Tasmanian Plants

The Myrtle Beech (Nothofagus cunninghamii) is one of Tasmania’s icon trees, and is the dominant component of  Tasmania’s cool temperate rainforest. Where these dendrons attain their finest stature in some parts of Tasmania’s verdant Northwest and Northeast, they assemble grand cathedral or callidendrous (meaning ‘beautiful tree’) rainforests, which has for generations captured the imagination and awe of Tasmanians.

Back 18,000 years ago, when glaciations in Tasmania were at their maximum (called the Last Glacial Maximum and henceforth abbreviated LGM), practically the whole of the island would have been unsuitable for the development of cool temperate rainforest, except in pockets of areas in the west. Such areas where plants survived during glacial periods are called refugia.

In the present day, the Northeastern part of Tasmania has sizeable patches of Myrtle Beech rainforest. Yet, geomorphological and pollen-based data suggests that the entire Northeastern area was too arid during the LGM to support rainforest. The question thus arises whether Myrtle Beech trees had survived there in refugia during the LGM or whether they were dispersed from refugia from the west after the LGM?

The immediate problem with the latter suggestion is that Myrtle Beech seeds disperse poorly over long distances, making it unlikely for seed to cross over 150 km from western refugia.

Tackling this conundrum was the topic of Dr James Worth’s honours research and part of his doctorate studies. The efforts of James and his fellow investigators have culminated in a recent publication in the scientific journal New Phytologist.

From his extensive fieldwork, James collected Myrtle Beech leaves from over 340 trees across the distributional range of the species, which includes both Tasmania and Victoria. Using molecular techniques, James then extracted the chloroplast DNA from these individuals and compared their DNA sequences.

James discovered that a common signature in the DNA (a chloroplast DNA sequence that is called a haplotype) that exists for Myrtle Beech trees in Victoria and in numerous areas of Tasmania. The western part of Tasmania however, had an additional and significantly large suite of other endemic haplotypes, suggesting a complex evolutionary history of Myrtle Beeches in that area, and perhaps survival in numerous refugia, which is within expectations.

Myrtle Beech haplotype distribution. White circles and black circles represent the widespread and endemic western haplotypes in the left and right map respectively. Red circles represent the unique Northeastern haplotypes. MA = Mt Arthur; MB = Mt Barrow; BL = Ben Lomond; MM = Mt Maurice; MV = Mt Victoria; BT = Blue Tiers

In the Northeast, trees from two regions bore the common haplotypes, some in the western extreme (Mt Barrow), and some in the eastern extreme (Blue Tiers). In between was a central region (areas in the vicinity of Mt Victoria, Mt Arthur and Mt Maurice) in which a unique haplotype was discovered.

At least for this central region, the presence of the unique haplotype is strong evidence that there must have been refugia for the Myrtle Beech in that area.

James concluded that the Myrtle Beech withstood the aridity of the last glacial period within multiple regions in apparently inhospitable climates.

Whether cathedral rainforest actually existed in refugia in the Northeast during those times is questionable but if the conditions then were simply untenable for rainforest, Myrtle Beech trees could still have survived, being, as we are currently able to observe, able to occur as a compact shrub in harsh highland environments.

This is where the true virtues of the Myrtle Beech comes to light. If Myrtle Beech did not survive through the last glacial, there would be no rainforest to speak of. Yet, Myrtle Beech did more than just survive through the LGM. Fossils suggests that it has been around for at least 780000 years. Myrtle Beeches have therefore survived through numerous cycles of glaciation.

The resilience of this iconic temperate tree throughout the ages has unquestionably shaped Tasmania’s modern biota.

The clear and bright morning of the 7th of October 2009 was to set the tone for the weather of the day. It was going to be a perfect day for an outing to the Tasman Peninsula to look for threatened plants, an emphasis being placed an endangered eyebright, the Peninsula Eyebright (Euphrasia semipicta).

Along with 10 other volunteers, I had the pleasure of joining Dr Wendy Potts of the Department of Primary Industries and Water, our local expert on Tasmanian eyebrights, in a hunt for the endangered plant.

The Peninsula Eyebright is a short-lived endemic perennial which has been listed as endangered under the Tasmanian Species Protection Act (see Notesheet from the DPIW website). As the common name suggests, the Peninsula Eyebright is found only on the Tasman Peninsula. There it grows on a wide variety of substrates ranging from clayey to sandy soils.

