Native fruit traits may mediate dispersal competition between native and non-native plants

Seed disperser preferences may mediate the impact of invasive, non-native plant species on their new ecological communities. Significant seed disperser preference for invasives over native species could facilitate the spread of the invasives while impeding native plant dispersal. Such competition for dispersers could negatively impact the fitness of some native plants. Here, we review published literature to identify circumstances under which preference for non-native fruits occurs. The importance of fruit attraction is underscored by several studies demonstrating that invasive, fleshy-fruited plant species are particularly attractive to regional frugivores. A small set of studies directly compare frugivore preference for native vs. invasive species, and we find that different designs and goals within such studies frequently yield contrasting results. When similar native and non-native plant species have been compared, frugivores have tended to show preference for the non-natives. This preference appears to stem from enhanced feeding efficiency or accessibility associated with the non-native fruits. On the other hand, studies examining preference within existing suites of co-occurring species, with no attempt to maximize fruit similarity, show mixed results, with frugivores in most cases acting opportunistically or preferring native species. A simple, exploratory meta-analysis finds significant preference for native species when these studies are examined as a group. We illustrate the contrasting findings typical of these two approaches with results from two smallscale aviary experiments we conducted to determine preference by frugivorous bird species in northern California. In these case studies, native birds preferred the native fruit species as long as it was dissimilar from non-native fruits, while non-native European starlings preferred non-native fruit. However, native birds showed slight, non-significant preference for non-native fruit species when such fruits were selected for their physical resemblance to the native fruit species. Based on our review and case studies, we propose that fruit characteristics of native plant communities could dictate how well a non-native, fleshy-fruited plant species competes for dispersers with natives. Native bird preferences may be largely influenced by regional native fruits, such that birds are attracted to the colors, morphology, and infructescence structures characteristic of preferred native fruits. Non-native fruits exhibiting similar traits are likely to encounter bird communities predisposed to consume them. If those non-natives offer greater fruit abundance, energy content, or accessibility, they may outcompete native plants for dispersers

Introduction to the Special Issue: The Role of Seed Dispersal in Plant Populations: Perspectives and Advances in a Changing World

Despite the importance of seed dispersal as a driving process behind plant community assembly, our understanding of the role of seed dispersal in plant population persistence and spread remains incomplete. As a result, our ability to predict the effects of global change on plant populations is hampered. We need to better understand the fundamental link between seed dispersal and population dynamics in order to make predictive generalizations across species and systems, to better understand plant community structure and function, and to make appropriate conservation and management responses related to seed dispersal. To tackle these important knowledge gaps, we established the CoDisperse Network and convened an interdisciplinary, NSF-sponsored Seed Dispersal Workshop in 2016, during which we explored the role of seed dispersal in plant population dynamics (NSF DEB Award # 1548194). In this Special Issue, we consider the current state of seed dispersal ecology and identify the following collaborative research needs: (i) the development of a mechanistic understanding of the movement process influencing dispersal of seeds; (ii) improved quantification of the relative influence of seed dispersal on plant fitness compared to processes occurring at other life history stages; (iii) an ability to scale from individual plants to ecosystems to quantify the influence of dispersal on ecosystem function; and (iv) the incorporation of seed dispersal ecology into conservation and management strategies

Non-native insects dominate daytime pollination in a high-elevation Hawaiian dryland ecosystem

PREMISE OF THE STUDY: Over one-third of the native flowering plant species in the Hawaiian Islands are listed as federally threatened or endangered. Lack of sufficient pollination could contribute to reductions in populations, reproduction, and genetic diversity among these species but has been little studied. METHODS: We used systematic observations and manual flower treatments to quantify flower visitation and outcrossing dependency of eight native (including four endangered) plant species in a dryland ecosystem in Hawaii: Argemone glauca, Bidens menziesii, Dubautia linearis, Haplostachys haplostachya, Sida fallax, Silene lanceolata, Stenogyne angustifolia, and Tetramolopium arenarium. KEY RESULTS: During 576.36 h of flower observations, only insects visited the flowers. Out of all recorded flower visits, 85% were performed by non-native species, particularly the honeybee (Apis mellifera) and flies in the family Syrphidae. Some plant species received little visitation (e.g., S. angustifolia received one visit in 120 h of observation), whereas others were visited by a wide diversity of insects. The endangered plant species were visited by fewer visitor taxa than were the common native plant species. For six of the focal plant species, bagging of flowers to exclude pollinators resulted in significant reductions in seed set. CONCLUSIONS: The flower visitor community in this system, although heavily dominated by non-native insects, appears to be facilitating pollination for multiple plant species. Non-native insects may thus be sustaining biotic interactions otherwise threatened with disruption in this island ecosystem. This may be particularly important for the studied endangered plant species, which exhibit fewer partners than the more common plant species

Absence of native flower visitors for the endangered Hawaiian mint \u3ci\u3eStenogyne angustifolia\u3c/i\u3e: Impending ecological extinction?

