Differential temporal beta‐diversity patterns of native and non‐native arthropod species in a fragmented native forest landscape

An important factor that hinders the management of non‐native species is a general lack of information regarding the biogeography of non‐natives, and, in particular, their rates of turnover. Here, we address this research gap by analysing differences in temporal beta‐diversity (using both pairwise and multiple‐time dissimilarity metrics) between native and non‐native species, using a novel time‐series dataset of arthropods sampled in native forest fragments in the Azores. We use a null model approach to determine whether temporal beta‐diversity was due to deterministic processes or stochastic colonisation and extinction events, and linear modelling selection to assess the factors driving variation in temporal beta‐diversity between plots. In accordance with our predictions, we found that the temporal beta‐diversity was much greater for non‐native species than for native species, and the null model analyses indicated that the turnover of non‐native species was due to stochastic events. No predictor variables were found to explain the turnover of native or non‐native species. We attribute the greater turnover of non‐native species to source‐sink processes and the close proximity of anthropogenic habitats to the fragmented native forest plots sampled in our study. Thus, our findings point to ways in which the study of turnover can be adapted for future applications in habitat island systems. The implications of this for biodiversity conservation and management are significant. The high rate of stochastic turnover of non‐native species indicates that attempts to simply reduce the populations of non‐native species in situ within native habitats may not be successful. A more efficient management strategy would be to interrupt source‐sink dynamics by improving the harsh boundaries between native and adjacent anthropogenic habitats.Portuguese FCT‐NETBIOME – ISLANDBIODIV grant 0003/2011.info:eu-repo/semantics/publishedVersio

Patterns of transition. Female native Dutch and ethnic minority employment patterns in the Dutch labour market, 1991 and 2002

This study analyses female native Dutch and ethnic minority employment patterns in the Dutch labour market. Focusing on life-course employment patterns, it aims to find out if native Dutch and ethnic minority women in the Netherlands have undergone a transition towards more labour market participation between 1991 and 2002. Three patterns of change in employment integration by age can be discerned. First, increasing employment levels for native Dutch women of almost all age groups, but in particular for those age groups that have to combine employment with rearing children. Second, a high employment level for Surinamese and Antillean women, revealing strong employment integration of all age groups, so that combining market work and rearing children does not hamper labour market integration. Third, a more traditional pattern for Turkish and Moroccan women, yet indicating an increased employment rate for almost all age groups, in particular 20-24 years. We find that critical life events such as motherhood have different effects on employment for Mediterranean, Caribbean and native Dutch women. In addition, the analysis shows that the attachment of both native Dutch and ethnic minority women to the labour market becomes stronger, and the influence of motherhood becomes smaller, over time. All in all, Caribbean women are the most attached to the labour market. © 2006 Taylor & Francis

Eco-Defense against Invasions

Characterizing patterns of invasion across space, time, and taxonomic group will help reveal how invasive species affect ecosystem function and individual native specie

Oscillator neural network model with distributed native frequencies

We study associative memory of an oscillator neural network with distributed native frequencies. The model is based on the use of the Hebb learning rule with random patterns ($\xi_i^{\mu}=\pm 1$), and the distribution function of native frequencies is assumed to be symmetric with respect to its average. Although the system with an extensive number of stored patterns is not allowed to get entirely synchronized, long time behaviors of the macroscopic order parameters describing partial synchronization phenomena can be obtained by discarding the contribution from the desynchronized part of the system. The oscillator network is shown to work as associative memory accompanied by synchronized oscillations. A phase diagram representing properties of memory retrieval is presented in terms of the parameters characterizing the native frequency distribution. Our analytical calculations based on the self-consistent signal-to-noise analysis are shown to be in excellent agreement with numerical simulations, confirming the validity of our theoretical treatment.Comment: 9 pages, revtex, 6 postscript figures, to be published in J. Phys.

Environmental effects related to the local absence of exotic fish

Given the extent of biological invasions in industrialized countries, our understanding of the determinants of overall patterns of biological invasions could gain most from consideration of why exotic species are absent from some areas, rather than from distribution patterns of exotic species. Fish communities were sampled at 381 sites representing 221 rivers in the Adour-Garonne stream system (116 000 km², SW France). Very few rivers were not colonized by exotic fish species, however, on a local basis, only 33% of the sampling sites hosted exotics. Using General Linear Modelling, we found that patterns of exotic fish (occurrence, number of species, proportion within assemblage) responded to both land-use and physical variables, whereas patterns of native fish only responded to the local meso-scale characteristics of each stream reach from headwaters to mouth. All fish communities were susceptible to invasion regardless of native species richness, and higher native species richness did not decrease the opportunity for establishment by exotic species. The likelihood that exotic fish are absent primarily increased with elevation and with lower human influence upon the land cover, while human-impacted landscapes (agricultural and urban areas) were more likely to host exotic fish and higher numbers of exotic species. In light of urban and agricultural development, our ability to detect responses of exotic species to landscape alterations using a combination of simple physical and land cover variables exemplifies a cost-effective technique for assessing areas at greater invasion risk in large stream systems

Geographical, socioeconomic, and ecological determinants of exotic plant naturalization in the United States : insights and updates from improved data

