Small Geographic Scale Research Articles

Phylogeography of the Island Leaf Warbler (Aves: Phylloscopus Poliocephalus) in Northern Melanesia Reveals Rapid Secondary Sympatry or Ecological Speciation on Kolombangara Island, Solomon Islands

Island archipelagos are well known for promoting geographic and adaptive radiations in terrestrial animals. Sympatry of closely related species in island systems has been thought to occur primarily through double-invasions from the same continental source population. Alternatively, this process can occur on a smaller geographic scale where divergent populations isolated from one another within an archipelago may come back into contact via intra-archipelago dispersal. Depending on degree of divergence and the development of reproductive isolating barriers, the result of this secondary contact could be gene flow between isolated populations, exclusion or extirpation of one population via competition, or the establishment of reproductively isolated sympatric species. Here, we provide strong evidence for intra-archipelago secondary sympatry within a radiation of Phylloscopus warblers in the Solomon and Bismarck archipelagos by presenting the first well-sampled phylogeny of Phylloscopus warbler populations in the region. By using genome-wide genetic data and complete mitochondrial genomes we also present evidence for a complex history of mitochondrial-nuclear discordance within this radiation, particularly in the only pair of sympatric populations east of Wallace’s Line, located on Kolombangara Island in the Solomon Islands. Our genomic data suggest that the divergent single-island endemic species on Kolombangara (Phylloscopus amoenus) is not a relic resulting from a double invasion from outside the Bismarck and Solomon archipelagos as previously thought. Rather, the sympatry on Kolombangara Island between the widespread P. poliocephalus and the endemic P. amoenus appears to result from recent intra-archipelago diversification, either via sympatric speciation or the rapid establishment of secondary sympatry. These novel genomic data provide insights into the evolutionary history of Phylloscopus warblers in Melanesia and improve our general understanding of how biodiversity accumulates in island systems.

Greenness visibility in urban living environments as pathway to promote health and well-being: Mapping spatial differentiation in Flanders (Belgium) based on viewshed analysis

A substantial body of evidence links green space to positive health outcomes. Beyond the availability of dedicated green spaces such as parks and the overall presence of vegetation and trees, visual exposure to greenery has also been shown to be important for well-being. Enhancing visual access to greenery may thus represent a pathway to promoting health and well-being. However, at regional or national scales, insights into disparities in visual access to greenery remain scarce. Most research and policy efforts rely on two-dimensional (top-down) data, which often fails to accurately capture the amount of greenery visible from individual perspectives, such as from within homes.This study builds on the work of Labib et al. [20], who developed a high-resolution (5 m grid) Viewshed Greenness Visibility Index (VGVI) for the Greater Manchester area (UK). By introducing technical improvements that significantly increased computational efficiency, we extended this approach to create a comprehensive VGVI map for Flanders, the northern region of Belgium. The resulting map enabled a broad assessment of VGVI disparities across Flanders. Our findings reveal evidence of distributive environmental injustice, as demonstrated by a strong negative correlation (Spearman's Rho = -0.48) between neighbourhood deprivation levels and VGVI scores. In Flanders, residents of more deprived neighbourhoods are exposed to significantly lower levels of visible greenery.We further explored the differences and similarities between traditional top-down greenness mapping and VGVI, which provides an eye-level perspective. Although a strong positive correlation was observed at the regional scale (Pearson's r = 0.80), this relationship weakens at the local level. Our findings suggest that VGVI analysis is particularly valuable at smaller geographic scales, making it especially relevant for research or spatial policies that address disparities in individual living conditions or target specific locations, such as schools, nurseries, hospitals, retirement homes, and community centres.

