Mitochondrial DNA variation in geographic populations of Colorado potato beetle,Leptinotarsa decemlineata (Coleoptera; Chrysomelidae)

Summary This study demonstrates variability in restriction enzyme cleavage sites of mitochondrial DNA (mtDNA) among four popalations of Colorado potato beetle (CPB). A suite of three enzymes (EcoRI,HpaI,PstI) was sufficient to discriminate among the populations tested. Individuals heteroplasmic for restriction enzyme patterns were found in some populations. Variability in CPB mtDNA should prove useful in efforts to trace the origin and dispersal of the species in North America.     

Rapid isolation of mitochondrial DNA. Mitochondrial DNA fromDrosophila serrata

A simple and rapid method for isolation of high quality mitochondrial DNA (mtDNA) is presented in this report. Using this method, isolation and restriction site maps for 10 enzymes of the mtDNA ofDrosophila serrata were established.     

Geographic populations of the medfly may be differentiated by mitochondrial DNA variation

Restriction enzyme cleavage sites of mitochondrial DNA (mtDNA) from the Mediterranean fruit fly were found to vary among introduced populations in the Neotropics. The survey included samples from 15 established natural populations and 5 laboratory cultures from Hawaii, Central America, South America and West Africa and samples from recent California infestations (1989, 1991). Based on restriction fragment length polymorphisms from 2 enzymes, Hawaii is an unlikely source for the 1989 and 1991 California infestations. Interpopulational variation in mtDNA demonstrates the potential for the technique to trace the process of colonization (geographic spread) by this insect.     

A mitochondrial DNA polymorphism in honeybees (Apis mellifera L.)

Summary Mitochondrial DNA (mtDNA), isolated from worker honeybee larvae, was digested by each of seven 6-base restriction enzymes. Only one enzyme (BglII) showed a mtDNA difference between the three tested races (Apis mellifera carcia, A. m. ligustica, A.m. caucasica). BothA.m. carnica andA.m. ligustica showed the same pattern, differing fromA.m. caucasica. The degree of fragment pattern similarity revealed that there is only a small level of mtDNA variation between the three races tested. This is in line with previous investigations of enzyme polymorphisms.     

Concordant change in mitochondrial and nuclear genes in a hybrid zone between two frog species (genusBombina)

Summary In contrast to results in other studies, nuclear and mitochondrial genes were found to change concordantly in a transect across the hybrid zone betweenBombina bombina andBombina variegata. mtDNAs of both species are found in populations in the central part of the zone, whereas populations at its margins contain mtDNA corresponding to nuclear genomes.     

A simple test using restricted PCR-amplified mitochondrial DNA to study the genetic structure ofApis mellifera L

The COI-COII intergenic region ofApis mellifera mitochondrial DNA contains an important length polymorphism based on a variable number of copies of a 192–196 bp sequence (Q) and the completer or partial deletion of 67 pb sequence (Po). This length variability has been combined with a restriction site polymorphism to produce a rapid and simple test for the characterization of mtDNA haplotypes. This test included the amplification by the polymerase chain reaction of the COI-COII region followed by aDraI restriction of the amplified fragment. In a survey of 302 colonies belonging to 12 subspecies, 21 different haplotypes have been found which have been unambiguously allocated to one of the 3 mtDNA lineages of the species. Although all colonies of lineage C exhibit the same pattern (C1), each one of lineages A and M presents up to 10 different haplotypes, opening the way to studies on the genetic structure and the evolution of a large fraction of the species. This test also differentiates southern Spanish and South African colonies, which can be of great interest for the Africanized bee problem.     

Mitochondrial DNA evidence for the 19th century introduction of African honey bees into the United States

Since the introduction of an African subspecies into Brazil in the mid-1950's¹, descendent Africanized honey bees (Apis mellifera L.) have spread throughout the Neotropics and into temperate North America. Restriction enzyme analysis of 422 feral honey bee colonies collected from non-Africanized areas in the southern United States revealed that over 21% of them had mitochondrial DNA (mtDNA) derived from a European race established in North America by the 17th century, 77% of them had mtDNA common in honey bees maintained by beekeepers and about 1% exhibited African mtDNA. Further analysis revealed that the African mtDNA was derived from a north African subspecies imported to the US in the 19th century.     

