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Featured researches published by Gary M. Barker.


Ecological Monographs | 2001

INTRODUCED BROWSING MAMMALS IN NEW ZEALAND NATURAL FORESTS: ABOVEGROUND AND BELOWGROUND CONSEQUENCES

David A. Wardle; Gary M. Barker; G. W. Yeates; Karen I. Bonner; Anwar Ghani

Forest dwelling browsing mammals, notably feral goats and deer, have been introduced to New Zealand over the past 220 years; prior to this such mammals were absent from New Zealand. The New Zealand forested landscape, therefore, presents an almost unique opportunity to determine the impacts of introduction of an entire functional group of alien animals to a habitat from which that group was previously absent. We sampled 30 long-term fenced exclosure plots in indigenous forests throughout New Zealand to evaluate community- and ecosystem-level impacts of introduced browsing mammals, emphasizing the decomposer subsystem. Browsing mammals often significantly altered plant community composition, reducing palatable broad-leaved species and promoting other less palatable types. Vegetation density in the browse layer was also usually reduced. Although there were some small but statis- tically significant effects of browsing on some measures of soil quality across the 30 locations, there were no consistent effects on components of the soil microfood web (com- prising microflora and nematodes, and spanning three consumer trophic levels); while there were clear multitrophic effects of browsing on this food web for several locations, com- parable numbers of locations showed stimulation and inhibition of biomasses or populations of food web components. In contrast, all microarthropod and macrofaunal groups were consistently adversely affected by browsing, irrespective of trophic position. Across the 30 locations, the magnitude of response of the dominant soil biotic groups to browsing mammals (and hence their resistance to browsers) was not correlated with the magnitude of vegetation response to browsing but was often strongly related to a range of other variables, including macroclimatic, soil nutrient, and tree stand properties. There were often strong significant effects of browsing mammals on species composition of the plant community, species composition of leaf litter in the litter layer, and composition of various litter-dwelling faunal groups. Across the 30 locations, the magnitude of browsing mammal effects on faunal community composition was often correlated with browser effects on litter layer leaf species composition but never with browser effects on plant community composition. Browsing mammals usually reduced browse layer plant diversity and often also altered habitat diversity in the litter layer and diversity of various soil faunal groups. Across the 30 locations, the magnitude of browser effects on diversity of only one faunal group, humus-dwelling nematodes, was correlated with browser effects on plant diversity. However, browser effects on diversity of diplopods and gastropods were correlated with browser effects on habitat diversity of the litter layer. Reasons for the lack of unidirectional relationships across locations between effects of browsers on vegetation community attri- butes and on soil invertebrate community attributes are discussed. Browsing mammals generally did not have strong effects on C mineralization but did significantly influence soil C and N storage on an areal basis for several locations. However the direction of these effects was idiosyncratic and presumably reflects different mechanisms by which browsers affect soil processes. While our study did not support hypotheses predicting consistent negative effects of browsing mammals on the decomposer subsystem through promotion of plant species with poorer litter quality, our results still show that the introduction of these mammals to New Zealand has caused far-ranging effects at both the community and ecosystem levels of resolution, with particularly adverse effects for indigenous plant com- munities and populations of most groups of litter-dwelling mesofauna and macrofauna.


The biology of terrestrial molluscs. | 2001

The biology of terrestrial molluscs

Gary M. Barker

1: Morphology, phylogeny and systematics, G M Barker, Landcare Research, New Zealand 2: Body wall: form and function, D L Luchtel and I Deyrup-Olsen University of Washington, USA 3: Sensory organs and the nervous system, R Chase, McGill University, Canada 4: Radular structure and function, U Mackenstedt, Universitat Hohenheim, Germany and K Markel, Ruhr-Universitat Bocham, Germany 5: Structure and function of the digestive tract, V K Dimitriadis, Aristotle University of Thessaloniki, Greece 6: Food and feeding behaviour, B Speiser, Research Institute of Organic Agriulcture (FiBL), Switzerland 7: Haemolymph: blood cell morphology and function, E Furuta and K Yamaguchi, Dokkyo University School of Medicine, Japan 8: Structure and functioning of the reproductive system, B Gomez, Universidad del Pais Vasco, Spain Regulation of growth and reproduction, A Gomot de Vaufleury, Universte de Fanche-Comte, France 9: Spermiogenesis and oogenesis, J M Healy, The University of Queensland, Australia 10: Population and conservation genetics, T Backeljau, Royal Belgian Institute of Natural Sciences, Belgium, A Baur and B Baur, University of Basel, Switzerland 11: Life history strategies, J Heller, The Hebrew University, Israel 12: Behavioural ecology: on doing the right thing in the right place at the right time, A Cook, University of Ulster, UK 13: Soil biology and ecotoxicology, R Dallinger and B Berger, Universitat Innsbruck, Austria, R Triebskorn-Koehler and H Koehler, Universitat Tubingen, Germany


Molluscs as crop pests. | 2002

Molluscs as crop pests.

Gary M. Barker

Toxocology of chemicals deployment of molluscicides in baits specific crop situations from around the world synopsis of the current pest status of mollusc species or species groups and progress towards development of solutions.


