Papers by Susanne Lachmuth
Global migration issues, 2016
Mountain regions are among the most vulnerable areas with regard to global environmental changes.... more Mountain regions are among the most vulnerable areas with regard to global environmental changes. In the Bolivian Andes, for example, environmental risks, such as those related to climate change, are numerous and often closely intertwined with social risks. Rural households are therefore characterized by high mobility, which is a traditional strategy of risk management. Nowadays, most rural households are involved in multi-residency or circular migratory movements at a regional, national, and international scale. Taking the case of two rural areas close to the city of La Paz, we analyzed migration patterns and drivers behind migrant household decisions in the Bolivian Andes. Data were collected through semi-structured interviews with selected respondents from 68 households. The drivers for migration were categorized, their relative importance was calculated, and generalized linear mixed models were applied for statistical analyses. Our results underline that migration is a traditional peasant household strategy to increase income and manage livelihood risks under rising economic pressures, scarcity of land, insufficient local off-farm work opportunities, and low agricultural productivity. Migration predominantly occurs to nearby urban areas located in the same region. Climatic variability and water scarcity, which have increased through climate change, play crucial roles as additional stressors for agricultural production. Our results suggest that environmental factors do not drive migration independently, but are rather combined with socio-economic factors. There is a need for more research on the links between environmental changes driven by climate change and other factors and their effects on migration dynamics and rural development in the Bolivian Andes and adjacent areas.
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Frontiers in Ecology and Evolution
IntroductionEcological genomic models are increasingly used to guide climate-conscious restoratio... more IntroductionEcological genomic models are increasingly used to guide climate-conscious restoration and conservation practices in the light of accelerating environmental change. Genomic offsets that quantify the disruption of existing genotype–environment associations under environmental change are a promising model-based tool to inform such measures. With recent advances, potential applications of genomic offset predictions include but are not restricted to: (1) assessing in situ climate risks, (2) mapping future habitat suitability while accounting for local adaptations, or (3) selecting donor populations and recipient areas that maximize genomic diversity and minimize maladaptation to future environments in assisted migration planning. As for any model-based approach, it is crucial to understand how arbitrary decisions made during the modeling process affect predictions and induce uncertainty.MethodsHere, we present a sensitivity analysis of how various modeling components influen...
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New Phytologist
Local adaptation to climate is common in plant species and has been studied in a range of context... more Local adaptation to climate is common in plant species and has been studied in a range of contexts, from improving crop yields to predicting population maladaptation to future conditions. The genomic era has brought new tools to study this process, which was historically explored through common garden experiments. In this study, we combine genomic methods and common gardens to investigate local adaptation in red spruce and identify environmental gradients and loci involved in climate adaptation. We first use climate transfer functions to estimate the impact of climate change on seedling performance in three common gardens. We then explore the use of multivariate gene-environment association methods to identify genes underlying climate adaptation, with particular attention to the implications of conducting genome scans with and without correction for neutral population structure. This integrative approach uncovered phenotypic evidence of local adaptation to climate and identified a set of putatively adaptive genes, some of which are involved in three main adaptive pathways found in other temperate and boreal coniferous species: drought tolerance, cold hardiness, and phenology. These putatively adaptive genes segregated into two 'modules' associated with different environmental gradients. This study nicely exemplifies the multivariate dimension of adaptation to climate in trees.
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Philosophical Transactions of the Royal Society B: Biological Sciences, 2022
Shifting range limits are predicted for many species as the climate warms. However, the rapid pac... more Shifting range limits are predicted for many species as the climate warms. However, the rapid pace of climate change will challenge the natural dispersal capacity of long-lived, sessile organisms such as forest trees. Adaptive responses of populations will, therefore, depend on levels of genetic variation and plasticity for climate-responsive traits, which likely vary across the range due to expansion history and current patterns of selection. Here, we study levels of genetic and plastic variation for phenology and growth traits in populations of red spruce ( Picea rubens ), from the range core to the highly fragmented trailing edge. We measured more than 5000 offspring sampled from three genetically distinct regions (core, margin and edge) grown in three common gardens replicated along a latitudinal gradient. Genetic variation in phenology and growth showed low to moderate heritability and differentiation among regions, suggesting some potential to respond to selection. Phenology t...
