Tree diversity effects on herbivores and tri-trophic interactions
Since 2010, we established and have been working in a tree diversity experiment found in southern Yucatan, México (http://www.treedivnet.ugent.be/ExpUADY.html). This system is composed of monocultures (of one species) and polycultures (of 4 species) of six tropical tree species. One of the selected species is big-leaf mahogany (Swietenia macrophylla) for which we additionally established monocultures of one and four (out of six possible) genotypes, and these two levels of genotype diversity are replicated at both high and low tree species diversity. Our goal in this project is to evaluate the effects of tree species diversity and genotypic diversity on interactions between trees and different guilds of insect herbivores as well as their invertebrate (e.g. spiders, parasitoids) and vertebrate (birds) predators. To this end, we have been collaborating with Kailen Mooney (UC-Irvine) and Xoaquín Moreira (Misión Biológica de Galicia).
Since 2010, we established and have been working in a tree diversity experiment found in southern Yucatan, México (http://www.treedivnet.ugent.be/ExpUADY.html). This system is composed of monocultures (of one species) and polycultures (of 4 species) of six tropical tree species. One of the selected species is big-leaf mahogany (Swietenia macrophylla) for which we additionally established monocultures of one and four (out of six possible) genotypes, and these two levels of genotype diversity are replicated at both high and low tree species diversity. Our goal in this project is to evaluate the effects of tree species diversity and genotypic diversity on interactions between trees and different guilds of insect herbivores as well as their invertebrate (e.g. spiders, parasitoids) and vertebrate (birds) predators. To this end, we have been collaborating with Kailen Mooney (UC-Irvine) and Xoaquín Moreira (Misión Biológica de Galicia).
Volatile-mediated signalling and induced defences in wild cotton
We are studying variation in defensive traits and herbivory in wild cotton (Gossypium hirsutum) populations in the coastal shrubland of Yucatán. Specifically, we are addressing different sources of variation within and across populations in traits associated with direct (e.g. trichomes, terpenoids, phenolics) and indirect (e.g. volatiles, extrafloral-nectaries) defence. These sources include endogenous plant defensve trade-offs as well as other sources of co-variation in defensive trais, as well as extrinsic variation in biotic (herbivory, predation) and abiotic (climatic variables, nutrients) factors. In addition, we are also studying the role of wild cotton in mediating interactions between insect herbivores (e.g. caterpillars, aphids) and pathogens (fungi), and volatile-mediated communication among plants in collaboration with Ted Turlings (University of Neuchâtel).
We are studying variation in defensive traits and herbivory in wild cotton (Gossypium hirsutum) populations in the coastal shrubland of Yucatán. Specifically, we are addressing different sources of variation within and across populations in traits associated with direct (e.g. trichomes, terpenoids, phenolics) and indirect (e.g. volatiles, extrafloral-nectaries) defence. These sources include endogenous plant defensve trade-offs as well as other sources of co-variation in defensive trais, as well as extrinsic variation in biotic (herbivory, predation) and abiotic (climatic variables, nutrients) factors. In addition, we are also studying the role of wild cotton in mediating interactions between insect herbivores (e.g. caterpillars, aphids) and pathogens (fungi), and volatile-mediated communication among plants in collaboration with Ted Turlings (University of Neuchâtel).
Seedling density- and frequency-dependent effects on herbivores and pathogens
Herbivores are key drivers of plant population dynamics and species diversity, and have especially strong effects in tropical forests. Theory predicts that herbivory should increase with both density and frequency of host plants, thus keeping in check abundant species and promoting tree diversity. Unfortunately, studies have overwhelmingly addressed density effects without controlling for frequency, thus limiting our understanding of the relative contributions of these factors. To address this, we are studying the effects of host plant density (number of seedlings per unit of area) and relative frequency (how common one species is relative to other species) on insect herbivores and plant pathogens. We are working in two systems, the UADY Tree Diversity experiment (see above) manipulating mahogany (S. macrophylla) seedling density in 1 by 1 m plots across levels of plant diversity, and the San Nicolás Reserve in collaboration with Jorge Berny and Cinthia Wilber from CEAPY where we established plots varying in the density and relative frequency of four tree species (Cordia dodecandra, Piscidia piscipula, Brosimum alicastrum, and Manilkara zapota) which are an important food source for local fauna as well as timber species.
