Step into the rainforests of the Daintree lowlands at the moment and you’re likely to whiff the pervasive scent of the rare Javan Ash (Ryparosa javanica). The abundant flowering emits a sweet, slightly off-smell, like five-day-old socks or raw hamburger mince.
The Javan Ash is found in both Java and Australia. This forms evidence of the mixing of the continental biota of the Australian and Asian plates, which are believed to have collided about fifteen million years ago, in the vicinity of what is now the Timor region.
As a defence against herbivores, these plants emit the poisonous gas Hydrogen Cyanide (HCN), through a process called ‘cyanogenesis’.
HCN is poisonous, not only to animals that the eat plants, but to the plants themselves. To prevent poisoning themselves, the plants limit the production of HCN through the strategic storage of both cyanogenic glycosides and an enzyme in adjacent vacuoles of the cell. When the cell is damaged the compartment walls are breached and the reaction takes place. In this way, HCN is produced only when needed.
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
The interactions between herbivores and plants toxic defence systems are always very interesting.
In South America, the tapirs are eating toxic leaves and as a means to neutralize the toxins they are eating a special mud…
But it looks so darn pretty. Reminds me of Bo Derek’s hair.
In the year 2000 I posted an image on wikipedia of a growth that I found on a Ryparosa javanica hoping to get it identified.
Seven years older, but no wiser, I thought it worth giving it another shot. I think it’s part of the growth of the tree, the stem looks similar, but it is not the normal fruiting body and with hundreds of trees to look at daily, I have not seen it again.
I am asking Neil, most humbly, if he will post my image on the blog, since I remain unempowered in the blogging process.
Hi Neil,
I thought you might like to hear that the Ryparosa species found in the Daintree is now known as Ryparosa kurrangii and has only been reported from the lowland regions of the three valleys between Alexandra Heights and Cape Tribulation. While it is clearly related to the other Ryparosa species in Java, these are now considered separate species.
Thanks Bruce,
Do you know if ‘kurrangii’ is derived from the Kuku Yalanji ‘karanji’ (cassowary)?
Hi Neil, Yep, you are right on the money there. I thought it would be an appropriate name for the Australian Ryparosa given (i) the apparent association between successful germination of R. kurrangii seeds and cassowary gut passage, and (ii) that the Kuku Yalangi refer to a prominent local feature (Cape Tribulation) by this term.
I wonder Bruce, if, in time, your nomenclature will have the species become known commonly as the cassowary ash (Javan Ash would seem to have become inappropriate). Of course, this is a little close to cassowary satinash (Acmena graveolens), so it may need another descriptor. Any suggestions/preferences?
Hi Neil,
Personally, I think the less ambiguous a common name is, the better – common names aren’t really needed either. I also think the ‘it looks like an ash back home so lets call it an ash’ colonial approach is a bit dated. Not only that, but it doesn’t seem a very appropriate term to use for Ryparosa. It seems that the origins of the word ash (as applied to trees) relates back to the old spear shafts used in medieval times, which were often made from Oleaceae (Fraxinus – Ash) wood. Ryparosa wood is certainly not hard and it doesn’t even have the pinnate leaves that Fraxinus has either….
So I agree that the term ‘Javan Ash’ is not appropriate to use for R. kurrangii, although the only place I have ever seen ‘Javan Ash’ written was on a rotting trail sign at the Coconut Beach resort so I’m not even sure how widespread that term is or where it originates from.
Is there a need to have a common name? While trying to come up with an appropriate species name, I asked the Kuku Yalangi if they had a common term for the tree, but we weren’t able to find out if there ever was one. As for using the term ‘cassowary’, so many large-fruited Daintree species depend on the cassowary for long-distance seed dispersal (and perhaps many more may also benefit from cassowary gut-passage), so I don’t think this relationship between Ryparosa and the cassowary is unique enough to consider calling it the ‘cassowary tree’ or something similar. I personally think ‘Australian Ryparosa’ would be an adequate, geographically informative and unambiguous common name if one is needed, because as far as we know there is only one Ryparosa species found in Australia.
Anyway, there’s my two bobs worth! Readers might be interested in this following link too regarding scientific and common names for plants: http://www.swcoloradowildflowers.com/plant%20names.htm