White Beech: The Rainforest Years

by Greer, Germaine

  Macadamias were one of the first trees I could identify at Cave Creek. I was excited at first, not because Macadamias are now the world’s favourite and most expensive nuts, but because Macadamia trees were becoming rare in the wild. Since then they have become even rarer. The latest (2010) research by the World Wildlife Fund Australia and the Spatial Ecology Laboratory at the University of Queensland found only 3,000 wild trees surviving in their native habitat.

  So first I was thrilled and then I got worried. Maybe the people who had tried to make a living at Cave Creek had imported some of the new improved cultivars and maybe it was their progeny I could see growing along the creek and up in the high forest. If that had been the case I would have had to think of removing them. I love everything about the Cave Creek Macadamias, their stiff geometric habit, the ruby glow of the young foliage, the long pink helical flower tassels that hang vertically, the clusters of fruit dangling on strings, the spherical nuts straining against their pointed follicles until they split, the piles of empty nutshells hidden in the forest, each with an immaculately machined hole through which the littlest rodents have been able to feast on carbs and fat and protein.

  Macadamias look like many of their Gondwanan relatives. If you have ever had the great pleasure of seeing Hakea victoria in her full flaming glory in Western Australia, you would recognise a family trait in the structure and leaf colouring of the juvenile Macadamias at Cave Creek. I really didn’t want to have to destroy them. Hoping against hope, I kept them in the planting lists, and the workforce propagated them, not particularly willingly, because they’d much rather grow the forest emergents that put on three metres of height in a year. The Macadamias were slow, and prickly to boot. But I loved them, we had millions of easily collected seeds, and so we kept propagating and planting them.

  Generally speaking, Australian common names are specific, but the names Queensland Nut and Bush Nut have been muddled ever since Allan Cunningham collected ‘a Queensland Bush Nut’ (which he identified as M. ternifolia) in 1828. In his report to Governor Darling Cunningham remarked, ‘independent of its highly ornamental habit and refreshing shade afforded by its densely leaved branches, its nuts are produced . . . in such abundance as to be ere long worthy the attention of the farmer.’ (McMinn, 93) It would be more than a hundred years before any Australian farmer would avail himself of the opportunity, even though a correspondent calling herself Pomona wrote to The Queenslander in 1876 to point out that ‘The Queensland nut is already in our gardens, and bearing fruits under conditions favourable to its permanent improvement.’ (Q, 16 December, 22)

  The specimen of the Queensland Nut Cunningham sent back to Kew in 1828 probably sank to the bottom of the vast mass of plant material arriving from all over the world, because it cannot now be traced. The species, or something like it, was collected again by Leichhardt in 1843, according to his note, in the ‘Bunya Bunya brush’ and sent to the Melbourne Herbarium. The area where he found it is now known to have been the Conondale Range. Mueller later wrote on the label ‘Dawson and Burnett Rivers’, which is simply wrong. Mueller collected the plant again himself in 1857, with Walter Hill, along ‘the Pine River of Moreton Bay’. The next year Mueller published his description in the Transactions of the Philosophical Institute of Victoria, placing it in a new genus which he called Macadamia, after Dr John Macadam, Honorary Secretary of the Institute. The type species name was ternifolia, three-leaved, and all the specimens preserved in the Economic Botany Collection at Kew still bear this name. Dr Macadam must have done something to annoy Mueller; two years later he described the Queensland Nut again and decided that it was a member of the south-east Asian proteaceous genus Helicia. Though Mueller was using the same material as he had for the earlier description he seems not to have recognised it and made no reference to his own earlier identification. It was Bentham, toiling away in England at his Flora, who saw that Mueller had been right the first time and resuscitated the genus Macadamia, using the grounds alleged by Mueller in his earlier publication.

