Tuberous Utricularia dichotoma flowering

[gardenofeden]

Remember this?

string by gardenofeden67, on Flickr

Tuber string from Utricularia dichotoma, Jamieson, Victoria.

Well it's flowering now for the first time.

dichotoma tuberous 14 by gardenofeden67, on Flickr

dichotoma tuberous 12 by gardenofeden67, on Flickr

Anyone know if it likes a dry dormancy, I'm not quite sure, manage to keep it alive but not convinced it's happy...

[LJ]

Cant help with the answer but just wanted to say great picture - must have missed the string of tubers the first time round - very interesting!

[Nigel H-C]

Hi Stephen,

I'd say keep it on the dry side as one assumes that's why they're produced. Kept mine wet just in case and lost it!

Nigel HC

[Dieter]

Hi Stephen,

congratulations! I am unfortunately one of those who did not manage to keep this interesting plants alive for more than a year.

Best regards

Dieter

[Sean Spence]

Glad to hear that it is still going strong. I have only a single pot remaining with a very small plant.

When the plant was growing well for me I found it essential to create new cultures regularly to keep the plant fresh and vigorous. If I didn't do this, the plants would dwindle quickly and die off.

I managed to keep it alive after a completely dry dormancy but found it responded better when kept moist.

It is a very difficult form to grow and the fact you've still got it going is a great effort.

[Fernando Rivadavia]

Wow, that tuber string is amazing! I wonder what evolutionary pressure would favor such a structure over simply one long fat root...

Thanks!

Fernando

[Tim Caldwell]

Wow, that tuber string is amazing! I wonder what evolutionary pressure would favor such a structure over simply one long fat root...

Good question. Maybe it's about making sure that more than one stolon is produced, so that the tuber isn't "putting all its eggs in one basket". My two (NON-tuberous) dichotomas have most of their leaves around the edges of the pot, which I'm hoping is just because U. dichotoma's stolons don't branch very often, so they probably just end up circling the pot. But if a tuberous plant only produced a single stolon with a single growing tip, having it damaged might be a really serious setback.

I'm amazed that any single Utricularia species can have such enormous variation as having tuberous and non-tuberous forms, while still apparently retaining all the other distinguishing characteristics of the species. I can't really imagine it happening with, say, drosera.

Cheers,

Tim

[Fernando Rivadavia]

Hello Tim,

Good question. Maybe it's about making sure that more than one stolon is produced, so that the tuber isn't "putting all its eggs in one basket". My two (NON-tuberous) dichotomas have most of their leaves around the edges of the pot, which I'm hoping is just because U. dichotoma's stolons don't branch very often, so they probably just end up circling the pot. But if a tuberous plant only produced a single stolon with a single growing tip, having it damaged might be a really serious setback.

I agree it possibly has something to do with not putting all its eggs in the same basket. In case the stolon is broken, maybe each one of those segments could sprout a new plant. But why put them so close together like that (reminds me of sausages!)? Why not spread them out more? If any damage occurs to the plant, it would probably be better off having those tubers spread out (thus not putting all the "eggs" so close together, where they could all be damaged at once).

This seems to suggest to me that the tuber strings are not produced as a safety measure to recover from damage. Maybe they're a way of spreading asexually after some annual event?

In the habitats where these tuberous U.dichotoma grow, does the soil dry up completely? Do the plants actually go dormant? Is there possibly something (rain or animals) which churn the soil up every year?

I'm amazed that any single Utricularia species can have such enormous variation as having tuberous and non-tuberous forms, while still apparently retaining all the other distinguishing characteristics of the species. I can't really imagine it happening with, say, drosera.

It could be that the common ancestor of all U.dichotoma lived in drier conditions and had tubers, but in most populations the genes for this have now been switched off because maybe they are not necessary anymore (and thus only a few populations are still expressing these genes).

