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Standard percent DNA sequence difference for insects does not predict species boundaries
1Department of Entomology, Michigan State University, East Lansing, MI 48824, USA. cognato@msu.edu
Journal of Economic Entomology
|August 30, 2006
Summary
A standard DNA sequence divergence threshold cannot reliably identify species boundaries in economically important insects. Overlapping genetic divergences and nonmonophyly indicate a need for advanced phylogenetic analysis for accurate species delimitation.
Area of Science:
- * Molecular Systematics
- * Insect Taxonomy
- * Population Genetics
Background:
- * Distinguishing species boundaries in economically important insects is challenging due to limited morphological and biological data.
- * DNA sequence divergence is frequently used to infer species status, with non-overlapping intra- and interspecific divergences often cited as evidence.
- * A standardized DNA divergence threshold could simplify species identification where status is uncertain.
Purpose of the Study:
- * To review and assess the utility of a standardized percent DNA sequence divergence for predicting species boundaries in economically important insects.
- * To determine if a universal DNA divergence threshold accurately delineates species across diverse insect taxa.
Main Methods:
- * Compilation and analysis of 62 comparisons of intra- and interspecific pairwise DNA differences from mitochondrial and nuclear loci.
- * Inclusion of data from multiple insect orders: Isoptera, Phthiraptera, Hemiptera, Coleoptera, Lepidoptera, Diptera, and Hymenoptera.
- * Statistical assessment of the overlap between intra- and interspecific sequence divergence ranges.
Main Results:
- * Intra- and interspecific sequence divergences exhibited wide variation (0.04–26.0% and 1.0–30.7%, respectively) across studied insect groups.
- * Overlap between intra- and interspecific divergences occurred in 28 of 62 comparisons (45%), indicating a failure of standardized thresholds.
- * Nonmonophyly in closely related species was common and significantly associated with the overlap in genetic divergences.
Conclusions:
- * A standard percent DNA sequence divergence is unreliable for predicting species boundaries in economically important insects.
- * The observed overlap and nonmonophyly highlight the complexity of species delimitation using simple divergence metrics.
- * Accurate species boundary determination necessitates nonphenetic phylogenetic analyses and expert systematic review of DNA data.
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