About Me

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Canberra-based naturalist, conservationist, educator since 1980. I’m passionate about the natural world (especially the southern hemisphere), and trying to understand it and to share such understandings. To that aim I’ve written several books (most recently 'Birds in Their Habitats' and 'Australian Bird Names; origins and meanings'), run tours all over Australia, and for the last decade to South America, done a lot of ABC radio work, chaired a government environmental advisory committee and taught many adult education classes – and of course presented this blog, since 2012. I am the recipient of the Australian Natural History Medallion, the Australian Plants Award and most recently a Medal of the Order of Australia for ‘services to conservation and the environment’. I live happily in suburban Duffy with my partner Louise surrounded by a dense native garden and lots of birds.

Thursday, 21 November 2019

Cycads; ancients with an amazing sex life!

Cycads, now a small part of the world's vegetation landscape, once dominated it. Their fossil record goes back unambiguously to 280 million years ago, with ages of over 300 million years often suggested. The younger figure is still 40-50 million years older than the first dinosaurs; this is a truly venerable plant lineage. The first flowering plants, which in time would overwhelm the cycads with a huge diversity of species, didn't appear for another 135 million years (ie 145 million years ago)!
Burrawangs Macrozamia communis, Nelligen, south coast New South Wales. Cycads have long lived in the
metaphorical shadow of flowering plants, as these common NSW coastal cycads do literally, under
the Spotted Gums Corymbia (formerly Eucalyptus) maculata.Like many cycads, the trunk of this species is underground;
no other cycad in the world grows further south than this one.
Now there are now only around 260 cycad species remaining, scattered throughout the world's tropics and subtropics, usually in drier situations (compared with at least 250,000 flowering plant species). Their superficial similarity to palms can be seen in the photo above, and is often remarked upon. It is totally coincidental however, as palms are true flowering plants.
Nonetheless, this Macrozamia riedlei (here in Coomallo Nature Reserve north of Perth) is often known as Zamia Palm
(or just Zamia) for understandable reasons. It is restricted to dry forests, especially Jarrah Eucalyptus marginata, in the
south-west of Western Australia. It was named for Anselme Riedlé, chief gardener (of a team of five)
on the mighty Baudin expedition of 1800-04, who almost certainly collected the first specimen at
King George Sound (now Albany). Sadly he died soon afterwards in Timor, aged just 26.
Cycads arose, as we have noted, in an unimaginably distant past before flowers developed. They reproduce by pollen transfer between cones on separate male and female plants. It was long assumed that this could only be achieved by wind and chance and that only flowering plants utilise animal pollinators, but these notions have now been challenged by detailed observation of several cycad species. It seems undoubtable now that cycads employed insects to efficiently transfer pollen from male to female cone long, long before flowering plants reinvented the trick. One of the first approaches in such studies is to exclude insects, but not wind, from female cones, and vice versa - repeatedly it transpires that pollination can take place without wind, but not without insects, especially beetles and particularly small weevils. We don't normally think of beetles (other perhaps than jewel beetles) as significant pollinators, but in this case it makes sense as beetles were around, with ancestral cycads, well before moths, flies or wasps were.

In some cases beetles have been observed pupating within the males cones, emerging with pollen attached to hairs on their legs and moving to female cones, entering them when they became receptive. Something must be attracting them. Observations on the NSW south coast Burrawang showed that adults and larvae of one species each of both weevils and thrips (a large order of tiny sap-sucking insects) were feeding and breeding in male cones, and later moving to female ones.
Female Burrawang cones, Nowra, New South Wales.
What's going on to strongly attract insects to them?
Studies of other Australian Macrozamia species revealed some remarkable adaptations on the part of the plants (which have had, after all, plenty of time to develop them!). Thrips like cool, dry, dark places and Macrozamia cones usually fit the bill perfectly. However sometimes the cones go to great lengths to expel them. The cones heat to 40 degrees C, and emit water vapour, carbon dioxide and unpleasant terpenes, which causes the thrips to leave en masse; many of them find refuge in nearby female cones and the pollen is transferred.

Some beetles however quite like it hot, and back in the early 1990s work done on the West Indian cycad Zamia pumila showed that in the evening when beetles were active the male cones heated by as much as five degrees, at considerable cost as starch and fat levels in the cone dropped considerably at the same time. The heat also vapourised a chemical with a "sweet minty" scent (in the opinion of the researchers, but the beetles clearly liked it to), and released a sweet secretion, all evidence that the presence of the beetle was worth a lot to the cycad. The beetles were impressed, spending time and even mating in the cone. This study didn't look at the role of the female cones (curiously perhaps) but more recent ones have.

