CactiGuide.com

Don't know if you have seen the flyers for this new alternative to The New Cactus Lexicon to be published next year. It will be available in several languages including English, with a pre publication discount:-

http://cactus-aventures.com/Taxonomy_of ... e_ENG.html" onclick="window.open(this.href);return false;

http://cactus-aventures.com/Taxonomy/DetailENG.html" onclick="window.open(this.href);return false;

They take PayPal, which is handy for currency conversion.

This series should be a welcome addition but the volumes will not answer many of the questions of species relationships. It will certainly help at the generic level and above. Until the limits of presently recognized species are better understood, DNA will not help as much as we would like. The problem of hybridization still continues to mess up DNA studies. This is a bigger headache in some groups like Opuntia and Echinocereus that others but but most groups have their problems. When hybrids are selected to represent a given species in DNA comparisons the results are not to be trusted. All DNA studies suffer an additonal limitation of extremely small sample size at present. I'm still going to want to get this series.
Dean

The problem Dean is past natural hybridity may have been a normal method of ev0lution and produced what we now recognise as valid genera. Backeberg postulated long before DNA studies that some genera of Cerei may have resulted this way in the past. DNA studies tend to indicate e Echinocactus grusonii may be a hybrid between a Ferocactus and an Echinocactus. It has been suggested Astrophytum ornatum may have originally been a hybrid between an Astrophytum and a Ferocactus in the distant past. One wonders whether past hybridity may have given rise to Digitostigma.

I couldn't be sure from the advert--will this new work include keys?

Dave, that is actually not a problem, what I was referring to has occurred in some recent studies (very good ones) where cladistic studies of Opuntia species actually used plants that were not even from the normal range of the species they were supposed to represent in the study and were hybrids. These were specimens contributed by other people to the study and misidentified. My point was that unless you have good representatives of a taxon for comparisons, your DNA results will not be accurate. What this means is that the field work must be done first to provide a good base for the DNA studies not the reverse. All too often now, the people doing DNA cladistic work are not trained in classical biology, taxonomy and field studies. I have many years of experience in DNA and chromosome studies so I understand how it is supposed to work.
Dean

I agree Dean, proper identification of the species is the first requirement for any study to be relevant and plants in cultivation are often a dubious source to use unless they were actually collected in the wild, or from collected seed. There is too much casual propagation in cultivation with few precautions against cross pollination when producing seed for commercial purposes for it to be reliable using most cultivated plants. Also the same presumed species from different localities that would not normally cross pollinate in habitat are often cross pollinated in cultivation to produce viable seed and then their offspring distributed as that species. All DNA studies should ideally be done on habitat material only.