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C Moritz

Publications and source records attributed to C Moritz.

45 records · Page 3Linked to original sources
PubMed1993

Rapid assessment of single-copy nuclear DNA variation in diverse species.

We investigated the use of PCR primers designed to conserved exons within nuclear DNA to amplify potentially variable regions such as introns or hypervariable exons from a wide range of species. We then explored various approaches to assay population-level variation in these PCR products. Primers designed to amplify regions within the histone H2AF, myoglobin, MHC DQA, and aldolase (ALD) genes gave clean amplifications in diverse mammals (DQA), and in birds, reptiles and mammals (aldolase, H2AF, myoglobin). The sequenced PCR products generally, but not always, confirmed that the correct locus had been amplified. Several primer sets produced smaller size fragments consistent with preferential amplification of intronless pseudogenes; this was confirmed by sequencing seal and reptile H2AF PCR products. Digestion with randomly selected four-base recognizing enzymes detected variation in some cases but not in others. In species/gene combinations with either low (e.g. seal H2AF, ALD-A) or high (e.g. skink ALD-1) nucleotide diversity it was more efficient to sequence a small number of distantly related individuals (e.g. one per geographic population) and from these data to identify informative or potentially informative restriction enzymes for 'targeted' digestion. We conclude that for studies of population-level variation, the optimal approach is to use a battery of primers for initial PCR of both mtDNA and scnDNA loci, select those that give clean amplifications, and sequence one sample from each population to (i) confirm gene identity, (ii) estimate the amount of variation and, (iii) search for diagnostic restriction sites. This will allow determination of the most efficient approach for a large-scale study.

Amino Acid Sequence↗
PubMed1993

Phylogeny and historical aspects of the ecology of eastern Australian scrubwrens Sericornis spp.--evidence from mitochondrial DNA.

A phylogeny of mainland eastern Australian scrubwrens (Sericornis citreogularis, S. frontalis, S. keri, S. magnirostris and S. beccarii) was constructed using presence or absence of phylogenetically informative restriction sites in 15 mitochondrial DNA (mtDNA) haplotypes. MtDNA sequence divergences between species were generally large (mostly between 10 and 18%) emphasizing the antiquity of this radiation. Phylogenetic analysis of the mtDNA resulted in a strongly supported phylogeny concordant with relationships suggested by a previous study of allozyme variation, but conflicting with concepts based on morphological similarity. The mtDNAs grouped the species into two lineages, one containing beccarii and magnirostris and the other comprising citreogularis, frontalis and keri. The mtDNAs of beccarii and magnirostris were paraphyletic with a northern variant of magnirostris being more similar to beccarii than other magnirostris. The mtDNA from keri was most closely related to that of frontalis and then citreogularis. The strongly corroborated molecular phylogeny confirms and extends the previous (Christidis et al. 1988; Auk 105: 616) reinterpretation of morphological and ecological shifts in the group. This suggests considerable plasticity and parallelism in the plumage characters previously used to associate species. The low divergence and close relationship between the montane rain-forest specialist keri and the widely distributed generalist frontalis demonstrate the capacity for evolutionarily rapid and dramatic shifts in habitat use. This contrasts with the assumption of fixed habitat preference that underlies refuge-based models of diversification of rain-forest fauna.

Animals↗
PubMed1991

Evidence for biased gene conversion in concerted evolution of ribosomal DNA.

Concerted evolution is the production and maintenance of homogeneity within repeated families of DNA. Two mechanisms--unequal crossing over and biased gene conversion--have been the principal explanations of concerted evolution. Concerted evolution of ribosomal DNA (rDNA) arrays is thought to be largely the result of unequal crossing over. However, concerted evolution of rDNA in parthenogenetic lizards of hybrid origin is strongly biased toward one of two parental sequences, which is consistent with biased gene conversion as the operative mechanism. The apparent gene conversions are independent of initial genome dosage and result in homogenization of rDNA arrays across all nucleolar organizer regions.

Animals↗
PubMed1991

Parallel origins of duplications and the formation of pseudogenes in mitochondrial DNA from parthenogenetic lizards (Heteronotia binoei; Gekkonidae).

