bluuebunny/crossref_metadata_2025 huggingface dataset:
Salinization triggers a trophic cascade in experimental freshwater communities with varying food‐chain length
Authors: Hintz William D. , Mattes Brian M. , Schuler Matthew S. , Jones Devin K. , Stoler Aaron B. , Lind Lovisa , Relyea Rick A.
Published: December 2016

The application of road deicing salts in northern regions worldwide is changing the chemical environment of freshwater ecosystems. Chloride levels in many lakes, streams, and wetlands exceed the chronic and acute thresholds established by the United States and Canada for the protection of freshwater biota. Few studies have identified the impacts of deicing salts in stream and wetland communities and none have examined impacts in lake communities. We tested how relevant concentrations of road salt (15, 100, 250, 500, and 1000 mg Cl−/L) interacted with experimental communities containing two or three trophic levels (i.e., no fish vs. predatory fish). We hypothesized that road salt and fish would have a negative synergistic effect on zooplankton, which would then induce a trophic cascade. We tested this hypothesis in outdoor mesocosms containing filamentous algae, periphyton, phytoplankton, zooplankton, several macroinvertebrate species, and fish. We found that the presence of fish and high salt had a negative synergistic effect on the zooplankton community, which in turn caused an increase in phytoplankton. Contributing to the magnitude of this trophic cascade was a direct positive effect of high salinity on phytoplankton abundance. Cascading effects were limited with respect to impacts on the benthic food web. Periphyton and snail grazers were unaffected by the salt‐induced trophic cascade, but the biomass of filamentous algae decreased as a result of competition with phytoplankton for light or nutrients. We also found direct negative effects of high salinity on the biomass of filamentous algae and amphipods (Hyalella azteca) and the mortality of banded mystery snails (Viviparus georgianus) and fingernail clams (Sphaerium simile). Clam mortality was dependent on the presence of fish, suggesting a non‐consumptive interactive effect with salt. Our results indicate that globally increasing concentrations of road salt can alter community structure via both direct and indirect effects.
Prescribed burning consumes key forest structural components: implications for landscape heterogeneity
Authors: Holland Greg J. , Clarke Michael F. , Bennett Andrew F.
Published: December 2016

Prescribed burning to achieve management objectives is a common practice in fire‐prone regions worldwide. Structural components of habitat that are combustible and slow to develop are particularly susceptible to change associated with prescribed burning. We used an experimental, “whole‐landscape” approach to investigate the effect of differing patterns of prescribed burning on key habitat components (logs, stumps, dead trees, litter cover, litter depth, and understorey vegetation). Twenty‐two landscapes (each ~100 ha) were selected in a dry forest ecosystem in southeast Australia. Experimental burns were conducted in 16 landscapes (stratified by burn extent) while six served as untreated controls. We measured habitat components prior to and after burning. Landscape burn extent ranged from 22% to 89% across the 16 burn treatments. With the exception of dead standing trees (no change), all measures of habitat components declined as a consequence of burning. The degree of loss increased as the extent to which a landscape was burned also increased. Prescribed burning had complex effects on the spatial heterogeneity (beta diversity) of structural components within landscapes. Landscapes that were more heterogeneous pre‐fire were homogenized by burning, while those that were more homogenous pre‐fire tended to display greater differentiation post‐burning. Thus, the notion that patch mosaic burning enhances heterogeneity at the landscape‐scale depends on prior conditions. These findings have important management implications. Where prescribed burns must be undertaken, effects on important resources can be moderated via control of burn characteristics (e.g., burn extent). Longer‐term impacts of prescribed burning will be strongly influenced by the return interval, given the slow rate at which some structural components accumulate (decades to centuries). Management of habitat structural components is important given the critical role they play in (1) provision of habitat resources for diverse organisms, (2) retention of moisture and nutrients in otherwise dry, low‐productivity systems, and (3) carbon storage.
Getting to the core: Internal body temperatures help reveal the ecological function and thermal implications of the lions’ mane
Authors: Trethowan Paul , Fuller Andrea , Haw Anna , Hart Tom , Markham Andrew , Loveridge Andrew , Hetem Robyn , du Preez Byron , Macdonald David W.
Published: December 2016

