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101.
A major factor affecting spring canola (Brassica napus) production in Canada is killing frosts during seedling development in the spring and seed maturation in the fall. The objective
of this study was to explore the possibility of producing spring canola lines with mutations that have altered biochemical
pathways that increase cold tolerance. The approach was to generate UV point mutations in cultured microspores followed by
chemical in vitro selection of individual mutant microspores or embryos resulting in measurable alterations to various biochemical
pathways with elevated levels of key defense signaling molecules such as, salicylic acid (SA), p-Fluoro-d,l-Phenyl Alanine (FPA), and jasmonic acid (JA). In addition, since proline (Pro) is known to protect plant tissues in the cold-induced
osmotic stress pathway, mutants that overproduce Pro were selected in vitro by using three Pro analogues: hydroxyproline (HP),
azetidine-2-carboxylate (A2C); and, 3,4-dehydro-d,l-proline (DP). Of the 329 in vitro selected mutant embryos produced, 74 were identified with significant cold tolerance compared
to their donor parents through indoor freezer tests at −6°C, and 19 had better winter field survival than winter canola checks. All chemically selected mutant doubled haploids with increased
cold tolerance compared well with parent lines for all seed quality and agronomic parameters. Development of increased frost
tolerant cultivars should allow for spring canola to be produced in western Canada without compromising seed quality. 相似文献
102.
Mun Sup Yoon Jeongran Lee Chang Yung Kim Jung Hoon Kang Eun Gi Cho Hyung Jin Baek 《Euphytica》2009,165(1):69-77
Approximately 7,000 accessions of Korean soybean (Glycine max (L.) Merrill) landraces, largely composed of three collections, the Korea Atomic Energy Research Institute’s soybean (KAS),
the Korean Crop Experiment Station’s soybean (KLS) and the Korean Agricultural Development and Technology Center’s soybean
(KADTC) collections, have been conserved at the Rural Development Administration (RDA) genebank in Korea. The accessions within
collections were classified based on their traditional uses such as sauce soybean (SA), sprouted soybean (SP), soybean for
cooking with rice (SCR), and OTHERS. A total of 2,758 accessions of Korean soybean landraces were used to profile and to evaluate
genetic structure using six SSR loci. A total of 110 alleles were revealed by at the six SSR loci. The number of alleles per
SSR locus ranged from 9 to 39 in Satt187 and Satt_074, respectively. The number of alleles ranged from 87 in the KADTC collection
to 96 in the KLS collection, and from 63 in the SCR group to 95 in the SP group. Nei’s average genetic diversity ranged from
0.68 to 0.70 across three collections, and 0.64 to 0.69 across the usage groups. The average between-group differentiation
(G
st) was 0.9 among collections, and 4.1 among the usage groups. The similar average diversity among three collections implies
that the genetic background of the three collections was quite similar or that there were a large number of duplicate accessions
in three collections. The selection from the four groups classified based upon usage may be a useful way to select accessions
for developing a Korean soybean landrace core collection at the RDA genebank. DNA profile information of accessions will provide
indications of redundancies or omissions and aid in managing the soybean collection held at the RDA genebank. The information
on diversity analysis could help to enlarge the genetic diversity of materials in breeding programs and could be used to develop
a core collection. 相似文献
103.
