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Helena Westerdahl
University of Lund,
Sweden
Title
Avian MHC: genetic variation, natural
selection and disease resistance in a natural population of great reed
warblers
Abstract
The Major Histocompatibility
Complex (MHC) plays a central role in vertebrates’ specific immune defence
against various pathogens. Compared with other coding genes the MHC genes
exhibit extremely high levels of polymorphism, which most likely is
maintained by balancing selection. The importance in immune defence and the
polymorphism make these genes essential to study from an ecological and
evolutionary perspective, specifically in populations that are subject to
natural selection. I am studying MHC genes in a population of wild songbirds,
great reed warblers Acrocephalus arundinaceus. Here I have characterized parts of the
MHC class I and II genes and I have focused especially on transcribed genes
since these are likely to be under selection. In order to be able to study
MHC class I diversity in the great reed warblers I developed a PCR-based
screening method. I found a large number of MHC loci and also a surprisingly
high level of allelic variation in the great reed warblers, in contrast to
the limited variation that was detected using neutral markers. The MHC allele
frequencies varied significantly between different cohorts (individuals
hatched in the same year) in the study population. This implies that there is
frequency dependent selection on the MHC class I alleles. Avian malaria could
be one such selective force generating the temporal variation in MHC allele
frequencies. I found an association between numbers of MHC class I alleles (a
measure of level of heterozygosity) and prevalence
of a specific avian malaria parasite. There was also an association between a
specific MHC allele, previously shown to be under frequency dependent
selection, and prevalence of this specific malaria parasite. These
associations suggest that individuals carrying either a large number of MHC
alleles or a specific MHC allele are protected against lethal malaria
infections. So far, associations between certain MHC alleles, or a large
number of MHC alleles, and resistance to specific diseases have only been
found in a few species. Most of these associations involve humans or are
experiments that have been done under controlled conditions. To me it is compelling
that the selection pressure from pathogens on MHC genes can be visualised
also in a wild bird population.
Biography
Helena Westerdahl began her undergraduate studies at Lund University
in 1990 and completed a MSc in Animal Ecology in
1995. She started her PhD studies in October 1995 at the Department of Animal
Ecology, supervised by Prof Torbjörn von Schantz, Prof Staffan Bensch and Associate Prof Håkan
Wittzell. She defended her thesis “Avian MHC:
variation and selection in the wild” on 2003.10.10, Opponent Prof. Josephine
Pemberton.
International
Conferences and Meetings
Fifth International Workshop on MHC Evolution, Visby 1997 (poster)
22nd International
Ornithological Congress, Durban
1998, (talk)
Sixth International Workshop on MHC Evolution 1999, (poster)
European Society for Evolutionary Biology IX, Leeds 2003, (talk)
Refereeing
Helena Westerdahl has
refereed manuscripts for Behavioural Ecology, Journal of Avian Biology, Ecography and Condor and also has evaluated an
application for Natural Environment Research Council NERC, UK.
International Collaborations
Dr David Richardson University of East Anglia, “Comparisons of MHC
genes in Seychelles
warblers and Great reed warblers”
Dr Katharina Foerster,
Max Planck Research Centre for Ornithology, Seewiesen
“MHC genes in blue tits”
PhD Camille Bonneaud, Université
Pierre et Marie Curie, Paris “Screening of MHC genes in house sparrows”
Teaching
During my PhD studies Helena Westerdahl
has done 300h of teaching (seminars, lectures, computer exercises and
molecular genetic laboratory practical classes). She has supervised a masters
degree project (10p) “Maintenance of MHC class I polymorphism in the great
reed warbler” by Maj Kroon
Employments
1998.11.01-2004.01.15 PhD-position at the
Department of Animal Ecology, Lund
University
2004.01.16-2004.10.31 Project Assistant at
the Department of Animal Ecology, Lund
University
Maternity leave 100% 1999.07.01-2000.06.30
and 2002.03.30-2003.01.05
Selected
recent publications
- Westerdahl, H., Bensch,
S., Hansson, B., Hasselquist,
D. and von Schantz, T.
(1997) Sex ratio variation among broods of great reed warblers Acrocephalus arundinaceus.
Molecular Ecology, 6: 543-548.
- Bensch, S., Westerdahl,
H., Hansson, B. and Hasselquist,
D. (1999) Do females adjust the sex-ratio of their offspring in relation
to skew in breeding sex ratios? Journal of Evolutionary
Biology 12:1104-1109.
- Westerdahl, H.,Wittzell, H. and von Schantz, T. (1999)
RFLP-polymorphism and transcription of Mhc
class I sequences in a Passerine bird, the great reed warbler. Immunogenetics 49:158-170.
- Wittzell, H., Madsen, T., Westerdahl, H., Shine, R. and von Schantz, T. (1999) MHC variation in birds and
reptiles. Genetica 104:301-309.
- Bensch, S., Stjernman,
M., Hasselquist, D., Östman,
Ö., Hansson, B., Westerdahl, H. and Torres Pinheiro, R. (2000) Host specificity in avian blood
parasites: a study of Plasmodium and Haemoproteus
mitochondrial DNA amplified from birds. Proceedings of the Royal Society
London B
267:1583-1589.
- Westerdahl, H., Bensch, S., Hansson,
B. and Hasselquist, D. (2000) Brood sex
ratios, female harem status and resources for nestling provisioning in
the great reed warbler Acrocephalus arundinaceus. Behavioural Ecology and Sociobiology 47:312-318.
- Westerdahl, H., Wittzell, H. and von Schantz, T. (2000) Mhc diversity in two passerine birds: no
evidence of a “minimal essential Mhc”. Immunogenetics 52:92-100.
- Richardson, D and Westerdahl, H. (2003) A comparison of MHC diversity in two Acrocephalus species: the outbred great reed warbler and the inbred Seyshelles warbler. Molecular Ecology 12:3523-3529.
- Bonneaud C., Sorci,
G., Morin, V., Westerdahl, H., Zoorob, R. and Wittzell,
H. (2004) Diversity of MHC class I and IIB genes in house sparrows (Passer
domesticus. Immunogenetics 55:855-865.
- Westerdahl, H, Hansson,
B, Bensch, S. and
Hasselquist D. (2004) Between-year variation
of MHC allele frequencies in great reed warblers; selection or drift?
Journal of Evolutionary Biology 17:485-492.
- Arlt, D., Bensch,
S., Hansson, B., Hasselquist,
D. and Westerdahl H. (2004) Observation of a ZZW-female in a natural population: implications
for avian sex determination. Biology Letters 271:S279-S251.
- Hansson, B., Westerdahl,
H., Hasselquist, D., Åkesson
M., Bensch, S. (2004) Does linkage
disequilibrium generate heterozygosity-fitness
correlations in great reed warblers? Evolution 58:870-879.
- Westerdahl, H., Wittzell,
H., von Schantz, T. Bensch,
S. (2004) MHC class I typing in a songbird with numerous loci and high
polymorphism using motif-specific PCR and DGGE. Heredity 92:534-542.
- Westerdahl, H. (2004) No evidence of an MHC based mate choice in the great reed
warbler. Molecular Ecology 13:2465-2470.
- Westerdahl H., Waldenström
J., Hansson B., Hasselquist
D. and Bensch S. (submitted) Associations between malaria and MHC genes in a migratory
songbird
Department of Animal Ecology
Ecology Building
SE -223 62 Lund
Sweden
http://www.biol.lu.se/zooekologi/forskargrupper_en.htm
http://fisher.teorekol.lu.se/ekol_inst/mol_ekol/index.html
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