  Nobody seems to have realised that the plants they were discussing produced palatable nuts of high nutritional value. Dutch botanist Maurits Greshoff, who examined the specimens at Kew, was convinced that Macadamia ternifolia was ‘among the most strongly cyanogenetic plants; in the fresh leaf the hydrocyanic content was more than 0.1 per cent’ (Kew Bulletin No. 10, 1909, 413). Perhaps what happened at Kew is that Greshoff was given immature kernels to study, possibly in a fermented state. This curious chain of accidents has given rise to the erroneous belief, cherished by American Macadamia growers, that there is a poisonous wild Macadamia species that has never been cultivated. This may have been the Gympie Nut, proteaceous, small-fruited and extremely bitter. It was not until 1897 that Maiden and Ernst Betche collected smooth-shelled Macadamias from Camden Haven, and suggested a new species, Macadamia integrifolia, so called because the leaves were less serrate than those of the type. Two years later they decided that they were wrong and reduced their separate species to a subspecies. ‘We found all degrees of transition between the two extreme forms and have been forced to the conclusion that it is merely another instance of the great variability of the Proteaceous trees . . .’ they explained (Maiden and Betche, 1897). Attempts to separate the entire-leaved Macadamias from the serrate-leaved Macadamias failed because single trees were capable of displaying both leaf forms at different stages in their development. There was one point of distinction between them which was not debated: the entire-leaved Macadamias grew only in Queensland (hence Queensland Nut), the serrate-leaved grew on both sides of the border (hence Bush Nut).

  In 1954, Lawrie Johnson came to the rescue: the confusion ‘has been due to several causes; firstly semi-juvenile stages of one species resemble the mature stage of the other species in the possession of toothed leaves; secondly two states of the first species have been described under two different names; and, thirdly, the second species has not been named at all’ (Johnson, 1954, 15). In fact Bentham had worked on specimens of both species, but Johnson was on the money. The name he suggested for the second species was Macadamia tetraphylla, and those are the Macadamias of the upper Nerang Valley. At least, I think they are. The CCRRS Macadamias are not reliably tetraphyllous; the first stem to appear above ground usually carries whorls of three leaves each, and continues to do so until the first fork; the growths above the fork will show whorls of four leaves – mostly. The leaves however are always serrate, but the flowers are not always pink but occasionally white or cream.

  By 1954 the phylogeny of the Macadamia was being obscured by the breeding and cross-breeding of selected strains by American horticulturists who recognised the nut’s commercial potential. The first Macadamia trees in Hawaii were planted as ornamentals in 1882 by William H. Purvis, manager of a cane plantation at Kapulena, who was an enthusiastic plant collector. Forty years later another American, Ernest Shelton van Tassell, tried to grow the nuts commercially, but the trees performed inconsistently, producing nuts of varying quality at varying intervals. The Agricultural Research Station of the University of Hawaii then stepped in. They recognised M. ternifolia as having almost sessile leaves in whorls of three or four with serrate and sometimes prickly margins; M. integrifolia was described as having spatulate leaves with a distinct petiole and entire margins. As cultivars were developed the two kinds resolved themselves into the rough-shelled type and the smooth-shelled type, with only the smooth-shelled type considered suitable for cultivation. As late as 1957 William B. Storey of the University of California, who described the genus as ‘possibly half a dozen species’, was still having difficulty separating them. In his version M. integrifolia was a subspecies of M. ternifolia. His account is remarkable because of its geographical detail.

  M. ternifolia occurs naturally only in south-eastern Queensland. Its range extends a distance of about 175 miles, from Beechmont on the south to Maryborough on 25°30' S. M. tetraphylla occurs naturally only at the south-eastern extremity of Queensland and the
north-eastern corner of New South Wales. Its range extends a distance of about 75 miles, from Mt. Tamborine on the north to Lismore on the south between the latitudinal limits of 28°S and 29°S. The ranges of the two species overlap for a distance of about 15 miles in the Guanabah and Tamborine Creek regions of southern Queensland. Types of trees intermediate in characteristics between the two species have been seen in the regions of overlapping ranges. These are thought to be interspecific hybrids. (334)

  This doesn’t quite make geographic sense but it does predict the variability that we have observed in the Cave Creek species. By 1970 Storey had accepted Maiden and Betche, and recognised M. integrifolia, but he thought it could be found in the Numinbah Valley. Maybe it can, but not at CCRRS. Perhaps botanists have had so much trouble distinguishing these species because in fact they are not distinct.

