Bad Patches Research Articles

Spatially explicit modeling of metapopulation dynamics of broadcast spawners and stabilizing/destabilizing effects of heterogeneity of quality across local habitats

Many coastal invertebrate species are broadcast spawners. These species have a highly sedentary adult stage and disperse by oceanic transport of planktonic larvae. One commercially important group of broadcast spawners is abalones, which live in suitable habitat patches of rock reefs that are discretely distributed. Because of these life-history and habitat characteristics, abalones tend to exhibit a metapopulation structure. Despite fisheries management and the release of juveniles, wild populations of broadcast spawners have undergone dramatic reductions in density due to overexploitation, which has been partly attributed to a failure to account for spatial structure. To clarify the relationship between the persistence of a metapopulation and the bottleneck that occurs during reproduction and dispersal processes caused by spatial structure, we developed a spatially explicit metapopulation model accounting for the effects of both life history and fishery pressure. By analyzing the model, we derived a metric to evaluate metapopulation quality as the leading eigenvalue of a non-negative matrix (the landscape matrix). Using this measure, we clarified that the effect of spatial structure on metapopulation stability is explained well by the mean and variance of parameter values across patches under the condition in which the heterogeneity of the metapopulation network is weak. In particular, the presence of both a higher average and higher variance of quality in the landscape could indicate stable fishery stocks under certain conditions. For example, when the decline in the mean longevity of local patch due to the fishery pressures gradually diminishes, the rescue effects by good patches would work more effectively than the negative effect of bad patches and then the stabilizing effect of spatial heterogeneity could be observed in a metapopulation. Furthermore, optimal patch characteristics for the improvement of quality strongly depend on specific parameter values. For example, when adult fertility is improved, a patch with higher “source” ability is more suitable. In contrast, when the settlement success of planktonic larvae is improved or fishery pressure is reduced, a patch with higher “buffer” ability is more suitable for the improvement of fishery management.

Spreading speeds for stage structured plant populations in fragmented landscapes

Landscape fragmentation has huge ecological and economic implications and affects the spatial dynamics of many plant species. Determining the speed of population spread in fragmented/heterogeneous landscapes is therefore of utmost importance to ecologists. Stage-structured integrodifference equations (IDEs) are deterministic models which accurately reflect the life cycles and dispersal patterns for numerous species. Existing approximations to wave-speeds consider only particular kernels, or landscapes in which the scale of variation is much smaller than the dispersal scale. We propose an analytical approximation to the wave-speeds of IDE solutions with periodic landscapes of alternating good and bad patches, where the dispersal scale is greater than the extent of each good patch and where the ratio of the demographic rates in the good and bad patches is given by a small parameter, denoted as ε. We formulate this approximation for the Gaussian and Laplace dispersal kernels and for stage structured and non-stage structured populations, and compare the results against numerical simulations. We find that the approximation is accurate for the landscapes considered, and that the type of dispersal kernel affects the relationship between landscape structure, as classified by landscape period and good patch size, and the spreading speed. This indicates that accurately fitting a kernel to data is important in determining the relationship between landscape structure and spreading speed.

Contributions of high- and low-quality patches to a metapopulation with stochastic disturbance

Studies of time-invariant matrix metapopulation models indicate that metapopulation growth rate is usually more sensitive to the vital rates of individuals in high-quality (i.e., good) patches than in low-quality (i.e., bad) patches. This suggests that, given a choice, management efforts should focus on good rather than bad patches. Here, we examine the sensitivity of metapopulation growth rate for a two-patch matrix metapopulation model with and without stochastic disturbance and found cases where managers can more efficiently increase metapopulation growth rate by focusing efforts on the bad patch. In our model, net reproductive rate differs between the two patches so that in the absence of dispersal, one patch is high quality and the other low quality. Disturbance, when present, reduces net reproductive rate with equal frequency and intensity in both patches. The stochastic disturbance model gives qualitatively similar results to the deterministic model. In most cases, metapopulation growth rate was elastic to changes in net reproductive rate of individuals in the good patch than the bad patch. However, when the majority of individuals are located in the bad patch, metapopulation growth rate can be most elastic to net reproductive rate in the bad patch. We expand the model to include two stages and parameterize the patches using data for the softshell clam, Mya arenaria. With a two-stage demographic model, the elasticities of metapopulation growth rate to parameters in the bad patch increase, while elasticities to the same parameters in the good patch decrease. Metapopulation growth rate is most elastic to adult survival in the population of the good patch for all scenarios we examine. If the majority of the metapopulation is located in the bad patch, the elasticity to parameters of that population increase but do not surpass elasticity to parameters in the good patch. This model can be expanded to include additional patches, multiple stages, stochastic dispersal, and complex demography.

