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Making an orchid family tree

Updated Tuesday 11th December 2007

Imagine there were 19,000 relatives in your family - and you had to make a family tree showing how they were all related…

Recently I attended a conference on orchids at Kew Gardens, it covered all aspects of orchid biology but concentrated on phylogeny (how they are all related to each other). In recent years it has become possible to look at exactly how each species or indeed each individual plant or animal is related to all others using similarities and differences in their DNA. Well in theory all of this is possible but in practice its not so easy.

A large family tree showing the position of all plant families has been produced and beyond this many of the plant families have been broken down into smaller and smaller branches some even showing exactly how each species is related to each other. The orchids are one of the largest plant families containing many thousands of species so it’s a huge task to fill in all the branches of their family tree – imagine there were 19,000 relatives in your family and you had to make a family tree showing how they were all related to each other. At the moment many of the higher level branches have been slotted in showing where groups of species fit and within a few of these groups the smaller branches and twigs down to species level have been done.

One of the most interesting things for me was to see that these marvellous DNA techniques actually failed to tell the difference between some of our most distinctive orchids which are easy to tell apart just by looking at them. For example, take a look The examples below are all orchids of the genus Ophrys, they look similar but we can see they are different and the insects that pollinate them can probably tell they are different too. However the usual DNA techniques have difficulty distinguishing the species. One theory to explain the finding is that this group are rapidly evolving and so there has not been enough time for the small mutations to build up that the DNA techniques use to tell the species apart.

Ophrys lutea Copyrighted image Icon Copyright: Used with permission

Ophrys lutea and Ophrys tenthredinifera,
[Image: Juan Sanchez used under Creative Commons licence]


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