(The following is the sixth part of a series of posts on an Annals of the Missouri Botanical Garden special issue on “Evolutionary Systematics and Paraphyly”. All posts in this series are tagged with “that special issue”.)
Following an introduction and the contributions of Lockhart et al., Hörandl, and George, the fifth full paper in the special issue is Stuessy et al.'s “Paraphyly and endemic genera of oceanic islands: Implications for conservation”.
The main argument is quickly summarised, and it has actually already been made before by the same author, only then in a considerably more concise manner (Hörandl & Stuessy, 2010). When new species arrive on oceanic islands via long distance dispersal, in the most extreme cases as a single seed or a single pregnant female, they may find themselves presented with many new possibilities. Some selection pressures from their original habitat may not exist on the island, and there may be unused niches ready for the taking. The new arrivals also undergo a severe genetic bottleneck, carrying only a small fraction of the genetic diversity of the mainland population in themselves.
This means that island colonisers often have the chance of undergoing spectacular adaptive radiations in a short time. Echium and Sonchus in the Canary Islands, fruit flies or the Silver Swords in Hawaii are just some examples. In the words of Stuessy et al.,
Because of the speed of the divergence, it might be that the island genera are genetically not so divergent from the continental relatives, but they are usually very divergent morphologically, hence their recognition at the generic level.
So because they looked superficially very distinctive after their adaptive radiation into new niches, island lineages were traditionally often treated as genera distinct from the mainland genera they evolved out of. With the advent of phylogenetic systematics, however, they are sunk into these mainland genera, so that these island lineages are not island-endemic genera any more; they are just the island's representatives of the widespread mainland genus.
So what? So, according to Stuessy et al., this:
these actions could have a substantial effect on world island conservation.
This is, as far as I can see, as explicit as the paper makes the argument for paraphyletic taxa, but it is still clear what this is about. The idea is undeniably that one should keep island endemic genera because they make a better sell for conservation politics than mere endemic species.