I am broadly interested in biodiversity, plant communication and ecological networks. Exploring how life's complexity is maintained in changing environments and the role of networks in ecological systems have been a recurrent aim of my studies.
In particular, my core research is centred around cause-and-effect of networks of species interactions including plants, their neighbours and their mutualistic and antagonistic partners in real-world ecosystems. To answer to these questions, whenever possible, I integrate observations, models and experiments.
My current research focuses on the impact of global change drivers on biotic interactions and species coexistence.
I hope my research output helps society to better manage ecosystems and to design novel solutions for sustainable schemes.
Honors & Awards
Early Postdoc Mobility, Swiss National Science Foundation (2019)
Scientific Exchange fellowship, Swiss National Science Foundation (2018)
Best poster prize, International Plant Science Conference (2014)
Flora award, University of Milan (2012)
FP7 Erasmus, European Union (2010-2011)
Fellowship for talented students, Italian Social Service Foundation (2009-2014)
Boards, Advisory Committees, Professional Organizations
Board committee, Life Science Zurich Graduate School, PhD Program in Ecology (2015 - 2015)
Member, Ecological Society of America (2016 - Present)
Member, British Ecological Society (2015 - Present)
PhD, University of Zurich, Ecology (2017)
MSc, University of Milan, Natural Science (2014)
BSc, University of Milan, Natural Science (2011)
Rodolfo Dirzo, Postdoctoral Faculty Sponsor
Current Research and Scholarly Interests
Disentangling the consequences of deforestation and biodiversity loss for species coexistence, and the role of coexistence mechanisms in mediating ecosystem functioning of forest communities in the tropics.
Combined effects of deforestation and biodiversity loss on species coexistence and ecosystem functioning, Stanford University (1/1/2020 - 6/30/2021)
Human activities are profoundly impacting life on Earth and increasingly threatening the functioning of ecosystems, with severe consequences for human well-being. In particular, recent experimental studies have shown that deforestation and biodiversity loss are disrupting key ecosystem functions on which we rely. Yet, we have a limited understanding of the mechanisms underlying the impact of these major anthropogenic perturbations on the functioning of ecosystems.A possible solution to this problem is to examine how interactions between species in ecological communities which are subject to perturbations influence ecosystem functioning. Modern coexistence theory highlights mechanisms of species interactions responsible for biodiversity maintenance, including niche differences and fitness differences. Nevertheless, we still do not know the consequences of deforestation and biodiversity loss for species coexistence mechanisms nor how these mechanisms influence ecosystem functioning. Understanding the synergistic effects of deforestation and biodiversity loss on species coexistence will provide a mechanistic link between anthropogenic perturbations and ecosystem functioning.Here, I propose a project aimed at disentangling the consequences of deforestation and biodiversity loss for species coexistence, and the role of coexistence mechanisms in mediating ecosystem functioning of forest communities. I plan to establish a new deforestation x biodiversity experiment using the herb layer of Mediterranean and tropical forests as a model system. The experimental design includes plant communities with different levels of species richness in the herb layer. I will manipulate plant species richness by sowing seeds from a pool of four herbaceous species. This will ensure that I capture the majority of biodiversity effects on biomass productivity that are expressed by just moving from monoculture to few-species mixture. Plant communities will be assembled using native herbs in forested and deforested ecosystems in Mediterranean (California) and tropical (Mexico) climates in two field stations owned by the host and collaborating institutions. This design will allow me to assess the direct and combined effects of deforestation and biodiversity loss on the herb layer of forest communities in contrasting climates. I will carry out two sets of independent but complementary studies within this experimental framework.First, I will test the consequences of deforestation and biodiversity loss of herbs for species coexistence using state-of-the-art ecological models.Second, I will examine the role of coexistence mechanisms in mediating the effects of deforestation and biodiversity loss on ecosystem functioning, such as biomass productivity and reproductive potential of herbs.Evidence of these hypothesised synergistic effects of deforestation and biodiversity loss on species coexistence and of the role of coexistence mechanisms in mediating ecosystem functioning would be the first in ecological literature. Addressing these questions will fill a key knowledge gap in understanding the impact of human activities on ecosystem functioning via their effects on species coexistence.
- Rodolfo Dirzo, Bing Prof in Environmental Science and Senior Fellow at the Woods Institute for the Environment, Stanford University
Revisiting local adaptation to climate change 90 years after, Stanford University (5/2020 - 6/2021)
The California Sierra Nevada is legendary for its biodiversity and cultural and scientific heritage. However, ongoing climate change poses serious threats to the conservation and sustainability of these environments.
This research project involves revisiting the famous studies of local adaptation initiated by Dr. H. M. Hall in the 1920’s and continued by California botanists Jens C. Clausen, William M. Hiesey, and David D. Keck in the 30’s. They showed, for the first time in history, how species evolve and locally adapt to different environments. In particular, they recorded the occurrence and phenotype of the same species (common yarrow, Achillea millefolium) across a broad climatic gradient ranging from the coast (Bodega Bay) to the basin (Lee Vining) passing through Yosemite. By growing plants from seeds in a common garden at Stanford, they then demonstrated how plants evolved to different environmental conditions and posed locally adapted genes – some years before the actual discovery of DNA.