Genetic patterns reveal geographic drivers of divergence in silvereyes (Zosterops lateralis)

Identifying mechanisms that drive population divergence under varying geographic and ecological scenarios can inform our understanding of evolution and speciation. In particular, analysis of genetic data from island populations with known colonisation timelines allows us to identify potential source populations of diverging island subspecies and current relationships among populations. Silvereyes (Zosterops lateralis) are a small passerine that have served as a valuable study system to investigate evolutionary patterns on both large and small geographic scales. We examined genetic relatedness and diversity of two silvereye subspecies, the mainland Z. l. cornwalli and island Z. l. chlorocephalus, and used 18 077 single nucleotide polymorphisms (SNPs), to compare locations across southeast Queensland, Australia. Although silvereyes are prolific island colonisers our findings revealed population divergence over relatively small spatial scales was strongly influenced by geographic isolation mediated by water barriers. Strong genetic connectivity was displayed between mainland sites, but minimal inter-island connectivity was shown despite comparable sampling distances. Genetic diversity analysis showed little difference in heterozygosity between island and mainland populations, but lower inbreeding scores among the island populations. Our study confirmed the range of the Z. l. chlorocephalus subspecies throughout the southern Great Barrier Reef. Our results show that water barriers and not geographic distance per se are important in driving incipient divergence in island populations. This helps to explain the relatively high number of phenotypically differentiated, but often geographically proximate, island silvereye subspecies compared to a lower number of phenotypically less well-defined Australian continental subspecies.

A Comparison of Butterfly Diversity Results between iNaturalist and Expert Surveys in Eastern Oklahoma

Ongoing worldwide biodiversity declines and range shifts associated with climate change increase the importance of documenting the current distributions of species to establish baseline data. However, financial and logistical constraints make it impossible for taxonomic experts to conduct thorough surveys in most locations. One popular approach to offset the lack of expert sampling is using community science data collected by the public, curated, and made available for research. These datasets, however, contain different biases than those typically present in data collected through conventional survey practices, often leading to different results. Recent studies have used massive datasets generated over large areas; however, less is known about the results obtained at smaller scales or with more limited sampling intervals. We compared butterfly observations in eastern Oklahoma using a dataset obtained from the popular community science website iNaturalist and one collected during targeted surveys of glade habitats conducted by taxonomic experts. At the county-level scale, the relative abundances of butterfly species correlated well between the glade surveys and the iNaturalist observations, and there was no difference in the relative abundance of different butterfly families between the two survey methods. However, as anticipated, the conventional surveys outperformed the community science data in measuring biodiversity at a smaller geographic scale.

Phenolic Profiles in Olive Leaves from Different Cultivars in Tuscany and Their Use as a Marker of Varietal and Geographical Origin on a Small Scale.

Olive leaves are a rich source of polyphenols with healthful properties and represent one of the most abundant waste products of olive oil production. The aims of this study were to explore the phenolic composition of olive leaves from the three main Tuscan cultivars (Leccino, Moraiolo and Frantoio) collected in Siena and Grosseto provinces and to investigate the possible use of these compounds as varietal and geographic origin markers. Discriminant factorial analysis (DFA) was used for distinguishing between different cultivars and locations. Apigenin and caffeoyl-secologanoside showed significant differences between cultivars. DFA showed that ligstroside, apigenin and luteolin have the most influence in determining the differences between sites, whereas total polyphenols, olacein and hydroxytyrosol acetate allowed for separation between leaves from the same province. The results of the present study indicate that concentrations of phenolic compounds, measured through high-resolution mass spectrometry, can be used as a marker for both the cultivar and of geographical origin of olive leaves, and possibly of olive-related products, as well as across small geographic scales (less than 50 km distance between sites).

Genetic differentiation across a steep and narrow environmental gradient: Quantitative genetic and genomic insights into Lake Superior populations of Quercus rubra.

