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91.
Farjalla VF Srivastava DS Marino NA Azevedo FD Dib V Lopes PM Rosado AS Bozelli RL Esteves FA 《Ecology》2012,93(7):1752-1759
After much debate, there is an emerging consensus that the composition of many ecological communities is determined both by species traits, as proposed by niche theory, as well as by chance events. A critical question for ecology is, therefore, which attributes of species predict the dominance of deterministic or stochastic processes. We outline two hypotheses by which organism size could determine which processes structure ecological communities, and we test these hypotheses by comparing the community structure in bromeliad phytotelmata of three groups of organisms (bacteria, zooplankton, and macroinvertebrates) that encompass a 10 000-fold gradient in body size, but live in the same habitat. Bacteria had no habitat associations, as would be expected from trait-neutral stochastic processes, but still showed exclusion among species pairs, as would be expected from niche-based processes. Macroinvertebrates had strong habitat and species associations, indicating niche-based processes. Zooplankton, with body size between bacteria and macroinvertebrates, showed intermediate habitat associations. We concluded that a key niche process, habitat filtering, strengthened with organism size, possibly because larger organisms are both less plastic in their fundamental niches and more able to be selective in dispersal. These results suggest that the relative importance of deterministic and stochastic processes may be predictable from organism size. 相似文献
92.
Impacts of climate variability and human colonization on the vegetation of the Galápagos Islands 总被引:1,自引:0,他引:1
Restrepo A Colinvaux P Bush M Correa-Metrio A Conroy J Gardener MR Jaramillo P Steinitz-Kannan M Overpeck J 《Ecology》2012,93(8):1853-1866
A high-resolution (2-9 year sampling interval) fossil pollen record from the Galápagos Islands, which spans the last 2690 years, reveals considerable ecosystem stability. Vegetation changes associated with independently derived histories of El Ni?o Southern Oscillation variability provided evidence of shifts in the relative abundance of individual species rather than immigration or extinction. Droughts associated with the Medieval Climate Anomaly induced rapid ecological change that was followed by a reversion to the previous state. The paleoecological data suggested nonneutral responses to climatic forcing in this ecosystem prior to the period of human influence. Human impacts on the islands are evident in the record. A marked decline in long-term codominants of the pollen record, Alternanthera and Acalypha, produced a flora without modern analogue before 1930. Intensified animal husbandry after ca. 1930 may have induced the local extinction of Acalypha and Alternanthera. Reductions in populations of grazing animals in the 1970s and 1980s did not result in the return of the native flora, but in invasions by exotic species. After ca. 1970 the trajectory of habitat change accelerated, continuously moving the ecosystem away from the observed range of variability in the previous 2690 years toward a novel ecosystem. The last 40 years of the record also suggest unprecedented transport of lowland pollen to the uplands, consistent with intensified convection and warmer wet seasons. 相似文献
93.
Dirk Erpenbeck John N. A. Hooper Isabelle Bonnard Patricia Sutcliffe Mayuri Chandra Pierre Perio Carsten Wolff Bernard Banaigs Gert W?rheide Cécile Debitus Sylvain Petek 《Marine Biology》2012,159(5):1119-1127
Sponges of the family Dysideidae (Dictyoceratida) are renowned for their diversity of secondary metabolites, and its genus Lamellodysidea, particularly Lamellodysidea herbacea, is the most studied taxon biochemically. Despite its importance, the taxonomic status of L. herbacea—whether it is a distinct species or a species complex—has never been assessed. Recent biochemical profiling revealed anti-plasmodial activity of brominated compounds in Lamellodysidea of the Pacific. Here, we present a comparative chemotaxonomic and molecular analysis of selected Dysideidae from the Pacific and the Indian Ocean (New Caledonia, Great Barrier Reef, Fiji, Mayotte, Guam, Palau). We investigated the phylogenetic relationships between the populations and assessed their bioactive (PBDE) compounds in order to unravel the taxonomic status of this commercially important group of sponges and assessed patterns of dispersal and biochemical variation. The molecular phylogeny was based on the internal transcribed ribosomal spacer and compared against a PBDE phylogeny for several specimens. Molecular data revealed a diversity of Indo-Pacific L. herbacea populations, also reflected by different PBDE compound profiles. Molecular and biochemical data also revealed a Lamellodysidea species new to science. Several specimens misidentified as Lamellodysidea were detected based on their position on different clades in the molecular phylogeny and their production of different halogenated compounds (brominated vs. chlorinated). The direct comparison of molecular and biochemical data also provided evidence for the occurrence of a host switch event and support for the theory that abiotic factors, such as sedimentation, affect the chemical constituents produced in L. herbacea. 相似文献
94.