Paul C. Stoy Mathew Williams Mathias Disney Ana Prieto-Blanco Brian Huntley Robert Baxter Philip Lewis 《Landscape Ecology》2009,24(7):971-986
Transferring ecological information across scale often involves spatial aggregation, which alters information content and
may bias estimates if the scaling process is nonlinear. Here, a potential solution, the preservation of the information content
of fine-scale measurements, is highlighted using modeled net ecosystem exchange (NEE) of an Arctic tundra landscape as an
example. The variance of aggregated normalized difference vegetation index (NDVI), measured from an airborne platform, decreased
linearly with log(scale), resulting in a linear relationship between log(scale) and the scale-wise modeled NEE estimate. Preserving
three units of information, the mean, variance and skewness of fine-scale NDVI observations, resulted in upscaled NEE estimates
that deviated less than 4% from the fine-scale estimate. Preserving only the mean and variance resulted in nearly 23% NEE
bias, and preserving only the mean resulted in larger error and a change in sign from CO2 sink to source. Compressing NDVI maps by 70–75% using wavelet thresholding with the Haar and Coiflet basis functions resulted
in 13% NEE bias across the study domain. Applying unique scale-dependent transfer functions between NDVI and leaf area index
(LAI) decreased, but did not remove, bias in modeled flux in a smaller expanse using handheld NDVI observations. Quantifying
the parameters of statistical distributions to preserve ecological information reduces bias when upscaling and makes possible
spatial data assimilation to further reduce errors in estimates of ecological processes across scale. 相似文献
104.
Brian R. Miranda Brian R. Sturtevant Jian Yang Eric J. Gustafson 《Landscape Ecology》2009,24(5):587-598
We demonstrate a method to evaluate the degree to which a meta-model approximates spatial disturbance processes represented
by a more detailed model across a range of landscape conditions, using neutral landscapes and equivalence testing. We illustrate
this approach by comparing burn patterns produced by a relatively simple fire spread algorithm with those generated by a more
detailed fire behavior model from which the simpler algorithm was derived. Equivalence testing allows objective comparisons
of the output of simple and complex models, to determine if the results are significantly similar. Neutral landscape models
represent a range of landscape conditions that the model may encounter, allowing evaluation of the sensitivity and behavior
of the model to different landscape compositions and configurations. We first tested the model for universal applicability,
then narrowed the testing to assess the practical domain of applicability. As a whole, the calibrated simple model passed
the test for significant equivalence using the 25% threshold. When applied to a range of landscape conditions different from
the calibration scenarios, the model failed the tests for equivalence. Although our particular model failed the tests, the
neutral landscape models were helpful in determining an appropriate domain of applicability and in assessing the model sensitivity
to landscape changes. Equivalence testing provides an effective method for model comparison, and coupled with neutral landscapes,
our approach provides an objective way to assess the domain of applicability of a spatial model. 相似文献
105.
Maintaining connectivity among local populations in a fragmented landscape is crucial for the survival of many species. For
isolated habitat patches, stochastic fluctuations and reduced gene flow can lead to high risk of extinction. The connectivity
of the landscape is especially crucial for the carabid species living in the fragmented forests of the Bereg plain (NE Hungary
and W Ukraine) because a highway will be constructed through the plain. Our purpose is to (1) evaluate the impacts of three
possible highway tracks, (2) suggest a solution that is realistic with less impact on connectivity than other plans and (3)
discuss how to decrease the disadvantageous effects of each track. Our results, based on a network analysis of landscape graph
of patches and ecological corridors, indicate that the intended highway could have deleterious consequences on forest-living
carabids. Relatively simple actions, like the establishment of stepping stones, could compensate for the loss of habitat connectivity
and promote the survival of carabids, or minor modifications in one possible track could diminish its adverse effects. While
many other studies would be needed for a comprehensive assessment of the biotic impact of the highway, we provide an example
on the usefulness of network analysis for land use management.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
106.
Habitat specificity indices reflect richness (α) and/or distinctiveness (β) components of diversity. The latter may be defined by α and γ (landscape) diversity in two alternative ways: multiplicatively () and additively (). We demonstrate that the original habitat specificity concept of Wagner and Edwards (Landscape Ecol 16:121–131, 2001) consists of three independent components: core habitat specificity (uniqueness of the species composition), patch area and
patch species richness. We describe habitat specificity as a family of indices that may include either area or richness components,
or none or both, and open for use of different types of mean in calculation of core habitat specificity. Core habitat specificity
is a beta diversity measure: the effective number of completely distinct communities in the landscape. Habitat specificity
weighted by species number is a gamma diversity measure: the effective number of species that a patch contributes to landscape
richness. We compared 12 habitat specificity indices by theoretical reasoning and by use of field data (vascular plant species
in SE Norwegian agricultural landscapes). Habitat specificity indices are strongly influenced by weights for patch area and
patch species richness, and the relative contribution of rare vs. common species (type of mean). The relevance of properties
emphasized by each habitat specificity index for evaluation of patches in a biodiversity context is discussed. Core habitat
specificity is emphasized as an ecologically interpretable measure that specifically addresses patch uniqueness while habitat
specificity weighted by species number combines species richness and species composition in ways relevant for conservation
biological assessment.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
107.