A south-east Queensland study did so and found another version of this fascinating story. Macrozamia lucida is a species from wet eucalypt forests in south-east Queensland, whose male cones harbour large numbers of thrips which eat the pollen but also carry some of it.

Male cones of MacDonnell Ranges Cycad Macrozamia maconnellii, a close relation of M. lucida.
For about four weeks of the year the M. lucida cones produce pollen, and at this time they also go to considerable lengths to expel their thrip tenants. Each morning the cones burn energy to raise their internal temperature by up to 12 degrees! At the same they they emit high levels of beta-myrcene (widely occurring in aromatic plants but also employed in the perfume industry) which has a "harsh, overwhelming odour" (again the researchers' opinion, but again the insects seem to agree). The thrips all flee, carrying pollen with them. And here it gets really interesting because the female cones now emit modest doses of the same chemical, but at lower levels the thrips find it attractive so they seek shelter there - and the plant's job is done! Then the male chemical levels drop again and the thrips return, and the performance is repeated daily until the male cone's reserves are depleted and the female is well-fertilised.

There are just three living families of cycads, and one of them (Stangeriaceae) comprises only three species, one in South Africa and two in Queensland. The largest is Zamiaceae with some 150 species in the tropics and subtropics of the Americas, Australia and Africa (though higher numbers are sometimes cited too). One subfamily of two genera is represented in Australia, and limited to it. There are about 40 species of Macrozamia, and just two of Lepidozamia. Some Macrozamia are common and familiar in their ranges. We've already met a couple but it doesn't hurt to renew our acquaintance.

Burrawang, Nowra, New South Wales.
This forms a near-dominant understorey to the lovely Spotted Gum coastal forests in places.
This is one of several species the seeds of which Indigenous Australians processed via a days-long
complex process of crushing, soaking and heating to denature the virulent toxins. It has always fascinated me
that people would make the assumption that a food which was fatal could be made edible if they
experimented enough - especially in a food-rich environment like the NSW coastal forests.
Macrozamia moorei, here near Springsure in central Queensland, is common in a limited
area of dry ranges inland from Rockhampton to Maryborough. It is probably
the largest of its genus, growing to tree size.
Macrozamia secunda (here in Goobang NP near Parkes, NSW) by contrast is one of the smallest,
with an underground stem and only one to four fronds which mostly grow close to the ground.
Distinctively the pinnae ('leaflets') grow on just one side of the stem.
Its habitat is dry open forests on the hot mid-western slopes of New South Wales.
One of the best-known Australian cycads however has one of the smallest distributions. The MacDonnell Ranges Cycad, introduced earlier, lives only in the dramatic MacDonnell Ranges of central Australia around Alice Springs and the nearby George Gill Range. They are relics of a wetter past, isolated in the relatively sheltered central ranges by the surrounding deserts.

McDonnell Ranges Cycads clinging to the gorge walls in the ranges;
at Ellery Creek Big Hole above, and Standley Chasm below.

The two Lepidozamia are widely separated in distribution, and both restricted. Lepidozamia hopei, reputedly the tallest of all cycads, towering to 20 metres high, lives only in the Queensland Wet Tropics rainforests. L. peroffskyana, far to the south, has a slightly larger range in wet forests on steep slopes from south-east Queensland to north-eastern New South Wales.
Lepidozamia peroffskyana in wet forest on North Brother Mountain, Dooragan NP near Port Macquarie,
north coast New South Wales. Note the huge female cone.
Weevil pollination has been demonstrated for this species too.
The third family is Cycadaceae, which comprises only the genus Cycas, with some 110 species from east Africa and Madagascar to south and south-east Asia through northern Australia to the Pacific. Perhaps 30 of those are Australian; here are three of them. It is a feature of Cycas that the female doesn't form cones, but carry hard spherical seeds on flattened drooping stalks called megasporophylls - in practice these are best considered 'opened-out' cones. They appear in a couple of these photos.
Cycas media is a common cycad in the woodlands of the Top End around Darwin in the Northern Territory.
It is atypical among cycads in being deciduous in the dry season; this plant is producing new growth.
The megasporophylls are obvious.
Cycas media in the understorey of dry monsoon forest south of Darwin.
Cycas calcicola in a burnt landscape at Litchfield National Park south-west of Darwin.
This is a very restricted species, growing only on limestone outcrops near Katherine (hence calciola)
and here on sandstone slopes in Litchfield. Any plant up here must be fire-tolerant.
Lastly Cycas media is a common cycad in drier forests subject to regular burning in east coastal tropical Queensland. Some authorities say that it is also found in the Top End and northern Western Australia, some do not. I'm still trying to fathom this one.
Flourishing Cycas media, Redden Island, Cairns. Both this specimen and the next display megasporophylls.

