Nacho Villar

Dr. Nacho Villar

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Visiting Address

Droevendaalsesteeg 10
6708 PB Wageningen

+31 (0) 317 47 34 00

The Netherlands


I study how large wildlife enginyeer Ecosystems and regulate Ecological dynamics, Trophic cascades, Community assembly and Zoogeochemistry in different ecosystems (grasslands, tropical forests & wetlands) and how Rewilding can help to Restore ecosystems.


I have a long-standing interest in understanding how ecological systems assemble and self-organize in order to persist, the feedback and coevolutive processes involved, and the ecological dynamics that emerge from these. I am also interested in developing a robust evidence-based science of Rewilding underpinned by this knowledge. I approach this broad theme by deciphering the impact of large wildlife on the structure and dynamics of ecosystems. In my research I have investigated how wildlife impacts on diversity and community assembly over time and space, niche partitioning and coexistence of plant communities, and their resilience to global change; how it affects the regulation of demography and population dynamics of other consumers and its cascading effects; and how it shapes above-belowground processes, nutrient cycles, carbon stocks and spatial subsidies, to name a few processes. I collaborate in a number of international projects and networks and supervise early stage researchers in relation to these research lines.

Research groups


Peer-reviewed publications

  • Journal of Ecology

    The interplay between defaunation and phylogenetic diversity affects leaf damage by natural enemies in tropical plants

    Carine Emer, Nacho Villar, Natália Melo, Valesca B. Ziparro, Sergio Nazareth, Mauro Galetti

    Natural enemies play an important role in controlling plant population growth and vegetation dynamics. Tropical rainforests host the greatest diversity of herbivores, from large mammalian ungulates to microscopic pathogens, generating and maintaining plant diversity. By feeding on the same resources, large mammalian herbivores may interfere with plant consumption and leaf damage by important enemy guilds such as invertebrate herbivores and pathogens, triggering indirect trophic cascades. However, the impact of local extinctions of large herbivores on plant–enemy interactions is relatively unknown. We experimentally tested the effects of defaunation of large mammalian herbivores (e.g. peccaries, tapirs and brocket deer; hereafter, large herbivores) on the leaf damage of 3350 understorey plants in tropical rainforests of Brazil. We examined leaf damage in 10,050 leaves from 333 morphospecies by assigning the area consumed or damaged by five guilds of insect herbivores and leaf pathogens within 86 paired open-closed plots and investigating the joint effects of defaunation and plant phylogenetic diversity. Plants released from large herbivores had 9% less leaf damage; this difference was due to the lower leaf pathogens incidence (29%) rather than insect herbivory. Evolutionary distinctness was positively correlated with leaf damage in a similar way in all treatments, suggesting additive effects of defaunation and phylogenetic diversity. Total and pathogenic leaf damage (but not insect damage) decreased with plant richness across treatments, and large herbivores exclusion resulted in increased plant species richness. This suggests that large herbivores exclusion leads to a dilution of total and pathogens' leaf damage by increasing plant species richness. Our results suggest that indirect effects of large herbivores decrease the dilution potential of plant communities against pathogens and rather reinforce their top-down impact on vegetation, demonstrating a previously overlooked cascading effect of large herbivore extinction on forest ecosystems. Synthesis: The extinction of large mammalian herbivores can lead to a decrease in pathogen-driven leaf damage, a previously unknown indirect effect in forest ecosystems, which might have consequences for plant fitness and ultimately for plant diversity. Large herbivores and plant pathogens might have synergistic effects in regulating the diversity of plant communities in some of the most diverse ecosystems on Earth.
  • Oikos

    A Seed Dispersal Effectiveness framework across the mutualism-antagonism continuum

