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81.
The rapidly evolving mitochondrial control region remains an important source of information on phylogeography and demographic
history for cetaceans and other vertebrates, despite great uncertainty in the rate of nucleotide substitution across both
nucleotide positions and lineages. Patterns of variation in linked markers with slower rates of evolution can potentially
be used to calibrate the rate of nucleotide substitution in the control region and to better understand the interplay of evolutionary
and demographic forces across the mitochondrial genome above and below the species level. We have examined patterns of diversity
within and between three baleen whale species (gray, humpback, and Antarctic minke whales) in order to determine how patterns
of molecular evolution differ between cytochrome b and the control region. Our results show that cytochrome b is less variable than expected given the diversity in the control region for gray and humpback whales, even after functional
differences are taken into account, but more variable than expected for minke whales. Differences in the frequency distributions
of polymorphic sites and in best-fit models of nucleotide substitution indicate that these patterns may be the result of hypervariability
in the control region in gray and humpback whales but, in minke whales, may result from a large, stable or expanding population
size coupled with saturation at the control region. Using paired cytochrome b and control region data across individuals, we show that the average rate of nucleotide substitution in the control region
may be on average 2.6 times higher than phylogenetically derived estimates in cetaceans. These results highlight the complexity
of making inferences from control region data alone and suggest that applying simple rules of DNA sequence analyses across
species may be difficult. 相似文献
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Stephen R. Palumbi Allan C. Wilson 《Evolution; international journal of organic evolution》1990,44(2):403-415
Restriction-fragment analysis was used to measure mitochondrial DNA (mtDNA) variability in 79 individuals of two species of temperate sea urchins. For the purple urchin Strongylocentrotus purpuratus, individuals were collected 1,500 km apart in 1985 and again from the same localities in 1988 (about one urchin generation). Twenty mtDNA genotypes belonging to four clades were found among 38 individuals. All four clades were found in both localities and in both years. Genetic structure was further tested by calculating the degree of interdeme genetic variation (GST) and comparing this value to the GST's from randomly shuffled data. No geographic structure was found. For S. droebachiensis, only six mtDNA genotypes were found among 41 individuals collected from the Pacific and Atlantic oceans. More than 80% of the individuals belonged to two genotypes. The genotype that dominated collections in the Pacific also occurred in the Atlantic; however, a common Atlantic genotype was never found in the Pacific. These two genotypes were identical at 64 of 65 restriction sites, and were only 0.2% divergent from each other. GST analysis confirmed that there were significant genetic differences between Atlantic and Pacific populations. The small divergence between genotypes suggests recent, but not continuous, migration. These marine species show smaller genotypic differences than terrestrial species over similar spatial and temporal scales. Both recruitment of adults from planktonic larval pools and the spread of sibling larvae over large distances from parents probably act as buffers to genetic differences in species with planktonic life-history phases. 相似文献
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Coral Reefs - Species-range information forms the empirical data base for much of biogeography, but even with a huge amount of data on species occurrences, many of the ecological and... 相似文献
86.