Intermediate spatial variations on acorn predation shapes Holm oak establishment within a Mediterranean landscape context

There is an emerging interest in analyzing the effects of seed predation and its consequences for plant recruitment across the landscape. The main goals of this study were to assess (1) whether seed predation varies among spatial levels of the landscape, (2) whether there are differences between pre- and post-dispersal seed predation and, (3) whether these differences are due to different animal species with different perception of the landscape and thus different activity ranges. The study system was a mosaic landscape composed of patches of different vegetation types (oak and pine woodlands and shrublands) and microhabitats intermingled. Pre-dispersal acorn predation varied between patches, trees, and predator species. Wild boar rooting activity was widely distributed through the landscape and mainly focused on pine woodlands while rodents′ feeding activity was mainly centered on local scales within oak woodland patches. The patch spatial level consistently appears to be the key explanatory variable for pre- and post-dispersal acorn predation. Furthermore, the post-dispersal percentage of seed predation and emergence also differed among spatial levels. Within the same vegetation type, different microhabitats did not show significant differences in rates of survival to acorn predation and then on germination or emergence. These results suggest that seed predators influence the spatial patterns of Quercus ilex populations by reshaping the seed shadow within the landscape, mainly by differences among patches. So, the landscape appears to behave as a mixed mosaic with valuable patches for plant recruitment (with low seed predation) intermingled with bad quality patches where the dispersed seeds more often disappear and thus, the recruitment fails.

When Sports Celebrity Doesn'T Perfrom: How Consumers React to Celebrity Endorsement?

Ubiquity of celebrity endorsements has attracted all around attention to make it more effective. This has emerged over the period as a prevalent form of advertising. Majority of celebrities made part and parcel of advertisements are either from cinema and or are the sportspersons. Youths imitate them after coming to know their lifestyles through such advertisements which portray fabulous and thrilling lifestyle of celebrities. They wonder, get fascinated and always think of emulating them. As role models, celebrities are capable to influence many facets of consumer behaviour. By virtue of magnitude and range of their impact on the consumer behaviour, these celebrities are used for multitude of marketing activities which include image building, attention grabbing, persuasion etc. Billions of dollars are committed and spent on such activities. In real life, the performance of sports celebrities may go through good and bad patches. Despite ample research on the impact of negative information concerning celebrity endorsers on consumers, little is known about the impact of poor performance of sports celebrities on the field, on consumers. The present study assesses the impact of poor performance of cricket celebrities on the perception of consumers towards them as a role model through using a pre and post quasi-experimental research design. Additionally, it also gauges the impact of poor performance on behavioural intentions of consumers. The results indicate that the poor performance of sports celebrities on field may dent their standing as a role model but fail to display significant impact of the behavioural intentions. The paper includes the implications for researchers and managers.

Quantifying the Adaptive Value of Learning in Foraging Behavior

The value of acquiring environmental information depends on the costs of collecting it and its utility. Foragers that search for patchily distributed resources may use experiences in previous patches to learn the habitat quality and adjust their behavior. We map the ecological landscape for the evolution of learning under a range of conditions, including both spatial and temporal heterogeneity. We compare the learning strategy with genetically fixed patch-leaving rules and with strategies of foragers that have free and perfect information about their environment. The model reveals that the efficiency of learning is highest when low encounter stochasticity results in reliable estimates of patch quality, when there is no or little temporal change, and when there is little spatial variability. This partially contrasts with the value of learning, which is highest when there is temporal change, because flexible strategies may track the environmental trend, and when there is spatial variability, because there is a need to distinguish between good and bad patches. Learning rules with short-term memory are beneficial when patch information is accurate and when there is temporal change, whereas learning rules that update slowly are generally more robust to spatial variability.

Do Football Teams Have Clusters of Wins, Draws and Defeats?