It has been proposed that there is a thermal cost of the mane to male lions, potentially leading to increased body surface temperatures (Ts), increased sperm abnormalities, and to lower food intake during hot summer months. To test whether a mane imposes thermal costs on males, we measured core body temperature (Tb) continuously for approximately 1 year in 18 free‐living lions. There was no difference in the 24‐hr maximum Tb of males (n = 12) and females (n = 6), and males had a 24‐hr mean Tb that was 0.2 ± 0.1°C lower than females after correcting for seasonal effects. Although feeding on a particular day increased 24‐hr mean and 24‐hr maximum Tb, this phenomenon was true of both male and female lions, and females had higher 24‐hr mean and 24‐hr maximum Tb than males, on both days when lions did not feed, and on days when lions did feed. Twenty‐four‐hour Tb was not influenced by mane length or color, and 24‐hr mean Tb was negatively correlated with mane length. These data contradict the suggestion that there exists a thermal cost to male lions in possessing a long dark mane, but do not preclude the possibility that males compensate for a mane with increased heat loss. The increased insulation caused by a mane does not necessarily have to impair heat loss by males, which in hot environments is primarily through respiratory evaporative cooling, nor does in necessarily lead to increased heat gain, as lions are nocturnal and seek shade during the day. The mane may even act as a heat shield by increasing insulation. However, dominant male lions frequent water points more than twice as often as females, raising the possibility that male lions are increasing water uptake to facilitate increased evaporative cooling. The question of whether male lions with manes compensate for a thermal cost to the mane remains unresolved, but male lions with access to water do not have higher Tb than females or males with smaller manes.
An exotic parasitoid provides an invasional lifeline for native parasitoids
Authors: Konopka Joanna K. , Haye Tim , Gariepy Tara , Mason Peter , Gillespie David , McNeil Jeremy N.
Published: December 2016

The introduction of an exotic species may alter food webs within the ecosystem and significantly affect the biodiversity of indigenous species at different trophic levels. It has been postulated that recent introduction of the brown marmorated stinkbug (Halyomorpha halys (Stål)) represents an evolutionary trap for native parasitoids, as they accept H. halys egg masses as a host but produce no viable progeny. Interspecific interactions between European egg parasitoid, Trissolcus cultratus (Mayr), and an Asian parasitoid, Trissolcus japonicus (Ashmead), were assessed by providing egg masses to T. cultratus at various time intervals following the initial parasitization by T. japonicus. The suitability of the host for the parasitoid development was re‐assessed by providing T. cultratus with fresh and frozen egg masses of various ages. The likelihood of T. cultratus being able to attack previously parasitized egg masses was determined by assessing the duration of egg mass guarding behavior by T. japonicus following parasitization. The results of experiments examining the interspecific interactions between a native European egg parasitoid, T. cultratus, and an Asian parasitoid, T. japonicus (a candidate for the biological control of H. halys), showed that the native species can act as facultative hyperparasitoid of the exotic one. Although this is only possible during certain stages of T. japonicus development, the presence of the introduced parasitoid may reduce the impact of the evolutionary trap for indigenous parasitoid species. There is a possibility that the occurrence of facultative hyperparasitism between scelionid parasitoids associated with stinkbugs is common. This resulting intraguild predation could promote conservation and stabilization of natural communities by impacting the diversity and population dynamics of native stinkbugs and their parasitoids (e.g., by allowing native parasitoids to avoid wasting reproductive effort on unsuitable hosts), or reduce success of biological control programs (e.g., by reducing the population size of the exotic parasitoids).
Quantitative evaluation of hybridization and the impact on biodiversity conservation
Authors: van Wyk Anna M. , Dalton Desiré L. , Hoban Sean , Bruford Michael W. , Russo Isa‐Rita M. , Birss Coral , Grobler Paul , van Vuuren Bettine Janse , Kotzé Antoinette
Published: December 2016

Anthropogenic hybridization is an increasing conservation threat worldwide. In South Africa, recent hybridization is threatening numerous ungulate taxa. For example, the genetic integrity of the near‐threatened bontebok (Damaliscus pygargus pygargus) is threatened by hybridization with the more common blesbok (D. p. phillipsi). Identifying nonadmixed parental and admixed individuals is challenging based on the morphological traits alone; however, molecular analyses may allow for accurate detection. Once hybrids are identified, population simulation software may assist in determining the optimal conservation management strategy, although quantitative evaluation of hybrid management is rarely performed. In this study, our objectives were to describe species‐wide and localized rates of hybridization in nearly 3,000 individuals based on 12 microsatellite loci, quantify the accuracy of hybrid assignment software (STRUCTURE and NEWHYBRIDS), and determine an optimal threshold of bontebok ancestry for management purposes. According to multiple methods, we identified 2,051 bontebok, 657 hybrids, and 29 blesbok. More than two‐thirds of locations contained at least some hybrid individuals, with populations varying in the degree of introgression. HYBRIDLAB was used to simulate four generations of coexistence between bontebok and blesbok, and to optimize a threshold of ancestry, where most hybrids will be detected and removed, and the fewest nonadmixed bontebok individuals misclassified as hybrids. Overall, a threshold Q‐value (admixture coefficient) of 0.90 would remove 94% of hybrid animals, while a threshold of 0.95 would remove 98% of hybrid animals but also 8% of nonadmixed bontebok. To this end, a threshold of 0.90 was identified as optimal and has since been implemented in formal policy by a provincial nature conservation agency. Due to widespread hybridization, effective conservation plans should be established and enforced to conserve native populations that are genetically unique.
A before–after control–impact assessment to understand the potential impacts of highway construction noise and activity on an endangered songbird
Authors: Long Ashley M. , Colón Melanie R. , Bosman Jessica L. , Robinson Dianne H. , Pruett Hannah L. , McFarland Tiffany M. , Mathewson Heather A. , Szewczak Joseph M. , Newnam J. Cal , Morrison Michael L.
Published: December 2016

