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821.
Above-ground biomass biomass of Molinia caerulea from 36 sites throughout Britain was analysed for concentrations of elements (N, P, K, Ca, Mg, Fe, Mn, Cu, Zn and Na), with matching analyses of soil nutrients, together with pH and LOI. Between-year and seasonal variation in the nutrients was also studied at one of the sites. the grass was found on acid sites ranging between pH 3.1 and 5.8. the soil humus content varied widely, and there were significant correlations between that and elements (N, P, K, Ca, Mg and Na) in the soil. Concentrations of calcium, magnesium, zinc and manganese in the plant material were significantly correlated with extractable levels in the soils. Between year variation in the plant nutrient concentrations at one site was of a similar order to variation between the sites. Generally there was less variation in nitrogen, phosphorus and potassium tissue levels than in calcium, magnesium, zinc and copper. Iron and sodium were the most variable. Tissue concentrations of nitrogen, phosphorus, potassium and copper declined throughout the growing season, whereas magnesium, calcium and iron built up until August/September after which a decline set in as the leaves senesced. the results are discussed in relation to the importance of standardizing the time of sampling, in comparison with concentrations of tissue levels in other plants and the growth strategy of this deciduous grass. 相似文献
822.
D.?R.?FeinbergEmail author L.?M.?DeBruine B.?C.?Jones A.?C.?Little J.?J.?M.?O’Connor C.?C.?Tigue 《Behavioral ecology and sociobiology》2012,66(3):413-418
Research has revealed that women’s self-perceived attractiveness positively predicts preferences for male facial and vocal
masculinity, particularly in the context of long-term relationships. Other research has demonstrated that women who perceive
themselves to be less healthy prefer male masculinity more than do women who may be healthier. As self-perceived health may
predict self-perceived attractiveness, previous findings may appear to be contradictory. Therefore, we compared the effects
of self-perceived attractiveness and self-perceived health on vocal masculinity preferences in long- and short-term relationship
contexts. We found that although self-perceived health and attractiveness were positively correlated, self-rated attractiveness
positively predicted long-term vocal masculinity preferences, whereas self-rated health negatively predicted short-term vocal
masculinity preferences. While health and attractiveness may share a common basis, here we show independent potentially adaptive
relationships with preferences based on relationship context. Such preferences are potentially adaptive as (a) masculine men
may pass on inheritable immunity to infection to their offspring, which may be a relatively greater benefit for women in poor
health; and (b) masculine men may be more likely to invest in relationships and offspring of relatively attractive women,
decreasing the cost of choosing a masculine long-term partner for attractive women. These data resolve a potential conflict
between health and attractiveness influences on the attractiveness of masculinity and highlight sophisticated individual differences
in preferences. 相似文献
823.
Kathryn B. McNamara Julia L. McKenzie Mark A. Elgar Therésa M. Jones 《Behavioral ecology and sociobiology》2012,66(8):1141-1147
Male mating status can affect female reproductive output if male ejaculate investment declines over consecutive matings. Accordingly, females are predicted to mate preferentially with virgin males. In mildly polyandrous lepidopterans, female fitness is less affected by reduced male investment than in more polyandrous species, and so the predictions for female mating preferences are less clear. We examined female mating preferences in the mildly polyandrous almond moth, Cadra cautella, in which ejaculate size does not affect female reproductive output. First, we allowed females to mate with virgin or once-mated males, in which the males were presented individually or simultaneously. We recorded the latency to mating and, in the case of the simultaneously presented trials, the identity of the successful, copulating male. We found that females mated more frequently with mated males (when simultaneously presented with both males), yet females did not differ in the time taken to initiate copulation with any male. We further examined if this mated male advantage was due to differential mate detection or locomotory behaviour of the male treatments. We tested the ability of virgin and mated males to locate a receptive female within a wind tunnel using long-distance pheromone cues and recorded their activity budget. We found no difference in the ability of mated or virgin males to locate or approach a receptive female, or in their activity levels. These data suggest a female preference for mated males in this species, a preference that may minimise other potential costs of mating. 相似文献
824.
