Northerly Sites Research Articles

Global change explains reduced seeding in a widespread New Zealand tree: indigenous Tūhoe knowledge informs mechanistic analysis

IntroductionClimate change is expected to exacerbate the pressures faced by already fragile ecosystems. Negative impacts on the localized and culturally significant plant and animal species within these ecosystems will have cascading effects for the indigenous communities that interact with those species. Understanding how climate change affects culturally important seed crops may be particularly important, as seeds are critical for forest regeneration as well as providing sustenance for wildlife and people. In the central North Island/Te Ika-a-Māui of Aotearoa-New Zealand, Tūhoe elders of the Tuawhenua region have observed declines in seed production by the large-fruited locally dominant forest tree Beilschmiedia tawa (tawa, Lauraceae) over the last half century, which could be related to climate change.MethodsWe used seed trap data from six sites throughout the geographic range of tawa to measure trends in seed crop size from 1986 to 2020 and to determine which weather factors affect seed crops. We then used these weather predictors to hindcast how tawa seeding may have changed in Tuawhenua forests from 1910–2019, based on historic weather data.ResultsSeed trap data showed a decline in seeding through time across tawa’s range, and that seeding was lower at more northerly sites. Seed crops were synchronous among trees within sites, but were strongly asynchronous among sites. High seed crops were associated with cooler summer and winter temperatures, and with high rainfall. In the Tuawhenua region, increases in summer and winter temperatures appear to have contributed to the declines in tawa seed crops observed by elders, with the model predicting that years with heavy fruiting have become less frequent after 1940.DiscussionOur study provides strong evidence that tawa is undergoing changing seedfall patterns in response to changing climate. The biggest weather drivers of seeding that we identified in tawa were winter and summer temperature, both of which were negatively associated with crop size. Both winter and summer temperatures have increased in Tuawhenua in the last 100 years suggesting a possible mechanism to explain observations of long-term declines in tawa seedfall observed by Tūhoe elders of the Tuawhenua region, with ecological and cultural implications.

Divergent Metabolic Changes in Rhizomes of Lowland and Upland Switchgrass (Panicum virgatum) from Early Season through Dormancy Onset.

High-biomass-yielding southerly adapted switchgrasses (Panicum virgatum L.) frequently suffer from unpredictable winter hardiness at more northerly sites arising from damage to rhizomes that prevent effective spring regrowth. Previously, changes occurring over the growing season in rhizomes sampled from a cold-adapted tetraploid upland cultivar, Summer, demonstrated a role for abscisic acid (ABA), starch accumulation, and transcriptional reprogramming as drivers of dormancy onset and potential keys to rhizome health during winter dormancy. Here, rhizome metabolism of a high-yielding southerly adapted tetraploid switchgrass cultivar, Kanlow-which is a significant source of genetics for yield improvement-was studied over a growing season at a northern site. Metabolite levels and transcript abundances were combined to develop physiological profiles accompanying greening through the onset of dormancy in Kanlow rhizomes. Next, comparisons of the data to rhizome metabolism occurring in the adapted upland cultivar Summer were performed. These data revealed both similarities as well as numerous differences in rhizome metabolism that were indicative of physiological adaptations unique to each cultivar. Similarities included elevated ABA levels and accumulation of starch in rhizomes during dormancy onset. Notable differences were observed in the accumulation of specific metabolites, the expression of genes encoding transcription factors, and several enzymes linked to primary metabolism.

Geographical distribution of floating aquatic plants in relation to environmental conditions in southern Quebec, Canada

Communities of free-floating aquatic plants dominated by Lemnaceae (duckweeds) are common in ponds and wetlands globally with important ecological functions. In addition to the cosmopolitan common duckweed (Lemna minor), other species of Lemnaceae, liverworts (Ricciaceae), hornworts (Ceratophyllum), and water ferns (Salviniaceae) often coexist over broad geographic areas. Despite these species all sharing a similar mode of life and resource requirements, they have important morphological and physiological differences such as variation in body size, degree of morphological reduction, presence/number of roots, and position in the water column. The degree to which these differences play a role in shaping their distributions is, however, unclear. We report a field survey of floating aquatic plants in southern Quebec, Canada. We find that species distributions are influenced by habitat specialization to water phosphorus levels. High nutrient specialization followed a continual reduction in body size and morphological complexity, with smaller, simpler species found in higher nutrient sites. We also found a latitudinal gradient in species richness with more northerly sites supporting less diversity. Rare species did not show clustering suggesting that dispersal limitation was not an important factor in determining local abundance. Our results suggest that the distribution of these plants is in part driven by competitive sorting of suitable species from a regional species pool.

