Western Australian Fossil Plants and Climate

Dr Ken McNamara, University of Cambridge was guest speaker for Armadale Branch meeting in April 2017.

Ken began his talk by stressing the importance of looking at the nature of rocks and fossil plants in helping to understand past climates. In particular they have helped show that over the last half a billion years, the Earth has experienced long periods of alternating ‘Greenhouse’ and ‘Icehouse’ worlds. During the former, CO2 levels and global temperature were much higher than in the current ‘Icehouse’ world we inhabit.

Ken’s talk centred on two fossil plant sites, both of which have only received preliminary studies. One, dated at about 130 million years old (Cretaceous Period) is near Kalbarri. The other, about 40 million years old, is at Walebing, east of Moora. They are very different from one another in that the older site near Kalbarri contains plants living before the advent of flowering plants. The fossils show that the area was dominated by ferns (about 40% of the flora), including gleicheniacean, dipteridacean and osmundacean types. The rest of the flora was mainly arauraciacean conifers (25%) and an extinct group, the seed ferns (25%). The rest are forms yet to be identified. Some of the seed ferns are similar to fossils found in India, which was close to Australia at this time. While much of the fossil plant material is leaves and broken branches, there are a number of seeds and also frequent seed scales from the conifers.

Like this Cretaceous flora, the younger 40 million-year-old (Eocene Epoch) Walebing site preserves the fossils as impressions in very silicified sandstones. These rocks are known as silcretes and reflect formation at a time when the climate was much wetter and warmer than today, despite being located at much higher latitudes than now (55°–60°), with pronounced seasonality. The fossils are very common and reflect a very diverse flora, dominated by proteaceans, such as banksia, grevillea and possibly macadamia. The very diverse array of banksia leaf types show biodiversity levels were high even at this time, and probably had been on the nutrient-poor soils for tens of millions of years before, back into late Cretaceous times.

As well as these sclerophyllous plants the flora also contains rainforest elements, such as the Southern Antarctic beech, Nothofagus and many myrtaceous leaves that resemble modern rainforest types. Araucareaceans are still present, as well as casuarina-type fruiting bodies, including some types present today only in rainforests in eastern Australia and New Caledonia.

Study of the leaves of one of the banksia species, B. paleocrypta, shows that it has sunken stomata, suggesting that it was preadapted for the drying out of the Australian continent that has occurred over the last 25 million years or so. The rainforest elements have disappeared from WA, leaving only those forms, such as the proteaceans, that were preadapted to both the nutrient-deficient soils and the seasonal periods of low water availability.

In his closing comments, Ken pointed out that much more work needs to carried out on these floras. This will help provide a better understanding of the evolution of the rich flora that we see in Western Australia today.

Nothofagus and Banksia leaves, Walebing (Photo: K. McNamara)
Kalbarri fern, Microphyllopteris (Photo: K. McNamara)

 

Be Awarded, Be Connected – Student Prize Winners.

The student prizes are one of many ways we as a society try to bridge the inter-generational gap. And the older folks have a lot to share, believe me!

Perth Branch is supporting UWA students; Northern Branch is looking at ECU while Murdoch Branch is obviously looking for the best students around its own bush that is Murdoch University and TAFE Challenger.

Last two years Murdoch Branch had a great honour to award four outstanding people. Pawel – our (tall) president of the last two years (2015-2016) is very happy to hand over the awards to:

1.     Merryn – the best student in “Plant Diversity”  in 2015:

From Left: Secretary Christina Birnbaum, The Winner Merryn Prior, President Pawel Waryszak.
From Left: Secretary Christina Birnbaum, The Winner Merryn Prior, President Pawel Waryszak.

Continue reading “Be Awarded, Be Connected – Student Prize Winners.”

Talk by Michael Morcombe on Pollination

This talk was given by Michael Morcombe on the 12th November 2015 at the Armadale branch general meeting.

Prior to the business meeting, the guest speaker for the evening was fellow member Michael Morcombe, whose topic was Pollination in an isolated region outlining the diverse and unique tactics by plants, insects, birds and mammals.

Michael explained briefly how he became interested in this field by explaining that he was asked to write a book in which pollination was a part,but couldn’t actually find anything on pollination in the southern hemisphere in the university library.  This began a long and interesting journey recording just how plants are pollinated in Australia resulting in many long road trips for his family and a lifelong interest in photographing their finds for Irene.

We have a unique flora here in Western Australia,so Michael showed some wonderful slides, many taken by Irene, of how the plants use insects, birds and mammals to help them with their pollination.  Plants have adapted to be insect-pollinated and many have long tubes which cover the insects in pollen.   Insects can see ultra-violet light and so what looks like a plain flower to the human eye actually shows a pathway to the nectar through the insects’ eyes.  Generally insects are attracted to blue/purple/white flowers while birds are attracted to red/yellow flowers.

Orchids are very clever and have evolved to play tricks on insects.  Many have parts which mimic female wasps and the orchid will therefore attract the male wasp dabbing a spot of pollen on his tail.   Flowers are very specific about using their pollen much like delivering letters.

Banksia flowers have evolved to attract birds and provide a perch, pollen and insects.  The pollen goes on the bird’s face and head.  The flowers are densely packed so that they are not attractive to insect pollination.  The fascinating thing about flowers is that depending on what flower the bird is attracted to, depends on where the flower will deposit its pollen on the bird.  Michael said it was entirely possible that a Dryandrawill deposit its pollen on the bird’s head while Anigozanthospollen will be deposited on a bird’s back.  Other plants may deposit their pollen on the breast so that the bird can virtually carry different pollens all over its body from many different plants.