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Aim. Understanding the forces that drive range shifts in forest landscapes is imperative for pred... more Aim. Understanding the forces that drive range shifts in forest landscapes is imperative for predicting species distributions under anthropogenic climate and land use change. However, empirical studies exploring how these components jointly influence critical early-life stages of mountain tree species across environmental gradients are scarce. We used the high-mountain tree Polylepis australis as model species to investigate the relative importance of altitude and associated climatic conditions, land use for livestock and microsite characteristics on early-life performance. Location. Córdoba Sierras, central Argentina. Methods. We set up an extensive in situ sowing experiment with a robust split-plot design that integrated spatial scales ranging from 0.4 m2 subplots at the microsite level (associated with vegetative and micro-topographic structures), to livestock exclosure and enclosure plots of several hectares, to an altitudinal gradient of 1000 m. Components of early-life performance were monitored across two subsequent growing seasons. Results. Microsite characteristics played a fundamental role in P. australis establishment, whereby interactions with altitude and/or land use suggested alternate mechanisms: facilitation (likely reduced desiccation) dominated at low altitude while at high altitude abiotic stress (likely intensive frost and radiation) overruled any microsite effects. At mid altitude benefits of competition release prevailed over facilitation and microsite effects gained importance under livestock presence. Inconsistencies between pre- and post- emergence responses illustrated potential tradeoffs between beneficial and detrimental effects of microsite conditions upon performance throughout early life: a favorable location for seeds may abruptly turn adverse for seedlings. Main conclusions. We unravel how changes in altitude, anthropogenic disturbances and microsite characteristics jointly modulate P. australis performance across stages of early establishment. Such information is fundamental when categorizing specific microhabitats as “safe sites” for tree regeneration especially in mountain environments with high spatiotemporal heterogeneity
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Inbred and outbred lineages from which fitness components were obtained. Arabic numerals refer to... more Inbred and outbred lineages from which fitness components were obtained. Arabic numerals refer to population numbers. Numbers of populations correspond to those in Table S1
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As a consequence of founder effects, inbreeding can hamper colonization success: First, in specie... more As a consequence of founder effects, inbreeding can hamper colonization success: First, in species with self-incompatibility controlled by an S-locus, inbreeding may decrease cross-compatibility, mainly due to the sharing of identical S-alleles between closely related mating partners. Secondly, inbreeding can reduce fitness of inbred relative to outbred offspring (i.e. inbreeding depression). Polyploids often show reduced inbreeding depression compared to diploids, which may contribute to the overrepresentation of polyploids among invasive species. This is the first study that tests how the effects of inbreeding differ between geocytotypes (i.e. ploidy levels within a given range). Our model organism, Centaurea stoebe, is strictly self-incompatible and comprises three geocytotypes: diploids are more frequent than tetraploids in the native range, while only tetraploids occur in the invasive range. We conducted a breeding experiment (sib-mating vs. outcrossing) with 14 native diploid, 13 native tetraploid and 15 invasive tetraploid populations. We recorded cross-compatibility and estimated a cumulative index for offspring fitness. Since frequent inbreeding can result in purging of genetic load responsible for inbreeding depression, our analyses included a metric for within-population relatedness, based on eight microsatellite markers, to assess the effect of purging. Inbreeding was found to reduce cross-compatibility, which was similarly pronounced in diploids and tetraploids. It also caused inbreeding depression in cumulative fitness, which was significant in diploids but not in tetraploids. No evidence of purging was observed as inbred fitness was not affected by within-population relatedness. Synthesis. Our results provide