Mitochondrial genome size variation in New World and Old World populations of Drosophila melanogaster (original) (raw)
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Evolution of Drosophila mitochondrial DNA and the history of the melanogaster subgroup
Proceedings of the National Academy of Sciences, 1990
The nucleotide sequences of a common region of 15 mitochondrial DNAs (mtDNAs) sampled from the Drosophila melanogaster subgroup were determined. The region is 2527 base pairs long, including most of the NADH dehydrogenase subunit 2 and cytochrome oxidase subunit 1 genes punctuated by three tRNA genes. The comparative study revealed (i) the extremely low saturation level of transitional differences, (ii) recombination or variable substitution rates even within species, (iii) long persistence times of distinct types of mtDNA in Drosophila simulans and Drosophila mauritiana, and (iv) an apparent lack of within-type variations in island species. Also found was a high correlation among the transitional rate, the saturation level, and the G+C content (or codon usage). It appears that D. simulans and D. mauritiana have maintained highly structured populations for more than 1 million years. Such structures are consistent with the origination of Drosophila sechellia from D. simulans. Yet geographic isolation is so weak as to show no evidence for further speciation. Moreover, one type of mtDNA shared by D. simulans and D. mauritiana suggests either recent divergence or ongoing introgression.
Mitochondrial DNA Variation and Genetic Structure in Old-World Populations of Drosophila subobscura
To discover the relation between mitochondrial DNA (mtDNA) polymorphism and the geographic population structure of Drosophila subobscura previously established for other genetic traits, a wide Paleartic survey was carried out. A total of 24 nucleomorphs was observed among 26 1 isofemale lines assayed by 11 restriction endonucleases with 38 different sites in the mtDNA cleavage map. The differentiation of the Canary Islands populations (6 = 0.0119) compared with the mean among all the other continental and insular populations (6 = 0.0002) is striking. Both the great divergence among Canary Islands nucleomorphs (6 = 0.02 1) compared with the maximum nucleomorph distance in all other populations (6 = 0.0 17) and the abundance of endemic nucleomorphs (11) on the Canary Islands (50% of the total number of different nucleomorphs found in the entire distribution area) suggest that this molecular differentiation most probably results from the very old age of the Canary Islands populations rather than from drift and founder effects.
Both original and colonizer populations of Drosophila buzzatii have been analyzed for mtDNA restriction polymorphisms. Most of the mtDNA nucleotide variation in original populations of NW Argentina can be explained by intrapopulation diversity and only a small fraction can be accounted for by between-population diversity. Similar results are obtained using either the estimated number of nucleotide substitutions per site or considering each restriction site as a locus. Colonizer populations of the Iberian Peninsula are monomorphic and show only the most common haplotype from the original populations. Under the infinite island model and assuming that populations are in equilibrium, fixation indices indicate enough gene flow to explain why the populations are not structured. Yet, the possibility exists that populations have not reached an equilibrium after a founder event at the end of the last Pleistocene glaciation. Tajima's test suggests that directional selection and/or a recent bottleneck could explain the present mtDNA differentiation. Considering the significant population structure found for the chromosomal and some allozyme polymorphisms, the among-population uniformity for mtDNA variability argues in favor of the chromosomal and some allozyme polymorphisms being adaptive.
Comparative genomics of mitochondrial DNA in members of the Drosophila melanogaster subgroup
2000
In this study, a comparative genomics approach is employed to investigate the forces that shape evolutionary change in the mitochondrial DNA (mtDNA) of members of the Drosophila melanogaster subgroup. This approach facilitates differentiation of the patterns of variation resulting from processes acting at a higher level from those acting on a single gene. The mitochondrial genomes of three isofemale lines of D. simulans (siI, -II, and -III), two of D. melanogaster (Oregon R and a line from Zimbabwe), and D. mauritiana (maI and -II), and one of D. sechellia were sequenced and compared with that derived from D. yakuba. Data presented here indicate that at least three broad mechanisms shape the evolutionary dynamics of mtDNA in these taxa. The first set of mechanisms is intrinsic to the molecule. Dominant processes may be interpreted as selection for an increased rate of replication of the mtDNA molecule, biases in DNA repair, and differences in the pattern of nucleotide substitution among strands. In the genes encoded on the major strand (62% of the coding DNA) changes to or from C predominate, whereas on the minor changes to or from G predominate. The second set of mechanisms affects distinct lineages. There are evolutionary rate differences among lineages, possibly owing to population demographic changes or changes in mutational biases. This is supported by the heterogeneity found in synonymous, nonsynonymous, and silent substitutions. The third set of mechanisms differentially affects distinct genes. A maximum-likelihood slidingwindow analysis detected four disjunct regions that have a significantly different nucleotide substitution process from that derived from the complete sequence. These data show the potential for comparative genomics to tease apart subtle forces that shape the evolution of DNA.
