The Sweet Zone

You can think of the habitable zone as a region in a multidimensional parameter space on which members of a species do well enough to persist. Move them slowly towards the edge of the zone and they often adapt.  Move them too fast and they can’t, move them too far and they can’t.

Generally speaking, fitness declines as the environment gets farther from the one they’re adapted to.  But there is an important class of exceptions to this generalization.

Describe it.


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31 Responses to The Sweet Zone

  1. reiner Tor says:

    If they were adapted to fierce competition from other species, and get into an environment full of species not adapted to the same thing. It’s like placentals in Australia and South America, or European armies in the Americas or in Tokugawa Japan.

    • reiner Tor says:

      Obviously there was some competition among kangaroos, too, but not nearly as fierce for a number of reasons. (E.g. smaller continent.)

    • Partch says:

      I think you need to clarify a few things.

      Africanized bees in the American south west are much much more aggressive than regular european honey bees. Those aggressive behaviors evolved for a fierce environment in Africa. But, in a less hostile environment, it hurts their fitness. They pay a price every time they attack in the form of dead bees, and they attack way too much. Those traits are quickly evolving away in that region because its very not fit, despite being adapted for much fiercer environment.

      • Reziac says:

        I last worked for a beekeeper about 20 years ago and maybe things have changed, but the factors working against Africanized bees were not fitness related to aggression. In fact by that time they’d pretty much taken over the lower elevations in SoCal, and wild bees were becoming increasingly “mean” as a result.

        But the majority of bees in the Southwest are ‘domesticated’ (that is, managed by humans rather than being wild bees) and two things work against the Africanized type: they’re not cold-tolerant (so a winter with sub-freezing temperatures dramatically reduces their numbers), and even if you’re equipped to manage mean bees, they’re relatively poor honey-producers (so commercial apiaries don’t want ’em). So there’s been selection against Africanized bees, but it has not been due to aggression-related mortality; bees make more bees far faster than they can use ’em up that way.

        • Partch says:

          Thank you. Sounds like you know more about this than I do.

          • Reziac says:

            I worked for beekeepers during the decade that our corner of SoCal got invaded by Africanized bees, so got to see the shift firsthand. The aggression difference is fairly dramatic, but only really evident once they’re disturbed… trouble is more things disturb ’em. They also don’t always go quiescent while swarming. Once they were on the scene, I got run out of the bee yard and had to hightail it for the trailer more than once, doing the same things I’d been doing for years previous (conversely English bees might buzz around a bit but had otherwise ignored me).

            Then I moved up to the high desert where we got really hard winter freezes (-10F) and it sure was nice to only encounter English bees again.

            Should note that English bees with an old or sick queen can also get ‘mean’ but they don’t attack in nearly the numbers nor with nearly the pursuit range. (half a dozen for 25′ vs several hundred for 300′)

    • gcochran9 says:

      Yes, moving somewhere where biological competition is less intense.

      • Woof says:

        It can also help if a new prey animal you’re optimized to exploit moves into a hostile area around the same time you do.

  2. protokol2020 says:

    Seldom, an apparent change for the worse is, in fact, a change for the better. For example on the eve of the KT event, everything looked just normal for a certain mammal. The next morning all Hell broke loose, but now, 66 or so million years later this mammal has a lot of descendants. Thanks mainly to that sudden push to the worse.

    • Woof says:

      A mass extinction of your predators or competitors can make life just easy enough that you can survive in an area that would normally kill you.

  3. TheBalkan says:

    There could to be regions of the space where optimal adaptations converge right?
    How about a class of environments where resource & predation constraints are so relaxed that a broad range of adaptations will do as long as the resource & protection pump remains constant and indifferent (or even patronizing).

    • TheBalkan says:

      Can’t tell if I’m cheating here since I’m thinking about it as a few parameters effectively neutralizing the effects of the other parameters, but really this might just be describing the same region with just a few superficial parameters adjusted and therefore not “too far” or “too fast”.

  4. Erebus says:

    Would the exception happen to be the parasite — that is, parasitic worms, fungi, etc.? If one can infect and rapidly adapt to a new host, different from the host it had originally evolved to take up residence within, then the overall fitness of the species should increase quite dramatically.