Anyway, what this means is that we still have a lot to learn from U.dichotoma ecology, phylogeny, genetics, etc.! :)

Best wishes,

Fernando

Edited September 9, 2010 by Fernando Rivadavia

[Tim Caldwell]

Hi Fernando,

It could be that the common ancestor of all U.dichotoma lived in drier conditions and had tubers, but in most populations the genes for this have now been switched off because maybe they are not necessary anymore (and thus only a few populations are still expressing these genes).

Yes, good point, it would certainly be far easier for populations to lose a redundant ancestral trait than it would be for any local population to develop a completely new trait, in enough isolation from other populations for it to be possible, and in quick enough time for it to not end up evolving into a completely new species.

This seems to suggest to me that the tuber strings are not produced as a safety measure to recover from damage. Maybe they're a way of spreading asexually after some annual event?

I meant that when the tubers sprout again in better conditions and need to establish themselves quickly, it might be better to start with more than one growing tip than just a single vulnerable one from a single large tuber. I suppose the asexual reproduction thing is possible, but it seems to me that most Utricularia are constantly reproducing asexually in much the same way anyway since they produce branching stolons, and when the older parts of the plant die all the growing tips that developed from the dead part effectively become separate plants. It's easiest to observe with the aquatic species, but presumably occurs in most terrestrial ones as well. So the most important question for us to ask is what kind of regular catastrophe the tubers are there to protect against.

In the habitats where these tuberous U.dichotoma grow, does the soil dry up completely? Do the plants actually go dormant? Is there possibly something (rain or animals) which churn the soil up every year?

I don't know what conditions the tuberous dichotomas grow in (or for that matter whether they're restricted to a single geographical area). But in this part of the world almost all herbs are tuberous or annual, because our summers are not only very warm to hot, but also very dry. So I would think that the tuberous populations live in wetland areas that dry up over summer, although there might be other contributing factors.

I don't get out on field trips much (I know you do!), but one of the few times I've come across U. dichotoma growing in the wild I just found a single flower growing out of a drying puddle. I have no idea how it got there, and since it probably wasn't tuberous it certainly wasn't going to be there for very long! But if 'normal' U. dichotomas can grow in those conditions, it raises the question of why most populations didn't retain the ancestral tubers, which might score a point for the 'innovation' theory over the 'inheritance' one. But since that poor little plant in the drying puddle would've benefited from having a tuber, there might be something in your suggestion that the tubers are about more than just surviving drought. Alternatively, maybe the tuberous forms have just 'recently' stumbled onto a fantastic innovation that might one day end up being shared with the rest of the populations of the species.

Anyway, what this means is that we still have a lot to learn from U.dichotoma ecology, phylogeny, genetics, etc.! :)

Yep, the more we think about the questions, the more confused we get. But I think U. dichotoma and its closest relatives are particularly interesting. As I understand it, they diverged from other sections of the genus fairly early on in Utricularia evolution, and so probably have a very different suite of inherited and innovated characteristics to the species in most other sections of the genus. And U. dichotoma in particular seems to have a surprising amount of variation.

On the two forms that I have the stolons follow an incredibly simple and regular pattern: at regular intervals along each stolon are nodes, each of which produce a single leaf as well as a pair of traps angled diagonally upwards, and a pair of anchor stolons angled diagonally downwards (so it looks a bit like a five pointed star). So the specific name 'dichotoma' doesn't seem to just apply to the flowers. But I've read that there are forms that also produce special trap-bearing stolons as well. The traps are also surprisingly variable and seem to come in quite a variety of different forms. Definitely one of my favourite species, not least because the traps are so big!

Cheers,

Tim

Edited September 10, 2010 by Tim Caldwell

[Sean Spence]

Thought I'd post some photos of the natural habitat of this form as well as a few images of different flower colours and forms found at the same location. These were all posted here back in 2004 when I first discovered this form.

The habitat is wet throughout winter as it is located at the base of a man made dam on the side of a road. Water seeps downhill from the dam, across the road towards a small waterhole. When the heat of summer arrives, the seep and waterhole dry up completely. Plants can only be found from October to mid-December as the weather is too cold in winter (frequent frosts and often snow) and too hot in summer (stretches of close to 40+ deg C for weeks at a time).

