Sunday, August 2, 2009

are fish become more or less diverse, and why? (freshwater)?


Answers:
Your question seems to be more of an evolutionary one, although the "man-made/developed" answer above could provide a new twist.

Basically, the idea is that stability promotes diversity -- that is, when environments are stable, the playing field for food mates, resources, etc. becomes crowded because everyone has a shot at competing.

When the resources are dominated by one group, others die off unless they have some adaptation that allows them to survive in a niche unoccupied by others. These niches could be things like tall trees (giraffes feed on them with long necks, where zebras do much better than giraffes on grass shoots), hot/cold areas, turbid waters, etc., etc., etc.

The key is stability for these niches -- if cataclysmic changes occur, only the generalists will survive and diversity takes a hit -- witness all the massive die offs that occurred in eons past.

With all this said, freshwater fish are probably enjoying a somewhat stable period of time, and have diversified quite a bit. Whether they will any more is debatable, but this can be taken to an individual environment level -- a waterway may have changes occur that open up new niches or close off existing ones.

Overall, you aren't likely to witness too many evolutionary changes in a lifetime -- it takes at least a handful of generations for some adaptations to occur, and that's the quick end of things.

Hope it helps!
please ask bettachris at his fish forum.

http://www.forumsvibe.com/betta/index.ph.
they seem to be pretty stable to me, but they are breeding new kinds of fish for sport fishing that put up way more fight than older speices.

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