Building the future by doing more together

MIDGE - MIcroevolutionary Dynamics and Genetic Erosion in pollution-affected Chironomus populations
Coordinator - João Luís Teixeira Pestana
Programme - PTDC/BIA-BEC/104125/2008
Execution dates - 2010-05-01 - 2013-04-30 (36 Months)
Funding Entity - FCT
Funding for CESAM - 170000 €
Total Funding - 170000 €
Proponent Institution - Universidade de Aveiro
Participating Institutions
Senckenberg Research Institute and Natural History Museum (SNG)

Chronic pollution has been shown to decrease genetic variation in populations of several species alongside with adverse effects on the physiology of organisms. Following basic concepts of evolutionary theory, this loss of genetic diversity may reduce the potential of populations to adapt to changing environments. In strongly human impacted ecosystems, environmental pollution is frequently associated with habitat destruction/fragmentation which can also lead to population isolation, inbreeding and reduced genetic diversity. It is thus of crucial importance to investigate the impact of reduced genetic diversity on the response to chemical stress.

Ecotoxicological studies need to consider not only short term effects of pollution, such as changes in life history traits of organisms, but also its long term effects, such as genetic erosion. This is especially important because organisms exposed to chemical stressors must mobilize defensive and repair processes if they are to survive. These processes are energy-demanding and may have negative fitness consequences. Because genetic erosion caused by pollution will likely lead to the loss of evolutionary potential, it is also of crucial importance to assess the evolutionary consequences of changes in genetic variability. This includes the assessment of fitness costs of genetic adaptation under optimal and, probably even more important, because natural populations are faced to the combined effects of multiple anthropogenic and natural stressors, under environmental changing conditions. Moreover, it is essential also to unravel the physiological basis of different susceptibilities and responses towards contamination of natural populations from contaminated and reference sites. The recent development of molecular genetic methods that allow a cost effective and robust assessment of population genetic variation strongly contributed to the emergence of evolutionary toxicology focused on the impact of environmental pollution on the genetic variability of natural populations. However, to our knowledge, integrative investigations that allow a mechanistic link between contamination, genetic variability, organismal physiology and fitness costs associated with genetic adaptation are scarce. There is an urge for studies on this research field because the combined investigation using genetic, physiologic and life-history approaches will allow a better and comprehensive understanding of stressor effects on populations. Such integrated approaches will certainly lead to a more reliable prediction of the anthropogenic impacts on biodiversity.

This project aims to tackle this gap by studying the impacts of contamination on  microevolutionary processes in natural populations of the limnic model species Chironomus riparius. More specifically we intend to address two main questions:
- Does chronic pollution affect genetic variability of C. riparius populations in the field?
- Are C. riparius populations in contaminated areas adapted to pollution exposure?
- What are the evolutionary consequences of this altered genetic variability due to pollution in terms of fitness costs?

To address these subjects, the genetic variability of C. riparius populations from unpolluted and contaminated sites will be addressed using mitochondrial sequence variation and nuclear microsatellite analyses. Investigations of genetic adaptation processes in C. riparius will be done with life-cycle laboratory assays performed with different strains from both contaminated and reference sites. These strains will be exposed to contaminants and natural stressors, and multiple parameters will be measured across different levels of biological organisation. The laboratory tests will assess susceptibilities of the different populations to contaminants and to environmental change. In addition, multigenerational tests using strains from uncontaminated sites exposed to contaminants will be conducted to experimentally evaluate adaptation processes and loss of genetic variation in midge populations across several generations. Effects on genetic variability are non-specific concerning mechanisms of action and at the same time sensitive towards permanent effects of contaminants in populations. Not surprisingly, measures of genetic erosion have recently been proposed as the ultimate biomarker of effect and their use in ecotoxicological studies can therefore significantly improve understanding of the ecological effects of chronic chemical exposure. By focusing on effects of contaminants on genetic variability in natural  populations the MIDGE project will aid in developing new bio-monitoring approaches, and provide advanced scientific basis for integrative ecological risk assessment methodologies which are essential for effective environmental conservation strategies.

Members on this project
Diana Marina Gomes de Campos
Grant holder (technician)
Isabel M. Lopes

PhD student
João Luís Teixeira Pestana
Principal Investigator

Grant holder (technician)

CESAM Funding: