Ph.D. student Nina Holmengen
Field of research
Simulation models for species interactions during external forcing
Mathematically, predator-prey interactions can be described by the Lotka-Volterra model, but real life systems always deviate from this idealized model.
My aim is to incorporate possible effects of predator energy reserves, toxic components accumulated in the system and prey refuges in extensions of simple Lotka-Volterra type models, and compare the simulated results with empirical data, primarily from aquatic systems. Models, in concordance with extensive revision of long time series can yield increased understanding of the underlying mechanisms that affect the character of the interactions.
Species interactions are strongly affected by intrinsic properties of the species involved and by extrinsic properties of the environment. I will in my Ph.D. study some of these factors and their impact on the population dynamics in competitive and predator-prey systems.
Throughout the study of population dynamics, there has been much emphasis on consumer-resource (e.g. predator-prey) systems. Freshwater systems are horizontally quite homogenous, and they are habitats for many relatively short-lived individuals, such as phyto- and zooplankton. Thus, long time series containing information on species interactions can be extracted in a relatively short period of time (3-10 years), which makes these ecosystems ideal for studying population dynamics.
The interactions between phytoplankton and herbivorous zooplankton and the interactions between herbivorous and carnivorous zooplankton are both representatives of consumer-resource systems that may be suitable model systems. However, there are also other systems for which there are long time series, e.g., voles, and I will include observations from such systems when pertinent.
Publications
- Holmengen, N. and K.L. Seip (submitted) "The effect of energy reserves on inter-specific competition in cladocerans." Verh. Internat. Verein. Limnol. (Conference proceedings)
- K. L. Seip and N. Holmengen (submitted) "Changes in interaction dynamics among functional species groups. The case of Lake Washington." Verh. Internat. Verein. Limnol. (Conference proceedings)
- Holmengen, N., K.L. Seip, M. Boyce, and N. C. Stenseth (submitted)"Predator-prey coupling: interaction between mink (Mustela vison) and muskrat (Ondatra zibethicus) across Canada." Ecology Letters.
- Holmengen, N. and K.L. Seip (In prep) "Forecasting species interactions from predictable cycle characteristics."
- Manuscript 2005: "Predator feeding strategy and energy storages-effects on predator and prey density and survival".