Douglas J. Levey

Douglas J. Levey
National Science Foundation | NSF · Division of Environmental Biology (DEB)

PhD

About

180
Publications
65,991
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16,603
Citations
Additional affiliations
September 1987 - December 2011
University of Florida
Position
  • Professor (Full)

Publications

Publications (180)
Article
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As earth-bound, bipedal creatures, our view of the world contrasts sharply with that of the miniature winged beasts we call songbirds, capable of crossing vast oceans, deserts, and mountains numerous times during their fast-paced lives. Unsurprisingly, the journeys of songbirds, as well as those of larger birds such as storks defied the comprehensi...
Article
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Dioecy allows separation of female and male functions and therefore facilitates separate co-evolutionary pathways with pollinators and seed dispersers. In monoecious figs, pollinators’ offspring develop inside the syconium by consuming some of the seeds. Flower-stage syconia must attract pollinators, then ripen and attract seed dispersers. In dioec...
Article
Deleterious effects of habitat fragmentation and benefits of connecting fragments could be significantly underestimated because changes in colonization and extinction rates that drive changes in biodiversity can take decades to accrue. In a large and well-replicated habitat fragmentation experiment, we find that annual colonization rates for 239 pl...
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Bee populations are decreasing worldwide. The underlying causes are likely determined by factors at different scales. We tested the relative importance of local resources and landscape connectivity on 64 bumblebee (Bombus impatiens) colonies in experimentally isolated and connected habitat fragments. We used colony mass, no. of workers, and no. of...
Article
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For a half century, habitat configuration – the arrangement of habitat patches within a landscape – has been central to theories of landscape ecology, population dynamics, and community assembly, in addition to conservation strategies. A recent hypothesis advanced by Fahrig (2013) would, if supported, greatly diminish the relevance of habitat confi...
Article
A variety of landscape models are used to conceptualize and interpret human impacts on ecosystems and their biodiversity. The simplest, a ‘patch-matrix’ model, is rooted in Island Biogeography Theory and assumes a dichotomy between generic, easily-defined habitat patches and a surrounding matrix that is completely inhospitable. This dichotomy betwe...
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Habitat fragmentation can create significant impediments to dispersal. A technique to increase dispersal between otherwise isolated fragments is the use of corridors. Although previous studies have compared dispersal between connected fragments to dispersal between unconnected fragments, it remains unknown how dispersal between fragments connected...
Article
Habitat fragmentation affects species and their interactions through intertwined mechanisms that include changes to fragment area, shape, connectivity and distance to edge. Disentangling these pathways is a fundamental challenge of landscape ecology and will help identify ecological processes important for management of rare species or restoration...
Article
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Habitat fragmentation can create significant impediments to dispersal. A technique to increase dispersal between otherwise isolated fragments is the use of corridors. Although previous studies have compared dispersal between connected fragments to dispersal between unconnected fragments, it remains unknown how dispersal between fragments connected...
Article
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Plants can influence the source and severity of seed predation through various mechanisms; the use of secondary metabolites for chemical defense, for example, is well documented. Gut passage by frugivores can also reduce mortality of animal-dispersed seeds, although this mechanism has gained far less attention than secondary metabolites. Apart from...
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Despite broad recognition that habitat loss represents the greatest threat to the world's biodiversity, a mechanistic understanding of how habitat loss and associated fragmentation affect ecological systems has proven remarkably challenging. The challenge stems from the multiple interdependent ways that landscapes change following fragmentation and...
Article
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Since 1997, the National Science Foundation's (NSF) efforts to promote the Broader Impacts Criterion (BIC) have yielded mixed results. Here, we evaluate proposals to the Division of Environmental Biology (DEB) from submission through the reporting stage to assess DEB's implementation of the BIC. Our results suggest that within DEB, past principal i...
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We conducted an analysis of global forest cover to reveal that 70% of remaining forest is within 1 km of the forest’s edge, subject to the degrading effects of fragmentation. A synthesis of fragmentation experiments spanning multiple biomes and scales, five continents, and 35 years demonstrates that habitat fragmentation reduces biodiversity by 13...