Spatial and temporal distribution of cold-water corals in the Northeast Atlantic Ocean over the last 150 thousand years

Scleractinian cold-water corals are found across the Northeast Atlantic, providing structure for important habitats that support high biodiversity. Climate-driven perturbations on parameters such as carbonate chemistry, oxygen, bottom currents, productivity and temperature have the potential to impact the abundance and diversity of these cold-water coral communities. One way to explore the linkage between corals and climate is to examine historic coral distributions during times of past climate change. Previous coral dating efforts in the Northeast Atlantic (n ∼ 700) have focused on reef-forming colonial coral communities from shelf and slope areas. However, there are far fewer data from open-ocean settings or from solitary coral species, thus precluding assessment of basin-wide controls on coral occurrence. Here, we contribute >600 new U-series ages for both solitary and colonial coral species from open-ocean sites including the Reykjanes Ridge and seamounts in the mid and low latitudes to map the changing distribution of Northeast Atlantic cold-water corals over the last 150,000 years. The temporal occurrences of solitary and colonial corals from our offshore sites are broadly similar to the distributions along the nearer-shore sites at the same latitudes. In the cold-temperate and high-latitude Northeast Atlantic, corals are most abundant during warm climate intervals, with the Reykjanes Ridge (60°N) representing the northernmost limit of corals in the Northeast Atlantic during Marine Isotope Stage (MIS) 5, MIS 3 and Bølling-Allerød. This biogeographical distribution expanded northwards to the Norwegian margin at the onset of the Holocene when the ice sheets retreated and modern-like oceanographic conditions were established. We interpret the abundance of corals at these northerly sites to be linked with increased food supply and favourable hydrological conditions. By contrast, coral sites south of 45°N are characterised by glacial and deglacial occurrences, with a marked decline during the Holocene. This distribution is also linked to food supply, potentially driven by shifts in dust fertilization and upwelling, in addition to changes in dissolved oxygen concentration and temperature. Together, these findings emphasize the links between climate, oceanic processes, and cold-water coral distribution, pointing to low food supply and low oxygen concentration as limiting factors for cold-water coral populations. Both parameters are changing in the modern ocean, with implications for future coral communities.

Non-uniform growth dynamics of a dominant boreal tree species (Picea mariana) in the face of rapid climate change

Northwestern Canada’s boreal forest has experienced rapid warming, drying, and changes to permafrost, yet the growth responses and mechanisms driving productivity have been under-studied at broad scales. Forest responses are largely driven by black spruce (Picea mariana (Mill.) B.S.P.) — the region’s most widespread and dominant tree. We collected tree ring samples from four black spruce-dominated sites across 15° of latitude, spanning gradients in climate and permafrost. We investigated (i) differences in growth patterns, (ii) variations in climatic drivers of growth, and (iii) trends in water use efficiency (WUE) through 13C isotope analysis from 1945 to 2006. We found positive growth trends at all sites except those at mid-latitude, where rapid permafrost thaw drove declines. Annual growth was lowest at the tree limit site and highest at the tree line. Climatic drivers of these growth patterns varied; positive growth responses at the northerly sites were associated with warmer winters, whereas Δ13C trends and climate-growth responses at mid-latitude sites indicated that growth was limited by moisture availability. Δ13C signatures indicated increased WUE at the southernmost site, with no significant trends at northern sites. These results suggest that warming will increase the growth of trees at the northern extent of black spruce, but southerly areas may face drought stress if precipitation does not balance evapotranspiration.

Evaluating the potential of red spruce (Picea rubens Sarg.) to persist under climate change using historic provenance trials in eastern Canada

