166,161 research outputs found
Less is more: rarity trumps quality in luxury markets
No full textThe international market for luxury goods has almost doubled since 1990, with a worldwide increase of 10% annually. This trade is fuelled by a great deal of legally and illegally exploited wildlife species, putting enormous pressure on many of them, with potentially irreversible consequences. The dramatic decline of sturgeon populations exploited for their caviar, is a good example: all 27 species are threatened and the most coveted are on the verge of extinction. We aim to identify the mechanism responsible for the continued overexploitation of sturgeon species, despite caviar's ever-increasing price and the imminent loss of these species. Here, we demonstrate consumer preference for rarity over intrinsic quality: customers tasting two caviar samples more often chose the one they thought was rare, although both were identical. In a game theory model, we demonstrate that the most rational behaviour is to rush to consume rare species, even though this precipitates their extinction. We conclude that the human predisposition to place exaggerated value on rarity probably drives the entire market for luxury goods from reptile skins to exotic woods. Our findings suggest that allowing low levels of legal trade will exacerbate the arbitrary value of rare species and thereby stimulate demand. Only a total ban on trade from the wild (with very strict controls) combined with strong support for farmed equivalents will protect rare species
Local and regional rarity in a diverse tropical fish assemblage
No full textBecause most species in an ecological assemblage are rare, much of the species richness we value is due to taxa with few individuals or a restricted distribution. It has been apparent since the time of ecological pioneers such as Bates and Darwin that tropical systems have disproportionately large numbers of rare species, yet the distribution and abundance patterns of these species remain largely unknown. Here, we examine the diversity of freshwater fish in a series of lakes in the Amazonian várzea, and relate relative abundance, both as numbers of individuals and as biomass, to the occurrence of species in space and time. We find a bimodal relationship of occurrence that distinguishes temporally and spatially persistent species from those that are infrequent in both space and time. Logistic regression reveals that information on occurrence helps distinguish those species that are rare in this locality but abundant elsewhere, from those that are rare throughout the region. These results form a link between different approaches used to evaluate commonness and rarity. In doing so, they provide a tool for identifying species of high conservation priority in poorly documented but species rich localities.Peer reviewe
How do biodiversity patterns of river animals emerge from the distributions of common and rare species?
No full textWe studied the patterns of commonness and rarity for one vertebrate (fish) and four freshwater insect taxa (Ephemeroptera, Plecoptera, Trichoptera and Coleoptera) in southwestern France (57,000 km²), and we analysed the relationships between the location of sites and the contribution of commonness and rarity to species richness within a large stream system. Richness patterns in fish and aquatic insects were related to the location of sites within the stream system. The number of common and rare fish species increased from up- to downstream areas as a result of downstream additions of species. The number of common insect species peaked in the intermediate section of the river continuum, whereas rarity increased with decreasing elevation. In all taxa, common species gave a closer approximation to overall patterns of species richness than did rare ones. The biodiversity patterns of river animals emerged from convergence in the distributions of common and rare species (fish), or mostly from the distribution of common species (insects). However, in fish, Ephemeroptera and Plecoptera, the rarer species became almost equally, or more strongly correlated with overall species richness when increasing information along the common-to-rare and rare-to-common sequences. These patterns suggested that rarer species show a similar or stronger affinity, on a species-for-species basis, for high richness areas than do the commoner species. These schemes have implications for biodiversity assessments, as studies using common species richness to target important areas for monitoring or conservation efforts within stream systems will not necessarily identify areas important for rare species, and vice versa
Poissonian twin-beam states and the effect of symmetrical photon subtraction in loss estimations
No full textWe have devised an experimentally realizable model generating twin-beam states whose individual beam photon statistics are varied from thermal to Poissonian (by temporal mode averaging) keeping the nonclassical mode correlation intact. We have studied the usefulness of these states for loss measurement by considering three different estimators, comparing with the correlated thermal twin-beam states generated from spontaneous parametric down conversion or four-wave mixing. We then incorporated the photon subtraction operation into the model and demonstrated their performance in loss estimations with respect to unsubtracted states at both fixed squeezing and per photon exposure of the absorbing sample. For instance, at fixed squeezing, for two photon subtraction, up to three times advantage is found. An unexpected result in the latter case is that in some operating regimes the photon subtraction scheme can also give up to 20% advantage over the correlated thermal beam result and no advantages are obtained when the statistics of each beam turns to Poissonian. We have also made a comparative study of these estimators for finding the best measurement for loss estimations. We present results for all the values of the model parameters changing the statistics of twin-beam states from thermal t
[Report to Chief J. E. Curry, by an unknown author #1]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
[Report to Chief J. E. Curry, by an unknown author #2]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
Rarity, trophy hunting and ungulates
No full textThe size and shape of a trophy constitute major determinants of its value. We postulate that the rarity of a species, whatever its causes, also plays a major role in determining its value among hunters. We investigated a role for an Anthropogenic Allee effect in trophy hunting, where human attraction to rarity could lead to an over-exploitative chain reaction that could eventually drive the targeted species to extinction. We performed an inter-specific analysis of trophy prices of 202 ungulate taxa and quantified to what extent morphological characteristics and their rarity accounted for the observed variation in their price. We found that once location and body mass were accounted for, trophies of rare species attain higher prices than those of more common species. By driving trophy price increase, this rarity effect may encourage the exploitation of rare species regardless of their availability, with potentially profound consequences for populations
Temporal rarity is a better predictor of local extinction risk than spatial rarity
No full textSpatial rarity is often used to predict extinction risk, but rarity can also occur temporally. Perhaps more relevant in the context of global change is whether a species is core to a community (persistent) or transient (intermittently present), with transient species often susceptible to human activities that reduce niche space. Using 5–12 yr of data on 1,447 plant species from 49 grasslands on five continents, we show that local abundance and species persistence under ambient conditions are both effective predictors of local extinction risk following experimental exclusion of grazers or addition of nutrients; persistence was a more powerful predictor than local abundance. While perturbations increased the risk of exclusion for low persistence and abundance species, transient but abundant species were also highly likely to be excluded from a perturbed plot relative to ambient conditions. Moreover, low persistence and low abundance species that were not excluded from perturbed plots tended to have a modest increase in abundance following perturbance. Last, even core species with high abundances had large decreases in persistence and increased losses in perturbed plots, threatening the long-term stability of these grasslands. Our results demonstrate that expanding the concept of rarity to include temporal dynamics, in addition to local abundance, more effectively predicts extinction risk in response to environmental change than either rarity axis predicts alone.This article is published as Wilfahrt, P. A., A. L. Asmus, E. W. Seabloom, J. A. Henning, P. Adler, C. A. Arnillas, J. D. Bakker, L. Biederman, L. A. Brudvig, M. Cadotte, P. Daleo, A. Eskelinen, J. Firn, W. S. Harpole, Y. Hautier, K. P. Kirkman, K. J. Komatsu, R. Laungani, A. MacDougall, R. L. McCulley, J. L. Moore, J. W. Morgan, B. Mortensen, R. Ochoa Hueso, T. Ohlert, S. A. Power, J. Price, A. C. Risch, M. Schuetz, L. Shoemaker, C. Stevens, A. T. Strauss, P. M. Tognetti, R. Virtanen, and E. T. Borer. 2021. Temporal rarity is a better predictor of local extinction risk than spatial rarity. Ecology 102(11):e03504. 10.1002/ecy.3504. Copyright by the Ecological Society of America. Posted with permission
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