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排序方式: 共有198条查询结果,搜索用时 31 毫秒
191.
192.
Episodic death across species of desert shrubs 总被引:2,自引:0,他引:2
Extreme events shape population and community trajectories. We report episodic mortality across common species of thousands of long-lived perennials individually tagged and monitored for 20 years in the Colorado Desert of California following severe regional drought. Demographic records from 1984 to 2004 show 15 years of virtual stasis in populations of adult shrubs and cacti, punctuated by a 55-100% die-off of six of the seven most common perennial species. In this episode, adults that experienced reduced growth in a lesser drought during 1984-1989 failed to survive the drought of 2002. The significance of this event is potentially profound because population dynamics of long-lived plants can be far more strongly affected by deaths of adults, which in deserts potentially live for centuries, than by seedling births or deaths. Differential mortality and rates of recovery during and after extreme climatic events quite likely determine the species composition of plant and associated animal communities for at least decades. The die-off recorded in this closely monitored community provides a unique window into the mechanics of this process of species decline and replacement. 相似文献
193.
Pilar Santidrián Tomillo Jack S. Suss Bryan P. Wallace Kimberly D. Magrini Gabriela Blanco Frank V. Paladino James R. Spotila 《Marine Biology》2009,156(10):2021-2031
Reproductive output of leatherback turtles (Dermochelys coriacea) is affected by the stochastic nature of emergence success. Average emergence success of nests at Playa Grande, Costa Rica
was 0.38 ± 0.27. Incubation temperature affected development of leatherback turtle eggs and emergence of hatchlings from the
nest. We found that high temperatures reduced hatching success and emergence rate and increased embryonic mortality both early
and late during incubation at Playa Grande. There was a temporal effect on emergence success that resulted in more hatchlings
being produced at the beginning of the season, because of higher emergence success, than toward the end. Likewise, production
of hatchlings varied from year to year. The average annual reproductive output was 252 ± 141 hatchlings per female. The 2005–2006
nesting season had the highest emergence success and produced the greatest number of hatchlings per female compared to the
2004–2005 (+120%) and 2006–2007 (+41%) seasons. However, average clutch size (62 ± 10) and clutch frequency (9.45 ± 1.63),
were not different among years. Turtles that had nested a high number of years exhibited greater clutch frequency and arrived
earlier to nest than turtles that had nested in fewer numbers of years. Nesting when environmental conditions favor high developmental
success and emergence rate may constitute an advantageous reproductive strategy. 相似文献
194.
Hannah B. Vander Zanden Joseph B. Pfaller Kimberly J. Reich Mariela Pajuelo Alan B. Bolten Kristina L. Williams Michael G. Frick Brian M. Shamblin Campbell J. Nairn Karen A. Bjorndal 《Marine Biology》2014,161(3):585-598
Diet items and habitat constitute some of the environmental resources that may be used differently by individuals within a population. Long-term fidelity by individuals to particular resources exemplifies individual specialization, a phenomenon that is becoming increasingly recognized across a wide range of species. Less is understood about the consequences of such specialization. Here, we investigate the effects of differential foraging ground use on reproductive output in 183 loggerhead sea turtles (Caretta caretta) nesting at Wassaw Island, Georgia (31.89°N, 80.97°W), between 2004 and 2011 with resulting possible fitness effects. Stable isotope analysis was used to assign the adult female loggerheads to one of three foraging areas in the Northwest Atlantic Ocean. Our data indicate that foraging area preference influences the size, fecundity, and breeding periodicity of adult female loggerhead turtles. We also found that the proportion of turtles originating from each foraging area varied significantly among the years examined. The change in the number of nesting females across the years of the study was not a result of uniform change from all foraging areas. We develop a novel approach to assess differential contributions of various foraging aggregations to changes in abundance of a sea turtle nesting aggregation using stable isotopes. Our approach can provide an improved understanding of the influences on the causes of increasing or decreasing population trends and allow more effective monitoring for these threatened species and other highly migratory species. 相似文献
195.
Katrina M. Pagenkopp Lohan Jan R. McDowell Jeffrey D. Shields Kimberly S. Reece 《Marine Biology》2014,161(2):261-273
Hematodinium perezi (genotype III) is a parasitic dinoflagellate that infects blue crabs along the eastern seaboard and Gulf of Mexico, USA. In order to examine the intra-specific genetic variation of this parasite, eleven microsatellite markers from H. perezi (III) were amplified from 227 infected blue crabs collected during 2008–2009 from six sites in Virginia. Simultaneous infections with multiple genetic types in a single-host individual were common and observed in 42 % of the samples. The remaining 58 % of samples had a single allele per locus at all eight polymorphic loci suggesting that the life history stages of the parasite in the host hemolymph are likely haploid. The composition and distribution of multi-locus genotypes (MLG) from samples with infections of a single genetic type indicated high genotypic variation along the Delmarva Peninsula, Virginia, with no evidence of population structure. The lack of linkage disequilibrium combined with the large number of unique MLGs (84 %) is strong evidence for recombination in the life cycle, but the sexual stages remain undetermined. This is the first evidence of ploidy level, infections by multiple genetic types in an individual host animal, high levels of genotypic variation, and sexual reproduction for any species of Hematodinium. 相似文献
196.
AbstractAtrazine, an endocrine-disrupting compound and environmental pollutant, can have adverse effects on amphibian reproductive development and function. To determine the effects of atrazine on anuran gonadal development, Lithobates pipiens larvae were exposed from Gosner stage 25 through 1-month post metamorphosis to 0, 2, 20, or 200?μg/L atrazine or estradiol. Exposure to atrazine did not markedly alter tadpole growth, development, gonadal histology, or reproductive steroidogenesis. Testicular ovarian follicles appeared in L. pipiens metamorphs following all treatments, including controls, whereas ovotestes occurred only in positive controls. Testicular ovarian follicles may be a natural ontogenetic occurrence in this species while ovotestes indicate disruption in development. Establishing the normal pattern of reproductive development for anuran species and conducting comparisons in fully sexually differentiated animals is necessary to clarify the influence of endocrine disrupting compounds. 相似文献
197.
The provision of a secure, continuous energy supply is becoming an issue for all sectors of society and the food processing industry as a major energy user must address these issues. This paper identifies anaerobic digestion as an opportunity to go some way to achieving energy security in a sustainable manner. However, a number of energy management and waste reduction concepts must also be brought into play if the environmental, social and economic aspects of sustainability are to be balanced. The reporting of such activity will help to promote the green credentials of the industry. Cleaner production, supply chain and life cycle assessment approaches all have a part to play as tools supporting a new vision for integrated energy and waste management. Our reliance on high-energy processing, such as canning and freezing/chill storage, might also need re-assessment together with processing based on hurdle technology. Finally, the concepts of energy and power management for a distributed energy generation system must be brought into the food processing industry. 相似文献
198.
The Theory of Conservation Biology 总被引:2,自引:0,他引:2
Kimberly A. With 《Conservation biology》1997,11(6):1436-1440