It’s rarity and unique distribution asides, the Peninsula Eyebright has an interesting natural history that may not immediately be apparent to the casual observer.

For many years, Eyebrights were part of the Figwort family (Scrophulariaceae), to which well known medicinal plants like figworts (Scrophularia) and mulleins (Verbascum) belong. The placement of Eyebrights in the Figwort family however, proved to be untenable on the basis of DNA evidence (Young et al. 1999). In fact, the entire figwort family has lost many of it’s members since the advent of molecular science.

Also because Eyebrights are semi-parasitic – a feature not typical of the Figwort family. Ultimately, Eyebrights were placed under the broomrape family (Orobanchaceae), which have members that are typically semi-parasitic to wholly parasitic. What the Peninsula Eyebright parasitizes on is still anyone’s guess, a reflection of what remains to be discovered.

The Peninsula Eyebright, like some other rare native eyebrights, is quite peculiar with respects to where it lives. In almost every site we visited, we found plants growing near tracks or roads. Wendy says that they ‘like the view’.  Being semi-parasitic seems to be tied in with their transpiration rate, and hence the need of exposure to drive that transpiration rate. ‘They can die within two days of being kept in a dim area’, says Wendy.

Also, being an endemic component of Tasmania’s flora, the Peninsula Eyebright must have evolved alongside the pyrogenic rhythms of the Tasmanian landscape. It is conceivable that before European settlement, the Peninsula must have relied heavily on aboriginal burning for survival. Arguably, the Peninsula may have been more common before the changed fire regimes brought about by European colonialism.

Complex evolutionary processes are at work in the East Coast of Tasmania, and their effects are very marked in the eyebrights. This creates a headache for taxonomists as the species concept is stretched really thin by some of these eyebrights. Just within the Peninsula Eyebrights, Wendy has found and described plants of three different forms that vary in corolla colour and other morphological details (Potts 1997), but as yet, no one has taken any steps to formally distinguish these forms as separate subspecies.

We saw two of the forms that Wendy described. One had purplish flowers with striations in the corolla. The other had the same type of striations but with white corollas, and tended to be more squat than the former.

In all the localities we visited, the Peninsula Eyebrights appeared to be doing better than the year before, when I had visited the same localities with Wendy. Perhaps it was the good rainfall we got this winter and early spring. We even discovered plants from a couple of new spots.

When I contemplate the Peninsula Eyebright, I cannot help but marvel at how nature sometimes graces certain small geographical areas with an expression of plants and animals that are found nowhere else. When, perhaps, in the distant future, natural processes separate the Tasman Peninsula from Tasmania, the Peninsula Eyebright will no doubt be a prime candidate as the icon plant of the ‘Tasman Island’.

When it comes to the sexual behavior of Tasmanian bryophytes, there are no lack of interesting species with juicy stories. One such moss is Rhacocarpus purpurascens.

This is a moss that typically grows on rocks in alpine regions and can frequently be seen submerged in alpine tarns. I never fail to look out for it everytime I visit such areas.

Oddly however, R. purpurascens it also occurs on large boulders at much lower altitudes near to sea level (see my previous post on my Cataract Gorge visit). Not a great deal of native plants can claim to have such a wide ecological range.

R. purpurascens is a very distinctive moss once known. The leaves have very fine hairpoint tips are arranged spirally around the stem in a very regular and neat fashion, conferring to the shoots a beautiful braided effect. Also, the brighter hues of the new shoot growth often contrasts beautifully with the older and darker parts of the plant.

I dedicate this post to R. purpurascens because this is the first time I am seeing it in fruit.

Since 2006 I have been looking out for capsules on this moss, particularly everytime I got to visit alpine areas. Interestingly, Paddy Dalton, a leading bryophyte specialist in Tasmania, has never seen R. purpurascens capsules up in the alpine areas in all his years of bryologizing. Oddly, he has observed it fruiting in Cataract Gorge, a lowland area. Paddy has written about this in the 35th Volume of the Bryological Newletter.

The elegant capsules are vase shaped and borne on a fine stalk (in bryological terms refered to as a seta).

I found fruiting R. purpurascens in the most unexpected of places – at Knocklofty Reserve. It was growing off a chunk frequently soaked exposed dolerite on the top of a cliff face.

Not only was it fruiting, there were dried capsules indicating that it must have been fruiting in at least the year prior as well.