If an organism becomes rare enough that it no longer participates in certain interspecific interactions, it can be said to have become ecologically extinct, even though it is still present. This form of extinction is much less recognized than global extinctions, although it may have ramifications for ecological community function. Here, we describe a case of possible or pending ecological extinction of an endemic Hawaiian plant. We performed over 120 h of systematic flower visitation observations of the endangered Hawaiian mint, Stenogyne angustifolia, in its wild habitat. The robust size and open shape of S. angustifolia flowers, along with their high accessibility, visibility, and nectar content, suggest that they are adapted to animal-mediated pollination. However, only one flower visitor was observed at our focal high-elevation study site: an individual of the non-native bee species Lasioglossum impavidum. Experimental pollination treatments indicate that S. angustifolia is self-compatible and demonstrates some autogamy, setting fruit and seed in the absence of pollinators. However, experimental additions of pollen increased fruit production, indicating that plants are pollen-limited and that lack of pollinators carries a reproductive cost for this species. Ecological communities throughout Hawaii are highly modified, and the distribution and diversity of the native pollinator community that occurred with S. angustifolia prior to these changes are wholly unknown. Nevertheless, the lack of visitation by native pollinators and extremely rare visitation by non-native pollinators suggest that this plant is today contributing little to pollination networks in its high-elevation habitat

Operationalizing resilience for conservation objectives: the 4S’s

Although resilience thinking is increasingly popular and attractive among restoration practitioners, it carries an abstract quality that hinders effective application. Because resilience and its components are defined differently in social and ecological contexts, individual managers or stakeholders may disagree on the definition of a system’s state, occurrence of a state change, preferred state characteristics, and appropriate methods to achieve success. Nevertheless, incentives and mandates often force managers to demonstrate how their work enhances resilience. Unclear or conflicting definitions can lead to ineffective or even detrimental decision-making in the name of resilience; essentially, any convenient action can be touted as resilience-enhancing in this case. We contend that any successful resilience management project must clearly identify up-front the stressors of concern, state traits, scales of appropriate management, and success indicators (the 4S’s) relevant to the management targets. We propose a deliberate process for determining these components in advance of resilience management for conservation. Our recommendations were inspired and informed by two case studies wherein different definitions of stressors, state, scales, and success would result in very different management choices, with potentially serious consequences for biodiversity targets

Unlikely Alliances and Their Implications for Resource Management in the American West

Collaborative, or participatory governance is an increasingly common means of addressing natural resource issues, especially in the American West where patchworks of public, private, and tribal interests characterize the region’s resources. In this context, unlikely alliances, or partnerships among diverse actors who have historically been at odds, have a growing potential to shape social and ecological outcomes, for better or worse. While these unlikely alliances have received greater attention in recent years, relatively little research has worked to synthesize the concept across diverse contexts and disciplines. Based on a review of the literature on unlikely alliances in natural resource governance, we develop a framework that synthesizes the individual motivations and contextual factors that influence their formation, as well as the social and ecological outcomes that they create. We use this framework to analyze six illustrative cases of unlikely alliances. Our analysis of these cases suggests that unlikely alliances in the American West are likely to arise in the presence of a crisis, when appropriate leadership is present, when some of the actors have interacted effectively in the past, and when actors need to pool resources. The cases also illustrate some common outcomes, including environmental improvement, transformation of social networks, policy change, and shifts in power relationships. We discuss the implications of unlikely alliances for the social-ecological future of the American West. Our paper highlights the role of unlikely alliances in shaping patterns of natural resource governance, and provides a focus for further research in this realm

