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91.
A. Joshua Leffler Karen H. Beard Katharine C. Kelsey Ryan T. Choi Joel A. Schmutz Jeffrey M. Welker 《Global Change Biology》2019,25(1):277-289
The advancement of spring and the differential ability of organisms to respond to changes in plant phenology may lead to “phenological mismatches” as a result of climate change. One potential for considerable mismatch is between migratory birds and food availability in northern breeding ranges, and these mismatches may have consequences for ecosystem function. We conducted a three‐year experiment to examine the consequences for CO2 exchange of advanced spring green‐up and altered timing of grazing by migratory Pacific black brant in a coastal wetland in western Alaska. Experimental treatments represent the variation in green‐up and timing of peak grazing intensity that currently exists in the system. Delayed grazing resulted in greater net ecosystem exchange (NEE) and gross primary productivity (GPP), while early grazing reduced CO2 uptake with the potential of causing net ecosystem carbon (C) loss in late spring and early summer. Conversely, advancing the growing season only influenced ecosystem respiration (ER), resulting in a small increase in ER with no concomitant impact on GPP or NEE. The experimental treatment that represents the most likely future, with green‐up advancing more rapidly than arrival of migratory geese, results in NEE changing by 1.2 µmol m?2 s?1 toward a greater CO2 sink in spring and summer. Increased sink strength, however, may be mitigated by early arrival of migratory geese, which would reduce CO2 uptake. Importantly, while the direct effect of climate warming on phenology of green‐up has a minimal influence on NEE, the indirect effect of climate warming manifest through changes in the timing of peak grazing can have a significant impact on C balance in northern coastal wetlands. Furthermore, processes influencing the timing of goose migration in the winter range can significantly influence ecosystem function in summer habitats. 相似文献
92.
Joseph Merz Lucius Caldwell Michael Beakes Chris Hammersmark Kirsten Sellheim 《Restoration Ecology》2019,27(3):661-671
Gravel augmentation is often applied to rivers and streams to rehabilitate salmonid spawning and incubation habitat. However, the effect of gravel size on salmon spawning utilization and embryo survival during incubation is not well understood. We conducted an experiment on a regulated and previously mined Northern California salmonid‐bearing stream in which different sized gravel (small, medium, and large) patches were placed into the stream's degraded spawning reach. We documented Oncorhynchus tshawytscha (Chinook salmon) spawning activity within the three gravel sizes for two seasons. In addition, we deployed Chinook salmon embryos into each gravel size patch and allowed them to incubate until estimated emergence time. Although all experimental gravel sizes were predicted to be within the spawning population's mobilization capabilities, model results indicated the probability of salmon building redds decreased as substrate size increased. Conversely, embryo survival increased as gravel size increased. A possible mechanism of disparate Chinook salmon embryo survival is provided by an observed decrease in embryo survival correlating with greater presence of embryo predators (leeches), which are associated with smaller gravel. Our results indicate a parent‐offspring conflict in optimal spawning gravel size for Chinook salmon, and suggest that an intermediate gravel size would maximize overall reproductive success across both spawning and incubation life stages. 相似文献
93.
Jeimy D. Santiago‐Valentín Alma P. Rodríguez‐Troncoso Eric Bautista‐Guerrero Andrs Lpez‐Prez Amilcar L. Cupul‐Magaa 《Invertebrate Biology》2019,138(1):29-39
Porites panamensis is a hermatypic brooder coral endemic to, and distributed along, the Eastern Tropical Pacific, and is considered a species vulnerable to local effects because it has limited capacity for long‐distance dispersal (and low genetic diversity). Although larvae of P. panamensis have been previously shown to recruit to artificial settlement platforms, they have never been observed in the water column. The present study describes the reproductive behavior of P. panamensis, with a focus on using molecular tools to document evidence for a larval planktonic stage and for successful recruitment. Larvae collected from the water column, and recruitment on natural and artificial substrata were documented. Phylogenetic analysis of two ribosomal markers, 18s rRNA and ITS (ITS1‐5.8‐ITS2), and one mitochondrial marker, cytochrome oxidase subunit 1 (cox1), confirmed the taxonomic identity of larvae, and showed that larvae and recruits have genotypes similar to adults of P. panamensis. Lipid vacuoles and Symbiodinium sp. were present in the gastrodermis of all larvae. A total of 12 and 371 recruits settled on artificial and natural substrates, respectively, and the recruitment rate differed significantly over time. By documenting the reproductive success of the species, we show the potential for existing individuals both to maintain the population in the study area and to contribute to maintenance of the coral reef community in the coming decades. 相似文献
94.
