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191.
Abstract– The introduction of Nile perch ( Lates niloticus ) into the Lake Victoria basin of East Africa has coincided with the decline or disappearance of hundreds of indigenous species. To mitigate additional biodiversity loss, we must learn what limits the spread of Nile perch and what habitats serve as refugia for prey species. Heavily vegetated wetlands may protect fishes from Nile perch predation by providing both structural and low-oxygen refugia for prey species tolerant of hypoxia. To examine the potential of wetlands as refugia we quantified the composition, persistence, and stability of fish assemblages in a wetland tributary of Lake Nabugabo, a satellite lake of Lake Victoria in which Nile perch have been introduced. Nile perch were extremely rare in the wetland, and nine of the 18 species that have disappeared from the open waters of the satellite lake were captured in the tributary in this study. Dissolved oxygen was chronically low in the river and may be important in shaping fish community characteristics. Faunal attenuation occurred as the dry season progressed and oxygen levels dropped; however, the most common species remained through seasonal changes. The chronically low oxygen conditions in the werland tributary may permit persistence of only hypoxia-tolerant species. However, wetland conditions seem to limit exploitation by Nile perch providing critical refugia for a subset of the basin fauna. 相似文献
192.
White Emma L. Thomasson J. Alex Auvermann Brent Kitchen Newell R. Pierson Leland Sandy Porter Dana Baillie Craig Hamann Hendrik Hoogenboom Gerrit Janzen Todd Khosla Rajiv Lowenberg-DeBoer James McIntosh Matt Murray Seth Osborn Dave Shetty Ashoo Stevenson Craig Tevis Joe Werner Fletcher 《Precision Agriculture》2021,22(1):306-315
Precision Agriculture - Data-centric technology has not undergone widespread adoption in production agriculture but could address global needs for food security and farm profitability. Participants... 相似文献
193.
LI Cun-dong BAI Zhi-ying Ye G Miyagi M Chapman S Reader S M LIU Chun-ji 《中国农业科学(英文版)》2011,10(2):159-165
Rapid expansion of leaves of early-stage plants in wheat produced by chromosomal control of characteristics related to rapid expansion of the first six leaves of wheat were investigated using a set of single chromosome substitution lines under two different temperature regimes(TRs).Results from this study indicated that several chromosomes could be responsible for each of the four characteristics studied(including leaf width,leaf length,leaf elongation rate and leaf appearance index)and that different chromosomes may be responsible for the same characteristics at different TRs.Only a small number of substitutions that showed the most significant effects on leaf length were found among those that showed the most significant effects on leaf width,providing further evidence that these two characteristics are likely controlled by different sets of genes.Substitutions 4B,4D,and 5A are among those that were repeatedly detected to having significant effects on different leaf characteristics at the lower-TR and genes residing on these three chromosomes could be homologous.This possibility and its implication are discussed. 相似文献
194.
Several reports have cast doubt on the cerebral origin of alpha and kappa electroencephalogram activity by charging that they are artifacts related to eye activity. Data are cited which eliminate the corneoretinal potential of the eyeball, tremor of the extraocular muscles, eye position, accommodation, and eye flutter as sources of alpha and kappa electroencephalogram activity. A subject with both eyes removed showed normal alpha and kappa electroencephalogram activity. Marked left-right differences in alpha activity were not found in one-eyed subjects whose eyes and extraocular muscles were completely removed on one side. 相似文献
195.
