Prediction of benthic macroinvertebrate composition using microhabitat characteristics derived from stereo photography

1. Benthic macroinvertebrate community and habitat features varying at the microscale ( 0.09 m ² ) were measured on one sampling occasion in the Thredbo River, Kosciusko National Park, NSW, Australia.
2. Most of the substratum habitat variables were measured in three dimensions using stereo photography. This is the first time that this method has been used so extensively for this purpose in freshwater ecology.
3. Microhabitat variables most related to benthic macroinvertebrate distribution and abundance were selected with multivariate analyses included rock length, height, area and water velocity. Individual variables alone could not account for macroinvertebrate variation, indicating the importance of interactions among variables.
4. Nine selected habitat variables were used to predict macroinvertebrate taxonomic content of additional sites. Predictions were 87% accurate for taxa with a > 50% chance of occurrence and 93% accuracy for taxa with a > 70% chance of occurrence. Variability observed in macroinvertebrate assemblages at the time of sampling was largely physically controlled and highly deterministic.     

Thirty‐eight single nucleotide polymorphism markers for high‐throughput genotyping of chum salmon

We characterize 38 single nucleotide polymorphism genotyping assays for chum salmon (Oncorhynchus keta), an important species for both commercial and subsistence fisheries in western Alaska. These assays are based on the 5′‐nuclease reaction and thus facilitate high‐throughput genotyping with minimal optimization time. Minor allele frequency differences (Δq) among collections were between 0.01 and 0.50 resulting in per locus F_ST estimates of 0.00–0.08 with an average of 0.03.     

Multiple anthropogenic changes cause biodiversity loss through plant invasion

Non‐native invasive plants are a widely acknowledged threat to global biodiversity. However, our understanding of the mechanisms underlying plant invasion, and the relative importance of multiple rather than single drivers, remains poor. Here, we provide a case study using time‐series data to reconstruct patterns of change, and field experiments to test for causality. We show how, over a 50‐year period, a series of unrelated human‐induced changes created highly favorable conditions for the non‐native tree mallow (Lavatera arborea) to turn invasive, causing loss of native vegetation and seabird breeding habitat. The combination of three drivers: human‐introduced disease, climate warming and a fisheries‐mediated increase in seabird populations, removed major constraints on plant population growth, (i.e. grazer control, climatic control, germination opportunity and nutrient limitation). Collectively, these changes created optimal conditions for the rapid expansion of tree mallow. The resulting dramatic impact on both the native vegetation and breeding seabirds, notably puffins (Fratercula arctica), exemplifies how non‐native invasive plant species can transform terrestrial ecosystems. While climate change is regarded as a key factor behind plant invasion, we highlight that multiple rather than single factors may be critical to biodiversity loss.     

Genomic consequences of interspecific Pinus spp. hybridization

Strong karotypic orthoselection does not fully account for genome size variation in pines. Adult F1 interspecific pine hybrids are fertile and the genomic consequences of hybridization can be studied using haploid female megagametophytes. Greater variation in genome size was hypothesized to occur in hybrids compared to their parental species and the variation was thought to be positively related to the phylogenetic distance between the parental species. Nuclear 1C DNA content of megagametophytes from four sets of fertile Pinus spp. F1 hybrids and their parents was determined using a laser flow cytometer. Fertile F1 hybrids included two sets of hard pine hybrid Pinus elliottii Engelm. x P. caribaea var. hondurensis Morelet and two Asian x New World soft pine hybrids P. wallichiana A.B. Jacks. x P. strobus L. (hybrid is known as P. x schwerinii ) and P. lambertiana Dougl. x P. armandii Franchlet. Fertile, adult F1 produce haploid megagametophytes with nuclear DNA contents comparable to the parents or parental species. One genomic consequence of hybridization in pines is stability in nuclear DNA content. Hybrid genomes neither increased or decreased DNA content regardless of the phylogenetic distance between parents. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 75 , 503–508.     

Evaluating Mule Deer Body Condition Using Serum Thyroid Hormone Concentrations

ABSTRACT Body condition of ungulates is a determinant of fecundity and survival rates. Ultrasonography and body condition scoring techniques allow reliable estimation of body fat but may not be feasible to employ in some circumstances. A reliable blood chemistry index for assessing relative condition of different ungulate populations or groups would be useful in ongoing population monitoring programs. We provided a nutrition supplement (treatment) to a group of free-ranging mule deer (Odocoileus hemionus) during 2 consecutive winters in southwest Colorado. In late February each year, we evaluated whether percent body fat and serum concentrations of total thyroxine (T4), total triiodothyronine (T3), free thyroxine (FT4), and free triiodothyronine (FT3) were higher among treatment deer than an adjacent group of deer that did not receive treatment (control). As a corroborative analysis, we modeled body fat as a function of thyroid hormone concentrations and morphometric variables. Estimated body fat of treatment deer averaged 12.3% (SE = 0.327), whereas estimated body fat of control deer averaged 7.0% (SE = 0.333) during the 2 winters of study. Concentrations of T4 and FT4 averaged 48.07 nanomole/L (SE = 3.80) and 12.61 picomole/L (SE = 1.04) higher, respectively, in treatment deer than control deer. Our optimal model of estimated body fat included T4, T4², FT4, and deer chest girth (%FAT = −4.8015 − 0.0946 × T4 + 0.000603 × T4² + 0.1474 × FT4 + 0.1426 × chest girth, R² = 0.609). Serum thyroid hormones effectively discerned treatment deer from control deer and were related to estimated body fat. Ultrasound and body condition scoring should be used to estimate body fat whenever possible. However, in cases where only a blood sample can be obtained, we documented potential utility of T4 and FT4 during late winter for evaluating relative body condition of mule deer.     