Article
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Overhunting in tropical forests reduces populations of vertebrate seed dispersers.If reduced seed dispersal has a negative impact on tree population viability, overhunting could lead to altered forest structure and dynamics, including decreased biodiversity. However, empirical data showing decreased animal-dispersed tree abundance in overhunted for...
Article
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Seeds of Capsicum spp. (wild chilies) are coated with capsaicin, which deters mammalian seed predators. During gut passage through frugivorous birds, its presence on seeds likely is greatly reduced, presumably increasing the seeds' susceptibility to post-dispersal seed predation by mammals. We tested whether gut passage influences the rate at which...
Conference Paper
Background/Question/Methods The theory of island biogeography laid the foundation for predicting and testing the impacts of habitat loss and fragmentation as well as conservation reserve design. Yet, the appropriateness of this classic theory for predicting species richness patterns in spatially-structured terrestrial landscapes has been question...
Conference Paper
Background/Question/Methods Correlations between invasive species dominance and native species decline are often used to assess the impacts of invasive species but are usually confounded by environmental changes associated with invasion, such as habitat disturbance. Are invasive species “drivers” or “passengers” of ecological shifts in communitie...
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Despite many studies showing that landscape corridors increase dispersal and species richness for disparate taxa, concerns persist that corridors can have unintended negative effects. In particular, some of the same mechanisms that underlie positive effects of corridors on species of conservation interest may also increase the spread and impact of...
Article
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Landscape corridors are commonly used to mitigate negative effects of habitat fragmentation, but concerns persist that they may facilitate the spread of invasive species. In a replicated landscape experiment of open habitat, we measured effects of corridors on the invasive fire ant, Solenopsis invicta, and native ants. Fire ants have two social for...
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Migratory vertebrates adjust their movements in response to environmental change. Throughout their migrations, they gather information, integrate environmental and internal state data, and make decisions about the timing and orientation of migratory movements. Understanding this class of animal decision-making has both basic and applied interest be...
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The fundamental properties of organisms—what they are, how and where they live, and the biotic and abiotic interactions that link them to communities and ecosystems—are the domain of natural history. We provide examples illustrating the vital importance of natural history knowledge to many disciplines, from human health and food security to conserv...
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Determining how widespread human-induced changes such as habitat loss, landscape fragmentation, and climate instability affect populations, communities, and ecosystems is one of the most pressing environmental challenges. Critical to this challenge is understanding how these changes are affecting the movement abilities and dispersal trajectories of...
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The conversion of natural habitats to unsustainable land use practices that continues in many developing countries can further degrade the agricultural landscape and hinder the development of rural areas. Agroforestry is one of the approaches being used to addressing this problem. Acquiring the information pertaining to such sustainable practices a...
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Historical records of species are compared with current records to elucidate effects of recent climate change. However, confounding variables such as succession, land-use change, and species invasions make it difficult to demonstrate a causal link between changes in biota and changes in climate. Experiments that manipulate temperature can overcome...
Article
The conversion of natural habitats to unsustainable land use practices that continues in many developing countries can further degrade the agricultural landscape and hinder the development of rural areas. Agroforestry is one of the approaches being used to addressing this problem. Acquiring the information pertaining to such sustainable practices a...
Article
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Sodium is an essential dietary element and preferential foraging for high concentrations of sodium by inland herbivorous and omnivorous ants suggests it may be limiting. If so, increased sodium availability through altered deposition and anthropogenic sources may lead to increased colony and population growth and cascading ecological impacts.For re...
Article
Agroforestry practices, such as Shaded Coffee and Homegardens, may provide habitat for forest butterflies and contribute to their conservation in fragmented agricultural landscapes. To determine the influence of agroforestry practices in an agricultural mosaic, the distribution of fruit-feeding butterflies was studied using a systematic approach th...
Article
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Long distance seed dispersal (LDD) is considered a crucial determinant of tree distributions, but its effects depend on demographic processes that enable seeds to establish into adults and that remain poorly understood at large spatial scales. We estimated rates of seed arrival, germination, and survival and growth for a canopy tree species (Milius...