SummaryThe issue of whether football teams have good or bad patches during the course of a season is of concern to many supporters. This interest can be harnessed to make the classroom teaching of probability more relevant. In this article, the unfamiliar runs test for multiple outcomes is used to test for possible clustering in wins, draws and defeats in a short series of consecutive matches.

Scramble in behaviour and ecology.

Nicholson's distinction between 'scramble' and 'contest' modes of competition has received widespread attention in ecology and in behaviour, though the emphasis has been different between the two disciplines. In ecology the focus has been on the effects on population; in behavioural ecology the focus has been on the consequences at the individual level. This paper reviews and develops a theory of scramble competition at the individual level, deriving a general evolutionarily stable strategy (ESS) for individual scramble expenditure in a patchy habitat in which individuals compete in local groups for available resources, and examines two population consequences. The critical parameter determining the relationship between individual scramble expenditure and the number of competitors in a patch is the expected resource per capita. If resource input, R, to a patch is constant and independent of the number of competitors, n, then as the number of competitors increases, the per-capita resources declines as R/n, and the ESS scramble level declines (in proportion to (n-1)/n2). However, if the resource input to a patch is positively related to the number of competitors in the patch, scramble expenditure may increase with the number of competitors. In the case where the per-capita resource input stays constant (i.e. R(n) = Rn), the scramble level increases with competitor number (in proportion to (n-1) /n). There are plausible ecological reasons why either of these extreme limits may be approached in nature, making it important to ascertain the relationship between R and n before predicting individual scramble expenditure. For example, resource input may be constant when groups of competitors are constrained to remain together in given patches, and constant per-capita resources may be approached when ideal-free foraging rules apply. However, in the latter case, scramble expenditure must be accounted for in determining the ideal-free distribution. An analysis shows that this leads to 'undermatching', i.e. the ratio of numbers of competitors for good/bad patches becomes progressively less than the ratio of input rates for good/bad patches as the difference between the good and bad patches increases. A second population consequence of the scramble ESS relates to the fact that scrambles may dramatically affect fitness. The per-capita gain in energy can be reduced by a factor of up to 1/n as a result of scramble expenditure, potentially reducing realized population size to as little as the square root of the maximum potential carrying capacity, though reasons are given why such large reductions are unlikely.

An Interview with Knopf Editor Ashbel Green

An Interview with Knopf Editor Ashbel Green Interviewen According to Alfred Knopf's own remarks, made in a talk in 1949, Alfred got into the business partly by getting to know good bookstores, including a model pubUsher in England, Martin Seeker. Then he came back to New York and finaUy got a job at Doubleday, Page, and Company, where he was paid eight dollars a week. When Doubleday sent him into the manufacturing department, his connection with books began. He got to correspond with Joseph Conrad, which was a really big thrill to him. He bought Conrad's correspondence from John Quinn and did his first book, partly to help Conrad, who was a lifelong gout sufferer and perpetually hard up. In other words, he became involved in publishing partly through his interest in and caring about authors. Do you think that describes the Knopf vision? Green: We certainly do care about authors, and we care about the quality of their work. Only three people have run this place in eighty-five years. Alfred and Blanche I count as one, and then Robert Gottiieb, and now Sonny Mehta. They are all very different from each other, but they have aU been committed to the care of authors and the quaUty of their work. Interviewen What about the idea that authors and pubUshers ought to be friends? Does that seem like the climate today? Green: Some authors and pubUshers are very much friends, and others are strictly businesslike. Certainly John Updike has been edited by Judith Jones for forty years, and they are very close. Interviewer: This brings up the perennial question about the relationships of editors, and it was one that concerned Knopf, too. Have you ever had to edit a book of fiction that you really, really disliked? The Missouri Review · 137 Green: I don't think Tve ever edited a book of fiction I disliked. I can say that I've edited a book of fiction that disappointed me. It sometimes happens that a writer will write a book that is not up to the level of his previous work. But if you believe in that writer you say all right, he or she's going to do better next time. Interviewer: Knopf believed that you should carry authors through bad patches and bad books. Green: He believed in publishing authors, not books. Although there were and are occasions—especially in nonfiction—where you're pubUshing one-of-a-kind books. Interviewer: At what point is an author important enough to a pubUshing house to be an author that they identify with? In a sense there's a lot of give there; some of these rejections are of books by authors Knopf had previously pubUshed. Green: I don't think in general such a relationship can happen after one book; it may take six books. Interviewer: Knopf's American repubUcation of Green Mansions, by W H. Hudson, was the big book, the early success, that aUowed him to continue. Then, in the '20s, Alfred and Blanche started going abroad every year looking for foreign titles. We notice in reading these reader reports that Knopf republished a lot of work from foreign publishers, particularly Britain. Seeker and Warburg, Heinemann and so forth. Has Knopf done that more than other publishing houses? Green: It's quite possible we did so in the early years. When Alfred and Blanche started this company they found it hard to attract American writers, so they went abroad for much of their list. I think the breakthrough among American writers was when they started to pubUsh Mencken and WUIa Cather in the late '10s, early '20s. Willa Cather left Houghton Mifflin to come to Alfred Knopf because she liked the way he produced and manufactured books. Interviewen He gave a lot of attention to the physical book. He went to Europe every year and looked at different paper for the end papers, etc. Green: He cared about the production values, and we try to continue in that vein. I would say that our list is more American now than it was 138 · The Missouri Review Ashbel Green in the '20s, '30s, '40s. This is essentiaUy...