The purpose of this study is to revisit the study of Hall, Clausen and colleagues 90 years after, which means in climatic and environmental conditions remarkably different than 90 years ago. Our objective is to examine how evolution and local adaptation changed during this last century of changing climate conditions. We will do so by comparing current results with data published by Clausen and colleagues.
The outcome of this research will help us understand plants’ evolutionary response to climate change.
- Rodolfo Dirzo, Prof., Stanford University
Network motifs involving both competition and facilitation predict biodiversity in alpine plant communities.
Proceedings of the National Academy of Sciences of the United States of America
2021; 118 (6)
Biological diversity depends on multiple, cooccurring ecological interactions. However, most studies focus on one interaction type at a time, leaving community ecologists unsure of how positive and negative associations among species combine to influence biodiversity patterns. Using surveys of plant populations in alpine communities worldwide, we explore patterns of positive and negative associations among triads of species (modules) and their relationship to local biodiversity. Three modules, each incorporating both positive and negative associations, were overrepresented, thus acting as "network motifs." Furthermore, the overrepresentation of these network motifs is positively linked to species diversity globally. A theoretical model illustrates that these network motifs, based on competition between facilitated species or facilitation between inferior competitors, increase local persistence. Our findings suggest that the interplay of competition and facilitation is crucial for maintaining biodiversity.
View details for DOI 10.1073/pnas.2005759118
View details for PubMedID 33526655
- Facilitation and biodiversity jointly drive mutualistic networks JOURNAL OF ECOLOGY 2021
- The Consequences of Glacier Retreat Are Uneven Between Plant Species FRONTIERS IN ECOLOGY AND EVOLUTION 2021; 8
Invasive species allelopathy decreases plant growth and soil microbial activity.
2021; 16 (2): e0246685
According to the 'novel weapons hypothesis', invasive success depends on harmful plant biochemicals, including allelopathic antimicrobial roots exudate that directly inhibit plant growth and soil microbial activity. However, the combination of direct and soil-mediated impacts of invasive plants via allelopathy remains poorly understood. Here, we addressed the allelopathic effects of an invasive plant species (Rhus typhina) on a cultivated plant (Tagetes erecta), soil properties and microbial communities. We grew T. erecta on soil samples at increasing concentrations of R. typhina root extracts and measured both plant growth and soil physiological profile with community-level physiological profiles (CLPP) using Biolog Eco-plates incubation. We found that R. typhina root extracts inhibit both plant growth and soil microbial activity. Plant height, Root length, soil organic carbon (SOC), total nitrogen (TN) and AWCD were significantly decreased with increasing root extract concentration, and plant above-ground biomass (AGB), below-ground biomass (BGB) and total biomass (TB) were significantly decreased at 10 mg·mL-1 of root extracts. In particular, root extracts significantly reduced the carbon source utilization of carbohydrates, carboxylic acids and polymers, but enhanced phenolic acid. Redundancy analysis shows that soil pH, TN, SOC and EC were the major driving factors of soil microbial activity. Our results indicate that strong allelopathic impact of root extracts on plant growth and soil microbial activity by mimicking roots exudate, providing novel insights into the role of plant-soil microbe interactions in mediating invasion success.
View details for DOI 10.1371/journal.pone.0246685
View details for PubMedID 33561161
An experimental approach to assessing the impact of ecosystem engineers on biodiversity and ecosystem functions.
Plants acting as ecosystem engineers create habitats and facilitate biodiversity maintenance within plant communities. Furthermore, biodiversity research has demonstrated that plant diversity enhances the productivity and functioning of ecosystems. However, these two fields of research developed in parallel and independent from one another, with the consequence that little is known about the role of ecosystem engineers in the relationship between biodiversity and ecosystem functioning across trophic levels. Here, we present an experimental framework to study this relationship. We combine facilitation by plants acting as ecosystem engineers with plant-insect interaction analysis and variance partitioning of biodiversity effects. We present a case-study experiment in which facilitation by a cushion-plant species and a dwarf-shrub species as ecosystem engineers increases positive effects of plant functional diversity (ecosystem engineers and associated plants) on ecosystem functioning (flower visitation rate). The experiment, conducted in the field during a single alpine flowering season, included the following treatments: 1) removal of plant species associated with ecosystem engineers, 2) exclusion (covering) of ecosystem engineer flowers, and 3) control, i.e. natural patches of ecosystem engineers and associated plant species. We found both positive and negative associational effects between plants depending on ecosystem engineer identity, indicating both pollination facilitation and interference. In both cases patches supported by ecosystem engineers increased phylogenetic and functional diversity of flower visitors. Furthermore, complementarity effects between engineers and associated plants were positive for flower visitation rates. Our study reveals that plant facilitation can enhance the strength of biodiversity-ecosystem functioning relationships, with complementarity between plants for attracting more and diverse flower visitors being the likely driver. A potential mechanism is that synergy and complementarity between engineers and associated plants increase attractiveness for shared visitors and widen pollination niches. In synthesis, facilitation among plants can scale up to a full network, supporting ecosystem functioning both directly via microhabitat amelioration and indirectly via diversity effects.
