Personal profile


I am a professor in animal ecology with a broad interest in evolutionary and behavioural ecology. Much of my research centers around aspects related to “eco-immunology” – a relatively new and interdisciplinary research field that examines interactions among host physiology and disease ecology in a range of environmentally relevant contexts. My research encompasses theoretical, methodological and empirical studies related to various eco-immunological issues such as the identification and quantification of immune costs (both in terms of physiology and Darwinian fitness), direct and long-term (hidden) costs of infection (telomeres and senescence), sexual selection and honest signaling, sexually antagonistic selection (e.g. on immune gene (MHC) diversity and immunity effects of maternal programming (antibody and hormone transfer to offspring).

A backbone of my research is the ongoing long-term project on the great reed warblers at Lake Kvismaren, Sweden. Over the last 35 years, I have coordinated a multitude of ecological studies on this unique study system (e.g. studies on the social and genetic mating systems, bird song, inbreeding, malaria parasites and geolocator studies). The data generated in this project includes a large multi-generational pedigree, based on >3000 DNA-sampled individuals, of which we for >800 have detailed information on lifetime reproductive success, lifespan, behaviour and morphological traits. These data provide the base for very good estimates of Darwinian fitness, as well as for QTL mapping, selection and microevolution studies of behavioural (e.g. spring arrival) and morphological traits. Other research themes are molecular and genomic ecology, e.g. immune gene evolution, telomere ecology and sex chromosome evolution in birds.

ERC Advanced grant - EcoImmuneCosts

In 2017, I was awarded a prestigious ERC Advanced Grant from the European Research Council for the project ’Hidden costs of disease, immune function and their consequences for Darwinian fitness’ (EcoImmuneCosts). In this project, we aim to better understand the physiological costs associated with ‘mild’ (seemingly harmless) diseases that are the direct or indirect result of immune system activation and maintenance. We conduct several long-term disease and immune challenge experiments and take advantage of our long-term population study on great read warblers at lake Kvismaren in central Sweden. Some of our target research questions are: is there a causative link between costs of chronic malaria infection and accelerated senescence of the body? Is telomere length a key mediator of, or merely correlated with, disease-associated fitness costs? Is there a general pattern so that other miId infections and immune response per se induce ’hidden’ costs? Read more about the project here

Recent research highlights

Extreme altitudes during diurnal flights in a nocturnal songbird migrant Sissel Sjöberg, Gintaras Malmiga, Andreas Nord, Arne Andersson, Johan Bäckman, Maja Tarka, Mikkel Willemoes, Kasper Thorup, Bengt Hansson, Thomas Alerstam & Dennis Hasselquist 2021. Extreme altitudes during diurnal flights in a nocturnal songbird migrant. Science 372: 646-648.

In this paper in Science (7 May 2021), we show that a nocturnally migrating songbird (the great reed warbler) migrate at unexpectedly high altitudes at day. When prolonging their flights into daytime during the crossing of the Sahara Desert and/or the Mediterranian Sea, the birds ascended from relatively high flight altitudes (mean 2400m) at night to extremely high cruising altitudes at day (mean 5400m, max 6300m). This novel diel pattern can not be explained by night and day differences in wind directions or high air temperature, but could potentially be a behavioural reaction to avoid overheating caused by solar radiation when flying at daytime.

Download reprint or read full text and abstract here:    

Full text:




Asghar M, Hasselquist1,† D, Hansson B, Zehtindjiev P, Westerdahl H  & Bensch†, S. 2015. Hidden costs of infection: chronic malaria accelerates telomere degradation and senescence. Science 347:436-8 (1Corresponding author. †These two authors contributed equally to this study.)

This paper in Science (23 Jan 2015) has been recommended at Faculty1000Prime, and has rendered huge interest (>180 citations on WoS). Read the fulltext or download a reprint (pdf; 420 Kb). We show that a seemingly harmless infection (chronic avian malaria) with no visible direct effects on behaviours (singing and nestling feeding), annual reproduction or survival to next year, over the long-term shortens lifespan (with 33%) and reduces lifetime offspring numbers (with >50%) in wild songbirds. These ‘hidden’ long-term costs inducing senescence could be mediated by accelerated telomere degradation, as malaria-infected birds showed faster telomere shortening, both in wild and experimentally infected great reed warblers. (Telomeres protect the chromosome ends and their shortening may be a link to ageing and senescence).

Asghar, M., Palinauskas, V., Zaghdoudi-Allan, N., Valkiunas, G., Muhkin, A., Platonova, E., Färnert, A., Bensch, S. & Hasselquist, D. 2016. Parallel telomere shortening in multiple body tissues owing to malaria infection. Proceedings of the Royal Society B 283:20161184.

The impact of infections on telomere attrition in different body tissues within an individual is unknown. In this study, we experimentally infected siskins (Spinus spinus) with the avian malaria parasite Plasmodium ashfordi, and used real time quantitative PCR to measure telomere length. Over 105 days post infection, malarial infection resulted in parallel telomere shortening in blood and tissue from of all six major organs investigated (liver, lungs, spleen, heart, kidney and brain), suggesting that the infection had induced systemic stress. Our results have far-reaching implications for understanding how short-term effects of an infection can translate into long-term costs, such as organ dysfunction, degenerative diseases and aging.


If you have an interest in evolutionary ecology, eco-immunology/physiology and immune genetics, and in particular in the interface between them, then do not hesitate to contact me to discuss possibilities to join my group. You can browse through our project pages to see if your interests and ideas align with our research themes. PhD opportunities are usually advertised through the Lund University job vacancies portal. If you are a recently graduated PhD thinking about getting your own funding to do a post-doc, we might just have the project for you!

Expertise related to UN Sustainable Development Goals

In 2015, UN member states agreed to 17 global Sustainable Development Goals (SDGs) to end poverty, protect the planet and ensure prosperity for all. This person’s work contributes towards the following SDG(s):

  • SDG 2 - Zero Hunger
  • SDG 3 - Good Health and Well-being
  • SDG 13 - Climate Action


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Collaborations the last five years

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