Chengfeng Le Shuyu Wu Chuanmin Hu Marcus W. Beck Xuchao Yang 《Global Change Biology》2019,25(10):3485-3493
Global climate change can significantly influence oceanic phytoplankton dynamics, and thus biogeochemical cycles and marine food webs. However, associative explanations based on the correlation between chlorophyll‐a concentration (Chl‐a) and climatic indices is inadequate to describe the mechanism of the connection between climate change, large‐scale atmospheric dynamics, and phytoplankton variability. Here, by analyzing multiple satellite observations of Chl‐a and atmospheric conditions from National Center for Environmental Prediction/National Center for Atmospheric Research reanalysis datasets, we show that high‐latitude atmospheric blocking events over Alaska are the primary drivers of the recent decline of Chl‐a in the eastern North Pacific transition zone. These blocking events were associated with the persistence of large‐scale atmosphere pressure fields that decreased westerly winds and southward Ekman transport over the subarctic ocean gyre. Reduced southward Ekman transport leads to reductions in nutrient availability to phytoplankton in the transition zone. The findings describe a previously unidentified climatic factor that contributed to the recent decline of phytoplankton in this region and propose a mechanism of the top‐down teleconnection between the high‐latitude atmospheric circulation anomalies and the subtropical oceanic primary productivity. The results also highlight the importance of understanding teleconnection among atmosphere–ocean interactions as a means to anticipate future climate change impacts on oceanic primary production. 相似文献
95.
Ronan James O'Sullivan Tutku Aykanat Susan E. Johnston Adam Kane Russell Poole Ger Rogan Paulo A. Prodhl Craig R. Primmer Philip McGinnity Thomas Eric Reed 《Ecology and evolution》2019,9(12):7096-7111
Comparing observed versus theoretically expected evolutionary responses is important for our understanding of the evolutionary process, and for assessing how species may cope with anthropogenic change. Here, we document directional selection for larger female size in Atlantic salmon, using pedigree‐derived estimates of lifetime reproductive success as a fitness measure. We show the trait is heritable and, thus, capable of responding to selection. The Breeder's Equation, which predicts microevolution as the product of phenotypic selection and heritability, predicted evolution of larger size. This was at odds, however, with the observed lack of either phenotypic or genetic temporal trends in body size, a so‐called “paradox of stasis.” To investigate this paradox, we estimated the additive genetic covariance between trait and fitness, which provides a prediction of evolutionary change according to Robertson's secondary theorem of selection (STS) that is unbiased by missing variables. The STS prediction was consistent with the observed stasis. Decomposition of phenotypic selection gradients into genetic and environmental components revealed a potential upward bias, implying unmeasured factors that covary with trait and fitness. These results showcase the power of pedigreed, wild population studies—which have largely been limited to birds and mammals—to study evolutionary processes on contemporary timescales. 相似文献
96.
97.
Tymchuk WE Sundström LF Devlin RH 《Evolution; international journal of organic evolution》2007,61(5):1225-1237
The purpose of this study was to examine, using a rainbow trout (Oncorhynchus mykiss) model system, the fitness consequences of three generations of introgression of genotypes adapted to two different environments (culture and nature). The experiments also isolated the influence of competitive interactions and risk of predation on the relative growth and survival of the wild and backcrossed lines. Line crosses representing fast-growing pure domestic (D), slow-growing pure wild (W), domestic x wild hybrids (F1), F1 x wild backcrosses (B1), and B1 x wild backcrosses (B2) were generated and reared under (1) culture conditions, (2) seminatural conditions with competition among genotypes, and (3) seminatural conditions under risk of predation. Survival of the fry in a seminatural environment with competition fit an additive model of gene action with the domestic fish having the highest survival and the wild fish the lowest, but under risk of predation outbreeding depression was suggested by low survival of the B2 lines. Evidence of a trade-off in growth and survival under risk of predation along with observations of genetically determined behavioral differences among the strains may provide some explanation for the observed differences in survival among the strains. This information is relevant to improving our evolutionary understanding of the interaction among genomes, and the influence of environment, during hybridization events. Results from this experiment indicate that alteration of phenotype likely played a prominent role in the reduced fitness experienced by progeny produced after three generations of introgression, supporting the theory that disruption of genotypes selected for adaptation to local conditions may be a primary cause of outbreeding depression in species such as salmon. 相似文献
98.
