonization. The main directions of postglacial recolonization were south to north and south to northwest in West and Central Europe, and for the eastern haplotypes also east to west in Central Europe. By contrast, the pollen mediated gene flow and introgression from Q. petraea modified the large-scale structure at the nuclear gene markers with significant west–east direction.

Geography-Driven Evolution of Potato Virus A Revealed by Genetic Diversity Analysis of the Complete Genome.

Potato virus A (PVA), a member of the genus Potyvirus, is an important potato pathogen that causes 30%–40% yield reduction to global potato production. Knowledge on the genetic structure and the evolutionary forces shaping the structure of this pathogen is limited but vital in developing effective management strategies. In this study, we investigated the population structure and molecular evolution of PVA by analyzing novel complete genomic sequences from Chinese isolates combined with available sequences from Europe, South America, Oceania, and North America. High nucleotide diversity was discovered among the populations studied. Pairwise FST values between geographical populations of PVA ranged from 0.22 to 0.46, indicating a significant spatial structure for this pathogen. Although purifying selection was detected at the majority of polymorphic sites, significant positive selection was identified in the P1, NIa, and NIb proteins, pointing to adaptive evolution of PVA. Further phylogeny–trait association analysis showed that the clustering of PVA isolates was significantly correlated with geographic regions, suggesting that geography-driven adaptation may be an important determinant of PVA diversification.

Context-dependent dispersal determines relatedness and genetic structure in a patchy amphibian population.

Dispersal is a central process in ecology and evolution with far reaching consequences for the dynamics and genetics of spatially structured populations (SSPs). Individuals can adjust their decisions to disperse according to local fitness prospects, resulting in context-dependent dispersal. By determining dispersal rate, distance and direction, these individual-level decisions further modulate the demography, relatedness and genetic structure of SSPs. Here, we examined how context-dependent dispersal influences the dynamics and genetics of a great crested newt (Triturus cristatus) SSP. We collected capture-recapture data of 5564 individuals and genetic data of 950 individuals across an SSP in northern Germany. We added genetic data from six sites outside this SSP to assess genetic structure and gene flow at a regional level. Dispersal rates within the SSP were high but dispersal distances were short. Dispersal was context-dependent: individuals preferentially immigrated into high-quality ponds where breeding probabilities were higher. The studied SSP behaved like a patchy population, where subpopulations at each pond were demographically interdependent. High context-dependent dispersal led to weak but significant spatial genetic structure and relatedness within the SSP. At the regional level, a strong hierarchical genetic structure with very few first-generation migrants as well as low effective dispersal rates suggest the presence of independent demographic units. Overall, our study highlights the importance of habitat quality for driving context-dependent dispersal and therefore demography and genetic structure in SSPs. Limited capacity for long-distance dispersal seems to increase genetic structure within a population and leads to demographic isolation in anthropogenic landscapes.

Urban proximity while breeding is not a predictor of perfluoroalkyl substance contamination in the eggs of brown pelicans

Identifying sources of exposure to chemical stressors is difficult when both target organisms and stressors are highly mobile. While previous studies have demonstrated that populations of some organisms proximal to urban centers may display increased burdens of human-created chemicals compared to more distal populations, this relationship may not be universal when applied to organisms and stressors capable of transboundary movements. We examined eggs of brown pelicans (Pelecanus occidentalis), a nearshore seabird with daily movements ranging from local to 50 km and annual migrations ranging from year-round residency to 1500 km. Thirty-six eggs from three breeding colonies located at increasing distances to a major urban center (Charleston, South Carolina, USA) were analyzed for concentrations of per- and polyfluoroalkyl substances (PFAS). Areas of high use for each colony during the breeding season were also assessed via the tracking of adult pelicans from each colony using GPS-PTT satellite transmitters and overlapped with measures of relative urbanization via land cover data. We report potentially significant ∑PFAS concentrations in the eggs of pelicans (175.4 ± 120.1 ng/g w wt. SD), driven largely by linear perfluorooctane sulfonate (n-PFOS) (48–546 ng/g w wt.). Residues of the precursor compound perfluorooctane sulfonamide (FOSA) were also present in pelican eggs, suggesting continued exposure of local wildlife beyond implemented phaseouts of some PFAS. For most analytes, egg concentrations did not exhibit a significant spatial structure despite some differentiation in high-use areas unlike similar data for another regional apex predator, the bottlenose dolphin (Tursiops truncatus). We suggest that the partially migratory nature of brown pelicans during the non-breeding season, combined with daily ranges that may extend to 50 km from local point sources, may have homogenized exposure across individuals. Charleston likely remains a major source for PFAS in the overall region, however, given the high concentrations observed as well as known releases of PFAS in the nearshore environment.