Biology subjects

Dieckmann, U.

Publications and source records attributed to Dieckmann, U..

6 recordsLinked to original sources

bioRxiv2023

libpspm: A feature-rich numerical package for solving physiologically structured population models

For a vast majority of organisms, life-history processes depend on their physiological state, such as body size, as well as on their environment. Size-structured population models, or more generally, physiologically structured population models (PSPMs), have emerged as powerful tools for modelling the population dynamics of organisms, as they account for the dependences of growth, mortality, and fecundity rates on an organisms physiological state and capture feedbacks between a populations structure and its environment, including all types of density regulation. However, despite their widespread appeal across biological disciplines, few numerical packages exist for solving PSPMs in an accessible and computationally efficient way. The main reason for this is that PSPMs typically involve solving partial differential equations (PDEs), and no single numerical method works universally best, or even at all, for all PDEs. Here, we present libpspm, a general-purpose numerical library for solving user-defined PSPMs. libpspm provides eight different methods for solving the PDEs underlying PSPMs, including four semi-implicit solvers that can be used for solving stiff problems. Users can choose the desired method without changing the code specifying the PSPM. libpspm allows for predicting the dynamics of multiple physiologically structured or unstructured species, each of which can have its own distinct set of physiological states and demographic functions. By separating model definition from model solution, libpspm can make PSPM-based modelling accessible to non-specialists and thus promote the widespread adoption of PSPMs.

ecology↗

bioRxiv2023

Competition for light can drive adverse species-composition shifts in the Amazon Forest under elevated CO2

The resilience of biodiverse forests to climate change depends on an interplay of adaptive processes operating at multiple temporal and organizational scales. These include short-term acclimation of physiological processes like photosynthesis and respiration, mid-term changes in forest structure due to competition, and long-term changes in community composition arising from competitive exclusion and genetic trait evolution. To investigate the roles of diversity and adaptation for forest resilience, we present Plant-FATE, a parsimonious eco-evolutionary vegetation model. Tested with data from a hyperdiverse Amazonian terra-firme forest, our model accurately predicts multiple emergent ecosystem properties characterizing forest structure and function. Under elevated CO2 conditions, we predict an increase in productivity, leaf area, and aboveground biomass, with the magnitude of this increase declining in nutrient-deprived soils if trees allocate more carbon to the rhizosphere to overcome nutrient limitation. Furthermore, increased aboveground productivity leads to greater competition for light and drives a shift in community composition towards fast-growing but short-lived species characterized by lower wood densities. Such a transition reduces the carbon residence time of woody biomass, dampening carbon-sink strength and potentially rendering the Amazon Forest more vulnerable to future climatic extreme events.

ecology↗

bioRxiv2020

Towards a unified theory of plant photosynthesis and hydraulics

The global carbon and water cycles are governed by the coupling of CO2 and water vapour exchanges through the leaves of terrestrial plants, controlled by plant adaptations to balance carbon gains and hydraulic risks. We introduce a trait-based optimality theory that unifies the treatment of stomatal responses and biochemical acclimation of plants to environments changing on multiple timescales. Tested with experimental data from 18 species, our model successfully predicts the simultaneous decline in carbon assimilation rate, stomatal conductance, and photosynthetic capacity during progressive soil drought. It also correctly predicts the dependencies of gas exchange on atmospheric vapour pressure deficit, temperature, and CO2. Model predictions are also consistent with widely observed empirical patterns, such as the distribution of hydraulic strategies. Our unified theory opens new avenues for reliably modelling the interactive effects of drying soil and rising atmospheric CO2 on global photosynthesis and transpiration.

plant biology↗

bioRxiv2019

Three-phase transitions to reproductive isolation: The roles of utilization mismatch and residual selection