A deep purple population occurs on the dam side of the road in a ditch. On the other side of the road beside the waterhole, the population is incredibly variable in flower colour, ranging from deep purple, blue, white, lilac, pink, etc. These flowers are larger than most others forms and often produce very wide lower corollas, some approaching 200+ degrees rather than the more common ~90 degrees (most obvious in the deep purple form). The upper corollas of these wider skirted forms are proportionate in size and angle to the lower corollas. Some palettes are yellow, others white and the number of palette ridges is very variable. It is common for most inflorescences to have 4-5 flowers per scape.

Interestingly, the leaves are quite different to any other forms I've seen (that's lots). They are pale green, very large and almost succulent.

A couple of larger flowered well coloured forms. Note the extra palette ridges and number of flowers. These grow near the natural waterhole.

A deep purple flowered form. Shorter than the others but the flower have an incredibly wide upper and lower corolla. The palette is white. All of the plants in the roadside population look like this.

A lilac coloured form from the waterhole.

and a pink one, also from the waterhole.

A shot of the large leaves from the upper area adjacent to the waterhole. These grew in the constantly flowing water of the seep. You can see that D. peltata var. peltata grows with it. The substrate here is sticky clay.

[Sean Spence]

Roadside below dam.

This area gets mowed each year- luckily just before the main flowering.

Other side of the road. A small natural waterhole. The U. dichotoma population here occupies are area about 10 metres long by 5 metres wide.

[MFS]

Sean,

Thanks for the pictures, they're great!

What really surprises me is how uniform U. dichotoma is in Tasmania, compared to just across the ditch. Down here most flowers have the colour and shape of this one:

Though I have seen populations in the northeast with larger flowers and several per scape, like the ones you show. I'll endeavour to photograph them this summer.

[Fernando Rivadavia]

Hey Tim,

I meant that when the tubers sprout again in better conditions and need to establish themselves quickly, it might be better to start with more than one growing tip than just a single vulnerable one from a single large tuber. I suppose the asexual reproduction thing is possible, but it seems to me that most Utricularia are constantly reproducing asexually in much the same way anyway since they produce branching stolons, and when the older parts of the plant die all the growing tips that developed from the dead part effectively become separate plants. It's easiest to observe with the aquatic species, but presumably occurs in most terrestrial ones as well. So the most important question for us to ask is what kind of regular catastrophe the tubers are there to protect against.

Exactly! This string of sausages suggests to me that it does expect some sort of regular (annual?) disaster (drought or some physical disturbance?) which will force it to regrow asexually from these little tubers. And I guess you're right about having multiple growing points once it does have to grow back (more likely to make it than one single large tuber).

I don't get out on field trips much (I know you do!), but one of the few times I've come across U. dichotoma growing in the wild I just found a single flower growing out of a drying puddle. I have no idea how it got there, and since it probably wasn't tuberous it certainly wasn't going to be there for very long! But if 'normal' U. dichotomas can grow in those conditions, it raises the question of why most populations didn't retain the ancestral tubers, which might score a point for the 'innovation' theory over the 'inheritance' one. But since that poor little plant in the drying puddle would've benefited from having a tuber, there might be something in your suggestion that the tubers are about more than just surviving drought. Alternatively, maybe the tuberous forms have just 'recently' stumbled onto a fantastic innovation that might one day end up being shared with the rest of the populations of the species.

I'd say it's more likely that the tuber is ancestral and your plant in the dry puddle is possibly an annual form (or annual wanna-be). Evolving towards an annual growth form would involve shedding tubers for one.

Yep, the more we think about the questions, the more confused we get. But I think U. dichotoma and its closest relatives are particularly interesting. As I understand it, they diverged from other sections of the genus fairly early on in Utricularia evolution, and so probably have a very different suite of inherited and innovated characteristics to the species in most other sections of the genus. And U. dichotoma in particular seems to have a surprising amount of variation.

Although U.dichotoma belongs to a basal lineage of Utricularia, that doesn't make it an old species. To me it actually looks more like a very recent branch sprouting off the base of the tree, a species that recently evolved and is very successful!