Mammals such as the Honey Possum with its long snout will pollinate flowers as well as Fairy Gliders and Dibblers (a native rat which was presumed extinct for 83 years until it was rediscovered in 1967).

http://www.michaelmorcombe.com.au/dibblerstory.html

 

Dibbler
Dibbler

 

Sandpaper Wattle, Acacia denticulosa

Among the hundreds of species of Acacia, Acacia denticulosa, Sandpaper Wattle, is one of the most striking. The species was first collected near Mt Churchman by Jesse Young, a member of Ernest Giles’ expedition across the Great Victoria Desert in 1875. Young (1852–1909) was the astronomer and principal plant collector (assisted by William Tietkens). With the consent of Thomas Elder, sponsor of the expedition, he passed his specimens to Ferdinand Mueller, Government Botanist of Victoria (remember, there was no botanist in WA then). The collection totalled about 400 species, of which some 63 were new. Mueller named many of these, including this species, published in 1876. The name refers to the toothed margins of the phyllodes but perhaps the more unusual feature of these is the very rough surface from which the common name is derived. This is due to short, conical outgrowths with gland-like tips that are scattered over the lamina and edges of the phyllodes. The phyllodes and young branchlets (also rough at this stage) are slightly sticky.

In the wild the plant is a shrub up to 4 m tall (bottom left) but in the garden it grows to 6 m and can spread to 8 m wide (bottom left). It has an open, rather ungainly habit. Its bark is almost smooth, pale greyish brown, or brown when wet (bottom right). In full flower the tree appears covered with large, golden, woolly caterpillars (centre left).

I bought my plant as a small seedling in April 2008. It grew quickly and by August 2010 was already 3 metres tall.  Since 2010 it has flowered well, starting in July and continuing to the end of August. One reason for its colourful show is that it usually has several spikes per axil. They have a faint ‘wattle’ scent. The fruit is relatively inconspicuous, being a narrow, undulating pod up to 7.5 cm long and 3–4 mm wide, holding small, dark brown shiny seeds (centre right).

The species has no close relatives. The plant has no lignotuber, hence is killed by fire and regenerates from seed. Given adequate space it does not require pruning.  Should this be necessary it should be done progressively as the plant grows, never cutting below the foliage.

Sandpaper Wattle is rare in the wild, known mainly from granite outcrops from near Mt Churchman south-east to Nungarin, with a record near Wongan Hills. It is a Declared Rare Flora (Threatened). Like another rare species from granite rocks, Eucalyptus caesia, it is proving amenable to cultivation.  A plant in the garden of the previous WA Herbarium grew to a large size.

-Alex George

Sandpaper 1 Sandpaper 2 Sandpaper 3 Sandpaper 4

Photos by Alex show the habit, bark, flowers and young pods.

 

References

Brooker, Lesley (2015), Explorers Routes Revisited: Giles 1875 Expedition, Hesperian Press, Carlisle.

Maslin, B.R. & Cowan, R.S. (2001), Acacia denticulosa F.Muell. in A.E.Orchard & A.J.G.Wilson (eds), Flora of Australia 11A: 238, 368, 370, 481, ABRS, Canberra, & CSIRO Publishing, Melbourne.

On Banksias, Dryandras, and Hairy Fish

Classification has always been about putting similar things in the same box. It is how one defines “similar” that changes. The earliest classifications were presumably pragmatic: things you could eat in one box, things you couldn’t eat in another, things you could use for medicines in yet another. In modern classification the idea of evolution determines what is thought to be similar. Hence, one criterion is that all the organisms in the one box should have evolved from a recent common ancestor. No problem there: both Banksias and Dryandras can be assumed to have a recent common ancestor. It is the second criterion that is tricky: all the descendants of a recent common ancestor should be in the same box. Dryandras can be assumed to have evolved from within the Banksias and therefore this criterion requires that they both be in the same genus.

Let us see what happens if we apply these criteria to humans. The mnemonic for remembering the higher classifications is: King Philip Came Over For Good Soup. (Kingdom, Phylum, Class, Order, Family, Genus, Species.) We are in the Kingdom Animalia, Phylum Chordata, Sub-Phylum Vertebrata, and Class Mammalia. Other Classes at the same level are: jawless fish (lampreys and the like); cartilaginous fish (sharks and rays); bony fish; amphibians; reptiles; and birds. Reptiles includes lizards and snakes, crocodiles, turtles and dinosaurs.

The first problem is that birds certainly evolved from dinosaurs. The reptile class therefore does not include all the descendants from the one ancestor; birds must go into the dinosaur box. The next problem is that mammals must have evolved from primitive reptiles, so by the same logic, mammals must also go into reptiles. Those of you who think that Dryandras should be sunk into Banksias must therefore think of themselves as hairy lizards.

But wait, there is more. Where did reptiles evolve from? Surely from bony fish. So reptiles and fish should not be at the same level: reptiles, together with birds and mammals, all must go into the fish class. You are not hairy lizards after all: you are hairy, air-breathing fish.

Or we could decide that it was rather silly and abandon the second criterion.

Jim Barrow