Multiple scale analysis of factors influencing the distribution of an invasive aquatic grass

With the expected increase in the spread of invasive species, examination of factors controlling distributions at multiple spatial scales and ecological modelling of their potential distributions are important analyses for informed decision-making. The scale-dependence of mechanisms influencing invasion by non-native species has been shown previously, indicating that studies of key factors affecting invasive species distributions at multiple spatial scales are critical for successful management. Freshwater systems are particularly vulnerable to invasive species, yet few studies have examined the environmental factors influencing distributions of invasive species at multiple spatial scales. We examined the effect of environmental variables on the predicted distribution of the invasive aquatic grass Glyceria maxima over continental, regional and local scales in Australia. We undertook an initial critical evaluation of which predictor variables were most appropriate to use at each scale, largely considering prior knowledge. On a continental scale, climatic, topographic and hydrological variables predicted well the potential distribution of G. maxima, identifying temperate regions as most susceptible to invasion. The regional analysis found that dense, woody, riparian vegetation has a strong negative impact on the occurrence of G. maxima, especially at intermediate elevations. The invasive grass was found less often on biotite granite and on fluvial geology. At a local scale, occurrence of G. maxima was related positively to soil phosphorus and nitrogen, and negatively related to soil organic carbon. The identification of key factors affecting invasive species distributions at multiple spatial scales will inform prevention schemes, assist targeted field sampling for the development of monitoring programs, and allow prioritization of control methods.     

Hierarchical scales of spatial variation in the smaller surface and near-surface macrobenthos of a subtropical intertidal seagrass system in Moreton Bay,Queensland

Core samples were taken along a 4 km stretch of intertidal seagrass on North Stradbroke Island, eastern Australia, at nested scales of 1 m (stations), 150 m (sites), and 2 km (localities) to investigate the extent to which abundance, diversity, and assemblage composition of the dominant smaller members (<10 mm) of the intertidal seagrass macrobenthos vary spatially and over what scales. Gastropods and polychaetes dominated both the 91 species present and, together with decapods, also the numbers of individuals. Abundance was low (mean < 2000 individuals m⁻²) but species diversity was high (overall Simpson’s index of diversity 0.91), with 44% of species occurring only as one or two individuals, and with only two species contributing >10% to the total numbers (the microgastropod Calopia imitata and crab Enigmaplax littoralis, both little known, rarely recorded endemics). On average, a species only occurred at 6% of stations and only four occurred at >25%. Assemblages at the three localities did not vary significantly in gross ecological features (levels of species richness, faunal abundance and species diversity per component site) (ANOVA P ≫ 0.05), but did vary markedly in their composition at all spatial scales (PERMANOVA P < 0.05). Variance partitioning showed that components of total variance were least at the largest spatial scale (locality 15.9%) and greatest at the smallest scale (station 59.3%). The commoner individual species all showed random distributions at small spatial scales but clumped distributions at large spatial scales.     

Patterns of alien plant distribution at multiple spatial scales in a large national park: implications for ecology, management and monitoring

Aim Spatial scale is critical for understanding and managing biological invasions. In providing direction to managing alien plant invasions, much emphasis is placed on collecting spatially explicit data. However, insufficient thought is often given to how the data are to be used, frequently resulting in the incompatibility of the data for different uses. This paper explores the role of spatial scale in interpreting, managing and monitoring alien plant invasions in a large protected area. Location Kruger National Park, South Africa. Methods Using 27,000 spatially‐explicit records of invasive alien plants for the Kruger National Park (> 20,000 km²) we assessed alien plant species richness per cell at nine different scales of resolution. Results When assessing the patterns of alien plants at the various scales of resolution, almost identical results are obtained when working at scales of quarter‐degree grids and quaternary watersheds (the fourth level category in South Africa's river basin classification system). Likewise, insights gained from working at resolutions of 0.1–0.5 km and 1–5 km are similar. At a scale of 0.1 × 0.1 km cells, only 0.4% of the Kruger National Park is invaded, whereas > 90% of the park is invaded when mapped at the quarter‐degree cell resolution. Main conclusions Selecting the appropriate scale of resolution is crucial when evaluating the distribution and abundance of alien plant invasions, understanding ecological processes, and operationalizing management applications and monitoring strategies. Quarter‐degree grids and quaternary watersheds are most useful at a regional or national scale. Grid cells of 1 to 25 km² are generally useful for establishing priorities for and planning management interventions. Fine‐scale data are useful for informing management in areas which are small in extent; they also provide the detail appropriate for assessing patterns and rates of invasion.     

