Trimming the Phylogenetic Tree

One of the main objectives of the Endangered Species Act of 1973, a powerful legislative driver of ecological conservation efforts, is to prevent organisms defined by specific genotypes from going extinct. An assumption of this act is that species with small isolated populations are likely to go extinct, but the reverse of this is often forgotten; many only recently speciated organisms also form small populations in isolated ranges. An international team of researchers (T Jonathan Davies et al. 2011) analyzed the genetic data of plant species in the United Kingdom and South Africa, and compared how the population size of species related to their time since speciating. The results show the range of “extinction hot spots” more significantly correlates with range of plant Lineages that have most recently diversified, than with the habitats directly influenced by human development. This means that, at least for plant species, small populations (ones that may be listed as endangered) may be more of a result of natural selection filtering out subprime genotypes than human degradation of the environment. Since the genetic data of this study was limited to an incomplete flora sample of the United Kingdom and South Africa it should not be assumed true for other parts of the world, but can serve to remind us that the loss of genetic traits is fundamental to natural selection.