Red spruce (Picea rubens Sarg.) is an important tree species in northeastern North America. The impact of climate change on this tree species is expected to vary regionally, but may be negative within Canada’s eastern Acadian Forest Region as temperatures there are expected to rise by 2–6 °C by 2100 under the business-as-usual Representative Concentration Pathway (RCP) 8.5 climate forcing scenario. In this study, we use one series of historic provenance trials from northeastern North America to evaluate the capacity of red spruce to persist under climate change by analyzing measurements of tree height and diameter at breast height (DBH) in relation to differences between provenance origin climate and test site climate (i.e., climate differentials).Within the range of climate differentials tested, warming (i.e., when the test site was warmer than provenance origin) did not appear to have a deleterious effect on red spruce growth, but cooling (i.e., moving provenances to colder, more northerly sites) did negatively affect growth by reducing height and diameter. Indeed, warmer temperatures, relative to provenance origin, increased tree size, especially for the most northern provenances, suggesting red spruce at the northern extent of its geographical range in northeastern North America is currently cold suppressed and located in non-optimal climates. However, our capacity to test warming effects on more southerly provenances was limited in this study by lack of available test sites south of red spruce’s climatic range. Among the eight climate variables tested, changes in frost free period and mean annual temperature had the most significant impact on tree size. In general, temperature-related climate variables had stronger effects than moisture-related variables. Overall, our results provide important insight for foresters when considering the future management of red spruce in the Acadian Forest Region and the selection of climate adapted seed source.

Make the Adder Count: population trends from a citizen science survey of UK adders

Concern has been growing about the status of UK adder populations, with expert opinion reporting widespread declines. Assessing the true scale of these declines, however, has been hampered by a lack of quantitative data. Make the Adder Count began in 2005 as a national surveillance programme collecting standardised counts of adders lying-out after emerging from hibernation. 260 sites have contributed data, confirming a significant decline, on average, across sites with small populations, while the few with large populations (<10 % of sites) are weakly increasing. If these trends continue, within 15‒20 years, adders will be restricted to a few large population sites, significantly increasing the extinction risk for this priority species in the UK. Public pressure/disturbance was reported as the most frequent negative factor affecting sites, followed by habitat management and habitat fragmentation. Negative impacts from habitat management were reported almost as frequently as positive impacts, suggesting many management plans do not adequately consider the requirements of adders. The dataset also demonstrated earlier emergence among males, in warmer springs and at more northerly sites.

The phenology of the subnivium

The subnivium is a seasonal refuge that exists at the interface between the snowpack and the ground, and provides a haven for a diversity of species to survive extreme winter temperatures. Due to the fitness of many plants and animals being strongly influenced by winter conditions, much attention has been given to changes in the timing of snow cover extent and duration in seasonally snow-covered environments; however, these broad-scale characteristics do not capture the finer-scale dynamics of the subnivium. To study the factors associated with subnivium development, we quantified three critical phenophases of the subnivium: establishment, maintenance, and disintegration along a latitudinal and land cover gradient in the Great Lakes Region of North America. We hypothesized that subnivium phenophases would depend primarily on snow depth and air temperature, but that these would be mediated by latitude and land cover. We found that patterns in both establishment and disintegration were affected by latitude more than land cover, but that variability in the timing of early season snowfall events overrode the effects of both factors in subnivium establishment. In contrast, disintegration was predictably later in more northerly sites, regardless of interannual variation in weather patterns. We found that the subnivium was the result of a balance between ambient temperature, snow depth, and snow density, but that ambient temperatures constrained the system by contributing to the frequency of snowfall and inducing changes in snow depth and density. Areas in lake effect zones, characterized by high snow depths and persistent snow cover, may be the last refugia for subnivia-dependent species given the predicted shifting climate regimes of the 21st century.

Water and energy fluxes over northern prairies as affected by chinook winds and winter precipitation

Chinooks are the North American variety of foehn: strong, warm and dry winds that descend lee mountain slopes. The strong wind speeds, high temperatures and substantial humidity deficits have been hypothesized to remove important prairie near-surface water storage from agricultural fields via evaporation, sublimation and blowing snow, as well as change the phase of near surface water via snowmelt and ground thaw. This paper presents observations of surface energy and water balances from eddy covariance instrumentation deployed at three open sites in southern Alberta, Canada during winter 2011–2012. Energy balances, snow and soil moisture budgets of three select chinook events were analysed in detail. These three events ranged in duration from two to nine days, and are representative of winter through early spring chinooks. Precipitation data from gauges and reanalyses (CaPA and ERA-interim) were used to assess water balances. Variations in precipitation and snowpacks caused the greatest differences in energy and water balances. Cumulative winter precipitation varied by a factor of two over the three sites: heaviest at the more northern site immediately east of the Rocky Mountains and lightest at the easternmost and southernmost site. The temporal progression of chinook-driven surface water loss is explained, beginning with strong blowing snow events through to evaporation of meltwater as snowpacks disappear. At the two sites with considerable winter precipitation and snowcover, large upward latent heat fluxes, often exceeding 100Wm−2, were driven by downward sensible heat fluxes but were unrelated to net radiation. Conversely, at the southernmost site with little snowcover, upward latent heat fluxes were much smaller (less than 50Wm−2) and were associated with periods of positive net radiation. Upward sensible heat fluxes during periods of positive net radiation were observed at this site throughout winter, but were not observed at the more northerly sites until March when the snowcovers ablated. Daily sublimation plus evaporation rates during chinooks at the sites with heaviest and lightest precipitation were 1.3–2.1mm/day and 0.1–0.3mm/day, respectively. Evaporation of soil water occurred while soils were partially to fully unfrozen in November. There was little change in soil water content between fall freeze-up and spring thaw (December through most of March), indicating that over-winter infiltration was balanced by soil water evaporation and both terms were likely to be small. Winter precipitation resulted in only 2% to 4% increases in near-surface water storage at the more northern sites with greater precipitation, whereas there was a net loss over winter at the southernmost site.

