Loss of function (LoF) genetic variants are predicted to disrupt gene function, and are therefore expected to substantially reduce individual's viability. Knowing the genetic burden of LoF variants in endangered species is of interest for a better understanding of the effects of declining population sizes on species viability. In this study, we have estimated the number of LoF polymorphic variants in six great ape populations, based on whole-genome sequencing data in 79 individuals. Our results show that although the number of functional variants per individual is conditioned by the effective population size, the number of variants with a drastic phenotypic effect is very similar across species. We hypothesize that for those variants with high selection coefficients, differences in effective population size are not important enough to affect the efficiency of natural selection to remove them. We also describe that mostly CpG LoF mutations are shared across species, and an accumulation of LoF variants at olfactory receptor genes in agreement with its pseudogenization in humans and other primate species.

The authors thank funding to F.C. by grant SAF2012-35025 from the Ministerio de Economía y Competitividad (Spain) and FEDER and by Direcció General de Recerca, Generalitat de Catalunya (2014SGR-866). T.M.B. is supported by EMBO YIP 2013, MINECO BFU2011-28549, BFU2014-55090-P (FEDER), BFU2015-7116-ERC and BFU2015-6215-ERC (www.mecd.gob.es), NIH U01 MH106874 grant and Fundació Zoo Barcelona.