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Fitness costs associated with low genetic variation are reduced in a harsher environment in amphibian island populations
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Population and Conservation Biology.ORCID iD: 0000-0002-5553-2691
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Population and Conservation Biology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Population and Conservation Biology.
2010 (English)In: Conservation Genetics, ISSN 1566-0621, E-ISSN 1572-9737, Vol. 11, no 2, 489-496 p.Article in journal (Other (popular science, discussion, etc.)) Published
Abstract [en]

A basic premise of conservation geneticists is that low levels of genetic variation are associated with fitness costs in terms of reduced survival and fecundity. These fitness costs may frequently vary with environmental factors and should increase under more stressful conditions. However, there is no consensus on how fitness costs associated with low genetic variation change under natural conditions in relation to the stressfulness of the environment. On the Swedish west coast, natterjack toad Bufo calamita populations show a strong population genetic structure and large variation in the amount of within-population genetic variation. We experimentally examined the survival of natterjack larvae from six populations with different genetic variation in three thermal environments corresponding to (a) the mean temperature of natural ponds (stable, laboratory), (b) a high temperature environment occurring in desiccating ponds (stable, laboratory) and (c) an outdoor treatment mimicking the natural, variable thermal conditions (fluctuating, semi-natural). We found that larvae in the outdoor treatment had poorer survival than larvae in the stable environments suggesting that the outdoor treatment was more stressful. Overall, populations with higher genetic variation had higher larval survival. However, a significant interaction between treatments and genetic variation indicated that fitness costs associated with low genetic variation were less severe in the outdoor treatment. Thus, we found no support for the hypothesis that fitness costs associated with low genetic variation increase under more stressful conditions. Our results suggest that natural thermal stress may mask fitness losses associated with low genetic variation in these populations.

Place, publisher, year, edition, pages
2010. Vol. 11, no 2, 489-496 p.
Keyword [en]
Conservation genetics, genetic structure, peripheral populations, genetic diversity, amphibians, environmental stress
National Category
Ecology
Research subject
Population Biology
Identifiers
URN: urn:nbn:se:uu:diva-107342DOI: 10.1007/s10592-009-0039-2ISI: 000275455700013OAI: oai:DiVA.org:uu-107342DiVA: diva2:228827
Available from: 2009-08-06 Created: 2009-08-06 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Genetic variation and local adaptation in peripheral populations of toads
Open this publication in new window or tab >>Genetic variation and local adaptation in peripheral populations of toads
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Northern fringe populations generally have low amounts of genetic variation and inhabit habitats where specific adaptations are needed. On the Swedish west coast, the natterjack toad (Bufo calamita) inhabits skerry islands. I have examined: I) adaptation to two environmental stressors in this habitat; II) the genetic population structure within the skerry habitat; III) the effects of neutral genetic variation, selection and genetic drift on trait divergence within the skerry habitat; and IV) the effects of genetic variation on fitness under three thermal conditions of varying stressfulness. V) I have also studied the impact of putative local adaptations on the Scandinavian green toad (Bufo viridis) conservation programme. The results suggest that the skerry natterjack toads are locally adapted to the desiccation risk in their habitat. However, despite inhabiting a more saline habitat, they had a lower salinity tolerance when compared to their conspecifics in the more general habitat. The lowered salinity tolerance is most likely explained by the presence of negative genetic correlations between salinity tolerance and desiccation avoidance and suggests that the occurrence of multiple environmental stressors may constrain adaptation. Within the skerry habitat, the toads exhibited a strong population structure with populations differing in their levels of genetic variation. Moreover, within the skerry habitat, the results suggest uniform selection pressures. However, correlations between trait values and neutral genetic variation suggest that inbreeding depression may affect trait values and thus potentially constrain adaptation. In the natterjack toad, fitness costs associated with lack of genetic variation were only present under benign conditions and not under more natural conditions. This suggests that environmental stress masks inbreeding depression in these traits under natural conditions. In the study regarding the Scandinavian green toads, I found that one population inhabiting a saline habitat had a higher salinity tolerance than other populations in less saline habitats. This suggests the presence of local adaptation, which should be acknowledged in the green toad conservation programme. Several of the northern fringe populations of toads fulfill the criteria of being Evolutionary Significant Units and their conservation thus should be prioritized.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 65 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 662
National Category
Ecology
Research subject
Population Biology
Identifiers
urn:nbn:se:uu:diva-107395 (URN)978-91-554-7580-2 (ISBN)
Public defence
2009-09-25, Friessalen, Norbyvägen 18A, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2009-09-04 Created: 2009-08-10 Last updated: 2015-04-29Bibliographically approved

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Rogell, BjörnThörngren, HannaLaurila, AnssiHöglund, Jacob

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