Explaining biodiversity through speciation

I investigate avian speciation through 1) observational data on acoustic variation and ecological selection pressures and 2) experimental data from playback trials in the field. Different environments and ecological gradients can cause divergence between different populations of the same or related bird species. In such cases, habitat-dependent variation in communication signals and responsiveness can play an important role in the emergence, persistance, or merging of species. My research thereby provides insight into the ecological distribution and evolutionary engine of current biodiversity. 

Explaining impact on biodiversity from pollution

I investigate behavioural effects of noise pollution on terrestrial and aquatic animals. Elevated sound levels due to human activities can harm and harrass. Noise pollution may disturb, deter and distract, as well as mask critically important signals and cues. The behavioural effects vary per species and context and depend on the type of noise and background. Furthermore, translation from individual effects to the population level requires insight into immediate and long-term effects on vital rates like growth, maturation, survival and reproduction. These studies help to understand distribution and density of local biodiversity and provide insight into mitigation potential.    

Investigating biodiversity and conservation in Suriname

Suriname is the country with most forest cover on earth and harbours a largely intact community of animals and plants. Together with a team (BioREPS) from the Anton de Kom University and Naturalis Biodiversity Center, I investigate terrestrial and aquatic ecosystems to better understand their natural history, ecological requirements, and the potential threats of climate change and chemical, noise, and light pollutants. We also integrate research with teaching, aiming for interdisciplinary projects across education levels, to raise awareness, contribute to local capacity, sustainable use of natural resources, and conservation of biodiversity.

Investigating urban biodiversity from a one health perspective

We share our urban and industrialized environment with many other species. Healthy conditions for humans typically go well together with ecologically beneficial conditions for animals and plants. I investigate conditions and effects of particulate matter, urban heat, and noise and light pollution in cities. Green areas and vegetation boundaries can play a critical role in restricting elevation and propagation of, and exposure to pollutants, for animals and humans alike. Furthermore, smart management of layered and native vegetation can promote urban biodiversity, which can positivily feedback again to human well-being and health. 

Crop pest control in above- and belowground biodiversity

We study how the introduction of flowering plants, so called banker plants, and the addition of compost to the soil, alters the aboveground and belowground biodiversity of arthropods and microbes in the field. We focus on the vegetable leek, and study how we can control thrips, the major pest insect in this crop, without pesticides. We expect that the addition of flowering plants, and compost leads to increases in biodiversity including natural enemies that subsequently keep the pest under control. We collaborate with growers, suppliers, other experts and policy makers, to realize a transition towards a new biodiversity-inclusive cropping system 

Rampant evolutionary transitions in biodiversity of woody growth forms

The evolutionary transition from herbaceousness towards woodiness in flowering plants is a peculiar phenomenon dating back to Darwin's original observations. To understand why plants became woody and why this has happened so frequently over evolutionary history, we have compiled the first globally derived woodiness database with about 7000 species from 700 independent lineages. Most derived woody species thrive in continental regions with recurrent drought cycles. We therefore now hypothesize drought as a major driver of the evolutionary transitions towards woodiness across lineages. We have preliminary experimental support for this hypothesis in several plant groups, and we are now looking into alternative drivers of wood formation across flowering plants.

Anatomical traits underlying drought tolerance in plant biodiversity

It is crucial to better understand how wild plants and crops respond to drought stress in a world facing global change. We still do not know which traits regulate drought tolerance and how this varies among species. Gas embolisms in the root-to-shoot water transport may be a main reason why plants die from drought stress. This so-called hydraulic failure can spontaneously occur, but some (drought-tolerant) species are better adapted to avoid lethal levels of embolisms than other (more sensitive) species. We measure embolism resistance in stems, roots and leaves, along with other ecophysiological traits such as stomatal conductance, to estimate whole-plant drought tolerance. These experimental results are compared across species that vary in wood formation to assess the impact of stem lignification on drought tolerance. 

Traded timber identification to protect tree biodiversity against illegal logging

With an estimated annual turnover of €50–150 billion, illegal logging is the third most profitable transnational crime, after drug trafficking and trade in fraudulent goods. The new European EUDR legislation (2025) for more strict regulation of international timber trade will only be effective in protecting our forests with reliable, large-scale identification and origin-tracing. At present, such methods are not yet available. In collaboration with large wood collection institutes, we develop a reliable, high-throughput wood identification method based on images from wood anatomical sections. This will provide customs officers and other stakeholders with a timber tracking tool to identify illegally logged wood, which will promote sustainable and environmentally responsible practices and contribute to conservation of global tree biodiversity. 

