Nina Gerber & Anouk N'Guyen

Tvärminne, Finland

Picture by Nina & Anouk

Combining different approaches: theory and practice

Combining concepts from different disciplines is a hallmark of mature science and has lead to a bigger understanding of complex problems in biology. We are convinced that combining disciplines is beneficial for understanding complex systems. We aim to combine different methods such as theoretical models, empirical data and transdisciplinary approaches to integrate practitioners. Quantitative models provide new tools for understanding interactions and relationships among biological systems and allow for predicting the behaviour of a system when conditions are manipulated. However, to obtain a deeper understanding of natural systems, insights gained from theoretical models have to be related to real life data. And if we want to be able to make science-based policies that are actually used, we also need to integrate knowledge and values from practitioners. 

After the temporal extinction, wolves are recolonizing the cultural landscape in Germany and the population increases exponentially. This rapid increase of the wolf population is not only a conservation success but is also a major challenge for wolf management. To prevent major human-wolf conflicts and support a successful and permanent reintegration to the ecosystem monitoring population dynamics as well as investigating the consequences of their return is necessary to support management decisions.

Additionally, the recolonization offers a natural system to study the impacts of the return of an apex predator that has been absent for about 150 years. Famous studies in the Yellowstone National Park have shown positive effects of a wolf reintroduction for the whole ecosystem. The cultural landscape of Europe, however, is fundamentally different from the huge open areas in such national parks and there are other dynamics to consider in an intensively managed cultural landscape.  In this project, I will study behavioural patterns wolves in the cultural landscape and wolf-deer interactions and the consequences for wildlife management. Within the project, I will work closely together with Friederike Riesch and Maria Paap, who will focus on different questions around the recolonization of the cultural landscape. Find more information on our project website (currently under construction).

The recolonization of the cultural landscape by Wolves 

photo from WWF US: Wildlife survey 

To use ecosystems sustainably, we have to estimate the capacity of these ecosystems to absorb direct and indirect anthropogenic impacts. This requires accurate ecological models – and more specifically, accurate estimates of demographic parameters such as birth and death rates, immigration and emigration. Estimating these parameters is particularly challenging for organisms with complex life cycles. Most marine species spend different life stages in entirely different locations, moving long distances during juvenile dispersal. The conservation and sustainable use of these species require a quantitative understanding of this complexity, including the scale of larval dispersal, and the rates of survival and mortality as both adults and juveniles.

 

The access multidimensional dataset of the orange clownfish allows me to estimate these demographic parameters using a Bayesian framework while accounting for the uncertainty that is inherent to the study of natural systems. With these parameters, I will parametrise a metapopulation model and estimate the resilience of the system and inform management decisions.​

Connectivity in Metapopulations

Ingestion of microplastic by whales

Microplastic pollution is a hot topic, but for many species, we have yet to find out how they are impacted by it. It is especially difficult to obtain information on how much microplastics (MP) is ingested by whales. In this project, we inferred the potential for MP uptake by cetaceans from the occurrence of MP in their prey species. First, we reviewed information on whale prey species, focussing on common minke and sei whale, for which the most comprehensive quantitative datasets exist. Second, evidence of MP ingestion by their prey species was reviewed.

 

We found common minke whales forage opportunistically on fish from various families such as AmmodytidaeClupeidaeGadidaeEngraulidae, and Osmeridae. Sei whales mostly feed on copepods, Engraulidae, Clupeidae and Scombridae. High levels of MP contamination are reported for Scombridae in the Atlantic and Engraulidae in the Northwest Pacific Ocean. Copepods exhibit low levels of MP ingestion in the Northeast Pacific Ocean. Species-specific prey preferences and feeding strategies imply different cetaceans have varied potential for MP uptake, even if they feed in similar geographic areas.

 

Check out the paper here.

Rewilding Key species in a fragmented landscape

One approach to restore ecosystems is Trophic Rewilding. An assumption of rewilding is that predators or large herbivores have a major effect on the whole ecosystem and facilitate through top-down trophic cascade self-regulating and diverse ecosystem. However, these key species were often lost through human activity and are now reintroduced or protected areas allow them to reestablish populations. I want to examine the potential effects of Wisents on the ecosystem and the potential connectivity of reintroduced populations. For this the Wisent Thal project seems an ideal opportunity.

 

Find more on the Wisent Thal project here.

The evolution of facultative sex

Facultative sex (cyclical parthenogenesis) seems to be a superior solution to the question of having sex or not, and the obvious question arises: why did it evolve relatively rarely? In my Ph.D. project, I tried to find explanations for the presence, absence, and consequences of facultative sex by investigating the conditions that favour its evolution.

 

Daphnia evolved cyclical parthenogenesis and the female’s investment in reproduction with different sex ratios can be easily observed in the field and proved to be an ideal system to study our research questions and combine empirical evidence with theoretical models.

 

Want to learn more? Have a look at my thesis, the original publications of this project or outreach projects or check out the Kokkonuts latest work.

Reproduction in mammals is influenced by three main factors: competitive stress, temperature, and food availability. With a unique data set on house mice, I was investigating the influence of early life conditions together with maternal investment on reproduction and survival later in life. As body mass is often associated with fitness consequences, females have the potential to influence their offspring lifetime fitness through their level of investment, which might interact with effects of population density (a proxy for social stress) and temperature. Our analysis shows that house mice can use population density and temperature as cues for predicting future environmental conditions. This allows a mother to adjust her investment according to the environment in which offspring will breed in order to maximise fitness. Thus, when investigating maternal investment, it is important to consider ecological conditions.


This project is based on the work of a previous Ph.D. student in Anna Lindholms and Barbara Königs group at the University of Zürich.

Maternal effects in house mice

Invasive species are one of the main threats to biodiversity. A recent invader to Swiss waters are gobies, small bottom-dwelling fish originating from the Ponto-Caspian area. Through their interactions with native species, such as competition and predation, they negatively affect local biodiversity. This, in turn, can lead to negative socio-economic impacts through reduced fishing success and management measures to contain the spread of gobies.  

 

Find out more about gobies here.

Impacts & Management of

Invasive GobiEs

The role of smell in

cooperative dilemmas

Reciprocity can explain cooperative behaviour among non-kin, where individuals help others depending on their experience in previous interactions. Norway rats (Rattus norvegicus)cooperate reciprocally according to direct and generalized reciprocity. In a sequence of experiments, we show that altruistic help of rats in an iterated Prisoner’s dilemma paradigm is triggered solely by the receipt of odour cues of a cooperating conspecific. When rats were enabled to help a non-cooperative partner while receiving olfactory information from a rat helping a conspecific in a different room, they helped their non-cooperative partner as if it was a cooperator. We further show that the cues inducing altruistic behaviour are released during the act of cooperation; they do not represent individual identity. Remarkably, olfactory cues are more important for cooperation decisions than direct behavioural cues. This suggests that rats signal their cooperation propensity to social partners, which increases their chances to receive help in return.

 

For more information on cooperation check out Manon Schweinfurth's awesome research