    Casper van Leeuwen, Nacho Villar, I. Mendoza-Sagrera, Andy J. Green, (Liesbeth) E.S. Bakker, Merel Soons, Mauro Galetti, Patrick A. Jansen, Bart A. Nolet, Luis Santamaría
    Many angiosperms rely on vertebrates for seed dispersal via gut passage, an interaction that has been traditionally classified as a mutualism. The seed dispersal effectiveness (SDE) framework provides a mechanistic approach to evaluate evolutionary and ecological characteristics of animal-mediated seed dispersal, by synthesising the quantity and the quality of the dispersal that a plant species receives from each of its animal dispersers. However, the application of the SDE framework has been largely restricted to plant–frugivore interactions, whereas animal-mediated seed dispersal results from plant–disperser interactions that cover a continuum from pure mutualisms to antagonisms. This biases ecological and evolutionary knowledge on plant–disperser interactions. Here, we propose an extended SDE framework (‘eSDE') that allows comparing plant–disperser interactions in the full mutualism–antagonism continuum ranging from pure mutualisms (frugivores) to conditional mutualisms (scatter-hoarding granivores and folivores) and antagonisms (pure granivores). We present the eSDE framework, and use examples to illustrate how it can be applied to compare effectiveness among plant–disperser interaction types. Our initial comparison based on available data suggests that vertebrate species differ more in the number of seeds they deposit away from the mother plant (quantity), than in the effects such dispersal processes have on seed fate (quality). Scatter-hoarding granivores provide the most effective dispersal due to high removal rates, closely followed by frugivores due to high deposition rates. Folivores and pure granivores provide low quantity dispersal, but of high and moderate quality, respectively. These early comparative insights illustrate the necessity and usefulness of more standardized data collection protocols, for which we provide recommendations. Applying the eSDE framework can reveal broad-scale patterns across and within plant–disperser interaction types, which will advance our evolutionary understanding of plant–animal interactions. This will provide new insights into the consequence of anthropogenic impacts on vertebrate-mediated seed dispersal in a world in which plant–animal interactions are increasingly threatened.
  • Perspectives in Ecology and Conservation

    Large herbivore-palm interactions modulate the spatial structure of seedling communities and productivity in Neotropical forests

    Nacho Villar, Fabiana Rocha-Mendes, Roger Guevara, Mauro Galetti

    Top-down control by large herbivores is a well-known driver of plant diversity structure and productivity. Yet, for forest ecosystems the sign and magnitude of herbivore control across resource gradients is not well understood. We conducted a series of replicated large herbivore exclusion experiments in defaunated and non-defaunated Atlantic forests of Brazil to evaluate the effects of large herbivores on tropical plant communities. We hypothesized that the top-down impact of large herbivores on seedling recruitment, species richness, diversity and productivity would change across a natural gradient in the density of a key plant resource, the palm Euterpe edulis, which is thought to act as a foundation species. We found both positive (agonistic) and negative (antagonistic) spatially-structured effects of large herbivores on plant communities driven by an interaction between large herbivores and palm density on non-defaunated sites, but not on defaunated sites. Indeed, through its interaction with large herbivores, palm trees were able to regulate the spatial structure of seedling communities. In the non-defaunated forest, the negative impact of large herbivores on plant recruitment and species richness decreased substantially as palms became more abundant and canopy cover decreased. Furthermore, large herbivores caused a 185% increase but a 194% decrease in aboveground seedling productivity in areas of high and low palm density, respectively. In contrast, in the defaunated forest we did not find any consistent large herbivore impacts on plant recruitment or species richness across the gradient of palm density, and herbivore activity consistently had negative effects on seedling productivity. Analyses using camera trap data indicate that white-lipped peccaries (Tayassu peccari) played a key role in modulating recruitment and seedling productivity, while tapirs (Tapirus terrestris) contributed significantly to an increase in plant diversity, hence playing a functionally complementary role. Our results demonstrate that a key interaction between large forest-dwelling tropical herbivores and their palm resource results in landscape-scale modulation of plant communities through positive and negative spatially-structured feedbacks, and support the view that palms might act as foundation species in tropical forests. Anthropogenic pressures posed by defaunation and illegal palm harvesting in the Neotropics might lead to the functional loss of this interaction and the collapse of the spatial structure along palm density gradients, with cascading effects on the dynamics and productivity of tropical forests.
  • Journal of Ecology

    Large mammalian herbivores modulate plant growth form diversity in a tropical rainforest