Adaptive differentiation of traits and underlying loci can occur at a small geographical scale if natural selection is stronger than countervailing gene flow and drift. We investigated this hypothesis using coupled quantitative genetic and genomic approaches for a wind-pollinated tree species, Quercus rubra, along the steep, narrow gradient of the Lake Superior coast that encompasses four USDA Hardiness Zones within 100 km. For the quantitative genetic component of this study, we examined phenotypic differentiation among eight populations in a common garden, measuring seed mass, germination, height, stem diameter, leaf number, specific leaf area and survival. For the genomic component, we quantified genetic differentiation for 26 populations from the same region using RAD-seq. Because hybridisation with Quercus ellipsoidalis occurs in other parts of the species' range, we included two populations of this congener for comparison. In the common garden study, we found a strong signal of population differentiation that was significantly associated with at least one climate factor for nine of 10 measured traits. In contrast, we found no evidence of genomic differentiation among populations based on FST or any other measures. However, both distance-based and genotype-environment association analyses identified loci showing the signature of selection, with one locus in common across five analyses. This locus was associated with the minimum temperature of the coldest month, a factor that defines the climate zones and was also significant in the common garden analyses. In addition, we documented introgression from Q. ellipsoidalis into Q. rubra, with rates of introgression correlated with the climate gradient. In sum, this study reveals signatures of selection at the quantitative trait and genomic level consistent with climate adaptation, a pattern that is more often documented at a much broader geographical scale, especially in long-lived wind-pollinated species.

Do fish gut microbiotas vary across spatial scales? A case study of Diplodus vulgaris in the Mediterranean Sea

BackgroundBiogeography has been linked to differences in gut microbiota in several animals. However, the existence of such a relationship in fish is not clear yet. So far, it seems to depend on the fish species studied. However, most studies of fish gut microbiotas are based on single populations. In this study, we investigated the gut microbiota of fish from three wild populations of the two-banded sea bream Diplodus vulgaris (Geoffroy Saint-Hilaire, 1817) to determine whether its diversity, structure and potential functionality reflect the geographic origin of the fish, at large and small geographical scale. Additionally, we explored the host- and environmental-related factors explaining this relationship.ResultsWe showed that the taxonomy and potential functionality of the mucosa-associated gut microbiota of Diplodus vulgaris differ to varying degrees depending on the spatial scale considered. At large scale, we observed that both the taxonomical structure and the potential functionality of the fish microbiota differed significantly between populations. In contrast, the taxonomical diversity of the microbial community displayed a significant relationship with factors other than the geographic origin of the fish (i.e. sampling date). On the other hand, at small scale, the different composition and diversity of the microbiota differ according to the characteristics of the habitat occupied by the fish. Specifically, we identified the presence of Posidonia oceanica in the benthic habitat as predictor of both the microbiota composition and diversity. Lastly, we reported the enrichment of functions related to the metabolism of xenobiotics (i.e. drugs and 4-aminobenzoate) in a population and we indicated it as a potential target of future monitoring.ConclusionsWith this study, we confirmed the importance of investigating the gut microbiota of wild fish species using multiple populations, taking into account the different habitats occupied by the individuals. Furthermore, we underscored the use of the biodegradation potential of the gut microbiota as an alternative means of monitoring emerging contaminants in Mediterranean fish.

Public health policy impact evaluation: A potential use case for longitudinal monitoring of viruses in wastewater at small geographic scales

Public health policy impact evaluation is challenging to study because randomized controlled experiments are infeasible to conduct, and policy changes often coincide with non-policy events. Quasi-experiments do not use randomization and can provide useful knowledge for causal inference. Here we demonstrate how longitudinal wastewater monitoring of viruses at a small geographic scale may be used in a quasi-experimental design to evaluate the impact of COVID-19 public health policies on the spread of COVID-19 among a university population. We first evaluated the correlation between incident, reported COVID-19 cases and wastewater SARS-CoV-2 RNA concentrations and observed changes to the correlation over time, likely due to changes in testing requirements and testing options. Using a difference-in-differences approach, we then evaluated the association between university COVID-19 public health policy changes and levels of SARS-CoV-2 RNA concentrations in wastewater. We did not observe changes in SARS-CoV-2 RNA concentrations associated with most policy changes. Policy changes associated with a significant change in campus wastewater SARS-CoV-2 RNA concentrations included changes to face covering recommendations, indoor gathering bans, and routine surveillance testing requirements and availability.