Runoff to boreal lakes linked to land cover, watershed morphology and permafrost thaw: a 9‐year isotope mass balance assessment

AbstractStable isotopes of oxygen and hydrogen were measured in water samples collected annually from a representative suite of 50 lakes in northeastern Alberta over a 9‐year period and are interpreted using a steady‐state isotope mass balance model to determine water yield and runoff ratios for the lake watersheds and residence time of the lakes. This isotopic perspective on hydrology of the region provides new insight into the role of land cover, watershed morphometry, climatic drivers and permafrost thaw on lakes. Bog cover, permafrost and presence of thaw features in bogs are found to be the dominant hydrologic drivers, although morphometric properties such as elevation, lake area and drainage basin area are also influential. In addition to quantifying the hydrologic fluxes, the analysis establishes contrasting conditions in more southerly lakes, located in the Stony Mountains and west of Fort McMurray, as compared with more northerly sites in the Birch Mountains, Caribou Mountains and northeast of Fort McMurray, mainly because of contributions from thawing permafrost at the northerly sites. Distinct hydrologic conditions are also noted for Shield systems north of Lake Athabasca where bogs and permafrost are absent. While permafrost thaw is not directly labelled by oxygen and hydrogen isotope composition, isotope mass balance calculations suggest that contributions of up to several hundred millimetres per year are occurring in 14 of the 50 lake watersheds under study. Several of these lakes have water yields in excess of precipitation in some years, and regional groups of lakes display significant correlations between water yield and percentage of bogs that have collapsed. Copyright © 2015 John Wiley & Sons, Ltd.

Trace elements and major ions in atmospheric wet and dry deposition across central Illinois, USA

Measurements of trace elements and major ions in wet and dry deposition were made at eight sites in central Illinois for a 1-month period during the spring/summer season in 2011. During this study, daily-event wet deposition was collected using a commonly utilized sampling train, while 72-h dry deposition collection employed a newly developed artificial turf surrogate surface sampler designed to be more representative of natural deposition surfaces. Results showed considerable intersite variability in the amounts of wet and dry deposition received at sites. Wet deposition loadings of Hg, Pb, S, and As were higher at more southerly network sites due to higher precipitation depths and proximity to sources in the electricity generating and iron and steel manufacturing sectors. Dry deposition loadings of Hg, Pb, S, Cu, Zn, and As were higher at northerly sites, and one urban site had the highest loadings of Pb, S, Cu, and Zn consistent with its proximity (3 km) to very large sources in the electricity generating and iron and steel manufacturing sectors. Enrichment factor analysis showed moderate to high enrichment in both wet and dry deposition samples, suggesting that anthropogenic sources contributed to deposition of many trace elements measured during this study. Analysis of trace element ratios in wet and dry deposition for anthropogenically derived elements provided insight into sources impacting the study sites. Arsenic-sulfur, selenium-sulfur, and mercury-sulfate interrelationships in wet deposition suggested that regional coal combustion sources were impacting receptor sites, while relationships were less pronounced in dry deposition samples suggesting less influence from regional coal combustion sources. In addition to measurements indicating the importance of near field contributions to dry deposition, this study overall demonstrated successful application of a novel method for the direct measurement of trace elements and major ions in the dry component of atmospheric deposition, which may be considered for future studies in other similar emission source regions.

