RUNAWAY COEVOLUTION: ADAPTATION TO HERITABLE AND NONHERITABLE ENVIRONMENTS

Populations evolve in response to the external environment, whether abiotic (e.g., climate) or biotic (e.g., other conspecifics). We investigated how adaptation to biotic, heritable environments differs from adaptation to abiotic, nonheritable environments. We found that, for the same selection coefficients, the coadaptive process between genes and heritable environments is much faster than genetic adaptation to an abiotic nonheritable environment. The increased rate of adaptation results from the positive association generated by reciprocal selection between the heritable environment and the genes responding to it. These associations result in a runaway process of adaptive coevolution, even when the genes creating the heritable environment and genes responding to the heritable environment are unlinked. Although tightening the degree of linkage accelerates the coadaptive process, the acceleration caused by a comparable amount of inbreeding is greater, because inbreeding has a cumulative effect on reducing functional recombination over generations. Our results suggest that that adaptation to local abiotic environmental variation may result in the rapid diversification of populations and subsequent reproductive isolation not directly but rather via its effects on heritable environments and the genes responding to them.     

Influence of learning on range expansion and adaptation to novel habitats

Learning has been postulated to ‘drive’ evolution, but its influence on adaptive evolution in heterogeneous environments has not been formally examined. We used a spatially explicit individual‐based model to study the effect of learning on the expansion and adaptation of a species to a novel habitat. Fitness was mediated by a behavioural trait (resource preference), which in turn was determined by both the genotype and learning. Our findings indicate that learning substantially increases the range of parameters under which the species expands and adapts to the novel habitat, particularly if the two habitats are separated by a sharp ecotone (rather than a gradient). However, for a broad range of parameters, learning reduces the degree of genetically‐based local adaptation following the expansion and facilitates maintenance of genetic variation within local populations. Thus, in heterogeneous environments learning may facilitate evolutionary range expansions and maintenance of the potential of local populations to respond to subsequent environmental changes.     

Preventing Ultimate Harm as the Justification for Biomoral Modification

Most advocates of biogenetic modification hope to amplify existing human traits in humans in order to increase the value of such traits as intelligence and resistance to disease. These advocates defend such enhancements as beneficial for the affected parties. By contrast, some commentators recommend certain biogenetic modifications to serve social goals. As Ingmar Persson and Julian Savulescu see things, human moral psychology is deficient relative to the most important risks facing humanity as a whole, including the prospect of Ultimate Harm, the point at which worthwhile life is forever impossible on the planet. These risks can be mitigated, they say, by enhancing moral psychology in novel ways. Persson and Savulescu argue that some parents should modify the underlying biogenetics of their children's moral psychology, if such measures were safe and effective, but they admit these interventions may not decouple humanity from Ultimate Harm. Neither are these modifications the only options, they concede, for addressing risks to humanity. Even with these concessions, saving humanity from itself is a fairly poor reason to modify the moral psychology of children. In most ways, adults would be better candidates, morally speaking, for modifications of psychology. Even then, there is no direct link between morally enhanced human beings and the hoped‐for effect of better protection from Ultimate Harm. Asserting a general duty of all to contribute to the avoidance of Ultimate Harm is a better moral strategy than intervening in the moral psychology of some, even though meeting that duty may involve substantial interference with the free exercise of one's interests.     

Effects of the supply levels and ratios of nitrogen and phosphorus on seed traits of Chenopodium glaucum

全球氮沉降不仅改变土壤氮和磷的有效性, 同时也改变氮磷比例。氮磷供应量、比例及其交互作用可能会影响植物种子性状。该研究在内蒙古草原基于沙培盆栽实验种植灰绿藜(Chenopodium glaucum), 设置3个氮磷供应量水平和3个氮磷比例的正交实验来探究氮磷供应量、比例及其交互作用对灰绿藜种子性状的影响。结果发现氮磷供应量对种子氮浓度、磷浓度和萌发率影响的相对贡献(15%-24%)大于氮磷比例(3%-7%), 而种子大小只受氮磷比例的影响。同时氮磷供应量和比例之间的交互作用显著影响种子氮浓度和磷浓度。同等氮磷比例情况下, 低量养分供应提高种子氮浓度、磷浓度和萌发率。氮磷比例只有在养分匮乏的环境中才会对种子大小和萌发率产生显著影响。总之, 灰绿藜种子不同性状对氮或磷限制的敏感性不同, 同时种子性状也对养分限制表现出适应性和被动响应。     

生态意识及其主要特点

一、生态意识产生的时代背景生态意识作为人类思想的先进观念,产生于20世纪后半叶。产业革命以来二百多年,人类依据先进科学技术武装的强大生产力,无限制地向自然进     

Novel Monte Carlo dose calculation algorithm for robotic radiosurgery with multi leaf collimator: Dosimetric evaluation