Gene pool preservation across time and space In Mongolian-speaking Oirats

The Oirats are a group of Mongolian-speaking peoples residing in Russia, China, and Mongolia, who speak Oirat dialects of the Mongolian language. Migrations of nomadic ethnopolitical formations of the Oirats across the Eurasian Steppe during the Late Middle Ages/early Modern times resulted in a wide geographic spread of Oirat ethnic groups from present-day northwestern China in East Asia to the Lower Volga region in Eastern Europe. In this study, we generate new genome-wide and mitochondrial DNA data for present-day Oirat-speaking populations from Kalmykia in Eastern Europe, Western Mongolia, and the Xinjiang region of China, as well as Issyk-Kul Sart-Kalmaks from Central Asia, and historically related ethnic groups from Altai, Tuva, and Northern Mongolia to study the genetic structure and history of the Oirats. Despite their spatial and temporal separation, small current population census, both the Kalmyks of Eastern Europe and the Oirats of Western Mongolia in East Asia are characterized by strong genetic similarity, high effective population size, and low levels of interpopulation structure. This contrasts the fine genetic structure observed today at a smaller geographic scale in traditionally sedentary populations, and is conditioned by high mobility and marriage practices (traditional strict exogamy) in nomadic groups. Conversely, the genetic profile of the Issyk-Kul Sart-Kalmaks suggests a distinct source(s) of genetic ancestry, along with indications of isolation and genetic drift compared to other Oirats. Our results also show that there was limited gene flow between the ancestors of the Oirats and the Altaians during the late Middle Ages.Source of the yurt image: https://www.vecteezy.com/free-vector/yurt.

Exploring the variances of climate change opinions in Germany at a fine-grained local scale

How and why climate change opinions vary within countries at a small geographic scale is rarely investigated. Previous research has focused on public opinions at the individual or national level, leaving local differences within countries and their underlying factors largely unexplored. The lack of research at subnational levels is problematic, as adaptation and mitigation policies depend on collective support and action involving multiple stakeholders at the local scale. It is thus crucial to identify geographic differences in climate change opinions and to unravel their determinants at a fine-grained local scale. We examine public CCOs across 4,667 municipalities in Germany by relying on a representative survey of households. Here we show substantial and systematic differences in public climate change opinions across locations that manifest between urban vs. rural and prospering vs. declining areas. Besides these geographic features, more complex historical and cultural differences between places play an important role.

Ecological and Biogeographical Imprints in a Beech Glacial Refugium

The distribution of vascular plant species and assemblages existing in beech (Fagus sylvatica L.) forests was compared with the distribution of beech chloroplast DNA (cpDNA) haplotypes, aiming to identify possible interpretable trends of co-occurrence, on a small geographical scale, and to infer the relevant historical factors. Vegetation and genetic (cpSSR) data were collected from 60 plots on Mt. Menikio (northeastern Greece). Classification and ordination analyses were applied on the vegetation data, while on the cpSSR data, diversity measures and genetic structure analyses were employed. A probabilistic co-occurrence analysis was performed on haplotypes and taxa. The results show that a plant biogeographical border exists on Mt. Menikio which, in addition, has acted both as a refugium and as a meeting point of lineages for more than one glacial cycle. Significant associations of co-occurrence between haplotypes and vascular taxa were found but no common distribution patterns between the former and species assemblages were identified. The combined consideration of the distribution profiles of species assemblages, plant species and cpDNA haplotypes (corresponding to the three levels of biodiversity) provides concrete information on historical events, leading to a comprehensive understanding of the evolutionary and biogeographical processes that have shaped specific spatial patterns of biodiversity.

