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DNA barcoding will often fail to discover new animal species over broad parameter space
Michael J Hickerson1, Christopher P Meyer, Craig Moritz
1Museum of Vertebrate Zoology, University of California, Berkeley, CA 94720-3160, USA. mhick@berkeley.edu
Systematic Biology
|October 25, 2006
Summary
Using mitochondrial DNA (mtDNA) for species discovery has limitations. Thresholds like reciprocal monophyly and the 10x rule often fail to identify reproductively isolated lineages, especially in recent divergences.
Area of Science:
- Evolutionary Biology
- Genetics
- Speciation Research
Background:
- Mitochondrial DNA (mtDNA) divergence is increasingly proposed as a primary method for animal species discovery.
- Two common thresholds for species discovery are reciprocal monophyly and the '10x rule' (10 times greater genetic divergence between than within species).
Purpose of the Study:
- To quantitatively assess the utility of proposed single-gene divergence thresholds for species discovery.
- To investigate the reliability of these thresholds in identifying reproductively isolated lineages using coalescent theory and speciation models.
Main Methods:
- Coupling neutral coalescent theory with the Bateson-Dobzhansky-Muller (BDM) model of speciation.
- Simulating joint stochastic dynamics of genetic divergence and reproductive isolation under varying conditions.
- Corroborating simulation results with six empirical data sets.
Main Results:
- Both reciprocal monophyly and the 10x rule thresholds frequently fail to "discover" reproductively isolated lineages, particularly under models with divergent selection.
- Acceptable error rates (<10%) were only achieved in simulations after > 4 million generations of population isolation.
- High error rates in simulations were consistent with empirical data, indicating limitations in current single-gene approaches.
Conclusions:
- Single-gene, high-throughput species discovery methods may introduce significant bias in biodiversity surveys, potentially missing recently diverged lineages.
- These methods can misrepresent the relationship between isolated populations and actual species, especially when reproductive isolation mechanisms accelerate divergence.
- Relying solely on these genetic thresholds can lead to an inaccurate understanding of evolutionary history and biodiversity.
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