Analysis of spatial association between two species based on the interspecies mean crowding

Summary and Conclusion The measurement of spatial association between two species is considered on the basis of interspecies mean crowding. Two indices of overlapping, γ andC _p, are derived as geometric and weighted arithmetic means of the same component ratios related to inter-and intraspecies mean crowdings. Both indices behave in a similar way, ranging from 1 when the distributions of two species are completely overlapped to 0 when they are completely exclusive with each other. The former is essentially identical with indices proposed byKuno (1968) andPianka (1973), and the latter is a modified form ofMorisita's (1959)C _σ index. Indices to measure the degree of spatial correlation between species, Ω andR _μ, are then derived for both kinds of overlapping indices, which vary from 1 in complete overlapping, through 0 in independent occurrence, to −1 in complete exclusion. Various kinds of interspecies association are analyzed using these indices and an extended form of the regression graph which provides a convenient way of indicating the spatial interrelation between two species as well as distribution patterns of respective species. The method presented in this paper may also be applicable to compare temporal distribution patterns between species, similarity between communities, etc. For such a wider application which includes continuous as well as discrete distributions, the interpretation of intra-and interspecies mean crowdings is not necessarily appropriate, and hence the concept of mean concentration with the symbols and for intraspecies relation and and for interspecies relation is suggested. This study was supported by Science Research Fund (No. 148041) from the Ministry of Education.     

The importance of non-linearity: A comment on the views of Taylor

Summary Taylor's (1984) view that his power law is better measurement of the distribution pattern of animals than 1/k, I _ρ and relation because almost all the data on means and variances of given species could be fitted by the power low, was critisized. Changes in values of 1/k, I _ρ and suggest the change of distribution pattern of the species, but the data can still be fitted by the power law because of the great linearizing power of log-log plots, and, using the power law only, we shall overlook the information on the meaningful changes in the distribution pattern.     

Overwintering ecology of two social halictine bees,Lasioglossum duplex andL. problematicum

Summary Overwintering of two social halictine bees,Lasioglossum duplex (Dalla Torre) andL. problematicum (Blüthgen), was studied. InL. duplex many females stay near the old nests, each female preparing a hibernaculum separated from the natal nest. InL. problematicum most females overwinter communally within the natal nest. This difference in overwintering habits relates to the social structure in the next spring.L. duplex is nearly always solitary in spring although later becoming eusocial, whereas many nests ofL. problematicum are polygynous, beginning in early spring.L. duplex overwinters much deeper ( ) in the soil than doesL. problematicum ( ), but both species are safe from drops in soil temperature, which is above 0°C even in midwinter, and the bees' supercooling points are lower than −6°C. This cold resistance and the storage of sufficient food in the crop are reflected in the winter survival, which is much higher (79%) than the rate of successful nests in the spring active phase (25%). Bionomics of the eusocial halictine beeLasioglossum duplex VII. Contribution No. 2654 from the Inst. Low Temp. Sci.     

Mortality process in relation to aggregation in the southern green stink bug

Summary A simple experiment of simulation was done to analyze the natural mortality process of young larval colonies and egg masses of the southern green stink bug. In this experiment, a degree of contagiousness was allowed in regard to the action of a mortality factor, and was defined as the mean number killed per a colony or an egg mass by the mortality factor within a unit time and the number killed per a colony was assumed to follow the Poisson series with the mean . Thus each component of the Poisson series was opposed to each colony or egg mass which was taken at random from 162 egg masses, 135 and 117 colonies of the first and the second instar larvae, respectively. It was revealed that mortality factors in the field did not act with a small degree of contagiosness, e. g. , on all colonies or egg masses, but acted with a large degree of contagiousness, e. g. , on some of the colonies or egg masses. Thus differential survival somewhat in all or none way occurred among the insect colonies irrespective of their initial sizes. These results were well explained by taking actual mortality factors into account.     

Studies on the distribution pattern of the pine needle gall midge,Thecodiplosis japonensisUchida etInouye (Diptera: Cecidomyiidae) in a pine forest

Summary Numerical changes and distribution patterns of the pine needle gall midge,Thecodiplosis japonensis Uchida etInouye, were studied during the period from 1978 to 1979 in a young plantation ofPinus thunbergii in Shiga Prefecture, Japan. The survivorship curve of this species was characterized by a low mortality of larvae in galls and two high mortalities before the formation of galls and during the overwintering period in soil. The within and between-trees distributions of eggs and larvae in galls were examined by using the regression method. The egg distribution per shoot was aggregative both within and between host plants. The within-tree variations in numbers of eggs per shoot were related to the differences in the abundance of available needles for oviposition per shoot among the canopy layers. The between-tree variations reflected the heterogeneous emergence of adult females in the study plot. The degree of aggregation increased from egg to gall stage in both within- and between-tree distributions and the increase was explained by the different mortality of larvae within trees and the inversely density-dependent mortality between trees. The distribution patterns in the soil habitat stages were examined by the patchness index ( ). This species showed aggregative distributions in soil stages. There was a correlation in spatial patterns of adult emergence between the successive generations. The distribution properties of this species were discussed in connection with the population dynamics and the availability of host plants in the study plot.     

