Hybridisation > New Species

[gerald]

Having just read this:

http://www.bbc.co.uk/news/science-environment-42103058

It occurs to me that in so far as plants, or more specifically cactus, are concerned, there's nothing new here. For two different species to interbreed and create a new 'form' which in turn eventually becomes seen as a new species in its own right, isn't uncommon at all - or at least as it seems that way given the number of 'new species' being claimed as by our East European friends!

[Terry S.]

The interesting thing about this Darwin finch hybrid is that it does not back-cross to the female parent, thus genetically isolating the hybrid from the parent. This is unlikely to happen with plant hybrids which will usually back-cross to both parents creating hybrid swarms.

[DaveW]

It often depends on isolation of parts of a previous cline, meaning a population continues to evolve without pollination contact with it's previous forms, therefore becomes a unique entity. In some places often every significant hill contains it's own unique form out of pollinator range of the others.

Much potential habitat of the Cactaceae has never been explored by the botanically inclined. If your taken to a known habitat of a species and ask "what's on the hills over there" you often get the reply "don't know we have never been up them yet".

Also access to many areas is often difficult, particularly for many present day botanists who prefer to stay in hotels and drive everywhere in four wheel drive vehicles, rather than the old days when they hired a burro and took stores to last them weeks or months in habitat out of touch with modern civilisation. Ritter was one such, since he was originally a mining engineer used to being off for on his own for months in unexplored country looking for mineral deposits. These days probably the nearest we have to those people are the E. Europeans who are prepared to rough it and wander off the beaten track to find new plants.

Many new plants are now being discovered as new roads go in, often to things like microwave towers on hills for communications, which allow those areas to now be reached quickly by wheeled transport. Old plants are often rediscovered too when somebody actually retraces old tracks that have been bye passed by modern paved roads.

Also things like "Google Earth" are now being used to locate the type of terrain where the plants are liable to grow, through noting GPS coordinates before a habitat visit and using those to locate the area when in habitat. I was told that a Melocactus was found growing on a certain rock type, therefore Google Earth was used to find all that rock type in the region and noting the GPS coordinates, which when used back in habitat found a few more new Melocactus localities. In fact I was told some of the larger Cerei can now be located in unexplored areas by the shadows they cast at certain times of day on Google Earth and obviously in future the resolution of Google Earth is liable to get even better.

Of course it depends on your concept of species as to what is new, but probably there still are dozens if not a hundred or so new cacti yet waiting to be discovered as the habitats open up. The problem is opening up the countries for development may kill off almost as many old plants as will yet be discovered.

A few now recognised genera, let alone species, may have been the result of hybridisation in the past that have stabilised. Echinocactus grusonii is now thought to be a hybrid between an Echinocactus and a Ferocactus, and one can speculate where Digitostigma and Leuchtenbergia sprang from, if not hybridisation in the dim dark past?

[habanerocat]

Having just read this:

http://www.bbc.co.uk/news/science-environment-42103058

It occurs to me that in so far as plants, or more specifically cactus, are concerned, there's nothing new here. For two different species to interbreed and create a new 'form' which in turn eventually becomes seen as a new species in its own right, isn't uncommon at all - or at least as it seems that way given the number of 'new species' being claimed as by our East European friends!

I read a book on this subject many years ago, so it may be a bit outdated now.

https://www.amazon.com/Beak-Finch-Story ... 067973337X

Very interesting read all the same about "evolution in our time".
Even a mention of the Cactus Finch.

[D^L]

There are arguments that, occasionally, hybridisation occurs together with a polyploidy event. So you have allopolyploids. Here the egg and pollen process retains both or the chromosomes from each pair.
The result is a plant with matching pairs of chromosomes so it can readily breed and since it has a different number of chromosomes it is effectively isolated from the parents.
It has been suggested as the mechanism for hybridisation of very different species. Roy Mottram wrote a note on it- Cactacean 5. I don't believe all he says in it but it is a thought provoking mechanism that could create some of the odd-ball cacti, eg Digitostigma.
Cheers
David Lambie