Analysis of mitochondrial DNAs (mtDNAs) from parthenogenetic lizards of the Heteronotia binoei complex with restriction enzymes revealed an approximately 5-kb addition present in all 77 individuals. Cleavage site mapping suggested the presence of a direct tandem duplication spanning the 16S and 12S rRNA genes, the control region and most, if not all, of the gene for the subunit 1 of NADH dehydrogenase (ND1). The location of the duplication was confirmed by Southern hybridization. A restriction enzyme survey provided evidence for modifications to each copy of the duplicated sequence, including four large deletions. Each gene affected by a deletion was complemented by an intact version in the other copy of the sequence, although for one gene the functional copy was heteroplasmic for another deletion. Sequencing of a fragment from one copy of the duplication which encompassed the tRNA(leu)(UUR) and parts of the 16S rRNA and ND1 genes, revealed mutations expected to disrupt function. Thus, evolution subsequent to the duplication event has resulted in mitochondrial pseudogenes. The presence of duplications in all of these parthenogens, but not among representatives of their maternal sexual ancestors, suggests that the duplications arose in the parthenogenetic form. This provides the second instance in H. binoei of mtDNA duplication associated with the transition from sexual to parthenogenetic reproduction. The increased incidence of duplications in parthenogenetic lizards may be caused by errors in mtDNA replication due to either polyploidy or hybridity of their nuclear genomes.

Amino Acid Sequence↗
PubMed1991

The origin and evolution of parthenogenesis in Heteronotia binoei (Gekkonidae): evidence for recent and localized origins of widespread clones.

The parthenogenetic form of the gecko lizard species Heteronotia binoei has an unusually broad geographic range and high genetic diversity. Restriction enzyme analysis revealed two basic types of mitochondrial DNA (mtDNA) among the parthenogens. One type is restricted to western populations. The other type, analyzed in detail here, was widespread, being found in populations from central to western Australia. The diversity within this widespread type was low. The variation among parthenogens from central to western Australia was similar to that found within local populations of the sexual species that provided the mtDNA, and was an order of magnitude less than the differentiation shown between sexual populations across the same geographic distance. Phylogenetic analysis revealed that the widespread type of mtDNA in the parthenogens is most closely related to mtDNAs from western populations of the "CA6" sexual parent. These data suggest that these parthenogenetic clones arose recently within a small geographic area, most probably in Western Australia. The parthenogens must have spread rapidly to occupy much of the central and western Australian deserts. This rapid and extensive range expansion provides strong evidence that parthenogenesis can be a successful strategy for lizards in an environment with low and unpredictable rainfall.

Animals↗
PubMed1991

Evolutionary dynamics of mitochondrial DNA duplications in parthenogenetic geckos, Heteronotia binoei.

Mitochondrial DNA (mtDNA) from triploid parthenogenetic geckos of the Heteronotia binoei complex varies in size from 17.2 to 27.6 kilobases (kb). Comparisons of long vs. short genomes using restriction endonucleases revealed a series of tandem direct duplications ranging in size from 1.2 to 10.4 kb. This interpretation was supported by transfer-hybridization experiments which also demonstrated that coding sequences were involved. Some of the duplications have been modified by deletion and restriction site changes, but no other rearrangements were detected. Analysis of the phylogenetic and geographic distribution of length variation suggests that duplications have arisen repeatedly within the parthenogenetic form of H. binoei. The parthenogens, and thus the duplications, are of recent origin; modifications of the duplicated sequences, particularly by deletion, has therefore been rapid. The absence of duplications from the mtDNA of the diploid sexual populations of H. binoei reinforces the correlation between nuclear polyploidy and duplication of mtDNA sequences reported for other lizards. In comparison to the genomes of sexual H. binoei and of most other animals, the mtDNA of these parthenogenetic geckos is extraordinarily variable in length and organization.

Animals↗
PubMed1987

Tandem duplications in animal mitochondrial DNAs: variation in incidence and gene content among lizards.

Size, location, gene content, and incidence were determined for 10 lizard mitochondrial DNA duplications. These range from 0.8 to 8.0 kilobases (kb) and account for essentially all of the observed size variation (17-25 kb). Cleavage-site mapping and transfer-hybridization experiments indicate that each duplication is tandem and direct, includes at least one protein or rRNA gene, and is adjacent to or includes the D loop-containing control region. Duplication boundaries are nonrandomly distributed, and most appear to align with tRNA genes, suggesting that these may play a role in the duplication process. Duplications are infrequent and usually restricted to particular individuals or populations. They appear to be ephemeral; in no case is the same duplication shared by mitochondrial DNAs from closely related species. Mitochondrial DNA duplications occur significantly more often in triploid than diploid lizards and at similar frequencies in hybrids and nonhybrids.

Animals↗
PubMed1986

Tandem duplication of D-loop and ribosomal RNA sequences in lizard mitochondrial DNA.

Some Cnemidophorus exsanguis have mitochondrial DNA's (mtDNA's) that are 22.2 kilobases (kb) in size, whereas most have mtDNA's of 17.4 kb. Restriction site mapping, DNA transfer hybridization experiments, and electron microscopy show that the size increment stems from the tandem duplication of a 4.8-kb region that includes regulatory sequences and transfer and ribosomal RNA genes. This observation is notable in that sequences outside of the control region are involved in major length variation. Besides revealing a novel form of mtDNA evolution in animals, these duplications provide a useful system for investigating the molecular and evolutionary biology of animal mtDNA.

Animals↗