Spatial and temporal variation in the diet of the Pacific sand lance Ammodytes hexapterus in waters off the coast of British Columbia, Canada

Variation in the diet of the Pacific sand lance Ammodytes hexapterus was examined in three years (2009-2011) at four sites in British Columbia, Canada. There were 12 major taxa of prey in diets, eight of which were Crustacea, with copepods being by far the dominant taxon in all 12 site-years. Of the 22 copepod taxa recorded, only Calanus marshallae and Pseudocalanus spp. occurred in all collections, and these two calanoid species dominated diets in terms of frequency of occurrence and total numbers of prey (Pseudocalanus spp. in most collections), and total prey biomass (C. marshallae in all collections). Based on an index of relative importance, C. marshallae was the primary prey at the two southerly sampling sites (Pine and Triangle Islands) and Pseudocalanus spp. at the two northerly sites (Lucy Island and S'Gang Gwaay). Based on an index of dietary overlap, the species composition of the copepod component of A. hexapterus diets overlapped very strongly at the northerly and the southerly pairs of sites in both a cold-water La Niña year (2009) and a warm-water El Niño year (2010), but overall there was more homogeneity amongst all four sites in the La Niña year.

A comparison of NOAA–AVHRR fire data with three Landsat data sets in arid and semi-arid Australia

Burnt area data, derived from the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) imagery, are validated in 11 regions of arid and semi-arid Australia, using three separate Landsat-derived burnt area data sets. Mapping accuracy of burnt extent is highly variable between areas and from year to year within the same area. Where there are corresponding patches in the AVHRR and Landsat data sets, the fit is good. However, the AVHRR data set misses some large patches. Overall, 63% of the Landsat burnt area is also mapped in the AVHRR data set, but this varies from 0% to 89% at different sites. In total, 81% of the AVHRR burnt area data are matched in the Landsat data set, but range from 0% to 94%. The lower match rates (<50%) are generally when little area has burnt (0–500 km2), with figures generally better in the more northerly sites. Results of regressions analysis based on 10 km × 10 km cells are also variable, with R 2 values ranging from 0.37 (n = 116) to 0.94 (n = 85). For the Tanami Desert scene, R 2 varies from 0.41 to 0.61 (n = 368) over three separate years. Combining the data results in an R 2 of 0.60 (n = 1315) (or 0.56 with the intercept set to 0). The slopes of the regressions indicate that mapping the burnt area from AVHRR imagery underestimates the ‘true’ extent of burning for all scenes and years. Differences in mapping accuracy between low and high fire years are examined, as well as the influence of soil, vegetation, land use and tenure on mapping accuracy. Issues which are relevant to mapping fire in arid and semi-arid environments and discontinuous fuels are highlighted.

Methane observations from the Greenhouse Gases Observing SATellite: Comparison to ground‐based TCCON data and model calculations

We report new short‐wave infrared (SWIR) column retrievals of atmospheric methane (XCH4) from the Japanese Greenhouse Gases Observing SATellite (GOSAT) and compare observed spatial and temporal variations with correlative ground‐based measurements from the Total Carbon Column Observing Network (TCCON) and with the global 3‐D GEOS‐Chem chemistry transport model. GOSAT XCH4 retrievals are compared with daily TCCON observations at six sites between April 2009 and July 2010 (Bialystok, Park Falls, Lamont, Orleans, Darwin and Wollongong). GOSAT reproduces the site‐dependent seasonal cycles as observed by TCCON with correlations typically between 0.5 and 0.7 with an estimated single‐sounding precision between 0.4–0.8%. We find a latitudinal‐dependent difference between the XCH4 retrievals from GOSAT and TCCON which ranges from 17.9 ppb at the most northerly site (Bialystok) to −14.6 ppb at the site with the lowest latitude (Darwin). We estimate that the mean smoothing error difference included in the GOSAT to TCCON comparisons can account for 15.7 to 17.4 ppb for the northerly sites and for 1.1 ppb at the lowest latitude site. The GOSAT XCH4 retrievals agree well with the GEOS‐Chem model on annual (August 2009 – July 2010) and monthly timescales, capturing over 80% of the zonal variability. Differences between model and observed XCH4 are found over key source regions such as Southeast Asia and central Africa which will be further investigated using a formal inverse model analysis.

