local adaptation
Note: I am inexperienced at blogging my research concepts and ideas, so please bear with me. I really appreciate any comments or questions. Please don't be shy.
The main concept behind my proposal is local adaptation.
Local adaptation is when a population evolves and adaptation to the ecological conditions in its local environment. The adaptation to these ecological conditions is driven by natural selection. The classic example of local adaptation comes from work done on black pine leaf scale insects, Nuculaspis californica, on pine trees. In the pine stands where these scales occur some trees have high infestations of scales while others are left unscathed. This lead to the hypothesis that these scales (and their descendants) were adapting to individual trees. To test this hypothesis scales were transferred from their natal tree to a novel tree. The scales experienced high mortality on the novel host. After these reciprocal transplant experiments, it was concluded that N. californica scale populations had adapted to survive on individual trees within a pine stand. These immobile scales had adapted to to the defensive properties of their natal tree (Edmunds & Alstad 1978).
One of the reason there is a great deal of interest in local adaptation is that it has been considered a stepping stone to speciation (Dres & Mallet 2002). I have made sense of the slippery slope of local adaptation by visualizing an adaptation continuum:
It is important to point out is that not all organisms will follow this continuum. Some species may never become locally adapted or speciate. This leads to another tangent that I will discuss in future posts – why are some groups of organisms so specious while others (say, for example, insects), while others have only one of a few species (sponges, for example). In this continuum an population can be adapted to extant conditions but not locally adapted. The population is not locally adapted because the mean fitness of the population is the same as any other population in that environment. The population is locally adapted when its mean fitness is higher than the mean fitness of other populations:
Here you can see that the fitness of populations fluctuate over time but a locally adapted population experiences higher mean fitness relative to the other populations.
How's that for a start?
The main concept behind my proposal is local adaptation.
Local adaptation is when a population evolves and adaptation to the ecological conditions in its local environment. The adaptation to these ecological conditions is driven by natural selection. The classic example of local adaptation comes from work done on black pine leaf scale insects, Nuculaspis californica, on pine trees. In the pine stands where these scales occur some trees have high infestations of scales while others are left unscathed. This lead to the hypothesis that these scales (and their descendants) were adapting to individual trees. To test this hypothesis scales were transferred from their natal tree to a novel tree. The scales experienced high mortality on the novel host. After these reciprocal transplant experiments, it was concluded that N. californica scale populations had adapted to survive on individual trees within a pine stand. These immobile scales had adapted to to the defensive properties of their natal tree (Edmunds & Alstad 1978).
One of the reason there is a great deal of interest in local adaptation is that it has been considered a stepping stone to speciation (Dres & Mallet 2002). I have made sense of the slippery slope of local adaptation by visualizing an adaptation continuum:
It is important to point out is that not all organisms will follow this continuum. Some species may never become locally adapted or speciate. This leads to another tangent that I will discuss in future posts – why are some groups of organisms so specious while others (say, for example, insects), while others have only one of a few species (sponges, for example). In this continuum an population can be adapted to extant conditions but not locally adapted. The population is not locally adapted because the mean fitness of the population is the same as any other population in that environment. The population is locally adapted when its mean fitness is higher than the mean fitness of other populations:
Here you can see that the fitness of populations fluctuate over time but a locally adapted population experiences higher mean fitness relative to the other populations.
How's that for a start?
posted by bugheart at 8:12 PM
2 Comments:
YAY! I can't wait to hear more specifics....like more on your chosen model system. Hooray for your proposal!! We missed you yesterday,
:( but hopefully you were able to get crankin' post-junkyard. :)
-Michelle
I follow you up until after the italics. What do you mean by "in this continuum [a] population can be adapted to extant conditions but not locally adapted"? It seems that at some point in this continuum, a population must be locally adapted. I feel like I missed the beginning of your argument somewhere.
Oh, and the comment about why some groups have a huge expansion and others don't is a great question! Charlie has done some wonderful work with that.
I'd love to discuss your ideas for you last graph. I have to admit that I see the difference between locally adapted and host races as due to a lack of gene flow rather than higher fitness, but this would be good to talk about.
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