M. F. DOCKER G. R. HAAS D. H. GOODMAN S. B. REID D. D. HEATH 《Molecular ecology resources》2007,7(2):350-353
We developed five polymerase chain reaction‐based markers that detect variation in the mitochondrial genome of the Pacific lamprey, Entosphenus tridentatus, across most of its range. Two gene fragments (ND2 and ND5) were amplified and digested with three and two restriction enzymes, respectively, detecting sequence variation at 18 sites (ND2 = 13; ND5 = 5) and yielding 29 composite haplotypes among 1246 lampreys. These sequence‐based markers will be useful in a range of phylogeographical and population genetic studies. 相似文献
99.
Alvinella pompejana, the so-called Pompeii worm (Desbruyères and Laubier, 1980), is found exclusively in association to high temperature venting,
at the surface of hydrothermal chimneys of the East Pacific Rise. The main characteristics of this emblematic species is its
tolerance to high temperature but its ability to colonize extremely hot substrates has been the subject of much controversy.
In the last decade, new tools allowing in situ and in vivo investigation have been determinant in the understanding of the
strategies and adaptations required to colonize such an extremely hot environment. New data relative to the characterization
of the animal habitat conditions, on one hand, to the molecular adaptations of this organism and the colonization processes
by this species, on the other hand, are now available. Advanced methods and tools, that have fostered the physico-chemical
characterization of vent habitats in recent years, are first reviewed. Factors controlling the physico-chemical variability
of vent habitats and the threats A. pompejana might effectively face are discussed. The exceptional thermotolerance of this species and the maximum temperature it could
sustain are then considered in the light of molecular data relative to its collagen stability. Life history traits as well
as biological controls on tube micro-habitat conditions are discussed on the basis of new in situ and in vivo experiments
and characterization. Finally, the current knowledge and opened questions related to the molecular adaptations to chemical
stresses are briefly stated. The ability of Alvinella pompejana to colonize these substrates is far from being fully understood, but the exceptional properties of its extracellular biopolymers
and the behavior of the worm can be now considered as major clues in the colonization process. Alvinella pompejana could thus stand at the limits authorized for its biological machinery in a highly dynamic environment where temperature
can readily reach lethal values, but where temperature regulation by the animal itself would prevent exposure to deleterious
thermal spikes. The dynamic system associating this pioneer species and its associated microflora might be viewed as a key
to the subsequent colonization of these environments by less tolerant species, highlighting A. pompejana as a new type of ecosystem bioengineer. 相似文献
100.
Kyle L. Wilson Colin J. Bailey Trevor D. Davies Jonathan W. Moore 《Global Change Biology》2022,28(1):72-85
Marine and freshwater ecosystems are increasingly at risk of large and cascading changes from multiple human activities (termed “regime shifts”), which can impact population productivity, resilience, and ecosystem structure. Pacific salmon exhibit persistent and large fluctuations in their population dynamics driven by combinations of intrinsic (e.g., density dependence) and extrinsic factors (e.g., ecosystem changes, species interactions). In recent years, many Pacific salmon have declined due to regime shifts but clear understanding of the processes driving these changes remains elusive. Here, we unpacked the role of density dependence, ecosystem trends, and stochasticity on productivity regimes for a community of five anadromous Pacific salmonids (Steelhead, Coho Salmon, Pink Salmon, Dolly Varden, and Coastal Cutthroat Trout) across a rich 40-year time-series. We used a Bayesian multivariate state-space model to examine whether productivity shifts had similarly occurred across the community and explored marine or freshwater changes associated with those shifts. Overall, we identified three productivity regimes: an early regime (1976–1990), a compensatory regime (1991–2009), and a declining regime (since 2010) where large declines were observed for Steelhead, Dolly Varden, and Cutthroat Trout, intermediate declines in Coho and no change in Pink Salmon. These regime changes were associated with multiple cumulative effects across the salmon life cycle. For example, increased seal densities and ocean competition were associated with lower adult marine survival in Steelhead. Watershed logging also intensified over the past 40 years and was associated with (all else equal) ≥97% declines in freshwater productivity for Steelhead, Cutthroat, and Coho. For Steelhead, marine and freshwater dynamics played approximately equal roles in explaining trends in total productivity. Collectively, these changing environments limited juvenile production and lowered future adult returns. These results reveal how changes in freshwater and marine environments can jointly shape population dynamics among ecological communities, like Pacific salmon, with cascading consequences to their resilience. 相似文献