On the two forms that I have the stolons follow an incredibly simple and regular pattern: at regular intervals along each stolon are nodes, each of which produce a single leaf as well as a pair of traps angled diagonally upwards, and a pair of anchor stolons angled diagonally downwards (so it looks a bit like a five pointed star). So the specific name 'dichotoma' doesn't seem to just apply to the flowers. But I've read that there are forms that also produce special trap-bearing stolons as well. The traps are also surprisingly variable and seem to come in quite a variety of different forms. Definitely one of my favourite species, not least because the traps are so big!

Wow, fascinating, I wasn't aware of all this!

Thanks!

Fernando

[Fernando Rivadavia]

Hello Sean,

Thanks for the beautiful pics and great info!

These were all posted here back in 2004 when I first discovered this form.

Could you give us thel link?

The habitat is wet throughout winter as it is located at the base of a man made dam on the side of a road. Water seeps downhill from the dam, across the road towards a small waterhole. When the heat of summer arrives, the seep and waterhole dry up completely. Plants can only be found from October to mid-December as the weather is too cold in winter (frequent frosts and often snow) and too hot in summer (stretches of close to 40+ deg C for weeks at a time).

Aha! Here we see some possible clues for the tuber formation... Ice & snow, huh? Could these tubers be made to survive in frozen soil then? Could numerous freeze-thaw events be responsible maybe even for breaking up the tubers from each other? Or maybe its the combination of bone-dry summer AND frozen winters that demand this tuberous growth form of survival?

Interestingly, the leaves are quite different to any other forms I've seen (that's lots). They are pale green, very large and almost succulent.

This sounds very interesting too!

So much to learn...

Thanks,

Fernando

[Tim Caldwell]

Hi Sean, Fernando, Miguel,

Plants can only be found from October to mid-December as the weather is too cold in winter (frequent frosts and often snow) and too hot in summer (stretches of close to 40+ deg C for weeks at a time).

The very short growing season might be a clue as to why this form became/remained tuberous, since with so little time to get established the plants would want to save as much of their energy as possible for an efficient start the following year. Bushfire might also be a factor as well. Jamieson is right in the area where the particularly bad bushfires were last year, actually very close to the town of Marysville which was pretty much destroyed.

Sean, just out of curiosity how many U. dichotoma forms do you grow? I just have a Beenak one from you, and one from the east coast of Tassie that Spot sent me. The Tasmanian one has slightly larger traps than the Victorian one - the largest are about 4mm. Not bad for a terrestrial utric I reckon! The traps are also noticeably different in shape on each of the two forms.

The Beenak one produced a scape once but unfortunately it aborted, so I've yet to see either of my plants flower and I'm looking forward to making the comparison!

Cheers,

Tim

Edited September 11, 2010 by Tim Caldwell

[Sean Spence]

We have plenty of populations here with flowers almost identical to your image Miguel.

Though I have seen populations in the northeast with larger flowers and several per scape, like the ones you show. I'll endeavour to photograph them this summer.

You'll need to check the underground parts this time round too.

Jamieson is right in the area where the particularly bad bushfires were last year, actually very close to the town of Marysville which was pretty much destroyed.

The environment is actually quite different, but bushfires are still always a danger. Hasn't been one there for many years though. The alpine fires of a few years back were much closer than those from Marysville.

Sean, just out of curiosity how many U. dichotoma forms do you grow?

Not quite as many as I once did but still quite a few. Not sure of the exact number without doing a thorough stocktake. Probably about 15-20.

Since we are discussing U. dichotoma, I thought I'd add a few images of other local forms- including the Beenak one you missed out on Tim.

The Beenak/Tonimbuk form.

Langwarrin.

Cranbourne purple palette.

Lowland Grampians form.

An albino version.

The aff. montane form.

[Sean Spence]

For comparison. Not U. dichotoma but very closely related, U. beaugleholei.