new insights into the contrasting invasion success of the cytotypes of C. stoebe. As the effects of cross-compatibility and purging were comparable between cytotypes, both processes can be ruled out to affect the colonization success of diploids versus tetraploids. Our findings are consistent with the hypothesis that polyploidy increases the masking of recessive mutations, which maintains high fitness in inbred tetraploids and may thus facilitate colonization of new ranges. We highlight that reduced inbreeding depression may add to previously acknowledged advantages of polyploids in range expansions, a mechanism that may hitherto have been underestimated due to a lack of data on variation in inbreeding depression across geocytotypes
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Plant Biology, 2018
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New Phytologist, 2022
Local adaptation to climate is common in plant species and has been studied in a range of context... more Local adaptation to climate is common in plant species and has been studied in a range of contexts, from improving crop yields to predicting population maladaptation to future conditions. The genomic era has brought new tools to study this process, which was historically explored through common garden experiments. In this study, we combine genomic methods and common gardens to investigate local adaptation in red spruce and identify environmental gradients and loci involved in climate adaptation. We first use climate transfer functions to estimate the impact of climate change on seedling performance in three common gardens. We then explore the use of multivariate gene-environment association methods to identify genes underlying climate adaptation, with particular attention to the implications of conducting genome scans with and without correction for neutral population structure. This integrative approach uncovered phenotypic evidence of local adaptation to climate and identified a set of putatively adaptive genes, some of which are involved in three main adaptive pathways found in other temperate and boreal coniferous species: drought tolerance, cold hardiness, and phenology. These putatively adaptive genes segregated into two 'modules' associated with different environmental gradients. This study nicely exemplifies the multivariate dimension of adaptation to climate in trees.
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Oikos
<strong>ABSTRACT </strong>from the connected paper [Haider, S., Palm, S., Bruelheide,... more <strong>ABSTRACT </strong>from the connected paper [Haider, S., Palm, S., Bruelheide, H., de Villemereuil, Menzel, A. &amp; Lachmuth, S. (2022): Disturbance and indirect effects of climate warming support a plant invader in mountains. Oikos, https://doi.org/10.1111/oik.08783]: Climate warming and increased disturbance (resulting from intensified land use) are expected to enhance the invasibility of plant communities and the performance of exotic species also at high elevations, and thus pose additional threats to mountain ecosystems. The invasion success of introduced genotypes will also depend on their degree of pre-adaption to high elevation climatic conditions, which may vary intra-specifically across source populations. For populations currently spreading in the lowlands, climate warming might reduce the climatic distance to high-elevation sites and thus remove a barrier to upwards spread. Here, we investigated the various facets of mountain invasions in a single, integrative experimental study. We applied a community transplant approach between high- and low-elevation sites in the European Alps to address effects of climate warming and disturbance through land use on community invasibility and the performance of the exotic species <em>Senecio inaequidens</em>, a potential future plant invader in the Alps. Additionally, the transplant sites served as common gardens to test the influence of climatic pre-adaptation to current (high site) and future (low site) climatic conditions on the performance of <em>S. inaequidens</em> in the transplanted communities. The 16 invasive Central and Western European <em>S. inaequidens</em> source population locations covered a wide geographic range, and thus a wide amplitude of climatic distances and presumed pre-adaptation to our gardens. Our results attest to a strong effect of disturbance, which increased community invasibility, and promoted the performance of the exotic species. Contrary to our expectation, experimentally induced climate warming did not increase community [...]