Anthropogenic noise associated with highway construction and operation can have individual‐ and population‐level consequences for wildlife (e.g., reduced densities, decreased reproductive success, behavioral changes). We used a before–after control–impact study design to examine the potential impacts of highway construction and traffic noise on endangered golden‐cheeked warblers (Setophaga chrysoparia; hereafter warbler) in urban Texas. We mapped and monitored warbler territories before (2009–2011), during (2012–2013), and after (2014) highway construction at three study sites: a treatment site exposed to highway construction and traffic noise, a control site exposed only to traffic noise, and a second control site exposed to neither highway construction or traffic noise. We measured noise levels at varying distances from the highway at sites exposed to construction and traffic noise. We examined how highway construction and traffic noise influenced warbler territory density, territory placement, productivity, and song characteristics. In addition, we conducted a playback experiment within study sites to evaluate acute behavioral responses to highway construction noises. Noise decreased with increasing distance from the highways. However, noise did not differ between the construction and traffic noise sites or across time. Warbler territory density increased over time at all study sites, and we found no differences in warbler territory placement, productivity, behavior, or song characteristics that we can attribute to highway construction or traffic noise. As such, we found no evidence to suggest that highway construction or traffic noise had a negative effect on warblers during our study. Because human population growth will require recurring improvements to transportation infrastructure, understanding wildlife responses to anthropogenic noise associated with the construction and operation of roads is essential for effective management and recovery of prioritized species.
An exception to the matched filter hypothesis: A mismatch of male call frequency and female best hearing frequency in a torrent frog
Authors: Zhao Longhui , Wang Jichao , Yang Yue , Zhu Bicheng , Brauth Steven E. , Tang Yezhong , Cui Jianguo
Published: December 2016

The matched filter hypothesis proposes that the tuning of auditory sensitivity and the spectral character of calls will match in order to maximize auditory processing efficiency during courtship. In this study, we analyzed the acoustic structure of male calls and both male and female hearing sensitivities in the little torrent frog (Amolops torrentis), an anuran species who transmits acoustic signals across streams. The results were in striking contradiction to the matched filter hypothesis. Auditory brainstem response results showed that the best hearing range was 1.6–2 kHz consistent with the best sensitive frequency of most terrestrial lentic taxa, yet completely mismatched with the dominant frequency of conspecific calls (4.3 kHz). Moreover, phonotaxis tests show that females strongly prefer high‐frequency (4.3 kHz) over low‐frequency calls (1.6 kHz) regardless of ambient noise levels, although peripheral auditory sensitivity is highest in the 1.6–2 kHz range. These results are consistent with the idea that A. torrentis evolved from nonstreamside species and that high‐frequency calls evolved under the pressure of stream noise. Our results also suggest that female preferences based on central auditory system characteristics may evolve independently of peripheral auditory system sensitivity in order to maximize communication effectiveness in noisy environments.
Ecological genomics of local adaptation inCornus floridaL. by genotyping by sequencing
Authors: Pais Andrew L. , Whetten Ross W. , Xiang Qiu‐Yun (Jenny)
Published: December 2016

Discovering local adaptation, its genetic underpinnings, and environmental drivers is important for conserving forest species. Ecological genomic approaches coupled with next‐generation sequencing are useful means to detect local adaptation and uncover its underlying genetic basis in nonmodel species. We report results from a study on flowering dogwood trees (Cornus florida L.) using genotyping by sequencing (GBS). This species is ecologically important to easternUSforests but is severely threatened by fungal diseases. We analyzed subpopulations in divergent ecological habitats within North Carolina to uncover loci under local selection and associated with environmental–functional traits or disease infection. At this scale, we tested the effect of incorporating additional sequencing before scaling for a broader examination of the entire range. To test for biases ofGBS, we sequenced two similarly sampled libraries independently from six populations of three ecological habitats. We obtained environmental–functional traits for each subpopulation to identify associations with genotypes via latent factor mixed modeling (LFMM) and gradient forests analysis. To test whether heterogeneity of abiotic pressures resulted in genetic differentiation indicative of local adaptation, we evaluatedFstper locus while accounting for genetic differentiation between coastal subpopulations and Piedmont‐Mountain subpopulations. Of the 54 candidate loci with sufficient evidence of being under selection among both libraries, 28–39 were Arlequin–BayeScanFstoutliers. ForLFMM, 45 candidates were associated with climate (of 54), 30 were associated with soil properties, and four were associated with plant health. Reanalysis of combined libraries showed that 42 candidate loci still showed evidence of being under selection. We conclude environment‐driven selection on specific loci has resulted in local adaptation in response to potassium deficiencies, temperature, precipitation, and (to a marginal extent) disease. High allele turnover along ecological gradients further supports the adaptive significance of loci speculated to be under selection.
The large X‐effect on secondary sexual characters and the genetics of variation in sex comb tooth number in Drosophila subobscura
Authors: Mittleman Briana E. , Manzano‐Winkler Brenda , Hall Julianne B. , Korunes Katharine L. , Noor Mohamed A. F.
Published: December 2016

