Authors: Multigner L. F., DiLeo M., Bras A. &Saastamoinen M.
Affiliations:
Research Centre for Ecological Change, Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
Ontario Ministry of Northern Development, Mines, Natural Resources and Forestry, Peterborough, ON, Canada
Habitat loss and fragmentation are considered the key drivers of biodiversity loss. While evidence indicates that habitat loss has a negative impact on biodiversity, there is no consensus on whether the effect of fragmentation per se –more discontinuous habitat distribution but no difference in habitat amount- is negative or positive. We studied how fragmentation per se affects genetic diversity (GD) while controlling for habitat amount in the Glanville fritillary butterfly metapopulation in the Åland islands. We used 40 SNP neutral markers from two years to calculate GD indices in over 200 habitat patches with relatively high population abundance. We estimated our appropriate landscape size to be a 3.5 km radius around each focal patch. We then selected patches with surrounding landscapes with a similar habitat amount but various number of patches, and assessed their respective effect on focal patch GD. Our first results support the habitat amount hypothesis, as the number of fragments had a neutral effect on the GD. However, further assessment of lack of contrast or statistical power in our dataset is required as we also failed to find a significant effect of the habitat amount.
The ability of populations to maintain an effective immunity against diseases and parasites relies on the presence of genetic diversity. Genetic diversity protects against widespread infection in the population if the disease shows genetic specificity for infection. Therefore, genetically diverse host populations face a lower risk of infections. Genetic diversity can be reduced when there is a population decline which subsequently may affect the population immunity. Collembolas are soil microarthropods and are constantly exposed to potentially infectious fungi and bacteria, hence it is important for collembola populations to maintain effective immunity to survive. With agricultural practices intensifying, this causes high mortality in many collembola populations in the agricultural fields. Due to the high importance of collembola to soil processes, it is critical that we understand how a reduction in their genetic diversity can affect their immunity and subsequent survival. In my poster, I will be presenting my PhD research plans on measuring natural varying genetic diversity through population genetics, measuring immunity gene variation to assess whether there is selection to maintain effective immunity in small populations, and culturing collembola from the respective populations for immune assays to associate genetic diversity and immunity performance.
Authors
Bras A1,2, Kaila L3, Jensen M R4, Djernæs M4, Bechsgaard J4, Bilde T4, Francis Thomsen P. F.4, Saastamoinen M1,2
Affiliations
1Research Centre for Ecological Change, Organismal and Evolutionary Biology Research Program, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
2Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
3Zoology Unit, Finnish Museum of Natural History, University of Helsinki, Helsinki, Finland
4Department of Biology - Genetics, Ecology & Evolution, Aarhus University, Denmark
Abstract
Insects have been reported declining worldwide in terms of numbers of species but also in population densities. Several factors such as climate change, pollution or land-use changes have been pointed out as main drivers of these declines. Whereas species losses are quantifiable through long term biodiversity monitoring, genetic losses remain difficult to quantify over time. The long-term monitoring surveys of butterflies in Finland have shown that they respond differently to climate change with species presenting various population trends. This baseline offers the opportunity to assess how factors responsible for insect decline has shaped genetic diversity over time. Using a museomics approach, we aim to (i) investigate the changes in genetic diversity during the last century for butterfly species showing population decline, and (ii) to assess how genetic diversity has changed for species belonging to the same genus but presenting contrasting population trends. To study this, we will sequence whole genomes of museum specimens collected at historical time points and compare the data with contemporary samples from same areas of each species of interest to look for genetic patterns.
Used for posterpresentation at:
Jeppe Bayer Pedersen, Trine Bilde, Jesper Smærup Bechsgaard
Major declines in arthropod populations have been reported in recent years, attributed to factors such as agricultural and forestry intensification, habitat degradation, and climate change. This is expected to be accompanied by reductions in effective population size and increased isolation of populations, both factors that affect the genetic composition of a population. Smaller populations are associated with elevated effects of drift and less efficient selection, which is predicted to cause an increase in genetic load, which is inversely related to fitness.
This project aims to quantify genetic load in natural populations of arthropods as a function of population size, age, and isolation. These demographic parameters are expected to be proxies for the effective population size and thereby the balance between drift and selection.
We will sequence multiple populations of 20 soil-surface-living arthropod species (collembolans, beetles, and spiders), which vary in dispersal ability. Populations are collected from 55 pastures across Denmark, that vary in area, temporal continuity (age), and spatial continuity (isolation). Fifty individuals from each species and pasture are subsequently pool-sequenced to obtain whole-genome re-sequencing data, which will be used to estimate components of genetic load, such as realized genetic load, including both segregating and fixed variants.
Different methods for estimation of genetic load will be utilized, such as comparison of functional sequences under evolutionary constraint, the distribution of fitness effects, and ratios of non-synonymous to synonymous site diversity across the whole and parts of the genome.
Land use intensification is one of the major factors driving current biodiversity change and loss. Previous studies have shown that traditional agricultural practices can help preserve insect diversity in comparison to intensively managed areas.
In this study we conducted a field monitoring of butterflies in the agricultural environments of the Åland islands, where intensively managed agricultural areas are still less prevalent than in the mainland Finland. Using the CORINE landcover database, we quantify the landscape structures surrounding the butterfly transect sites at different spatial scales.
We expect the butterfly diversity to decline with increase in cultivated land and landscape homogeneity. We also look at how the butterfly community composition has changed over the 20 years between the first and last sampling time. Even though the number of butterflies has stayed stable over the years, there have been changes in the species composition of the community.
The results will work as the starting point for further studies addressing how different functional traits of butterflies could be linked to differences in the landscape structure in their surrounding habitats.
