Thursday, 8 July 2010

Eight Roadside Wattles









It stopped raining in the Kimberley today, but tonight we expect more of the rain that doesn't fall during the dry season.

The road we wanted to travel today was closed so we made do with a short trip to the Ngumpan Cliff area west of Fitzroy Crossing. It turned out to be a day of wattles.

Along the roadside I saw eight different wattles in the 70 km stretch. I could only identify a couple of them: Acacia colei, Acacia tumida and Vachellia farnesiana if that is the right name now that most of the Australia species are Acacia and the rest of the world has mostly other genera (with 'farnesiana' one of our foreign origin species).

Until recently, our wattles were part of a large world-wide genus called Acacia, with 1200-1300 species worldwide. As most people now now, this group has been recently divided up into five or more different genera, and we’ve kept the name Acacia for Australia’s 950 species (98% in Australia only - less than 20 grow outside Australia as well – Asia, Pacific Islands and through to Madagascar).

The other genera are Senagalia in the Americas (123 spp.), Africa (69), Asia (43) and Australia (2); Vachellia in Africa (73 spp.), Americas (60, Asia (36) and Australia (9 – all tropical except farnesiana which is probably weedy); as well as Acaciella and one other genus I don't think has a name, but perhaps it does.... Difficult to appear knowledgeable with limited internet and expert access out here at Fitzroy Crossing.

Briefly, the basis of the name change is as follows. Based on the rules of naming in botany, the name Acacia should technically be applied to the mostly thorny acacias in Africa, America and Asia, with only a few species in Australia (see above).

This is because the species designated as the ‘Type’ of the genus way back when it was described is an African species. If this was the case, most of the 950 species in Australia would then have to change to the name Racosperma.

However there are ways to conserve names if there are good economic, social or other reasons for it. There was and is fierce debate in the scientific community about whether to follow the rules or to be practical about it and try and reduce the impact of the change. It isn’t as simple as it sounds – some of the arguments:
o Vast majority of species in Australia (13 to 1 ratio)
o But public perception of acacia in much of the world is the thorny trees in Africa
o In Africa half of there species will be split into one of the other new genera (so there will be a lot of change anyway).
o Acacias are ecologically, economically and scientifically important wherever they grow – this argument has been used on both sides
o Adding up the number of books that refer to acacia in Australia and elsewhere – comes out pretty even.
o Accepting exceptions like this will destabilise the whole set of botanical naming rules – but this is seen as an exception where nearly a thousand species would be effected by the change.

It was a close finish, but in 2005 an international committee that looks after plant names voted to keep Acacia for the Australian representatives, and to generalise, Africans, Americans and Asians had to use new names for their wattles.

So here I am in Fitzroy Crossing with fragments of eight species, most of which I can call Acacia (only one I can't) but very few of which I can put on species names. Anyway, they look quite pretty on the hotel desk.

Images: Three of the eight wattles (it would take too long to load them all...) and the Ngumpan Cliff. The wattle without the flowers is not an Acacia in its new, narrower, sense, and probably not growing in Australia until more recent times (i.e. an introduced weed).

2 comments:

Delphine said...

I love your blog so much !! i feel your passion for plant in every post. Thank you for making me discover Australia. A warm regard from Paris, France.

Tim Entwisle said...

Thanks Delphine! I have a few more pictures from around Broome I hope to post later, but poor connectin here (and being told I need to holiday!). Good to get feedback.