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91.
LOUIS C. BENDER LAURIE A. LOMAS JASON BROWNING 《The Journal of wildlife management》2007,71(4):1118-1124
Abstract: From December 2001 to December 2004 we monitored 30–44 adult female mule deer (Odocoileus hemionus) annually to assess the factors affecting survival and cause-specific mortality. We found adult female survival of 0.63 (SE = 0.08), 0.90 (SE = 0.05), and 0.91 (SE = 0.04), 2002–2004, respectively. Starvation was the most common cause of mortality, accounting for 11/23 mortalities. Mean ingesta-free body fat (IFBF) levels of adult females in December were low (6–9%), despite few (0–13%) lactating adult females, indicative of extremely nutritionally deficient summer—autumn ranges throughout the study site. A priori levels of IFBF and rump body condition scores (rBCS) were higher in deer that survived the following year regardless of cause of mortality. Logistical analysis indicated that models containing individual body fat, rBCS, mean population body fat, winter precipitation, precipitation during mid- to late gestation, and total annual precipitation were related (x2 ≥ 9.1; P ≤ 0.003) to deer survival, with individual IFBF (β =-0.47 [SE = 0.21]; odds ratio = 0.63 [0.42-0.94]) and population mean IFBF (β = -1.94 [SE = 0.68]; odds ratio = 0.14 [0.04-0.54]) the best predictors; with either variable, probability of dying decreased as fat levels increased. Fawn production was low (2–29 fawns/100 ad F) and, combined with adult survival, resulted in estimated population rates of increase of -35%, -5%, and +6% for 2002–2004, respectively. Deer survival and population performance were limited in north-central New Mexico, USA, due to poor condition of deer, likely a result of limited food resulting from both drought and long-term changes in plant communities. Precipitation during mid- to late gestation was also important for adult female survival in north-central New Mexico. 相似文献
92.
- 1 Two experimental approaches were used to examine the predation risk of six littoral cladoceran and ostracod species to two size classes of the damselfly Lestes sp. Behavioural observations were conducted in a 2–1 arena and predation rate experiments in 1–1 jars in the laboratory.
- 2 Behavioural observations revealed that attack and capture efficiencies by Lestes were higher on smaller cladocerans (Polyphemus and Ceriodaphnia) than on other taxa. Small Lestes had little success ingesting the small ostracod Cypridopsis, whereas larger Lestes captured and ate it easily.
- 3 Predation-rate experiments showed that Lestes has a clear preference for smaller cladocerans over both a large cladoceran (Simocephatus) and all three ostracods (Cypricercus, Cyclocypris, and Cypridopsis). Most Lestes were unable to consume the larger Cypricercus.
- 4 Attack rates and predation rates were highly variable among individual predators.
- 5 These data indicate that damselfly larvae are size selective and consume all but very large cladocerans more readily than ostracods.
93.
Crystal Structure of the C-Terminal Tetrapeptide of Oxytocin 总被引:3,自引:0,他引:3
WE have determined the crystal structure of the protected, C-terminal tetrapeptide of oxytocin S-benzyl-L-cysteinyl-L-prolyl-L-leucyl-glycine amide as well as of its virtually isomorphous seleno-analogue. The crystal structure analyses of these two peptides were undertaken because of our interest in the conformation of the tetrapeptide in isolation as well as when attached to the ring in the complete oxytocin molecule. The seleno-analogue provided an opportunity to compare sulphur and selenium stereochemistry. 相似文献
94.
Microcosms of Danthonia richardsonii (Cashmore) accumulated more carbon when grown under CO2 enrichment (719 μL L–1 cf. 359 μL L–1) over a four-year period, even when nitrogen availability severely restricted productivity (enhancement ratios for total microcosm C accumulation of 1.21, 1.14 and 1.29 for mineral N supplies of 2.2, 6.7 and 19.8 g N m–2 y–1, respectively). The effect of CO2 enrichment on total system carbon content did not diminish with time. Increased carbon accumulation occurred despite the development over time of a lower leaf area index and less carbon in the green leaf fraction at high CO2. The extra carbon accumulated at high CO2 in the soil, senesced leaf and leaf litter fractions at all N levels, and in root at high-N, while at low-and mid-N less carbon accumulated in the root fraction at high CO2. The rate of leaf turnover was increased under CO2 enrichment, as indicated by increases in the carbon mass ratio of senesced to green leaf lamina. Microcosm evapotranspiration rates were lower at high CO2 when water was in abundant supply, resulting in higher average soil water contents. The higher soil water contents at high CO2 have important implications for microcosm function, and may have contributed significantly to the increased carbon accumulation at high CO2. These results indicate that CO2 enrichment can increase carbon accumulation by a simple soil–plant system, and that any increase in whole system carbon accumulation may not be evident from snapshot measurements of live plant carbon. 相似文献
95.
