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Does hybridization increase evolutionary rate? Data from the 28S-rDNA D8 domain in echinoderms
Anne Chenuil1, Emilie Egea, Caroline Rocher
1Laboratoire DIMAR, diversité, évolution, écologie fonctionnelle marine, CNRS UMR6540, Université Aix-Marseille II, Université de la Méditerranée, Marseille, France. chenuil@univmed.fr
Journal of Molecular Evolution
|October 25, 2008
Summary
The large ribosomal RNA D8 domain in echinoderms shows a common structure but significant variation, particularly in the D8a region. This variation, influenced by selection and potentially hybridization, impacts evolutionary rates.
Area of Science:
- Evolutionary Biology
- Molecular Biology
- Genetics
Background:
- The divergent domain D8 of large ribosomal RNA is known for its variability in vertebrates.
- Echinoderms, as nonvertebrate deuterostomes, offer a unique system to study D8 evolution outside of vertebrates.
Purpose of the Study:
- To conduct the first comparative analysis of the D8 domain in nonvertebrate deuterostomes, specifically 31 species of echinoderms.
- To investigate the secondary structure, variation patterns, and evolutionary rates of the D8 domain in echinoderms.
- To explore the potential impact of hybridization on D8 evolutionary rates.
Main Methods:
- Comparative analysis of D8 sequences from 31 echinoderm species.
- Sequencing of 16S mitochondrial DNA in sea urchin taxa.
- Analysis of single-strand conformation polymorphism (SSCP) of D8 in Echinocardium cordatum populations.
Main Results:
- A common secondary structure for echinoderm D8 was inferred, supported by compensatory substitutions and indels.
- Variation in D8 primarily occurs at the tip of the D8a stem; more variable taxa exhibit longer, more stable D8 structures.
- Extreme variations in D8 evolutionary rates were observed in certain sea urchin taxa, correlating with reported interspecific hybridization.
Conclusions:
- Selection appears to maintain D8 stability within a specific range, rather than maximizing it.
- Hybridization may influence nuclear gene evolutionary rates relative to mitochondrial genes through processes like gene silencing or concerted evolution.
- The study highlights significant evolutionary dynamics of the ribosomal RNA D8 domain in echinoderms, particularly in relation to hybridization events.
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