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Discovering plant diversity – are we up to speed?

New plant species and even genera are discovered at a startling rate. Assistant Keeper of the Herbarium, Bill Baker, describes the discovery of three new palm genera and reflects on the need to accelerate the taxonomic process.
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Bill Baker

The discovery of a new species is one of the greatest thrills of the life botanical. Botanists can often be heard telling adventurous tales of the first time they clapped eyes on something new, while hanging off a cliff, wallowing in a swamp or swinging from a tree (delete as applicable). In my case, it happened in the Nepalese Himalayas on an undergraduate expedition shortly after my 20th birthday. Descending from a high ridge, drenched and decaying after days of solid rain, we stumbled upon some curious hardy gingers (Roscoea) with the “wrong”-coloured flowers. With the help of a dog-eared photocopy of a taxonomic paper published at Kew, we soon realised the plants were new to science. I recall the intense excitement of it all and the adrenaline-fuelled sleepless nights. The thought that we had found something that even those experts at Kew had never seen was almost unbearably exhilarating.

In fact, the discovery of new species continues apace today. The International Plant Names Index, jointly led by Kew, tells us that more than 2000 new species of vascular plants have been described every year over the past decade, each one a new branch of the Tree of Life brought to light. It is extraordinary to think that there is still so much we don’t about the living world, even in relatively conspicuous groups such as plants. The knowledge deficit is orders of magnitude greater for less conspicuous groups, such as fungi or invertebrates.            

New genera – the process of discovery

Even more surprising is the fact that around 200 new genera are described every year. The genus (plural: genera) is the taxonomic unit (or rank) above the level of the species, each genus containing one or more species united by shared features. While discovering and describing new species is routine business for active botanists, finding a new genus is a much more momentous event, often met with consternation and questioning – surely botanists must know all the plant genera by now? We probably do know the majority of plant genera, but as our methods become more sophisticated and our search for unknown plant diversity better targeted, we become more efficient at unveiling the plant kingdom’s remaining hidden secrets.

Take my own specialism, the palms (Arecaceae or Palmae), as an example — in 2008, we published Genera Palmarum, an encyclopaedic account of all palm genera that drew together all the latest research into a brand new classification. We recognised 183 known genera, and yet within just six years, that number has risen to 188. Major lineages of the palm evolutionary tree are still revealing themselves, despite our best efforts to provide a comprehensive research tool for palms, such as Genera Palmarum. However, it is precisely because we have such a resource, though, that we are able to go on and discover more.

New genera typically come to light in two different ways, either as discoveries in the field or the lab. The palm genus Tahina, described just in time for inclusion in Genera Palmarum, is a classic field discovery. This massive fan-leaved palm somehow escaped scientific attention in a remote corner of western Madagascar until 2006. Its morphological distinctness alone provided a sufficient case for erecting a new genus. In contrast, Dransfieldia, another new palm genus that I published with collaborators in 2006, was very much a lab discovery. This palm was originally discovered by the great Italian botanist Odoardo Beccari in 1872, but he and palm botanists after him placed the species in no less than three different genera. It was not until we analysed DNA sequences that we realised it did not belong to any of these three genera and needed a genus of its own. This in turn helped us better understand its anomalous morphology, which had confused so many previous experts.

Three new palm genera from Indonesia

In August 2014, an unprecedented rash of new palm genera was published as a result of a combination of both field and lab discovery. Over many years, my colleagues Charlie Heatubun (University of Papua), Scott Zona (Florida International University) and I have studied the palms of New Guinea and nearby islands. We frequently find new species, but three new palms first collected in 1998, 2006 and 2011 presented us with a serious problem. We simply did not know which genera to describe them in. We made a stab at describing two of them, using preliminary evidence from morphology and DNA, but made no progress on the third. In stepped French PhD student, Elodie Alapetite (Université Paris Sud), who painstakingly analysed DNA sequences of eight different genes.

