Jim,
>> I do not believe any consensus exists among
>> scientists as to how much genetic divergence
>> is needed to name a new species.
>It seems like there is consensus that calling something a different
>species hinges on reproductive isolation. The isolation may result from
>actual reproductive incompatibility (ie, genetic difference) or
>spatial-temporal isolation.
There are numerous execptions to the reproductive isolation definition of
species (e.g., coydogs ... coyote - domestic dog offspring that are
fertile) especially when organisms like fungi are considered. I remember
from a mycology class I took a couple of years ago that the entire
taxonomic system for fungi is a hotly contested issue as species are being
reorganized into different families and orders based on genetic mapping.
Some scientists are advocating species designation based on a certain
level of variation in ribosomal DNA, while other mycologists counter that
this approach to species determination makes no practical sense and
advocate a more ecologically based determination. I'm not sure that the
classical explanation of reproductive isolation is still the consensus
view among the scientific community for defining a species. It seems that
consensus is lacking.
Scott Maxwell
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