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تاريخ القرن الثامن عشر في أوروبة
يبحث في تاريخ القرن الثامن عشر في أوربا من خلال المصادر والوثائق والمذكرات والقصص والبينات الاجتماعية والحياة الاقتصادية والحكومة والإدارة والملوك والمستدين والتوتر في داخل الدول والجيوش البرية والبحرية والدبلوماسية والعلاقات والدولية، وتوسع روسيا، ويتحدث عن الدول الألمانية وصعود بروسيا، ويدرس إسبانيا وإيطاليا والبحر المتوسط والتنافس الاستعمار وأوربا والعالم والخارجي والتعليم والحياة والفكرية والدين والكنائس.
BOOK
Carbon dynamics of silvopasture systems in the Northeastern United States
Silvopasture is increasingly recognized as a nature-based solution to climate change. However, few studies have quantified the total carbon storage potential of silvopasture in humid continental climates, complicating efforts to understand climate mitigation potential. In this study, we compared the carbon stocks of silvopastures established by afforestation of trees into pastures (silvopasture) with pasture that remained without trees (treeless pasture) on five farms in the Northeastern United States. Total carbon content was measured in the woody, herbaceous, and soil pools for silvopastures and treeless pastures. Results indicate that silvopastures stored 43% more total carbon (136.42 Mg C ha
− 1
) than treeless pastures (95.47 Mg C ha
− 1
), with tree carbon in silvopastures being the driving factor. No significant difference in soil carbon stocks were found between systems across all five study farms. Total carbon content of forages was generally lower in silvopastures (7.24 Mg C ha
− 1
) when compared to treeless pasture (7.84 Mg C ha
− 1
). These findings quantify the additionality of silvopasture as a nature-based carbon storage practice when trees are planted into pasture.
Journal Article
Convergent Evolution of Hemoglobin Function in High-Altitude Andean Waterfowl Involves Limited Parallelism at the Molecular Sequence Level
A fundamental question in evolutionary genetics concerns the extent to which adaptive phenotypic convergence is attributable to convergent or parallel changes at the molecular sequence level. Here we report a comparative analysis of hemoglobin (Hb) function in eight phylogenetically replicated pairs of high- and low-altitude waterfowl taxa to test for convergence in the oxygenation properties of Hb, and to assess the extent to which convergence in biochemical phenotype is attributable to repeated amino acid replacements. Functional experiments on native Hb variants and protein engineering experiments based on site-directed mutagenesis revealed the phenotypic effects of specific amino acid replacements that were responsible for convergent increases in Hb-O2 affinity in multiple high-altitude taxa. In six of the eight taxon pairs, high-altitude taxa evolved derived increases in Hb-O2 affinity that were caused by a combination of unique replacements, parallel replacements (involving identical-by-state variants with independent mutational origins in different lineages), and collateral replacements (involving shared, identical-by-descent variants derived via introgressive hybridization). In genome scans of nucleotide differentiation involving high- and low-altitude populations of three separate species, function-altering amino acid polymorphisms in the globin genes emerged as highly significant outliers, providing independent evidence for adaptive divergence in Hb function. The experimental results demonstrate that convergent changes in protein function can occur through multiple historical paths, and can involve multiple possible mutations. Most cases of convergence in Hb function did not involve parallel substitutions and most parallel substitutions did not affect Hb-O2 affinity, indicating that the repeatability of phenotypic evolution does not require parallelism at the molecular level.
Journal Article
Assessing silvopasture management as a strategy to reduce fuel loads and mitigate wildfire risk
Managing private forests for wildfire resilience is challenging due to conflicting social, economic, and ecological decisions that may result in an increase of surface fuel loads leading to greater fire risk. Due to fire suppression and a changing climate, land managers in fire-prone regions face an increasing threat of high severity fires. Thus, land managers need fuel treatment options that match their forest types and management objectives. One potential option for producers that graze livestock is silvopasture management, where livestock, forages, and overstory vegetation are carefully managed for co-benefits on the same unit of land. This study compared forest composition and structure, fuel types, and vegetative biomass between silvopasture and non-grazed managed forests in Washington, U.S. We show that silvopasture management results in reductions in grass biomass, litter, and duff depth when compared to non-grazed managed forest. These findings point to the integrated nature of silvopasture, where management of overstory composition and structure, understory vegetation, and grazing can reduce fuel loads and potential wildfire risk.