An index of spatial distribution

Summary The index , which takes the value of −1 for a perfectly regular distribution, +1 for a highly aggregated distribution and 0 for the distribution implied by the theoretical varianceσ ², is proposed and a significance table provided.     

A new method of sequential sampling to classify populations relative to a critical density

Summary A method of sequential sampling for grading population level in relation to a critical density is proposed. The method is based on the relationship and can be used without restrictions on the distribution patterns. The formulae for simple random sampling as well as for two-stage sampling are given. This research was suported by science research fund from the Ministry of Education.     

The spatial distribution pattern of the brown planthopperNilaparvata lugens St?l (Homoptera: Delphacidae) in west Java, Indonesia

Summary Spatial distribution pattern of the brown planthopper (BPH) was analyzed at 9 experimental fields in the northern part of West Java during two consecutive rice cropping seasons, i.e., wet and dry seasons. The population of each developmental stage and wing form of BPH at each location showed consistent departure from the random (Poisson) distribution, the variances of the densities in most cases exceeding their means. Namely, the distribution pattern of BPH per hill of rice plant was found to have a general tendency to be aggregated or contagious and to fit fairly well to the negative binomial model. The tendency for aggregation was further confirmed by both the β-values of -m regression being larger than unity and theC _A -values being larger than zero for each developmental stage. Although significant variations in the distribution pattern as measured by β- orC _A -value were observed between different developmental stages, between wing forms and among locations, the degree of aggregation for a given developmental stage at each experimental field remained fairly stable throughout the crop period, despite wide temporal changes in population density. Possible factors to explain these characteristics of the spatial distribution pattern of the BPH in West Java were discussed with reference to the process generating it.     

A field study of the effect of prebaiting on censusing by the capture-recapture method in a vole population

Summary Populations of the vole,Clethrionomys rufocanus, in a lowland woodlot of Hokkaido were studied for the presence of effects of prebaiting on censusing by the capture-recapture method. A grid of 121 live-traps, spaced 5 m apart, was laid out on each of two plots, one of which alone was prebaited three days long. Owing to very high densities and great trap-efficiency, sufficient and favourable samples could be available for statistical analysis, except the trend of delayed catch for young in sampling. The population on either plot, however, proved to be markedly variable in catchability of unmarked animals in the course of trapping; while the probability of recapture was counted as invariable on the average from day to day, the recapture frequency was different between juveniles, subadults and adults. Needless to say, the catchability was distinctly greater for marked voles than for unmarked ones, whether prebaited or not, through the trapping period, except that the first-day catchability for unmarked ones on the prebaited plot seems not to be significantly lower than that for marked ones. Consequently, it turns out that the prebaiting has almost never helped to eliminate the important bias induced by differential trap-response of marked and unmarked animals; its contribution is only that the catchability for unmarked ones is slightly higher on the part of the prebaited plot on earlier days of the period. In accordance with the heterogeneous catchability, the Γ-form distribution analogous to the geometric could be applied with thorough fitness to the capture frequency in order to estimate the whole populations. The fact that the estimates are reliable, being not at any rate underestimates, was further confirmed by the result of a follow-up work conducted by means of the removal method with wider trap-spacing which brought forth distinct underestimation chiefly referable to unexposure to traps of the partial populations. The subject of unexposure was discussed by laying stress on the relation between minimum range length and trap-spacing. Contribution from JIBP-PT No. 88, carried out by the grant from the expenditure of Education Department to the specific study on “Dynamics of Biosphere”.     

Too many migrants, too few services: a model of decision-making on immigration and integration with cultural distance

We model the political demand for immigrants as a trade-off that native voters face between having services, assumed to be produced only by unskilled and nonassimilated immigrants, and experiencing disutility due to the immigrant workers having a culture different from the native culture. Immigrants decide whether to integrate into the native culture. We show that if services are priced according to per unit costs, the market demand for immigrants will exceed the political demand. Market forces then lead to higher services prices, implying that the initially allowed number of immigrants is ‘politically’ too large.