Genetic studies of secondary sexual traits provide insights into whether and how selection drove their divergence among populations, and these studies often focus on the fraction of variation attributable to genes on the X‐chromosome. However, such studies may sometimes misinterpret the amount of variation attributable to the X‐chromosome if using only simple reciprocal F1 crosses, or they may presume sexual selection has affected the observed phenotypic variation. We examined the genetics of a secondary sexual trait, male sex comb size, in Drosophila subobscura. This species bears unusually large sex combs for its species group, and therefore, this trait may be a good candidate for having been affected by natural or sexual selection. We observed significant heritable variation in number of teeth of the distal sex comb across strains. While reciprocal F1 crosses seemed to implicate a disproportionate X‐chromosome effect, further examination in the F2 progeny showed that transgressive autosomal effects inflated the estimate of variation associated with the X‐chromosome in the F1. Instead, the X‐chromosome appears to confer the smallest contribution of all major chromosomes to the observed phenotypic variation. Further, we failed to detect effects on copulation latency or duration associated with the observed phenotypic variation. Overall, this study presents an examination of the genetics underlying segregating phenotypic variation within species and illustrates two common pitfalls associated with some past studies of the genetic basis of secondary sexual traits.
Geographical structure, narrow species ranges, and Cenozoic diversification in a pantropical clade of epiphyllous leafy liverworts
Authors: Bechteler Julia , Schäfer‐Verwimp Alfons , Lee Gaik Ee , Feldberg Kathrin , Pérez‐Escobar Oscar Alejandro , Pócs Tamás , Peralta Denilson F. , Renner Matthew A. M. , Heinrichs Jochen
Published: December 2016

The evolutionary history and classification of epiphyllous cryptogams are still poorly known. Leptolejeunea is a largely epiphyllous pantropical liverwort genus with about 25 species characterized by deeply bilobed underleaves, elliptic to narrowly obovate leaf lobes, the presence of ocelli, and vegetative reproduction by cladia. Sequences of three chloroplast regions (rbcL, trnL‐F, psbA) and the nuclear ribosomal ITS region were obtained for 66 accessions of Leptolejeunea and six outgroup species to explore the phylogeny, divergence times, and ancestral areas of this genus. The phylogeny was estimated using maximum‐likelihood and Bayesian inference approaches, and divergence times were estimated with a Bayesian relaxed clock method. Leptolejeunea likely originated in Asia or the Neotropics within a time interval from the Early Eocene to the Late Cretaceous (67.9 Ma, 95% highest posterior density [HPD]: 47.9–93.7). Diversification of the crown group initiated in the Eocene or early Oligocene (38.4 Ma, 95% HPD: 27.2–52.6). Most species clades were established in the Miocene. Leptolejeunea epiphylla and L. schiffneri originated in Asia and colonized African islands during the Plio‐Pleistocene. Accessions of supposedly pantropical species are placed in different main clades. Several monophyletic morphospecies exhibit considerable sequence variation related to a geographical pattern. The clear geographic structure of the Leptolejeunea crown group points to evolutionary processes including rare long‐distance dispersal and subsequent speciation. Leptolejeunea may have benefitted from the large‐scale distribution of humid tropical angiosperm forests in the Eocene.
Latitudinal variation in sexual dimorphism in life‐history traits of a freshwater fish
Authors: Estlander Satu , Kahilainen Kimmo K. , Horppila Jukka , Olin Mikko , Rask Martti , Kubečka Jan , Peterka Jiří , Říha Milan , Huuskonen Hannu , Nurminen Leena
Published: December 2016

Sexual dimorphism is common across the animal kingdom, but the contribution of environmental factors shaping differences between the sexes remains controversial. In ectotherms, life‐history traits are known to correlate with latitude, but sex‐specific responses are not well understood. We analyzed life‐history trait variation between the sexes of European perch (Perca fluviatilis L.), a common freshwater fish displaying larger female size, by employing a wide latitudinal gradient. We expected to find sex‐dependent latitudinal variation in life‐history variables: length at age, length increment, and size at maturity, with females showing consistently higher values than males at all latitudes. We further anticipated that this gender difference would progressively decrease with the increasingly harsh environmental conditions toward higher latitude. We hypothesized that growth and length increment would decrease and size/age at maturity would increase at higher latitudes. Our results confirmed female‐biased sexual size dimorphism at all latitudes and the magnitude of sexual dimorphism diminished with increase in latitude. Growth of both sexes decreased with increase in latitude, and the female latitudinal clines were steeper than those of males. Hence, we challenge two predominant ecological rules (Rensch's and Bergmann's rules) that describe common large‐scale patterns of body size variation. Our data demonstrate that these two rules are not universally applicable in ectotherms or female‐biased species. Our study highlights the importance of sex‐specific differences in life‐history traits along a latitudinal gradient, with evident implications for a wide range of studies from individual to ecosystems level.
Size selection by a gape‐limited predator of a marine snail: Insights into magic traits for speciation
Authors: Boulding Elizabeth G. , Rivas María José , González‐Lavín Nerea , Rolán‐Alvarez Emilio , Galindo Juan
Published: December 2016

