Sometimes in taxonomy there are good solutions and not-so-good solutions to taxonomic conundrums. And sometimes it just takes a while to reach a good solution.
One such conundrum arose when careful molecular phylogenetic studies showed that the well-known and diverse Australian genus Hakea is nested inside the even better-known and even more diverse genus Grevillea. With this result, the trouble with grevilleas began.
Hakea and Grevillea were both named and described around the turn of the 19th Century, the former by the German botanists Heinrich Schrader and Johann Wendland in 1797, the latter by English botanists Joseph Knight, Richard Salisbury and Robert Brown in 1809. (In a curious case of history repeating itself, the publication of Grevillea was highly controversial at the time; we'll return to this later.)
Since that time, many species have been discovered and named in both genera, so that today there are nearly 150 species in Hakea and more than 350 in Grevillea. Grevillea is the third largest genus in Australia, after Acacia and Eucalyptus. New species are regularly discovered, especially in Grevillea.
Throughout their history, the differences between species of Hakea and those of Grevillea have been pretty clear. Hakea species all have thick, woody follicles (fruits) that persist on the plant for some time, protecting the seeds until a fire pops them open, while almost all species of Grevillea have thin-valved, leathery follicles that open without fire and are then shed after the seeds fall.
While this difference worked well for botanists for centuries, modern taxonomy has a more rigorous standard for recognising and naming genera and other taxa. More emphasis is now placed on evolutionary history and the evolutionary structure of life rather than on simple similarities and differences. In this modern view, a genus should comprise all and only the descendants of an original species. This makes sense - most people would expect that all species in Grevillea should be evolutionarily more closely related to each other than they are to species in Hakea.
Another way to say this is that genera in modern taxonomy should be whole branches of the tree of life, not partial branches that include some descendants but not others.
With the powerful insights offered by DNA sequencing and phylogenetics, Hakea and Grevillea have become problematic as genera. It turns out that Grevillea is a large branch on the tree of life, and Hakea is a sub-branch within it. That is, hakeas are simply grevilleas that have developed thicker follicles. (One other genus, the small New Guinea rainforest genus Finschia, is also a sub-branch of Grevillea.)
When this result was first confirmed in 2015, a number of possible taxonomic solutions were available to fix the problem. One solution would be to simply merge Hakea (and Finschia) into Grevillea, so that only the whole branch containing all species in all three genera is recognised as a genus.
If this were the case, the name Hakea would have priority (since it was published some 12 years before Grevillea, and a century before Finschia), so all Grevillea and Finschia species would need to be given new names in Hakea. An alternative solution would be to prune new genera out of Grevillea, ensuring that each genus comprises a whole sub-branch of the Hakea+Grevillea+Finschia branch. This would allow Hakea and Finschia to be retained, but would dismember the larger genus Grevillea.
Both these solutions are available to taxonomists; which is chosen depends on many factors, including convenience. If it were necessary to split Grevillea into a large number of small genera, and if these small genera would be hard to recognise, then merging into a single genus would be preferable. If, on the other hand, Grevillea could be conveniently split by pruning off a few readily recognisable new genera as a way to save Hakea and Finschia, this would be a preferable solution.
Unfortunately, the original 2015 paper that showed there is a problem had insufficient sampling of Grevillea species to point the way to a solution. More work was needed before Australian botanists could comfortably address the issue.
And this is where a controversy has arisen. In 2018, a group of European botanists working for a private botanical company, in a self-published volume of a planned global flora called GLOVAP, took the plunge and combined all species of Grevillea and Finschia into Hakea, publishing many hundreds of new combinations and new names to do so. One reason given was that progress to solve the problem, first identified in 2015, was too slow.
Done without consultation with the Australian botanists working towards a solution, this understandably caused a degree of outrage. The GLOVAP authors chose the easier option (sinking Grevillea and Finschia into Hakea), while Australian botanists were working towards the more difficult but ultimately less disruptive solution of splitting some new genera from Grevillea.
The result is a stand-off. While many of the new names published by the GLOVAP authors are valid under the International Code of Nomenclature for algae, fungi and plants, no Australian herbarium, nor the agreed Australian Plant Census, has taken them up. For the time being, the problem remains unresolved.
In a curious irony, the GLOVAP authors unwittingly repeated a rather sorry chapter in the history of Grevillea taxonomy, by effectively gazumping the Australian botanists working on Grevillea. Remember that Grevillea was named in 1809, in a publication by Joseph Knight called On the cultivation of the plants belonging to the natural order of Proteeae. It's now widely accepted that most of that publication, including the section where Grevillea was named, was written anonymously by Knight's friend and controversial botanist Richard Salisbury.
Salisbury effectively plagiarised a series of lectures given by Robert Brown, a noted expert on Australian plants. He had attended a series of lectures given by Brown at the Linnean Society, where Brown had read from his yet-unpublished work On the Proteaceae of Jussieu, including observations and discoveries amongst Australian Proteaceae. Salisbury apparently memorised Brown's plant names, and gazumped Brown by quickly going to print, in 1809 (Brown published in March 1810). Salisbury, via Knight, thus claimed priority for the names that Brown had authored.
For his troubles, Salisbury was effectively boycotted by most of the leading botanists of the day, and many of his names were ignored. Likewise, the merger of Grevillea into Hakea has been effectively ignored by Australian botanists, at least for the time being.
But, prepare for some name changes arising from all this. At the moment it appears that both Grevillea and Hakea can be retained by segregating a few small genera from the former. Once this change is made, the taxonomy of these two closely related genera should be stable, and more robust than it's been for over two centuries.