The dynamics of immigrant welfare and labor market behavior

This paper analyzes transitions into and out of social assistance, unemployment, and employment. We estimate a dynamic multinomial logit model, controlling for endogenous initial condition and unobserved heterogeneity, using a large representative Swedish panel data set. The empirical results suggest that particularly refugee immigrants display a greater degree of “structural” state dependence than natives. The high welfare participation rates among refugee immigrants may be due to the existence of a “welfare trap”, while participation among natives and non-refugee immigrants is largely due to permanent unobserved characteristics. These results suggest that welfare reforms may have differential effects on refugee immigrants and natives.

Housing Adjustment Among Immigrants in Israel: Application of Complementary Non-Metric and Metric Techniques

This study applies two different complementary statistical techniques to examine the structure and determinants of homeownership and consumption of household goods among immigrants in Israel. Findings from partial-order analysis (POSAC) reveal significant differences between immigrant groups by type, rather than level, of household characteristics. Suppliers of entertainment (television) and of information-communication (computer) are the items that most strongly distinguish between immigrants. The joint direction of the partially ordered space corresponds with home and car ownership. Immigrant groups are dispersed in different parts of the household typology; with increased duration of residence in Israel immigrants move, albeit in varied rhythms, toward improved housing conditions. A complementary logistic regression analysis, which controls for socio-demographic variation and detailed tenure in Israel, show a likelihood of convergence of immigrants from all origin countries with the core native-born group in owning a home. For other household goods, the findings largely coincide with the typology derived from POSAC. The findings are discussed in reference to three conceptual expectations of “cultural norms”, “adjustment”, and “structural-environmental considerations”.

The Place of Place: Location and Immigrant Economic Well-being in Canada

In recent years, successive cohorts of immigrants to Canada have experienced a striking level of deterioration in their economic well-being. At the same time, more immigrants than ever before are choosing to live in Montréal, Toronto, or Vancouver, Canada’s three-first-tier or ‘gateway cities’. This paper uses instrumental variable regression techniques to determine the extent to which gateway city clustering is related to immigrant economic well-being. It identifies whether employment status, earnings, and employment suitability would significantly improve if more immigrants chose to live outside of Canada’s three gateway cities. The results suggest that, for the most part, although immigrants do worse than the native-born in gateway cities, they do experience marginally higher earnings than their non-gateway counterparts. Income and unemployment rates are higher for immigrants in gateway cities than they are for the native-born, but the gateway/non-gateway disparity is minimal. Levels of employment mismatch are substantially higher in gateway cities, compared to both the gateway city native-born population, and non-gateway immigrants. An analysis of the data shows that only marginal improvements to economic well-being would result from an increase in non-gateway immigration, and that there are other factors, like race or skin colour, that seem to be more closely linked to labour market success.

Analysis of contagiousness in the action of mortality factors on the western tent caterpillar population by using the \mathop m* - m\mathop m\limits^* - m relationshiprelationship

Summary The contagiousness in the operation of mortality processes on the colonies of the western tent caterpillar,Malacosoma californicum pluviale, was analyzed from two different aspects: successive changes in the frequency distribution of the number of surviving individuals per colony in the course of development, and the distribution pattern of the individuals killed by some biotic mortality factors. Also, for a tachinid parasite,Tachinomyia similis, the analysis was made on the egg-laying pattern on colonies as well as on individual larvae. The methods of these analyses were all based on the relation of mean crowding (m) on mean . A braconid parasite,Rogas sp., tended to kill few individuals together once it attacked a colony, but its effect on host colonies was rather equivalent to the random removal of individuals from all the colonies. Diseases in the late-stage larvae before cocooning was contagious in their action. Nuclear polyhedrosis virus seemed to have no basic contagiousness in its action, but it caused highly contagious distribution of deaths among the colonies when its average incidence was high. A spore-formingBacillus had a tendency to kill several individuals once it appeared in a colony, but the distribution of its incidence (no. of times it appeared per colony) was considered to be nearly at random. The female ofTachinomyia tended to lay more than one egg successively on the same colony. It also attacked individual larvae with a definite tendency for aggregation, which seemed to be resulted from the parasite’s preference to large hosts. When the number of eggs laid on prefered hosts exceeded a certain threshold, however, the fly seemed to change its attention to less attractive, smaller individuals.     

A distance measure of spatial pattern in a biological population

Summary Suppose thatn individuals locate independently and randomly on a segment of line of finite length (habitat). Let the theoretical and observed ranges of the sites of the individuals on the segment be μ _n-1 andr _n-1, respectively. Then, the degree of dispersion of the individual sites is measured by the ratio, T _n =n _n-1/μ _n-1, as follows: A random spatial pattern forI _r−1 =1 An aggregated spatial pattern for 0≤I _r <1 A uniform spatial pattern for (n+1)/(n−1)≥I _r >1. Another method was derived. Let the probability that an observed range is less thanr _n−1 beI _p , under the hypothesis of a Beta distribution. Then indicates A random spatial pattern forI _p =1/2 An aggregated spatial pattern forI _p <1/2 A uniform spatial pattern forI _p >1/2. The first index can be used for comparing populations having the same number of individuals, whereas the second one can be used for comparing populations with different numbers of individuals.     