Conference Paper
Background/Question/Methods Landscape corridors – strips of habitat that connect otherwise isolated habitat fragments – are a leading strategy for mitigating negative impacts of habitat fragmentation on biodiversity. Despite widespread implementation, questions remain about corridor efficacy, particularly how corridors affect dispersal of dispara...
Conference Paper
Background/Question/Methods Landscape connectivity – or the degree to which the landscape facilitates dispersal – is a fundamentally important factor regulating species diversity and is becoming increasingly in human-dominated landscapes that are affected by habitat fragmentation and climate instability. The impact of connectivity on diversity, h...
Conference Paper
Background/Question/Methods Negative effects of habitat fragmentation have led to widespread use of habitat corridors in conservation. Yet not all species respond to corridors in the same way. Predicting these differences is difficult due to lack of a robust, empirically validated framework that applies to the diverse taxa that characterize ecolog...
Conference Paper
Background/Question/Methods Seed dispersal is essential for plant recruitment. Despite much attention to animals as seed dispersers, very few studies have been able to link spatial patterns of animal-generated seed shadows to patterns of tree regeneration. We asked: How do species of seed dispersers differ in the seed shadows they create, and are...
Conference Paper
Background/Question/Methods Long distance seed dispersal (LDD) can have major consequences for plant population and community dynamics. Because rates of LDD can enable range expansion of invasive species, plant migration in response to climate change and species persistence in fragmented landscapes, LDD also has relevance for biodiversity conserv...
Article
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Seed ingestion by frugivorous vertebrates commonly benefits plants by moving seeds to locations with fewer predators and pathogens than under the parent. For plants with high local population densities, however, movement from the parent plant is unlikely to result in 'escape' from predators and pathogens. Changes to seed condition caused by gut pas...
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Quantifying the relative importance of the multiple processes that limit recruitment may hold the key to understanding tropical tree diversity. Here we couple theoretical models with a large-scale, multi-species seed-sowing experiment to assess the degree to which seed and establishment limitation shape patterns of tropical tree seedling recruitmen...
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Little is known about the timing of migration, migration routes, and migratory connectivity of most of the >230 species of birds that breed at south temperate latitudes of South America and then migrate toward the tropics to overwinter. We used light-level geolocators to track the migration of 3 male and 3 female Fork-tailed Flycatchers (Tyrannus s...
Article
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In fragmented landscapes, plant population persistence and community diversity can hinge upon plants dispersing seeds long distances between isolated patches of habitat. Landscape corridors, which connect otherwise isolated patches, have been shown to increase seed dispersal by birds moving between patch fragments. But as bird behaviors change seas...
Article
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Descriptions of intra- and interspecific variation in migratory patterns of closely related species are rare yet valuable because they can help assess how differences in ecology and life-history strategies drive the evolution of migration. We report data on timing and location of migration routes and wintering areas, and on migratory speed and phen...
Article
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Habitat fragmentation disrupts species movement, leading to local extinctions and altered community structure. Habitat corridors, which connect isolated patches of habitat and facilitate movement between patches, provide a potential solution to these negative impacts. However, most studies to date have examined the movement of species alone without...
Conference Paper
Background/Question/Methods Widespread anthropogenic changes in landscape structure can alter dispersal and other movements of organisms, impacting populations, communities, and ecosystems. Key challenges in understanding wind-dispersed organisms are to extract the basic principles of wind dispersal in various types of fragmented environments, and...
Conference Paper
Background/Question/Methods Landscape corridors – strips of habitat that connect otherwise isolated habitat fragments – are a popular management technique used to mitigate negative effects of habitat fragmentation. Corridors have been shown to promote movement of individuals, plant-animal interactions, and community diversity. These findings rema...
Conference Paper
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Over 250 bird species migrate wholly within South America, many of which spenddifferent parts of their annual cycle in different countries. We attached light-level geolocatorsto individual migrant flycatchers of the genus Tyrannus in Santa Cruz Department, Bolivia(twelve White-throated Kingbirds, T. albogularis) and Buenos Aires Province, Argentina...
