000			02511nab a22003257a 4500
003			EC-PaCDF
005			20171204141423.0
008			170725t20132013xxu|||||||||||||||||eng||
040			_aEC-PaCDF
041			_aeng
082	0	4	_221 _a597.9246
100	1		_aLoire, Etienne.
245	1	0	_aPopulation genomics of the endangered giant Galápagos tortoise.
520	0		_aBackground: The giant Galápagos tortoise, Chelonoidis nigra, is a large-sized terrestrial chelonian of high patrimonial interest. The species recently colonized a small continental archipelago, the Galápagos Islands, where it has been facing novel environmental conditions and limited resource availability. To explore the genomic consequences of this ecological shift, we analyze the transcriptomic variability of five individuals of C. nigra,andcompareittosimilar data obtained from several continental species of turtles. Results: Having clarified the timing of divergence in the Chelonoidis genus,wereportinC. nigra averylowlevelof genetic polymorphism, signatures of a weakened efficacy of purifying selection, and an elevated mutation load in coding and regulatory sequences. These results are consistent with the hypothesis of an extremely low long-term effective population size in this insular species. Functional evolutionary analyses reveal a reduced diversity of immunity genes in C. nigra, in line with the hypothesis of attenuated pathogen diversity in islands, and an increased selective pressure on genes involved in response to stress, potentially related to the climatic instability of its environment and its elongated lifespan. Finally, we detect no population structure or homozygosity excess in our five-individual sample. Conclusions: These results enlighten the molecular evolution of an endangered taxon in a stressful environment and point to island endemic species as a promising model for the study of the deleterious effects on genome evolution of a reduced long-term population size.
546			_aEnglish
653			_aGiant tortoise.
653			_aTortugas Gigantes.
653			_aGalapagos.
653			_aChelonoidis nigra.
653			_aEndangered.
653			_aPeligro de extinción.
700	1		_aChiari, Ylenia. _92256
700	1		_aBernard, Aurélien.
700	1		_aCahais, Vincent.
700	1		_aRomiguier, Jonathan.
700	1		_aLourenço, Joao Miguel.
700	1		_aGaltier, Nicolas.
773	0		_gVol. 14 (2013), p. 1-11 _tGenome Biology.
942			_2ddc _cARTICLE
999			_c13061 _d13061