Skip to content

Orchid evolution

September 18, 2011

I was recently asked an intelligent question about the orchids’ closest relative, and from what plant it evolved. If one person asks this, I am sure other orchid lovers wonder too.

Evolution involves studies of the DNA which is arranged into chromosomes in the cell nuclei. The DNA is like the blue print for making an organism. By comparing certain sequences of the DNA, one can create a pedigree based on DNA similarities. This can be tested by making DNA analyses of your family members, including some strangers and foreigners. It will show you are more related to your children, uncles and cousins than to foreigners.

The question of time is resolved by studying fossils, where the age of a fossil can be estimated based on the geological layer it is found, often determined by studying ratios of radioactive isotopes in crystals (they change over time).

This article from 2010, based on fossils and a molecular mutation clock, states that all orchids have one ancestor in common dating back some 77 million years ago:
http://www.biomedcentral.com/1471-2148/10/177

According to the Angiosperm Phylogeny Group (2009, Botanical Journal of the Linnean Society 161: 105-121), the orchid family ‘Orchidaceae’ is a part of the Asparagus order ‘Asparagales’. This is also based on DNA sequencing. The ancestor of the orchids is extinct so we do not know exactly what it looked like. This ancestor’s descendants were the lilies on one hand, and the ancestor of the asparagus order and the commelinid plants (gingers, grasses, palms and Commelina) on the other hand. Within the Asparagus order, the orchids branched out early, all other families are on the other branch of the pedigree.

The details were published by Davis et al. (2004) A phylogeny of the monocots…Systematic Botany 29:467-510.

To transform the results in a pedagogic way one can make this simplified conclusion:
‘The grand-grandmother of the orchids was the lilies’ (Liliales) and pandan’s (Pandanales) grandmother. ‘The ancestor of the daylilies, asparagus and sandlilies was the orchids’ sister’.

Helen’s Bulbophyllum (Bulbophyllum helenae) is native to Thailand and the Himalayas, preferring moist environments. It is still in blossom at Dokmai Garden and is a part of the Orchid Ark.

Eric Danell

Advertisements
2 Comments leave one →
  1. Bill Hunter permalink
    September 18, 2011 7:30 PM

    Excellent short answer to an often asked question, thank you.
    Bill Hunter

    • September 18, 2011 7:47 PM

      One may wonder why there are no tree forms of orchids? They are old and they are species rich (at least 22 500 species), and one might speculate that a huge epiphytic orchid may develop into a strangler, but this never happened. Beans, mints, grasses and daisies have their woody and tall tree-like forms, but not the orchids. Maybe there is a lack of lignin making them too weak? Or maybe we should ask why epiphytic forms of beans, mints, grasses and daisies are rare or non-existing? The orchids’ solution to how to reach the sun is either to adapt to low light, or become epiphytic high up in a tree, and then there is no need for a huge energy consuming stem.

      Eric

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: