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71.
Insectivorous fishes were sampled from March, 1983 to February 1984, in Flint Creek, Delaware Co., Oklahoma. There was insignificant habitat segregation between Etheostoma spectabile and E. punctulatum and seasonal habitat partitioning between Cottus carolinae and both darters. Mature E. spectabile ate primarily chironomids and mayflies, whereas juveniles fed primarily on microcrustaceans. Mature E. punctulatum consumed fewer Ephemerella and Leptophlebia than E. spectabile , feeding on Stenonema and other crustaceans. Juvenile E. punctulatum fed mainly on amphipods and mayflies, and juvenile E. spectabile ate primarily microcrustaceans. Cottus carolinae elected primarily mayflies in spring - summer and chironomids in January - February. Coefficients of dietary overlap were highest between larger E. spectabile and juvenile E. punctulatum and lowest between immature E. spectabile and mature E. punctulatum . Overlap between the two darters was significantly correlated with differences in mean prey size (p E. spectabile was also significantly correlated to differences in mean prey sizes. Etheostoma spectabile generally preferred smaller prey than E. punctulatum . All three species avoided Stenelmis . Cottus carolinae avoided microcrustaceans. The study showed that resource partitioning among these three insectivorous fishes is affected by complex interactions of habitat and prey electivity, and prey size selectivity. 相似文献
72.
Nymphs and adults of three new species of Isoperla are described from reared material. I. sagittata is known only from southeastern Texas, I. Coushatta has been collected in East Texas and Oklahoma, and I. jewetti occurs in the Basin and Range Mountains of West Texas. The male aedeagii, female subgenital plates, and nymphal mouthparts are diagnostic in all three species. 相似文献
73.
Sònia Garcia Teresa Garnatje E. Durant McArthur Jaume Pellicer Stewart C. Sanderson Joan Vallès 《西北部美国博物学家》2011,71(2)
A recent molecular phylogenetic study of all members of Artemisia subgenus Tridentatae, as well as most of the other New World endemic Artemisia and the allied genera Sphaeromeria and Picrothamnus, raised the necessity of revising the taxonomic framework of the North American endemic Artemisia. Composition of the subgenus Tridentatae is enlarged to accommodate other North American endemics and is organized into 3 sections: Tridentatae, Nebulosae, and Filifoliae. This paper deals with the combination of one section, the amendment of 2 more sections, and the combination in or the reversion to Artemisia of some Sphaeromeria and Picrothamnus species. The new names given for previous Sphaeromeria species are Artemisia macarthurii (for S. argentea ), A. albicans (for S. cana ), A. constricta (for S. compacta ), and A. inaequifolia (for S. diversifolia ). The other Sphaeromeria we studied ( S. capitata, S. potentilloides, S. ruthiae, and S. simplex ) had been formerly considered Artemisia (respectively, A. capitata, A. potentilloides, A. ruthiae, and A. simplex ), and their previous nomenclature is therefore recommended. Un estudio reciente sobre la filogenia molecular de todos los miembros del subgénero Tridentatae de Artemisia, así como de la mayoría de las otras especies de Artemisia endémicas del Nuevo Mundo y los géneros afines Sphaeromeria y Picrothamnus, hizo ver la necesidad de revisar el marco taxonómico de las especies de Artemisia endémicas a Norteamérica. La composición del subgénero Tridentatae se ha ampliado para dar cabida a las otras especies endémicas de Norteamérica, y está organizado en 3 secciones: Tridentatae, Nebulosae y Filifoliae. El presente artículo trata sobre la combinación de una sección y la enmienda de 2 más, y propone la incorporación o reversión a Artemisia de algunas especies de Sphaeromeria y Picrothamnus. Los nuevos nombres de las especies previamente asignadas a Sphaeromeria son Artemisia macarthurii (para S. argentea ), A. albicans (para S. cana ), A. constricta (para S. compacta ) y A. inaequifolia (para S. diversifolia ). Las otras especies de Sphaeromeria estudiadas ( S. capitata, S. potentilloides, S. ruthiae y S. simplex ) habían sido previamente consideradas como miembros de Artemisia ( A. capitata, A. potentilloides, A. ruthiae y A. simplex, respectivamente), por lo quese recomienda utilizar su nomenclatura anterior. 相似文献
74.
