Fatima Jlil, Trine Bilde, Jesper Bechsgaard, Anne Aagaard, Jilong Ma, Jeppe Pedersen
Abstract:
Arthropod populations are declining worldwide, with habitat loss from human land-use changes and rapid environmental shifts exacerbating the threat. If populations fail to adapt to these changes or suffer critical size declines due to ecological constraints or direct human impact, events of local extinction may occur. Survival under such pressures may depend largely on the capacity for local adaptation; however, arthropods’ capacity to adapt, and their underlying determinants remain poorly understood. In Denmark, intensive agricultural practices have fragmented natural landscapes, providing an ideal setting to explore these dynamics. We performed pool‐sequenced from up to 55 populations of 30 arthropod species—including of 10 collembola, 10 beetles, and 10 spiders species— collected in grassland sites. The sampling sites were also characterized for environmental variables such as temperature, humidity, and soil properties. This species assemblage, which spans a range of life history traits and Ne (such as dispersal abilities and effective population sizes), experiences comparable levels of habitat fragmentation and environmental change. By linking local adaptation signals with population genomic metrics—such as effective population size trajectories, gene flow, and genetic diversity—our study integrates ecological and genomic perspectives to elucidate factors driving population resilience. Moreover, by quantifying the degree of local adaptation, we assess its role in buffering against extinction risk. Although preliminary, our approach promises to enhance our understanding of the adaptive mechanisms that enable arthropods to persist in rapidly changing, human-altered landscapes.
Authors: Fernández Multigner, L., Bras, A., Saastamoinen, M
Abstract:
Many species are shifting their range to track the most suitable environmental conditions in response to global warming. This strategy can improve the chances of species' long-term persistence. However, colonisation events, lower population densities, and strong selection pressures at the expanding range margin can result in reduced genetic diversity at the local populations. Lower habitat availability and connectivity in the range edge can also restrict the expansion, gene flow and population size, with further effects at the genetic level. Although the loss of genetic diversity during range shift could be only temporary, a rapid and continuous increase in temperatures could cause range shifts to be too swift to allow for genetic diversity recovery. Selection pressures that might help marginal populations expand can also lose effectiveness if the genetic variability is too low for selection to act on. Such scenario will leave expanding edge populations in a particularly vulnerable position. Alternatively, if enough gene flow is maintained between the range edge and other populations, which can be enhanced by the landscape and habitat connectivity, the genetic diversity may be recovered. There is abundant theory on the interplay of colonisation effects, selection and gene flow on the genetics of edge populations, and simulation studies showing a reduction in genetic diversity due to range expansion. However, few studies have looked at these patterns and the underlying processes in natural populations across different species. To test these hypotheses, three range-shifting and two non-range-shifting butterfly species in Finland were chosen as model organisms. For each species, ten individuals from three populations in the expanding edge of the distribution range and three in the core of the distribution were sampled for full genome analyses. Each individual was sequenced with a low-coverage whole-genome resequencing approach and will be used to estimate population genetic diversity. We will also look for signs of selection affecting the populations of the range margin. We expect to observe lower genetic diversity in expanding populations than in core populations, and to find stronger differences in species that have expanded northwards over the last decades. Preliminary data from the genetic analyses will be presented here. In future, we aim to link the genetic diversity estimates to the habitat availability and connectivity within the real landscapes.
Authors: Ulla Riihimäki, Juho Kökkö, Jenna Palttala, Jesper Bechsgaard & Marjo Saastamoinen
Abstract:
Land use is one of the key drivers in the current biodiversity loss with agricultural intensification and climate change impacting natural habitats worldwide. Landscape structure has the potential to filter individuals for example through structural changes or changes in microclimate which could lead to spatial sorting of individuals by their traits. One key trait impacting individuals’ ability to survive in changing landscapes is dispersal which is also a key trait for the gene flow between populations. Studies assessing among species variation in dispersal suggest that species with better dispersal abilities are more likely to persist under intensified land use. Less is known about land use impacts on within species dispersal ability and subsequent consequences on population genetic structure. In this study we collected individuals of three grassland butterfly species with differing dispersal capabilities (Maniola jurtina, Pieris napi, Thymelicus lineola) from six populations across two different types of landscapes; habitats surrounded by agricultural fields and more natural or semi-natural meadow habitats. We measured variation in dispersal (morphological and physiological proxies) and body size. Individual whole-genome sequencing was used to assess population structure between the landscape types and populations in all species.
Intra-specific variation in flight metabolic rate (FMR) was evident in all species. However, only in M. jurtina, which is considered as an intermediate disperser in comparison to high disperser P. napi and low disperser T. lineola, butterflies originating from agricultural landscapes had higher FMR compared with butterflies originating from more natural landscapes. M. jurtina butterflies from agricultural landscapes had also higher body mass than those from more natural landscapes. Assessing the genetic structure between populations will provide information whether the differences in FMR in M. jurtina have also led to genetic structure between landscape types. The genetic analysis can also confirm our assumptions on the dispersal capabilities of the different species; with no genetic structure between populations indicating high gene flow and dispersal between populations vs. population structure indicating lower gene flow and dispersal. The sequencing is completed, and the analysis of the genetic structure are underway. Our results suggest that land use, can impact within species trait variation with agricultural landscapes selecting for individuals with better dispersal ability. The genetic analysis will help to shed light whether landscape structure can lead to population structure between landscape types or whether it is simply explained by geographical distance and dispersal ability. Further studies would be required to understand the impacts of landscape structure on ecological processes, both between and within species.
