ETH-News interviewed project manager Martin C. Fischer for an article about the genetic diversity monitoring pilot study, giving a comprehensive overview of the project and its aims as well as interesting insights to preliminary results: link to the article.
The latest issue of HOTSPOT magazine focuses on biodiversity monitoring and presents ongoing and new projects, programs and technologies. Our pilot study is represented with an article about our work and about the challenges of monitoring genetic diversity.
A new IUCN manual guides through the decision-making and evaluation processes involved in designing a genetic diversity monitoring programme and identifying the most appropriate species or populations. The guidance document is aimed at conservation practitioners and includes several case studies, including our pilot study for genetic monitoring in Switzerland. Link to the publication: https://doi.org/10.2305/IUCN.CH.2022.07.en
With the supplementary sampling of Melitaea diamina, the 2022 field season was successfully completed. The collected samples of the five species are distributed – according to their habitats – over the whole of Switzerland and all biogeographical regions. The sampling includes more than 1200 individuals from 158 populations.
The specifically developed sampling strategy (proportional stratified random sampling) has proven successful: the climatic niche, i.e. the range of temperature and precipitation suitable or expected for a species, is well covered for all species.
In addition, areas of varying size, quality, and connectivity were selected using the random sampling strategy.
Thank you all for fantastic presentations and inspiring discussions!
More information about the workshop: https://gendiv.ethz.ch/en/genetic-diversity-monitoring-workshop-2023-in-zurich/
In the new article in the Journal of Applied Ecology, our pilot study for a monitoring of genetic diversity has been compared with and related to other approaches to reporting on within species genetic diversity. The publication shows the international importance of a monitoring of genetic diversity. The publication is available via this link in the Journal of Applied Ecology.
After the largely successful sampling of all five selected species in 2021, the missing false heath fritillary, Melitaea diamina, populations will be sampled this year. In addition, 200 contemporary populations of Hare’s-tail cottongrass, Eriophorum vaginatum, will be sampled for retrospective monitoring of genetic diversity. Where possible, these will be collected from similar places as the 200 historical samples from collections and museums. The over 200 historic samples of Eriophorum and 200 samples of Melitaea are currently being processed in the clean-lab and will soon be sequenced.
As a consequence of the rainy and cool weather in spring and summer 2021, some populations of the false heath fritillary could not be successfully sampled. Therefore, 10-15 populations of the false heath fritillary will be resampled this year, mostly in eastern Switzerland. The collection points were chosen more specifically to increase the chance of successful sampling in the second trial. Since the false heath fritillary is also studied retrospectively, in addition to the recent specimens, specimens from museums the same place of origin, if possible, are also studied. The collection points were slightly optimised for this purpose without compromising our proportionally stratified rantom sampling strategy. This is because it is important that the location of the historical and present-day material coincide as closely as possible, as otherwise geographical rather than temporal differences in genetic diversity are inferred.
For the retrospective analysis of Hare’s-tail cottongrass (Eriophorum vaginatum), about 200 populations are sampled. The aim is to sample a population of each selected herbarium record, which are between 70 and 150 years old, as close as possible to the historical site. The difficulty is to match the approx. 100 year old field descriptions on the labels of the herbarium specimens with today’s field descriptions on the maps and to find potential sites where there is a chance to find and sample the species today. This is especially difficult when the landscape has changed considerably due to human activity. With the populations sampled this year and the approximately 100 years of herbarium specimens, it should be possible to carry out analyses that provide information on whether certain locally adapted plants have come under particular pressure. This is particularly relevant with regard to the massive loss of Hare’s-tail cottongrass habitats (predominantly raised bogs), which has mainly taken place on the Swiss Central Plateau in recent centuries. In addition, it should be possible to determine whether genetic diversity in this species has changed over the time-period studied.
Sampling of the five species was fairly successful despite a wet and cold spring and a gloomy summer.
At the beginning of April 2021, the teams of the Swiss Ornithological Institute started sampling the Yellowhammer (Emberiza citrinella). They sampled about 120 bird over a two-month period. The anticipated number of 150 samples was not reached because bird trapping was hampered by the cold and wet spring. Nevertheless, birds were sampled in 23 of the 30 planned collection quadrats.
