The success of invasivness of the Bermuda Buttercup (Oxalis)

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The success of invasivness of the Bermuda Buttercup (Oxalis)

Post by MWP admin » Sun Dec 18, 2005 10:57 pm

I want to discuss with you one of my most intriguing questions regarding Maltese flora. How did the seedless Oxalis pes-caprae (Bermuda buttercup / Haxixa Ingliza) manage to spread practically to every corner of the Maltese islands? Aaah - it is also thought that from Malta it spread and became naturalised throughout the whole Mediterranean basin !!!


Your opinions are all welcomed.



Let us put some facts.
-----------------------------
Next year, we would probably celabrate the 2nd century (200 yrs) anniversary of the presence of Oxalis pes-caprae in Malta. It is believed that it was introduced as a single (or few individual) plant(s) as an ornament flower from Cape Town (S. Africa). This area have a Mediterranean like climate (there are 5 zones describes as Mediterranean climate in the world) and there are plenty of Bermuda Buttercup.

As far as I know, plants were planted mostly at the Argotti gardens, Floriana, but it was reported to have escaped and hence the tragedy to Maltese flora - it has invaded the whole islands being of detriment to other low-growing / fragile maltese flora.

Another fact is that the plant, despite the fertile flowers, seldom make seeds. So propagation is only by root bulbils through soil. Unlike seeding plants, which produce thousands and more of seeds per year, bulb propagation would produce few new plants per year.


This leads to some interesting questions.
-----------------------------------------------------

1) Could mathematically the few introduced species with a low reproductive number per year (via bulbils) result in billions and billions (I cannot really estimate how much) of plants in a turn over of 200 generations (200 years).

2) How could a seedless plant get dispersed in all corners and habitats of the maltese islands such as

- Garigues far away from civilisation
- Wall gaps
- Fortification walls
- Those cliffs and areas where could not be reached by man.
- Individual soil pockets in steppe and garigue

It is considered that the successful spread relies on soil mixing. In the examples above, soil mixing could not take place, but the plant is abundant / present there too. Who would have placed 'bulbil - infected' soil in those soil pockets in garigues or wall gaps in high fortifications where Oxalis is found.

3) Is there Oxalis pes-caprae in Filfla, St. Paul's island and Cominotto where soil mixing is unlikely to have taken place?

All this story makes me think that we are missing some link or fact. In my imagination, I cannot figure out that the plant have invaded the islands by only bulbil to bulbil propagation through soil.


MY list of alternative hypothesis:
-----------------------------------------
A) In the past the plant used to make planty of seeds (maybe berries carried by birds) but now it lost this function.

B) It might have been introduced much before (eg by Arabs) in garigues or unknown places by contaminated soil from Arab land.

C) There was a long period where the plant was cheaply sold as an ornament with plenty of people planting it in their gardens or fields. The plant would have had a cost effective market becasuse:

- Probably cheap,
- Nice bright flowers spanning over 4 months (Jan-Apr)
- Flowers are scented
- Long flower stalk makes it ideal for a cut flower
- Little care needed,
- At that times was a new flower (so interesting)



I hope I have created an interesting article, and your comments / opinions / envisage / opinions are welcomed.
Last edited by MWP admin on Tue Jan 03, 2006 8:08 am, edited 2 times in total.
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Post by IL-PINE » Mon Dec 19, 2005 12:27 am

I think that the bulbils are very light and easily get dispersed by wind and will germinate in any condition available - even steppes and the limits of sand dunes.

There are no parasites of this species that can limit the spread of the species - the endemic Broomrape who was a parasite on other plants has switched on this species for example.

The plant might spread via roots or any other segment of the plant!

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Post by jackpot » Mon Dec 19, 2005 10:44 am

Pine: you are right with the bulbils, dispersed by wind and water! We studied the subterranean part of O. p-c. 2 years ago (unpublished). There is a contractile root, which is responsible for separating very small bulbils etc. Also, they get dispersed by cutting or digging out the plant. I remember many times that people hang the plants over the walls of their agricultural sites, I don not know why... (just for removing or drying for fodder?). It should be prohibited to do so, because this results and a much stronger invasion.
Orobanche ramosa/melitensis kills the plant very fast (but unfortunately not the bulbils).

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Post by IL-PINE » Wed Dec 21, 2005 10:59 pm

An incredible plant. We just need a large number of Orobanche to kill the Oxalis off! :x

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Post by wolf » Mon Dec 26, 2005 9:35 pm

I notice however that a couple of garigues are free of oxalis and also a few patches of garigue here and there are free .....for example at dingli near maddalena chapel oxalis usually stays by the road verge and is not present near cliff edge ( which is slightly higher ground....so the pine theory seems to be working here

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Post by MWP admin » Thu Dec 29, 2005 8:39 am

I think the distribution by wind makes a bit of sense when I see Oxalis in small rock gaps. It has also been reported in some references (ref link). How else they could have ended there if not by aerial drop (= wind / birds)?! On the other hand I am sceptical about this theory becasue nutlets or bulbils form rather strong well anchored roots and so how would they get free from soil and so carried away?? I am not saying it is impossible, but that it is not the main factor of the huge dispersal of Oxalis pes-caprae.

I notice however that a couple of garigues are free of oxalis and also a few patches of garigue here and there are free .....for example at dingli near maddalena chapel oxalis usually stays by the road verge and is not present near cliff edge ( which is slightly higher ground....so the pine theory seems to be working here
When I see a patch free from Oxalis, sometimes I do not consider much the wind theory, because how would you explain that this open patch was not reached by wind?!! Strange indeed.