Authors: Fernández Multigner, L. F., Bras A., Saastamoinen M.
Abstract:
In response to climate change, numerous species are shifting their range towards higher latitudes, tracking suitable temperature conditions. Although these range shifts are often considered a positive response, the genetic composition of the expanding populations can be altered, and the genetic diversity reduced. The genetic loss can be bigger if the area of expansion presents little available habitat or is poorly connected, as that would make the new populations smaller and more isolated. Although the negative effects of habitat loss and fragmentation on species richness are known, their role during range expansions is still understudied, especially at the genetic level. In this study, we aim to understand the effect of habitat configuration on the distribution of genetic diversity in five butterfly species in Finland, two of which are expanding northwards. We are first studying the role of the landscape on the species distribution through habitat suitability models based on occurrence, climatic, habitat and host plant distribution data. We will present the preliminary models of the five species. In a next step, we are aiming at integrating species genetic diversity data with the distribution models to perform individual-based simulations, which will allow us to understand the role of landscape on the spatial distribution of genetic diversity. We expect genetic diversity to be reduced in the northern border of the distribution, as well as in areas with little habitat or poor connectivity. This study will help understand the interplay of climate change and habitat loss as drivers of genetic diversity loss.
Authors: Fatima Jlil, Anne Aagaard, Jesper Bechsgaard, Trine Bilde, Jilong Ma
Abstract:
Arthropods were among the first taxa to recolonize northern Europe after the Pleistocene glaciations, yet many populations are now declining in association with Anthropogenic land use. How species have responded to historical environmental changes are reflected in the distribution of adaptive genomic signals among populations – the adaptation landscape. Past and recent selection thus inform their adaptive potential in a changing world. Here we characterize the adaptation landscape of six Collembola species, small terrestrial hexapods with limited mobility, sampled across 54 locations in Denmark. We identify a south-to-north post-glacial recolonization history that strongly structures the spatial distribution of adaptive signals. A substantial proportion of selection sweeps shared among populations are attributed to shared ancestry rather than independent convergent evolution. Older, widely shared sweeps are significantly longer than younger, population-specific sweeps. These patterns are consistent with different selective regimes acting during early colonization compared to the more recent post-colonization phase. In line with this, ancestral and more recent sweeps show distinct Gene Ontology enrichments, suggesting shifts in the biological processes under selection through time. Across species, effective population size (Ne) predicts the number of selection sweeps per population. Moreover, we observe fewer sweeps per unit of evolutionary time in recent times across species, which suggest a slowdown of adaptive evolution. This temporal shift of the adaptation landscape raises the possibility that the Anthropogenic land usage constrains the adaptive evolution in low-dispersive soil arthropods.
Authors: Ulla Riihimäki, Mathijs de Koning, Lotta Kaila & Marjo Saastamoinen
Abstract:
Agricultural intensification is one of the key drivers of biodiversity loss. Intensified agriculture is often associated with increased use of pesticides and the use of pesticides could negatively impact also non-target species living in the vicinity of agricultural lands. We exposed larvae of the Glanville fritillary butterfly (Melitaea cinxia) to a short-term exposure of a herbicide, a fungicide, or a mix of the two via their larval host plant (Plantago lanceolata). Survival and performance of the larvae was recorded and potential carry-over effects on adult butterfly f itness traits were assessed under semi-natural conditions in an outdoor enclosure. Our results showed significantly higher mortality of 60 % in the larvae exposed to the fungicide and 22 % mortality in the fungicide- herbicide mix treatment, with both treatments also impacting adult morphology. Adult female butterflies exposed to the mix of fungicide and herbicide treatment during their development also had lower lifetime reproductive success than the other treatment groups, suggesting that the combined chemical load had stronger carry-over effects into adulthood. Our results demonstrate clear negative impacts of a commonly used fungicide on a non-target butterfly species. The combined effect of two pesticides, while less lethal to larvae directly, seem to have a more profound carry-over impact on fitness of adult female butterflies. The mechanisms underlying the effects of a fungicide alone and in interaction with the herbicide, as well as the relatively minor impacts of herbicide alone on the specialist insect warrant further investigation in the role of pesticides in natural populations.
Authors: Multigner L. F., Bras A., Saastamoinen M.