The intertidal snailLittorina saxatilishas repeatedly evolved two parallel ecotypes assumed to be wave adapted and predatory shore crab adapted, but the magnitude and targets of predator‐driven selection are unknown. In Spain, a small, wave ecotype with a large aperture from the lower shore and a large, thick‐shelled crab ecotype from the upper shore meet in the mid‐shore and show partial size‐assortative mating. We performed complementary field tethering and laboratory predation experiments; the first set compared the survival of two different size‐classes of the crab ecotype while the second compared the same size‐class of the two ecotypes. In the first set, the large size‐class of the crab ecotype survived significantly better than the small size‐class both on the upper shore and in the laboratory. In the second set, the small size‐class of the crab ecotype survived substantially better than that of the wave ecotype both on the upper shore and in the laboratory. Shell‐breaking predation on tethered snails was almost absent within the lower shore. In the laboratory shore crabs (Pachygrapsus marmoratus) with larger claw heights selected most strongly against the small size‐class of the crab ecotype, whereas those with medium claw heights selected most strongly against the thin‐shelled wave ecotype. Sexual maturity occurred at a much larger size in the crab ecotype than in the wave ecotype. Our results showed that selection on the upper shore for rapid attainment of a size refuge from this gape‐limited predator favors large size, thick shells, and late maturity. Model parameterization showed that size‐selective predation restricted to the upper shore resulted in the evolution of the crab ecotype despite gene flow from the wave ecotype snails living on the lower shore. These results on gape‐limited predation and previous ones showing size‐assortative mating between ecotypes suggest that size may represent a magic trait for the thick‐shelled ecotype.
Life cycle matters: DNA barcoding reveals contrasting community structure between fern sporophytes and gametophytes
Authors: Nitta Joel H. , Meyer Jean‐Yves , Taputuarai Ravahere , Davis Charles C.
Published: December 2016

Ferns are the only major lineage of vascular plants that have nutritionally independent sporophyte (diploid) and gametophyte (haploid) life stages. However, the implications of this unique life cycle for fern community ecology have rarely been considered. To compare patterns of community structure between fern sporophytes and gametophytes, we conducted a survey of the ferns of the islands of Moorea and Tahiti (French Polynesia). We first constructed a DNA barcode library (plastid rbcL and trnH‐psbA) for the two island floras including 145 fern species. We then used these DNA barcodes to identify more than 1300 field‐collected gametophytes from 25 plots spanning an elevational gradient from 200 to 2000 m. We found that species richness of fern sporophytes conforms to the well‐known unimodal (i.e., mid‐elevation peak) pattern, reaching a maximum at ~1000–1200 m. Moreover, we found that fern sporophyte communities become increasingly phylogenetically clustered at high elevations. In contrast, species richness of fern gametophytes was consistent across sites, and gametophytes showed no correlation of phylogenetic community structure with elevation. Turnover of sporophyte and gametophyte communities was closely linked with elevation at shallow phylogenetic levels, but not at deeper nodes in the tree. Finally, we found several species for which gametophytes had broader ranges than sporophytes, including a vittarioid fern with abundant gametophytes but extremely rare sporophytes. Our study highlights the importance of including diverse life history stages in surveys of community structure, and has implications for the possible impacts of climate change on the distribution of fern diversity.
Understanding and predicting physiological performance of organisms in fluctuating and multifactorial environments
Authors: Koussoroplis Apostolos‐Manuel , Pincebourde Sylvain , Wacker Alexander
Published: December 2016

Understanding how variance in environmental factors affects physiological performance, population growth, and persistence is central in ecology. Despite recent interest in the effects of variance in single biological drivers, such as temperature, we have lacked a comprehensive framework for predicting how the variances and covariances between multiple environmental factors will affect physiological rates. Here, we integrate current theory on variance effects with co‐limitation theory into a single unified conceptual framework that has general applicability. We show how the framework can be applied (1) to generate mathematically tractable predictions of the physiological effects of multiple fluctuating co‐limiting factors, (2) to understand how each co‐limiting factor contributes to these effects, and (3) to detect mechanisms such as acclimation or physiological stress when they are at play. We show that the statistical covariance of co‐limiting factors, which has not been considered before, can be a strong driver of physiological performance in various ecological contexts. Our framework can provide powerful insights on how the global change‐induced shifts in multiple environmental factors affect the physiological performance of organisms.
Changes in community phylogenetic structure in a North American forest chronosequence
Authors: Pastore Abigail I. , Scherer Brendan P.
Published: December 2016