Article
ABSTRACT Fleshy fruit is a key food resource for many vertebrates and may be particularly important energy source to birds during fall migration and winter. Hence, land managers should know how fruit availability varies among forest types, seasons, and years. We quantified fleshy fruit abundance monthly for 9 years (1995-2003) in 56 0.1-ha plots in...
Article
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Habitat corridors confer many conservation benefits by increasing movement of organisms between habitat patches, but the benefits for some species may exact costs for others. For example, corridors may increase the abundance of consumers in a habitat to the detriment of the species they consume. In this study we assessed the impact of corridors on...
Article
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In tropical forests, resource-based niches and density-dependent mortality are mutually compatible mechanisms that can act simultaneously to limit seedling populations. Differences in the strengths of these mechanisms will determine their roles in maintaining species coexistence. In the first assessment of these mechanisms in a Congo Basin forest,...
Article
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We describe partial migration of passerine birds across temperate latitudes in the New World. Owing to lower climatic seasonality near the coast of North America, the proportion of partial migrants at high latitudes in North America should be lower when excluding coastal records. We detected a 10% decrease in the proportion of partially migratory s...
Article
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Evolutionary biologists increasingly recognize that evolution can be constrained by trade-offs, yet our understanding of how and when such constraints are manifested and whether they restrict adaptive divergence in populations remains limited. Here, we show that spatial heterogeneity in moisture maintains a polymorphism for pungency (heat) among na...
Article
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Research on Nearctic-Neotropical migratory birds in Colombia has strengthened in the last decade although most work has been centered on boreal migrants. Achievements are reflected in recent publications, in the studies presented at national ornithology conferences, and in the publication of the National Plan for Conservation of Migratory Species....
Conference Paper
Background/Question/Methods Habitat fragmentation disrupts ecological processes and is a driver of species extinctions. Corridors that connect otherwise isolated fragments of habitat may mitigate these negative effects on populations and communities. Although experimental work generally confirms that corridors increase movement of individuals bet...
Conference Paper
Background/Question/Methods Granivores have significant impacts on seedling recruitment in many species. Capsaicin in wild chilies (Capsicum annuum) deters mammalian granivores but does not deter consumption by birds or insects. This study examined whether gut passage by frugivorous birds influences post-dispersal seed predation. C. annuum seeds...
Chapter
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Young (1–10 year post-disturbance) upland hardwood forests function as high-quality food patches by providing abundant fruit, and nutritious foliage and flowers that attract pollinating and foliar arthropods and support high populations of small mammals that, in turn, are prey for numerous vertebrate predators. Reductions in basal area increase lig...
Article
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The most popular landscape-level strategy to conserve biodiversity is to link reserves with corridors. Despite much theoretical and empirical support for their benefits in creating or maintaining population sources, corridors may have negative effects and create sinks by altering the dynamics of competitors and natural enemies. In this chapter, we...
Article
Little is known about the relationship between seasonal food availability and the foraging strategies of insectivorous Neotropical birds. We studied a population of Tropical Kingbirds (Tyrannus melancholicus), a primarily insectivorous species, in eastern Bolivia to examine relationships between rainfall, food availability, and foraging strategies...
Article
1. Little is known about mechanisms that drive migration of birds at tropical latitudes. Because most migratory bird species in South America have populations that are present year-round, partial migration (in which only some individuals of a given population migrate at the end of the breeding season) is likely to be common, providing an opportunit...
Article
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Seed dispersal by vertebrates is one of the most common and important plant-animal mutualisms, involving an enormous diversity of fruiting plants and frugivorous animals. Even though plant reproduction depends largely on seed dispersal, evolutionary ecologists have been unable to link co-occurring traits in fruits with differences in behavior, phys...
Conference Paper
Background/Question/Methods Habitat fragmentation is a formidable threat to biodiversity worldwide. Maintaining connectivity among remnant habitat patches is a central management plan to promote biodiversity. Therefore, understanding how the spatial arrangement of habitat patches in landscapes affect functional connectivity for communities is a cr...