I think that a combination of events have lead to the wide distribution of Bermuda buttercup in these 2 centuries.
Some theories and hypothesis are:

1) Wind dispersal of bulbils which are quite light. (reported)
2) Distribution by water after heavy rains - bulbils float. (reported)
3) Fast spreading nature of the plant. (reported)
4) Perfect adaptability to our climate and soi.l (reported)
5) Not eaten by most grazing animals. (reported)
6) Mixing of soil and land from one place to another - a quite important factor in a small island like Malta. (reported)
7) Distribution as ornament in early times. (hypothesis)
8 ) Formation of seeds in the past. (hypothesis)



I would like to ask the experts:

1) If is it possible that the plant form seeds in certain climatic/environmental conditions? (I would like to believe in this hypothesis too - it would explain it all! )

2) Is there Oxalis pes-capres in Filfla?

3) How invasive it is in neighbour islands like Sicily, Sardegna, Corsica, Cyprus etc - is it as bad as in Malta?

4) If a plant forms an average of 15-20 bulblets per year (ref link), and we started say from 20 escaped plants, would mathematically in 200 years arrive to this millions or billions or ... (I cannot estimate) of plants as found on our islands?
Last edited by MWP admin on Tue Jan 03, 2006 8:13 am, edited 8 times in total.
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Publish me

Post by MWP admin » Thu Dec 29, 2005 9:21 am

We studied the subterranean part of O. p-c. 2 years ago (unpublished)
Jackpot, would we ever see this study published. It would be very interesting. You are of course more than welcomed if you want to do so via this website (all copyrights reserved of course).

Either send me the doc or a link to a server and citation of the refernces.
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Seeding could be possible

Post by MWP admin » Thu Dec 29, 2005 10:10 am

Look what I have found...

http://www.bihrmann.com/caudiciforms/su ... es-sub.asp

"WARNING: This plant will spread fast, thanks to it's exploding seed-capsules. " (refering to oxalis pes-caprae).


- - - - - - - - - - -


http://www.plantzafrica.com/plantnop/oxalis.htm

"The ovary is superior, 5-locular with five free styles. The fruit of Oxalis is a 5-lobed capsule, much longer than broad, with nearly parallel sides. The seeds, one to many, are explosively ejected." (Refering to the Oxalis Genus)
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Post by MWP admin » Thu Dec 29, 2005 10:31 am

jackpot wrote:I remember many times that people hang the plants over the walls of their agricultural sites, I don not know why... (just for removing or drying for fodder?).
I do not think so, because it is reported that Oxalis pes-caprae casue livestock intoxication due to oxalate posioning. Maybe the farmers have a way to render the poison harmles for example by drying?? - I doubt it though.
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Seeds or not!?!

Post by MWP admin » Thu Jan 19, 2006 12:39 pm

I have been in touch with a friend whose friend goes to Filfla for research purposes several times. She confirms the presence of Oxalis pes-caprae on this small islet, about 4km away from mainland Malta.

So what are your explanation of the presence of this plant on this islet???

As far as I know:


No farmers,
No agriculture,
No people would take the burden to go by their small boats to Filfla and dump their soil = no soil mixing
Wind cannot carry bulblets that far
I dont think they were carried away by sea water


My hypothesis is always that at a certain time the plant was able to form seeds and these where carried by birds and dropped via their faeces. Maybe nature contols itself and switched off the seed-forming gene of the plant when 'it' saw its huge and terrible invasiveness!
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Post by IL-PINE » Sun Jan 29, 2006 11:51 am

I was reading in the books that we have another 2 species of Oxalis in Malta. One has also yellow flowers and is smaller than the Oxalis pes-caprae. Besides, it produces seeds. So are we dealing with just one or 2 species of Oxalis in our islands? The invasiveness could also explain this.

Boq!

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Post by robcar » Sun Jan 29, 2006 5:41 pm

The oxalis with smaller yellow flowers must be O.corniculata. The photo attached below was taken in May in Balzan.
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Oxalis corniculata (creeping woodsorrel) Balzan.JPG
Oxalis corniculata (creeping woodsorrel) Balzan.JPG (88.46 KiB) Viewed 62594 times

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Post by MWP admin » Sun Jan 29, 2006 5:43 pm

Your comment came in time with my incident of meeting a strange Oxalis pes-caprae as shown here. I will submit a specified post in the identification post as I do not know if it is a defect/hybrid of Oxalis pes-caprae or a new species.

Dont forget that the O. pes-caprae pleniflora is a variant of O. p-c. not a new species.
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SmallOxalis_pc.jpg
Small flowered version of Oxalis pes caprae
SmallOxalis_pc.jpg (96.68 KiB) Viewed 62593 times
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Post by greenhorn » Thu Feb 02, 2006 1:41 pm

Yesterday I found in a book about Greek Flora, that this plant came
via Malta!!! from South Africa to the Greek Islands.
And one of our neighbours dries it and uses it together with straw
for the sheep and his goat. He says, it is good against parasites.

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Post by MWP admin » Thu Feb 02, 2006 6:02 pm

Yes its true, not only greece but whole Mediterranean part of Europe, include some islands in the atlantic oceans. And from Malta it all strarted from a couple of plants exactly 200yrs ago.

You can reed more info on this link:

Oxalis pes-caprae
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Post by RB » Wed Nov 08, 2006 6:15 pm

Kumbinazzjoni I was just thinking about Oxalis. I have some seedlings in pots, it does look likely to be contaminated compost, and the seedlings look rather reddish so likely not pes-caprae.

Honestly I don't give them much of a chance though :twisted:

Also in some pots of plants I bought, there is also some oxalis sp growing, not pes-caprae. Easy ticket in, ehhh?

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Post by MWP admin » Wed Nov 08, 2006 6:19 pm

It can be Oxalis corniculata or Oxalis fontana, both species in Malta. The latter is featured in my website!
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