Several studies of succession in tropical and subtropical climates include phylogenetic analyses of the plant communities; the majority of these studies find a shift from more closely related to less closely related assemblages over succession. It has been suggested that this pattern indicates a shift from abiotic to biotic filters structuring communities over time, but there is considerable debate surrounding this interpretation. Conducting analyses for multiple components of plant assemblages can provide insight into the processes structuring communities. Here, we present community phylogenetic analyses of a deciduous forest chronosequence for three community components: standing vegetation, seed bank, and vegetation regenerated after small‐scale disturbance. We constructed a phylogeny from 228 taxa present in the community data of a chronosequence obtained from previously published research. In the standing vegetation, we found a shift from more closely related to less closely related vegetation over the chronosequence. These results are consistent with other studies of chronosequences in tropical forests, lending support to the ubiquity of such shifts in relatedness over succession under different climatic conditions. However, the seed bank and vegetation regenerated after small‐scale disturbance showed no consistent pattern with stand age, suggesting recruits are experiencing different forces than surrounding vegetation. These phylogenetic analyses of seed banks and vegetation regenerated after small‐scale disturbance over a chronosequence provide additional evidence into the mechanisms driving forest succession.
Predicting conifer establishment post wildfire in mixed conifer forests of the North American Mediterranean‐climate zone
Authors: Welch Kevin R. , Safford Hugh D. , Young Truman P.
Published: December 2016

Due to fire suppression policies, timber harvest, and other management practices over the last century, many low‐ to mid‐elevation forests in semiarid parts of the western United States have accumulated high fuel loads and dense, multi‐layered canopies that are dominated by shade‐tolerant and fire‐sensitive conifers. To a great extent, the future status of western US forests will depend on tree species’ responses to patterns and trends in fire activity and fire behavior and postfire management decisions. This is especially the case in the North American Mediterranean‐climate zone (NAMCZ), which supports the highest precipitation variability in North America and a 4‐ to 6‐month annual drought, and has seen greater‐than‐average increases in air temperature and fire activity over the last three decades. We established 1490 survey plots in 14 burned areas on 10 National Forests across a range of elevations, forest types, and fire severities in the central and northern NAMCZ to provide insight into factors that promote natural tree regeneration after wildfires and the differences in postfire responses of the most common conifer species. We measured site characteristics, seedling densities, woody shrub, and tree growth. We specified a zero‐inflated negative binomial mixed model with random effects to understand the importance of each measured variable in predicting conifer regeneration. Across all fires, 43% of all plots had no conifer regeneration. Ten of the 14 fires had median conifer seedling densities that did not meet Forest Service stocking density thresholds for mixed conifer forests. When regeneration did occur, it was dominated by shade‐tolerant but fire‐sensitive firs (Abies spp.), Douglas‐fir (Pseudotsuga menziesii) and incense cedar (Calocedrus decurrens). Seedling densities of conifer species were lowest in sites that burned at high severity, principally due to the biotic consequences of high severity fire, for example, increased distances to live seed trees and competition with fire‐following shrubs. We developed a second model specifically for forest managers and restoration practitioners who work in yellow pine and mixed conifer forests in the central NAMCZ to assess potential natural regeneration in the years immediately following a fire, allowing them to prioritize which areas may need active postfire forest restoration and supplemental planting.
Ecosystem resilience is evident 17 years after fire in Wyoming big sagebrush ecosystems
Authors: Ellsworth L. M. , Wrobleski D. W. , Kauffman J. B. , Reis S. A.
Published: December 2016

Recent policy has focused on prevention of wildfire in the sagebrush steppe in an effort to protect habitat for the greater sage grouse (Centrocercus urophasianus). Historically, fire return intervals in Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) ecosystems were 50–100 yr or more, but invasive species, climate change, and a legacy of intensive grazing practices have led to degraded rangeland condition, altered fire regimes and fire effects, and declines in sagebrush cover. Little is known about the long‐term impacts of fire in this ecosystem in areas where grazing pressure has been removed, few invasive species exist, and fire return intervals are maintained. In this study, we quantified vegetation composition prior to prescribed burning, 1 year following fire, and 17 years after fire in a native‐dominated Wyoming big sagebrush ecosystem at Hart Mountain National Antelope Refuge, Oregon, United States. Seventeen years following fire, the ecosystem was dominated by native herbaceous vegetation, with 8.3% cover of broad‐leaved forbs and bunchgrasses in the understory, compared to just 3.8% cover of native herbaceous vegetation in unburned controls. Invasive annual grass cover ranged from 0.2% to 8.4% across all treatments and years (P = 0.56). One year following fire, the distance from a randomly located point and the nearest mature sagebrush was 16.6 m, but by 17 years after the fire, that distance had decreased to 2.5 m. Seventeen years after fires, shrub cover was 0.4–4% in burned plots compared to 13–24% in unburned controls. Collectively, these data demonstrate that good condition ungrazed Wyoming big sagebrush plant communities exhibited resilience following fire and maintained a native‐dominated mosaic of shrubs, bunchgrasses, and forbs. Further, unburned control plots were dominated by woody vegetation and exhibited losses in herbaceous understory, possibly indicating that they are outside of their natural fire return interval. Our results illustrate that management of all habitat components, including natural disturbance and a mosaic of successional stages, is important for persistent resilience and that suppression of all fires in the sagebrush steppe may create long‐term losses of heterogeneity in good condition Wyoming big sagebrush ecosystems.
Growth rate and resource imbalance interactively control biomass stoichiometry and elemental quotas of aquatic bacteria
Authors: Godwin Casey M. , Whitaker Emily A. , Cotner James B.
Published: December 2016