Productivity–species richness relationship changes from unimodal to positive linear with increasing spatial scale in the Inner Mongolia steppe

Productivity–species diversity relationships have been a controversial research topic in ecology with scale believed to be among the main reasons for discovering different relationships. We collected data on species diversity (richness) and productivity (peak above-ground biomass) of the Stipa breviflora association in the Inner Mongolia grassland to examine spatial scale dependency and possible underlying mechanisms responsible for the relationships found. One local and seven different landscape scales (the first level corresponds in extent to a 100 × 100 km area, which is increased consecutively by 100 km resulting in the 700 × 700 km area at the highest level) were considered. We found that: (1) unimodal relationships dominated the local scale, but this varied depending on the position along successional gradients; (2) a positive linear relationship was common at larger spatial scales; (3) biotic processes were the most likely primary factor underlying local scale unimodal relationships, but environmental heterogeneity (precipitation patterns) was the main determinant of relationships found at larger spatial scales; (4) our study contributed to other empirical evidence and predictions of theoretical models regarding scale dependency of productivity–species richness relationships; (5) while earlier research demonstrated positive linear species richness–productivity relationships across a number of ecological scales in the Inner Mongolia steppe, our study specifically tested a spectrum of geographical scales to confirm the scale-dependency of this relationship. Lastly, our study emphasized the critical role played by precipitation patterns in controlling biodiversity and grassland ecosystem functioning, which maintains the relatively high level of biodiversity and stable ecosystem processes.     

The influence of spatial scale on the genetic structure of a widespread tropical wetland tree, Pterocarpus officinalis (Fabaceae)

Identifying factors that cause genetic differentiation in plant populations and the spatial scale at which genetic structuring can be detected will help to understand plant population dynamics and identify conservation units. In this study, we determined the genetic structure and diversity of Pterocarpus officinalis, a widespread tropical wetland tree, at three spatial scales: (1) drainage basin “watershed” (<10 km), (2) within Puerto Rico (<100 km), and (3) Caribbean-wide (>1000 km) using AFLP. At all three spatial scales, most of the genetic variation occurred within populations, but as the spatial scale increased from the watershed to the Caribbean region, there was an increase in the among population variation (Φ_ST=0.19 to Φ_ST=0.53). At the watershed scale, there was no significant differentiation (P=0.77) among populations in the different watersheds, although there was some evidence that montane and coastal populations differed (P<0.01). At the island scale, there was significant differentiation (P<0.001) among four populations in Puerto Rico. At the regional scale (>1000 km), we found significant differentiation (P<0.001) between island and continental populations in the Caribbean region, which we attributed to factors associated with the colonization history of P. officinalis in the Neotropics. Given that genetic structure can occur from local to regional spatial scales, it is critical that conservation recommendations be based on genetic information collected at the appropriate spatial scale.     

Landscapes as gradients: The spatial structure of terrestrial ecosystem components in southern Ontario,Canada

The conventional view of the environment – consisting of discrete patches that repeat themselves across the landscape – has seldom been tested. Across a wide spatial scope in southern Ontario, Canada, we investigated the spatial structure of physical and biological features of the environment: vegetation communities, moisture, pH, and organic content of soil at local scales (10–1250 m), and mammalian communities, mean annual temperature and precipitation at regional scales (10–650 km). Spatial structure was quantified using log–log regression of variance (V) with distance (D), according to the power formula, V = aD^z. All these ecosystem components exhibited gradients. Slopes (z) of log–log regressions were positive (0.065 < z < 0.703) and were significantly steeper at the regional scale than the local scale. Variance appeared to increase without bound as distance between sampling locations increased. The results support the view of landscapes as continua and gradients. These patterns represent a challenge to the conventional view of how the natural environment is organised.     

