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On Natural Variation in Hoyas

Posted by mikedahms London Ontario (My Page) on
Wed, Oct 19, 11 at 12:06

I was reading this article on natural variation the other day and got to thinking about just how messed up Hoyas are when you consider the frequency that new plants are considered to be new species instead of just natural variations of known ones.
Most recently there was a photo of a very narrow lance shaped leaf of a plant that was collected along with Hoya thompsonii. Now to me this was obviously just a variation of Hoya thompsonii and showed all the characteristics seen in this species but it was listed as an unknown. Granted the plant was not shown to be in flower so the conservative thing to do would be to keep it as an unknown until it can be confirmed but having said that variations in leaf do not make new species. Sadly the Apodagis site seems to be offline, hopefully it is back soon as it is a great resource.

Now the article above is tailored to Aroids and there will be terms used that do not apply to Hoyas. Hoyas also do not show Ontogeny which greatly simplifies identification. Plants like many Aroids and Nepenthes have distinct life stages where the fully mature flowering portion of the plants can look very different from younger plants and in the case of Nepenthes the pitchers used to catch insects can also change quite dramatically on the high climbing or upper portion of the plant vs the initial lower growth.

I would recommend everyone to read this article as it will help in understanding that plants of the same species do not need to look exactly the same. We see this with Hoya carnosa plants that people post, there are many leaf shapes associated with Hoya carnosa but often times people feel that they have something different because it is not the carnosa they are familiar with.
A very good point is made in the article about the collection of plants in the wild. Plant collectors choose the best or most novel specimens to introduce to horticulture, not necessarily the most common form of a species. When Hoyas are concerned, because they are so easily propagated vegetatively one new introduction can spread throughout collections to the exclusion of others. Even though you may get one plant from Thailand and another from Sweden in some cases they may very well be from the same original source.

I hope the article helps in understanding some of the issues faced by Hoya collectors and why the names can seem so confusing. As RFG has pointed out we obviously have many species under the wrong names and others that perhaps should not have been published as new species have been. This all makes me wonder just how many of our "species" are truly hybrids that have developed to be stable over many thousands of years. Still as long as we try our best to follow the rules of nomenclature we have a terrific structure in place to help us discuss these plants.


Follow-Up Postings:

RE: On Natural Variation in Hoyas

Other than DNA testing, the only real way to know your plant is a hybrid or species is if you self it and grow the seeds out. If you selfed it and all the babies come out with different flower shapes and colors, it is most likely a hybrid. Other ways also include. Leaves alone don't make up a species. If you ever selfed Hoya caudata with the speckled reddish leaves, don't be surprised that not a single baby will develop this reddish flecked leaves. All will have mostly a drag olive green leaf and maybe one or two will have a fleck on it. But it is a true species as the flowers will be true.
The finlaysonii, callistophylla, meredithii group are all a bunch of hybrids posing as species. None of them will produce true to type babies from seeds when selfed.

RE: On Natural Variation in Hoyas

I wish we would see DNA analysis used more in Hoya research as it would certainly help in defining the relationships between species and in uncovering the intermediate plants that may very well be hybrids.
Ok I have to try my hand at pollination again, even if only a selfing. I have failed so many times that I had given up but as long as I don't have high expectations what�s to lose? I do foresee serious issues with space if I ever do succeed as I will want to keep and observe a large number of seedlings.


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