E. Durant McArthur Joann Mudge Renée Van Buren W. Ralph Andersen Stewart C. Sanderson David G. Babbel 《西北部美国博物学家》2011,58(1)
Species of Artemisia (subgenus Tridentatae ) dominate much of western North America. The genetic variation that allows this broad ecological adaptation is facilitated by hybridization and polyploidization. Three separate studies were performed in this group using randomly amplified polymorphic DNA (RAPD). Fifty-seven 10-mer primers generated nearly 400 markers from genomic DNA obtained from leaf tissue. These studies were (1) a measure of the variability of plants within and between populations and between subspecies using 5 A. tridentata ssp. wyomingensis populations, 2 A. cana ssp. cana populations, and 1 A. cana ssp. viscidula population; (2) an examination of the hypothesis that tetraploid (4 x ) Artemisia tridentata spp. vaseyana derives de novo from diploid (2 x ) populations via antopolyploidy; and (3) an examination of the validity of the status of putative hybrids that have been produced by controlled pollination. These later hybrid combinations- A. tridentata ssp. tridentata × A. t. ssp. vaseyana , A. t. ssp. wyomingensis × A. tripartita , and A. cana ssp. cana A. tridentata ssp. wyomingensis - were made to combine traits of parental taxa in unique combinations with possible management application. RAPD marker data were subjected to similarity and UPGMA clustering analyses. RAPD markers were effective in measuring genetic diversity at different systematic levels. Individual plants within a population were approximately 55% to > 80% similar to one another; populations within subspecies gave corresponding values of similarity, probably a result of the combined effects of large population sizes and wind pollination. The 2 subspecies of A. cana were approximately 45% similar. At least some 4 x populations of A. tridentata ssp. vaseyana apparently derive de novo from 2 x plants based on their being embedded in 2 x phenogram groups, thus reinforcing evidence that autopolyploidy plays an important role in Tridentatae population biology. Two ( A. tridentata ssp. tridentata × A. t. ssp. vaseyana and A. cana ssp. cana × A. tridentata ssp. wyomingensis ) of the 3 putative hybrid combinations were confirmed to include hybrids. These hybrids may have potential in management applications. Additional use of RAPD technology combined with other techniques may be useful in delimiting genetic characteristics and in guiding artificial selection in Tridentatae . 相似文献
75.
76.
A decomposition of the Brier skill score shows that the performance of judgmental forecasts depends on seven components: environmental predictability, fidelity of the information system, match between environment and forecaster, reliability of information acquisition, reliability of information processing, conditional bias, and unconditional bias. These components provide a framework for research on the forecasting process. Selected literature addressing each component is reviewed, and implications for improving judgmental forecasting are discussed. 相似文献
77.
During mitosis, adherent animal cells undergo a drastic shape change, from essentially flat to round. Mitotic cell rounding is thought to facilitate organization within the mitotic cell and be necessary for the geometric requirements of division. However, the forces that drive this shape change remain poorly understood in the presence of external impediments, such as a tissue environment. Here we use cantilevers to track cell rounding force and volume. We show that cells have an outward rounding force, which increases as cells enter mitosis. We find that this mitotic rounding force depends both on the actomyosin cytoskeleton and the cells' ability to regulate osmolarity. The rounding force itself is generated by an osmotic pressure. However, the actomyosin cortex is required to maintain this rounding force against external impediments. Instantaneous disruption of the actomyosin cortex leads to volume increase, and stimulation of actomyosin contraction leads to volume decrease. These results show that in cells, osmotic pressure is balanced by inwardly directed actomyosin cortex contraction. Thus, by locally modulating actomyosin-cortex-dependent surface tension and globally regulating osmotic pressure, cells can control their volume, shape and mechanical properties. 相似文献
78.