Coexistence patterns of two invasive thistle species, Carduus nutans and C. acanthoides, at three spatial scales

To better understand the competitive processes involved in invasion by congeners, we examine coexistence patterns of two invasive species, Carduus nutans and C. acanthoides, at three spatial scales. A roadside survey of 5 × 5 km blocks in a previously identified overlap zone provided information about the regional scale. At smaller scales, we surveyed four fields of natural co-occurrence, quantifying the spatial patterns at the field scale by randomly placed 1 × 1 m quadrats and at the smallest scale by detailing plant position within the quadrats. The patterns observed are strikingly different at the different scales. At the regional scale, there is positive local autocorrelation in both species but negative cross-correlation between them, consistent with previous surveys. However, at the field scale, there is positive local autocorrelation in both species, and we generally see a positive association between the two species. At the plot scale, when excluding areas of joint absence, there is again a negative association between the two species. This pattern can also be seen at the field scale when excluding plots with joint absence. These results suggest that, at the scale of a field, the strongest factor determining location is aggregation in favorable habitats, which is a stronger force than the competition-induced segregation evidenced at small scales. Lottery competition for spatially aggregated safe sites thus appears to drive the patterns observed at the field scale, while the regional scale pattern may be a result of restricted natural dispersal and invasion history.     

Research article: small-scale spatial variation of δ13C and δ15N isotopes in Antarctic carbon sources and consumers

Regional food web studies that fail to account for small-scale isotopic variability can lead to a mismatch between an organism’s inferred and true trophic position. Misinterpretation of trophic status may result, substantially limiting spatial and temporal comparability of food web studies. We sampled several carbon sources and consumers in a nested design to assess the variability of food web members across small spatial scales (100 s of m to several km) in regions around the Windmill Islands and Vestfold Hills in East Antarctica. For carbon sources, δ¹³C in sea ice POM was particularly variable between locations (km apart) and between sites (100 s of m apart) with replicate samples varying by up to 16‰. Macroalgae δ¹³C was less variable (replicate samples ranging up to 6.9‰ for the red alga Iridaea cordata), yet still differed between locations. Sediment POM and pelagic POM were the least variable, displaying minimal differences between locations or sites for δ¹³C and δ¹⁵N. Three out of eight consumers were significantly different between locations for δ¹³C, and five out of eight for δ¹⁵N, with the fish Trematomus bernacchii the most variable for both δ¹³C and δ¹⁵N. At smaller scales, the amphipod Paramorea walkeri showed significant variation between sites in δ¹³C but not in δ¹⁵N. We attribute small-scale variability to the dynamic physical environment for carbon sources in coastal systems and a close coupling of diet to habitat for consumers. We highlight the need to account for small-scale spatial variation in sampling designs for regional food web studies.     

Spatial Variability in Litterfall,Litter Standing Crop and Litter Quality in a Tropical Rain Forest Region

Understanding the spatial variability in plant litter processes is essential for accurate comprehension of biogeochemical cycles and ecosystem function. We assessed spatial patterns in litter processes from local to regional scales, at sites throughout the wet tropical rain forests of northern Australia. We aimed to determine the controls (e.g., climate, soil, plant community composition) on annual litter standing crop, annual litterfall rate and in situ leaf litter decomposability. The level of spatial variance in these components, and leaf litter N, P, Ca, lignin, α‐cellulose and total phenolics, was determined from within the scale of subregion, to site (1 km transects) to local/plot (~30 m²). Overall, standing crop was modeled with litterfall and its chemical composition, in situ decomposability, soil Na, and topography (r² = 0.69, 36 plots). Litterfall was most closely aligned with plant species richness and stem density (negative correlation); leaf decomposability with leaf‐P and lignin, soil Na, and dry season moisture (r² = 0.89, 40 plots). The predominant scale of variability in litterfall rates was local (plot), while litter standing crop and α‐cellulose variability was more evenly distributed across spatial scales. Litter decomposability, N, P and phenolics were more aligned with subregional differences. Leaf litter C, lignin and Ca varied most at the site level, suggesting more local controls. We show that variability in litter quality and decomposability are more easily accounted for spatially than litterfall rates, which vary widely over short distances possibly in response to idiosyncratic patterns of disturbance.     