Water vapour fluxes and their impact under elevated CO2 in a C4-tallgrass prairie

We measured leaf-level stomatal conductance, xylem pressure potential, and stomate number and size as well as whole plant sap flow and canopy-level water vapour fluxes in a C4-tallgrass prairie in Kansas exposed to ambient and elevated CO₂. Stomatal conductance was reduced by as much as 50% under elevated CO₂ compared to ambient. In addition, there was a reduction in stomate number of the C4 grass, Andropogon gerardii Vitman, and the C3 dicot herb, Salvia pitcheri Torr., under elevated CO₂ compared to ambient. The result was an improved water status for plants exposed to elevated CO₂ which was reflected by a less negative xylem pressure potential compared to plants exposed to ambient CO₂. Sap flow rates were 20 to 30% lower for plants exposed to elevated CO₂ than for those exposed to ambient CO₂. At the canopy level, evapotranspiration was reduced by 22% under elevated CO₂. The reduced water use by the plant canopy under elevated CO₂ extended the photosynthetically-active period when water became limiting in the ecosystem. The result was an increased above- and belowground biomass production in years when water stress was frequent.     

Changes in Fatty Acid Composition of Phospholipids from Different Ages of Potato Seed-tubers During Sprouting

The relative growth rate of plants from 7-month-old potato seed-tuberswas significantly greater (37%) than that from 19-month-oldseed-tubers. To determine if loss in seed-tuber phospholipidcontent, and thus membrane integrity, is associated with age-reducedvigour, changes in fatty acyl composition of free fatty acid(FA) and phospholipid fractions were characterized in both seed-tuberages over a 19-d interval of plant establishment. The concentration(nmol g d. wt^–1) of saturated and unsaturated FA withinthe phosphatidylcholine (PC) and phosphatidylethanolamine (PE)pools decreased an average of 27-fold over the initial 7 d ofestablishment. This decline was followed by a 19-fold (on average)increase to day 19. The change with time in saturated and unsaturatedFA concentration within the free FA pool was quadratic, butwas opposite to that displayed by the two phospholipid pools.The close correlation in fatty acyl content between the phospholipidand free FA fractions suggested high phospholipase activityduring early plant establishment. The double-bond index (DBI)of all three lipid fractions decreased from day 0 to 7 and thenincreased to day 19. More importantly, in older seed-tubers,the minima in phospholipid DBI and content occurred significantlyearlier (on a plant developmental scale) than in younger seed-tubers.A premature decrease in DBI is indicative of loss of membraneintegrity in potato, and undoubtedly has implications for efficiencyof substrate mobilization and energy metabolism during plantestablishment. Potatoes (Solanum tuberosum L.), seed-tuber age, lipids, plant growth potential     

Night-time transpiration can decrease hydraulic redistribution

C₃ plants dominate many landscapes and are critically important for ecosystem water cycling. At night, plant water losses can include transpiration (E_night) from the canopy and hydraulic redistribution (HR) from roots. We tested whether E_night limits the magnitude of HR in a greenhouse study using Artemisia tridentata , Helianthus anomalus and Quercus laevis . Plants were grown with their roots split between two compartments. HR was initiated by briefly withholding all water, followed by watering only one rooting compartment. Under study conditions, all species showed substantial E_night and HR (highest minus lowest soil water potential [ Ψ _s] during a specified diel period). Suppressing E_night by canopy bagging increased HR during the nightly bagging period (HR_N) for A. tridentata and H. anomalus by 73 and 33% respectively, but did not affect HR_N by Q. laevis . Total daily HR (HR_T) was positively correlated with the Ψ _s gradient between the rooting compartments, which was correlated with light and/or atmospheric vapour pressure deficit (VPDa) the prior day. For A. tridentata , HR_T was negatively correlated with night-time VPDa. Ecological implications of the impact of E_night on HR may include decreased plant productivity during dry seasons, altered ecosystem water flux patterns and reduced nutrient cycling in drying soils.     

Microgeographic life history variation in an alpine caddisfly: plasticity in response to seasonal time constraints

1. Temporally constrained environments, such as habitats with short growth seasons or short hydroperiods, cause potentially strong selection on life histories. Depending on the predictability of these events and the extent of spatial and temporal heterogeneity, local populations could become adapted either via a fixed phenotype or via life history plasticity in response to these environmental cues. 2. We used a common garden experiment to investigate microgeographic variation in life history responses to combined changes in photoperiod (ambient/late) and hydroperiod (constant/drying) time constraint cues in an alpine caddisfly (Trichoptera). We compared six populations (three permanent/three temporary streams) originating from a small, alpine floodplain and which spanned an expected gradient in growth period duration (GPD) with distance from glaciers. 3. We made two main predictions in relation to locally varying selection pressures: (i) populations nearest glaciers (shorter GPD and strongest time constraints) should have the fastest development rates and (ii) populations from permanent streams should be less able to respond to drying hydroperiods than populations from temporary streams. 4. All populations and both sexes accelerated development in response to late season photoperiod cues. However, only permanent stream populations showed an increase in development time with increasing GPD, suggesting that other factors were influencing populations in temporary streams. 5. Permanent stream populations showed countergradient variation (genetic and environmental influences were in opposition) in development time, and under‐compensation of growth rates resulted in a converse Bergmann cline in body size (smaller body size along gradients of declining season length). The extent of plasticity in response to hydroperiod, and the combined effects of both time constraints, differed between populations and sexes, but were not consistent among populations. 6. Taken together, our results suggest adaptive plasticity in response to season length. The lack of a predictable pattern in response to hydroperiod may be due to gene flow or weak selection. We conclude that spatially structured populations can strongly differ in phenotypic plasticity even at microgeographic scales.