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Population differentiation decreases with depth in deep-sea bivalves
Ron J Etter1, Michael A Rex, Michael R Chase
1Biology Department, University of Massachusetts, Boston, Massachusetts 02125, USA. ron.etter@umb.edu
Evolution; International Journal of Organic Evolution
|September 13, 2005
Summary
Deep-sea bivalves show reduced genetic differentiation with increasing depth. The complex bathyal zone, not the abyss, may drive deep-sea species evolution.
Area of Science:
- Marine Biology
- Evolutionary Genetics
- Deep-Sea Ecology
Background:
- The deep sea, Earth's largest ecosystem, harbors diverse endemic fauna.
- Evolutionary processes driving deep-sea species richness remain poorly understood.
- Environmental factors like depth influence population differentiation.
Purpose of the Study:
- To investigate how depth affects population genetic structure in deep-sea protobranch bivalves.
- To test the hypothesis that population differentiation decreases with increasing depth.
- To understand evolutionary processes in the deep sea.
Main Methods:
- Mitochondrial DNA (16S rRNA gene) analysis of 268 individuals from four bivalve species.
- Sequencing and haplotype analysis.
- Population genetic statistics (phiST) and phylogenetic analyses (UPGMA, nested clade analysis).
Main Results:
- 45 haplotypes were identified across the four species.
- Sequence divergence shifted from inter- to intra-population with depth.
- Higher population structure (phiST) in upper bathyal species (0.755-0.931) than lower bathyal/abyssal species (0.071-0.045).
- Genetic distances and population divergence decreased with depth.
Conclusions:
- Deep-sea protobranch bivalve genetic structure parallels depth-related morphological divergence.
- The heterogeneous and complex bathyal zone likely promotes species formation.
- The bathyal zone, not the abyss, may be a key area for deep-sea evolutionary radiation.