Urbanization and distance shape population structure in Fundulus heteroclitus

Abstract The federal Superfund site at New Bedford Harbor (Massachusetts, USA) is an example of an environment where pollution levels rose quickly and dramatically. Industrial waste containing polychlorinated biphenyls, heavy metals, and other organic pollutants was dumped into the harbor in the mid-20th century. The mummichog (Fundulus heteroclitus) is a widely distributed fish typically susceptible to polychlorinated biphenyl toxicity. However, the population in New Bedford Harbor is one of several that have evolved the ability to tolerate this category of toxicants. Constituents of the aryl hydrocarbon receptor system are linked to this adaptive pollution tolerance. Our population genetic analysis of 444 mummichogs from Massachusetts and Rhode Island estuaries using 55 SNP loci suggests that F. heteroclitus near New Bedford Harbor have large populations and restricted but meaningful levels of gene exchange among adjacent habitats. When comparing polluted to cleaner sites, we find strong evidence of genetic differentiation at a small geographic scale. Populations at the two most polluted sites form a genetically distinct cluster. Much of this differentiation is driven by allele frequency differences at loci associated with the aryl hydrocarbon receptor system. While allele frequencies at loci associated with pollution tolerance vary between clean and polluted habitats, putatively adaptive alleles are present at low frequency elsewhere in our study area.

Characterization of pure and admixed brown trout (Salmo trutta) populations of high conservation value in the upper Danubian contact zone using ddRADseq genotyping

Increasing rates of hybridization and introgression in managed populations of freshwater fish are a major threat to the long-term viability of native species. The conservation challenge begins with identifying native gene pools. For brown trout (Salmo trutta Linnaeus, 1758) in the Upper Danube drainage, this task is complicated by the presence of both naturally and anthropogenically induced admixture of highly divergent lineages (Atlantic and Danubian). Herein, a ddRADseq protocol was used to type 377 individuals from 24 populations in the Upper Danube in Austria and Germany, and from reference populations from adjacent drainages and commercial hatcheries. High genetic differentiation at small geographic scales was found among pure Danubian-lineage populations, especially in the Kalkalpen National Park (Austria). In the Upper Danube drainage of Germany, as well as in the Rhine and Elbe drainages, brown trout populations were predominantly of Atlantic-lineage origin – as were those of all commercial hatcheries. Most populations, however, showed various degrees of admixture between Danubian and Atlantic lineages, hypothesized to be the result of both natural and anthropogenic processes. We highlight the conservation value of pure Danubian-lineage populations, and the challenges promoting conservation of naturally admixed populations, while discouraging continued stocking and admixture via management activities.

Exploring the origin and fate of surface and sub-surface marine microplastics in the Canary Islands region

The presence of different types of microplastics (MPs) in the Atlantic Ocean has been well-documented, with data collected from the Canary Islands indicating high concentrations of MPs at four different beaches (hot spots). However, critical gaps persist regarding the abundance of MPs in diverse open ocean regions, at varying depths, and their transport behavior and origin. This study aims to evaluate, for the first time, the large-scale (>100 km) and mesoscale (10-100 km) ocean dynamic processes and the resulting transport of MPs in the region. On the one hand, this study investigates the surface velocity of currents between 27-32°N latitude range, establishing correlation with the accumulation of MPs on diverse beaches across several islands of the archipelago. This analysis goes beyond studying the predominant current by integrating data at a smaller geographical scale over a two-year period. Concurrently, previous and ongoing research suggests the presence of small MPs (SMPs,<1 mm) at high concentration at a depth of 1100 meters in this region. By integrating these vertical profiles of MPs with a deep understanding of the physical processes of the Canary region accumulated over decades of research, our study introduces an innovative model that outlines how SMPs are sink and transported in open oceans by water mases. This comprehensive approach not only enhances our understanding of the complex dynamics influencing the distribution of MPs but also provides crucial insights to address the widespread problem of MP pollution in the Atlantic.

Small-scale metapopulation structure of a limnophilic fish species in a natural river system investigated using microsatellite genotyping by amplicon sequencing (SSR-GBAS)

