Monday, August 11, 2008

Coldhouse grown Lophophora williamsii - the next generation

Four years ago I started my first batch of coldhouse grown Lophophora williamsii (SB 854; Starr Co, Texas) from seed. I've lost a few plants to frost during the years but the survivors have coped surprisingly well, enduring the Danish winters in an unheated greenhouse without problems (that being said, I still worry a bit for the plants every winter ;-).

Flowering Lophophora williamsii (SB 854; Starr Co, Texas)
Flowering Lophophora williamsii (SB 854; Starr Co, Texas)

The plants are now old enough to flower and have been doing so freely all summer. The above photo was taken late June and today the plants are still flowering.

I have pollinated as many flowers as possible - if more plants flower at the same time the flowers are cross-pollinated, otherwise selfed. A cotton-tipped swab can be used for transferring the pollen from the anther and deposit it on the stigma.

Lophophora williamsii pollinated with the help of a Q-tip
Lophophora williamsii pollinated with the help of a Q-tip

Lophophora williamsii with pollen deposited on the stigma
Lophophora williamsii with pollen deposited on the stigma

The plants have already set the first fruits (the picture below was taken at the end of July) - I can't say if these fruits are the result of the flowers being pollinated 5 weeks before, but I'm currently conducting some experiments to get a better understanding of how much time passes between a flower is pollinated and the resulting fruit appears.

Fruiting Lophophora williamsii
Fruiting Lophophora williamsii

As mentioned above I cross-pollinate my Lophophora williamsii plants when possible (I don't cross plants from different locations though). This might be a waste of time as preliminary studies by Martin Terry indicate that outcrossing is close to zero (i.e. selfing is virtually 100%) in natural populations and all individuals in a given population are clones. The study is based on data from three Texan populations, including Starr County, and the results are not definite - but if the results are correct it would also mean that my surviving (Starr County) plants are not more fit for the coldhouse, genetically speaking, than the ones that died off as they are/were all clones... and I thought I was witnessing a live "selection of the fittest" drama. Anyway, I'll harvest the seed soon to start the next generation of coldhouse grown Lophophora williamsii ;-)

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Read the comments for a discussion on the use of the word "clone".

9 comments:

  1. interesting experiment! Good luck in the coldhouse!

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  2. Great Site, particularly as I share your passon for lophophora. I have a species I am struggling to identify, it has white seed pods, could I send you a photo? Also wondering if you would like to swop seeds? I think I have near on 1000 loph now :) Can we exchange some tips and images via email?

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  3. My genetics need some dusting but, if I remember correctly, plants grown from seed are never "clones" of the parent plant. Meiosis provides a [relatively] random set of genes for boht gametes that, once recombined, differ from the parent plant's. That could account for differences in frost-resistance. On the other hand, this "inbreeding" could (theoretically), in time, condemn a given population to extinction if no outcrossing occurs, as the gene pool thins out slightly for every generation that passes.

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  4. sclaws, you can reach me via the email address "lophophora [dot] blog [at] gmail [dot] com". Alternatively you can post the photos at the Lophophora discussion group.

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  5. Z, that's a very good point, but as I understand Martin Terry's results inbreeding has already taken its toll on the genetic diversity of the Texan Lophophora populations. In his PhD dissertation Terry writes "In contrast [to Astrophytum asterias], with a primarily autogamous cactus like Lophophora, we would expect to see minimal mixing of alleles within a population, virtually no mixing of alleles between populations, very low levels of heterozygosity, and relatively low numbers of alleles per locus, as many ancestral alleles would have gone to fixation in the form of homozygotes or gone to extinction, due to the extreme degree of inbreeding which selfing constitutes. And that is indeed what we observe in the Lophophora data: genetic monotony confined to a single homozygotic genotype within each population, with some variation between distant populations, but variation only in the sense of a shift from 100% homozygotes of one allele in one population to 100% homozygotes of a different allele in another population (the difference in identity of the fixed alleles being attributable to genetic drift)." In an email correspondence I asked Martin Terry if his preliminary results suggest that all individuals in a given (Texan) population are essentially clones to which he answered in the affirmative, explaining that they got that genetic profile by virtue of having adopted the habit of self-fertilization (the ultimate case of inbreeding) as their primary mode of reproduction.

    That being said, I'm by no means an expert on genetics and might very well have misunderstood some of the details (in which case I would appreciate being corrected ;-). The results I'm referring to are from the chapter on Population genetics of Lophophora williamsii in Martin Terry's PhD dissertation A tale of two cacti: studies in Astrophytum asterias and Lophophora williamsii. I hope that Martin Terry follows up on these results in future articles.

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  6. You're right, I did not consider time. It seems that evolution took care of the inbreeding problem and "streamlined" the DNA of every population to a viable and stable set of characters. That is very good news for us. :)

    (thank you for the link to Terry's dissertation, it seems to be very informative and entertaining)

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  7. My cactus has finally flowered after about 5 years. In Australia see www.bluesbirds.blogspot.com for photo.

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  8. Nice plant - good luck with its continued growth.

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