Biology subjects

Drossel, B.

Publications and source records attributed to Drossel, B..

4 recordsLinked to original sources

bioRxiv2022

Shifts from non-obligate generalists to obligate specialists in simulations of mutualistic network assembly

Understanding ecosystem recovery after perturbation is crucial for ecosystem conservation. Mutualisms contribute key functions for plants such as pollination and seed dispersal. We modelled the assembly of mutualistic networks based on trait matching between plants and their animal partners that have different degrees of specialization on plant traits. Additionally, we addressed the role of non-obligate animal mutualists, including facultative mutualists or non-resident species that have their main resources outside the target site. Our computer simulations show that non-obligate animals facilitate network assembly during the early stages, furthering colonization by an increase in niche space and reduced competition. While non-obligate and generalist animals provide most of the fitness benefits to plants in the early stages of the assembly, obligate and specialist animals dominate at the end of the assembly. Our results thus demonstrate the combined occurrence of shifts from diet, trait, and habitat generalists to more specialised animals.

ecology↗

bioRxiv2020

Nested versus independent sampling: Solving the mystery of contradictory species-area relationships

AO_SCPLOWBSTRACTC_SCPLOWSpecies-area relationships (SARs) describe how the number of species increases with the size of the area surveyed, and they usually take the shape of a power law on regional spatial scales. A meta-review of empirical data has shown that the exponent of the power law is on average larger when the areas are sampled in a nested manner, compared to sampling of independent areas such as islands of different sizes. As this is in contrast to ecological reasoning, we performed computer simulations of three qualitatively different models that generate species distributions in space and time by the mechanisms of speciation, dispersal, and extinction. We find that in all cases and over a wide parameter range the SARs obtained by nested sampling have a smaller slope in the regional scale than those obtained by independent sampling. We explain the discrepancy to the empirical data by the different spatial scales on which the two types of empirical investigations were performed.

ecology↗

bioRxiv2019

The concerted emergence of well-known spatial and temporal ecological patterns in an evolutionary food web model in space

Ecological systems show a variety of characteristic patterns of biodiversity in space and time. It is a challenge for theory to find models that can reproduce and explain the observed patterns. Since the advent of island biogeography these models revolve around speciation, dispersal, and extinction, but they usually neglect trophic structure. Here, we propose and study a spatially extended evolutionary food web model that allows us to study large spatial systems with several trophic layers. Our computer simulations show that the model gives rise simultaneously to several biodiversity patterns in space and time, from species abundance distributions to the waxing and waning of geographic ranges. We find that trophic position in the network plays a crucial role when it comes to the time evolution of range sizes, because the trophic context restricts the occurrence and survival of species especially on higher trophic levels.

ecology↗

bioRxiv2019

Impact of herbivore preference on the benefit of plant trait variability

We explore the hypothesis that intraspecific trait variability can be per se beneficial for the plant when the curvature of the herbivore response to this trait is concave downwards. This hypothesis is based on a mathematical relation for non-linear averaging (Jensens inequality), leading to reduced herbivory when the trait distribution becomes broader. Our study introduces and investigates a model for plants and their insect herbivores that includes an unequal distribution of nutrient content between leaves. In contrast to earlier publications, we take into account the ability of herbivores to choose leaves, and the associated costs. By performing computer simulations and analytic calculations, we find that this herbivore preference can considerably alter the conclusion cited above. In particular, we demonstrate that herbivore populations that show preference for leaves on which they grow well can benefit from large nutrient level variability independently of the curvature of the herbivore response function, and despite the cost for preference.

ecology↗