>>I have a question I would like to ask the group about species >>and
>>niches. Basically what I have on my mind is this, In any
>>given habitat is species diversity limited by ecological niches or by the
>>ability of the genera that lives there to adapt to available niches? Or is
>>the number of occupied niches a factor of time between catastrophic events
>>that wipe the slate clean or at least cut down on species? I ask this
>>because of the differences in fish populations in different areas of the
>>globe. It seems that in some areas niches are filled that are >>blank in
>>other areas. Any one have comments on this?
The evidence seems to point to this, I also think that man has had an effect
on the fish in Asia as 4,000 years of paddy culture has caused the evolution
of rice and also selected for species of fish, crustaceans and plants that
can benefit from this environment and the conditions it creates. As
excellent examples I give the Oryzias group which are egg hangers. They
usually mate and then choose a location to hang their eggs that has a stable
water level and temperature. This group of fish are found throughout SE Asia
and the Indian subcontinent. In Japan they actually are in decline in areas
without rice culture. Likewise the gouramie complex in Asia. These fish also
thrive in paddies and have an extra breathing apparatus that allows them to
survive in oxygen poor environments. Recent research also points to the
construction of bubblenests as a temperature modulation device. The bubbles
actually break up and refract the sun's rays.
Edward Venn
Tokyo Japan
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