The effects of resource stoichiometry and growth rate on the elemental composition of biomass have been examined in a wide variety of organisms, but the interaction among these effects is often overlooked. To determine how growth rate and resource imbalance affect bacterial carbon (C): nitrogen (N): phosphorus (P) stoichiometry and elemental content, we cultured two strains of aquatic heterotrophic bacteria in chemostats at a range of dilution rates and P supply levels (C:P of 100:1 to 10,000:1). When growing below 50% of their maximum growth rate, P availability and dilution rate had strong interactive effects on biomass C:N:P, elemental quotas, cell size, respiration rate, and growth efficiency. In contrast, at faster growth rates, biomass stoichiometry was strongly homeostatic in both strains (C:N:P of 70:13:1 and 73:14:1) and elemental quotas of C, N, and P were tightly coupled (but not constant). Respiration and cell size increased with both growth rate and P limitation, and P limitation induced C accumulation and excess respiration. These results show that bacterial biomass stoichiometry is relatively constrained when all resources are abundant and growth rates are high, but at low growth rates resource imbalance is relatively more important than growth rate in controlling bacterial biomass composition.
Polydatin and its derivatives inhibit fatty acid desaturases in microorganisms
Authors: Řezanka Tomáš , Vítová Milada , Kolouchová Irena , Nedbalová Linda , Doležalová Jana , Palyzová Andrea , Sigler Karel
Published: December 2016

Antioxidant plant polyphenols resveratrol and its glycoside polydatin at 500 μg/L were found to have two distinct effects on yeasts and algae depending on the cell content of polyunsaturated fatty acids (PUFA). In yeasts that do not produce PUFA, resveratrol (0.5 mg/L) increased resistance to biosynthesized ethanol (an important property in winemaking) to 22% EtOH in Saccharomyces cerevisiae and 14% EtOH in Torulaspora delbrückii, the fatty acid content being changed only slightly, whereas in the PUFA‐producing algae Desmodesmus quadricauda and Euglena gracilis both compounds act as inhibitors of Δ4 desaturases blocking the formation of both even‐ and odd‐numbered PUFA having the first double‐bond in position 4. This leads to the biotechnologically desirable accumulation of the health‐beneficial polyunsaturated fatty acids (PUFAs), docosapentaenoic (DPA), and docosahexaenoic acid (DHA).

Practical applications: Employing natural stilbene compounds has far‐reaching use in biotechnological applications such as the production of ethanol used for biofuels or production of wine and beer. It allows the production of beer with higher alcohol content, without resorting to the use of consumer‐unacceptable genetically modified yeast. In brewing, when the yeast is often repeatedly reused to ferment fresh wort, higher resistance of yeast in the presence of these compounds can lead to an increase in the number of yeast reuses and thereby reduce economic costs of the brewery needed for preparation of inocula. Using polydatin as inhibitor of Δ4 desaturase in Euglena and Desmodesmus algae blocks the biosynthesis of both even‐ and odd‐numbered PUFAs having a double bond in position 4. This leads to a change in the content of fatty acids and accumulation of biosynthetic precursors, e.g., 22:5n‐3 acid that has more favorable pharmacological effects than docosahexaenoic acid (22:6n‐3)

Natural stilbenes such as polydatin and resveratrol have not yet been known as inhibitors of desaturases. We found that they alter the fatty acid composition in microorganisms containing PUFA (algae) by inhibiting Δ4 desaturase and thus blocking the biosynthesis of specific PUFAs. Inhibition of Δ4 desaturase produces oils with a higher proportion of DPA. Moreover, these compounds increase yeast resistance to ethanol.
Porphyrin‐Catalyzed Photochemical C–H Arylation of Heteroarenes
Authors: Rybicka‐Jasińska Katarzyna , König Burkhard , Gryko Dorota
Published: December 2016

Organic dyes are a promising class of photoredox catalysts and offer a meaningful alternative to broadly applied Ru and Ir complexes. We found that porphyrins with tuned physicochemical properties, by tailoring various substituents at the periphery of the macrocycle, are effective in catalyzing the light‐induced direct arylation of heteroarenes and coumarins with diazonium salts. Mechanistic studies confirmed that the reaction operates by an oxidative quenching pathway of the porphyrin.
Methylsulfenylation of Electrophilic Carbon Atoms: Reaction Development, Scope, and Mechanism
Authors: Pereira Adriane A. , Pereira Amanda S. , de Mello Amanda C. , Carpanez Arthur G. , Horta Bruno A. C. , Amarante Giovanni W.
Published: December 2016

