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71.
Patterns and drivers of fish extirpations in rivers of the American Southwest and Southeast 下载免费PDF全文
John S. Kominoski Albert Ruhí Megan M. Hagler Kelly Petersen John L. Sabo Tushar Sinha Arumugam Sankarasubramanian Julian D. Olden 《Global Change Biology》2018,24(3):1175-1185
Effective conservation of freshwater biodiversity requires spatially explicit investigations of how dams and hydroclimatic alterations among climate regions may interact to drive species to extinction. We investigated how dams and hydroclimatic alterations interact with species ecological and life history traits to influence past extirpation probabilities of native freshwater fishes in the Upper and Lower Colorado River (CR), Alabama‐Coosa‐Tallapoosa (ACT), and Apalachicola‐Chattahoochee‐Flint (ACF) basins. Using long‐term discharge data for continuously gaged streams and rivers, we quantified streamflow anomalies (i.e., departure “expected” streamflow) at the sub‐basin scale over the past half‐century. Next, we related extirpation probabilities of native fishes in both regions to streamflow anomalies, river basin characteristics, species traits, and non‐native species richness using binomial logistic regression. Sub‐basin extirpations in the Southwest (n = 95 Upper CR, n = 130 Lower CR) were highest in lowland mainstem rivers impacted by large dams and in desert springs. Dampened flow seasonality, increased longevity (i.e., delayed reproduction), and decreased fish egg sizes (i.e., lower parental care) were related to elevated fish extirpation probability in the Southwest. Sub‐basin extirpations in the Southeast (ACT n = 46, ACF n = 22) were most prevalent in upland rivers, with flow dependency, greater age and length at maturity, isolation by dams, and greater distance upstream. Our results confirm that dams are an overriding driver of native fish species losses, irrespective of basin‐wide differences in native or non‐native species richness. Dams and hydrologic alterations interact with species traits to influence community disassembly, and very high extirpation risks in the Southeast are due to interactions between high dam density and species restricted ranges. Given global surges in dam building and retrofitting, increased extirpation risks should be expected unless management strategies that balance flow regulation with ecological outcomes are widely implemented. 相似文献
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Almir S Zanca Renato Vicentini Fausto A Ortiz-Morea Luiz EV Del Bem Marcio J da Silva Michel Vincentz Fabio TS Nogueira 《BMC plant biology》2010,10(1):260
Background
MicroRNAs (miRNAs) are small regulatory RNAs, some of which are conserved in diverse plant genomes. Therefore, computational identification and further experimental validation of miRNAs from non-model organisms is both feasible and instrumental for addressing miRNA-based gene regulation and evolution. Sugarcane (Saccharum spp.) is an important biofuel crop with publicly available expressed sequence tag and genomic survey sequence databases, but little is known about miRNAs and their targets in this highly polyploid species. 相似文献74.
Pollution of aquatic ecosystems often results in adverse environmental disturbances, including physiological and/ or histomorphological changes in fish. The health of Clarias gariepinus sampled from two polluted water bodies, Orlando Dam and a pond in the Klipspruit wetland catchment, Soweto, was investigated in 2015–2016. Limited fish health-related data is available for this highly impacted freshwater ecosystem. Fish were collected between April 2015 and February 2016. A necropsy and a histological assessment were done on various target organs of each fish. Water and sediment samples were analysed for selected organic and inorganic compounds. Macroscopic assessment revealed abnormally shaped urogenital papillae, morphological alterations of the gonads, as well as discoloration of liver tissue. These observations were supported by microscopic evidence of hepatic histological alterations in fish from Orlando Dam, as well as the presence of both female and male gonadal tissue (intersex) in 13.6% and 50% of fish from the wetland pond and the Orlando Dam, respectively. Water analyses showed high levels of faecal coliform bacteria and metal concentrations and sediment analyses showed detectable levels of potential endocrine disrupting chemicals. 相似文献
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Ecdysterone added in vitro to wing tissue from diapausing Antheraea polyphemus pupae induced the synthesis of several epidermal cell proteins. This is one of few instances in which any steroid hormone in physiological concentrations has been able to induce specific protein synthesis in target tissue in vitro soon after hormone stimulation. Hormone-treated tissue was incubated with 3H-leucine while control tissue was incubated with 14C-leucine. Polyacrylamide gel electrophoretic distribution of labelled wing tissue proteins after ecdysterone stimulation in vitro for various periods of time was determined. The ratio emphasized the areas of increased protein synthesis due to ecdysterone. These areas of increased protein synthesis were reproducible with several ecdysterone concentrations and with different incubation times. Induction of protein synthesis occurs at an earlier time period when the hormone dosage is higher, i.e. the lower the dosage, the longer it is necessary for exposure of tissue to hormone. α-Ecdysone, known to initiate the moulting process in vitro in some insect species, also induced protein synthesis. Cortisol, a mammalian steroid hormone, produced no hormone specific protein synthesis. Therefore, the results seen with ecdysterone and α-ecdysone are not the result of non-specific steroid stimulation. When no hormone was added to the incubation medium (control), only one area of the polyacrylamide gel demonstrated protein synthesis. Therefore, there are a few proteins being synthesized in vitro in wing tissue, removed from diapausing animals without hormone stimulation, which may be related to the ‘injury phenomenon’. Protein banding patterns were also determined and compared with the radioactivity profile. The study of such early biochemical and physiological responses of target tissue to hormones will aid in our understanding of a hormone's mechanism of action, since the earlier an event occurs, the more likely that it is the primary result of hormone stimulation. 相似文献
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Experiments were performed to compare the agonistic and antagonistic properties of the high affinity antiestrogen, H1285, and the low affinity antiestrogens CI-628 and tamoxifen on rat uterine growth and morphology. Myometrial and stromal areas and endometrial epithelial cell heights were calculated. Whereas all antiestrogens displayed some degree of estrogenic response, only H1285 at 5 or 0.5 micrograms was an effective inhibitor of E2 induced proliferative responses in the myometrium, stroma, and endometrial epithelium. All antiestrogens caused tremendous endometrial hypertrophy. 相似文献
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