Habitat niches of fish species can exert a strong influence on population structure, even on a small geographical scale. In this scope, Pelasgus thesproticus is a great model species to study connectivity in riverine environments owing to its naturally patchy habitat distribution. Furthermore, it is important to conduct such studies in near-natural systems to avoid the impact of human disturbances on the river, such as fragmentation, morphological changes and habitat degradation. In this sense, the Vjosa in Albania is an excellent study area. A total of 204 individuals were sampled from five locations in the lower Vjosa and two tributaries and genotyped with 33 newly designed microsatellites loci using high throughput sequencing. The application of microsatellite genotyping by sequencing revealed genetic structure and some differentiation, even at a small spatial scale (< 65 river km). A total of 500 alleles were found with an average of 0.93 private alleles among sites with rather low FST values (< 0.04). The extent of admixture observed in some populations indicate that the genetic structure is mainly influenced by upstream populations, either from the main river itself or from tributaries. In addition, the connection between a tributary and the other sites is disrupted by the flow regime, which is reflected in a high degree of divergence from the other populations. Our results indicate that hydrological conditions of the flowing river present strong barriers to gene flow, particularly in the upstream direction, but at the same time act as dispersal corridors in the downstream direction and exhibit source-sink dynamics in which upstream populations contribute disproportionately to downstream populations for this habitat specialist along the river. It is suggested that processes of colonization and reinforcement may play an important role in shaping the genetic structure of patchily distributed fish species in natural river systems. Future studies should increase the knowledge of dispersal factors, habitat heterogeneity, consequence of source-sink dynamics, and gene flow within the system, which will help to understand and maintain important processes related to metapopulation theory and the potential evolutionary consequences of habitat loss and fragmentation.

Genetic structure and diversity of the seagrass Zostera marina along a steep environmental gradient, with implications for genetic monitoring

Zostera marina (eelgrass) is a foundation species in coastal zones in the northern hemisphere. Eelgrass is declining across its distribution, a trend likely to accelerate under climate change. In Sweden, eelgrass is a species of particular concern in management and conservation. Here, we provide information on genetic variation, an important component for the potential persistence and adaptation of any species in a changing environment. In particular, the steep salinity gradient over which eelgrass is distributed along the Swedish coast (26 psu on the west coast to 5 psu on the east coast) calls for a better understanding of genetic diversity, connectivity, and potential for local adaptation. To assess genetic variation and population genetic structure, we genotyped individuals with 2,138 single nucleotide polymorphisms (SNPs) from 15 eelgrass meadows spanning the whole Swedish distribution. We found a geographic population genetic structure from west to east parallel to the salinity gradient and with a clear genetic break at the entrance to the Baltic Sea. Meadows along the low salinity east coast consisted of a few or only one clone. Eelgrass on the west coast had higher genotypic richness, higher genetic variation, and showed population differentiation on smaller geographic scales. With their low genetic variation, the east coast meadows are especially threatened amidst global changes. Lack of sexual reproduction and the capacity to generate new genotypes is an issue that needs to be seriously considered in management and conservation. In addition, the lack of sexual reproduction renders clonal eelgrass less likely to recover and recolonize after disturbance, and more challenging to restore. The here provided information on genetic clusters, clonality, and genetic variation can be included for prioritizing meadows for conservation and for identifying meadows for restoration purposes. Most importantly, genetic monitoring is urgently needed to assess temporal genetic changes of eelgrass along the Swedish coast and elsewhere facing climate change.

Not one but two: examining the genetic origin and characterization of the non-native spectacled caiman (Caiman crocodilus) in Florida

The US state of Florida is home to an alarmingly large number of invasive species, many of which have proven detrimental to native ecosystems. Biological invasions of reptiles in particular have been a major concern in recent years. The spectacled caiman (Caiman crocodilus) was first introduced from Latin America to Florida in the 1950’s. Given there are now established breeding populations across southern Florida, there are ongoing efforts to control them. Therefore, there is a need to understand this species’ natural history and introduction pathways. Previous studies have cited the Caribbean Coastal region of Colombia as a primary, and possibly exclusive, origin of C. crocodilus in Florida, and the species was identified as belonging to the C. c. fuscus molecular lineage. However, previous genetic sampling has been limited and may have been biased by small sample sizes and limited geographic scale. We collected 27 genetic samples from caimans captured in Florida, and sequenced the mitochondrial genes, Cytochrome oxidase I (COI) and Cytochrome B (CytB) for comparison with homologous gene fragments available for the species at GenBank. We found genetic evidence for multiple introduction events and the taxonomic classification of the Florida caimans as two distinct molecular lineages (C. c. fuscus and C. c. crocodilus) originating from at least two different regions: the Magdalena River Basin in Colombia and the Upper Branco River Basin in northern Brazil. This study helps to elucidate the genetic history of Florida caimans and provides valuable insight for population management of the species in Florida.