Natural enemies of terrestrial molluscs. | 2004

Natural enemies of terrestrial molluscs

Gary M. Barker

Avian, mammalian and reptilian predators coleopteran, heteropteran predators and aranae gastropods, nematodes and mites as natural enemies sciomyzidae, phoridae and sacrophagidae ciliophora and microsporidia as parasites of mollusca bacterial and non-microbial diseases.


Oikos | 1997

Competition and Herbivory in Establishing Grassland Communities: Implications for Plant Biomass, Species Diversity and Soil Microbial Activity

David A. Wardle; Gary M. Barker

The two main biotic factors affecting grassland plant species are herbivory and competition. We investigated the significance of both these factors in establishing grassland communities through manipulation experiments conducted in both winter and summer in glasshouse conditions. Manipulations consisted of addition of above-ground and below-ground herbivores, reduction of herbivory through use of an insecticide, and varying of competitive pressure by removing either dicotyledonous or monocotyledonous seedlings as they appeared. In the winter experiment, the total biomass of dicotyledonous plants was reduced by both above-ground and below-ground herbivory, while monocotyledonous plant biomass was unaffected. However, in the summer experiment, only those treatments in which competition was manipulated had any detectable effect. This suggests that the relative importance of competition and herbivory can vary considerably. The above-ground herbivory treatment sometimes stimulated and sometimes reduced plant species diversity, and sometimes also induced significantly higher dicotyledonous species diversity than the root herbivory treatment. Those treatments in which competitive pressure was manipulated had no detectable effects on diversity. There were many strong effects detected when plant species were considered individually, with different species responding to different treatments, and with all treatments affecting at least some species. Different species therefore respond quite differently to competition and herbivory. None of the treatments affected soil microbial activity or active soil microbial biomass in the winter experiment, although active biomass was significantly positively correlated with dicotyledonous plant biomass. In the summer experiment, soil activity was positively affected by monocotyledonous plants, while active biomass was the same in all treatments except for the treatment with all plants removed, where biomass was less. None of the soil biotic variables showed any relationship with plant species richness. Our study shows that competition and herbivory can both exert important influences at both the community and ecosystem levels of resolution.


PLOS ONE | 2015

Risk factors for men's lifetime perpetration of physical violence against intimate partners: results from the international men and gender equality survey (IMAGES) in eight countries.

Paul J. Fleming; Jennifer McCleary-Sills; Matthew Morton; Ruti Levtov; Brian Heilman; Gary M. Barker

This paper examines men’s lifetime physical intimate partner violence (IPV) perpetration across eight low- and middle-income countries to better understand key risk factors that interventions can target in order to promote gender equality and reduce IPV. We use data from men (n = 7806) that were collected as part of the International Men and Gender Equality Survey (IMAGES) in Bosnia and Herzegovina, Brazil, Chile, Croatia, Democratic Republic of Congo (DRC), India, Mexico, and Rwanda. Results show that there is wide variation across countries for lifetime self-reported physical violence perpetration (range: 17% in Mexico to 45% in DRC), men’s support for equal roles for men and women, and acceptability of violence against women. Across the sample, 31% of men report having perpetrated physical violence against a partner in their lifetime. In multivariate analyses examining risk factors for men ever perpetrating physical violence against a partner, witnessing parental violence was the strongest risk factor, reinforcing previous research suggesting the inter-generational transmission of violence. Additionally, having been involved in fights not specifically with an intimate partner, permissive attitudes towards violence against women, having inequitable gender attitudes, and older age were associated with a higher likelihood of ever perpetrating physical IPV. In separate analyses for each country, we found different patterns of risk factors in countries with high perpetration compared to countries with low perpetration. Findings are interpreted to identify key knowledge gaps and directions for future research, public policies, evaluation, and programming.


Soil Biology & Biochemistry | 2001

Response of soil food-web structure to defoliation of different plant species combinations in an experimental grassland community

