Dryopteris wattsii (Dryopteridaceae)

A young specimen of Dryopteris wattsii in the Cairns Botanical Gardens.

As it can easily be guessed, the Wet Tropics of Australia is a prime spot for ferns in Australia. Although much can be said in praise of the luxuriousness of ferns in the temperate rainforests of Melbourne and Tasmania, a huge proportion (~65% or over 250 species) of the fern species in Australia is found in the Wet Tropics.

Additionally, about 40 species are endemic to the region, and the species of this post, Dryopteris wattsii is one such species.

The attractive pinnate frond with dark shiny green uppersides.

Perhaps even more notable is the fact that Dryopteris wattsii was once called Revwattsia fragilis, and was considered the only member of the genus, i.e. it is a monotypic fern. In other words, not only was the species endemic, there are no other member of the genus anywhere else in the world.

Still earlier 1915, the fern was named by Reverend W.W. Watts as a member of Polystichum, a well known genus of “shield ferns” in Australia and elsewhere. Like some Australian species of Polystichum, this fern has attractive long fronds (1-2m long), with a great potential to be used as an ornamental.

However, various morphological features make the inclusion of this fern in Polystichum unacceptable. Some of these are the long-creeping rhizomes, kidney-shaped indusia (the spore bearing pouches), and the epiphytic habit are not characteristic of Polystichum.

In the 1980s the eminent pteridologist (a specialist in ferns) SB Andrews in the landmark work Ferns of Queensland suggested that the species be recognised as a separate genus, and later botanist David Jones, in recognition of Reverend Watts, endowed the fern with a new genus name, Revwattsia.

Any close relationship with Polystichum was dealt the nail in the coffin when Meghan McKeown and colleges applied phylogenetic analyses on the species to understand where the species fits within the Dryopteridaceae fern family.

Using a number of chloroplast DNA markers , McKeown and colleges were able to investigate the relationships of Revwattsia fragilis within Dryopteridaceae. Their results confirmed that Revwattsia is distinct from Polystichum, but at the same time they also delivered a severe blow to the name Revwattsia, as they found that the species is much more related to southeast Asian species of ferns from the genus Drypoteris.

To this end, McKeown and colleges therefore proposed that the species be renamed Dryopteris wattsii. They probably considered calling the species “Drypoteris fragilis“, but the species epithet “fragilis” was already taken up by another species elsewhere.

Thus we have it. The shifting tides of taxonomy and phylogenetics have conferred an insignificant addition to the burgeoning 250 odd species of Dryopteris worldwide, but annihilated a monotypic genus from the Wet Tropics. Perhaps it is for the better that any allusion to fragility (“i.e.”fragilis“) was removed, and that a hint of reverence for Reverend Watts is maintained after the dissolution of “Revwattsia“.

Frond underside of the frond. More pictures to come when I get lucky enough to see the species in sporulation.

Monotypic or not, Dryopteris wattsii remains an important fern for conservation in the Wet Tropics. Dryopteris wattsii is a rare treasure and is known only from six small populations in wet rainforests in the Atherton Tablelands, with a combined total of less than a dozen plants.

To conserve the species, Christine Cargill and Jen Johnston recommend that the species be cultivated more widely. In their studies that found that the species is slow-growing and require a number of years and repotting before attaining the large mature fronds found in wild populations. In consolation however, they state that “developing juvenile plants are also attractive, and the grower should not be disappointed as with time and patience potted juveniles will grow to maturity if correctly nurtured.”

References

Andrews SB (1990) Ferns of Queensland. Queensland Department of Primary Industries. Brisbane.

Cargill, D. C., & Johnston, J. (2009). The Biology and Cultivation of Revwattsia fragilis (Watts) DL Jones. URL: http://aff.org.au/Cargill_Revwattsia_Final.pdf

McKeown M, Sundue M, Barrington D (2012) Phylogenetic analyses place the Australian monotypic Revwattsia in Dryopteris (Dryopteridaceae). PhytoKeys 14, 43.

Jones DL (1998) Flora of Australia, Ferns, Gynosperms and Allied Groups.Vol. 48, Melbourne: ABRS/CSIRO Australia.

Watts WW (1915) [‘1914’] Some notes on the ferns of north Queensland. Proceedings of the Linnean Society of New South Wales Series 2, 39: 775, t. lxxxviii, fig. 9A–G.

Searching for truth beneath bark

The famed Australian poetess Judith Wright wrote in her poem The Forest:

“When first I knew this forest
its flowers were strange…

…time was to spend
and time’s renewing harvest
could never reach an end

Now that its vines and flowers
are named and known,
like long-fulfilled desires
those first strange joys are gone”

I resonate deeply with this poem as it speaks to my personal journey with the tropical rainforests of Far North Queensland.

