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Latitudinal MHC variation and haplotype associated differential survival in response to experimental infection of two strains of Bd-GPL in common toads
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics. Uppsala University.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics.
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(English)Manuscript (preprint) (Other academic)
National Category
Evolutionary Biology
Identifiers
URN: urn:nbn:se:uu:diva-382090DOI: 10.1101/597559OAI: oai:DiVA.org:uu-382090DiVA, id: diva2:1305941
Available from: 2019-04-20 Created: 2019-04-20 Last updated: 2019-11-12
In thesis
1. Immunogenetic variation along the latitudinal gradient in Scandinavian anuran species: Evolutionary processes, demography and infection
Open this publication in new window or tab >>Immunogenetic variation along the latitudinal gradient in Scandinavian anuran species: Evolutionary processes, demography and infection
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The evolutionary and demographic processes affecting how genetic variation is partitioned and distributed over large geographical scales is of fundamental importance for our understanding of how organisms may adapt to their environments. Northern peripheral populations generally have lower genetic variation and individuals in these populations may therefore face difficulties adapting to their local environment. At northern latitudes lack of genetic variation could be detrimental in face of newly emerging diseases as a result of anthropogenic actions and warmer climate in these areas. In this thesis, I explore genetic variation and the contemporary evolutionary processes affecting genes involved in the adaptive immune defense (Major Histocompatibility Complex; MHC) and the innate immune defense (AMP; Antimicrobial Peptides) over a large geographical gradient in anuran species (paper I, II and IV). I study signatures of historical selection on the MHC class II exon 2 and AMP (Temporin, Brevinin and Palustrin) sequences in the Signal Peptide and the Acidic Propiece domains (paper II and III). Finally, I investigate potential associations between specific MHC class II exon 2 alleles and a chytrid fungus infection (Bd) in common toads (Bufo bufo) (paper IV). The results reveal that genetic variation of MHC class II exon 2 decreases towards northern latitudes in R. arvalis and B. bufo and have been shaped by complex evolutionary processes (drift, selection, migration) affected by different demographic scenarios. On the other hand, AMP nucleotide variation is divergent among geographical areas, but there is no clear geographical pattern along the same gradient, suggesting diversifying selection as the main force shaping genetic variation. Finally, I found an effect of two specific MHC class II exon 2 alleles on survival in juvenile B. bufo when infected with Bd. In summary, my thesis unravels the complex patterns shaping genetic diversity at large scales. My results may guide conservation practices aiming to prevent amphibian mass mortality events on-going all over the world.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. p. 45
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1811
National Category
Evolutionary Biology
Research subject
Biology; Biology with specialization in Evolutionary Genetics
Identifiers
urn:nbn:se:uu:diva-382092 (URN)978-91-513-0662-9 (ISBN)
Public defence
2019-06-14, Zootisalen, Norbyvägen 14-18, Uppsala, 13:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council Formas, 146400178Swedish Research Council, 621-2013-4503
Available from: 2019-05-22 Created: 2019-04-20 Last updated: 2019-06-17
2. The response in native wildlife to an invading pathogen: Swedish amphibians and Batrachochytrium dendrobatidis
Open this publication in new window or tab >>The response in native wildlife to an invading pathogen: Swedish amphibians and Batrachochytrium dendrobatidis
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Emerging infectious diseases are causing mortality and declines in wildlife populations globally. My thesis aims to get as clear a picture as possible of the effect the invasive chytrid fungus Batrachochytrium dendrobatidis has on the Swedish amphibian community.

In Paper I I performed a large-scale survey testing for the presence of Bd in three regions in Sweden (Southern, Central and Northern). I sampled 1917 amphibians from 101 localities and found that Bd was widespread in southern and central Sweden, occurring in all nine investigated species and in 45.5 % of the sampled sites with an overall prevalence of 13.8%. I found a positive correlation between the temperature at spawning for each species and species prevalence. Species that require higher temperatures for egg-laying are distributed in the southern parts of the country, which led to a higher prevalence in the southern region.

In Paper II, I investigated which local environmental factors in breeding habitats, landscape structure and amphibian community affect the occurrence and prevalence of Bd among breeding sites in southern Sweden. Bd prevalence in the four species with the highest prevalence (Bombina bombina, Bufotes variabilis, Epidalea calamita and Rana arvalis) was higher in ponds surrounded by less mature forest, few wetlands, and higher pH.

In Papers III and IV, I looked at species and population differences in responses to Bd infection. I performed an infection experiment described in Paper III, where I exposed individuals from two common Swedish species (moor frog R. arvalis and common toad Bufo bufo) originating from two regions (north and south) with two different strains of Bd (from Sweden and the UK). I found that infection led to lower survival and growth in both species, more so in B. bufo than in R. arvalis. Small size proved to be a strong determinant of survival. As individuals from the northern population were significantly smaller than the southern ones, this may have led to the northern populations being more affected by Bd infection. In Paper IV, I studied variation in MHC Class IIB loci in B. bufo along a latitudinal gradient across Sweden. Variation in MCH genes decreased from south to north. Also, differences in survival from the experiment in Paper III could be explained by MHC haplotypes. I found that survival in the southern region was dependent on both Bd-strain and MHC haplotype.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. p. 44
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1879
Keywords
Emerging diseases, chytrid, amphibians, wildlife
National Category
Ecology
Research subject
Biology with specialization in Animal Conservation
Identifiers
urn:nbn:se:uu:diva-396987 (URN)978-91-513-0812-8 (ISBN)
Public defence
2019-12-13, Ekmansalen, EBC, Norbyvägen 14, Uppsala, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council Formas
Available from: 2019-11-15 Created: 2019-11-12 Last updated: 2019-11-18

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