Which European green toads should be crossed to boost populations? Population genomic approaches reveal strong differentiation between fragmented Swedish populations of Bufotes viridis, and low genetic diversity within most subpopulations, informing conservation actions
(2024) BION02 20232Degree Projects in Biology
- Abstract
- Amphibians are the most rapidly declining vertebrate class globally and are especially vulnerable to habitat fragmentation causing population isolation. The genetic consequences of population size reduction, inbreeding and genetic drift, can have detrimental effects on the long-term viability of amphibian species, often leading to extinction. Population genomics approaches have become a crucial tool to monitor genetic diversity within and between subpopulations and inform conservation actions such as captive breeding and reintroductions. The European green toad, Bufotes viridis, is the most threatened amphibian in Sweden. Understanding the underlying population structure and differentiation between subpopulations as well as the level of... (More)
- Amphibians are the most rapidly declining vertebrate class globally and are especially vulnerable to habitat fragmentation causing population isolation. The genetic consequences of population size reduction, inbreeding and genetic drift, can have detrimental effects on the long-term viability of amphibian species, often leading to extinction. Population genomics approaches have become a crucial tool to monitor genetic diversity within and between subpopulations and inform conservation actions such as captive breeding and reintroductions. The European green toad, Bufotes viridis, is the most threatened amphibian in Sweden. Understanding the underlying population structure and differentiation between subpopulations as well as the level of inbreeding is necessary to make informed management decisions and to achieve the goal of establishing a genetically diverse, stable metapopulation system. We found strong population structure and genetic differentiation between most Swedish subpopulations indicating limited gene flow. The populations are small and isolated, thus highly susceptible to genetic drift. Our whole-genome analysis results show signs of inbreeding within subpopulations that are more recent compared to a more genetically diverse population from Poland. We recommend a re-evaluation of the choice of source population for the existing captive breeding program, taking into consideration the risk of eroding local adaptation, and avoiding both inbreeding depression, as well as outbreeding depression. (Less)
- Popular Abstract
- Genomics and Old Toes for Toad Conservation
Biodiversity is important due to the interconnectedness of species, ecosystems, and biomes. The foundation for all levels of biodiversity is genetic diversity, a metric of how much DNA variation exists between individuals. Without genetic diversity, populations will struggle to evolve and adapt to forces such as climate change, disease, and habitat fragmentation. Thus, it is crucial to consider genetic diversity measures in designing conservation actions. The most endangered vertebrate class, amphibians, are becoming increasingly threatened due to changing environmental conditions and reduced genetic diversity as populations decline. Here, we studied the genomes of endangered toad populations... (More) - Genomics and Old Toes for Toad Conservation
Biodiversity is important due to the interconnectedness of species, ecosystems, and biomes. The foundation for all levels of biodiversity is genetic diversity, a metric of how much DNA variation exists between individuals. Without genetic diversity, populations will struggle to evolve and adapt to forces such as climate change, disease, and habitat fragmentation. Thus, it is crucial to consider genetic diversity measures in designing conservation actions. The most endangered vertebrate class, amphibians, are becoming increasingly threatened due to changing environmental conditions and reduced genetic diversity as populations decline. Here, we studied the genomes of endangered toad populations and found low genetic diversity and signs of inbreeding.
European green toads (Bufotes viridis) have seen significant declines in Sweden. Only a few, isolated populations remain at the northern edge of their global distribution. Small, fragmented populations are especially vulnerable to loss of genetic variation due to increased levels of genetic drift and inbreeding (mating with close relatives). These changes to the genetic composition of populations can have long-term effects on species’ survival. Thus, taking a closer look across the genome of extant European green toads, as well as DNA from old museum specimen, can help guide management strategies.
In this study, I used bioinformatic tools to estimate and compare genetic diversity for each of seven Swedish green toad populations as well as one Polish population. I also tried to find genomic signs of inbreeding. In addition to analyzing contemporary DNA samples, I attempted to extract DNA from toe clippings of historic museum specimen to understand how genetic variation has changed through time.
Strong differentiation and low levels of variation among European green toads in Sweden
The populations of European green toads were genetically different from each other, suggesting limited interconnectedness between them. I found overall low genetic diversity among Swedish green toads and compared to the Polish population, which suggests that Swedish populations may have relatively lower adaptive potential. Genomic evidence of inbreeding indicated a possible risk of negative effects on survival and reproduction. The greatest degree of recent inbreeding was detected in the contemporary source population for a captive breeding program. Unfortunately, our museum samples had not retained sufficient DNA for analysis.
Most conservation attempts involve risks, trade-offs, and ethical dilemmas. However, looking at genomic data enables more informed decisions and long-term predictions about the resilience of species. This project is directly applied through collaboration with institutions that implement the action plan for European green toads in Sweden and incorporate genetic information in their decision making process. Further research is needed to access historic DNA of museum samples.
Master’s Degree Project in Biology, Animal Ecology 45 credits 2024
Department of Biology, Lund University
Advisors:
Jacob Höglund, Department of Ecology and Genetics, Uppsala University
Bengt Hansson, Department of Biology, Molecular Ecology and Evolution, Lund University (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9176773
- author
- Walderich, Leonie Muriel
- supervisor
- organization
- course
- BION02 20232
- year
- 2024
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9176773
- date added to LUP
- 2024-10-18 11:12:45
- date last changed
- 2024-10-18 11:12:45
@misc{9176773,
abstract = {{Amphibians are the most rapidly declining vertebrate class globally and are especially vulnerable to habitat fragmentation causing population isolation. The genetic consequences of population size reduction, inbreeding and genetic drift, can have detrimental effects on the long-term viability of amphibian species, often leading to extinction. Population genomics approaches have become a crucial tool to monitor genetic diversity within and between subpopulations and inform conservation actions such as captive breeding and reintroductions. The European green toad, Bufotes viridis, is the most threatened amphibian in Sweden. Understanding the underlying population structure and differentiation between subpopulations as well as the level of inbreeding is necessary to make informed management decisions and to achieve the goal of establishing a genetically diverse, stable metapopulation system. We found strong population structure and genetic differentiation between most Swedish subpopulations indicating limited gene flow. The populations are small and isolated, thus highly susceptible to genetic drift. Our whole-genome analysis results show signs of inbreeding within subpopulations that are more recent compared to a more genetically diverse population from Poland. We recommend a re-evaluation of the choice of source population for the existing captive breeding program, taking into consideration the risk of eroding local adaptation, and avoiding both inbreeding depression, as well as outbreeding depression.}},
author = {{Walderich, Leonie Muriel}},
language = {{eng}},
note = {{Student Paper}},
title = {{Which European green toads should be crossed to boost populations? Population genomic approaches reveal strong differentiation between fragmented Swedish populations of Bufotes viridis, and low genetic diversity within most subpopulations, informing conservation actions}},
year = {{2024}},
}