Seedling density- and frequency-dependent effects on herbivores and pathogens
Herbivores are key drivers of plant population dynamics and species diversity, and have especially strong effects in tropical forests. Theory predicts that herbivory should increase with both density and frequency of host plants, thus keeping in check abundant species and promoting tree diversity. Unfortunately, studies have overwhelmingly addressed density effects without controlling for frequency, thus limiting our understanding of the relative contributions of these factors. To address this, we are studying the effects of host plant density (number of seedlings per unit of area) and relative frequency (how common one species is relative to other species) on insect herbivores and plant pathogens. We are working in two systems, the UADY Tree Diversity experiment (see above) manipulating mahogany (S. macrophylla) seedling density in 1 by 1 m plots across levels of plant diversity, and the San Nicolás Reserve in collaboration with Jorge Berny and Cinthia Wilber from CEAPY where we established plots varying in the density and relative frequency of four tree species (Cordia dodecandra, Piscidia piscipula, Brosimum alicastrum, and Manilkara zapota) which are an important food source for local fauna as well as timber species.
Tri-trophic interactions and indirect defenses in agricultural systems
The effects producer bottom-up and consumer top-down effects may be particularly amenable for study in agricultural systems because of their simplified nature and due to high phenotypic divergence between plant types (e.g. genotypes, varieties) which may result in strong plant bottom-up effects. In this sense, we seek to determine how genetically based variation in crop traits influences insect herbivores and their natural enemies, as well as the potential for natural enemy effects to feed back and influence crop yield (thus informing breeding and pest control strategies). To do so, we have conducted greenhouse and field studies to evaluate the effects of plant genotype, as well as plant intra- (genotype) and inter-specific (species) diversity on tri-trophic interactions. These studies involve detailed examinations of plant traits that influence natural enemies and thus mediate plant indirect defenses against herbivores. An example of this is work on arthropod interactions associated to peppers (Capsicum spp.) in collaboration with Jorge Berny.
The effects producer bottom-up and consumer top-down effects may be particularly amenable for study in agricultural systems because of their simplified nature and due to high phenotypic divergence between plant types (e.g. genotypes, varieties) which may result in strong plant bottom-up effects. In this sense, we seek to determine how genetically based variation in crop traits influences insect herbivores and their natural enemies, as well as the potential for natural enemy effects to feed back and influence crop yield (thus informing breeding and pest control strategies). To do so, we have conducted greenhouse and field studies to evaluate the effects of plant genotype, as well as plant intra- (genotype) and inter-specific (species) diversity on tri-trophic interactions. These studies involve detailed examinations of plant traits that influence natural enemies and thus mediate plant indirect defenses against herbivores. An example of this is work on arthropod interactions associated to peppers (Capsicum spp.) in collaboration with Jorge Berny.
Ecological gradients in species interactions
Species interactions exhibit widespread variability across space, particularly across gradients in biotic or abiotic factors. Disentangling these sources of variation is key to understand the mechanisms that govern species interactions and their impacts on communities and ecosystems. To this end, we have been studying latitudinal and elevational gradients in herbivory and plant defences, as well as tri-trophic interactions (e.g., parasitoid attack) in both temperate and tropical systems, ranging from trees (e.g., oaks) to shrubs (e.g, wild cotton) and herbs, with the ultimate goal of identifying key drivers and commonalities in mechanisms across species and systems. Much of this work has been in collaboration with Xoaquín Moreira (Misión Biológica de Galicia).
Effects of insularity on species interactions
Islands provide singular and yet powerful natural settings for testing ecological and evolutionary hypotheses and have been particularly informative for disentangling the drivers and consequences of species interactions. Within this context, we have focused mainly on island-to-island and mainland-island comparisons of plant defences and herbivory, and have recently incorporated tests of variation in predation (by birds). This work is part of an ongoing collaboration with Xoaquín Moreira (Misión Biológica de Galicia).
Other ongoing projects/topics
Other ongoing projects/topics
- Plant defence syndromes and ontogenetic variation in defences.
- Effects of urbanization on species interactions and traits.
- Evolutionary ecology of plant reproductive synchrony (e.g. masting) and plant-animal interactions.