I am interested in creating realistic simulations of population demographic decline, such as to represent harvesting, disease, invasive species, or habitat degradation. Often in population genetics and even conservation genetics, demographic declines are modeled as occurring instantaneously. What is a more realistic (but very simple) way to model demographic decline that might be applicable to many endangered species? Linear, exponential, logistic? From some species such as Iberian lynx, I might suppose roughly linear, but other species like American chestnut it is exponential or even close to instantaneous. Suggestions? What about in your species of choice?
It depends on the ecology of the species, the method of reproduction, the duration of the reproductive period, the genetic heterogeneity of the offspring (vegetative clonal progeny apomictic offspring, the offspring of self-fertilization, the offspring of intraspecific pollination progeny of interspecific pollination). And of course the ease of living.
I agree, certainly. But is there one shape that seems to be the most common and thus the most representative for a general model?
If one is wanting an output that is useful can inform conservation policy development, then one would not want a general model (which badly applies to everything), but something that can more usefully inform on issues related to species/species groups under consideration. Probably not a very helpful comment - sorry!
Dear Sean: I agree with the others that think that every case need a different model (ad hoc). Any species (or better: each population) must be considered as an individual-based case, constrained by particular environmental events, genetic and demographic forces...
However, you find interesting some papers as http://www.sciencedirect.com/science/article/pii/S0006320797000268
And I heard that a very good and strong software (freeware, of course) to anlyze this data type is "Vortex".
http://vortex10.org/Vortex10.aspx
Good luck!
Federico
Thanks everyone for the suggestions so far. I find it helpful. I do plan to use a software similar to Vortex to model the population. I have some experience with it and like it very much. I also will try a simpler software called "Nemo". And yes, at this point, for vertebrates.
This paper on decline dynamics for vertebrate species could be useful - it describes different curves depending on the pressures experienced by populations, calibrated against over 100 wild vertebrate populations. Could be a good place to start:
http://onlinelibrary.wiley.com/doi/10.1002/ece3.596/abstract
That seems to be a really fantastic reference, Sarah, I will check it out! I appreciate it
Just to follow up with a short summary of the Di Fonza et al 2013 paper, which helped immensely (thanks Sarah!)... The paper presents models of decline with different growth rates, K values, and pressures on the population. The resulting declines were either linear, exponential or quadratic. Linear decline was not observed very commonly. The two most common decline curves were a rapid decrease followed by a leveling off, or a slow decline followed by a sort of tipping point after which rate of decline rapidly increased. It will be a useful paper especially because of realistic values given for r and K. Has anyone else read this paper? Any opinions on it? Thanks everyone.
"I am interested in creating realistic simulations of population demographic decline,"
on decline (only) or on dynamics?
Dear Zsolt, that is a good point. Primarily I am interested to model decline, though actually I will also create some models of decline followed by recovery.
- Badges
- Science method
- Similar topics
- Biological Science
- Ecology