905 resultados para endangered bird
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We used random amplified polymorphic DNA markers (RAPDs) to assess genetic variation between- and within-populations of Anisodus tanguticus (Solanaceae), an endangered perennial endemic to the Qinghai-Tibetan Plateau with important medicinal value. We recorded a total of 92 amplified bands, using 12 RAPD primers, 76 of which (P = 82.61%) were polymorphic, and calculated values of H-t and H-sp of 0.3015 and 0.4459, respectively, suggesting a remarkably high rate of genetic variation at the species level. The average within-population diversity also appeared to be high, with P, H-e and H-pop values of 55.11%, 0.1948 and 0.2918, respectively. Analyses of molecular variance (AMOVA) showed that among- and between-population genetic variation accounted for 67.02% and 32.98% of the total genetic variation, respectively. In addition, Nei's coefficient of differentiation (G(ST)) was found to be high (0.35), confirming the relatively high level of genetic differentiation among the populations. These differentiation coefficients are higher than mean corresponding coefficients for outbreeding species, but lower than reported coefficients for some rare species from this region. The genetic structure of A. tanguticus has probably been shaped by its breeding attributes, biogeographic history and human impact due to collection for medicinal purposes. The observed genetic variations suggest that as many populations as possible should be considered in any planned in situ or ex situ conservation programs for this species.
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Reproductive failure results in many plant species becoming endangered. However, little is known of how and to what extent pollinator shifts affect reproductive performance of endangered species as a result of the artificial introduction of alien insects. In this study we examined breeding systems, visitor species, visiting frequency and seed set coefficients of Swertia przewalskii in two years that had different dominant pollinator species (native vs. alien). Flowers of this species were protandrous and herkogamous and insects were needed for the production of seeds. The stigmatic receptivity of this species was shorter than for other gentians. No significant difference in seed set coefficient was found for hand-pollinated plants between the two years, indicating that pollinator shift only had a minor effect on this plant's breeding system. The commonest pollinators in 2002 were native bumblebees, alien honeybees and occasional solitary bees, however, only alien honeybees were observed in 2004. The flower visitation rate in both years was relatively high, although the total visit frequency decreased significantly in 2004. The control flowers without any treatment produced significantly fewer seed sets in 2004 than in 2002. In the past decade the seed production of this species may have partly decreased due to pollination by alien honeybees, however, we suggest that they might have acted as alternative pollinators ensuring seed production of S. przewalskii when native pollinators were unavailable. The main reason that this plant is endangered is probably the result of habitat destruction, but changes in land use, namely intensified agricultural practice and unfavorable animal husbandry have also contributed to its decline. We recommend that in-situ conservation, including the establishment of a protected area, is the best way to preserve this species effectively.
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Swertia przewalskii Pissjauk. (Gentianaceae) is a critically endangered and endemic plant of the Qinghai-Tibet Plateau in China. RAPD and ISSR analyses were carried out on a total of 63 individuals to assess the extent of genetic variation in the remaining three populations. Percentage of polymorphic bands was 94% (156 bands) for RAPD and 96% (222 bands) for ISSR. A pairwise distance measure calculated from the RAPD and ISSR data was used as input for analysis of molecular variance (AMOVA). AMOVA indicated that a high proportion of the total genetic variation (52% for RAPD and 56% for ISSR) was found among populations; pairwise Phi(ST) comparisons showed that the three populations examined were significantly different (p < 0.001). Significant genetic differentiation was found based on different measures (AMOVA and Hickory theta(B)) in S. przewalskii (0.52 on RAPD and 0.56 on ISSR; 0.46 on RAPD and 0.45 on ISSR). The differentiation of the populations corresponded to low average gene flow (0.28 based on RAPD and 0.31 based on ISSR), whereas genetic distance-based clustering and coalescent-based assignment analyses revealed significant genetic isolation among populations. Our results indicate that genetic diversity is independent of population size. We conclude that although sexual reproduction and gene flow between populations of S. przewalskii are very limited, they have preserved high levels of genetic diversity. The main factors responsible for the high level of difference among populations are the isolation and recent fragmentation under human disturbance.
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http://www.archive.org/details/bibleworkinbible00birduoft
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Commercial capture fisheries produce huge quantities of offal, as well as undersized and unwanted catch in the form of discards. Declines in global catches and legislation to ban discarding will significantly reduce discards, but this subsidy supports a large scavenger community. Understanding the potential impact of declining discards for scavengers should feature in an eco-system based approach to fisheries management, but requires greater knowledge of scavenger/fishery interactions. Here we use bird-borne cameras, in tandem with GPS loggers, to provide a unique view of seabird/fishery interactions. 20,643 digital images (one min 21) from ten bird-borne cameras deployed on central place northern gannets Morus bassanus revealed that all birds photographed fishing vessels. These were large (>15 m) boats, with no small-scale vessels. Virtually all vessels were trawlers, and gannets were almost always accompanied by other scavenging birds. All individuals exhibited an Area-Restricted Search (ARS) during foraging, but only 42% of ARS were associated with fishing vessels, indicating much 'natural' foraging. The proportion of ARS behaviours associated with fishing boats were higher for males (81%) than females (30%), although the reasons for this are currently unclear. Our study illustrates that fisheries form a very important component of the prey-landscape for foraging gannets and that a discard ban, such as that proposed under reforms of the EU Common Fisheries Policy, may have a significant impact on gannet behaviour, particularly males. However, a continued reliance on 'natural' foraging suggests the ability to switch away from scavenging, but only if there is sufficient food to meet their needs in the absence of a discard subsidy.