View details for DOI 10.1002/ecy.3243
View details for PubMedID 33190225
- Molecular Ecological Network Analyses: An Effective Conservation Tool for the Assessment of Biodiversity, Trophic Interactions, and Community Structure FRONTIERS IN ECOLOGY AND EVOLUTION 2020; 8
- Foundation species promote local adaptation and fine-scale distribution of herbaceous plants JOURNAL OF ECOLOGY 2020
- The assembly of plant-patch networks in Mediterranean alpine grasslands JOURNAL OF PLANT ECOLOGY 2020; 13 (3): 273–80
- Pollination interactions reveal direct costs and indirect benefits of plant-plant facilitation for ecosystem engineers JOURNAL OF PLANT ECOLOGY 2020; 13 (1): 107–13
- Perspectives for ecological networks in plant ecology PLANT ECOLOGY & DIVERSITY 2019; 12 (2): 87–102
- Facilitation mediates species presence beyond their environmental optimum PERSPECTIVES IN PLANT ECOLOGY EVOLUTION AND SYSTEMATICS 2019; 38: 24–30
Plant interactions shape pollination networks via nonadditive effects
2019; 100 (3): e02619
Plants grow in communities where they interact with other plants and with other living organisms such as pollinators. On the one hand, studies of plant-plant interactions rarely consider how plants interact with other trophic levels such as pollinators. On the other, studies of plant-animal interactions rarely deal with interactions within trophic levels such as plant-plant competition and facilitation. Thus, to what degree plant interactions affect biodiversity and ecological networks across trophic levels is poorly understood. We manipulated plant communities driven by foundation species facilitation and sampled plant-pollinator networks at fine spatial scale in a field experiment in Sierra Nevada, Spain. We found that plant-plant facilitation shaped pollinator diversity and structured pollination networks. Nonadditive effects of plant interactions on pollinator diversity and interaction diversity were synergistic in one foundation species networks while they were additive in another foundation species. Nonadditive effects of plant interactions were due to rewiring of pollination interactions. In addition, plant facilitation had negative effects on the structure of pollination networks likely due to increase in plant competition for pollination. Our results empirically demonstrate how different network types are coupled, revealing pervasive consequences of interaction chains in diverse communities.
View details for DOI 10.1002/ecy.2619
View details for Web of Science ID 000460163500012
View details for PubMedID 30636292
- Flower-power: Flower diversity is a stronger predictor of network structure than insect diversity in an Arctic plant-pollinator network ECOLOGICAL COMPLEXITY 2018; 36: 1–6
- The assembly of a plant network in alpine vegetation JOURNAL OF VEGETATION SCIENCE 2018; 29 (6): 999–1006
- Plant life history stage and nurse age change the development of ecological networks in an arid ecosystem OIKOS 2018; 127 (9): 1390–97
Effects of nitrogen deposition on soil microbial communities in temperate and subtropical forests in China
SCIENCE OF THE TOTAL ENVIRONMENT
2017; 607: 1367–75
Increasing nitrogen (N) deposition has aroused large concerns because of its potential negative effects on forest ecosystems. Although microorganisms play a vital role in ecosystem carbon (C) and nutrient cycling, the effect of N deposition on soil microbiota still remains unclear. In this study, we investigated the responses of microbial biomass C (MBC) and N (MBN) and microbial community composition to 4-5years of experimentally simulated N deposition in temperate needle-leaf forests and subtropical evergreen broadleaf forests in eastern China, using chloroform fumigation extraction and phospholipid fatty acid (PLFA) methods. We found idiosyncratic effects of N addition on microbial biomass in these two types of forest ecosystems. In the subtropical forests, N addition showed a significant negative effect on microbial biomass and community composition, while the effect of N addition was not significant in the temperate forests. The N addition decreased MBC, MBN, arbuscular mycorrhizal fungi, and the F/B ratio (ratio of fungi to bacteria biomass) in the subtropical forests, likely due to a decreased soil pH and changes in the plant community composition. These results showed that microbial biomass and community composition in subtropical forests, compared with the temperate forests, were sensitive to N deposition. Our findings suggest that N deposition may have negative influence on soil microorganisms and potentially alter carbon and nutrient cycling in subtropical forests, rather than in temperate forests.
View details for DOI 10.1016/j.scitotenv.2017.06.057
View details for Web of Science ID 000408755300136
View details for PubMedID 28738512
- Life in harsh environments: carabid and spider trait types and functional diversity on a debris-covered glacier and along its foreland ECOLOGICAL ENTOMOLOGY 2017; 42 (6): 838–48
- Resistance of plant-plant networks to biodiversity loss and secondary extinctions following simulated environmental changes FUNCTIONAL ECOLOGY 2017; 31 (5): 1145–52
- Feedback effects between plant and flower-visiting insect communities along a primary succession gradient ARTHROPOD-PLANT INTERACTIONS 2016; 10 (6): 485–95
- Structure-dynamic relationship of plant-insect networks along a primary succession gradient on a glacier foreland ECOLOGICAL MODELLING 2015; 314: 73–79