Quantitative trait loci for agronomic and seed quality traits in an F2 and F4:6 soybean population 总被引:2,自引:1,他引:2
A. Chapman V.R. Pantalone A. Ustun F.L. Allen D. Landau-Ellis R.N. Trigiano P.M. Gresshoff 《Euphytica》2003,129(3):387-393
Molecular breeding is becoming more practical as better technology emerges. The use of molecular markers in plant breeding
for indirect selection of important traits can favorably impact breeding efficiency. The purpose of this research is to identify
quantitative trait loci (QTL) on molecular linkage groups (MLG) which are associated with seed protein concentration, seed
oil concentration, seed size, plant height, lodging, and maturity, in a population from a cross between the soybean cultivars
‘Essex’ and ‘Williams.’ DNA was extracted from F2 generation soybean leaves and amplified via polymerase chain reaction (PCR) using simple sequence repeat (SSR) markers. Markers
that were polymorphic between the parents were analyzed against phenotypic trait data from the F2 and F4:6 generation. For the F2 population, significant additive QTL were Satt540 (MLG M, maturity,
r2 = 0.11; height, r2 = 0.04, seed size, r2= 0.06], Satt373 (MLG L, seed size, r2 = 0.04; height, r2 = 0.14), Satt50 (MLG A1, maturity r2 = 0.07), Satt14 (MLG D2, oil, r2 = 0.05), and Satt251 (protein r2 = 0.03, oil, r2 =0.04). Significant dominant QTL for the F2 population were Satt540 (MLG M,height, r2 = 0.04; seed size, r2 = 0.06) and Satt14 (MLG D2, oil, r2 = 0.05). In the F4:6 generation significant additive QTL were Satt239 (MLGI, height, r2 = 0.02 at Knoxville, TN and r2 = 0.03 at Springfield, TN), Satt14 (MLG D2, seed size, r2 = 0.14 at Knoxville, TN), Satt373 (MLG L, protein, r2 = 0.04 at Knoxville, TN) and Satt251 (MLG B1, lodging r2 = 0.04 at Springfield, TN). Averaged over both environments in the F4:6 generation, significant additive QTL were identified as Satt251 (MLG B1, protein, r2 = 0.03), and Satt239 (MLG I, height, r2 = 0.03). The results found in this study indicate that selections based solely on these QTL would produce limited gains (based
on low r2 values). Few QTL were detected to be stable across environments. Further research to identify stable QTL over environments
is needed to make marker-assisted approaches more widely adopted by soybean breeders.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
196.
197.
198.
Katrina V. Cook Andrea J. Reid David A. Patterson Kendra A. Robinson Jacqueline M. Chapman Scott G. Hinch Steven J. Cooke 《Fish and Fisheries》2019,20(1):25-43
Discarding non‐target fish from commercial fisheries is controversial and has been a persistent concern for fisheries managers globally. Discard management strategies typically begin by understanding mortality rates among discarded fish, a challenging task given the dynamic, highly context‐specific nature of fisheries. An alternative is to develop our knowledge of how stressors operate by first understanding the causes of mortality that drive this context dependence. Particularly relevant to mitigation efforts is an understanding of how fish respond to the physical factors of fishing, such as the gear itself and methods of fishing and handling the gear. We provide a synthesis of how commercial fishing methods may influence discard mortality and outline means by which capture‐induced stress and injury can be mitigated for common commercial gear types, emphasizing method variants or alternatives during capture, handling, and release that could improve survival. This synthesis identifies exhaustion and injury as the most detrimental and ubiquitous stressors experienced by discarded fish, with few options for mitigating their effects. Trawls and hanging net fisheries are identified as the most harmful gears for by‐catch, characterized by high stress regardless of method variants and limited options for mitigation. Irrespective of gear type and type of stressor, minimizing durations of capture and handling and encouragement of good handling behaviour (e.g., during landing and sorting) will reduce the magnitude of stress and injury in fish, and ultimately increase survival. 相似文献
199.
200.
Andrea J. Reid Maxwell J. Farrell Max N. Luke Lauren J. Chapman 《Ecology of Freshwater Fish》2013,22(3):421-429
Aquatic hypoxia can affect predator‐prey interactions by altering the success rate of the predator and/or the vulnerability of prey. For example, in the Lake Victoria basin of East Africa, native prey exploit hypoxic wetlands as refugia from predation by introduced Nile perch (Lates niloticus). Here, it is predicted that species exploitation of wetlands depends on their hypoxia tolerance relative to the heterogeneity of wetland hypoxia. In this study, we compared the hypoxia tolerance of four fish taxa that differ in their use of hypoxic wetlands in Lake Nabugabo, Uganda: the cichlid Pseudocrenilabrus multicolor victoriae that inhabits the dense swamp interior; and three taxa that inhabit wetland ecotones including Nile tilapia (Oreochromis niloticus), L. niloticus and juvenile endemic haplochromine cichlids. We characterised hypoxia tolerance by exposing fish to progressive hypoxia and quantifying variation in aquatic surface respiration (ASR). The effect of body size on tolerance was explored in L. niloticus by quantifying ASR behaviour across a range of size classes. ASR behaviour was also compared between O. niloticus groups from wetland versus open‐water habitats to detect habitat‐associated intraspecific variation. The most tolerant taxon was the swamp specialist P. multicolor, indicated by its low ASR thresholds and small percentage of fish using ASR during the final sample interval. The other three taxa did not differ in ASR behaviour, and no differences were detected between O. niloticus groups. Body size effects were present for L. niloticus suggesting a lower tolerance to hypoxia in larger‐bodied individuals, thus limiting their ability to penetrate wetlands. 相似文献