My conclusions about this interesting disparity in fruiting behavior mirrors what Paddy wrote in his article, that phenological (study of flowering/fruiting behavior) investigations will be necessary to find out what is going on with the populations up the mountains.

Perhaps what we are seeing is a very versatile moss that chooses procreation when the conditions serves it but opts for celibacy instead under the harsher, colder environments on the tops of mountains. In the latter case, it has somehow managed to reproduce itself asexually and has been very successful at doing so.

Whether sexual or celibate, alpine or lowland dweling, R purpurascens has been hugely successful.

Mitrasacme pilosa var. pilosa (Hairy Mitrewort). Peter Murrell Nature Reserve.

Mitreworts refer to a group of plants of the genus Mitella from the Saxifrage family (see wiki article). These are temperate and arctic North America and Asian plants which, as far as I know, do not occur in Tasmania.

However, the practice of assigning the same common names to plants that are totally not related to one another has been going on for a long time.

It is therefore of little surprise that we find in Tasmania a number of plants called mitreworts as well. These are small herbs which hail from the Loganiaceae, the botanical family that houses the infamous Strychnine tree.

M. pilosa var. pilosa (Hairy Mitrewort). Closeup. Peter Murrell Nature Reserve.

This post is about a small herb known as the Hairy Mitrewort (Mitrasacme pilosa), a widespread species which often occurs in sandy heaths.

Whilst rambling around Peter Murrell Nature Reserve I stumbled on a small patch of what I believe is this plant near a ditch full of exotic grasses.

The plant was an attractive, neatly compact and prostrate herb. It had hairy stems with opposite leaves. In particular, the calyces were extremely hairy. The Hairy Mitrewort came to mind.

I had previously seen the Hairy Mitrewort before in a sandy heath on the Tasman Peninsula but after dredging up the photo I found that the two plants looked rather different.

M. pilosa var. stuartii (Stalked Hairy Mitrewort). Tasman Peninsula.

The one I found at Peter Murrell was compact, had very short pedicels (flower stalks) and extremely hairy calyces whereas the one I saw at the Tasman Peninsular was a less compact herb and slightly erect, had a very long flower stalk, and a close to hairless calyx.

Going back to the Student’s Flora of Tasmania, I found a description of the plant in Part 3 of the flora where Curtis writes:

‘The variants of with flowers borne on long pedicels have been distinguished as var. stuartii. Extreme forms, i.e. those with almost sessile flowers (flowers born on a very short stalk) and those with flowers on pedicels c. 3 cm long are very distinctive.’

This being said, it is probably safe for me to conclude that the Tasman Peninsula specimen belongs to var. stuartii and that the Peter Murrell specimen belongs to var. pilosa, which is the only other variety present in Tasmania.

M. pilosa var. stuartii (Stalked Hairy Mitrewort). Closeup. Tasman Peninsula.

Still, the disparity between the two varieties makes it difficult to accept at face value that it is all the same species. The long pedicels versus the short pedicels on the different varieties would make most think the two were different species. Moreover, the difference in hairiness could also strengthen the argument that there might be two different species here.

According to the Student’s Flora though, plants from different localities exhibit a range of variation, making the assignment of a specimen to a variety difficult in some instances.

As with the Finger-orchids I have written about, this is possibly a species complex worthy of a further taxonomic-molecular study.

Caladenia carnea (Pink Fingers)

One of the largest orchid genus in Tasmania must be Caladenia, of which the island (including the smaller islands off the state) boasts 36 species. That makes it one of the largest genera of plants in Tasmania.

While members of the Caladenia are a morphologically diverse, they are readily recognizable by gist in the field.

There are at least 2 different forms: the small flowered ones are more commonly known as Finger orchids while those with long sepals and petals are usually known as Spider orchids.

Just in the bush around Hobart alone, at least a third of the 36 Caladenia species occur. One of them, the small flowered Caladenia sylvicola (Forest fingers), is an endangered orchid with very few known records.

C. fuscata (side view showing streaks on column)

According to The Orchids of Tasmania, the species was first collected in 1992 in a locality near Dynnyrne, under heathy Silver Peppermint (Eucalyptus tenuiramis) forest. A larger colony was later found in 1994 in the same vicinity.

In my visits to the area I have found two species of Caladenia co-occurring there. These are namely Caladenia carnea (Pink Fingers) and C. fuscata (Dusky Fingers).

In the species key given in Orchids of Tasmania, C. sylvicola is distinguished from C. fuscata and C. carnea by the lack of the pink, red or purplish bars that streak the column.

