J. Scott MacIvor

Decoupling factors affecting plant diversity and cover on extensive green roofs.

Supplemental irrigation systems are often specified on green roofs to ensure plant cover and growth, both important components of green roof performance and aesthetics. Properties of the growing media environment too can alter the assemblage of plant species able to thrive. In this study we determine how plant cover, above ground biomass and species diversity are influenced by irrigation and growing media. Grass and forb vegetative cover and biomass were significantly greater in organic based growing media but there was no effect of supplemental irrigation, with two warm season grasses dominating in those treatments receiving no supplemental irrigation. On the other hand, plant diversity declined without irrigation in organic media, and having no irrigation in inorganic growing media resulted in almost a complete loss of cover. Sedum biomass was less in inorganic growing media treatments and species dominance shifted when growing media organic content increased. Our results demonstrate that supplemental irrigation is required to maintain plant diversity on an extensive green roof, but not necessarily plant cover or biomass. These results provide evidence that planting extensive green roofs with a mix of plant species can ensure the survival of some species; maintaining cover and biomass when supplemental irrigation is turned off to conserve water, or during extreme drought.

Biodiversity in the City: Fundamental Questions for Understanding the Ecology of Urban Green Spaces for Biodiversity Conservation

&NA; As urban areas expand, understanding how ecological processes function in cities has become increasingly important for conserving biodiversity. Urban green spaces are critical habitats to support biodiversity, but we still have a limited understanding of their ecology and how they function to conserve biodiversity at local and landscape scales across multiple taxa. Given this limited view, we discuss five key questions that need to be addressed to advance the ecology of urban green spaces for biodiversity conservation and restoration. Specifically, we discuss the need for research to understand how green space size, connectedness, and type influence the community, population, and life‐history dynamics of multiple taxa in cities. A research framework based in landscape and metapopulation ecology will allow for a greater understanding of the ecological function of green spaces and thus allow for planning and management of green spaces to conserve biodiversity and aid in restoration activities.

Cavity-nest boxes for solitary bees: a century of design and research

A variety of solitary bee species that naturally nest in wood and plant stems aboveground also readily accept nest boxes, which are human-made devices that aggregate these nesting conditions. Nest boxes are sheltered bundles of hollow plant stems, bamboo or reeds, and holes drilled into wood or cavities made of other materials such as glass or polystyrene. In this paper, I examine the best practises in nest box material selection and construction, and the use of nest boxes to address four basic objectives related to our understanding of bee biology and enhancement of pollination services. A variety of materials and cavity dimensions are included in nest boxes that are used to monitor local bee diversity or to address fundamental questions in community ecology and environmental change. Others examine bee biology, physiology and behaviour that use nest boxes to obtain bees for further experimentation. The majority of studies use nest boxes in agricultural landscapes and in alternative pollinator management; these studies improve nest box design for target bee species to augment their numbers. Continued design and data sharing, as well as the refinement of nest box construction and deployment for specific objectives, will ensure they remain useful tools for bee science, conservation and alternative pollinator management.

Are urban systems beneficial, detrimental, or indifferent for biological invasion?

Urban environments are often seen as unique or degraded habitats that both present hardships for some sensitive species and provide opportunities to others. Non-indigenous species (NIS) are commonly referenced in the latter group, and are comprised of species that can tolerate the unique conditions or capitalize on the opportunities found in urban environments. Moreover, these urban beneficiaries may be those that normally cannot overcome competitive interactions in intact native communities, but find opportunity to flourish in urban habitats. We ask the question: do NIS benefit from urbanization? We answer this question using three strategies. First, we explore the problem conceptually, using community assembly theory. Second, we perform a broad literature review. Finally, we analyze studies with sufficient information using a meta-analysis. We show that the available evidence supports the proposition that NIS benefit from urbanization, with NIS obtaining higher abundances and greater diversity in more urbanized habitats. There were only 43 studies that measured NIS abundance and diversity while adequately quantifying the degree of urbanization surrounding plots, and effect sizes (measured by Hedge’s D) reveal that NIS obtain higher abundances in more urbanized habitats, and especially for invertebrates. Despite the intense interest in NIS dynamics and impacts, we note a general dearth of robust studies that adequately quantify ‘urbanization’, and we end with a general call for more detailed research.

DNA barcoding to identify leaf preference of leafcutting bees

Leafcutting bees (Megachile: Megachilidae) cut leaves from various trees, shrubs, wildflowers and grasses to partition and encase brood cells in hollow plant stems, decaying logs or in the ground. The identification of preferred plant species via morphological characters of the leaf fragments is challenging and direct observation of bees cutting leaves from certain plant species are difficult. As such, data are poor on leaf preference of leafcutting bees. In this study, I use DNA barcoding of the rcbL and ITS2 regions to identify and compare leaf preference of three Megachile bee species widespread in Toronto, Canada. Nests were opened and one leaf piece from one cell per nest of the native M. pugnata Say (N=45 leaf pieces), and the introduced M. rotundata Fabricius (N=64) and M. centuncularis (L.) (N=65) were analysed. From 174 individual DNA sequences, 54 plant species were identified. Preference by M. rotundata was most diverse (36 leaf species, H′=3.08, phylogenetic diversity (pd)=2.97), followed by M. centuncularis (23 species, H′=2.38, pd=1.51) then M. pugnata (18 species, H′=1.87, pd=1.22). Cluster analysis revealed significant overlap in leaf choice of M. rotundata and M. centuncularis. There was no significant preference for native leaves, and only M. centuncularis showed preference for leaves of woody plants over perennials. Interestingly, antimicrobial properties were present in all but six plants collected; all these were exotic plants and none were collected by the native bee, M. pugnata. These missing details in interpreting what bees need offers valuable information for conservation by accounting for necessary (and potentially limiting) nesting materials.

