Nested Clade Phylogeographic Analysis (NCPA) ranks among the mostly widely used methods in the gene-genealogy based analysis of intraspecific phylogeography.
The method was originally described more than 13 years ago (
Templeton et al. 1995), and has by some accounts (e.g.,
Knowles 2008) been used over 1700 times.
Certainly, the original description of the method has been cited
over 600 times, a number that continues to grow (with 8 citations already reported for 2009 at the time of writing).
The method has also been described elsewhere, including in Alan Templeton’s
recent book.
The primary innovation of the method when introduced (as purported in Templeton et al. 1995 and Templeton 2006) is that by incorporating the temporal information of gene trees, the procedure extends our phylogeographic inference capabilities beyond the traditional
FSTs and
Nms of classical population genetics.
Nielsen and Beaumont (2009; pp. 1037-1038) provide a wonderfully succinct description of NCPA. Given a sample of haplotypes at a given genetic locus, the user first identifies an estimate of the haplotype network for the sample. He or she then hierarchically agglomerates sets of haplotypes separated by 1, 2, 3, . . ., etc. mutational steps. Next, the user calculates statistics describing the geographic dispersion within clades and between nested clades, and compares these statistics to those obtained by permuting geographical information among samples - retaining the distances from the clades with significant statistics for comparison to an inference key. Inferences liable to result from the procedure include such things as range expansion, long distance migration, and geographic fragmentation.
However, the method has received some pointed criticism as well, most notably from Lacey Knowles at the University of Michigan. Recently, Knowles and Templeton exchanged vitriolic attacks in the pages of the journal Evolution (Knowles 2008; Templeton 2009). Earlier, Knowles and Maddison (2002; maybe someone can tell me why the article, pp. 2623-2635, is missing from the online journal issue here) published a simulation study sharply critical of the method in Molecular Ecology, and Templeton (2004) responded in kind. Criticized shortcomings of the method include an exceedingly high type I error rate in simulation studies (estimated to be ~20% by Templeton 2008, but as high as 75% in other analyses), and subjectivity in the agglomeration of nested clades and in the application of the method's inference key. Other detailed critiques of NCPA can be found in Beaumont and Panchal (2008) and in Nielsen and Beaumont (2009) (the latter even includes a fascinating discussion of the 'Forer effect' as it might pertain to this method).
How do the readers of this blog perceive the current standing of NCPA? Furthermore, but on a much more philosophical note, how do readers view the kind of heated exchange partaken of by Knowles (2008) and Templeton (2009)? Is it true (to paraphrase A. N. Whitehead) that the clash of ideas is more of an opportunity than a calamity?
Note: For other fun exchanges in the recent literature among people I know, please check out: Downhower et al. (2009) and the response by Langerhans and Gifford (2009); or Bokma (2008), and the reply by Rabosky and Lovette (2008).
We at the AMNH have been adopting Geneious as well and after we recently purchased several copies, they donated licenses on our behalf to Diponegoro University in Indonesia, the International Centre of Insect Physiology in Kenya and the University of the Philippines Marine Science Institute, places which some of our postdocs have been collaborating. The press release that the company just released about this states that they have developed a general practice of providing discounts to researchers in low GDP countries to help promote bioinformatics around the world. Broader impacts included the box!
