title: The microbiome of colonial ascidians

authors: Livne Fadlon, Shir

abstract: Colonial ascidians are prolific and successful marine invertebrates worldwide. Colonial ascidians harbour a diverse assemblage of microorganisms, some of which are known to produce secondary metabolites (bioactives) that contribute to the ascidians’ ecological success. However, little is known about the microbial ecology of the putative symbionts associated with colonial ascidians and whether they consistently contribute to host competitiveness. We hypothesise that the colonial ascidian microbiome is host-specific and enables host ecological success in interacting with proximate competitor(s) through chemical competition facilitated by inducible microbially synthesised metabolites. We further theorise that, during invasion events, non-native colonial ascidians outcompete native ones using allelochemical capacities conferred by their microbiome and that nonnative colonial ascidians, which are globally successful invaders, harbour unique microorganism assemblages. 
To examine our hypotheses, it is necessary to characterise the relationship between ascidian ecological status (i.e., native, non-native, monospecific, or interacting) and the ascidian microbiome. We systematically sampled colonial ascidian specimens (both native and non-native species) engaged in competitive interactions as well as monospecific specimens. Microbiome analysis was conducted using 16S rRNA gene PCR amplicon sequencing to characterise baseline variability and identify microbial response patterns linked to the ecological status of host species. 
Our findings revealed a high degree of species-specificity in the ascidian microbiome, and native and non-native species exhibited distinct microbial patterns linked with their ecological state. However, interacting ascidian species did not appear to harbour dominant unique microbial assemblages compared to their monospecific counterparts. We also conducted the first microbiome comparison for zooids and tunics of colonial ascidians and found that, contrary to common assumptions, zooids and tunics generally harbour similar microorganisms. 
This study provides the first systematic characterisation of the colonial ascidian microbiome. We generated statistically informative baselines for the colonial ascidian microbiome and novel insight on its potential roles in mediating host ecology. Findings from this study form a robust foundation for future chemical characterisation of potential bioactive compounds (using the same specimens) and shotgun metagenomic analyses of these unique microbial communities.

text: The microbiome of colonial ascidians Colonial ascidians are prolific and successful marine invertebrates worldwide. Colonial ascidians harbour a diverse assemblage of microorganisms, some of which are known to produce secondary metabolites (bioactives) that contribute to the ascidians’ ecological success. However, little is known about the microbial ecology of the putative symbionts associated with colonial ascidians and whether they consistently contribute to host competitiveness. We hypothesise that the colonial ascidian microbiome is host-specific and enables host ecological success in interacting with proximate competitor(s) through chemical competition facilitated by inducible microbially synthesised metabolites. We further theorise that, during invasion events, non-native colonial ascidians outcompete native ones using allelochemical capacities conferred by their microbiome and that nonnative colonial ascidians, which are globally successful invaders, harbour unique microorganism assemblages. 
To examine our hypotheses, it is necessary to characterise the relationship between ascidian ecological status (i.e., native, non-native, monospecific, or interacting) and the ascidian microbiome. We systematically sampled colonial ascidian specimens (both native and non-native species) engaged in competitive interactions as well as monospecific specimens. Microbiome analysis was conducted using 16S rRNA gene PCR amplicon sequencing to characterise baseline variability and identify microbial response patterns linked to the ecological status of host species. 
Our findings revealed a high degree of species-specificity in the ascidian microbiome, and native and non-native species exhibited distinct microbial patterns linked with their ecological state. However, interacting ascidian species did not appear to harbour dominant unique microbial assemblages compared to their monospecific counterparts. We also conducted the first microbiome comparison for zooids and tunics of colonial ascidians and found that, contrary to common assumptions, zooids and tunics generally harbour similar microorganisms. 
This study provides the first systematic characterisation of the colonial ascidian microbiome. We generated statistically informative baselines for the colonial ascidian microbiome and novel insight on its potential roles in mediating host ecology. Findings from this study form a robust foundation for future chemical characterisation of potential bioactive compounds (using the same specimens) and shotgun metagenomic analyses of these unique microbial communities.

year: 2022

title: On ensemble techniques for data stream regression

authors: Gomes, Heitor Murilo

subjects: Science & Technology

abstract: An ensemble of learners tends to exceed the predictive performance of individual learners. This approach has been explored for both batch and online learning. Ensembles methods applied to data stream classification were thoroughly investigated over the years, while their regression counterparts received less attention in comparison. In this work, we discuss and analyze several techniques for generating, aggregating, and updating ensembles of regressors for evolving data streams. We investigate the impact of different strategies for inducing diversity into the ensemble by randomizing the input data (resampling, random subspaces and random patches). On top of that, we devote particular attention to techniques that adapt the ensemble model in response to concept drifts, including adaptive window approaches, fixed periodical resets and randomly determined windows. Extensive empirical experiments show that simple techniques can obtain similar predictive performance to sophisticated algorithms that rely on reactive adaptation (i.e., concept drift detection and recovery).

text: On ensemble techniques for data stream regression An ensemble of learners tends to exceed the predictive performance of individual learners. This approach has been explored for both batch and online learning. Ensembles methods applied to data stream classification were thoroughly investigated over the years, while their regression counterparts received less attention in comparison. In this work, we discuss and analyze several techniques for generating, aggregating, and updating ensembles of regressors for evolving data streams. We investigate the impact of different strategies for inducing diversity into the ensemble by randomizing the input data (resampling, random subspaces and random patches). On top of that, we devote particular attention to techniques that adapt the ensemble model in response to concept drifts, including adaptive window approaches, fixed periodical resets and randomly determined windows. Extensive empirical experiments show that simple techniques can obtain similar predictive performance to sophisticated algorithms that rely on reactive adaptation (i.e., concept drift detection and recovery).

year: 2020

title: From colonial categories to local culture: Evolving state practices of ethnic enumeration in Oceania, 1965-2014

authors: Kukutai, Tahu

subjects: Social Sciences

abstract: Numerous scholars have examined how governments in particular times and places have classified their populations by ethnicity, but studies that are both cross-national and longitudinal are rare. Using a unique database of census questionnaires, we examine state practices of ethnic enumeration over a 50-year period (1965–2014) in the 24 countries and areas that comprise Oceania. The region’s extraordinary linguistic and cultural diversity, combined with its complex colonial history and indigenous politics, make it an ideal site for comparative analyses. We find a shift from biological conceptions of difference to a more cultural understanding of group identity, exemplified by a sharp rise in language questions and the decline of race-based inquiries. While local identity labels have largely displaced colonial categories, the imprimatur of previous regimes still lingers, particularly in Melanesia. These shifts in official constructions of ethnoracial differences reflect a gradual lessening of colonial influences on demographic practices.

text: From colonial categories to local culture: Evolving state practices of ethnic enumeration in Oceania, 1965-2014 Numerous scholars have examined how governments in particular times and places have classified their populations by ethnicity, but studies that are both cross-national and longitudinal are rare. Using a unique database of census questionnaires, we examine state practices of ethnic enumeration over a 50-year period (1965–2014) in the 24 countries and areas that comprise Oceania. The region’s extraordinary linguistic and cultural diversity, combined with its complex colonial history and indigenous politics, make it an ideal site for comparative analyses. We find a shift from biological conceptions of difference to a more cultural understanding of group identity, exemplified by a sharp rise in language questions and the decline of race-based inquiries. While local identity labels have largely displaced colonial categories, the imprimatur of previous regimes still lingers, particularly in Melanesia. These shifts in official constructions of ethnoracial differences reflect a gradual lessening of colonial influences on demographic practices.

year: 2016