  Commercial production of improved cultivars in Hawaii got under way in the 1950s. The first country to import and grow Hawaiian cultivars was Guatemala, followed by Australia (Cheel and Morrison, 23). Australia now produces 37 per cent of the world’s Macadamia nuts, Hawaii 22 per cent. New varieties are produced every year, not only in Hawaii but in South Africa, New Zealand and Australia as well. The breeders’ aims are to produce strains that will crop heavily and drop their nuts easily, so that they can be harvested mechanically off the ground, and with thinner and more brittle shells so that the kernels are not damaged when the shells are removed. Nowadays the cultivars have numbers instead of names. No more than 2–3 per cent of the Macadamia nuts produced round the world end up being eaten as nuts; three-quarters of them are processed to go into cakes and biscuits, the rest into chocolates, ice cream – and cosmetics.

  We were back in Cambridge when the subject came up again. Jenny listened to me bumbling for as long as she could stand it and then grabbed the laptop.

  ‘Let’s get some answers here. How big’s the Macadamia gene pool? How many species in the genus?’

  ‘Two,’ I said confidently. Jenny did a spot of googling.

  ‘Wikipedia says there are nine species in the genus Macadamia.’

  ‘According to whom?’

  ‘It doesn’t say.’

  ‘Does he, she or it name them?’

  ‘Hm. Seven from eastern Australia, one from New Caledonia and one from Sulawesi.’

  ‘That’s easy. There was a group of proteaceous plants growing in north Queensland that got lumped in with the Macadamias but they’ve been lumped out again. The one from Sulawesi was Macadamia hildebrandii. They’ve all been relocated in the genus Lasjia.’ I pronounced it to rhyme with ‘mass jeer’.

  ‘Never heard of it.’

  ‘Me either. I’m not even sure how to say it. It’s a made-up name to honour the Australian expert on the Proteaceae, L. A. S. Johnson. Have a look at APNI.’

  APNI is the on-line Australian Plant Name Index. As Queensland has yet to publish a state Flora, and the 3-volume 1986 Flora of South-Eastern Queensland by T. E. Stanley and E. M. Ross is both out of date and out of print, we tend to consult APNI in the first instance.

  Jenny’s fingers skated over the mouse-pad.

  ‘Sure enough, five one-time Macadamias are now in the genus Lasjia: Macadamia claudiensis, M. whelanii, M. grandis, M. erecta, and M. hildebrandii.’ (She might have added four more: M. praealta is now Floydia praealta, M. youngiana Triunia youngiana, M. angustifolia Virotia angustifolia, M. heyana Catalepidia heyana.)

  ‘Cross-check with Tropicos.’

  ‘What’s that?’

  ‘The data base of the Missouri Botanical Garden.’

  Jenny did. I could hear her growling in her throat.

  ‘What a mess. Thirteen species listed and no sign that the taxonomy has been revised.’

  ‘That may be because they don’t accept the revision.’

  As a proper scientist who works on the pharmacology of brain function, Jenny was distinctly unimpressed with the mare’s nest that is botany.

  ‘The sooner they find an objective way of identifying plants the better. This is hopeless.’

  I couldn’t disagree, even though I would miss the barminess of the binomials once barcodes had taken their place. Given the bossiness of the Australian academic establishment, use of the binomials will probably be banned once a barcode system is adopted.

  The Tropicos list included four species that have now been classified as belonging to another new genus called Virotia, plus two of the five that are now Lasjia, and two mysteries, M. francii and M. alticola. ‘Macadamia alticola’ was first called that by René Paul Capuron, who found it 1,600 metres up in the forest of Ambohitantely on the island of Madagascar, where he had spent a good deal of his life studying the tree flora (Capuron, 370). When Lawrie Johnson and Barbara Briggs examined the type specimen, they soon realised that it was not a Macadamia but a new genus that they called Malagasia, after the island itself (Johnson and Briggs, 1975, 175).

  The more we foraged, the more Macadamias we found. All but four had been reidentified as something else.

  After some more rambling round the net, Jenny stood up and stretched.

  ‘I get it. Austin Mast at Florida State University got an award in 2005 to run a research programme with Peter Weston and Greg Jordan in Oz and David Cantrill in Sweden where they work on a phylogeny for the Grevilloideae section of the Proteaceae using nuclear and chloroplast gene sequencing. The idea was to track the breaking up of Gondwana by tracking the genetic relationships between members of the group. They published their results in December 2007. Apparently it went a bit pear-shaped.’