JASON A. ADDISON 《Molecular ecology resources》2007,7(3):389-392
I present a simple approach to overcome the high cost and low efficiency of cloning polymerase chain reaction (PCR) products for individuals in wide‐scale population genetic analyses. The methodology reduces the number of cloning reactions per individual by engineering a suite of genetic markers that differ in size and pooling these PCR products prior to cloning. Alleles from each gene are then recovered by screening transformed bacterial colonies and identifying the inserts corresponding to each gene based on size. I demonstrate the utility of this technique by presenting the results I obtained from cloning four nuclear genes in 118 individuals from three species of sea urchins (Strongylocentrotus purpuratus, S. droebachiensis and S. pallidus). Of the 472 different PCR products I cloned, I recovered at least one allele for 432 of them (91.5%) by screening between 16 and 32 bacterial colonies for each individual. There existed a bias with respect to recovery efficiency: the two largest fragments (1130–800 bp) were recovered 100% of the time, while the two smaller fragments (580–650 bp) were recovered in 85.6% and 81.4% of the experiments, respectively. I discuss the promise of this application for wide‐scale genetic analyses. 相似文献
96.
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98.
A NEW SEA SPIDER (ARTHROPODA: PYCNOGONIDA) WITH A FLAGELLIFORM TELSON FROM THE LOWER DEVONIAN HUNSRÜCK SLATE, GERMANY 总被引:1,自引:1,他引:0
Abstract: A new Lower Devonian sea spider (Arthropoda: Pycnogonida) from the Hunsrück Slate, Germany, is described as Flagellopantopus blocki gen. et sp. nov. This is only the sixth fossil pycnogonid species to be described. Its most remarkable and unique aspect is the long, flagelliform telson. Although our fossil apparently lacks chelifores (an apomorphy), the retained telson and the segmented trunk end behind the last pair of legs resolve F. blocki to a fairly basal position in the pycnogonid stem lineage. It probably lies between Palaeoisopus problematicus Broili, which has a lanceolate telson and the most trunk segments of any sea spider, and all other Silurian–Recent Pycnogonida. Our new material shows that at least two fossil pycnogonids retained a telson, albeit with very different morphologies, and further supports the idea that a greater diversity of body plans existed among the Palaeozoic pycnogonid taxa. 相似文献
99.
RAYNA C. BELL JUAN L. PARRA MARIA TONIONE CONRAD J. HOSKIN JASON B. MACKENZIE STEPHEN E. WILLIAMS CRAIG MORITZ 《Molecular ecology》2010,19(12):2531-2544
Globally, montane tropical diversity is characterized by extraordinary local endemism that is not readily explained by current environmental variables indicating a strong imprint of history. Montane species often exist as isolated populations under current climatic conditions and may have remained isolated throughout recent climatic cycles, leading to substantial genetic and phenotypic divergence. Alternatively, populations may have become contiguous during colder climates resulting in less divergence. Here we compare responses to historical climate fluctuation in a montane specialist skink, Lampropholis robertsi, and its more broadly distributed congener, L. coggeri, both endemic to rainforests of northeast Australia. To do so, we combine spatial modelling of potential distributions under representative palaeoclimates, multi‐locus phylogeography and analyses of phenotypic variation. Spatial modelling of L. robertsi predicts strong isolation among disjunct montane refugia during warm climates, but with potential for localized exchange during the most recent glacial period. In contrast, predicted stable areas are more widespread and connected in L. coggeri. Both species exhibit pronounced phylogeographic structuring for mitochondrial and nuclear genes, attesting to low dispersal and high persistence across multiple isolated regions. This is most prominent in L. robertsi, for which coalescent analyses indicate that most populations persisted in isolation throughout the climate cycles of the Pleistocene. Morphological divergence, principally in body size, is more evident among isolated populations of L. robertsi than L. coggeri. These results highlight the biodiversity value of isolated montane populations and support the general hypothesis that tropical montane regions harbour high levels of narrow‐range taxa because of their resilience to past climate change. 相似文献
100.
JASON G. VOGEL BEN P. BOND-LAMBERTY† EDWARD A. G. SCHUUR STITH T. GOWER† MICHELLE C. MACK KARI E. B. O'CONNELL‡ DAVID W. VALENTINE§ ROGER W. RUESS¶ 《Global Change Biology》2008,14(7):1503-1516
A common hypothesis for northern ecosystems is that low soil temperatures inhibit plant productivity. To address this hypothesis, we reviewed how separate components of ecosystem carbon (C) cycling varied along a soil temperature gradient for nine well-drained, relatively productive boreal black spruce ( Picea mariana Mill. [B.S.P.]) forests in Alaska, USA, and Saskatchewan and Manitoba, Canada. Annual soil temperature [expressed as soil summed degree days (SDD)] was positively correlated with aboveground net primary productivity (ANPP), while negatively correlated with total belowground carbon flux (TBCF). The partitioning of C to ANPP at the expense of root processes represented a nearly 1 : 1 tradeoff across the soil temperature gradient, which implied that the amount of C cycling through these black spruce ecosystems was relatively insensitive to variation in SDD. Moreover, the rate at which C accumulated in the ecosystem since the last stand replacing fire was unrelated to SDD, but SDD was positively correlated to the ratio of spruce-biomass : forest-floor-mass. Thus, plant partitioning of C and the distribution of ecosystem C were apparently affected by soil temperature, although across regions, precipitation co-varied with soil temperature. These two factors likely correlated with one another because of precipitation's influence on soil heat balance, suggesting that a soil temperature–precipitation interaction could be responsible for the shifts in C allocation. Nonetheless, our results highlight that for this boreal ecosystem, ANPP and TBCF can be negatively correlated. In tropical and temperate forests, TBCF and ANPP have been reported as positively correlated, and our results may reflect the unique interactions between soil temperature, forest floor accumulation, rooting depth, and nutrient availability that characterize the black spruce forest type. 相似文献