Journal Article
Navigating the trade‐offs between environmental DNA and conventional field surveys for improved amphibian monitoring
The need for efficient, accurate biodiversity monitoring is growing, especially for globally imperiled taxa, such as amphibians. Environmental DNA (eDNA) analysis holds enormous potential for enhancing monitoring programs, but as this tool is increasingly adopted, it is imperative for users to understand its potential benefits and shortcomings. We conducted a comparative study to evaluate the efficacy of two eDNA methodologies (quantitative (q)PCR and metabarcoding) and conventional field sampling approaches (seining, dipnetting, and visual encounter surveys) in a system of 20 ponds containing six different amphibian species. Using an occupancy modeling framework, we estimated differences in detection sensitivity across methods, with a focus on how eDNA survey design could be further optimized. Overall, both metabarcoding and qPCR were competitive with or improved upon conventional methods. Specifically, qPCR (species‐specific approach) was the most effective technique for detecting two rare species, the California tiger salamander (Ambystoma californiense) and California red‐legged frog (Rana draytonii), with a detection probability of >0.80 per survey. Metabarcoding (community approach) estimated amphibian diversity with comparable rates to field techniques on average, and detected an additional 41 vertebrate taxa. However, for two abundant species (western toads, Anaxyrus boreas, and Pacific chorus frogs, Pseudacris regilla), field techniques outperformed metabarcoding, especially as individuals metamorphosed. Our results indicate that eDNA approaches would be most effective when paired with visual encounter surveys to detect terrestrial life stages, and that more optimization, specifically primer choice and validation, is needed. By comparing methods across a diverse set of ponds and species, we provide guidance for future studies integrating eDNA approaches into amphibian monitoring.
Journal Article
Sex-specific resource strategies mediate home range sizes of an endangered carnivore across multiple scales
Home ranges reflect a trade-off between the costs and benefits associated with acquiring resources and are influenced by complex interactions among intrinsic and extrinsic factors. These factors can lead to different spatial and temporal patterns to acquire the necessary resources that meet energetic and reproductive needs. Identifying the drivers of these strategies concurrently across spatiotemporal scales remains rare but is essential for identifying landscape constraints on populations in rapidly changing systems. We examined spatiotemporal drivers of home range size of the federally endangered ocelot (
Leopardus pardalis
; [22 Males, 12 Females]) in the two remaining populations in the USA. Males increased home range size during reproductive periods while females constrained their home range, but increased in size to match the demands of reproduction. Habitat complexity and the associated prey diversity and abundance were related to smaller home range size. Our results suggest that home range variation is a response to environmental conditions and annual changes in life history. Sex-specific drivers of home range size across space and time—in the context of habitat loss, shifting climate patterns, and changing resource productivity—can help identify management and habitat restoration targets for small and declining populations.
Journal Article
The Intentional and Unintentional Human Food Subsidy Landscape for a Large Carnivore
Humans have transformed ecosystems and resource availability. Many species exploit these novel resources, which can increase conflict between humans and wildlife. This is particularly true for large carnivores that readily consume human foods, which can lead to conflict. However, disentangling the different forms of human food subsidies, their drivers across a landscape, and potential consequences for conflict has not been explored. American black bears (Ursus americanus) consume large quantities of unintentional (e.g., refuse, crops) and intentional human food (e.g., hunting bait). Up to 40% of a wild bear's diet can be from human food subsidies. This consumption has been associated with increasing numbers and more conflict. The state of Wisconsin, USA, has a liberal bear baiting policy and high densities of bears compared to neighboring states and has the potential for high consumption of human foods and conflict. We estimated the proportional diets of black bears using stable isotope analysis (δ13C and δ15N) from a statewide sampling in Wisconsin. We modeled the response of diets to landscape variables likely to influence the consumption of either natural food items and two sources of human food subsidies: intentional and unintentional. We then predicted a human subsidy landscape that explored the spatial variation between intentional and unintentional sources and modeled the relationship between human food subsidies and conflict. We found substantial consumption of intentional (7%; 95% CI [0%, 25%]) and unintentional (32%; 95% CI [27%, 38%]) subsidies. The consumption of intentional subsidies increased in areas with public lands and higher hunter activity, while the consumption of unintentional subsidies increased with corn production and less natural land cover. We found the number of reported complaints increased with the consumption of unintentional human subsidies. Our predicted map of human subsidy consumption disentangled the form of the human food subsidy and showed that the consumption of unintentional human food subsidies along their expanding range can lead to greater conflict with people and property. Our mapped subsidy landscape can be used by managers to target management actions to reduce the availability of human subsidies and to predict areas of human‐wildlife interactions. Our findings highlight important differences between the source of human subsidy and how it enters the natural system and leads to human‐wildlife conflict. Ultimately, we can target management actions that influence habitat that can mediate human subsidy consumption and identify areas to implement strategies that promote safe human‐wildlife interactions.