    Yuri Souza, Nacho Villar, Valesca Zipparro, Sergio Nazareth, Mauro Galetti

    The world’s terrestrial biomes are broadly classified according to the dominant plant growth forms that define ecosystem structure and processes. Although the abundance and distribution of different plant growth forms can be strongly determined by factors such as climate and soil composition, large mammalian herbivores have a strong impact on plant communities, thus defaunation (the local or functional extinction of large animals) has the potential to alter the compositional structure of plant growth forms in natural ecosystems. Tropical rainforests sustain a high diversity of growth forms, including trees, palms, lianas, shrubs, herbs and bamboos, all of which play important ecosystem functions. Here, we experimentally evaluate how large mammalian herbivores affect the dominance, diversity and coexistence of these major tropical forest plant growth forms, by monitoring communities of saplings on the understorey in 43 paired exclusion plots in a long-term replicated exclusion experiment in the understorey of the Atlantic forest of Brazil. Over the course of 10 years large herbivore exclusion decreased diversity among growth forms, increased the absolute abundance of palms and trees (22% and 38% respectively) and increased the diversity of species within these two groups, to the detriment of other growth forms. Furthermore, all pairwise relationships between growth forms were positive on plots where herbivores had access, whereas several strong negative relationships emerged in plots where herbivores were excluded. This occurred despite strong background directional temporal trends affecting plant communities in both experimental treatments across the region. Synthesis. Our work indicates that the defaunation alters growth form dominance by favouring palms and trees while eroding diversity among growth forms and coexistence on a temporal scale. Large herbivore mammals promote diversity among growth forms, preventing the hyper-dominance of trees and palms, yet without supressing the diversity of species within growth forms. We argue that large herbivore mammals affect growth forms through several non-mutually exclusive mechanisms, including herbivory, seed dispersal and physical disturbance, as well as differential effects linked to the morphological and physiological adaptations of growth forms. We conclude that defaunation might lead to profound impacts on important ecosystem functions underpinned by growth form diversity, and result in vertical and horizontal structural simplification of tropical rainforests.
  • Animal Conservation

    Dietary expansion facilitates the persistence of a large frugivore in fragmented tropical forests

    Marcelo Magioli, Nacho Villar, Maria Luisa Jorge, Cibele Biondo, Alexine Keuroghlian, Jennifer Bradham, Felipe Pedrosa, Vladimir Costa, Marcelo Zacharias Moreira, Katia Maria Paschoaletto Micchi de Barros Ferraz, Mauro Galetti

    How species persist in fragmented habitats is essential to understanding species resilience in response to increasing anthropogenic pressures. It has been suggested that expansion in dietary niche allows populations to persist in human-modified landscapes, yet this hypothesis has been poorly tested in highly diverse ecosystems such as tropical forests where frugivory is ubiquitous. Here, we measured dietary niche expansion of a large forest-dwelling mammal, the white-lipped peccary (Tayassu pecari), in the Atlantic Forest, Brazil, by comparing its diet using stable carbon (δ13C) and nitrogen (δ15N) isotopes. We collected hair of white-lipped peccaries in three continuous and three fragmented forests and compared δ13C and δ15N values, resource use and isotopic niches among populations and between forest types. We also tested the relationship between isotopic values of the populations and the forest cover percentage. White-lipped peccaries fed mainly on forest sources (C3 resources), especially in continuous forests, but 28% of the individuals in fragmented sites also incorporated C4 resources to some extent. In fragmented forests, the populations had isotopic niches from 3- to 3.6-fold the size of those in continuous forests. This niche expansion was due to the consumption of food items with higher δ15N values and C4 crops. Differences among populations were larger among fragmented forests, suggesting variable site-specific strategies to cope with habitat loss. The mean isotopic values of white-lipped peccary populations were negatively correlated with the loss of forest cover. Some small forest fragments might still retain relatively high habitat quality, and white-lipped peccaries might be able to capitalize on such variety of resources, shifting their diets from those observed in continuous forests. We suggest that high dietary flexibility and dietary expansion toward consumption of non-forest resources might facilitate the persistence of large frugivores in fragmented habitats.
  • Journal of Applied Ecology

    Large wild herbivores slow down the rapid decline of plant diversity in a tropical forest biodiversity hotspot

    Nacho Villar, Emilia Patricia Medici

    The UN declaration of the Decade of Ecosystem Restoration 2021–2030 emphasizes the need for effective measures to restore ecosystems and safeguard biodiversity. Large herbivores regulate many ecosystem processes and functions; yet, their potential as a nature-based solution to buffer against long-term temporal declines in biodiversity associated with global change and restore diversity in secondary forests remains unknown. By means of an exclusion experiment, we tested experimentally the buffering effects of large wild herbivores to avert against long-term biodiversity collapse in old-growth and secondary tropical forests in the Atlantic Forest of Brazil where sapling abundance and species richness declined c. 20% over the course of 10 years. The experiment comprised 50 large herbivore exclosure-open control plot pairs (25 at the old-growth forest and 25 at the secondary forest), where 2 m2 were monitored in every plot during a 10-year period. Large herbivores were able to decelerate diversity declines and compositional change in the species-rich old-growth forest, but only decelerated compositional change in the secondary forest. In contrast, declines in species richness and abundance were unaffected by large herbivores on either forest. The buffering effects of large herbivores were strongly nonlinear and contingent on the initial level of diversity at the patch scale: highly diverse communities suffered the strongest collapse in the absence of large herbivores. Thus, larger buffering effects of large herbivores on the old-growth forest are the logical consequence of large herbivores buffering the many high diversity plant communities found in this forest. Conversely, as the secondary forest held fewer high diversity patches, buffering effects on the secondary forest were weak. Synthesis and applications. Our study indicates that large herbivores have moderate yet critical effects on slowing down community change and diversity loss of highly diverse plant communities, thus suggesting that the conservation of (and potentially trophic rewilding with) large herbivores is a fundamental nature-based solution for averting the global collapse of the strongholds of biodiversity. Its buffering effects on biodiversity loss operate at very small spatial scales, are likely contingent on successional stage and are most effective in old-growth or high diversity secondary forests.
  • Functional Ecology

