Re: Re: HYB: ploidy - speculation

In a message dated 1/1/02 7:35:10 AM Mountain Standard Time, 
lmann@volfirst.net writes:


> Unless Sharon has time & is willing to step in and once again attempt to
> translate my thought here into technically useful English! <g>

Only a thumbnail sketch today....

I think you're referring to a long-ago discussion of karyotype analysis and 
the role of homologous chromosomes in inter-species compatibility.  Counting 
chromosomes is just the first step.  Identification of individual ones and 
comparing size and shape both within a set and with chromosomes 
characteristic of other species can reveal a great deal about compatibility 
and the evolutionary process. 

The key point:  although species do have some distinctive chromosomes, they 
also have some that are quite similar to those of their relatives.  Species 
with a high proportion of compatible sets cross with relative ease, while 
those with fewer like sets pose a greater challenge.  

Further along the spectrum, species with a low proportion of compatible sets 
sometimes produce amphidiploid offspring.  The stoloniferabreds and 
hoogianabreds are a commonly cited example -- but relatively few have been 
introduced and those with whom I've discussed these lines have shared my 
experience that such crosses are much less productive than work within either 
of the parental families.  

Both the normal functioning of homologous chromosomes and the phenomenon of 
amphidiploidlike breeding behavior have played important roles in the 
development of today's iris, but I think it will be easier if we discuss them 
separately here.

Sharon McAllister



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