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Biology subjects

van Leeuwen, A.

Publications and source records attributed to van Leeuwen, A..

5 recordsLinked to original sources

In the face of competition, imperfect knowledge can lead to sustainable exploitation of a shared resource.

Overexploitation of a shared resource is a frequent phenomenon among groups of selfish consumers, known as the tragedy of the commons. To avoid "self-damage through self-interest", humans may either defend exclusive access to resources, or collectively adopt advanced cooperative behaviour and carefully designed spatial harvesting strategies to exploit a shared resource sustainably. However, why do many non-human species that are neither social nor territorial also appear to avoid overexploiting resources? This study shows that, even under highly competitive scenarios, cooperation is not necessary to sustainably exploit shared resources if individuals have imperfect knowledge about the distribution of those resources. Poorly informed individuals are more likely to inadvertently exploit resources in peripheral habitats, which may allow for higher resource renewal in the nearby and low-cost habitats, enhancing the sustainability of resource use. As a result, those consumers can achieve a long-term yield that approaches that of cooperative consumers and is higher than omniscient consumers. Ironically, while there might be an evolutionary drive for individuals to make well-informed decisions, consumers of shared resources may be collectively more prosperous when they make decisions based on less information. These findings might explain why apparently sub-optimal consumer behaviour appears so prevalent in nature.

ecology↗

Population regulation in semelparous deep-sea squid is driven by ecological conditions in surface waters and whale predation at depth

Predator-prey interactions present a powerful framework for understanding population regulation in natural systems, including the vast and understudied pelagic deep sea. Oceanic squid are among the most abundant and important species groups in this habitat and function as primary prey for the largest marine top predators, deep-diving cetaceans. At the same time, these cryptic animals are highly data deficient. Insight into the dynamics of deep-sea squid populations and the impacts of predation by top-predators is crucial for designing conservation strategies and developing a general theory of deep-sea ecology. Here, we offer fundamental new insights into how individual life history and predation interact to shape population regulation in deep-sea squid. Using empirical data, we develop a size-structured population model for a highly abundant histioteuthid deep-sea squid. We show that population regulation is driven primarily by conditions experienced as paralarvae in the upper water column, where they face intense resource competition. Relaxation of this competition following ontogenetic migration as juveniles drives exponential-like growth curves. Population dynamics exhibit single-cohort cycles, producing regular seasonal patterns in reproduction, even in the absence of any environmental seasonality. Furthermore, we demonstrate that predation by deep-diving cetaceans at different depths can lead to emergent facilitation between top predators. This reveals the complex interdependencies in trophic networks connecting the deep sea with surface waters. Our findings provide critical insights into the ecological functioning of the pelagic deep-sea and their link with surface waters. These insights are urgently needed to better understand and conserve this vast, data-deficient habitat, which endangered deep-diving predators depend on but is under major stress from anthropogenic activities.

ecology↗

Local reflects global: Life-stage dependent changes in the phenology of coastal habitat use by North Sea herring

Climate warming is affecting the suitability and utilisation of coastal habitats by marine fishes around the world. Phenological changes are an important indicator of population responses to climate-induced changes but remain difficult to detect in marine fish populations. The design of large-scale monitoring surveys does not allow fine-grained temporal inference of population responses, while the responses of ecologically and economically important species groups such as small pelagic fish are particularly sensitive to temporal resolution. Here, we use the longest, highest-resolution time series of species composition and abundance of marine fishes in northern Europe to detect possible phenological shifts in the small pelagic North Sea herring. We detect a clear forward temporal shift in the phenology of nearshore habitat use by small juvenile North Sea herring. This forward shift can best be explained by changes in water temperatures in the North Sea. We find that reducing the temporal resolution of our data to reflect the resolution typical of larger surveys makes it difficult to detect phenological shifts and drastically reduces the effect sizes of environmental covariates such as seawater temperature. Our study therefore shows how local, long-term, high-resolution time series of fish catches are essential to understand the general phenological responses of marine fishes to climate warming and to define ecological indicators of system-level changes.

ecology↗

Within-host dynamics of virulent viruses in bat reservoirs for emerging zoonotic disease

Bats host virulent zoonotic viruses without experiencing disease. A mechanistic understanding of the impact of bats virus hosting capacities, including uniquely constitutive immune pathways, on cellular-scale viral dynamics is needed to elucidate zoonotic emergence. We carried out virus infectivity assays on bat cell lines expressing induced and constitutive immune phenotypes, then developed a theoretical model of our in vitro system, which we fit to empirical data. Best fit models recapitulated expected immune phenotypes for representative cell lines, supporting robust antiviral defenses in bat cells that correlated with higher estimates for within-host viral propagation rates. In general, heightened immune responses limit pathogen-induced cellular morbidity, which can facilitate the establishment of rapidly-propagating persistent infections within-host. Rapidly-replicating viruses that have evolved with bat immune systems will likely cause enhanced virulence following emergence into secondary hosts with immune systems that diverge from those unique to bats.

ecology↗

EVALUATION OF OSTEOINDUCTIVITY OF DIFFERENT CALCIUM PHOSPHATE AND PTMC-CALCIUM PHOSPHATE COMPOSITE BIOMATERIALS IN A SHEEP MODEL

Osteoinduction refers to de novo bone formation induced by biomaterials in places where physiologically no bone tissue is formed. Biomaterials with osteoinductive capacities have been shown to fill bone defects of critical sizes with ubiquitous new bone formation. Therefore, osteoinduction has been regarded as an important characteristic for biomaterials aiming at bone regeneration. In our study, we tested osteoinductive capacities of different calcium phosphate bioceramic particles, calcium phosphate scaffolds, and porous poly(trimethylene carbonate)(PTMC)-calcium phosphate composite scaffolds in a sheep model. Biphasic calcium phosphate (BCP) particles of 45-150 m and 150-500 m, microporous {beta}-tricalcium phosphate ({beta}-TCP) particles of 45-150 m, non-microporous {beta}-TCP particles of 45-150 m and 150-500 m, and porous {beta}-TCP scaffolds were implanted in sheep long dorsal muscle for three and nine months. Likewise, porous composite scaffolds, in which BCP particles, microporous {beta}-TCP particles and {beta}-TCP particles, all of 45-150 m, had been incorporated into PTMC matrices, were implanted in sheep long dorsal muscle for three and nine months. Porous PTMC scaffolds were implanted as controls. Abundant new bone formation was induced by BCP particles of both size ranges, the {beta}-TCP scaffold was also able to induce new bone formation at both three and nine months follow up, while no new bone formation was induced by the other biomaterials. Implantation of the abovementioned biomaterials led to uneventful degradation of the PTMC matrices and the incorporated calcium phosphate particles, and provoked no obvious tissue reaction. Future studies are needed to determine the optimal composition of composite biomaterials based on PTMC and calcium phosphate to produce osteoinductive composites.

bioengineering↗