Insect egg development in a warming world: the eco-evo-devo of embryonic developmental time

What is the genetic basis of developmental time? Climate change is putting insect populations under pressure and especially insect species that overwinter as eggs show strong population declines. To survive climate change, insects need to adapt their embryonic developmental time. In this project, we investigate the genetic basis of developmental time, and the adaptive potential of wild insects. Using selection lines in the model insect Tribolium castaneum, we aim to unravel genetic targets of selection and the genetic basis of developmental time. By investigating wild populations of 12 insect species, we assess whether the same genes play a role in different insects  With this knowledge, we can determine if genetic variation is present for these genes in wild insect populations, and aim to predict their adaptability to clime change.

Balanced Lethal Systems

In a balanced lethal system, two chromosome forms carry distinct lethal alleles that are reciprocally compensated for by functional genes on the alternate form. In effect, both are required for survival. Yet, parents randomly pass these forms on to the next generation. Under Mendelian inheritance, exactly 50% of the offspring receive two copies of the same chromosome form and are therefore not viable. The incredibly high mortality in a balanced lethal systems appears to defy evolutionary theory. I lead a genomic study of the best-known case of a balanced lethal system in Triturus to understand balanced lethal system evolution.

Hybrid zone movement

Speciation typically involves a stage in which species can still exchange genetic material across the hybrid zones they establish upon secondary contact. If one species displaces the other, their hybrid zone would move. Such movement may amount to considerable distances over ‘evolutionary time’. Yet, the prevalence of long-term hybrid zone movement is poorly understood. A key prediction is that that the receding species leaves behind a trail of introgressed selectively neutral alleles within the expanding one. I expose the genomic footprint of hybrid zone movement in Triturus hybrid zones.

Genetic pollution

Invasive species can threaten native biota by means of competition, predation and infection. A less-known risk is genetic pollution: the (partial) replacement of local genotypes via hybridization. A particular challenge of quantifying invasive hybridization is that the closely related species involved tend to be morphologically similar. As a consequence, conservation action would depend on large-scale genotyping. Addressing genetic pollution is a notoriously contentious issue, with complications arising at the stage of obtaining and interpreting information. I mainly work on Dutch case studies involving amphibians and reptiles.

Monitoring urban soil biodiversity

Urban soils host complex and often overlooked microbial communities that are essential for the functioning of greenspaces. Together with Naturalis Biodiversity Center and through teaching activities, I investigate how urbanization influences soil biodiversity. By identifying environmental factors and urban features that shape microbial communities across city landscapes, this research contributes to a deeper understanding of how biodiversity is structured belowground in cities.

Understanding tree–microbiome interactions

Trees form dynamic associations with microbial partners that play critical roles in their growth and health. As part of the Silva Nova consortium, I investigate how these tree-microbiome interactions vary across agricultural fields, restoration sites, and natural forests. Understanding how past land use shapes microbial communities helps reveal the legacy effects influencing tree performance, soil biodiversity, and the success of forest restoration.

Enhancing tree stress resilience through soil biodiversity

Urbanization brings stressors such as drought, heat, and nitrogen deposition, that challenge tree survival and performance. I explore how soil biodiversity, particularly mycorrhizal fungi but also other soil microbes, can enhance tree resilience to these pressures. Through field studies and lab experiments, I investigate how microbial diversity supports tree stress tolerance. As part of the Thirsty Cities consortium, this research also informs how soil biodiversity can improve drought resilience of trees and be leveraged in urban planning to create more drought-resilient green spaces.

Living with unloved biodiversity in the city

People do not care or even dislike much of the biodiversity around us. Especially those species that thrive with and near humans and which are commonly called pests, weeds or invasive. We study these unloved species in the city, such as rats in the waste bins, ticks in the urban greenery, or crows and seagulls at bird-feeders. We do this with participatory or citizen science methods to understand the positive or negative appraisal of urban nature and how humans can or cannot live together with sometimes awkward biodiversity.

Not home alone: biodiversity in the house

Our homes are built by humans, for humans, or that is how we imagine our homes. In reality, there is much more non-human life in homes than there are humans, pets or house plants, or other species that we bring in. These uninvited, often unwanted, species also shape our homes through structures and practices. We study biodiversity in the house and what role these housemates play in our everyday life. We strive to understand how humans and non-human animals relate to each other in the most mundane and domestic of ecological settings.