Meet Alexander Weigand: speleologist, pollinator specialist and species conservationist at the MNHNL

Dr Alexander Weigand, biologist and curator of zoology at the MNHNL, explains in this interview how classic field research can be combined with modern methods and why even ticks matter.

Dr. Alexander Weigand is a German biologist and researcher at the MNHNL.

His scientific focus is on biodiversity research, particularly in the areas of pollinator insects, entomological vectors, and subterranean fauna.

Among other projects, he is currently working on a comprehensive atlas of hoverflies and on Luxembourg's first national wild bee atlas, as well as studying the country's underground cave biodiversity. Alexander is also involved in science communication and policy advising.

Why is his work so important?

It contributes significantly to the documentation and conservation of Luxembourg's biodiversity.

It combines modern technologies such as DNA metabarcoding and computer tomography with traditional field research.

It provides a scientific basis for nature conservation measures, environmental education, and political decisions.

Find out more in our new interview.

Tell us briefly about your scientific career so far and what you specialise in.

I studied biology in Darmstadt from 2004, specialising in zoology. I subsequently completed my doctorate at Goethe University Frankfurt am Main in the field of biodiversity research and evolutionary biology, focusing on microsnails and the cave habitat.

After my PhD in 2012, I worked at the Graduate Academy of Goethe University (‘Grade’) and developed e-learning materials for PhD students and undergraduates in the field of life sciences. At the same time, I was a trainer and consultant for a company called uni-support. There, I learnt a lot about project management and scientific writing and shared that knowledge with others. From 2014 to 2018, I held a postdoctoral position at Ruhr University Bochum and the University of Duisburg-Essen. During this time, my DFG research proposal was accepted, and I was able to focus on cave biology again.

Since January 2019, I have been working as a curator of zoology at the MNHNL.

What made you choose invertebrates and subterranean biodiversity as your focus?

My focus is on the diversity and distribution of species, primarily invertebrates (insects, spiders, crustaceans, etc.). I am interested in the most diverse groups of organisms about which little is currently known in Luxembourg. My aim is to close the knowledge gaps.

One major project I've been working on since 2019 is focused on wild bees: our work has already enabled us to identify dozens of new species in Luxembourg. We were able to do this because, in addition to the classic methods of biology, we also use modern methods – such as genetics or imaging techniques – as part of an integrative approach.

Another important aspect of my research activities concerns entomological vectors: these are species of invertebrates that can spread so-called zoonoses (see infobox). They include ticks, mosquitoes, sand flies, and midges. We are planning a Luxembourg tick atlas, as there is still very little knowledge about these arachnids. We have already found five new tick species in Luxembourg. We are currently studying them using computer tomography: we place them on microscope slides, analyse their external morphology, examine their internal anatomy and thus gather valuable new insights.

In 2023, we published the mosquito atlas of Luxembourg and, at the same time, recorded the first sand flies (Phlebotomus mascittii) in the country, a finding that is highly relevant from a public health perspective, as sand flies can transmit leishmaniasis to humans and animals (especially dogs) (see infobox). However, Leishmania parasites have not yet been detected in this country.

Through these various activities, I have become the national contact person for entomological vectors for Luxembourg and the European Commission.

How to ticks benefit nature?

They play an important role in ecosystems by regulating populations. Take, for example, the population of roe deer, which no longer have natural predators in our country. If they reproduce undisturbed, they consume the entire undergrowth and cause considerable damage to the forest. Once the deer population reaches a certain size and density, diseases spread, transmitted by  ectoparasites such as the tick, so that the deer population is reduced. Ticks, in this context, act as natural regulators of certain host populations.

Incidentally, not many tick species bite humans. Ticks are highly specialised – some, for example, feed exclusively on bats or birds. So not all ticks are the same.

How do atlases help to protect biodiversity?

Hotspots are defined for certain species, either due to a particularly high diversity or the presence of rare species that are nationally or even Europe-wide threatened. Once identified, appropriate conservation measures can be implemented to protect them.

For example, a species of hoverfly from the genus Neoascia specialises in Petasites hybridus (butterbur) and is classified as endangered on the European Red List. We have found a large population of Neoascia unifasciata in Luxembourg, as well as a few smaller satellite populations. One measure to protect them is selective tree removal to make room for the butterbur.

Such measures are implemented by the biological stations, the ANF (Administration de la Nature et des Forêts), or the municipalities.

But that's not all: you also work in the field of speleology. Can you tell us more about that?