Mills RE Walter K Stewart C Handsaker RE Chen K Alkan C Abyzov A Yoon SC Ye K Cheetham RK Chinwalla A Conrad DF Fu Y Grubert F Hajirasouliha I Hormozdiari F Iakoucheva LM Iqbal Z Kang S Kidd JM Konkel MK Korn J Khurana E Kural D Lam HY Leng J Li R Li Y Lin CY Luo R Mu XJ Nemesh J Peckham HE Rausch T Scally A Shi X Stromberg MP Stütz AM Urban AE Walker JA Wu J Zhang Y Zhang ZD Batzer MA Ding L Marth GT McVean G Sebat J Snyder M Wang J Ye K Eichler EE Gerstein MB Hurles ME Lee C McCarroll SA 《Nature》2011,470(7332):59-65
Genomic structural variants (SVs) are abundant in humans, differing from other forms of variation in extent, origin and functional impact. Despite progress in SV characterization, the nucleotide resolution architecture of most SVs remains unknown. We constructed a map of unbalanced SVs (that is, copy number variants) based on whole genome DNA sequencing data from 185 human genomes, integrating evidence from complementary SV discovery approaches with extensive experimental validations. Our map encompassed 22,025 deletions and 6,000 additional SVs, including insertions and tandem duplications. Most SVs (53%) were mapped to nucleotide resolution, which facilitated analysing their origin and functional impact. We examined numerous whole and partial gene deletions with a genotyping approach and observed a depletion of gene disruptions amongst high frequency deletions. Furthermore, we observed differences in the size spectra of SVs originating from distinct formation mechanisms, and constructed a map of SV hotspots formed by common mechanisms. Our analytical framework and SV map serves as a resource for sequencing-based association studies. 相似文献
79.
John E. Stewart 《Foundations of Science》2012,17(1):47-50
Vidal’s (Found Sci, 2010) and Rottiers’s (Found Sci, 2010) commentaries on my (2010) paper raised a number of important issues about the possible future trajectory of evolution and
its implications for humanity. My response emphasizes that despite the inherent uncertainty involved in extrapolating the
trajectory of evolution into the far future, the possibilities it reveals nonetheless have significant strategic implications
for what we do with our lives here and now, individually and collectively. One important implication is the replacement of
postmodern scepticism and relativism with an evolutionary grand narrative that can guide humanity to participate successfully
in the future evolution of life in the universe. 相似文献
80.
The Meaning of Life in a Developing Universe 总被引:4,自引:4,他引:0
John E. Stewart 《Foundations of Science》2010,15(4):395-409
The evolution of life on Earth has produced an organism that is beginning to model and understand its own evolution and the
possible future evolution of life in the universe. These models and associated evidence show that evolution on Earth has a
trajectory. The scale over which living processes are organized cooperatively has increased progressively, as has its evolvability.
Recent theoretical advances raise the possibility that this trajectory is itself part of a wider developmental process. According
to these theories, the developmental process has been shaped by a yet larger evolutionary dynamic that involves the reproduction
of universes. This evolutionary dynamic has tuned the key parameters of the universe to increase the likelihood that life
will emerge and produce outcomes that are successful in the larger process (e.g. a key outcome may be to produce life and
intelligence that intentionally reproduces the universe and tunes the parameters of ‘offspring’ universes). Theory suggests
that when life emerges on a planet, it moves along this trajectory of its own accord. However, at a particular point evolution
will continue to advance only if organisms emerge that decide to advance the developmental process intentionally. The organisms
must be prepared to make this commitment even though the ultimate nature and destination of the process is uncertain, and
may forever remain unknown. Organisms that complete this transition to intentional evolution will drive the further development
of life and intelligence in the universe. Humanity’s increasing understanding of the evolution of life in the universe is
rapidly bringing it to the threshold of this major evolutionary transition. 相似文献