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151.
Twenty-seven plant taxa previously unreported from Bryce Canyon National Park are listed. 相似文献
152.
Gregory Haenel 《西北部美国博物学家》2011,71(2)
Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; text-indent:.25in; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Clutch size is an important determinant of female reproductive success in reptiles. Although female body size explains much variation in clutch size, other important factors include differences in food availability, predation risk, morphology, and demography. Ornate tree lizards, Urosaurus ornatus, display extensive variation in life history traits, including clutch size. Tree lizards primarily use 2 distinct habitat types—trees and rock surfaces—which influence both the performance and morphology of this species and may affect life history traits such as clutch size. As food availability, microclimate, and, potentially, predator escape probabilities differ between these 2 habitats, I predicted that tree- and rockdwelling lizards would allocate resources toward clutch size differently. Clutch size variation was compared among 15 populations of U. ornatus sampled from the different habitat types. Urosaurus ornatus individuals living on trees had significantly larger clutches than those living on rocks, even after including the effects of body size and environment. Two potential mechanisms leading to larger clutches in tree-dwelling lizards are (1) differences in food availability and (2) differences in performance (sprint vs. endurance) requirements for predator escape in the 2 habitats. Inconsistent distribution of habitat type across the phylogenetic tree indicates either many cases of independent evolution in the allocation strategies of these lizards or a consistent phenotypically plastic response to similar environmental challenges in different populations. El tamaño de puesta es un determinante importante del éxito reproductivo de las hembras. Aunque el tamaño corporal de la hembra explica gran parte de la variación en el tamaño de puesta de los reptiles, otros factores importantes incluyen las diferencias en la disponibilidad de alimento, el riesgo de depredación, la morfología y la demografía. La lagartija arbolera Urosaurus ornatus exhibe gran variación en características de historia de vida, incluyendo el tamaño de puesta. Esta lagartija usa principalmente dos hábitats distintos, árboles y superficies de rocas, los cuales influyen tanto en el desempeño como en la morfología de esta especie y pueden afectar las características de historia de vida como el tamaño de puesta. En vista de que la disponibilidad de alimento, el microclima y posiblemente el escape de los depredadores difieren entre estos dos hábitats, fue posible predecir que las lagartijas que viven en árboles distribuirían sus recursos de una manera diferente a la de las lagartijas que viven en las rocas con respecto al tamaño de puesta. Comparamos la variación en el tamaño de puesta entre 15 poblaciones de U. ornatus provenientes de los dos tipos de hábitat. Las Urosaurus ornatus que viven en los árboles tuvieron puestas considerablemente más grandes que las que viven en las rocas, aun después de incluir los efectos del tamaño corporal y del ambiente. Dos mecanismos que podrían llevar a puestas más grandes en lagartijas que viven en árboles son (1) diferencias en la disponibilidad de alimento, y (2) diferencias en las capacidades necesarias (velocidad/resistencia) para eludir depredadores en los dos hábitats. La distribución del tipo de hábitat en el árbol filogenético indica, o muchos casos de evolución independiente en las estrategias de asignación de recursos de estas lagartijas, o una reacción sistemática y fenotípicamente plástica a presiones ambientales similares en distintas poblaciones. 相似文献
153.
154.
Alushin GM Ramey VH Pasqualato S Ball DA Grigorieff N Musacchio A Nogales E 《Nature》2010,467(7317):805-810
The Ndc80 complex is a key site of regulated kinetochore-microtubule attachment (a process required for cell division), but the molecular mechanism underlying its function remains unknown. Here we present a subnanometre-resolution cryo-electron microscopy reconstruction of the human Ndc80 complex bound to microtubules, sufficient for precise docking of crystal structures of the component proteins. We find that the Ndc80 complex binds the microtubule with a tubulin monomer repeat, recognizing α- and β-tubulin at both intra- and inter-tubulin dimer interfaces in a manner that is sensitive to tubulin conformation. Furthermore, Ndc80 complexes self-associate along protofilaments through interactions mediated by the amino-terminal tail of the NDC80 protein, which is the site of phospho-regulation by Aurora B kinase. The complex's mode of interaction with the microtubule and its oligomerization suggest a mechanism by which Aurora B could regulate the stability of load-bearing kinetochore-microtubule attachments. 相似文献
155.
156.
AP Gregory CA Dendrou KE Attfield A Haghikia DK Xifara F Butter G Poschmann G Kaur L Lambert OA Leach S Prömel D Punwani JH Felce SJ Davis R Gold FC Nielsen RM Siegel M Mann JI Bell G McVean L Fugger 《Nature》2012,488(7412):508-511
Although there has been much success in identifying genetic variants associated with common diseases using genome-wide association studies (GWAS), it has been difficult to demonstrate which variants are causal and what role they have in disease. Moreover, the modest contribution that these variants make to disease risk has raised questions regarding their medical relevance. Here we have investigated a single nucleotide polymorphism (SNP) in the TNFRSF1A gene, that encodes tumour necrosis factor receptor 1 (TNFR1), which was discovered through GWAS to be associated with multiple sclerosis (MS), but not with other autoimmune conditions such as rheumatoid arthritis, psoriasis and Crohn’s disease. By analysing MS GWAS data in conjunction with the 1000 Genomes Project data we provide genetic evidence that strongly implicates this SNP, rs1800693, as the causal variant in the TNFRSF1A region. We further substantiate this through functional studies showing that the MS risk allele directs expression of a novel, soluble form of TNFR1 that can block TNF. Importantly, TNF-blocking drugs can promote onset or exacerbation of MS, but they have proven highly efficacious in the treatment of autoimmune diseases for which there is no association with rs1800693. This indicates that the clinical experience with these drugs parallels the disease association of rs1800693, and that the MS-associated TNFR1 variant mimics the effect of TNF-blocking drugs. Hence, our study demonstrates that clinical practice can be informed by comparing GWAS across common autoimmune diseases and by investigating the functional consequences of the disease-associated genetic variation. 相似文献
157.
The determination of palaeo-elevation has emerged in the past 15 years as an important tool for constraining physical processes that govern the formation of mountain belts. Rowley and Currie report palaeo-elevations for the Lunpola basin within the Tibetan plateau and claim that these elevations are incompatible with 'mantle-thickening models' for mountain formation. We show here that their data do not support this conclusion and, indeed, are consistent with its opposite. The Tibetan plateau could have risen by a kilometre or more as its dense lower lithosphere sank into the underlying mantle. 相似文献
158.
Invasion and the evolution of speed in toads 总被引:1,自引:0,他引:1
Cane toads (Bufo marinus) are large anurans (weighing up to 2 kg) that were introduced to Australia 70 years ago to control insect pests in sugar-cane fields. But the result has been disastrous because the toads are toxic and highly invasive. Here we show that the annual rate of progress of the toad invasion front has increased about fivefold since the toads first arrived; we find that toads with longer legs can not only move faster and are the first to arrive in new areas, but also that those at the front have longer legs than toads in older (long-established) populations. The disaster looks set to turn into an ecological nightmare because of the negative effects invasive species can have on native ecosystems; over many generations, rates of invasion will be accelerated owing to rapid adaptive change in the invader, with continual 'spatial selection' at the expanding front favouring traits that increase the toads' dispersal. 相似文献
159.
160.