Non-native species in urban environments: patterns, processes, impacts and challenges

AbstractAlthough urban ecosystems are hotspots for biological invasions, the field of invasion science has given scant attention to invasion dynamics and the challenges facing managers in towns and cities. This paper provides an introduction to the growing challenges of understanding and managing invasive species in urban systems, and the context for a special issue of Biological Invasions, comprising 17 papers, that arose from a workshop on “Non-native species in urban environments: patterns, processes, impacts and challenges” held in Stellenbosch, South Africa, in November 2016. Contributions explore the following key questions: Are patterns and processes of urban invasions different from invasions in other contexts? Why is it important to manage non-native species in urban ecosystems? What are the special management needs in an urban context? How can we bridge the gaps between science, management, and policy with regards to biological invasions in urban ecosystems? The papers in this special issue show that patterns and processes of urban invasions differ in many ways from invasions in other contexts, and that managing invasive species in cities poses unique and increasingly complex challenges. Progress in urban invasion science requires further work to: (1) address key limitations that hinder our understanding of invasion dynamics in cities; (2) clarify whether fundamental concepts in the field of invasion science are appropriate for urban ecosystems; (3) integrate insights from invasion science with those from the burgeoning literature on the “Anthropocene biosphere”, novel ecosystems, social–ecological systems, human–wildlife conflicts, urban green infrastructure, urban planning and design, and ecosystem services/disservices.

Phylogenetic diversity and plant trait composition predict multiple ecosystem functions in green roofs

Plant selection and diversity can influence the provision of key ecosystem services in extensive green roofs. While species richness does predict ecosystem services, functional and phylogenetic community structure may provide a stronger mechanistic link to such services than species richness alone. In this study, we assessed the relationship between community-weighted trait values from four key leaf and canopy functional traits (plant height, leaf area, specific leaf area, dry leaf matter content), functional diversity, and phylogenetic diversity to ten different green roof functions, including ecosystem multifunctionality, in experimental polycultures. Functional traits of dominant plant species were a major driver for indicators of multiple green roof functions, such as substrate nitrate-N, substrate phosphorus, aboveground biomass and ecosystem multifunctionality. In contrast, functional diversity alone increased substrate organic matter. Moreover, both functional/phylogenetic diversity and identity predicted canopy density, substrate cooling. This study highlights the first line of evidence that distinct aspects of phylogenetic and functional diversity play a major role in predicting multiple green roof services. Therefore, we provide further evidence that to maximize green roof functioning, a very careful selection of plant traits and polycultures are needed.

Questioning public perception, conservation policy, and recovery actions for honeybees in North America

Global pollinator declines have resulted in an increasing number of policies and actions to help bee populations. In North America, there is strong public engagement, but also growing controversies over how to address declines. This is fueled by complex scientific evidence across species, habitat types, geographic regions, as well as intense lobbying by NGOs, beekeeping, agro-chemical and farming industries. Policy and conservation initiatives often focus on the Western Honeybee, Apis mellifera Linnaeus, a domesticated species not native to North America. Although losses of managed honeybee colonies are recorded annually, we argue that honeybee losses are not a conservation problem, but instead a domesticated animal management issue. By focusing attention on honeybees, policies and subsequent resources may undermine native bee conservation and have negative impacts ecologically and socially. This article is protected by copyright. All rights reserved

Wild Bees in Cultivated City Gardens

The pursuit for and production of fresh and local fruits and vegetables is gaining popularity among homeowners and community groups in cities. Cultivating crops allows one to connect to natural processes, invest in food security and gain crucial life skills. It’s also relaxing, provides exercise and is a lot of fun. Although gardening is one of the most common activities among homeowners, and many are aware of the role of pollinators in plant reproduction, the various needs of pollinating insects are often overlooked in garden design and maintenance.

The Necessity of Multitrophic Approaches in Community Ecology

Trophic interactions are a fundamental part of ecosystems; yet, most ecological studies focus on single trophic levels and this hampers our ability to detect the underlying mechanisms structuring communities as well as the effects of environmental change. Here, we argue that the historical dominance of studying competition within trophic levels, and the focus on taxonomic groups without differentiating the trophic level, has led to the under-representation of multitrophic research in community ecology. There are many hurdles that challenge multitrophic approaches and we discuss solutions to overcome these. To advance our understanding of the fundamental drivers of community assembly and to provide the necessary guidance for managing and mitigating the effects of environmental change, we argue that ecologists should better align research with a trophically inclusive definition of a community.