C. sylvicola? (streaks absent on column)

On the 16th October 2004 I was botanizing in a bush near the Waterworks Reserve and I stumbled on a strange looking Caladenia, growing amongst a vibrant population of C. fuscata.

This mystery orchid was totally white and had yellowish calli (protuberances found inside the column of many orchids). There was only one plant and I figured it was just a white form of either C. fuscata or C. carnea.

In the Orchids of Tasmania book, the description for Caladenia sylvicola was the closest match to what I had found.

Caladenia sylvicola (Forest Fingers)? 16 Oct 2004

If my identification is correct, that would the first time it has been seen for over a decade. Apparently, the esteemed photographers from the Up Close website had also encountered a similar orchid which they left unnamed. Unfortunately, they left no date or location on their website as to when they photographed the flower.

In any case, I did not see the presumed C. sylvicola for another 5 years, despite serious searchs.

Then this year, on the 22 Oct I spent an evening orchid hunting around the vicinity and spotted a single ghostly white orchid. It has a slightly damaged dorsal sepal but in all respects was similar to the one I had seen half a decade earlier.

Caladenia sylvicola (Forest Fingers)? 22 Oct 2009

Again, this single specimen was co-occuring with large number of C. fuscata (Dusky Fingers). I also know from past encounters that the area is also a haunt of C. carnea (Pink Fingers).

This begs a question.

Could C. sylvicola just be an aberrant albino or just a pure white form of C. fuscata or C. carnea?

C. carnea tends to be a bit larger and taller than C. fuscata and C. sylvicola. C. carnea also has the ability to bear two flowers per scape, a feature not observed in C. fuscata and C. sylvicola. It is unlikely then, to be confused with C. sylvicola.

With C. fuscata however, other than the pink bars on the column and the coloration of the petal, sepals and calli, there were little other morphological features differentiating this species and C. sylvicola.

In the aspects of stature and calli arrangement, the two were indistinguishable.

I did not collect the single specimen of the presumed C. sylvicola as it would be a legal offense to collect threatened plants. However, I did take a long hard look at the calli of both species in the field and could not discern and any differences in the arrangement of the calli. With the exception of colour differences, both had two rows of calli extending into the column in a similar fashion.

C. fuscata - pink and white form side by side

Also, C. fuscata in the area exhibited a wide range of colour from deep pink to white, with white ones occurring at a much lower frequency.

In the latter case, there are red/purple streaks marking the labellum and column as with the typical pink forms.

The idea that C. sylvicola may be a totally white form of C. fuscata may not that hard to believe.

I use the example of an orchid of another genus, Chiloglottis. The Small Bird orchid (Chiloglottis grammata) is typically dark purplish brown but greenish purple and pure green forms exist. Yet by virtue of their calli patterns the green and dark purplish-brown forms are all called Chiloglottis grammata.

Another argument would be that the two times I have sighted the presumed C. sylvicola, they popped up in the middle of a healthy C. fuscata population, the latter species displaying different shades of petal and sepal color ranging from deep pink to white. It is therefore easy to conceive of C. sylvicola as just being at the farthest extreme of the color and pattern themes of C. fuscata.

Other questions arise from this mental workout.

If C. sylvicola is a real species, could it have evolved from C. fuscata, perhaps by mutation? If so, C. sylvicola doesn’t look like a species that is doing too well.

What these speculations need are scientific studies using a combination of morphological and molecular analyses. Some workers have already developed, from some species of Chiloglottis, certain DNA markers called microsatellites. These microsatellites, if they can be developed for Caladenia, can be useful in finding out the relationship between C. sylvicola, C. fuscata and C. carnea.

There really is much we have yet to know when it comes to orchids. But then again, isn’t it the same for just about anything?

I am so excited. It is time to do a sales job. The long awaited Tree Flip is out.

Another masterpiece by Rob Wiltshire and Greg Jordan from the School of Plant Science  (UTAS), the TreeFlip follows on the heels of the success of the eucaflip (a similar, flippable field guide to the eucalypts of Tasmania). It has the same feel and lives up to (in my opinion excceeds) it’s predecessor in the layout and pictures.

Here’s what the TreeFlip offers for each of the 31 tree species featured:

- common and scientific names

- easy-to-interpret key characters for identification

- pictures of leaves

- pictures of flowers

- pictures of fruits

- bark characters

- distribution maps

- brief geographical/ecological information

Moreover, the TreeFlip is portable and definitely built for all-weather conditions. 