Local–regional boundary shifts in oribatid mite (Acari: Oribatida) communities: species–area relationships in arboreal habitat islands of a coastal temperate rain forest, Vancouver Island, Canada

Aim This study investigates the species–area relationship (SAR) for oribatid mite communities of isolated suspended soil habitats, and compares the shape and slope of the SAR with a nested data set collected over three spatial scales (core, patch and tree level). We investigate whether scale dependence is exhibited in the nested sampling design, use multivariate regression models to elucidate factors affecting richness and abundance patterns, and ask whether the community composition of oribatid mites changes in suspended soil patches of different sizes. Location Walbran Valley, Vancouver Island, Canada. Methods A total of 216 core samples were collected from 72 small, medium and large isolated suspended soil habitats in six western redcedar trees in June 2005. The relationship between oribatid species richness and habitat volume was modelled for suspended soil habitat isolates (type 3) and a nested sampling design (type 1) over multiple spatial scales. Nonlinear estimation parameterized linear, power and Weibull function regression models for both SAR designs, and these were assessed for best fit using R² and Akaike's information criteria (ΔAIC) values. Factors affecting oribatid mite species richness and standardized abundance (number per g dry weight) were analysed by anova and linear regression models. Results Sixty‐seven species of oribatid mites were identified from 9064 adult specimens. Surface area and moisture content of suspended soils contributed to the variation in species richness, while overall oribatid mite abundance was explained by moisture and depth. A power‐law function best described the isolate SAR (S = 3.97 × A^0.12, R² = 0.247, F_1,70 = 22.450, P < 0.001), although linear and Weibull functions were also valid models. Oribatid mite species richness in nested samples closely fitted a power‐law model (S = 1.96 × A^0.39, R² = 0.854, F_1,18 = 2693.6, P < 0.001). The nested SAR constructed over spatial scales of core, patch and tree levels proved to be scale‐independent. Main conclusions Unique microhabitats provided by well developed suspended soil accumulations are a habitat template responsible for the diversity of canopy oribatid mites. Species–area relationships of isolate vs. nested species richness data differed in the rate of accumulation of species with increased area. We suggest that colonization history, stability of suspended soil environments, and structural habitat complexity at local and regional scales are major determinants of arboreal oribatid mite species richness.     

Fungal endophyte β-diversity associated with Myrtaceae species in an Andean Patagonian forest (Argentina) and an Atlantic forest (Brazil)

The biogeography of microorganisms is poorly understood and how microbial diversity is structured is still an open debate. We investigated the processes underlying the fungal endophyte assemblages of phylogenetically related Myrtae host tree species at different spatial scales: regional, 101–5 000 km; local, 0–100 km; and microscale, 0–1 km. A total of 939 isolates was obtained and assigned to 51 distinct MOTUs based on the sequencing of the nrITS region. At regional scales, geographic distance was responsible for explaining the fungal community similarity, while, at a local scale, it was the environmental distance. Moreover, fungal endophytes exhibit preference in the colonization of Luma apiculata but not for Myrceugenia ovata var. nanophylla. Our results suggest that fungal endophytes are not randomly distributed and are influenced by both geographic and environment distances depending on the spatial scale analysed.     

Geographical and environmental controls of palm beta diversity in paleo-riverine terrace forests in Amazonian Peru