[Binataboy]

I think the U dichotoma's in Victoria are currently undergoing mass speciation. There are a lot of variations and simmilarities in the U. dichotoma in SE Australia. The Jamieson plants have very simmilar fleshy "leaves" to a plant a friend found growing at Cheshunt, which is about 60km as the crow flies from Jamieson. Cheshunt also experiences snow and the plant was found growing as an aquatic in a spagnum bog. I have not had it form a tuber, or flower (I have distributed a fair amount of this plant over the years, has anyone had it flower?)... Where the alpine dichotoma I found (aprox 1800m alt.) looked like a typical plant only redder in the leaves.

As for aquatics, I had a form of dichotoma from Enfield, Vic. which grows well as an aquatic, and flowers as a suspended aquatic in deep water. Its aquatic leaves are very long and thin, up to 5cm, where the Cheshunt leaves remain rounded and fleshy.

Sean is the Beenak dichot flower typical of your plant as in the wild they usualy had 5 ridges? (three main and 2 small side ridges)

These are some of the original plants I collected many years ago so sorry for the poor pic...

I am sure there are a lot more secrets in this species complex.

Cheers

George

[Fernando Rivadavia]

Hey guys,

The very short growing season might be a clue as to why this form became/remained tuberous, since with so little time to get established the plants would want to save as much of their energy as possible for an efficient start the following year. Bushfire might also be a factor as well. Jamieson is right in the area where the particularly bad bushfires were last year, actually very close to the town of Marysville which was pretty much destroyed.

In order to better understand the evolutionary reason for these tubers, I guess we'd have to find out when exactly they are formed in the wild (and in cultivation). Are they present year round or only part of the year? Are they formed every year, or only after rare events like fires?

Thanks for all the cool pics!

Fernando

[Tim Caldwell]

Hi guys,

Thanks for those pics Sean, it's great to compare some different types. Most of the wild plants I've seen are at Langwarrin, so for me that form is kind of a frame of reference. I actually quite like the Beenak one with it's wide and nicely shaped lower corolla.

The comparison with U. beaugleholei is interesting. U. dichotoma's flowers are so variable that U. beaugleholei just looks like one of the more extreme variants, and for me as a layman it's tempting to demand that botanists divide U. dichotoma up into more species or subspecies. But with so much variability even within individual small populations it might be difficult to assign meaningful, stable, subcategories. But I am curious to know exactly what the criteria were that made U. monanthos and U. beaugleholei so special that they be given specific status. U. monanthos has flowers that seem like pretty run of the mill dichotoma flowers except for their short scapes, and I suspect that stability of form over a wide area might be the key to why they're recognised as separate species. With U. dichotoma, labelling them by location as you do, eg. 'Beenak form', might be the best that can be done.

Probably about 15-20.

That's not a bad selection! How much variation do you see in the arrangement of stolons, and size and form of the traps?

Are they formed every year, or only after rare events like fires?

Fernando

One point about bushfires is that I would think tubers that are formed beneath the surface would be much better insulated from fire than seed that's scattered close to the surface. So that might be a contributing factor to why this form uses tubers rather than employing some other strategy. But the short growing season seems likely to be the main stress factor.

As for aquatics, I had a form of dichotoma from Enfield, Vic. which grows well as an aquatic, and flowers as a suspended aquatic in deep water. Its aquatic leaves are very long and thin, up to 5cm, where the Cheshunt leaves remain rounded and fleshy.

That's an interesting point. Tasmanians in the group have posted interesting photos of wild plants that border on being aquatic.

U. dichotoma's traps are really pushing the limits of how big the traps of a terrestrial utric can get. And it's also a species that seems to benefit more than most from growing completely submerged in cultivation. Even the way the stolons only branch rarely seems more akin to the aquatic species, and these features might point to it having evolved in a particularly wet environment.

Cheers,

Tim

[moof]

Great photos and interesting photos everyone, I've got about 6 dichotoma forms (some are mislabelled so not sure which plant is from which location:( ) including the one from Jamieson and Enfield, Vic but never got these locations to flower. They grows fine though, and I keep them constantly wet, sand-based soil medium. I'll try to grow them as submerged ones. And I agree this species have got really big traps sometimes when compared to other terrestrial ones!