Douglas J. Levey

• PhD
• Project Manager at National Science Foundation

Although individuals of some species appear able to distinguish among individuals of a second species, an alternative explanation is that individuals of the first species may simply be distinguishing between familiar and unfamiliar individuals of the second species. In that case, they would not be learning unique characteristics of any given hetero...

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...

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...

Habitat connectivity enhances diversity Fragmentation of ecosystems leads to loss of biodiversity in the remaining habitat patches, but retaining connecting corridors can reduce these losses. Using long-term data from a large, replicated experiment, Damschen et al. show quantitatively how these losses are reduced. In their pine savanna system, corr...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

Significance Understanding how widespread human-induced global changes are affecting the movement and dispersal of organisms is critical for maintaining species diversity and making sound land management decisions. In contrast with animal-dispersed species, little is known about how wind-dispersed species are affected by conservation strategies suc...

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...

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...

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...

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 r...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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,...

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...

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...

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....

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...

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...

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...

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...

Source-sink theories provide a simple yet powerful framework for understanding how the patterns, processes and dynamics of ecological systems vary and interact over space and time. Integrating multiple research fields, including population biology and landscape ecology, this book presents the latest advances in source-sink theories, methods and app...

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...

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...

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...

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...

Tropical montane species are characterized by narrow elevational distributions. Recent perspectives on mechanisms maintaining these restricted distributions have emphasized abiotic processes, but biotic processes may also play a role in their establishment or maintenance. One historically popular hypothesis, especially for birds, is that interspeci...

We attempted to distinguish spring passage migrant Tropical Kingbirds (Tyrannus melancholicus) from resident conspecifics where they overlap in South America. Migrant males at our Bolivian study site had significantly less tail feather molt and longer wing chords than resident males. Migrant females had significantly longer wing chords, less flight...

Migratory bird needs must be met during four phases of the year: breeding season, fall migration, wintering, and spring migration; thus, management may be needed during all four phases. The bulk of research and management has focused on the breeding season, although several issues remain unsettled, including the spatial extent of habitat influences...

Our understanding of migratory birds' year-round ecology and evolution remains patchy despite recent fundamental advances. Periodic reviews focus future research and inform conservation and management; here, we take advantage of our combined experiences working on Western Hemisphere avian migration systems to highlight recent lessons and critical g...

Understanding how home range size varies across seasons can provide insights into how birds respond to changes in resource levels. Yet, seasonal variation in home range size of most Neotropical birds is poorly understood. We recorded locations of color-banded Tropical Kingbirds during four years at a site comprised of cerrado woodland, humid forest...

Background/Question/Methods One of the most important challenges facing ecologists and conservationists is to understand how species composition of communities changes across heterogeneous landscapes. On the level of individual species, an important corollary is to understand ecological factors that enforce the limits of species’ ranges. Tropical...

Conservation efforts typically focus on maximizing biodiversity in protected areas. The space available for reserves is limited, however, and conservation efforts must increasingly consider how management of protected areas can promote biodiversity beyond reserve borders. Habitat corridors are considered an important feature of reserves because the...

Practically all animals are affected by humans, especially in urban areas. Although most species respond negatively to urbanization, some thrive in human-dominated settings. A central question in urban ecology is why some species adapt well to the presence of humans and others do not. We show that Northern Mockingbirds (Mimus polyglottos) nesting o...

TY

Durante un período de siete años realizamos censos invernales, en cinco ambientes diferentes, de dos migrantes de corta distancia, Catharus guttatus y Dendroica coronata, para determinar si las abundancias locales pueden ser predichas a partir de la biomasa de pulpa de fruto. Los ambientes muestreados fueron plantaciones de especies de madera dura...

For those few bird species that are exclusively frugivorous, the low protein content of fruits is likely a major nutritional constraint. Physiological mechanisms that allow strict frugivory remain enigmatic, but reduced protein requirements may suffice. We investigated protein requirements of Pesquet's Parrot (Psittrichas fulgidus), a highly specia...