Assessment of assisted migration effects on spring bud flush in white spruce (Picea glauca[Moench] Voss) seedlings

In a changing climate, delaying the time of bud flush may be advantageous to boreal forest species to reduce the risk of spring frost damage. In this study, we examined the potential effect of assisted migration of tree seed on time to bud flush for white spruce. Flushing times of seedlings from 23 white spruce provenances from Ontario were observed under varying temperature conditions simulated in controlled environment chambers. Results indicated that time to bud flush varied considerably among provenances. Although higher temperatures significantly promoted bud flushing for all provenances, provenance-by-temperature interactions were negligible, indicating stable performance of white spruce provenances for this adaptive trait. Spatial patterns of variation among provenances in bud flushing were not consistent with patterns found in range-wide provenance tests. Assisted migration of tree seed across relatively short distances is unlikely to delay bud flushing time in white spruce. Some southern populations may flush earlier at more northerly sites, which would exacerbate spring frost risk. Tree improvement may be an effective approach to utilize amongand withinprovenance variation to enhance this fitness trait for better climatic adaptation.

Occupancy modeling of Black-backed Woodpeckers on burned Sierra Nevada forests

The Black-backed Woodpecker (Picoides arcticus) has been designated by the USDA Forest Service as a management indicator species for snags in burned conifer forests of the Sierra Nevada of California, USA. However, little is known about the characteristics that affect between-fire and within-fire habitat selection by the species in the region. Here we report on the first broad-scale survey of Black-backed Woodpeckers on wildfire-affected forests of the Sierra Nevada. We implemented a Bayesian hierarchical model to: 1) estimate Black-backed Woodpecker occupancy probability in fire areas burned within a time window of 1–10 years; 2) identify relationships between occupancy probability and habitat covariates (fire age, change in canopy cover pre-to-post fire, and snag basal area), elevation, and latitude; and 3) estimate detection probability and relate it to survey interval length and survey type (passive v. broadcast). We included random fire-area effects in our model of occupancy probability to accommodate clusters of non-independent points surveyed within the larger set of fire areas. Mean occupancy probability was estimated to be 0.097. Elevation (after controlling for latitude) had the strongest effect on occupancy probability (higher occupancy at higher elevation) followed by latitude (higher occupancy at northerly sites). Fire age was also important; occupancy probability was about 4× higher on the youngest compared to oldest fires. Although the direction of regression coefficients were in the expected direction (positive), snag basal area and canopy cover change were of minor importance in affecting occupancy probability. There was some indication, however, that the importance of snag basal area increased with fire age. Weak links between occupancy and canopy cover change suggested the species uses a range of burn severities, and such heterogeneity may promote habitat longevity. Our estimate of overall detection probability (across all survey intervals) was 0.772. We found strong effects of survey interval length (higher for longer interval) and, especially survey type (higher for broadcast survey) on detection probability. Our modeling framework and implementation illustrates the flexibility of the Bayesian hierarchical approach for handling complexities such as estimating derived parameters (and variances) and modeling random effects, and should prove generally useful for occupancy studies.

Transcriptomic responses to salinity stress in invasive and native blue mussels (genus Mytilus)

The invasive marine mussel Mytilus galloprovincialis has displaced the native congener Mytilus trossulus from central and southern California, but the native species remains dominant at more northerly sites that have high levels of freshwater input. To determine the extent to which interspecific differences in physiological tolerance to low salinity might explain limits to the invasive species' biogeography, we used an oligonucleotide microarray to compare the transcriptional responses of these two species to an acute decrease in salinity. Among 6777 genes on the microarray, 117 genes showed significant changes that were similar between species, and 12 genes showed significant species-specific responses to salinity stress. Osmoregulation and cell cycle control were important aspects of the shared transcriptomic response to salinity stress, whereas the genes with species-specific expression patterns were involved in mRNA splicing, polyamine synthesis, exocytosis, translation, cell adhesion, and cell signalling. Forty-five genes that changed expression significantly during salinity stress also changed expression during heat stress, but the direction of change in expression was typically opposite for the two forms of stress. These results (i) provide insights into the role of changes in gene expression in establishing physiological tolerance to acute decreases in salinity, and (ii) indicate that transcriptomic differences between M.galloprovincialis and M.trossulus in response to salinity stress are subtle and involve only a minor fraction of the overall suite of gene regulatory responses.

Phenotypic changes and reduced genetic diversity have accompanied the rapid decline of the garden tiger moth (Arctia caja) in the U.K.