The palm (Arecaceae) community on low paleo-riverine terraces (terrace forest) in the north-western Amazon, is described, and we assessed the importance of environmental differences and geographic distance as drivers of its local (25² grain and 0–500 extent) and regional scale (500² grain and 0.3–143 km extent) beta diversity using ordination, multiple regressions on distance matrices and Indicator Species Analysis. A total of 15,869 individuals and 37 species of palm were sampled in 10 terrace forest transects, while 3758 individuals and 21 species were sampled in two adjacent floodplain forest transects for comparison. The terrace and floodplain forest were clearly different in their diversity and floristic composition. The relative importance of geographical distance and environmental difference as controls of terrace forest beta diversity was scale dependent, with environmental differences, notably in soil moisture, dominating at local scales and geographical distance dominating at regional scales. In fact, none of the environmental factors had a significant influence on regional-scale beta diversity. The geographical distance decay in floristic similarity was markedly steeper at local scale ( −0.25 km ⁻¹) than at regional scale ( −0.003 km⁻¹). Such a nonlinear decay is expected if simple dispersal limitation controls beta diversity. However, the absent flattening of the distance decay at the largest distances and the sub-Andean affinities of the westernmost palm communities suggest that large-scale biogeographical processes also contribute to the regional-scale beta diversity. Hereby our results indicate that not only local environment, but also dispersal limitation and biogeographical history can be important controls of the diversity and composition of local plant communities.     

Spatial variation in the climatic predictors of species compositional turnover and endemism

Previous research focusing on broad‐scale or geographically invariant species‐environment dependencies suggest that temperature‐related variables explain more of the variation in reptile distributions than precipitation. However, species–environment relationships may exhibit considerable spatial variation contingent upon the geographic nuances that vary between locations. Broad‐scale, geographically invariant analyses may mask this local variation and their findings may not generalize to different locations at local scales. We assess how reptile–climatic relationships change with varying spatial scale, location, and direction. Since the spatial distributions of diversity and endemism hotspots differ for other species groups, we also assess whether reptile species turnover and endemism hotspots are influenced differently by climatic predictors. Using New Zealand reptiles as an example, the variation in species turnover, endemism and turnover in climatic variables was measured using directional moving window analyses, rotated through 360°. Correlations between the species turnover, endemism and climatic turnover results generated by each rotation of the moving window were analysed using multivariate generalized linear models applied at national, regional, and local scales. At national‐scale, temperature turnover consistently exhibited the greatest influence on species turnover and endemism, but model predictive capacity was low (typically r² = 0.05, P < 0.001). At regional scales the relative influence of temperature and precipitation turnover varied between regions, although model predictive capacity was also generally low. Climatic turnover was considerably more predictive of species turnover and endemism at local scales (e.g., r² = 0.65, P < 0.001). While temperature turnover had the greatest effect in one locale (the northern North Island), there was substantial variation in the relative influence of temperature and precipitation predictors in the remaining four locales. Species turnover and endemism hotspots often occurred in different locations. Climatic predictors had a smaller influence on endemism. Our results caution against assuming that variability in temperature will always be most predictive of reptile biodiversity across different spatial scales, locations and directions. The influence of climatic turnover on the species turnover and endemism of other taxa may exhibit similar patterns of spatial variation. Such intricate variation might be discerned more readily if studies at broad scales are complemented by geographically variant, local‐scale analyses.     

Elevational species shifts in a warmer climate are overestimated when based on weather station data

Strong topographic variation interacting with low stature alpine vegetation creates a multitude of micro-habitats poorly represented by common 2 m above the ground meteorological measurements (weather station data). However, the extent to which the actual habitat temperatures in alpine landscapes deviate from meteorological data at different spatial scales has rarely been quantified. In this study, we assessed thermal surface and soil conditions across topographically rich alpine landscapes by thermal imagery and miniature data loggers from regional (2-km²) to plot (1-m²) scale. The data were used to quantify the effects of spatial sampling resolution on current micro-habitat distributions and habitat loss due to climate warming scenarios. Soil temperatures showed substantial variation among slopes (2–3 K) dependent on slope exposure, within slopes (3–4 K) due to micro-topography and within 1-m² plots (1 K) as a result of plant cover effects. A reduction of spatial sampling resolution from 1 × 1 m to 100 × 100 m leads to an underestimation of current habitat diversity by 25% and predicts a six-times higher habitat loss in a 2-K warming scenario. Our results demonstrate that weather station data are unable to reflect the complex thermal patterns of aerodynamically decoupled alpine vegetation at the investigated scales. Thus, the use of interpolated weather station data to describe alpine life conditions without considering the micro-topographically induced thermal mosaic might lead to misinterpretation and inaccurate prediction.     