Although I cannot claim to know all the trees of this forest, many are now familiar.

I can roll off my tongue sleek-sounding scientific names of trees like Beilschmeidia bancroftii, Eupomatia laurina, Macaranga tanarius, off my tongue. It was self-gratifying to know these names, but this is no longer satisfying.

My quest to know plants have gone deeper still – and now I am delving deep beneath their bark.

As an ecologist, I have always had a deep yearning to understand how tropical rainforest plants can find solutions to living in a common environment.

How do the grand tropical laurel trees raise those lofty crowns to the canopy? What has come with being a shrub and giving up with the competition for growing tall? And just how do lianas do their thing?

Just like people having a diversity of professions to provide different services to their community, trees, shrubs and vines are just some of the ways tropical rainforest plants have diversified into different ecological groups to cohabit a forest environment.

Trees occupy different strata in the forest. Sun-loving canopy species claim the prime spots in the well-illuminated canopy, while shorter trees make do with the shade of the subcanopy.

Then there are also “sun-fearing” shrubs that have found their place in the deep shade and barely grow taller than 2 meters.

Conspicuously in tropical rainforests also, there are thick-stemmed lianas whose gnarled-twisted stems tangle and literally tie the forest together.

And also, there are more open or marginal environments in tropical rainforests, where a suite of pioneer species reside. These species of trees and shrubs are more able to cope with disturbance and exposure, and are typically hate to be in the shade.

So the question arose as to whether plant from all these different lifeforms will have different ways to ecological strategies to deal with the needs to transport water.

Following some of investigations in plant water transport in tree species in an earlier work in the journal PLOS ONE, I became smitten with the inner mechanisms of plant, and fascinated how the little pipes or the vascular system within a plant’s stem enable a plant to conduct water. This earlier study had looked at just 8 species of trees, and I just had to see more.

Based at James Cook University, my colleges and I we set out to investigate how wood anatomy may reveal the different ecological strategies of rainforest plants, which has recently come out in Functional Ecology.

Needless to say, our study was based in the Daintree, one of Australia’s prime lowland tropical rainforest. I’ll probably be shameless and say that we used the permanent monitoring plot for which we had previously published a full species list for.

We collected stem wood from 90 species of plants (15 species each) from within six ecological groups: mature-phase trees, understorey trees, understorey shrubs, pioneer trees, pioneer shrubs and lianas. And in the lab, we made wood stem sections for microscope analysis to measure vessel features such as vessel sizes, frequencies and grouping. These features can be hypothesized to have a direct influence on water transport and plant performance.

Next we wanted to understand how anatomical characteristics of plant vessels influences plant performance. For this we used the leaf material for biochemical analysis, looking at leaf carbon isotope ratios. Basically, this analysis would enable us to get an idea of how well our study plants are photosynthesizing and how efficiently it is using water.

I also got to use the Daintree Rainforest Observatory canopy crane to collect some of our samples. This construction crane is one of a global network of dedicated cranes used for scientific research work. With great mastery, the crane operator Andrew Thompson took us within the gondola 30-35m above the canopy of the trees where we could collect leaf samples with ease.

For mature-phase canopy trees such as the Pink Satinash (Syzygium sayeri) which can get to over 30m tall, canopy crane access to leaves are certainly appreciate.

Mature-phase trees such as the Pink Satinash (Syzygium sayeri) have typically large vessels.

(Fast forward from the gruelling laboratory, analysis and writing sessions). viola! Our results show that yes, plant performance (how well our plant ecological groups use water) is related to the size of the vessels. One interesting conclusion we could draw from our results was that vines are very much like pioneer trees in their potential efficiency in transporting water, and also in terms of their plant performance.

Shamelessly again, I point to our published article for the sciency nitty gritty.

What we could not show in our article was the joy of seeing the inner workings of species that we have come to know so well.

Trees clearly had larger vessels than shrubs, as one might expect from the stature differences between these two ecological groups. However, within both, there is much diversity in the way the vessels appear.

The Buff Beech (Gomphandra australiana), an understorey tree revealed a beautiful intricate pattern of vessels, fibre, and parenchyma cells that would be worthy of a t-shirt print.

The alternate patterning of parenchyma rays and vessels in the Buff Beech (Gomphandra australiana), an understorey tree

In terms of vessel size, the local Bernie Bean (Mucuna gigantea) has the largest vessels of them all. This could be seen with the naked eye upon making a stem cutting.