Abstract 1. Previous studies have quantified the recent decline of numerous Lepidopteran species in the U.K., including the garden tiger moth (Arctia caja), in which abundance has decreased by 85% over the past 30 years. At the same time that overall numbers have been falling, the distribution of abundance of this species has been moving northwards. In this study, morphological and genetic data were used to investigate the possibility that these changes in abundance and distribution have been accompanied by microevolutionary changes.2. A comparison of wing size and shape in current and historical moth samples revealed that wing shape has altered significantly over the past century, resulting in longer, narrower hindwings and narrower forewings for a given forewing length. Habitat fragmentation and increased suitability of northerly sites provide a plausible explanation for the selection of increasingly dispersive individuals.3. Mitochondrial DNA revealed no phylogeographic structuring either before or after the population decline. However, a comparison of mtDNA haplotypes from current and museum specimens indicated that the recent population decline across the U.K. has been accompanied by a significant loss of genetic diversity.4. The changes in wing shape suggest recent adaptation to environmental change, whereas a loss of genetic diversity may limit the ability of garden tiger moths to adapt to future environmental change.

Particle size/composition relationships of wind‐eroding sediments, Owens (dry) Lake, California, USA

AbstractMajor, minor, and trace element concentrations were determined by particle‐induced x‐ray emission (PIXE) in 118 aeolian sediment samples collected at six heights in seven locations along a 1.2 km transect during three sequential dust storms at Owens (dry) Lake, California, USA. Na and S concentrations covaried with each other (and inversely with Si and Ca), increased with height, and decreased with distance downwind and time. Mg, Al, Si, K, Mn, Fe, and Sr concentrations at northerly sites varied with height and location as opposed to nearly constant concentrations at southerly locations. Volumetric particle‐size distribution (PSD) for each sample was determined via laser diffraction. PSDs of the collected sediment reflected a trimodal distribution:63% of samples peaked at 20–50 µm (silt), 11% at 50–100 µm (very fine sand) and 26% at 100–250 µm (fine sand). Most silty samples occurred during the first two events. Significant differences in element concentrations existed in relation to the PSDs. Na and S concentrations were proportional to the submicron to silt particle fraction during each event. Al, Ti, Mn, K, Fe, and Rb concentrations correlated with 100–500 µm (fine/medium sand) particles in the first two events and a wider PSD range 250–1000 µm (coarse sand) in the third event. The results suggest sodium sulfate aerosol emission during the first windstorm, while subsequent saltation‐dominated events released more aluminosilicate minerals containing higher trace metal concentrations. These combined techniques reveal particle size/chemical fractionation and spatial variability of sediment properties during resuspension at aeolian ‘hotspots,’ with implications to geochemical cycling and aerosol source/receptor relationships. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Polychlorinated biphenyls, DDT, polybrominated diphenyl ethers, and organic pesticides in United Kingdom harbor seals (Phoca vitulina)—mixed exposures and thyroid homeostasis

Polychlorinated biphenyls, DDT and its metabolites, polybrominated diphenyl ethers, and selected organochlorine pesticide concentrations were measured in blubber samples from 60 free-living harbor seals in 2003 from five sites around the United Kingdom coast. Significant regional differences among contaminant levels were found, with seals on Islay and Jura (southwest Scotland) having the highest levels of polychlorinated biphenyls and seals in the Wash (eastern England) having the highest polybrominated diphenyl ether levels. Animals from the north and northeast of Scotland (Orkney and the Moray Firth) had the lowest levels of all the contaminant groups studied. Congener-specific profiles of polychlorinated biphenyls and polybrominated diphenyl ethers showed relatively higher levels of the lower chlorinated and brominated compounds at the more northerly sites, with the lowest total levels of both chemical groups. Significant positive relationships between blubber contaminants and total triiodothyronine (TT3) concentrations were found after controlling for the potential effects of confounding because of sex, mass, and season. Increased serum TT3 levels were significantly related to higher blubber contaminant concentrations in the following order: sum of all contaminants > polybrominated diphenyl ethers > polychlorinated biphenyls > DDT. Serum TT3 levels in the harbor seals with the highest exposures might be indicative of a T3 thyrotoxicosis, but without information on free T3 and circulating thyroid-stimulating hormone levels, it is difficult to determine the importance of this observation for the health of the individuals or populations. However, the mixture of contaminants to which United Kingdom harbor seals are exposed has changed over the last few decades, and the toxicological and epidemiological importance of adding the brominated compounds to the classical organochlorine and heavy metal mixture is not known.