    Frugivory underpins the nitrogen cycle

    Nacho Villar, Claudia Paz, Valesca Zipparro, Sergio Nazareth, Leticia Bulascoschi, (Liesbeth) E.S. Bakker, Mauro Galetti

    Tropical rainforests are populated by large frugivores that feed upon fruit-producing woody species, yet their role in regulating the cycle of globally important biogeochemical elements such as nitrogen is still unknown. This is particularly relevant because tropical forests play a prominent role in the nitrogen cycle and are becoming rapidly defaunated. Furthermore, frugivory is not considered in current plant-large herbivore-nutrient cycling frameworks exclusively focused on grazers and browsers. Here we used a long-term replicated paired control-exclusion experiment in the Atlantic Forest of Brazil, where peccaries and tapirs are the largest native frugivores, to examine the impact of large ground-dwelling frugivores on modulating soil nitrogen cycling, considering their effects across a gradient of abundance of a hyper-dominant palm. We found that both large frugivores and dominant palms play a substantial role in modulating ammonium availability and nitrification rates. Large frugivores increased ammonium by 95%, which also increased additively with palm abundance. Nitrification rates increased with palm abundance in the presence of large frugivores, but not on exclosure plots. Large frugivores also stimulated the regulation of the functions of soil-nitrifying microorganisms, and modulated the landscape-scale variance in nitrogen availability. Such joint effects of large frugivores and palms are consistent with the notion of ‘fruiting lawns’. Our study indicates that frugivory plays a pivotal role in zoogeochemistry in tropical forests by regulating and structuring the nitrogen cycle, urging to accommodate frugivory in plant-large herbivore-nutrient cycling frameworks. It also indicates that defaunation, deforestation and illegal palm and timber harvesting seriously affect nitrogen cycling in tropical forests, that play a prominent role in the global cycle of this nutrient. A free Plain Language Summary can be found within the Supporting Information of this article.
  • 2021

    Causes and Consequences of Large-Scale Defaunation in the Atlantic Forest

    Mauro Galetti, Fernando Gonçalves, Nacho Villar, Valesca Zipparro, Claudia Paz, Calebe P. Mendes, Laís Lautenschlager, Yuri Souza, Paula Akkawi, Felipe Pedrosa, Leticia Bulascoschi, Carolina Bello, Anaiá P. Sevá, Lilian Sales, Luisa Genes, Fernanda Delborgo Abra, Ricardo Bovendorp
    The Atlantic Forest of South America hosts one of the world’s most diverse and threatened tropical forest biota. After five centuries of European human expansion, most Atlantic Forest landscapes are archipelagos of small forest fragments surrounded by open-habitat matrices. In this chapter, we describe the causes and consequences of large-scale defaunation in the Atlantic Forest of South America. We identify and quantify the magnitude of the main anthropogenic drivers of defaunation and stimulate a debate on how to revert the loss of fauna to restore biodiversity and ecosystem functions and services. The magnitude of the impact of defaunation in the Atlantic Forest is hard to estimate, but we can predict that, at large scale, habitat loss, fragmentation, and degradation are the most common threats to terrestrial populations. Other threats vary in importance according to the taxonomic group. In general, apex predators, other carnivores, large-bodied mammals, and large herbivores were among the most defaunated functional groups and the loss of these animals has also a strong impact on the ecosystem services. Given the extent of the consequences of defaunation in the Atlantic Forest, mitigation strategies are imperative. Habitat restoration would clearly be effective in building space for defaunation mitigation but reversing the pervasive defaunation that occurred in the Atlantic Forest is by no means a straightforward task. Nonetheless, it will be fundamental to assure the persistence of the biodiversity in the Atlantic Forest remnants.

Projects & collaborations