J Mikola; G. W. Yeates; David A. Wardle; Gary M. Barker; Karen I. Bonner

We established a greenhouse experiment based on replicated mini-ecosystems to evaluate the effects of defoliation of different plant species combinations on soil food-web structure in grasslands. Plant communities, composed of white clover (Trifolium repens), perennial ryegrass (Lolium perenne) and plantain (Plantago lanceolata), were subjected to the following defoliation treatments: no defoliation of any species (control) and selective trimming of all possible one-, two- and three-way combinations of the species either to 27 cm height (weak defoliation) or to 15 cm height (strong defoliation) above the soil surface three times over a 10-week period. Successive defoliations removed the largest amounts of shoot mass from systems in which T. repens was included among the defoliated species because T. repens dominated aboveground plant biomass. At the final harvest shoot mass was lowest in treatments that included defoliation of T. repens, while total root mass was on average lower in strongly than in weakly defoliated systems and did not differ between the control and defoliation treatments. Total shoot production was not affected by defoliation. Microbial basal respiration and soil NO3-N concentration differed between the combinations of defoliated species; e.g. microbial respiration was on average 32% lower in systems in which only L. perenne was defoliated than in systems in which only T. repens was defoliated. Microbial biomass and soil NH4‐N concentration were not significantly affected by defoliation treatments. Enchytraeid abundance differed significantly between the combinations of defoliated species: in systems in which only L. perenne was defoliated enchytraeid abundance was on average 88% lower than in systems in which all species or only T. repens were defoliated. Enchytraeid abundance was also positively associated with total defoliated shoot mass. Abundances of both bacterial-feeding and fungal-feeding nematodes were affected by the combination of defoliated species; e.g. the abundance of bacterial feeders was on average 52% lower in systems in which only T. repens was defoliated than in systems in which both P. lanceolata and T. repens were defoliated. Fungal-feeding nematodes were also more numerous in strongly than in weakly defoliated systems and positively associated with total defoliated shoot mass. Herbivorous nematode abundance was not significantly affected by defoliation treatments. The results show that the response of soil food webs to defoliation can be affected by which combination of species in a plant community is defoliated. Further, it seems that the role of the combination of species that are defoliated may for some components of the soil biota (e.g. fungal-feeding nematodes) be explicable simply in terms of the total mass of foliage removed. However, for other components of the soil biota (e.g. bacterial-feeding nematodes and enchytraeids) species-specific properties of different plant species in the combination of defoliated species are also clearly important, over and above simple mass removal effects of defoliation. q 2001 Elsevier Science Ltd. All rights reserved.


Molecular Ecology | 2009

Phylogeography and ecological niche modelling implicate coastal refugia and trans‐alpine dispersal of a New Zealand fungus beetle

Katharine A. Marske; Richard A. B. Leschen; Gary M. Barker; Thomas R. Buckley

The Last Glacial Maximum (LGM) severely restricted forest ecosystems on New Zealand’s South Island, but the extent of LGM distribution for forest species is still poorly understood. We used mitochondrial DNA phylogeography (COI) and ecological niche modelling (ENM) to identify LGM refugia for the mycophagous beetle Agyrtodes labralis (Leiodidae), a forest edge species widely distributed in the South Island. Both the phylogenetic analyses and the ENM indicate that A. labralis refuged in Kaikoura, Nelson, and along much of the South Island’s west coast. Phylogeography of this species indicates that recolonization of the largely deforested east and southeast South Island occurred in a west–east direction, with populations moving through the Southern Alps, and that the northern refugia participated little in interglacial population expansion. This contradicts published studies of other New Zealand species, in which recolonization occurs in a north–south fashion from many of the same refugia.


Ecology Letters | 2011

Combining α - and β -diversity models to fill gaps in our knowledge of biodiversity.

Karel Mokany; Tom Harwood; Jacob McC. Overton; Gary M. Barker; Simon Ferrier

For many taxonomic groups, sparse information on the spatial distribution of biodiversity limits our capacity to answer a variety of theoretical and applied ecological questions. Modelling community-level attributes (α- and β-diversity) over space can help overcome this shortfall in our knowledge, yet individually, predictions of α- or β-diversity have their limitations. In this study, we present a novel approach to combining models of α- and β-diversity, with sparse survey data, to predict the community composition for all sites in a region. We applied our new approach to predict land snail community composition across New Zealand. As we demonstrate, these predictions of metacommunity composition have diverse potential applications, including predicting γ-diversity for any set of sites, identifying target areas for conservation reserves, locating priority areas for future ecological surveys, generating realistic compositional data for metacommunity models and simultaneously predicting the distribution of all species in a taxon consistent with known community diversity patterns.


Men and Masculinities | 2014

Working with Men and Boys to Prevent Gender-based Violence Principles, Lessons Learned, and Ways Forward

Dean Peacock; Gary M. Barker

In spite of tremendous progress toward including gender equality as a global goal—included in numerous UN conventions and the Millennium Development Goals—much progress remains to be made. Men’s violence against women remains a pervasive feature of life in every country in the world. Increasing attention is being paid to engaging men and boys to end men’s violence. Programs and policies have been successfully piloted by nongovernmental organizations across the world and shown to promote important and positive change in men’s gender-related attitudes and practices, including in reducing men’s use of violence against women. Since the International Conference on Population and Development in 1994, national governments and UN agencies have steadily adopted and implemented policies and community-based interventions intended to change social norms about gender and masculinities. As cross-pollination happens across countries and regions, work with men and boys for gender equality has become more complex, ambitious, and visible, generating important synergies and successes, and some resistance. This article examines the rationale for that work; describes key findings from multicountry studies about the relationship between notions of masculinities and men’s gender-related practices; documents key principles guiding much gender equality work with men and boys; identifies emerging strategies and proposes key next steps to increase the scale, impact, and sustainability of gender transformative work with men and boys.

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Gilianne D. Brodie

University of the South Pacific

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David A. Wardle

Swedish University of Agricultural Sciences

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Brian Heilman

International Center for Research on Women

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Raphael K. Didham

University of Western Australia

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Lia J.K.D. Bogitini

University of the South Pacific

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Corinne Watts

University of Canterbury

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