PurposeAt introduction in 2014, dose calculation for the first MLC on a robotic SRS/SBRT platform was limited to a correction-based Finite-Size Pencil Beam (FSPB) algorithm. We report on the dosimetric accuracy of a novel Monte Carlo (MC) dose calculation algorithm for this MLC, included in the Precision™ treatment planning system.MethodsA phantom was built of one slab (5.0 cm) of lung-equivalent material (0.09…0.29 g/cc) enclosed by 3.5 cm (above) and 5 cm (below) slabs of solid water (1.045 g/cc). This was irradiated using rectangular (15.4 × 15.4 mm² to 53.8 × 53.7 mm²) and two irregular MLC-fields. Radiochromic film (EBT3) was positioned perpendicular to the slabs and parallel to the beam. Calculated dose distributions were compared to film measurements using line scans and 2D gamma analysis.ResultsMeasured and MC calculated percent depth dose curves showed a characteristic dose drop within the low-density region, which was not correctly reproduced by FSPB. Superior average gamma pass rates (2%/1 mm) were found for MC (91.2 ± 1.5%) compared to FSPB (55.4 ± 2.7%). However, MC calculations exhibited localized anomalies at mass density transitions around 0.15 g/cc, which were traced to a simplification in electron transport. Absence of these anomalies was confirmed in a modified build of the MC engine, which increased gamma pass rates to 96.6 ± 1.2%.ConclusionsThe novel MC algorithm greatly improves dosimetric accuracy in heterogeneous tissue, potentially expanding the clinical use of robotic radiosurgery with MLC. In-depth, independent validation is paramount to identify and reduce the residual uncertainties in any software solution.     

The effects of environment and ownership on children's innovation of tools and tool material selection

Research indicates that in experimental settings, young children of 3–7 years old are unlikely to devise a simple tool to solve a problem. This series of exploratory studies done in museums in the US and UK explores how environment and ownership of materials may improve children''s ability and inclination for (i) tool material selection and (ii) innovation. The first study takes place in a children''s museum, an environment where children can use tools and materials freely. We replicated a tool innovation task in this environment and found that while 3–4 year olds showed the predicted low levels of innovation rates, 4–7 year olds showed higher rates of innovation than the younger children and than reported in prior studies. The second study explores the effect of whether the experimental materials are owned by the experimenter or the child on tool selection and innovation. Results showed that 5–6 year olds and 6–7 year olds were more likely to select tool material they owned compared to tool material owned by the experimenter, although ownership had no effect on tool innovation. We argue that learning environments supporting tool exploration and invention and conveying ownership over materials may encourage successful tool innovation at earlier ages.     

Effects of the level of early productivity on the lifespan of ewes in contrasting flock environments

Selection for high levels of prolificacy has allowed substantial improvements in the production efficiency of New Zealand (NZ) sheep farms, but the consequences on ewe lifetime performance are mostly unknown. In this study, the relationship between the level of prolificacy early in ewes’ productive lives and their probability to survive later (i.e. stayability) was evaluated in two contrasting NZ flock environments. Records were obtained from 6605 ewes from four ram breeder flocks representing either a moderate (n=2) or a highly variable (n=2) nutritional environment. All ewes lambed for the first time at 2 years of age and were mated the following year. The number of lambs born during the first 2 years of productive life (NLB_2–3) was used as a measure of early prolificacy. Effects of NLB_2–3 on stayability to 4, 5, 6, 7 and 8 years old were analysed using logistic regression. Curvilinear effects (logit-transformed) were detected (P<0.05) until stayability to 6 years and to 8 years old in the highly variable and the moderate environment, respectively. The NLB_2–3 that resulted in maximum expected stayability to various ages was 3.9 to 4.2, and 4.5 to 4.7 lambs in the highly variable and in the moderate flock environments, respectively. In addition, ewe stayability was reduced when the proportion of the litter that survived from birth to weaning (i.e. ewe rearing ability) was submaximal during the early productive life. High prolific ewes had a low rearing ability whatever the environment whereas the rearing ability of lowly prolific ewes was apparently more sensitive to the nutritional environment. The poor maternal performance of ewes with low levels of NLB_2–3 led to a premature culling by breeders whereas the high early reproductive effort associated with high levels of NLB_2–3 seemed to be at the cost of ewes’ survival, even in the moderate flock environment. In conclusion, the flock environment influenced the level of early prolificacy beyond which ewe longevity was reduced. It is suggested that further selection for high and early prolificacy in NZ flocks is likely to impair ewes’ lifetime productivity.