Abstract:
Species responses to climate change include adapting in place or tracking suitable conditions in space or time. Range shifts can, however, greatly impact species at the genetic level, causing lower genetic diversity in the expanding than in the core populations due to colonization events, lower densities, and selection pressures. These processes are also shaped by the landscape characteristics along the range, due to habitat availability impacting population connectivity and gene flow, further influencing genetic diversity. While selection may allow species to adapt, rapid genetic diversity loss may limit long-term adaptive potential for species coping with climate change through range shifts. Alternatively, successfully expanding species could be avoiding genetic diversity loss by maintaining enough gene flow between populations, for which habitat connectivity is determinant, and positive population trends given that they are dispersive enough. In Finland, numerous butterfly species have expanded northwards in response to climate change, prompting a study on how landscape, climate, and range shifts affect their genetic diversity. For my PhD, I aim to first analyse genetic diversity patterns and selection pressure across northern distribution ranges of expanding and non-expanding butterfly populations. Next, I will develop spatial models to define how landscape and climate influence species distribution and genetic patterns. Finally, I will simulate potential genetic diversity changes under various climatic scenarios, considering habitat restoration and individual translocation. The findings will be used to suggest conservation measures that consider the interplay between genetic diversity, range shifts, and landscape factors
Author: Multigner L. F.
Abstract:
Species responses to climate change include adapting in place or tracking suitable conditions in space or time. Range shifts can, however, greatly impact species at the genetic level, causing lower genetic diversity in the expanding than in the core populations due to colonization events, lower densities, and selection pressures. These processes are also shaped by the landscape characteristics along the range, due to habitat availability and spatial distribution impacting population connectivity and gene flow, further influencing genetic diversity. While selection may allow species to adapt, rapid genetic diversity loss, may limit long-term adaptive potential for species coping with climate change through range shifts. Alternatively, successfully expanding species could be avoiding genetic diversity loss by maintaining enough gene flow between populations, for which habitat connectivity is determinant, and positive population trends given that they are dispersive enough.
In Finland, numerous butterfly species have expanded northwards in response to climate change, prompting a study on how landscape, climate, and range shifts affect their genetic diversity. For my PhD, I aim to first analyse genetic diversity patterns and selection pressure across northern distribution ranges of expanding and non-expanding butterfly populations, by sampling and sequencing populations from the northern border and the core of the distribution area in Finland. Next, I will develop spatial models to define how landscape and climate influence species distribution and genetic patterns at a finer scale. Finally, I will simulate potential genetic diversity changes under various climatic scenarios, considering habitat restoration and individual translocation. The findings will be used to suggest conservation measures that consider the interplay between genetic diversity, range shifts, and landscape factors.
Authors: Dis, N. E., Ruokolainen, A., Nair, A., Oostra, V. & Saastamoinen, M.
Abstract:
Insect populations will need to rapidly adapt to survive the large-scale environmental changes caused by anthropogenic pressures. However, we still know very little about the factors that determine a population’s adaptive potential. Here, we utilize temporal genomic data from a unique long-term sample collection of the Finnish Glanville fritillary butterfly metapopulation (Melitaea cinxia) to investigate which factors influence the adaptive potential of wild insect populations. We whole-genome sequenced individuals sampled in the last 15 years, with 4-8 timepoints for 3-6 populations, to identify changes in population genomic variation over time. Previous work has shown that climate change and land-use changes are affecting the habitat quality of this species, resulting in population declines over time. Using genome-environment association analysis (GSEA), we will determine how ecological processes influence population genomic composition over time, linking temporal genomic changes to ecological data on population numbers and habitat quality. This highly novel approach will provide unprecedented insights into the eco-evolutionary dynamics of wild populations, specifically testing whether the speed of genetic changes is affected by ecological processes.
Authors: Multigner L. F., DiLeo M., Bras A. & Saastamoinen M.
Abstract:
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.
Authors: Tammy A.T. Ho, Jørgen A. Axelsen, Jesper S. Bechsgaard, Tove H. Jørgensen, Trine Bilde
Abstract:
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 A, Kaila L, Jensen M R4 Djernæs M, Bechsgaard J, Bilde T, Francis Thomsen P. F., Saastamoinen M
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.
Authors: Jeppe Bayer Pedersen, Trine Bilde, Jesper Smærup Bechsgaard
Authors:
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.
Abstract:
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.
Authors: Nathalie P. E. A. Ibsen
Abstract:
I investigate the population genetic composition of non-threatened butterflies (Lepidoptera) with varying dispersal abilities, in response to their species-specific habitat configurations. Over the past two years, I have delved into population genetic theory, genomics, dispersal parameters, and habitat assessments. Currently, my focus is on exploring the parameter space of several genomic analyses. The choice of parameters in both well-supported and emerging methods significantly influences the outcomes and, consequently, the inferences drawn. However, not all insights are robust to changes in the parameter space. These key points are illustrated on this poster, presented at the Population Genetics Group 58 conference in Sheffield, 2025. The discussion was lively, with several researchers taking the time to participate in the survey, share their experiences, and offer valuable advice. The survey results revealed no clear consensus on best practices for defining parameter space in comparative genomics, highlighting the need for further exploration and methodological refinement.