An innovative method for the methylsulfenylation of electrophilic carbons was explored. Cheap and commercially available dimethyl sulfoxide (DMSO) was used as a source of the –SCH3 group. Chalcone, dibenzylideneacetone, and Morita–Baylis–Hillman adduct derivatives were successfully sulfenylated to give the corresponding products in moderate to high yields. Control experiments and DFT calculations revealed deoxygenation of DMSO and nucleophilic addition of a sulfur intermediate as key steps in the entire mechanism.
Voltammetric and Spectrophotometric Studies on DNA Interacting with Daunorubicin and its Amidino Derivatives
Authors: Palinska‐Saadi Adriana , Lukasiewicz Magdalena , Oszczapowicz Janusz , Lukawska Malgorzata , Oszczapowicz Irena , Zwierkowska Elzbieta , Achmatowicz Selim , Maj‐Zurawska Magdalena
Published: December 2016

Daunorubicin (DAU) is one of the anticancer drugs widely applied in therapy although it reveals high toxicity. As a result of the search for new derivatives of anthracyclines with better biological properties, amidino antracyclines were invented. They contain in the daunosamine moiety an amidine group, –N=CR–NR1R2 where −NR1R2 is the rest of the cyclic secondary amine, instead of the −NH2 group. DAU and its two formamidino derivatives, the one containing the rest of the morpholine in the formamidine group (DAU‐Fmor) and the other one containing the rest of the hexamethyleneimine (DAU‐Fhex) were selected for voltammetric and spectrophotometric investigation of their interactions with DNA. These interactions were investigated by monitoring the changes in the UV/Vis absorption spectra of the anthracyclines interacting with oligonucleotides in the solution, as well as by monitoring the changes in electrochemical properties of oligonucleotides interacting with anthracyclines on the surface of screen‐printed graphite electrodes (SPEs) using square wave voltammetry (SWV). The obtained results indicate that interactions between DNA and anthracyclines depend mainly on two factors: the DNA sequence and the detailed structure of the anthracycline. As a result of these interactions, the anthracycline absorbance and the oxidation current of both, guanine and adenine change. The relations between these changes and the structure of the investigated anthracyclines are discussed.
Scaling‐up camera traps: monitoring the planet's biodiversity with networks of remote sensors
Authors: Steenweg Robin , Hebblewhite Mark , Kays Roland , Ahumada Jorge , Fisher Jason T , Burton Cole , Townsend Susan E , Carbone Chris , Rowcliffe J Marcus , Whittington Jesse , Brodie Jedediah , Royle J Andrew , Switalski Adam , Clevenger Anthony P , Heim Nicole , Rich Lindsey N
Published: December 2016

Countries committed to implementing the Convention on Biological Diversity's 2011–2020 strategic plan need effective tools to monitor global trends in biodiversity. Remote cameras are a rapidly growing technology that has great potential to transform global monitoring for terrestrial biodiversity and can be an important contributor to the call for measuring Essential Biodiversity Variables. Recent advances in camera technology and methods enable researchers to estimate changes in abundance and distribution for entire communities of animals and to identify global drivers of biodiversity trends. We suggest that interconnected networks of remote cameras will soon monitor biodiversity at a global scale, help answer pressing ecological questions, and guide conservation policy. This global network will require greater collaboration among remote‐camera studies and citizen scientists, including standardized metadata, shared protocols, and security measures to protect records about sensitive species. With modest investment in infrastructure, and continued innovation, synthesis, and collaboration, we envision a global network of remote cameras that not only provides real‐time biodiversity data but also serves to connect people with nature.
Hepatostat: Liver regeneration and normal liver tissue maintenance
Authors: Michalopoulos George K.
Published: December 2016

In contrast to all other organs, liver‐to‐body‐weight ratio needs to be maintained always at 100% of what is required for body homeostasis. Adjustment of liver size to 100% of what is required for homeostasis has been called “hepatostat.” Removal of a portion of any other organ is followed with local regeneration of a limited degree, but it never attempts to reach 100% of the original size. The complex mechanisms involved in this uniquely hepatic process encompass a variety of regenerative pathways that are specific to different types of injury. The most studied form of liver regeneration (LR) is that occurring after loss of hepatocytes in a single acute injury, such as rodent LR after two‐thirds partial hepatectomy or administration of damaging chemicals (CCl4, acetaminophen, etc.). Alternative regenerative pathways become activated when normal regeneration is thwarted and trigger the appearance of “progenitor” cells. Chronic loss of hepatocytes is associated with regenerative efforts characterized by continual hepatocyte proliferation and often has adverse consequences (development of cirrhosis or liver cancer). Even though a very few hepatocytes proliferate at any given time in normal liver, the mechanisms involved in the maintenance of liver weight by this slow process in the absence of liver injury are not as well understood. (Hepatology 2017;65:1384‐1392)