Previous studies on alien species establishment in the United States and around the world have drastically improved our understanding of the patterns of species naturalization, biological invasions, and underlying mechanisms. Meanwhile, relevant new data have been added and the data quality has significantly increased along with the consistency of related concepts and terminology that are being developed. Here using new and/or improved data on the native and exotic plant richness and many socioeconomic and physical variables at the state level in the United States, we attempt to test whether previously discovered patterns still hold, particularly how native and exotic species are related and what are the dominant factors controlling the plant naturalization. We found that, while the number of native species is largely controlled by natural factors such as area and temperature, exotic species and exotic fraction are predominantly influenced by social factors such as human population. When domestically introduced species were included, several aspects in earlier findings were somewhat altered and additional insights regarding the mechanisms of naturalization could be achieved. With increased data availability, however, a greater challenge ahead appears to be how many and which variables to include in analyses

Language proficiency among immigrants and the establishment of interethnic relations: a comparative analysis of Bilbao, Lisbon and Rotterdam

Despite the increasing interest in exploring language proficiency among immigrants as a quintessential element for their economic integration in the host country, less attention has been devoted to the social impacts that destination-language proficiency may have on enhancing interethnic contacts between immigrants and the native population. This research aims to shed light on this latter topic, discussing if being a native-speaker immigrant in the host country or, for those immigrants who are non-native speakers, having a stronger command of the destination-language may increase their likelihood of interacting with the native population. Moreover, we question if there are significant differences in the interaction patterns between these two groups and the natives, presenting the cities of Bilbao, Lisbon and Rotterdam as a territorial frame. The analysis is based on data gathered through the GEITONIES survey. The results obtained indicate that native-speaker immigrants generally tend to show more interaction with the natives. Nevertheless, for immigrants not sharing such cultural similarity, those with a higher level of second-language proficiency clearly show stronger bonds with the native population; in both cases this can also be related to individual, group or place related variables

Metadiscourse repertoire of L1 Mandarin undergraduates writing in English : a cross-contextual, cross-disciplinary study

This article presents a qualitative, comparative study of metadiscourse in the academic writing of two groups of undergraduate students working in two different disciplines. The groups of students were: 1) Native speakers of Mandarin studying in China through the medium of English; 2) Native speakers of Mandarin studying in the UK through the medium of English. For each group of students, we examined writing undertaken in two undergraduate disciplinary courses: Literary Criticism and Translation Studies. Our aim was to extend research into English writing by L1 Mandarin speakers, and to identify patterns of difference and similarity both between educational contexts and between disciplines. Results suggest that patterns of metadiscourse use in our corpus are associated with both disciplinary and contextual factors, but that contextual factors may have a stronger effect than disciplinary factors. For our data, local institutional culture seems to have a noticeable influence on student writers' use of metadiscourse

Immigrant-Native Fertility and Mortality Differentials in the United States

Immigrants have been discussed as a means of alleviating fiscal pressures on Social Security. Their long-term impact on the Social Security system depends critically on their fertility and mortality patterns. In this paper, we examine the fertility and mortality patterns of immigrants to the United States and compare these patterns with those of non-immigrants. We find that both the recent and cumulative fertility of immigrant women is higher than that of native-born women, but that a large share of these differentials can be “explained” by differences in age structures, race and ethnicity, years in the United States, and country of origin. Using a synthetic cohort approach, we examine the role of years in the United States in more detail, and find no evidence of assimilation towards native-born fertility patterns. Consistent with previous research, we find evidence of a disruption effect on fertility – the fertility of immigrant women in the most recent arrival cohorts is low, but increases at a faster rate relative to both the fertility of immigrants from earlier cohorts and relative to the fertility of natives. We find that immigrants experience lower mortality than native-born individuals in the United States, and these differences remain even after controlling for underlying differences in observable characteristics. However we find that they do not exhibit differences in their subjective expectations of their mortality.

A hypothesis on improving foreign accents by optimizing variability in vocal learning brain circuits

Rapid vocal motor learning is observed when acquiring a language in early childhood, or learning to speak another language later in life. Accurate pronunciation is one of the hardest things for late learners to master and they are almost always left with a non-native accent. Here I propose a novel hypothesis that this accent could be improved by optimizing variability in vocal learning brain circuits during learning. Much of the neurobiology of human vocal motor learning has been inferred from studies on songbirds. Jarvis (2004) proposed the hypothesis that as in songbirds there are two pathways in humans: one for learning speech (the striatal vocal learning pathway), and one for production of previously learnt speech (the motor pathway). Learning new motor sequences necessary for accurate non-native pronunciation is challenging and I argue that in late learners of a foreign language the vocal learning pathway becomes inactive prematurely. The motor pathway is engaged once again and learners maintain their original native motor patterns for producing speech, resulting in speaking with a foreign accent. Further, I argue that variability in neural activity within vocal motor circuitry generates vocal variability that supports accurate non-native pronunciation. Recent theoretical and experimental work on motor learning suggests that variability in the motor movement is necessary for the development of expertise. I propose that there is little trial-by-trial variability when using the motor pathway. When using the vocal learning pathway variability gradually increases, reflecting an exploratory phase in which learners try out different ways of pronouncing words, before decreasing and stabilizing once the ‘best’ performance has been identified. The hypothesis proposed here could be tested using behavioral interventions that optimize variability and engage the vocal learning pathway for longer, with the prediction that this would allow learners to develop new motor patterns that result in more native-like pronunciation