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The comment by Votier et al. (2008) on our recently published article (Wynn et al. 2007) contains two main criticisms: (i) that our analytical approach is inappropriate and (ii) that we have failed to acknowledge other factors that may have contributed to the change in Balearic Shearwater numbers recorded throughout northwest European waters. We strongly disagree with both these criticisms.
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The Nassau grouper, Epinephelus striatus (Bloch, 1792), is an endangered species that has been historically overexploited in numerous fisheries throughout its range in the Caribbean and tropical West Atlantic. Data relating fishery exploitation levels to stock abundance of the species are deficient, and protective regulations for the Nassau grouper are yet to be implemented in the Turks and Caicos Islands (TCI). The goal of this study was to conduct a stock assessment and evaluate the exploitation status of the Nassau grouper in the TCI. Materials and methods. Calibrated length cohort analysis was applied to published fisheries data on Nassau grouper landings in the TCI. The total lengths of Nassau groupers among the catches of spearfishers, lobster trappers, and deep sea fishers on the island of South Caicos during 2006 and 2008 were used with estimates of growth, natural mortality, and total annual landings to derive exploitation benchmarks. Results. The TCI stock experienced low to moderate fishing mortality (0.28, 0.18) and exploitation rates (0.49, 0.38) during the period of the study (2006, 2008). However, 21.2%-64.4% of all landings were reproductively immature. Spearfishing appeared to contribute most to fishing mortality relative to the use of lobster traps or hydraulic reels along bank drop-offs. Conclusion. In comparison with available fisheries data for the wider Caribbean, the results reveal the TCI as one of the remaining sites, in addition to the Bahamas, with a substantial Nassau grouper stock. In light of increasing development and tourism in the TCI, continued monitoring is essential to maintain sustainable harvesting practices.
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1. The freshwater pearl mussel Margaritifera margaritifera L. is globally endangered and is threatened by commercial exploitation, pollution and habitat loss throughout its range. Captive breeding would be a valuable tool in enhancing the status of M. margaritifera in the UK. 2. We have developed a semi-natural system for successfully infecting juvenile brown trout with glochidial M. margaritifera, and culturing juvenile mussels in experimental tanks where glochidial M. margaritifera can excyst from fish gills and settle into sediment. 3. Infected fish had less than 1% mortality. Levels of infection varied among fish. Two yearly cohorts of juvenile M. margaritifera were identified from samples of sediment taken from each experimental tank. Individuals range in size from 1.4 mm (2000 cohort) to >3 mm in length (1999 cohort). 4. The number of juvenile M. margaritifera present in the two experimental tanks are estimated to be between 3600 (tank A) and 0 (tank B) for the putative 1999 cohort and between 6000 (tank A) and 13 000 (tank B) for the putative 2000 cohort. 5. This pioneering method for large-scale cultivation of juvenile M. margaritifera is intermediate between the release of infected fish into rivers and the intensive cultivation systems developed in continental Europe and the USA for other species of unionid. This is the first time that large numbers of M. margaritifera have been cultured and represents a significant breakthrough in the conservation of this globally endangered Red Data List species. The method is straightforward and is most cost-effective when undertaken alongside established hatchery processes.
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Mammillaria gaumeri (Britton & Ross) Orcutt (Cactaceae), an endemic plant of the Yucatan Peninsula, is included by the Mexican government in the list of species that require special protection. Its natural habitat is now restricted to fragmented areas and protection programs involve botanical gardens in growing individuals rescued from disturbed areas. Little information is available on the reproductive characteristics of this species and nothing is known of its pollinators. We investigated the visitors of M. gaumeri flowers, collecting and observing bee species in its natural habitat (i.e., coastal dune) and in a botanical garden, where coastal dune vegetation had been created. Observations were made on plants whose density was artificially increased by grouping flowering individuals. At each site, we: 1) collected insects visiting the flowers; 2) recorded number of visits; and 3) video-recorded bee movements on the flowers. As expected, the number of bee species and visitation frequency were higher at the botanical garden than at the coastal dune. After landing on a flower, bees either inspected the anthers or dived among them. These behaviors, carried out by all observed species, seemed related to the state of the anthers (full or empty of pollen) and stigma lobes (opened or closed). Specifically, visits lasted longer when anthers were full of pollen and stigma lobes were opened. The same bee species recorded on the dune were also recorded at the botanical garden, suggesting that the artificial dune at the botanical garden offered suitable conditions for the natural pollinators of this endangered cactus.