Designing Algorithm for Nesting Irregular Shapes With and Without Boundary Constraints

Nesting of flat patterns into a given raw sheet has applications in a number of industries. It is in fact a common problem often faced by designers in the shipbuilding and garment manufacturing industries. In addition to a number of constraints peculiar to the specific type of application, the basic goal is to achieve a good layout so that material wastage will be reduced to a minimum. Traditionally, a solution is achieved through the careful manipulation of an experienced designer. This is equivalent to putting together an imperfect jig-saw puzzle which is highly Intuitive and time-consuming. This paper describes the design and development of a nesting algorithm in a step-by-step approach from scratch. Graphics routines are used to describe the shape of a pattern. An approximate-shape routine than replaces the original pattern with a multi-sided polygon. The patterns can be completely different in shape or repetitive in small batches. For repetitive patterns, a pairwise layout is first used to search for a probable good nesting module. Modules are further clustered to form larger modules using a rectangular-packing routine. The program gives an automatic layout solution with variables such as bridge width and stock size controllable by the operator. The program also caters for raw sheet with irregular boundaries and internal bad patches. This feature has further application in leather trimming since leather sheets are highly irregular in profile and are known to contain a large amount of defects such as scars and scratches.

Flash Fire-Valve*

Flash fire-valves are designed to eliminate all danger of serious film fires in projectors during projection caused by broken or tom sprocket-holes, bad patches, worn out mechanism, etc. The operation of the valves makes it impossible for fire in the projector during the process of projection to get into either film magazine, and limits the length of film that can burn in the projector to about 18 inches, or just what is threaded through the mechanism.

On the Pathogenicity of Heterodera schachtii to Potatoes and Mangolds

In 1925, Morgan, in recording field observations on Heterodera schachtii in the Kirton district, pointed out that cysts were frequently as abundant in certain areas of infected fields where the yield was satisfactory, as in “bad patches” where the plants showed every manifestation of eelworm disease, and where the crop was a failure. In a further publication (1926) he again emphasized the lack of correlation between cyst content of the soil and the incidence of “potato-sickness.” One field on which detailed observations were carried out, although the worst case of eelworm infestation examined in the district, was found to give a satisfactory crop—average yield eight tons ware per acre—after only a four year rotation. In summing up these observations, Morgan says: “While it is not suggested that the eelworm had no influence on the yield in this instance, the success of the crop in spite of the pest lends support to the view that the problem is primarily one of obtaining more suitable conditions for plant growth by more judicious manuring and a system of rotation.”

Investigations on Eelworm in Potatoes in South Lincolnshire

The Failure Of the potato crop On some fields in South Lincolnshire has been noted for several years. The stunted growth of the plant, together with the wilting and yellowing of the foliage, usually associated with root trouble, were the symptoms observed, while the yield suffered greatly owing to the small size of the tubers formed. In a few instances the crop over the whole field was so poor that the yield hardly paid for the seed planted; others shewed bad patches which seemed to increase in size year after year.