Interpretation of bootstrap values in phylogenetic analysis.
Bootstrap Analysis is a common tool in cladistics, and consequently many authors tend to believe that it could be close to a test of monophyly. In fact, it is only a procedure to calculate the redundancy of a certain character pattern among taxa. To demonstrate this, we set up a study with questionable data: Four skulls of great apes and humans were digitally photographed, and the pixels' brightness values were simply transformed to a one-zero-matrix, which was then used to calculate a Wagner tree with PHYLIP. As a rule, the higher the resolution of the photos is, the higher are the bootstrap values of supported taxa (and the lower are the bootstrap values of non-supported data). Redundancy of intertaxic information might indeed be an indicator of phylogenetic relationship, but can also be due to other reasons, like functional-adaptive needs in morphology, or semantic needs in a DNA-code. As a result, we tend to believe that high bootstrap values are actually less important than low ones. It is safer, based on a low bootstrap value, to claim that a certain taxon is not well supported by certain data. Therefore, we recommend discussions of low bootstrap values in future publications.
Wiesemüller
Bernhard
B
Institut für Zoologie, Anthropologie und Entwicklungsbiologie der Universität Göttingen.
Rothe
Hartmut
H
D000818:Animals; D005075:Biological Evolution; D006071:Gorilla gorilla / Q000033:anatomy & histology / Q000145:classification / Q000235:genetics; D015186:Hominidae / Q000033:anatomy & histology* / Q000145:classification* / Q000235:genetics; D006801:Humans; D008297:Male; D002679:Pan troglodytes / Q000033:anatomy & histology / Q000145:classification / Q000235:genetics; D010802:Phylogeny; D011148:Pongo pygmaeus / Q000033:anatomy & histology / Q000145:classification / Q000235:genetics; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D012815:Signal Processing, Computer-Assisted; D012886:Skull / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*