Paper 30 by T. Hawkins

Dynamics of regional distribution: the core and satellite species hypothesis

By Ilkka Hanski | Foreword by S. Kathleen Lyons | Blog by Tanner Hawkins

Ilkka Hanski was an ecologist at the University of Helsinki. He headed the Metapopulation Research Center until his death in 2016.

S. Kathleen Lyons is an associate professor at the University of Nebraska, and researches the effects of global climate change on diversity patterns.

What determines how species are distributed? The boundaries could be defined spatially, or by interactions with other species. Are those boundaries characteristic of species life history, or are they explained by other factors?

Hanski investigates these questions using a corrected version of Levins’ model of community distribution, which is in turn based on a logistic growth function. The reason behind the modification is that according to Levins’ original model, the distribution of a species is unimodal. That is, in a given region, there is an arbitrary optimal space that a species can occupy. The problem is that that is not empirically true. What tends to happen is that there are low area and high area species. So rather than a unimodal, the distribution is instead bimodal. Hanski calls these satellite and core species. The way he describes it is similar to R and K selected populations, in that there are two viable strategies, and species will over time adapt to be one or the other.

Questions:

The part where I start to be skeptical, is when he claims that K selection is related to core species, and R selection to satellite species. I don’t believe that’s true if you would look outside of animal taxa. I just don’t buy it, and I’d like to at least see where he’s coming from before I write that point off. What was his reasoning?