Population biolog​y

We study the spatial population dynamics of closely interacting species in a fragmented landscape.  This work is rooted in: (1) long-term monitoring of the butterfly Melitaea cinixa and its parasitoids in the Åland islands, (2) detailed study of the behavior and natural history of individual species, and (3) population genetics tools. We have shown that parasitoid metapopulation dynamics are influenced by host dynamics and habitat connectivity, as well as host plant species, hyperparasitism, competition, temperature mediated phenology, and more recently a plant pathogenic fungus.
Three ongoing projects are:

The effects of species interaction and spatial structure of the landscape on population dynamics and genetic structure.

The population dynamics of species depend on the distribution and stability of resources and enemies, population size and the extent to which individuals move between resource patches. It isn’t simple to disentangle what biotic and abiotic factors go into explaining the dynamics of species. A recent study showed that increasing synchrony of population dynamics of the butterfly M. cinxia can be explained by weather extremes, and not interaction with natural enemies.

Increasing synchrony of butterfly population dynamics are associated with increasing synchrony in weather.

Kahilainen, A., van Nouhuys, S., Schulz, T. & Saastamoinen, M. 2018
Metapopulation dynamics in a changing climate: Increasing spatial synchrony in weather conditions drives metapopulation synchrony of a butterfly inhabiting a fragmented landscape
Global Change Biology, 24: 10.1111/gcb.14280

We are also using Population genetics tools to exploring the association of population structure with environment (such a habitat connectivity), resource distribution (host population dynamics), life history (i.e. population size and sex ratio), and interactions such as competition (we are using primarily neutral microsatellite markers) of the butterfly M. cinxia and its parasitoids in a landscape.

One clear pattern is that higher trophic level species have lower spatial genetic structure.  This is not surprising because as trophic level increases the resource becomes sparse and unpredictable, so individuals must be mobile, leading to population mixing.

Multilocus genetic clusters for each species mapped onto the map of the Åland islands

Wang, S., Brose, U., van Nouhuys, S., Holt, R. D. and Loreau, M. 2021 Metapopulation capacity determines food chain length in fragmented landscapes. Proceedings of the National Academy of Sciences, 118, e2102733118.

Duplouy, A., Nair, A., Nyman, T., van Nouhuys, S. 2021
Long-term spatiotemporal genetic structure of an accidental parasitoid introduction, and local changes in prevalence of its associated Wolbachia symbiont. Molecular Ecology, 30, 4368-4380

Opedal, Ø., Ovaskainen, O., Saastamoinen, M., Laine, A-L., van Nouhuys, S. 2020
Host plant availability drives the spatio-temporal dynamics of interacting metapopulations across a fragmented landscape.
Ecology, 101(12):e03186. 10.1002/ecy.3186

55. Nair, A., Nonaka , E., van Nouhuys, S.  2018
Increased fluctuation in a butterfly metapopulation leads to diploid males and decline of a hyperparasitoid
Proceedings of the Royal Society B, 285: 10.1098/rspb.2018.0372

Nair, A., Fountain, T., Ikonen, S., Ojanen, S. P., van Nouhuys, S. 2016. Spatial and temporal genetic structure at the fourth trophic level in a fragmented landscape. Proceedings of the Royal Society B, 283: 10.1098/rspb.2016.0668

Couchoux,, C., Seppä, P., van Nouhuys,, S. 2016. Strong dispersal in a parasitoid wasp overwhelms habitat fragmentation and host population dynamics.  Molecular Ecology,  doi: 10.1111/mec.13696

van Nouhuys, S. 2016.  Diversity, population structure and individual behavior of parasitoids as seen using molecular markers. Current opinions in Insect Science 14: 94-99.

Couchoux, C., Seppä, P., van Nouhuys, S. 2015. Microsatellites for the parasitoid wasp Hyposoter horticola. Conservation Genetics Resources, 7: 595-597 

Nair, A., van Nouhuys, S. 2015. Microsatellite markers for a hyperparasitoid wasp from a fragmented landscape. Conservation Genetics Resources, 7: 565-586

Kankare, M., van Nouhuys, S., Gaggiotti, O., Hanski, I. 2005. Metapopulation genetic structure of two coexisting parasitoids of the Glanville fritillary butterfly. Oecologia, 143: 77-84