“However, this type of natural selection is more pronounced in extreme winters. When they become milder, mortality rates are lower throughout the species, and there is less selection against the darker reddish brown owls. Towards the end of our study period, and particularly over the last decade, we noted that as winter temperatures rose, selection against the reddish-brown
morph markedly
decreased. In fact, their numbers rose to levels far above those noted in Finnish historic records.” “When it comes to climate change, this
study is perhaps one of the clearest empirical examples of how an organism can adapt to variations in its actual
examining the impact of an avian form of malaria. “We’re interested in the way in which this disease could act as a physiological mechanism that mediates natural selection,” says Karell. By capturing and ringing individual owls, then testing their blood, the team obtained estimates of the number of parasites in their systems, and is using statistical modelling to ascertain their effects. “At a conceptual level, little is known
about how genetically distinct individuals can keep up with the threat of parasites in the wild, so the study is quite novel,” he comments. To create an experimental sample to compare against
AT A GLANCE Project Information
Project Title: Evolutionary dynamics of colour polymorphism
Project Objective: The project investigates how environmental (climate) change generates a phenotypic response in wild populations through evolutionary and ecological processes. The project aims are to understand how environment- driven selection and inherent fitness variation between individuals simultaneously alter the evolutionary response to environmental change.
Project Duration and Timing: 3 years, September 2011 to August 2014
“Empirical evidence from lab studies shows that a melanin pigment creates the different coloured plumage of the owls”
environment,” says Karell. “It suggests that even a long-lived organism like tawny owls has the means to adapt to very rapid changes, through natural selection.” However, the study did not manage to fully ascertain the causes of the selection process that was demonstrated,
particularly as the
survivability rates of both brown and grey owls were found to be comparable. A later study by Karell’s group published in 2013 also concluded that feather- moulting patterns of owls seemed independent
of environmental
conditions, acknowledging that other behavioural and physiological factors were likely at work. To obtain more data about the significance of colour morphs, Karell’s latest three-year project, currently nearing its conclusion, examines the role of parasites as mediators of natural selection. This venture builds on earlier work co-
authored by Karell, and published in the Journal of Evolutionary Biology. The paper argued that, faced with parasitic infection, there was a complex interaction between bodily immune defences and hereditary traits in the owl population. These had different costs for the two colour types. To find out further details of this dynamic relationship, Karell and his colleagues are currently
www.projectsmagazine.eu.com
natural ‘control’ subjects, the scientists also medicated some of the owls using an anti-malaria drug, to document its influence on their breeding patterns and metabolism. “Our next step is to predict what kind of an impact the disease has on survival in the long term and I have, together with colleagues at Lund University in Sweden, developed molecular tools to study the parasites in depth,” says Karell. Although his research to date has
primarily concentrated on Finnish populations, Karell hopes to obtain further funding for research to look at variation in tawny owl colour polymorphism across Europe, with the aim to document large scale genetic patterns and adaptations to different climatic conditions The exercise would require a large-scale
collaboration with other researchers and bird-ringers, to obtain a sizeable and valid data set. “Our intention is to gather complete data from the whole range of the species, and model this statistically in a scientifically robust way” he outlines. “Of course, this has formerly been attempted in lab studies of mice, but this doesn’t reveal anything about ecological contexts. We think it’s very important to learn how evolution operates in our real, and constantly changing world.”
★ 59
Project Funding: Academy of Finland
Project Partners: • Prof. Staffan Bensch, Lund University • Prof. Jan-Åke Nilsson, Lund University • Prof. Jon Brommer, University of Turku • Dr. Jari Valkama, University of Helsinki • Dr. Andreas Lindén, Åbo Akademi University
MAIN CONTACT
Patrik Karell PhD in Ecology and evolutionary biology from University of Helsinki in 2007, postdoctoral work at University of Helsinki 2007-2011 and Lund University 2011. Currently postdoctoral researcher and project leader at Environmental and Marine Biology, Åbo Akademi University. Main research interests range from evolutionary ecology to ecological immunology and population ecology.
Contact: Tel: +358-50-3412879 Email:
patrik.karell@abo.fi Web:
http://web.abo.fi/fak/mnf/biol/ eco/beeg/
patrik.html
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