title: Direct Determination of the Mutation Rate in the Bumblebee Reveals Evidence for Weak Recombination-Associated Mutation and an Approximate Rate Constancy in Insects.
abstract: Accurate knowledge of the mutation rate provides a base line for inferring expected rates of evolution, for testing evolutionary hypotheses and for estimation of key parameters. Advances in sequencing technology now permit direct estimates of the mutation rate from sequencing of close relatives. Within insects there have been three prior such estimates, two in nonsocial insects (Drosophila: 2.8 × 10-9per bp per haploid genome per generation; Heliconius: 2.9 × 10-9) and one in a social species, the honeybee (3.4 × 10-9). Might the honeybee's rate be ∼20% higher because it has an exceptionally high recombination rate and recombination may be directly or indirectly mutagenic? To address this possibility, we provide a direct estimate of the mutation rate in the bumblebee (Bombus terrestris), this being a close relative of the honeybee but with a much lower recombination rate. We confirm that the crossover rate of the bumblebee is indeed much lower than honeybees (8.7 cM/Mb vs. 37 cM/Mb). Importantly, we find no significant difference in the mutation rates: we estimate for bumblebees a rate of 3.6 × 10-9per haploid genome per generation (95% confidence intervals 2.38 × 10-9and 5.37 × 10-9) which is just 5% higher than the estimate that of honeybees. Both genomes have approximately one new mutation per haploid genome per generation. While we find evidence for a direct coupling between recombination and mutation (also seen in honeybees), the effect is so weak as to leave almost no footprint on any between-species differences. The similarity in mutation rates suggests an approximate constancy of the mutation rate in insects.
authors.affiliation: State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, China.
authors.forename: Haoxuan
authors.initials: H
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, China.
authors.forename: Yanxiao
authors.initials: Y
authors.lastname: Jia
authors.affiliation: State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, China.
authors.forename: Xiaoguang
authors.initials: X
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, China.
authors.forename: Dacheng
authors.initials: D
authors.lastname: Tian
authors.affiliation: Department of Biology and Biochemistry, The Milner Centre for Evolution, University of Bath, Bath, United Kingdom bssldh@bath.ac.uk sihaiyang@nju.edu.cn.
authors.forename: Laurence D
authors.initials: LD
authors.lastname: Hurst
authors.affiliation: State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, China bssldh@bath.ac.uk sihaiyang@nju.edu.cn.
authors.forename: Sihai
authors.initials: S
authors.lastname: Yang
mesh_terms: D000818:Animals; D001516:Bees / Q000235:genetics*; D005075:Biological Evolution; D019143:Evolution, Molecular; D016678:Genome; D049750:Genome, Insect; D009154:Mutation; D059645:Mutation Rate; D011995:Recombination, Genetic
keywords: bee; biased gene conversion; mutation rate; recombination rate