Control of “blue carbon” storage by mangrove ageing: Evidence from a 66‐year chronosequence in French Guiana

The role of mangroves in the blue carbon stock is critical and requires special focus. Mangroves are carbon‐rich forests that are not in steady‐state equilibrium at the decadal time scale. Over the last decades, the structure and zonation of mangroves have been largely disturbed by coastal changes and land use conversions. The amount of time since the last disturbance is a key parameter determining forest structure, but it has so far been overlooked in mangrove carbon stock projections. In particular, the carbon sequestration rates among mangrove successional ages after (re)establishment are poorly quantified and not used in large‐scale estimations of the blue carbon stock. Here, it is hypothesized that ecosystem age structure significantly modulates mangrove carbon stocks. We analysed a 66‐year chronosequence of the aboveground and belowground biomass and soil carbon stock of mangroves in French Guiana, and we found that in the year after forest establishment on newly formed mud banks, the aboveground, belowground and soil carbon stocks averaged 23.56 ± 7.71, 13.04 ± 3.37 and 84.26 ± 64.14 (to a depth of 1 m) Mg C/ha, respectively. The mean annual increment (MAI) in the aboveground and belowground reservoirs was 23.56 × Age^−0.52 and 13.20 × Age^−0.64 Mg C ha⁻¹ year⁻¹, respectively, and the MAI in the soil carbon reservoir was 3.00 ± 1.80 Mg C ha⁻¹ year⁻¹. Our results show that the plant carbon sink capacity declines with ecosystem age, while the soil carbon sequestration rate remains constant over many years. We suggest that global projections of the above‐ and belowground reservoirs of the carbon stock need to account for mangrove age structures, which result from historical changes in coastal morphology. Our work anticipates joint international efforts to globally quantify the multidecadal mangrove carbon balance based on the combined use of age‐based parametric equations and time series of mangrove age maps at regional scales.     

Multilevel landscape utilization of the Siberian flying squirrel: Scale effects on species habitat use

Animals use and select habitat at multiple hierarchical levels and at different spatial scales within each level. Still, there is little knowledge on the scale effects at different spatial levels of species occupancy patterns. The objective of this study was to examine nonlinear effects and optimal‐scale landscape characteristics that affect occupancy of the Siberian flying squirrel, Pteromys volans, in South‐ and Mid‐Finland. We used presence–absence data (n = 10,032 plots of 9 ha) and novel approach to separate the effects on site‐, landscape‐, and regional‐level occupancy patterns. Our main results were: landscape variables predicted the placement of population patches at least twice as well as they predicted the occupancy of particular sites; the clear optimal value of preferred habitat cover for species landscape‐level abundance is a surprisingly low value (10% within a 4 km buffer); landscape metrics exert different effects on species occupancy and abundance in high versus low population density regions of our study area. We conclude that knowledge of regional variation in landscape utilization will be essential for successful conservation of the species. The results also support the view that large‐scale landscape variables have high predictive power in explaining species abundance. Our study demonstrates the complex response of species occurrence at different levels of population configuration on landscape structure. The study also highlights the need for data in large spatial scale to increase the precision of biodiversity mapping and prediction of future trends.     

Single nucleotide polymorphism‐based dispersal estimates using noninvasive sampling

Quantifying dispersal within wild populations is an important but challenging task. Here we present a method to estimate contemporary, individual‐based dispersal distance from noninvasively collected samples using a specialized panel of 96 SNPs (single nucleotide polymorphisms). One main issue in conducting dispersal studies is the requirement for a high sampling resolution at a geographic scale appropriate for capturing the majority of dispersal events. In this study, fecal samples of brown bear (Ursus arctos) were collected by volunteer citizens, resulting in a high sampling resolution spanning over 45,000 km² in Gävleborg and Dalarna counties in Sweden. SNP genotypes were obtained for unique individuals sampled (n = 433) and subsequently used to reconstruct pedigrees. A Mantel test for isolation by distance suggests that the sampling scale was appropriate for females but not for males, which are known to disperse long distances. Euclidean distance was estimated between mother and offspring pairs identified through the reconstructed pedigrees. The mean dispersal distance was 12.9 km (SE 3.2) and 33.8 km (SE 6.8) for females and males, respectively. These results were significantly different (Wilcoxon's rank‐sum test: P‐value = 0.02) and are in agreement with the previously identified pattern of male‐biased dispersal. Our results illustrate the potential of using a combination of noninvasively collected samples at high resolution and specialized SNPs for pedigree‐based dispersal models.     

