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Proc Biol Sci. 2009 Nov 7;276(1674):3753-7. doi: 10.1098/rspb.2009.1004. Epub 2009 Aug 5.

The smallest avian genomes are found in hummingbirds.

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  • 1Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada. rgregory@uoguelph.ca

Abstract

It has often been suggested that the genome sizes of birds are constrained relative to other tetrapods owing to the high metabolic demands of powered flight and the link between nuclear DNA content and red blood cell size. This hypothesis predicts that hummingbirds, which engage in energy-intensive hovering flight, will display especially constrained genomes even relative to other birds. We report genome size measurements for 37 species of hummingbirds that confirm this prediction. Our results suggest that genome size was reduced before the divergence of extant hummingbird lineages, and that only minimal additional reduction occurred during hummingbird diversification. Unlike in some other avian taxa, the small amount of variation observed within hummingbirds is not explained by variation in respiratory and flight-related parameters. Unexpectedly, genome size appears to have increased in four unrelated hummingbird species whose distributions are centred on humid forests of the upper-tropical elevational zone on the eastern slope of the Andes. This suggests that the secondary expansion of the genome may have been mediated by biogeographical and demographic effects.

PMID:
19656792
PMCID:
PMC2817281
DOI:
10.1098/rspb.2009.1004
[PubMed - indexed for MEDLINE]
Free PMC Article
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