But beyond having big vessels, we found that vines have a huge diversity of patterns in their stem anatomy, in particular the way they arrange their parenchyma tissues. This diversity is in and of itself worthy of a dedicated study.

The Common Milk Vine (Pycnarrhena novoguineensis) and it’s drammatic wood anatomy.

So to close, you might ask if I found the “deeper truth from which they spring” poring through thousands of vessels.

I will say that I thought I came close, but it was just a whiff. The truth is still in there, deep into the essence of what constitutes a plant, and beyond the vessels that we can see in our microscope slides. And again the closing stanzas of The Forest echos in my heart:

“My search is further.
There’s still to name and know
beyond the flowers I gather
that one that does not wither-
the truth from which they grow”

Vegetation of a piece of Australia’s prime rainforest

Australia’s prime rainforest estate at Cape Tribulation.

Having started this blog almost 6 years ago and spending some years learning the flora of the region, I have had the great previlege to examine closer, in a scientific way, the flora of a patch of Australia’s prime rainforest estate. And there is probably few places that can match the Daintree to have such an opportunity.

These research culminated in a recently published paper [download pdf] in the free-to-read open access Biodiversity Data Journal, an apt place to publish forest plot and species diversity data.

The lowland rainforests at the Daintree and areas around Cape Tribulation have been touted as representing the prime development of rainforest in Australia, because of their complex structure. Alluding to this complexity, these forests have locally been called “Complex Mesophyll Vine Forest”.

When I first got the opportunity to work at the Daintree in earnest in 2013, there was already a 0.95 hectare (now extended to 1-ha) long-term rainforest monitoring plot in existence. This plot was set up in the year 2000 and so has been monitored for over 15 years.

Although other tropical countries have much larger monitoring plots, this plot is Australia’s largest lowland rainforest plot. Strategically, this plot is also situated under the canopy crane, and is in fact the only place in Australia with a canopy crane to study rainforest, and one of a few in the world.

Such is the significance of this infrastructure that a research station, the Daintree Rainforest Observatory, was built to administer research activities on the canopy crane. Not surprising, there has been quite a wonderful list of ecological and biological research conducted from the crane.

The Daintree Rainforest Observatory “rebooted” in 2014. Now furnished with space for over 40 people.

I was tasked to set up another 1-ha plot to complement the one already in existence, and this involved going out into the forest, tagging, marking, identifying and measuring the trunk diameters of these trees.

It was gruelling and bloody (literally) work – a kind of intensive outdoor gardening which required the pruning of spiny vines to create access paths and to lay out 20x20m grids. And it was certainly not possible to complete without the help of many kind volunteers.

Working in the canopy crane

But I was in a kind of “plant heaven”, having an opportunity to make close friends with the plants in such a beautiful rainforest region, and not just the trees.

Later between 2014-2015, I when back to lay out a few small plots in the understorey to have a closer look at the abundance of shrubs and tree saplings, and also to do an overall flora survey of the 42-ha research station. While such an ad hoc survey may not be very precise in terms of the number of the species present at the site, we did find some 385 native plant species at the site which is certainly a good representation of the diversity of the forests in the Daintree region.

In terms of the plot, the tree diversity of ~80 species per ha was not particularly high by world standards, but what was interesting was the number of stems exceeding 10cm diameter (>800 stems per ha). This is higher than most places with permanent plots, and could be a result of regeneration from cyclones that occasionally visit these lands.

I hope that this work will form a firm ecological basis for other hypothesis-driven studies, and also for further studies looking at the rainforest vegetation of the Wet Tropics of Australia.

Carpentaria acuminata (Arecaceae)

Carpentaria acuminata (Carpentaria Palm) is the sole species in the genus Carpentaria, which is native to tropical coastal regions in the north of Northern Territory, Australia. Due to it’s attractive form and red fruits, it is widely grown in Cairns as an ornamental.

As in the Northern Territory, the Carpentaria Palm is an important food source for Torresian Imperial Pigeons (Ducula spilorrhoa).

Clerodendrum splendens (Lamiaceae)

Commonly by various names such as the Flaming Glorybower, this vigorous vine, native to tropical Africa, is grown for its showy and ornamental red blossoms.

Beautiful these flowers are! – brilliant bright red, very showy, and borne in terminal clusters. The flower corolla is fused into a tube, lobes spreading to 2 cm long. The stamens with their red filaments protrude quite conspicuously out of the corolla like whiskers.

Few people who cultivate this vine probably know that they have an ornamental pharmacopeia at they doorsteps.