Journal Article
Socioeconomic Benefits of Large Carnivore Recolonization Through Reduced Wildlife‐Vehicle Collisions
The decline of top carnivores has released large herbivore populations around the world, incurring socioeconomic costs such as increased animal–vehicle collisions. Attempts to control overabundant deer in the Eastern United States have largely failed, and deer–vehicle collisions (DVCs) continue to rise at alarming rates. We present the first valuation of an ecosystem service provided by large carnivore recolonization, using DVC reduction by cougars as a case study. Our coupled deer population models and socioeconomic valuations revealed that cougars could reduce deer densities and DVCs by 22% in the Eastern United States, preventing 21,400 human injuries, 155 fatalities, and$2.13 billion in avoided costs within 30 years of establishment. Recently established cougars in South Dakota prevent $ 1.1 million in collision costs annually. Large carnivore restoration could provide valuable ecosystem services through such socio‐ecological cascades, and these benefits could offset the societal costs of coexistence.
Journal Article
Prevalence and diversity of avian blood parasites in a resident northern passerine
Background
Climate-related changes are expected to influence the prevalence and distribution of vector-borne haemosporidian parasites at northern latitudes, although baseline information about resident birds is still lacking. In this study, we investigated prevalence and genetic diversity of
Plasmodium
,
Haemoproteus,
and
Leucocytozoon
parasites infecting the northwestern crow (
Corvus caurinus
), a non-migratory passerine with unique life-history characteristics. This species occupies both intertidal and forested habitats and is subject to high prevalence of avian keratin disorder (AKD), a disease that causes gross beak deformities. Investigation of avian blood parasites in northwestern crows at sites broadly distributed across coastal Alaska provided an opportunity to evaluate specific host factors related to parasite infection status and assess geographical patterns of prevalence.
Results
We used molecular methods to screen for haemosporidian parasites in northwestern crows and estimated genus-specific parasite prevalence with occupancy modeling that accounts for imperfect detection of parasite infection. We observed considerable geographical and annual variation in prevalence of
Plasmodium
,
Haemoproteus
, and
Leucocytozoon
, but these patterns were not correlated with indices of local climatic conditions. Our models also did not provide support for relationships between the probability of parasite infection and body condition or the occurrence of co-infections with other parasite genera or clinical signs of AKD. In our phylogenetic analyses, we identified multiple lineages of each parasite genus, with
Leucocytozoon
showing greater diversity than
Plasmodium
or
Haemoproteus
.
Conclusions
Results from this study expand our knowledge about the prevalence and diversity of avian blood parasites in northern resident birds as well as corvids worldwide. We detected all three genera of avian haemosporidians in northwestern crows in Alaska, although only
Leucocytozoon
occurred at all sites in both years. Given the strong geographical and annual variation in parasite prevalence and apparent lack of correlation with climatic variables, it appears that there are other key factors responsible for driving transmission dynamics in this region. Thus, caution is warranted when using standard climatic or geographical attributes in a predictive framework. Our phylogenetic results demonstrate lower host specificity for some lineages of
Leucocytozoon
than is typically reported and provide insights about genetic diversity of local haemosporidian parasites in Alaska.
Journal Article
Small but connected islands can maintain populations and genetic diversity under climate change
In response to the striking effects of environmental change, conservation strategies often include the identification of conservation areas that can effectively maintain vulnerable species. Consequently, identifying system‐specific conditions that maintain the demographic and genetic viability of species of conservation concern is essential. Connectivity plays a critical role in the persistence of populations. Islands have been model systems to understand connectivity and metapopulation processes and have emerged as particularly favorable targets for conservation. While islands can be isolated from mainland disturbances, it is unknown what degree of isolation is necessary to avoid unfavorable changes but remain sufficiently connected to maintain population viability. To test this question, we explored connectivity within the Apostle Islands, an archipelago of 22 islands within Lake Superior, by comparing historical and contemporary trends in ice bridge connectivity and by simulating the effect of reduced connectivity within this system. We developed a demographically informed individual‐based model to explicitly test the role of connectivity to influence the persistence and genetic diversity of American marten Martes americana, a forest carnivore at risk across its southern range boundary. We found that genetic diversity was resilient to moderate changes in ice cover, but a complete loss of connectivity resulted in rapid genetic erosion. Despite genetic erosion, populations persisted as long as nominal connectivity occurred between islands. Our work suggests that connectivity will decline, but martens would be resilient to moderate changes and, in the short term, the Apostle Islands can act as a refuge along this species' southern range boundary. Identifying thresholds in connectivity that maintain populations but allow for isolation from disturbance will be necessary to identify suitable areas for species conservation across space and time.
Journal Article