Human-caused changes in disturbance regimes and introductions of nonnative species have the potential to result in widespread, directional changes in forest community structure. The degree that plant community composition persists or changes following disturbances depends on the balance between local extirpation and colonization by new species, including nonnatives. In this study, we examined species losses and gains, and entry of native vs. exotic species to determine how oak forests in the Appalachian Mountains might shift in species composition following a gradient of pulse disturbances (timber harvesting). We asked (1) how compositional stability of the plant community (resistance and resilience) was influenced by disturbance intensity, (2) whether community responses were driven by extirpation or colonization of species, and (3) how disturbance intensity influenced total and functional group diversity, including the nonnative proportion of the flora through time. We collected data at three spatial scales and three times, including just before, one year post-disturbance, and 10 years post-disturbance. Resistance was estimated using community distance measures between pre- and one year post-disturbance, and resilience using community distance between pre- and 10-year post-disturbance conditions. The number of colonizing and extirpated species between sampling times was analyzed for all species combined and for six functional groups. Resistance and resilience decreased with increasing timber-harvesting disturbance; compositional stability was lower in the most disturbed plots, which was driven by colonization, but not extirpation, of species. Colonization of species also led to increases in diversity after disturbance that was typically maintained after 10 years following disturbance. Most of the community-level responses were driven by post-disturbance colonization of native forbs and graminoids. The nonnative proportion of plant species tended to increase following disturbance, especially at large spatial scales in the most disturbed treatments, but tended to decrease through time following disturbance due to canopy development. The results of this study are consistent with the theory that resources released by disturbance have strong influences on species colonization and community composition. The effects of management activities tested in this study, which span a gradient of timber-harvesting disturbance, shift species composition largely via an increase in species colonization and diversity. 相似文献
825.
Charlyn Partridge Ingrid Ahnesjö Charlotta Kvarnemo Kenyon B. Mobley Anders Berglund Adam G. Jones 《Behavioral ecology and sociobiology》2009,63(3):345-354
The last several decades of research in behavioral ecology have resulted in a deeper appreciation of post-mating processes
and sexual conflict in sexual selection. One of the most controversial aspects of sexual selection is cryptic mate choice.
Here, we take advantage of male pregnancy in a sex-role-reversed pipefish (Syngnathus typhle) to quantify cryptic choice based on perceived parasite load and other sources of variance in female fitness. Studies have
shown that S. typhle males preferentially mate with females with lower parasite loads and that a male’s perception of female parasite load can
be altered by tattooing females. We manipulated the apparent parasite load of females in controlled mating experiments to
test the hypothesis that post-copulatory sexual selection is dependent on a male’s perception of female parasite load in pipefish.
Our results provided no evidence for cryptic male choice based on perceived female parasite load. However, we found evidence
that eggs from larger females were more likely to result in viable offspring than eggs from smaller females and that the first
female to mate with a male transferred more eggs per copulation on average. Overall, our results show that potential for post-copulatory
sexual selection does exist in pipefish, but the male’s perception of female parasite load does not play a major role in this
process. 相似文献
826.
Ann E. Krause Ken A. Frank Michael L. Jones Thomas F. Nalepa Richard P. Barbiero Charles P. Madenjian Megan Agy Marlene S. Evans William W. Taylor Doran M. Mason Nancy J. Leonard 《Ecological modelling》2009,220(22):3147
Two issues in ecological network theory are: (1) how to construct an ecological network model and (2) how do entire networks (as opposed to individual species) adapt to changing conditions? We present a novel method for constructing an ecological network model for the food web of southeastern Lake Michigan (USA) and we identify changes in key system properties that are large relative to their uncertainty as this ecological network adapts from one time point to a second time point in response to multiple perturbations. To construct our food web for southeastern Lake Michigan, we followed the list of seven recommendations outlined in Cohen et al. [Cohen, J.E., et al., 1993. Improving food webs. Ecology 74, 252–258] for improving food webs. We explored two inter-related extensions of hierarchical system theory with our food web; the first one was that subsystems react to perturbations independently in the short-term and the second one was that a system's properties change at a slower rate than its subsystems’ properties. We used Shannon's equations to provide quantitative versions of the basic food web properties: number of prey, number of predators, number of feeding links, and connectance (or density). We then compared these properties between the two time-periods by developing distributions of each property for each time period that took uncertainty about the property into account. We compared these distributions, and concluded that non-overlapping distributions indicated changes in these properties that were large relative to their uncertainty. Two subsystems were identified within our food web system structure (p < 0.001). One subsystem had more non-overlapping distributions in food web properties between Time 1 and Time 2 than the other subsystem. The overall system had all overlapping distributions in food web properties between Time 1 and Time 2. These results supported both extensions of hierarchical systems theory. Interestingly, the subsystem with more non-overlapping distributions in food web properties was the subsystem that contained primarily benthic taxa, contrary to expectations that the identified major perturbations (lower phosphorous inputs and invasive species) would more greatly affect the subsystem containing primarily pelagic taxa. Future food-web research should employ rigorous statistical analysis and incorporate uncertainty in food web properties for a better understanding of how ecological networks adapt. 相似文献
827.