In it’s native range in Western Africa, extracts of roots, leaves, and bark from C. splendens are used in traditional medicine to treat various ailments ranging from malaria, coughs, skin diseases, ulcers, rheumatism, asthma, and uterine fibroid, and venereal infections, including gonorrhea and syphilis (Shrivastava & Patel 2007; Okwu & Iroabuchi 2008, 2009; Gbedema et al. 2010).

Recent research further suggests that polysaccharides from leaves of the plant have ability to modulate the immune systems, and may thus have beneficial effects for people with autoimmune disease (Kouakou et al. 2013).

Impressive list for a garden ornamental!

References

Gbedema SY, Emelia K, Francis A, Kofi A, Eric W. 2010. Wound healing properties and kill kinetics of Clerodendron splendens G. Don, a Ghanaian wound healing plant. Pharmacognosy Res 2:63–68.

Kouakou K, Schepetkin IA, Jun S, Kirpotina LN, Yapi A, Khramova DS, Pascual DW, Ovodov YS, Jutila MA, Quinn MT. 2013. Immunomodulatory activity of polysaccharides isolated from Clerodendrum splendens: Beneficial effects in experimental autoimmune encephalomyelitis. BMC complementary and alternative medicine 13: 149.

Okwu DE, Iroabuchi F. 2008. Isolation of an antioxidant flavanone diglycoside from the Nigeria medicinal plant Clerodendron splendens, a. Cheval. Int J Chem Sci 2008, 6:631–636.

Okwu DE, Iroabuchi F: Phytochemical composition and biological activities of Uvaria chamae and Clerodendoron splendens . E-Journal Chem 2009, 6:553–560.

Shrivastava N, Patel T. 2007. Clerodendrum and healthcare: an overview. Medicinal Aromatic Plant Sci Biotech 1:140–150.

Loropetalum chinense (Hamamelidaceae)

Loropetalum chinense, known commonly as the Chinese fringe flower, is a ornamental species of the witch hazel family, grown as a hedge plant in certain places around Cairns and the Tablelands.

Cladopus queenslandicus (Podostemaceae)

Plant life is believed to have begun from aquatic origins. As any biology textbook would show, the oldest lineages of land plants (i.e. bryophytes – liverworts, hornworts and mosses) are highly dependent on water for sexual reproduction, and are therefore often found close to permanent freshwater sources or moist conditions.

Many liverworts for example have thalloid bodies – i.e. rather than leaves they have a body consisting of a flatten film of photosynthetic tissue, very much like a lichen. This allowed them to adhere tightly to substrates. Later in their evolution, liverworts started to evolve leaf-like structures (Read the fascinating story of how liverworts may have started making leaves)

When flowering plants came onto the scene, they also radiated into freshwater habitats, and they found a myriad of exciting ways to live in water.

For one family of aquatic flowering plants, the Podostemaceae, the return to life in the water came with a “reverse innovation” – it seems to have “relearnt” how to be a liverwort.

One very prominent member of the family in tropical Queensland is Cladopus queenslandicus. This aquatic flowering herb has very interesting plant form. The stems have very basic fleshy leaf-like structures which are ridged on the back. These fleshy structures resemble those of liverworts that have are in a transitional stage between being thalloid and leafy (See illustrations online).

The stems of Cladopus queenslandicus showing liverwort-like overlapping fleshy leaves.

The roots have a thalloid form like a liverwort, and is obviously quite specialized to be able to grip onto rock substrates. Indeed, Thus, experts on the family suggest that the root is the leading organ in the
body plan of most Podostemaceae, reflecting a remarkable adaptation to a unique aquatic environment, i.e., the border between rock surfaces and fast-running water (Koi et al. 2006).

The flattened thalloid roots of Cladopus clasping onto rock substrates.

Fascinatingly, the closest relatives of the Podostemaceae are from the mangosteen family – an excellent example of how evolutionarily plastic plant form can be.

C. queenslandicus is found in fast-flowing water or torrents near waterfalls around the Ravenshoe region (i.e. Little Millstream Falls), and also in some localities in Malaysia and PNG. It was previously and much more descriptively named Torrenticola queenslandica by karl Domin.

References

Koi S, Fujinami R, Kubo N, Tsukamoto I, Inagawa R, Imaichi R, Kato M. 2006. Comparative anatomy of root meristem and root cap in some species of Podostemaceae and the evolution of root dorsiventrality. American Journal of Botany, 93, 682-692.

van Steenis CGGJ (ed). 1948. Flora Malesiana: being an illustrated systematic account of the Malaysian flora including keys for determination, diagnostic descriptions, references to the literature, synonymy, and distribution, and notes on the ecology of its wild and commonly cultivated plants. [See 1949, Series 1, Volume 42, pg 68 (Read relevant page here)]