Two new fern chloroplasts and decelerated evolution linked to the long generation time in tree ferns.
We report the chloroplast genomes of a tree fern (Dicksonia squarrosa) and a "fern ally" (Tmesipteris elongata), and show that the phylogeny of early land plants is basically as expected, and the estimates of divergence time are largely unaffected after removing the fastest evolving sites. The tree fern shows the major reduction in the rate of evolution, and there has been a major slowdown in the rate of mutation in both families of tree ferns. We suggest that this is related to a generation time effect; if there is a long time period between generations, then this is probably incompatible with a high mutation rate because otherwise nearly every propagule would probably have several lethal mutations. This effect will be especially strong in organisms that have large numbers of cell divisions between generations. This shows the necessity of going beyond phylogeny and integrating its study with other properties of organisms.
Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand bjzhong@gmail.com.
Bojian
B
Zhong
Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand.
Richard
R
Fong
Faculty of Health Sciences, Universal College of Learning, Palmerston North, New Zealand.
Lesley J
LJ
Collins
Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand.
Patricia A
PA
McLenachan
Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand.
David
D
Penny
D005075:Biological Evolution; D029624:Ferns / Q000235:genetics*; D005828:Genetics, Population; D054628:Genome, Chloroplast; D008969:Molecular Sequence Data; D059645:Mutation Rate; D009520:New Zealand; D010802:Phylogeny
Dicksonia; Tmesipteris; chloroplast genomes; ferns and fern allies; generation time effect; mutation rates