Limits...
Bias and sensitivity in the placement of fossil taxa resulting from interpretations of missing data.

Sansom RS - Syst. Biol. (2014)

Bottom Line: The opposite threshold in empirical fossil taxa is also found to be low; two absent entries replaced with presences causes fossil taxa to drift up trees.This observed sensitivity to coding non-present morphology presents a problem for all evolutionary studies that attempt to use fossils to reconstruct rates of evolution or unlock sequences of morphological change.Absent characters therefore require explicit justification and taphonomic frameworks to support their interpretation.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK robert.sansom@manchester.ac.uk.

Show MeSH

Related in: MedlinePlus

Distribution of linear fit coefficients for percent missing data against average taxon shift for data sets (40 simulated data sets, 5 empirical data sets, and 4 extinct only data sets).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4380037&req=5

Figure 3: Distribution of linear fit coefficients for percent missing data against average taxon shift for data sets (40 simulated data sets, 5 empirical data sets, and 4 extinct only data sets).

Mentions: The introduction of random missing data to simulated taxa (replacing 0s and 1s with ?s) fits the expected hypothesis: individual taxa drift up or down a tree with equal probability, relative to their original position and the root. As more missing data are introduced to a taxon, more noise is introduced and the magnitude of drift from the original position is greater, but these shifts are symmetrical on a gross level (Fig. 2). This balance of drift up and down is statistically supported (linear fit coefficients with zero intercept for percent missing data against average taxon shift for each simulated data set do not differ significantly from zero; one sample -test , ; Fig. 3). The same pattern was observed for empirical taxa from published morphological data sets (Fig. 2), which fall well within the range of simulated data (two sample -test for empirical and simulated coefficients ; Fig. 3).


Bias and sensitivity in the placement of fossil taxa resulting from interpretations of missing data.

Sansom RS - Syst. Biol. (2014)

Distribution of linear fit coefficients for percent missing data against average taxon shift for data sets (40 simulated data sets, 5 empirical data sets, and 4 extinct only data sets).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4380037&req=5

Figure 3: Distribution of linear fit coefficients for percent missing data against average taxon shift for data sets (40 simulated data sets, 5 empirical data sets, and 4 extinct only data sets).
Mentions: The introduction of random missing data to simulated taxa (replacing 0s and 1s with ?s) fits the expected hypothesis: individual taxa drift up or down a tree with equal probability, relative to their original position and the root. As more missing data are introduced to a taxon, more noise is introduced and the magnitude of drift from the original position is greater, but these shifts are symmetrical on a gross level (Fig. 2). This balance of drift up and down is statistically supported (linear fit coefficients with zero intercept for percent missing data against average taxon shift for each simulated data set do not differ significantly from zero; one sample -test , ; Fig. 3). The same pattern was observed for empirical taxa from published morphological data sets (Fig. 2), which fall well within the range of simulated data (two sample -test for empirical and simulated coefficients ; Fig. 3).

Bottom Line: The opposite threshold in empirical fossil taxa is also found to be low; two absent entries replaced with presences causes fossil taxa to drift up trees.This observed sensitivity to coding non-present morphology presents a problem for all evolutionary studies that attempt to use fossils to reconstruct rates of evolution or unlock sequences of morphological change.Absent characters therefore require explicit justification and taphonomic frameworks to support their interpretation.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK robert.sansom@manchester.ac.uk.

Show MeSH
Related in: MedlinePlus