The adaptive emergence of reproductive isolation is increasingly recognized as a key mechanism of sympatric speciation. Here we aim at establishing a deeper understanding of the complex multilocus dynamics underlying such speciation transitions under resource competition. In reality, a single populations resource utilization can never exactly match a resource distribution, making residual selection pressures inevitable. We find that this commonly leads to three-phase transitions to reproductive isolation. First, partial assortativity emerges, quickly adjusting a populations variance to the resource distributions variance. Second, allelic variance slowly erodes across loci, allowing an increasingly bimodal phenotype distribution to emerge. Third, a fast transition occurs toward full bimodality in conjunction with practically complete reproductive isolation of the emerging two species. The first phase is driven by frequency-dependent divergent ecological selection. The second phase is driven by self-accelerating residual ecological selection: the more loci code for the selected phenotype, the slower is this intermediate phase. The third phase is driven by self-accelerating sexual selection. We study three types of mismatch-driven speciation, resulting from (i) incongruences between the shapes of resource distributions and competition kernels, (ii) low numbers of loci, and (iii) premature cessations of the first phases variance expansion. Our results suggest that the incomplete separation of incipient species, a characteristic of the second phase, is common in nature, which is likely resulting in detectable genetic footprints of three-phase transitions to reproductive isolation occurring in nature.

evolutionary biology↗

bioRxiv2018

Emergence of social inequality in a spatial-ecological public goods game

Spatial ecological public goods, such as forests, grasslands, and fish stocks risk being overexploited by selfish consumers, a phenomenon called \"the tragedy of commons\". The spatial and ecological dimensions introduce new features absent in non spatio-ecological contexts, such as consumer mobility, incomplete information availability, and rapid evolution by social learning. It is unclear how these different processes interact to influence the harvesting and dispersal strategies of consumers. To answer these questions, we develop and analyze an individual-based, spatially-structured evolutionary model with explicit resource dynamics. We find that, 1) When harvesting efficiency is low, consumers evolve a sedentary harvesting strategy, with which resources are harvested sustainably, but harvesting rates remain far below their maximum sustainable value. 2) As harvesting efficiency increases, consumers adopt a mobile consume-and-disperse strategy, which is sustainable, equitable, and allows for maximum sustainable yield. 3) Further increase in harvesting efficiency leads to large-scale overexploitation. 4) If costs of dispersal are significant, increased harvesting efficiency also leads to social inequality between frugal sedentary consumers and overexploitative mobile consumers. Whereas overexploitation can occur without social inequality, social inequality always leads to overexploitation. Thus, we identify four conditions, which are characteristic (and as such positive) features of modern societies resulting from technological progress, but also risk promoting social inequality and unsustainable resource use: high harvesting efficiency, moderately low costs of dispersal, high consumer density, and consumers tendency to rapidly adopt new strategies. We also show that access to global information, which is also a feature of modern societies, may help mitigate these risks.

evolutionary biology↗

bioRxiv2017

Ecological, angler and spatial heterogeneity drive social and ecological outcomes in an integrated landscape model of freshwater recreational fisheries

Freshwater recreational fisheries constitute complex adaptive social-ecological systems (SES) where mobile anglers link spatially structured ecosystems. We present a general social-ecological model of a spatial recreational fishery for northern pike (Esox lucius) that included an empirically measured mechanistic utility model driving angler behaviors. We studied emergent properties at the macro-scale (e.g., region) as a result of local-scale fish-angler interactions, while systematically examining key heterogeneities (at the angler and ecosystem level) and sources of uncertainty. We offer three key insights. First, the angler population size and the resulting latent reginal angling effort exerts a much greater impact on the overall regional-level overfishing outcome than any residential pattern (urban or rural), while the residential patterns strongly affects the location of local overfishing pockets. Second, simplifying a heterogeneous angler population to a homogenous one representing the preference and behaviours of an average angler risks severely underestimating landscape-level effort and regional overfishing. Third, we did not find that ecologically more productive lakes were more systematically overexploited than lower-productive lakes. We conclude that understanding regional-level outcomes depends on considering four key ingredients: regional angler population size, the angler population composition, the specific residential pattern in place and spatial ecological variation. Simplification of any of these may obscure important dynamics and render the system prone to collapse.

ecology↗