Cycas media with new growth, Cooktown.
Cycads are old, magnificent, fascinating - and arguably raunchy. I hope you love them too.

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Thursday, 7 November 2019

Kirstenbosch: one of the world's great gardens

Kirstenbosch National Botanical Garden really is one of the world's great botanic gardens and a delight to visit. This post is based on a visit we paid to it in May this year. It was my third visit, but the others were long ago, before the advent of digital photography into my life, so the photos here reflect just that one very warm and quite windy Saturday morning. It means that they don't really give much idea of the garden's wildlife, but hopefully I can show you enough that you can share my love for this place.

One of the key points of Kirstenbosch is its location at the eastern foot of mighty Table Mountain; the gardens cover a substantial 36ha, but there are also nearly 500ha of wild fynbos (the hugely rich heathlands of the Western Cape) and forest managed by the gardens. It all connects to the even larger Table Mountain National Park. 
View of part of the Table Mountain massif from the nice outdoor cafe/restaurant in the gardens.

Looking up to Castle Rock from one of the many garden paths in Kirstenbosch.
Most of Cape Town is underlaid by 560 million year old sedimentary shales; however under Kirstenbosch
and the whole Cape Peninsula to the south are slightly younger granites.
The hard erosion-resisting cap of Table Mountain comprises tough coarse sandstone.
The true nature of Table Mountain as the northern end of a range can be appreciated from the gardens; the 'table' aspect is only obvious from other and more distant perspectives. 
Table Mountain behind Cape Town from the north, across St Helena Bay.
Kirstenbosch is 'behind and to the left' of the mountain; the rugged peak to the left is Fernwood Peak
which towers over the gardens just to the right of Castle Rock in the previous photo.
But, back to the gardens. We don't know who the Kirsten was of 'Kirsten's forest'; the name was recorded in 1795, though no Kirstens are known to have been associated with it. (It's certainly a Cape Town name though; indeed we stayed nearby at a lovely B and B owned by South African cricketing great Gary Kirsten and his wife Deborah.) The controversial and influential Cecil Rhodes bought the property in 1895, but importantly he left the land to the government on his death in 1902. It was then neglected until 1911, when Harold Pearson, professor of botany at Cape Town College, came across it while searching for a site for a botanic gardens. The government accepted his recommendation, and the garden was founded in 1913. It was a huge task, preparing a vast run-down, weed- and pig-infested neglected farm with many exotic plantations, but labour was cheap... 

Pearson was an expert on cycads, and his collections formed the basis of the excellent living collection now in Kirstenbosch.
Part of the Kirstenbosch cycad garden - and yes, that is a pterosaur that you see! They are making the twin points that
cycads are indeed very ancient plants, and that many species of cycads (including most African ones) are faced with
extinction such as befell the dinosaurs, though the cycads' plight is mostly associated with human activity,
Pearson died in 1916 aged only 46, and three years later, at the conclusion of his war service, Professor Robert Compton took his place. For 34 years until 1953 he held the posts of both director of the gardens and professor of botany at Cape Town University (which is on the nearby slopes of Table Mountain). He was a visionary and a very hard worker. He began the gardens herbarium in 1939 with 18 cabinets; when he retired just 14 years later the 60,000 specimens (of which Compton contributed 35,000) filled 119 cabinets. Today there are 750,000 specimens, of 12,000 plant species, comprising the second-largest herbarium in southern Africa. Compton described more than 200 plant species in his life and more than 20 others are named (by others) for him. (When he retired he moved to Swaziland - now Eswatini - and carried out a national botanical survey for the government. His Flora of Swaziland appeared in 1976 when was 90. He died in Cape Town in 1979, aged 93.)

But once again, back to the gardens! Perhaps for the rest a stroll through the gardens might be the best way to introduce them.

The somewhat hazy view out over the sprawling Cape Flats suburbs to the towering Hottentots' Holland mountains.
I mentioned that our wildlife experience this time was relatively limited (partly due to conditions, but mostly our fault, as it was our first morning in South Africa and we got a late start). However there is always something there. I have read that since dogs were banned from the gardens in the mid 2000s  wildlife watching has greatly improved.
Two handsome birds that are readily seen in Kirstenbosch - as they are throughout South Africa,
and indeed through most of the continent.
Egyptian Goose Alopochen aegyptiaca above and Helmeted Guineafowl Numida meleagris below.