Molecular Biology and Evolution, 1991
Recent empirical and theoretical studies on mitochondrial DNA (mtDNA) variation in higher animals have suggested that the extent of mtDNA polymorphism is largely affected by spatial population subdivision. To examine this we studied mtDNA polymorphism in two subspecies of Drosophila sulfurigaster: D. s. albostrigata and D. s. bilimbata. Drosophila sulfurigaster albostrigata is mainly distributed on the mainland of Southeast Asia. In contrast, D. s. bilimbata forms discontinuous populations on many islands scattered in the Pacific Ocean. Because of the difference in their distribution patterns, the two subspecies are thought to be different in the extent of spatial population subdivision. mtDNA was isolated from >50 isofemale strains for each subspecies and were analyzed by eight restriction endonucleases. Nucleotide diversity within a population was higher in D. s. albostrigata than in D. s. bifimbata. However, haplotype diversity was 1.6 times greater in D. s. bilimbata (0.85) than in D. s. albostrigata (0.53). The large difference in overall heterogeneity was attributed to the difference in interpopulational nucleotide diversity. For the two subspecies the proportion of interpopulational gene diversity in a subdivided population was calculated to be 0.54 in D. s. bilimbata and 0.40 in D. s. albostrigata. These observations indicate that spatial population subdivision is a major factor in determining mtDNA polymorphism in these subspecies. The extent of mtDNA divergence between the subspecies was very high. The average nucleotide divergence between them was 7.6%, which is almost the interspecific level reported for other Drosophila species. The cause of the high degree of mtDNA divergence is discussed.
Dynamics of mitochondrial polymorphism in a natural population of Drosophila littoralis
Russian Journal of Genetics, 2008
During seven years, we observed stable mtDNA polymorphism in a local population of Drosophila littoralis. Using RFLP, a number of mitochondrial haplotypes were revealed, two of which were the core and in condition of stable equilibrium. To explain the absence of fixation of one haplotype, we checked a hypothesis that the D. littoralis population had a complex structure, being subdivided into several partially isolated races existing on the same territory. Analysis of highly hypervariable nuclear sequence of retrotransposons Tv1 showed positive correlation of the mitochondrial haplotype with a particular allelic form of Tv1. This supports the proposal that the D. littoralis natural population forms the population system consisting of genetically differentiated races.
The recent colonization of South America Brncic et al. 198 1) and North America by the Paleartic species Drosophila subobscura has offered the opportunity to test empirically the effect of a founder event on different levels of polymorphism in an expanding population. Analysis of chromosomal inversion polymorphism ), allozyme polymorphism (Prevosti et al. 1983, gametic associations of allozymes and chromosomal gene arrangements ) and allelism of lethals (Mestres et al., accepted) showed that only a mild founder effect occurred at the beginning of the colonization, but not during its expansion.
Evolution of Mitochondrial DNA in Drosophila subobscura
Proceedings of The National Academy of Sciences, 1986
The colonization of the New World by the Palearctic species Drosophila subobscura was first detected in 1978 in South America and around 1982 in western North America. The ensuing dramatic expansion of the species, in territory as well as numbers, provides an opportunity for studying evolution in a scale rarely possible. We have used 10 restriction endonucleases to analyze the mitochondrial DNA (mtDNA) of individuals from 23 widely dispersed localities. Only two mtDNA composite morphs have been detected in the Americas. None of the two morphs has been found in Africa, and only one in the Atlantic islands; but both are widespread in Europe, which provides no clue of the precise geographic origin of the colonizers. The amount of nucleotide-substitution polymorphism detected in D. subobscura is typical for animals, but it is greater in the Old than in the New World, presumably due to the recent colonization by a limited number of colonizers. Assuming standard evolutionary rates of mtDNA base substitution, the mtDNA morphs found in D. subobscura can be traced to a single one that existed no less than one million years ago. We argue against the inference that the D. subobscura flies now living descend from only one or a few females that lived at that time. This type of inference, which we call the "Mother Eve hypothesis," has been made to conclude that the human population went through a severe constriction about 200,000 years ago, so that all living humans descend from only one or a few women who lived at that time. The Mother Eve hypothesis is fallacious.
Variation of the Mitochondral Genome in the Evolution of Drosophila
2002
The evidence on mitochondrial genome variation and its role in evolution of the genus Drosophila are reviewed. The mitochondrial genome is represented by a circular double-stranded DNA molecule 16 to 19 kb in length. Mitochondrial genes lack introns and recombination. The entire mitochondrial genome can be arbitrarily divided into three parts: (1) protein-coding genes; (2) genes encoding rRNA and tRNA; and (3) the noncoding regulatory region (A + T region). The selective importance of mutations within different mtDNA regions is therefore unequal. In Drosophila , the content of the A + T pairs in mtDNA is extremely high and a pattern of nucleotide substitution is characterized by a low transition/transversion ratio (and a low threshold of mutation saturation). The deletions and duplications are of common occurrence in the mitochondrial genome. However, this genome lacks such characteristic for the nuclear genome aberrations as inversions and transpositions. The phenomena of introgression and heteroplasmy provide an opportunity to study the adaptive role of the mitochondrial genome and its role in speciation. Analysis of evidence concerning mtDNA variation in different species of the genus Drosophila made it possible to ascertain data on phylogenetic relationships among species obtained by studying nuclear genome variation. In some species, mtDNA variation may serve as a reliable marker for population differentiation within a species, although evidence on the population dynamics of the mtDNA variation is very scarce.
Genetics, 1987
Restriction endonuclease analysis of mtDNA was used to examine the genetic relatedness of several geographically separated isolines of the Drosophila mercatorum subgroup. In addition, we examined the temporal and spatial distribution of two mtDNA restriction site polymorphisms produced by the enzymes BstEII and BstNI at a single locality--Kamuela, Hawaii. Due to small sample sizes of some collections and the undesirable dependance of the estimation of polymorphism frequency on its variance, an arcsin square root transformation of the frequency data was used. We also use an Fst estimator of our transformed frequencies to demonstrate considerable spatial and temporal differentiation within the Kamuela population. In contrast, isozyme data from the same population reveals no pattern of differentiation. The temporal and geographic heterogeneity and population subdivision detected with mtDNA analysis also is consistent with the known dispersal behavior and ecological constraints of this ...