HERE'S something interesting, which I heard on PM last week. The Bastard Gumwood (Commidendrum rotundifolium) is a 12 foot tall tree with long, knarled branches, at the tips of which are star-like, pale yellow and white flowerings. As a species, there is no variation from these characteristics, because there's only one of them. As such, it is declared extinct in the wild. Now, conservationists from Kew Gardens are making a last-ditch effort to rescue it from extinction.
John Ekwall's St Helena flora profile
You might imagine that conserving a species from just one specimen would be difficult, and you would be correct. Added to the complexity of the task is that the single tree lives on St Helena, a remote British-owned island in the south Atlantic, famed for being the location of Napoleon Bonaparte's imprisonment. Owing to its isolation, the island has 49 endemic floral species, including 13 species of fern, but it might once have had many more. When the British moved in in 1659, they destroyed the native forests, which had already been damaged by the introduction of goats by the Portugeuse in 1502. Now, Phil Lambdon of Kew Gardens and Jamie Roberts of the St Helena National Trust are working to preserve this final specimen.
Flowering plants contain a system of self-incompatibility, which prevents self-fertilisation. The last thing that you want is for pollen from an anther to blow off straight on to the stigma of the same plant, so a genetic barrier is present to halt the process of pollen tube growth, ovule fertilization and embryo development. Often, this occurs by the expression of genes in what is called an S locus. Both ovules and pollen from the same flower will contain the same S genes. When these are translated into S proteins, the proteins are identical, and cancel each other out, thereby blocking the development of a new plant. Pollen from a different plant will have a slightly different set of S genes (strictly, a different S haplotype), and thereby S proteins, allowing development to occur. It's a little more complicated than this, but in essence matching S haplotypes (say, S1 and S1) antagonise one another. Naturally therefore, the Bastard Gumwood stubbornly refuses to reproduce, except by cross-pollination with neighbouring False Gumwoods, but such hybridisation creates new, hybrid species and therefore doesn't preserve the Bastard Gumwood in its entireity.
So, the conservationists are having to do things the hard way. They've put a protective muslin netting around it to stave off any potentially cross-pollinating insects, and every day collect pollen from each flower with a paintbrush. This they use to attempt to pollinate a different flower on the same tree.
They hope that they will find a pollen grain that contains a mutation in the S locus that makes it sufficiently different to allow fertilisation, and thereby induce plant reproduction. But these mutations are so rare - they are working to a predicted rate of 1 pollen grain in 10,000 - that the work will take a long time indeed. Then, every single seed created must be planted and nurtured, in the hope that it is fertile.
This is not the first time this gumwood has been on the brink. It was thought to be extinct between 1870 and 1980, until Stedson Stroud stumbled across a final specimen in 1982. That tree was said to have died in 1986, so quite where today's tree came from does not seem to be recorded. Nonetheless, the painstaking effort of these scientists and their other team members is tremendously admirable and I hope they succeed.