Big and

• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: baleen whales; Humpback Whale
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.664.3767; http://palumbi.stanford.edu/manuscripts/big+and+slow.pdf

Baleen whales are the largest animals that have ever lived. To develop an improved estimation of substitution rate for nuclear and mitochondrial DNA for this taxon, we implemented a relaxed-clock phylogenetic approach using three fossil calibration dates: the divergence between odontocetes and mysticetes;34 million years ago (Ma), between the balaenids and balaenopterids;28 Ma, and the time to most recent common ancestor within the Balaenopteridae;12 Ma. We examined seven mitochondrial genomes, a large number of mitochondrial control region sequences (219 haplotypes for 465 bp) and nine nuclear introns representing five species of whales, within which multiple species-specific alleles were sequenced to account for within-species diversity (1–15 for each locus). The total data set represents.1.65 Mbp of mitogenome and nuclear genomic sequence. The estimated substitution rate for the humpback whale control region (3.9%/million years, My) was higher than previous estimates for baleen whales but slow relative to other mammal species with similar generation times (e.g., human–chimp mean rate. 20%/My). The mitogenomic third codon position rate was also slow relative to other mammals (mean estimate 1%/My compared with a mammalian average of 9.8%/My for the cytochrome b gene). The mean nuclear genomic substitution rate (0.05%/My) was substantially slower than average synonymous estimates for other mammals (0.21–0.37%/My across a range of studies). The nuclear and mitogenome rate estimates for baleen whales were thus roughly consistent with an 8- to 10-fold slowing due to a combination of large body size and long generation times. Surprisingly, despite the large data set of nuclear intron