Perhaps we can look forward to soon seeing a ShrubFlip, HerbFlip, AlpineFlip, AcaciaFlip. But in the meantime, I’ll waste no time in getting a copy of the TreeFlip today.

Saltmarsh at Sorrell. The grey patch is a large mat of the Silky Wilsonia (Wilsonia humilis)

In November 2008 I had the privilege to participate in an African Boxthorn (Lycium ferocissimum) weeding trip at a beautiful saltmarsh in Sorrell with my fellow DPIW colleagues Mick Ilowski and Adam Smith.

The reason for doing weeding at the saltmarsh was because a threatened species, the Silky Wilsonia (Wilsonia humilis) grows there.

The Silky Wilsonia (Wilsonia humilis) is listed as rare under the Tasmanian Species Protection Act and the African Boxthorn invasion into the saltmarsh would possibly be quite detrimental to the health of the Silky Wilsonia populations there.

If you have ever seen morning glories you would never have imagined that Wilsonia humilis is anywhere remotely related to it (see also my post on the Golden Dodder).

Unlike it’s typical twinning morning glory cousins, native Tasmanian Wilsonias have succulent leaves and very small flowers (compared to typical morning glories). It is only by virtue of their floral structure that the Wilsonias belong within the morning glory family (Convolvulaceae).

I imagine that the Silky Wilsonia would make a fabulous lawn plant. There are simply little words to express the exquisiteness of those succulent greyish and densely overlapping leaves.

Flowers of Wilsonia humilis

Leaves of Wilsonia humilis

The succulence of the leaves is an adaptation to the saline conditions of the saltmarsh habitat and it never fails to amaze me how numerous unrelated families of plants have adopted succulence in order to survive in saline environments.

In any case, the exuberance of Silky Wilsonia in the Sorrell saltmarsh was simply amazing.

According to Richard Schahinger, a botanist from DPIW’s Threatened Species Unit, this salmarsh probably has one of the most healthy looking populations of the plant. I can’t disagree.

Narrowleaf Wilsonia (Wilsonia backhousei)

The Sorrell saltmarsh also has another very different looking Wilsonia species there, the Narrowleaf Wilsonia (Wilsonia backhousei).

The Narrowleaf Wilsonia is not threatened but is no less fascinating. The thin elongated sky-ward pointing corollas made me think of little trumpets. If I could but hear the tunes they play?

Ozothamnus antennaria (Sticky Everlastingbush)

In Tasmanian botany I was taught the concept of a cline, where a plant species seems to metamorphose into another species along an environmental gradient. In other words, what is considered a plant species at one end of a environmental continuum (eg, the base of a mountain) shows continuous morphological variation and seems to become another species as one goes up a mountain.

The most quoted and classical example of this would be that of the eucalypts, where you might see the Yellow Gum (Eucalyptus johnstonii) grading into the Alpine Yellow Gum (Eucalyptus subcrenulata), which grades into the Varnished Gum (Eucalyptus vernicosa) along some mountains in Tasmania.

I have often wondered how the concept of clinal variation might apply to other Tasmanian plants.

Ozothamnus rodwayi (Alpine Everlastingbush)

An example I had in mind was of the Tasmanian Everlastingbushes (Ozothamnus spp.).

In particular, the high altitude Sticky everlastingbush (Ozothamnus antennaria), Alpine everlastingbush (O. rodwayi) and Mountain everlastingbush (O. ledifolius) seem to exhibit morphological features that makes it easy to imagine that these species somehow evolved from one to the other or graded from one to the other along some sort of a environmental gradient.

It is easy to imagine the leaves of O. antennaria (which grows at slightly lower altitudes from it’s two relatives) becoming smaller and the flower heads getting more compact until it becomes something like O. ledifolius, the morphology of O. rodwayi being intermediate.

Ozothamnus ledifolius (Mountain Everlastingbush)

Not sure if this betrays any relationships: O. ledifolius smells vaguely of cinnamon spice and O. rodwayi seems to have a similar, albeit fainter smell. O. antennaria has the faintest smell last I took a sniff.

In any case, the idea of a cline in the everlastingbushes could be fallacious. But afterall, all good science starts with a conjecture, insane as it may seem. It would really be an interesting hypothesis to test using molecular methods, wouldn’t it.