The often confiding African Dusky Flycatcher Muscicapa adusta isn't quite so familiar, though it occurs
across the southern coast of South Africa and scattered through mid-eastern Africa to the Red Sea,
including in well-vegetated gardens.
Others are a bit more restricted. Kirstenbosch is an excellent place for close views of the often shy Cape Spurfowl (or Francolin) Pternistis capensis, which is limited to the south-west of South Africa, plus a population along the Orange River on the Namibian Border.
The Kirstenbosch Cape Spurfowl are entirely accustomed to gawking visitors.
And who wouldn't gawk at that lovely subtly patterned plumage?
We also saw a Cape (or Small) Grey Mongoose Galerella pulverulenta hunting in the garden beds while we had lunch, and we read that Cape Clawless Otters Aonyx capensis still occur in the gardens, though scarce and shy. This is the nearest we got to them however.
It's a lovely sculpture and when first encountered certainly brings you up short for a moment!
This very African shelter built, like the retaining walls, steps etc, from local stone,
is typical of the tasteful infrastructure.
One addition since my last visit in 2005 is the lovely sinuous 130 metre canopy walk, called the Boomslang for the highly venomous arboreal snake which its curves are supposed to resemble.
And from this perspective the snake allusion is not at all hard to understand.
Looking along the boomslang.

The view of the forest - well-established plantings - from the canopy walk.
We ended our memorable visit with a very pleasant low key lunch on the verandah of the cafe.
Approaching the cafe from one of  many the garden paths.
But ultimately of course a botanic gardens is about plants, so let's end with some African plants featured at Kirstenbosch. Unfortunately not many of the Proteas or Ericas, quintessential South African heathland genera, were flowering at that time.

Silver Tree Leucadendron argenteum a highly endangered (and lovely) species, found naturally only
on the slopes of Table Mountain.
(There are a couple of other populations near Cape Town, but their status as natural populations is very questionable.)
A Kirstenbosch Silver Tree with its natural home behind it. Suburban development, clearing
for pine and eucalypt plantations and inappropriate fire regimes are the basic causes of its plight.
King Protea P. cynaroides, South Africa's floral emblem. It was just starting to flower and sadly not
attracting any sunbirds or sugarbirds while we were in attendance.
Unlike the Silver Tree (in the same family) it is found right across the south of the country.
Strelitzia juncea, one of the bird-of-paradise flowers, among the most widely recognised and grown
South African plants outside of its home. One of five similar species in the small family Strelitziaceae,
this one is perhaps not the one mostly grown as it occurs naturally only sparsely, in the vicinity of Port Elizabeth.
Another familiar South African export, one of the 70 or so species of red hot pokers, Kniphofia linearifolia.All are African, most are South African; this one grows as far north as Malawi.
Like the next two plants, this one is in the large lily family Asphodelaceae.
Candalabra Aloe A. arborescens, a magnificent big lily that grows in rocky areas
from eastern South Africa north to Malawi.
Bulbine frutescens, a genus familiar to people from my part of the world, though there are
only a few species here, compared with many in southern Africa.
African Mahogany Khaya anthotheca Family Melicaceae is not related to the Asian mahoganies, but is in the
same family as the Australian 'cedars'. The story is widely put about that the genus name came from a
misunderstanding when 'a botanist' asked his guide 'somewhere in Africa' what it was and got the response
'khaya' which purportedly means 'I don't know'. Some more detail - ie the botanist's name, the place and language,
and an explanation as to how he was working with a guide with whom he couldn't communicate - might lend
a little more credibility to the tale. Lovely tree though! It is found widely in central African forests
and in plantations in Africa and beyond.

Mountain Cypress Widdringtonia nodiflora Family Cupressaceae, a conifer found on mountains
in southern Africa, including Table Mountain.
Confetti Bush Coleonema pulchellum, Family Rutaceae. A South African endemic, I understand
that it has become naturalised in Victoria, but I've not knowingly seen it there. It's pretty spectacular in flower!
Restio sp., Family Restionaceae. We are familiar with rush-like Restios in Australia, but
it is now agreed that Restio is solely an African genus, and ours have been renamed.
The ones I know here are very modest indeed compared with this magnificent giant.
Plants such as this one form important habitat for quite a few South African birds.
And lastly a display of lovely daisies for which I don't have names. That doesn't interfere
with our enjoyment of them though.
If you can, you should certainly consider going to South Africa. And if you do, don't just go to the east of the country, though Kruger NP is a must - the Western Cape is well worth a visit too, not least for fabulous Kirstenbosch.

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