One of the points I think has been missed in the discussions of the latest artilce with the earlier splitting then re-lumping of Cattleya Alliance species in the recent series of articles is this.
The first passes through on orchid molecular taxonomy were done on analysis done with a SINGLE DATA SET. This could be interpreted as the coding for a single enzyme or protien, a single DNA sequence. This is not the whole genome. The big problem was in Cattleya maxina, to make it fit, you had to do weird things with Laelia to make Cattleya maxima fit in the genus Cattleya. Next generation of these studies were done with 2 data sets, meaning the coding for two separate enzymes or protiens. The DNA coding these enzymes or protiens are probably on different chromosomes. This requires double the lab cost and the square of the computer power. So initially this work was done as a single data set for all and the second data set test done on select problem species. As the cost, time and ease of the techniques made things more affordable, more testing was done. Now this latest article is unique in that THREE data sets were employed. Three enzymes, three different DNA sequences, three times the lab effort and cube the computing power required. So the result is more scientifically robust, and in some ways it moves us back to more sensible lumping of species. As a separate thought. In most plant groups, species that interbreed easily are usually put in the same genus. In most plant groups intergeneric crosses are difficult. In orchids, especially the Cattleya alliance, interbreeding between genera seems easy. This may be an indication that too much taxonomic splitting has been done. The 3 data set that says the main Cattleya Alliance genera all should be moved back into Cattleya makes some sense supported by the fact that intergeneric hybrid are so easy and quite fertile between these groups. Potinara and other quadrageneric hybrids really should not be so easy to make if the genera were truely evolutionarily separate. It's all Cattleya makes some sense, understanding that 'all' is not absolute. I suspect things like Leptotes or some of the other minors are different enough that they will stand after the more thorough DNA treatment. So I think the point is - taxonomic revisions based on molecular cladistics should NEVER have been made until the technique was refined more and made more robust. Until the costs come down, and the DNA data set libraries are built up enough, I am not changing any labels on my plants simply because of a single study of a single data set. Molecular cladistics is an immature science, particuarly in orchids, the libraries of DNA sequences are too limited. Not enough of the orchid genomes are cataloged to make molecular cladistics as strong as the old fasioned phenotype trait based taxonomy. Someday in the future things will be different. Using DNA is not as simple as the Maury Povich Show makes it seem to be. You are NOT the father! _______________________________________________ the OrchidGuide Digest (OGD) [email protected] http://orchidguide.com/mailman/listinfo/orchids_orchidguide.com