Environmental dependence of population dynamics and height growth of a subalpine conifer across its vertical distribution: an approach using high‐resolution aerial photographs

Many studies have reported shifts in the altitudinal ranges of plant species in response to recent global warming. However, most studies of tree species have been conducted on a small scale and have focused on tree line ecotones by examining tree rings and age structure on account of the long life spans of the trees. To examine the impact of climate change on forest dynamics at a regional scale, we investigated differences in the population density and canopy height of a Japanese subalpine coniferous species, Abies mariesii, between 1967 and 2003 by analysis of high‐resolution aerial photographs of the Hakkoda Mountains, Honshu, Japan. In 712 plots within the photographs we analyzed which environmental variables (including elevation, aspect, wetness, and distance from moorlands) account for these changes. The population density of A. mariesii decreased below 1000 m a.s.l. and increased above 1300 m a.s.l. It also increased around moorlands, which may provide refugia at low elevations. The rate of increase in canopy height was lowest on the southeastern slopes and on the periphery of the moorlands. The distinct changes in the population density of A. mariesii at its distribution limits probably reflect the responses of the population to climatic changes during three decades. Areas surrounding the moorlands may offer refugia in spite of the poor growing conditions there.     

Scale morphological variation across the flank in four Tonguefishes species collected from the Gulf of Oman (Pleuronectiforms; Cynoglossidae)

The scale morphology of pleuronectiforms in the Gulf of Oman remains insufficiently known. This study used light microscopy and morphological analysis to examine scale variation across the flank of four Tonguefishes species; Cynoglossus arel, C. bilineatus, C. lingua, and C. puncticeps. Scales were extracted from six flank regions, three on the eyed and blind sides, respectively. The most differentiated species was C. arel, which showed significant differences in four size variables in five regions. In Cynoglossus arel and C. lingua, the scales of the eyed side were ctenoid, and those scales from the blind side were cycloid; C. puncticeps have ctenoid scales on both flank sides and C. bilineatus has cycloid scales on both sides. All species' scales on the blind side have fewer ctenial spines (except in C. bilineatus). This study indicated that scale morphology demonstrated considerable variation among the flank regions of the examined species. As a result, the scales from the head and the trunk regions of the eyed side and the scales from the head region of the blind side have a good power of species separation in this family.     

Urban land use limits regional bumble bee gene flow

Potential declines in native pollinator communities and increased reliance on pollinator‐dependent crops have raised concerns about native pollinator conservation and dispersal across human‐altered landscapes. Bumble bees are one of the most effective native pollinators and are often the first to be extirpated in human‐altered habitats, yet little is known about how bumble bees move across fine spatial scales and what landscapes promote or limit their gene flow. In this study, we examine regional genetic differentiation and fine‐scale relatedness patterns of the yellow‐faced bumble bee, Bombus vosnesenskii, to investigate how current and historic habitat composition impact gene flow. We conducted our study across a landscape mosaic of natural, agricultural and urban/suburban habitats, and we show that B. vosnesenskii exhibits low but significant levels of differentiation across the study system (F_ST = 0.019, D_est = 0.049). Most importantly, we reveal significant relationships between pairwise F_ST and resistance models created from contemporary land use maps. Specifically, B. vosnesenskii gene flow is most limited by commercial, industrial and transportation‐related impervious cover. Finally, our fine‐scale analysis reveals significant but declining relatedness between individuals at the 1–9 km spatial scale, most likely due to local queen dispersal. Overall, our results indicate that B. vosnesenskii exhibits considerable local dispersal and that regional gene flow is significantly limited by impervious cover associated with urbanization.