108.
The viability of metapopulations in fragmented landscapes has become a central theme in conservation biology. Landscape fragmentation
is increasingly recognized as a dynamical process: in many situations, the quality of local habitats must be expected to undergo
continual changes. Here we assess the implications of such recurrent local disturbances for the equilibrium density of metapopulations.
Using a spatially explicit lattice model in which the considered metapopulation as well as the underlying landscape pattern
change dynamically, we show that equilibrium metapopulation density is maximized at intermediate frequencies of local landscape
disturbance. On both sides around this maximum, the metapopulation may go extinct. We show how the position and shape of the
intermediate viability maximum is responding to changes in the landscape’s overall habitat quality and the population’s propensity
for local extinction. We interpret our findings in terms of a dual effect of intensified landscape disturbances, which on
the one hand exterminate local populations and on the other hand enhance a metapopulation’s capacity for spreading between
habitat clusters. 相似文献
109.
The question of what determines plant community composition is fundamental to the study of plant community ecology. We examined
the relative roles of historical land use, landscape context, and the biophysical environment as determinants of plant community
composition in regenerating citrus groves in north-central Florida. Results were interpreted in light of plant functional
traits. Herbaceous and woody plants responded differently to broad-scale variables; herbs correlated most strongly with surrounding
land cover at a scale of 8 km, while the only significant determinant of woody species distributions was local land use history.
There were significant correlations between herbaceous species and spatial context, habitat isolation, environmental variables,
and historical variables. Partial Mantel tests indicated that each variable provided a unique contribution in explaining some
of the variation in the herbaceous dataset. The correlation between woody plants and local historical variables remained significant
even with other effects corrected for. In the herbaceous community, species composition was linked to functional traits much
as expected from classical theory. While spatial influences in our study system are important for both woody and herbaceous
plants, the primary determinant of plant community composition in regenerating citrus groves is historical land use. Our results
suggest that the fine-scale mechanisms of local competition, tolerance and facilitation invoked by many classical studies
may ultimately be less important than land use history in understanding current plant community composition in regenerating
agricultural areas. 相似文献
110.
Tradable biodiversity credit systems provide flexible means to resolve conflicts between development and conservation land-use
options for habitats occupied by threatened or endangered species. We describe an approach to incorporate the influence of
habitat fragmentation into the conservation value of tradable credits. Habitat fragmentation decreases gene flow, increases
rates of genetic drift and inbreeding, and increases probabilities of patch extinction. Importantly, tradable credit systems
will change the level of fragmentation over time for small and/or declining populations. We apply landscape equivalency analysis
(LEA), a generalizable, landscape-scale accounting system that assigns conservation value to habitat patches based on patch
contributions to abundance and genetic variance at landscape scales. By evaluating habitat trades using two models that vary
the relationship between dispersal behaviors and landscape patterns, we show that LEA provides a novel method for limiting
access to habitat at the landscape-scale, recognizing that the appropriate amount of migration needed to supplement patch
recruitment and to offset drift and inbreeding will vary as landscape pattern changes over time. We also found that decisions
based on probabilities of persistence alone would ignore changes in migration, genetic drift, and patch extinction that result
from habitat trades. The general principle of LEA is that habitat patches traded should make at least equivalent contributions
to rates of recruitment and migration estimated at a landscape scale. Traditional approaches for assessing the “take” and
“jeopardy” standards under the Endangered Species Act based on changes in abundance and probability of persistence may be
inadequate to prevent trades that increase fragmentation. 相似文献