Chloroplast capture explained

Chloroplast capture is an evolutionary process through which inter-species hybridization and subsequent backcrosses yield a plant with new genetic combination of nuclear and chloroplast genomes.^[1] For instance:

• 1) species A's (having chloroplast genome a and nuclear genome AA) pollen hybridizes to species B's (b and BB) ovule, yielding the 1st hybrid (F1) with chloroplast genome b and nuclear genome A (50%) and B (50%);
• 2) species A's pollen hybridizes (backcross) to F1's ovule, yielding the 2nd hybrid (F2) with chloroplast genome b and nuclear genome A (75%) and B (25%);
• 3) species A's pollen again backcrosses to F2's ovule, yielding the 3rd hybrid (F3) with chloroplast genome b and nuclear genome A (87.5%) and B (12.5%);
• 4) after further backcross generations, a plant is obtained with the new genetic combination (chloroplast genome b and nuclear genome AA).

Known cases of chloroplast capture

Gymnosperm

• Juniperus (Cupressaceae) ^[2]
• Pinus (Pinaceae) ^[3]

Angiosperm

• Quercus (Fagaceae) ^[4]
• Ruppia (Ruppiaceae) ^[5]
• Heuchera (Saxifragaceae) ^[6]

Notes and References

1. [Loren H. Rieseberg|Rieseberg. L. H.]
2. Terry RG, Nowak RS, Tausch (2000) Genetic variation in chloroplast and nuclear ribosomal DNA in Utah juniper (Juniperus osteosperma, Cupressaceae): evidence for interspecific gene flow. American Journal of Botany 87: 250-258
3. Matos, J. A. and B. A. Schaal. 2000. Chloroplast evolution in the Pinus montezumae complex: a coalescent approach to hybridization. Evolution 54: 1218–1233
4. Whittemore, A. T., Schaal, B. A. (1991) Interspecific gene flow in sympatric oaks. PNAS 88: 2540-2544
5. Ito, Y., T. Ohi-Toma, J. Murata, and Nr. Tanaka (2013) Comprehensive phylogenetic analyses of the Ruppia maritima complex focusing on taxa from the Mediterranean. Journal of Plant Research 126(6):753-62.
6. [Soltis, D. E.]