Ecological studies of collembolan populations in a pine forest soil IV. Comparison of distribution patterns

Summary The distribution pattern of ten species of Collembola was studied during the four years period from July 1971 to May 1975 in a pine forest soil. The distribution patterns were analysed for two scales of distribution, i. e., the distribution over the plot of 10×10 m² and the micro-distribution within a block sample consisting of 36 contigious units each 2×2 cm² in area, by applying the -m regression method. The fundamental pattern which appeared was quite similar for the species examined and individuals were aggregated in response to the heterogeneity of habitat conditions. The causes of aggregations were discussed with regard to some environmental factors. The relative abundances of 10 species within the collembolan community was examined in relation to the habitat utilization and the relative abundance was not related to the degree of aggregation but rather to the area occupied by individuals. This suggests that the more numerically abundant species tend to occupy broader micro-habitat. Biological meaning of aggregation was discussed in connection with the population biology and community organization of collembola.     

Inquiry into effects of prebaiting on removal census in a vole population

Summary A field work with two plots of grid, a snap trap being set on each station spaced 5 m apart, was executed in the summer of 1968 to evaluate prebaiting in census trapping by comparing the result in one plot, prebaited for three days, with that in the other not prebaited. Since the population was as high as some 230 per acre on the average in density and formed of the vole,Microtus montebelli, alone, sufficient samples were gathered irrespective of the plot size as small as 50×50 m. Owning to the circumstances, multiple collisions inflicted so intense influence on sampling especially in the prebaited plot thatz-equation for census adjusted to the effect was well applicable to the data in either plot. In sampling, the fact that small voles are apt to be caught later than large voles was statistically evidenced in either sex, and yet any proof that males tend to be caught prior to females was not offered. It was ascertained in either plot that the daily catch was realized according to the same rule through the whole period of trapping in both external belt and internal square within the plot; hence it follows that no considerable immigration occurred. One of the beneficial effects of prebaiting is sure to be that the probability of capture was markedly enhanced in the prebaited plot, and a second is supposed, though inconclusively, to be that a good sampling could be executed consistently through the census period giving rise to no inordinate catches perhaps due to heterogeneous sampling as was seen in earlier days in the not prebaited plot. The supposition has derived from the condition that most of the whole population is trappable, which is established by interrelation among population density, size of home range and trap spacing. It was suggested that the effect of prebaiting should be evaluated from the view-point of the interrelation, because the basic utility of prebaiting consists in that it may help to our utlimate purpose to estimate the whole population. Contribution from JIBP-PT No. 55, carried out by the grant from the expenditure of Education Department to the specific study on “Dynamics of Biosphere”     

The educational attainment of second-generation mainland Chinese immigrants in Taiwan

The social status and well-being of political immigrants’ children are seldom touched upon in literature. This paper focuses on the impact of refugee experience on the relative educational attainment of second-generation immigrants in Taiwan. In contrast with the results in van Ours and Veenman (J Popul Econ 16(4):739–753, 2003) and Riphahn (J Popul Econ 16(4):711–737, 2003) who showed that second-generation immigrants lag behind their native counterparts, this paper’s principle finding is that the father’s immigration status can help his children achieve a higher educational qualification than native Taiwanese after controlling the relevant determinants of educational attainment, including parental background and the neighborhood where the interviewee grows up. In addition, women born in the earlier cohort benefit more by their fathers’ immigration status than their male counterparts do. However, Taiwanese schooling advances across generations are impressive, whereby the gap in schooling attainment between second-generation immigrants and native Taiwanese is found to decline over time.

Labor market transitions of immigrants with emphasis on marginalization and self-employment

In developed countries, immigrants are more likely to be nonemployed and self-employed compared to natives. Based on register data of male immigrants in Denmark, we performed a detailed investigation of the immigrant–native difference in transition patterns across labor market states. We find that a high proportion of immigrants from non-Western countries tend to be marginalized relative to natives, and they tend to use self-employment to escape marginalization.

Are there gender and country of origin differences in immigrant labor market outcomes across European destinations?

The 1994–2000 waves of the European Community Household Panel are used to study the earnings of immigrants as compared to native workers in 15 European countries. At the time of arrival, there is a significant negative partial effect of foreign birth on individual earnings compared to the native born in the destination of around 40%. These differences vary across origins and destinations and by gender. Immigrant earnings catch-up to those of the native born after around 18 years in the destination. Schooling matters more for earnings for women, whereas, language skills are relatively more important for men.