La disponibilidad de alimentos durante el invierno puede determinar el uso del hábitat y limitar las poblaciones de aves que permanecen en sus áreas de nidificación durante el invierno. Sin embargo, es difícil determinar su importancia debido a que pocos estudios han evaluado experimentalmente la respuesta de aves no reproductivas a cambios en la a...

Many migrant birds that breed in North and South America overwinter in the tropics of South America. Yet their exact distribution, micro-habitat use, and threats to survival on their win-tering grounds are still poorly understood. Although many use secondary habitats, others require habitats such as native grasslands that are under intense threat o...

A conceptual model of movement ecology has recently been advanced to explain all movement by considering the interaction of four elements: internal state, motion capacity, navigation capacities, and external factors. We modified this framework to generate predictions for species richness dynamics of fragmented plant communities and tested them in e...

Avian incubation behaviour is thought to be influenced mainly by ambient temperature and food availability. Field studies, however, have generated contradictory results; there is little agreement about the relative importance of food and temperature and how different components of incubation behaviour are affected by them. To date, no studies have...

The primary function of fruit is to attract animals that disperse viable seeds, but the nutritional rewards that attract beneficial consumers also attract consumers that kill seeds instead of dispersing them. Many of these unwanted consumers are microbes, and microbial defense is commonly invoked to explain the bitter, distasteful, occasionally tox...

1. Long-distance seed dispersal is difficult to measure, yet key to understanding plant population; dynamics and community composition.; 2. We used a spatially explicit model to predict the distribution of seeds dispersed long distances by; birds into habitat patches of different shapes. All patches were the same type of habitat and size, but; vari...

A fundamental way in which animal-dispersed plants can influence the viability and distribution of dispersed seeds is through control of retention time in the guts of dispersers. Using two species of wild chilies and their dispersers, we examined how chemical and physical properties of fruits and seeds mediate this interaction. Capsicum chacoense i...

Many papers and lesson plans have been published on the value of going outside or "into the field" to teach about topics related to biodiversity (e.g., Zervanos & McLaughlin, 2003; O'Neal & Skelton, 1994; Beiersdorfer & Davis, 1994). However, there has been much less published about effective alternatives, when field trips are not an option. In thi...

The life histories of many species depend first on dispersal to local sites and then on establishment. After dispersal, density-independent and density-dependent mortalities modify propagule supply, determining the number of individuals that establish. Because multiple factors influence recruitment, the dichotomy of propagule versus establishment l...

The chapters of this book on seed dispersal are divided into four parts: (1) frugivores and frugivory (8 chapters); (2) seed and seedling shadows (7 chapters); (3) seed fate and establishment (eight chapters); and (4) management implications and conservation (six chapters). The book presents both recent advances and reviews of current knowledge.

This chapter illustrates using simulations how the assumed Janzen-Connell relationship between distance from parent and seed density can break down. Emphasis is given on spatial patterns of seed dispersal, the resultant spatial structure of seeds and the potential consequences for the population and the community. A special form of dispersal limita...

We examine the relative importance of processes that underlie plant population abundance and distribution. Two opposing views dominate the field. One posits that the ability to establish at a site is determined by the availability of suitable microsites (establishment limitation), while the second asserts that recruitment is limited by the availabi...

Fleshy fruit is a key food resource for both game and nongame wildlife, and it may be especially important for migratory birds during fall and for resident birds and mammals during winter. Land managers need to know how land uses affect the quantities and species of fruit produced in different forest types and how fruit production varies seasonally...

Research to date has demonstrated that bird migration is comprised of highly diverse and plastic behavioural patterns. Our objective is to highlight the importance of studying mechanisms underlying these patterns in austral migrants. We focus on the high incidence of overlap in breeding and non-breeding ranges as a particularly thought-provoking pa...

Research to date has demonstrated that bird migration is comprised of highly diverse and plastic behavioural patterns. Our objective is to highlight the importance of studying mechanisms underlying these patterns in austral migrants. We focus on the high incidence of overlap in breeding and non-breeding ranges as a particularly thought-provoking pa...