A paper out in Nature 15 February, uses a novel technique devised by one of the authors, Dan Faith, called Phylogenetic Diversity (PD), to assess the biodiversity and conservation value of endangered species and regions in terms of how unique they are in evolutionary history.
The summary article says this:
When seeking to preserve biodiversity, simply trying to count and protect every species may not be enough. A new study suggests that conservationists should also consider the extent to which the mix of species in an area has the genetic potential to adapt to change.
In the past, many scientists assumed that the number of species in a region reflects that area's potential for evolutionary change. That potential is expressed in terms of "phylogenetic diversity"--a measure of how distantly related those species are. The higher the species number, the prevailing theory went, the higher the phylogenetic diversity, and the easier it would be for the area as a whole to adapt to global change.
When Félix Forest, Richard Grenyer, and colleagues at the Jodrell Laboratory of the Royal Botanic Gardens in Kew, U.K., and other research centers examined plant life in two biodiversity hot spots in South Africa's Cape region, however, they found that species number and phylogenetic diversity don't always go hand in hand. Analyzing sequence data from a gene present in 735 plant genera, the researchers found that while the western Cape had more plant species, the eastern Cape's flora had higher phylogenetic diversity. That diversity, in turn, had produced more plants with traits useful for food or medicine. The team presents its findings 15 February in Nature.
Actually, there's a bit of difference between the PD approach and genetic potential to adapt. PD simply measures how rare species are, phylogenetically, in a region. Sequence data here simply means that genetic sequences were used to construct the cladograms. This technique raises some interesting issues - why should we care about phylogenetic diversity? It's a record of what happened in the past, not the future. Genetic diversity may be an indication that existing groups will survive in the future, but PD seems not to relate much to that, the summary article notwithstanding.
I think the answer will depend very much on what we want biodiversity measures to measure (and this is something that I will be investigating, I hope in conjunction with Dan, in my grant). Do we value species that exist or species that may exist? Is what we want to conserve the situation that existed when we first encountered it ("wilderness") or whatever is left of that? Or shall we apply measures of "services", meaning what we can get out of a region (or what a region produces independently of us)? If the services view is taken seriously, then counter-intuitively, a simpler system may be better (that is, more efficient). If we want it to be resistant to environmental perturbation in the future, then that may mean we want to maximise both taxon richness and genetic richness. And so on.
I have no real opinion on this yet, except that I am fascinated by the conflicting goals and aims of conservation planning. From an evolutionary perspective, the current extinction pulse we have caused (there's really no doubt, you know) will end up resulting in an adaptive radiation down the track. But how far? 2 million years? 5? 10? If this is used as a justification for any conservation strategy, what is the payoff to us if we are likely extinct ourselves by then?
The authors note that "Conservation planning is not just about total numbers, but also about marginal gains." The question of qui bono (whose good?) out of law here is pretty important. Marginal gains for whom? Or, to put it another way, are the interests served in conservation those of the organisms, species or genetic types, or are they ours?
I'll let you know if I come up with anything...
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