We have been commissioned by the Ministry of the Environment to record the ecological condition of Luxembourg's caves (a process known as cave monitoring). Cave-specific animals, typical cave habitats (such as standing or flowing water, stalactites, frost-protected areas) and human influence (e.g. geocaches, rubbish dumps, fireplaces) are systematically assessed. All of these play a role in biodiversity.

We try to sample every cave. An important volunteer organisation, the Groupe Spéléologique Luxembourgeois (G.S.L.), works closely with us: they have already produced many cave maps and even developed a cave cadastre.

A very diverse profession!

Indeed. To summarise, I often go out into the field to observe different species in their natural habitats – that's the best way to study them. There are countless new species under our feet, and one doesn’t necessarily have to travel to the tropics to find organisms of scientific interest. We are currently in the process of describing six new groundwater amphipods (Niphargus) from Luxembourg!

Why is biodiversity in groundwater so important for the entire ecosystem?

The quality of groundwater is essential for maintaining clean springs and rivers. Groundwater is pumped for drinking water and treated at great expense; in contrast, animals help filter groundwater biologically. Although this can also be done mechanically or chemically, organisms are often more efficient at breaking down smaller substances. For example, the movement of certain crayfish species supports bacteria and fungi in breaking down and filtering biological material more effectively.

Other animal species depend on clean springs for survival. Some dragonfly species of the genus Cordulegaster, for instance, must live as larvae in spring water for up to six years before emerging as winged adults.

What is DNA metabarcoding and how does it help you in your daily work?

DNA barcoding has been used for over 20 years to identify animals, plants, and fungi. It enables species identification based on genetic material – the genome. It works like a supermarket barcode scan: a small piece of genetic material is compared with a reference database and checked for matches, allowing the species to be genetically identified.

The modern version of this method is called DNA metabarcoding. This means that many individuals are analysed simultaneously for a specific section of genetic material and identified using the reference database. For example, we took a leg from a large number of wild bee individuals and compared the DNA from these legs with the reference database. This provided a species list for each location where we collected wild bees.

One of these reference databases, called “BOLD” (Barcode of Life Data Systems, https://boldsystems.org/), contains no less than 16.5 million barcodes. Creating and maintaining such a database requires collaboration among taxonomic experts worldwide.

How does your research influence political decisions and nature conservation measures?

In speleology, we are the experts consulted for each site when management measures need to be implemented. For example, we are currently discussing a management plan for the “Mamerleeën” with the responsible authorities.

I am also a member of the Pollinator Action Committee, which determines the pollinator-friendly measures introduced in Luxembourg and identifies those still needed.

To advance this work, I am active in the Observatoire National de l'Environnement Naturel, an association of institutions involved in nature conservation and environmental management in Luxembourg. We are consulted on political environmental decisions and draft legislation, and we issue formal statements.

What are the most important steps to stop the decline of pollinators?

For pollinators in general, maintaining the greatest possible habitat diversity – avoiding large monocultures – is crucial. Structurally rich habitats are essential: hedges, open sandy areas, jagged forest edges, ponds, and more.

At the same time, the availability of flowers must be kept high, as wild bees and other pollinators such as butterflies and hoverflies are often specialised. Many visit only a few – or even just one – species of flowering plant to collect pollen as adults or to feed as larvae or caterpillars.

Many of these rare flowering plant species thrive in nutrient-poor soils. If soils are too rich in nutrients, generalist plants tend to outcompete them. A species-rich landscape is best achieved by maintaining nutrient-poor soils. In practical terms, this means reducing fertiliser use.

Which of your projects have been the most fun so far and why?

The whole field of speleology. It's such a wide-ranging subject!

In 2021, I had the opportunity to train two female astronauts in cave biology. The goal was to prepare these potential candidates from the foundation “Die erste deutsche Astronautin”, which was collaborating with ESA, for an extraordinary experience: spending a week in a cave in Germany.

What new research questions would you like to tackle in the future?

We are currently launching a project on another group of entomological vectors about which little is known: gnats. Gnats from the genus Culicoides transmit bluetongue disease. Recently (2024 - 25), many cattle and sheep in central-western Europe contracted the disease and had to be culled. However, knowledge about vector insects remains insufficient in individual European countries. Gaining a better understanding of these vectors is essential for effective prevention.

Do you have any tips for young scientists who want to get started in your field?

Just give it a try! If you are motivated, committed, and flexible about where you work, you will find an interesting position. Don’t be discouraged.

Do you have a final message that you would like to pass on?

Society needs increased funding for taxonomy (the study of species). There is a lack of secure, permanent positions in Luxembourg. It is essential to understand which species are dangerous, which need protection, and where their populations occur.

Author: Diane Bertel

Editors: Monique Kirsch, Selma Weber