Elodie’s data left us with a hard choice. Option one was to combine (or “sink”) our three new palms with four existing genera, many of which are important landscape and garden plants. Though a simple solution, this would be unhelpful to the users of our taxonomy (imagine the objections of the gardeners!) and would result in a genus that was impossible to define morphologically. Option two was to recognise each of our mystery palms as a separate new genus. This proliferation of small genera can be unpopular with some botanists, but we viewed this as the right course of action as it minimised destabilising taxonomic change and because the three new palms can be readily distinguished from other genera. 

Thus, the genera JailoloaManjekia and Wallaceodoxa were born. Jailoloa, is a slender upland heath forest palm from Halmahera in the Moluccas, and is named using a traditional word for its island home, Jailolo or Gilolo. Manjekia was coined using the local name (Manjek) for this species on its native island of Biak, and is a stately palm of lowland limestone forest with pendulous leaves. Wallaceodoxa, a 30m tree from the Raja Ampat Islands off the western end of New Guinea, honours Alfred Russel Wallace, the great Victorian naturalist and co-discoverer with Darwin of the theory of evolution by natural selection, whose centenary we celebrated last year. Wallace visited the Raja Ampat Islands in 1860 during his epic tour of the Malay Archipelago, but he was also an admirer of palms and author of the very first palm field guide, drawing on his experiences in the Amazon.

Too little, too late?

All three genera are threatened with extinction. Critically endangered Jailoloa, for example, grows in a single site in a nickel-mining concession. 

But the twist in the tale belongs to Wallaceodoxa; in the years we spent worrying away at the generic placement of this palm, diligently collecting DNA data to satisfy the critical minds of our peers, the largest wild population of around 50 adults and many offspring in 2006, was reduced to just 28 adults with no juveniles in 2011 because of habitat destruction. For as long as a species remains undescribed, it is out of sight of decision makers and cannot be protected. Have we failed Wallaceodoxa by missing the window for its conservation? Only time will tell.

The taxonomic process has an illustrious history with many time-honoured conventions, but, as the case of Wallaceodoxa shows, it still works too slowly. As a community, we taxonomists must find new ways to expedite the unlocking of biodiversity, embracing new methods to accelerate the process, such as eTaxonomy, turbotaxonomy and DNA barcoding. Kew and its sister institutions around the world are stepping up to this challenge, but there is no time to lose. If we fail, lack of time and resources for describing new discoveries will join the ever-growing list of factors driving species to extinction. I for one do not want that on my conscience.

- Bill -


References

Alapetite, E., Baker, W.J. & Nadot, S. (2014). Evolution of stamen number in Ptychospermatinae (Arecaceae): Insights from a new molecular phylogeny of the subtribe. Molecular Phylogenetics and Evolution 76: 227-240. Available online

Baker, W.J. & Heatubun, C.D. (2012). New palms from Biak and Supiori, western New Guinea. Palms 56: 131–150. 

Baker, W.J., Zona, S., Heatubun, C.D., Lewis, C.E., Maturbongs, R.A., Norup, M.V. (2006). Dransfieldia (Arecaceae) - A new palm genus from western New Guinea. Systematic Botany 31: 61–69. Available online

Dransfield, J., Rakotoarinivo, M., Baker, W.J., Bayton, R.P., Fisher, J.B., Horn, J.W., Leroy, B. & Metz, X. (2008). A new coryphoid palm genus from Madagascar. Botanical Journal of the Linnean Society 156: 79–91. Available online

Dransfield, J., Uhl, N.W., Asmussen, C.B.,  Baker, W.J., Harley, M.M. &  Lewis, C.E. (2008). Genera Palmarum – the evolution and classification of palms. Royal Botanic Gardens, Kew, 732 pp.

Heatubun, C.D., Zona, S. & Baker, W.J. (2014). Three new genera of arecoid palm (Arecaceae) from eastern Malesia. Kew Bulletin 69: 9525. Available online