    There are, for instance, certain flatworms that evolved in crustaceans and then discovered that they can also live perfectly well inside fish. There are others that evolved in insects and then developed the ability to live in birds.

  5. danodet says:

    Rabits in Australia.

  6. Abraham Lincoln says:



    generalists in a post-cataclysm environment freed of their more specialized competitors

  7. Smithie says:

    Man and animals useful to man.

    Who wants elephantiasis, or malaria? Not me! I’m glad to be out of the tropics, even though I’m not as cold-adapted as a caribou. Regarding useful animals: Asian sea bass are now being grown indoors in Iowa.

  8. bimperwang says:

    MHC stuff and hybrids.

  9. Adaptation often amounts to making the best of a bad situation. A change of the environment to something less bad might be beneficial even to a species adapted to a challenging environment. Or it might not, for instance if rival species would do better in the improved environment.
    (OK, I’m waaay outside my field of expertise here, so please have patience if I write dumb stuff.)

  10. Rick Sint says:

    The trivial case would be a new environment that is just more favorable. But I imagine it can happen even in a new environment that is less favorable. Say the new environment drives evolution toward new capacities that confer huge benefits for totally different problems. Human intelligence might have advanced in various places along this pattern. And you might generalize from changes in the physical environment to the culutral environment. For instance if a foreign population happened to enter a society that directed it toward a certain profession deemed immoral there—but a profession demanding certain desirable traits.

  11. Lior says:

    Moving them away from diseases and parasites who are adapted to them to a place where they are not or where thier diseases can kill the competition.

  12. Erik Sieven says:

    civilization is a situation humans are not adapted to, yet with civilization human population has grown more than before.
    Also in Zoos animals live longer than in the wild.

  13. JP Irwin says:

    You have the perennial pattern of conquerors moving from colder places to warmer places and taking names when they do. Being cold-adapted makes your genetics so bad-ass that you’re able to overcome your lack of adaptation. Witness West Eurasians easily conquering Mexico and settling Texas, despite the fact that they get horrible sunburns and skin damage not being adapted for the extreme (sub)tropical weather.

    This breaks down at the extreme tropical end, it doesn’t matter how smart and mighty you are. A madman like Henry Morton Stanley can drag himself though darkest central Africa, but no non-African population seems to be able to live there long term, even with modern technology.

    • Abraham Lincoln says:

      but no non-African population seems to be able to live there long term, even with modern technology

      That’s where you’re wrong, kiddo. We have terra-forming these days. We can do it, and we can call the process “Floridaniazation”.

    • Max Para says:

      “Skin damage” generally doesn’t wipe out the invading population until long after they had the chance to use their guns, germs and steel against the natives and reproduce themselves, if ever.

    • ThinkingCat says:

      A madman like Henry Morton Stanley can drag himself though darkest central Africa, but no non-African population seems to be able to live there long term, even with modern technology.

      Not really. There were many white colonists in Kisangani which was known as Stanleyville. Same for Lubumbashi which was known as Elizabethville.

  14. albatross says:

    Not just competition. Suppose you evolve in an environment where a major constraint on life is X. Later you find yourself in another environment where a major constraint on life is X, but one that’s not quite so harsh. I think you will do well.

    If the Andes mountains got an invasion of Tibetans, the Tibetans would probably outcompete the Andes Indians. (Or they’d interbreed and make some kind of hybrid super-high-altitude people.)

  15. Lindsey says:

    When population A moves into an environment that’s already been ‘made safe’ by the work of population B. E.g. a group of SSAs would not have produced many/any offspring that survived long enough to reproduce if magically teleported to the Sweden of 3000 years ago, but in the Sweden of today they can pump out kids one after the other and all will be nurtured through to reproduction and beyond by the bountiful welfare state!

  16. Anonymous says:

    Kudzu and zebra muscles. When the change brings you to predator/parasite free habitat. Or where the current climate matches a historical climate to which you remain adapted. Leibig had his law of the minimum, so generally where the limiting factor is much more available(a nutrient) or much less prevalent (a predator.) and other potentially limiting factors are equally or more favorable

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