Impact of Elevational Gradients and Chemical Parameters on Changes in Soil Bacterial Diversity Under Semiarid Mountain Region.

Elevation gradients, often regarded as "natural experiments or laboratories", can be used to study changes in the distribution of microbial diversity related to changes in environmental conditions that typically occur over small geographical scales. We obtained bacterial sequences using MiSeq sequencing and clustered them into operational taxonomic units (OTUs). The total number of reads obtained by the bacterial 16S rRNA sequencing analysis was 1,090,555, with an average of approximately 45,439 reads per sample collected from various elevations. The current study observed inconsistent bacterial diversity patterns in samples from the lowest to highest elevations. 983 OTUs were found common among all the elevations. The most unique OTUs were found in the soil sample from elevation_2, followed by elevation_1. Soil sample collected at elevation_6 had the least unique OTUs. Actinobacteria, Protobacteria, Chloroflexi were found most abundant bacterial phyla in current study. Ammonium nitrogen (NH4+-N), and total phosphate (TP) are the main factors influencing bacterial diversity at elevations_1. pH was the main factor influencing the bacterial diversity at elevations_2, elevation_3 and elevation_4. Our results provide new visions on forming and maintaining soil microbial diversity along an elevational gradient and have implications for microbial responses to environmental change in semiarid mountain ecosystems.

Mobility of antimony in contrasting surface environments of a mine site: influence of redox conditions and microbial communities.

Microbial processes can influence the complex geochemical behaviour of the toxic metalloid antimony (Sb) in mining environments. The present study is aimed to evaluate the influence of microbial communities on the mobility of Sb from solid phases to water in different compartments and redox conditions of a mining site in southwest (SW) Spain. Samples of surface materials presenting high Sb concentrations, from two weathered mining waste dumps, and an aquatic sediment were incubated in slurries comparing oxic and anoxic conditions. The initial microbial communities of the three materials strongly differed. Incubations induced an increase of microbial biomass and an evolution of the microbial communities' structures and compositions, which diverged in different redox conditions. The presence of active bacteria always influenced the mobility of Sb, except in the neutral pH waste incubated in oxic conditions. The effect of active microbial activities in oxic conditions was dependent on the material: Sb oxic release was biologically amplified with the acidic waste, but attenuated with the sediment. Different bacterial genera involved in Sb, Fe and S oxidation or reduction were present and/or grew during incubation of each material. The results highlighted the wide diversity of microbial communities and metabolisms at the small geographic scale of a mining site and their strong implication in Sb mobility.

Temporal Variation in Selection Influences Microgeographic Local Adaptation.

AbstractEcological heterogeneity can lead to local adaptation when populations exhibit fitness trade-offs among habitats. However, the degree to which local adaptation is affected by the spatial and temporal scale of environmental variation is poorly understood. A multiyear reciprocal transplant experiment was performed with populations of the annual plant Leptosiphon parviflorus living on adjacent serpentine and nonserpentine soil. Local adaptation over this small geographic scale was observed, but there were differences in the temporal variability of selection across habitats. On serpentine soil, the local population had a consistently large survival advantage, presumably as a result of the temporal stability in selection imposed by soil cation content. In contrast, a fecundity advantage was observed for the sandstone population on its native soil type but only in the two study years with the highest rainfall. A manipulative greenhouse experiment demonstrated that the fitness advantage of the sandstone population in its native soil type depends critically on water availability. The temporal variability in local adaptation driven by variation in precipitation suggests that continued drought conditions have the potential to erode local adaptation in these populations. These results show how different selective factors can influence spatial and temporal patterns of variation in fitness trade-offs.