Invasive predators affect community-wide pollinator visitation

Disruption of plant–pollinator interactions by invasive predators is poorly understood but may pose a critical threat for native ecosystems. In a multiyear field experiment in Hawai’i, we suppressed abundances of globally invasive predators and then observed insect visitation to flowers of six native plant species. Three plant species are federally endangered (Haplostachys haplostachya, Silene lanceolata, Tetramolopium arenarium) and three are common throughout their range (Bidens menziesii, Dubautia linearis, Sida fallax). Insect visitors were primarily generalist pollinators, including taxa that occur worldwide such as solitary bees (e.g., Lasioglossum impavidum), social bees (e.g., Apis mellifera), and syrphid flies (e.g., Allograpta exotica). We found that suppressing invasive rats (Rattus rattus), mice (Mus musculus), ants (Linepithema humile, Tapinoma melanocephalum), and yellowjacket wasps (Vespula pensylvanica) had positive effects on pollinator visitation to plants in 16 of 19 significant predator–pollinator–plant interactions. We found only positive effects of suppressing rats and ants, and both positive and negative effects of suppressing mice and yellowjacket wasps, on the frequency of interactions between pollinators and plants. Model results predicted that predator eradication could increase the frequency of insect visitation to flowering species, in some cases by more than 90%. Previous results from the system showed that these flowering species produced significantly more seed when flowers were allowed to outcross than when flowers were bagged to exclude pollinators, indicating limited autogamy. Our findings highlight the potential benefits of suppression or eradication of invasive rodents, ants, and yellowjackets to reverse pollination disruption, particularly in locations with high numbers of at-risk plant species or already imperiled pollinator populations

Coupled ecological and management connectivity across administrative boundaries in undeveloped landscapes

Human-induced ecological boundaries, or anthropogenic ecotones, may arise where administrative boundaries meet on undeveloped lands. Landscape-level ecological processes related to factors such as fire, invasive species, grazing, resource extraction, wildlife, and water may be affected due to unique management strategies adopted by each administrative unit. Over time, different management can result in discernible ecological differences (e.g., species composition or soil characteristics). Thus, fragmentation in the management landscape can correspond to ecological fragmentation. Different ecological patterns may emerge due to an increase in the number of management units in a region, or due to an increase in the number of different types of management units in the region. Temporal effects and collaboration history can also affect the emergence of ecotones. We use conceptual models to explore the relationship between these aspects of management fragmentation and the anthropogenic ecotones between management parcels. We then use examples of different management challenges to explore how anthropogenic ecotones can disrupt ecological flows. Our models suggest that cross-boundary collaboration that enhances management connectivity is likely essential to ecological connectivity in the face of environmental and social change

Quantifying ecological variation across jurisdictional boundaries in a management mosaic landscape

Context Large landscapes exhibit natural heterogeneity. Land management can impose additional variation, altering ecosystem patterns. Habitat characteristics may reflect these management factors, potentially resulting in habitat differences that manifest along jurisdictional boundaries. Objectives We characterized the patchwork of habitats across a case study landscape, the Grand Canyon Protected Area-Centered Ecosystem. We asked: how do ecological conditions vary across different types of jurisdictional boundaries on public lands? We hypothesized that differences in fire and grazing, because they respond to differences in management over time, contribute to ecological differences by jurisdiction. Methods We collected plot-scale vegetation and soils data along boundaries between public lands units surrounding the Grand Canyon. We compared locations across boundaries of units managed differently, accounting for vegetation type and elevation differences that pre-date management unit designations. We used generalized mixed effects models to evaluate differences in disturbance and ecology across boundaries. Results Jurisdictions varied in evidence of grazing and fire. After accounting for these differences, some measured vegetation and soil properties also differed among jurisdictions. The greatest differences were between US Forest Service wilderness and Bureau of Land Management units. For most measured variables, US Forest Service non-wilderness units and National Park Service units were intermediate. Conclusions In this study, several ecological properties tracked jurisdictional boundaries, forming a predictable patchwork of habitats. These patterns likely reflect site differences that pre-date jurisdictions as well as those resulting from different management histories. Understanding how ecosystem differences manifest at jurisdictional boundaries can inform resource management, conservation, and cross-boundary collaborations

New insights into the structure of nanoporous carbons from NMR, Raman, and pair distribution function analysis

The structural characterization of nanoporous carbons is a challenging task as they generally lack long-range order and can exhibit diverse local structures. Such characterization represents an important step toward understanding and improving the properties and functionality of porous carbons, yet few experimental techniques have been developed for this purpose. Here we demonstrate the application of nuclear magnetic resonance (NMR) spectroscopy and pair distribution function (PDF) analysis as new tools to probe the local structures of porous carbons, alongside more conventional Raman spectroscopy. Together, the PDFs and the Raman spectra allow the local chemical bonding to be probed, with the bonding becoming more ordered for carbide-derived carbons (CDCs) synthesized at higher temperatures. The ring currents induced in the NMR experiment (and thus the observed NMR chemical shifts for adsorbed species) are strongly dependent on the size of the aromatic carbon domains. We exploit this property and use computer simulations to show that the carbon domain size increases with the temperature used in the carbon synthesis. The techniques developed here are applicable to a wide range of porous carbons and offer new insights into the structures of CDCs (conventional and vacuum-annealed) and coconut shell-derived activated carbons