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1. Density-dependence is of fundamental importance for population and range dynamics. Density-dep... more 1. Density-dependence is of fundamental importance for population and range dynamics. Density-dependent reproduction of plants arises from competitive and facilitative plant-plant interactions that can be pollination-independent or pollination-mediated. In small and sparse populations, conspecific density-dependence often turns from negative to positive and causes Allee effects. Reproduction may also increase with heterospecific density (community-level Allee effect), but the underlying mechanisms are poorly understood and the consequences for community dynamics can be complex. Allee effects have crucial consequences for the conservation of declining species, but also the dynamics of range edge populations. In invasive species, Allee effects may slow or stop range expansion. 2. Observational studies in natural plant communities cannot distinguish whether reproduction is limited by pollination-mediated interactions among plants or by other neighbourhood effects (e.g. competition for abiotic resources). Even experimental pollen supply cannot distinguish whether variation in reproduction is caused by direct density effects or by plant traits correlated with density. Finally, it is unknown over which spatial scales pollination-mediated interactions occur. 3. To circumvent these problems, we introduce a comprehensive experimental and analytical framework which simultaneously (1) manipulates pollen availability and quality by hand pollination and pollinator exclusion, (2) manipulates neighbourhoods by transplanting target plants, and (3) analyses the effects of con- and heterospecific neighbourhoods on reproduction with spatially-explicit trait-based neighbourhood models. 4. Applying this framework to Senecio inaequidens, one of Europe’s fastest plant invaders, we found that the seed set was strongly pollen-limited. Reproduction had increased by pollinator-mediated facilitation by both con- and heterospecific neighbours which may lead to (community-level) Allee effects. Pollination-independent interactions, such as amelioration of abiotic conditions through neighbours, contributed to additional positive neighbour effects. However, these pollination-independent interactions were weaker than the pollination-mediated interactions and they occurred over smaller spatial scales. Finally, the strength and direction of neighbourhood effects depended on neighbour traits and thus changed with the trait composition of the neighbourhood. 5. Synthesis. By manipulating both pollen availability and target plant locations within neighbourhoods, we can comprehensively analyse spatially-explicit density-dependence of plant reproduction. This experimental approach enhances our ability to understand the dynamics of sparse populations and of species’ geographical ranges
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AoB PLANTS, 2019
Plant invasions are prime opportunities for studying hybridization and the nature of species boun... more Plant invasions are prime opportunities for studying hybridization and the nature of species boundaries, but hybrids also complicate the taxonomic treatment and management of introduced taxa. In this study, we use population genomics to estimate the extent of genomic admixture and test for its association with morphology and genome size in a hybrid complex of knapweeds invasive to North America: meadow knapweed (Centaurea × moncktonii) and its parental species (C. jacea and C. nigra). We sampled 20 populations from New York and Vermont, USA, and used genotyping by sequencing to identify single nucleotide polymorphisms in order to estimate genome-wide ancestry and classify individuals into hybrid genotype classes. We then tested for association between degree of genomic introgression and variation in a subset of traits diagnostic for the parental taxa, namely capitula morphology and monoploid genome size. Genomic clustering revealed two clearly defined lineages, as well as many admix...
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Basic and Applied Ecology, 2018
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Plant Biology, 2016
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Oikos, 2016
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Weltweit steht die Biodiversität unter dem Druck anthropogener Umweltveränderungen. In diesem Kon... more Weltweit steht die Biodiversität unter dem Druck anthropogener Umweltveränderungen. In diesem Kontext stellen seltene oder zurückgehende Arten gegenüber invasiven Arten die entgegengesetzten Enden eines Gradienten demographischen Erfolgs dar. Diese Habilitationsschrift umfasst konzeptionelle und empirische Forschungsarbeiten zu fünf Phänomenen, die die ökoevolutionäre Dynamik natürlicher Pflanzenpopulationen unter globalem Umweltwandel adressieren: 1) anthropogene Veränderungen biotischer und abiotischer Umwelten, 2) demographische und genetische Flaschenhälse 3) Inzuchtdepression und Inzucht-Umwelt-Interaktionen, 4) interspezifische Hybridisierung vormals isolierter Taxa, 5) und letztlich veränderte evolutionäre Trajektorien. Zusammenfassend lässt sich sagen, dass die in dieser Arbeit zusammengetragene Forschung zu einem allgemeineren Verständnis der wichtigen Rolle ökoevolutionärer Prozesse für den demographischen Erfolg und das Managements abnehmender und invasiver Arten beiträgt.
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Papers by Susanne Lachmuth