Between early April and late July 2021, experts commissioned by the Coordination Center for the protection of Amphibians and Reptiles (karch) were able to collect a total of about 150 samples in the form of embryos or tadpoles of the natterjack toad (Epidalea calamita) in 28 of the 30 planned quadrats. It was often necessary to find replacement quadrats because the natterjack toad, as a pioneer species, often changes its habitat, causing occurrences to disappear and emerge elsewhere. In addition, it is also one of the amphibian species in Switzerland whose populations are in sharp decline.
Just over 220 false heat fritillaries (Melitaea diamina) were collected by various environmental agencies between mid-June and mid-August 2021 in 22 of the 30 planned sampling quadrats. Rainy weather and hailstorms that severely impacted vegetation in some study areas hampered the collectors’ work and limited the number of sunny days on which butterflies were flying and could be sampled.
From early June to early August 2021, environmental agencies successfully sampled 30 populations and 300 individuals of hare’s tail cottongrass (Eriophorum vaginatum). A replacement collection quadrat was needed twice because the species was either no longer present or there were too few individuals at the actual designated location.
Sampling of the Carthusian pink (Dianthus carthusianorum) by environmental agencies was also successful. 31 populations and 330 individuals were sampled between late May and early July 2021. Six replacement collection quadrats were needed, often in regions where Carthusian pink was artificially seeded.
The random stratified proportional sampling strategy proved to be efficient in the field and we covered the climatic space of each species well, as it can be seen in the figure below with the hare’s tail cottongrass as an example. The randomly sampled individuals and populations (red dots) cover the climate space of the species in Switzerland (gray dots) well. The climate space covers the range from low to high mean annual temperature (e.g. low and high elevation regions) on the X-axis, and high to low rainfall regions can be seen on the Y-axis.
The work on retrospective analyses using museum and herbarium samples is currently underway. DNA from museum and herbarium samples that are older than 40 years is highly fragmented, usually with fragments shorter than 70 base pairs. It is also more damaged compared to DNA from freshly collected samples, making it highly susceptible to contamination by new and fresh DNA from humans or other samples processed in the laboratory. These properties necessitate the use of state-of-the-art clean lab, such as those available at the Institute of Evolutionary Medicine (IEM) at the University of Zurich. This clean lab has all the necessary equipment for the various stages of ancient DNA analysis, including a positive pressure system, UV sterilization, and several isolated workstations where research personnel work in full-body protective gear. Only thanks to this careful approach, the recovery and sequencing of DNA from voucher specimens is possible in a reliable manner. Currently, about 200 voucher specimens each of the hare’s tail cottongrass and the false heat fritillaries from Swiss collections are processed in the clean lab.
The preparation of the reference genomes of the five species is well advanced and thanks to new sequencing technologies (PacBio HiFi Reads and OMNI-C Scaffolding) the quality of the reference genomes have exceeded our expectations. Most genomes were assembled almost to chromosome level. This is even true for the natterjack toad, which has the largest genome of the five species and with 3.8 billion base pairs, it is even larger than the human genome.
Great work awaits us this year as well. The DNA of the 1,120 collected samples will be extracted, sequenced and analyzed. In addition, work continues on the museum samples in the clean lab. After the extraction and sequencing of the DNA, these sequences will be analyzed and compared with the modern samples.
The Swiss-wide stakeholder survey, which was conducted as part of the feasibility study for a genetic diversity monitoring, has now been published in the journal Conservation Genetics! The paper is publicly accessible via this link: https://link.springer.com/article/10.1007/s10592-021-01379-6
For the retrospective analysis, more than 700 voucher specimens were found for the Hare’s-tail cottongrass and more than 1,000 for the False heath fritillary in collections in Switzerland – from Geneva to Basel. Where not already done, each specimen was entered into a database and the location was recorded and georeferenced using the original label. In a next step, a selection of the vouchers will now be made. A report on part of our research on collection specimens of the False heath fritillary has just been written and published in the ETH journal GLOBE: https://ethz.ch/en/news-and-events/eth-news/news/2021/06/silent-witnesses.html