  She sat down again. ‘Listen to this:

  Ever since continental drift and plate tectonics displaced the stable earth model in geological theory, the Proteaceae have been generally regarded as a classic ‘Gondwanic Group’ – one that originated well before the fragmentation of the ancient supercontinent Gondwana, and which achieved its widespread distribution in the southern hemisphere as a result of vicariance.

  ‘Vicariance?’

  Jenny explained. ‘It’s the word they use for what happens when the range of a species is split and two different species evolve from a common ancestor. It’s only a theory. If it’s correct the distribution of taxonomic groups has been determined by ruptures in the range of ancestral species, by continental drift or an eruption or a flood. What our colleagues were trying to do was trace the splitting process by a phylogenetic examination of a group of Proteaceae. However’ – Jenny paused for dramatic effect –

  However, molecular dating analyses recently conducted by Dr Weston’s research group are suggesting that the first of these ideas is false and the second only partly true.

  ‘Then, what . . .?’ I stared at her. I’d just got my head round the Gondwana hypothesis and here it was disappearing like the Cheshire Cat, leaving only Jenny’s delighted grin behind.

  ‘Wait,’ she said. ‘There’s more.’

  Mast et al. (2008) published the results of a phylogenetic analysis and molecular dating of the most biogeographically interesting clade in the Proteaceae, the tribe Macadamieae—

  Jenny turned to me. ‘Which would be?’

  I had to ferret in my files for the answer. ‘The tribe is made up of four subtribes, the Macadamiinae, the Malagasiinae, the Virotiinae and the Gevuiinae.’ The Macadamiinae are three genera, Macadamia, Panopsis (from tropical America) and Brabejum (from the south-west Cape); the Malagasiinae two, Malagasia (from Madagascar) and Catalepidia (from Queensland); the Virotiinae three, Virotia (from New Caledonia), Athertonia (Queensland) and Heliciopsis (Burma to central Malesia); and the Gevuinae seven or eight, depending, Cardwellia (Queensland), Sleumerodendron (New Caledonia), Euplassa (tropical America), Gevuina (Chile and Argentina), Bleasdalea (western Pacific to eastern Australia), Hicksbeachia (up the road from Cave Creek), Kermadecia from New Caledonia and Turrillia (probably synonymous with Bleasdalea). OK?’

  Jenny turned back to the computer screen. ‘The analysis was based on DNA sequence data for seven nuclear
and chloroplast genes plus morphology. Are you with me?’

  I thought so. ‘Hang on tight,’ said Jen.

  Their results strongly suggest that at least 8 of the 9 clades in this tribe showing continental disjunctions are too young to have dispersed between the continents over land.

  ‘What?’ I was dumbfounded.

  ‘Hold on,’ said Jen.

  It suggests—

  ‘What suggests? That “it” has no antecedent.’

  ‘He’s a botanist. You can’t expect grammar.’

  It suggests instead that what is now the Australian craton is the centre of origin for this tribe and that the clades now found in tropical and temperate South America, New Caledonia, Fiji, Vanuatu, south-east Asia, Madagascar and southern Africa got there by long distance dispersal across significant ocean gaps. Moreover, the reconstructed dispersal events all post-date the onset of the circum-polar current and are significantly correlated with multiple evolutionary origins of indehiscent fruits, suggesting that the intact fruit wall has played a key role in protecting the seed from immersion in salt water.

  The suspicion that the commonly accepted version of the evolution of the Proteaceae was wrong had been around for years. Nigel Barker, who began working on the Proteaceae as a graduate student in South Africa, was granted a fellowship to work at the Royal Botanical Gardens in Sydney with Peter Weston in 1996 and formed his hypothesis then, but it was not until he met Frank Rutschmann, who was completing a Ph.D. at the Institute for Systematic Botany in Zurich, that he was able to avail himself of the newest computational expertise in molecular dating. Hervé Sauquet’s revision and reassessment of the fossil evidence completed the array of skills needed to calibrate the molecular clock as the mutation rate of the various DNA sequences they had assembled was established by comparison with that of the fossils. The genus Protea turned out to be genuinely Gondwanan but other of the fynbos genera were much younger and had closer Australian relatives (Barker, N., et al.).