Mioko Taguchi Susan J. Chivers Patricia E. Rosel Takashi Matsuishi Syuiti Abe 《Marine Biology》2010,157(7):1489-1498
Genetic structure and phylogeography of the harbour porpoise Phocoena phocoena in the North Pacific were examined using 358 bps sequences from the 5′ end of the mitochondrial DNA control region including
those reported previously and newly obtained from the west Pacific. AMOVA and pairwise population φ
st
estimates clearly revealed genetic differentiation between an east/south and a north/northwest group with the break along
the Pacific Rim at British Columbia. In addition, nested clade phylogeographical analysis, neutrality tests, mismatch distribution
analysis, genetic diversities and Mantel test, suggested that the observed genetic structure might have been influenced by
contiguous range expansion with restricted gene flow in the direction from south to north along the North American coasts
and east to west along the Pacific Rim in the middle to late Pleistocene. 相似文献
95.
Patricia Widener 《Local Environment》2013,18(7):834-851
This article examines the relevance of environmental justice (EJ) and climate change debates as points of articulation and mobilisation among community groups responding to a proposed refinery. It then compares media coverage of the refinery project, a bi-national pipeline and other energy and climate-related news events. The analytical frame joins the EJ paradigm with citizen mobilisation on issues of climate change and energy projects that emit greenhouse gases and that discourage development of renewable sources. Data were collected and analysed from websites, public message boards and media documents. Findings indicate that a community-based anti-refinery campaign combined local EJ struggles with climate activism, while challenging fossil fuel dependencies and calling for renewable regional energy. A climate justice community formed – yet their voices were in their blogs and websites, not in local or national media. 相似文献
96.
97.
To investigate the ability of elasmobranchs to distinguish between differing prey-type electric fields we examined the electroreceptive
foraging behaviour of a model species, Scyliorhinus canicula (small-spotted catshark). Catshark preferences were studied by behaviourally conditioning them to swim through narrow tunnels,
and on exit presenting them simultaneously with two different electric fields. Their subsequent choices of the following paired
options were recorded; (i) Two artificial electric fields (dipole electrodes) with different magnitude direct current (D.C.),
(ii) Two artificial electric fields, one D.C. and the other alternating current (A.C.), of the same magnitude, and (iii) similar
magnitude, natural and artificial D.C. electric fields associated with shore crabs and dipole electrodes respectively. We
found a highly significant preference for the stronger D.C. electric field and a less pronounced, but still significant, preference
for the A.C. electric field rather than the D.C. electric field. No preference was demonstrated between the artificial and
natural D.C. electric fields. The findings are discussed in relation to the animal’s diet and ecology and with regard to anthropogenic
sources of electric fields within their habitat. 相似文献
98.
99.
Schinkel J Warren N Fransman W van Tongeren M McDonnell P Voogd E Cherrie JW Tischer M Kromhout H Tielemans E 《Journal of environmental monitoring : JEM》2011,13(5):1374-1382
The mechanistic model of the Advanced Reach Tool (ART) provides a relative ranking of exposure levels from different scenarios. The objectives of the calibration described in this paper are threefold: to study whether the mechanistic model scores are accurately ranked in relation to exposure measurements; to enable the mechanistic model to estimate actual exposure levels rather than relative scores; and to provide a method of quantifying model uncertainty. Stringent data quality guidelines were applied to the collated data. Linear mixed effects models were used to evaluate the association between relative ART model scores and measurements. A random scenario and company component of variance were introduced to reflect the model uncertainty. Stratified analyses were conducted for different forms of exposure (abrasive dust, dust, vapours and mists). In total more than 2000 good quality measurements were available for the calibration of the mechanistic model. The calibration showed that after calibration the mechanistic model of ART was able to estimate geometric mean (GM) exposure levels with 90% confidence for a given scenario to lie within a factor between two and six of the measured GM depending upon the form of exposure. 相似文献
100.
Recent literature suggests that a “shared politics of place” attained through joint activities fosters social integration and provides people with a means to practise co-operation [Baumann, G., 1996. Contesting culture: discourses of identity in multi-ethnic London. Cambridge: Cambridge University Press; Sanjek, R., 1998. The future of us all: race & neighbourhood policies in New York City. Ithaca, NY: Cornell University Press; Sennett, R., 2012. Together: the rituals, pleasures and politics of cooperation. UK: Penguin]. Such a “shared politics of place” is most likely to occur in the context of public space conceptualised broadly as “the setting for everyday spatial behaviour of individuals and communities, emphasizing ordinary activities of citizens” [Lownsbrough, H. and Beunderman, J., 2007. Equally spaced? Public space and interaction between diverse communities. London: Demos, p. 8]. Here we explore one element of such public space – urban agriculture sites – with a view to identifying the extent to which a “shared politics of place” can be created and nurtured among the cultivating citizenry. The paper draws on data collected on allotment gardening sites in two urban contexts: Dublin (Ireland) and Belfast (Northern Ireland) over the period 2009–2013. We demonstrate the centrality of allotment cultivation to the generation of solidarity, mutuality and trust among participating citizens. Individuals engaging in allotment gardening in both Dublin and Belfast create and sustain civil interfaces – dismantling barriers, exchanging knowledge, challenging stereotypes, generating empathy and getting on with the business of simply getting on with their lives. The modus operandi of allotment gardening is predicated on a willingness to disregard social and ethno-national categorisations while on site. This is not to deny that such differences exist and persist, but allotments offer a “space of potential” where those differences are, at least for a time, rendered less salient. 相似文献