Xubin PAN Jingyi ZHANG Wei-Ta FANG Kim D. JONES 《Frontiers of Environmental Science & Engineering》2012,6(6):825-830
To control water impairment in urban stormwater, it is important to evaluate changing patterns of water quality parameters in stormwater runoff. Thus, the authors performed a series of experiments to investigate the dynamics of common water parameters during storm events in semi-arid areas, with multiple samples collected and analyzed in field stormwater applications. At this field monitoring site within McAuliffe Park, McAllen, Texas, in the United States, a storm event increased the concentrations of Escherichia coli (E. coli), but this event represented a decreasing trend over the entire event period. Besides, peak intensity of different pollutants in the stormwater runoff occurred at different times other than at any peak flows, representing a complexity of the temporal and spatial measurements. Multi-sample perevent approaches recommended based on the complexity of the hydrograph and different peak intensity times of pollutants. In addition, high bacteria and total suspended solids (TSS) concentrations in the initial stage of the storm event should be considered when designing Best Management Practices (BMPs) and Low Impact Developments (LIDs). New strategies and solutions for addressing ecohydrological challenges should be proposed to avoid collateral damages to their both common wealth in ecosystems and human well-beings. 相似文献
828.
Ranches are being converted to exurban housing developments in the southwestern United States, with potentially significant but little-studied impacts on biological diversity. We counted birds in grasslands and savannas in southeastern Arizona that were grazed by livestock, embedded in low-density exurban housing developments, or both, or neither. Species richness and bird abundance were higher in exurban neighborhoods than in undeveloped landscapes, independent of livestock grazing. The positive response to development was particularly evident among doves, quail, hummingbirds, aerial insectivores, and some but not all ground-foraging sparrows. Effects of livestock grazing were comparatively minor and mostly involved birds with requirements for tall ground cover or the lack of it. The average rank correlation between counts of individual species and housing density was positive across all transects. However, this relationship disappeared among the exurban transects alone, and bird species richness on the exurban transects was negatively correlated with the number of homes nearby. These results suggest that the positive influence of exurban development on avian abundance and variety was greatest at the lowest housing densities. We attribute the attraction of many birds to exurban development to an oasis effect, in which resources otherwise scarce in arid southwestern environments (shade, nectar, nest sites, and especially water) are relatively abundant around exurban home sites. This finding is consistent with the hypothesis that exurban home sites represented resource supply points inside birds' home ranges otherwise consisting mostly of natural vegetation. 相似文献
829.
Vyverman W Verleyen E Sabbe K Vanhoutte K Sterken M Hodgson DA Mann DG Juggins S Van de Vijver B Jones V Flower R Roberts D Chepurnov VA Kilroy C Vanormelingen P De Wever A 《Ecology》2007,88(8):1924-1931
There is a long-standing belief that microbial organisms have unlimited dispersal capabilities, are therefore ubiquitous, and show weak or absent latitudinal diversity gradients. In contrast, using a global freshwater diatom data set, we show that latitudinal gradients in local and regional genus richness are present and highly asymmetric between both hemispheres. Patterns in regional richness are explained by the degree of isolation of lake districts, while the number of locally coexisting diatom genera is highly constrained by the size of the regional diatom pool, habitat availability, and the connectivity between habitats within lake districts. At regional to global scales, historical factors explain significantly more of the observed geographic patterns in genus richness than do contemporary environmental conditions. Together, these results stress the importance of dispersal and migration in structuring diatom communities at regional to global scales. Our results are consistent with predictions from the theory of island biogeography and metacommunity concepts and likely underlie the strong provinciality and endemism observed in the relatively isolated diatom floras in the Southern Hemisphere. 相似文献
830.
Toal ME Copplestone D Johnson MS Jackson D Jones SR 《Journal of environmental radioactivity》2002,63(1):85-103
Radiocaesium (137Cs) activity concentrations and aggregated transfer factors (Tag values) were calculated for vascular plants, fungal fruiting bodies and invertebrates in a semi-natural Picea sitchensis woodland (Lady Wood) adjacent to the British Nuclear Fuels plc. reprocessing facility at Sellafield, Cumbria, UK. The Tag values for vascular plants ranged from 7.1 x 10(-4) - 1.9 x 10(-2) m2 kg(-1), the maximum value being for Pteridium aquilinum. Fungal fruiting bodies had higher Tag values (1.9 x 10(-3) - 1.8 x 10(-1) m2 kg(-1)) than vascular plants, with a maximum value for Mycena galericulata. None of the activity concentrations for edible foodstuffs collected within this study (fungi and berries) exceeded the EC recommended limits of 137Cs in foodstuffs grown within the UK. The invertebrate community sampled during the study had Tag values ranging from 3.4 x 10(-4) to 1.3 x 10(-2) m2 kg(-1). There were no systematic differences in 137Cs activity concentration between invertebrate guilds, or between seasonal cohorts within guilds. The invertebrates in Lady Wood were exposed to a dose from 137Cs (internal gamma + beta and external gamma) ranging between 4.37 x 10(-4) and 6.40 x 10(-4) mGy day(-1). Including dose from radionuclides other than 137Cs and accounting for uncertainties due to the relative biological effectiveness of differing radionuclides could increase total dose by approximately an order of magnitude. These dose rates are at least three orders of magnitude lower than the 1 mGy d(-1) level at which harm may be caused to terrestrial biota, hence the risk to the invertebrate community from the effects of ionising radiation in Lady Wood is low. 相似文献