Heterochromatin characterization and distribution in the chromosomes of two populations ofIdotea baltica basteri Audouin, 1826 (Isopoda,Valvifera)

Two mediterranean populations ofIdotea baltica basteri from Messina and Naples showed a set of chromosomes composed by 58 all-biarmed chromosomes. The heterochromatin was located in the pericentromeric region of the chromosomes, and its composition appeared heterogeneous. In fact, not all the homologs showed heterochromatin resistant to digestion with three restriction enzymes (Alu I, Hae III and Sau 3A). Moreover, the two populations showed polymorphism in a band of G+C-rich telomeric heterochromatin, which was present only in the population from Messina. It is hypothesized that chromosomal polymorphism might reflect the geographical isolation of the two populations. It is also suggested that a process of diversification is taking place.     

Population genetics of a colonizing lizard: Loss of variability in introduced populations ofPodarcis sicula

Allozyme electrophoresis was used to study the genetic variability (proportion of polymorphic loci and heterozygosity) in insular populations (Corsica, Elba, Montecristo, Marettimo, Pantelleria) of the lacertid lizardPodarcis sicula. These populations were presumed to have originated from episodes of accidental anthropogenic introduction. In order to test the hypothesis of a man-aided colonization and to provide comparative data, heterozygosity and polymorphism were also estimated in autochthonous populations ofP. sicula from the Italian peninsula and Sicily. In each case, the presumed introduced population showed levels of genetic variability significantly lower than those detected in the autochthonous ones. Very little genetic differentiation was found among native and presumed colonist populations, Nei's standard genetic distances ranging from 0.001 to 0.009. These results strongly support the hypothesis thatP. sicula was only recently introduced to the studied islands, and provide additional evidence of reduced genetic variability due to founder effect in insular populations originating from episodes of human transportation.     

Gel-electrophoretic description of European populations ofTerellia virens (Loew) (Diptera,Tephritidae); implications for its use as an agent for the biological control ofCentaurea spp. (Asteraceae) in North America

Allozyme frequencies of 15 enzyme loci, 14 of which were polymorphic, were used to characterize sevenTerellia virens populations originating from three allopatrically distributedCentaurea species. The two populations whose origins were geographically furthest apart, from Israel (onC. iberica) and from Switzerland (onC. vallesiaca), showed relatively high values of genetic distance from the 5 populations sampled in Austria and Hungary (onC. maculosa) (Nei's D>0.07). The latter five displayed a high degree of genetic similarity. No diagnostic (fixed) allelic differences were observed between these three groups ofT. virens populations, but they could be well characterized by significant differences in allelic frequencies at 9 enzyme loci. Independently of this study, the populations from Switzerland (C. vallesiaca) and eastern Austria (C. maculosa) were selected as potential source populations for future introductions into North America for the biological control of introducedC. maculosa andC. diffusa. Based on the observed genetic differences and results from field experiments on the host specificity of these two potential source populations, it is argued that host specificity screening tests should be conducted separately for local (host plant) populations, as such populations might accept a different set of hosts. Biotype mismatch and the risk of spill-overs to native species could thus possibly be reduced.     

Naja siamensis, a cryptic species of venomous snake revealed by mtDNA sequencing

Because of possible variation in venom composition, an understanding of venomous snake systematics is of great importance for the optimization of antivenom treatment of snakebite patients. Intraspecific variation in the morphology of many venomous snakes complicates the definition and indentification of some species when allopatric populations are involved. Selectively neutral or near-neutral mtDNA sequences can reveal evolutionary relationships obscured by ecogenetically-caused morphological variation. We use comparative sequencing of the cytochrome oxidase subunit 1 gene to reveal the existence of a widespread, cryptic species of spiting cobra from southeast Asia. This species,Naja siamensis, is widely sympatric with other Asiatic cobra species. This may be of considerable medical significance, and calls for further research into venom composition in Asiatic cobras.     

The evolutionary history ofDrosophila buzzatii. V. Differential survivorship onOpuntia betweenD. buzzatii andD. serido

Summary Survival time ofDrosophila buzzatii adults on anOpuntia (prickly pear) medium was significantly longer than that of its nearest relativeD. serido. A significant difference was also found betweenD. buzzatii adults from two experimental populations, one of them fed onOpuntia rots for more than two years and another one kept on standardDrosophila medium for the same period of time. These results suggest that adult selection may be taking place in cactiphilicDrosophila in their natural habitats and could be responsible for the niche differentiation betweenD. buzzatii andD. serido.This work has been supported by the Comisión Asesora de investigación Científica y Técnica, Spain, by funds to project 4514/79 awarded to the third author.     

Polymorphisms in mitochondrial DNA of european and Africanized honeybees (Apis mellifera)

Summary This study demonstrates polymorphisms in both the length and in the restriction enzyme cleavage sites of honeybee mitochondrial DNA (mtDNA). The levels of variation are typical of those found in other metazoan species. These polymorphisms are potentially useful for the identification of Africanized bees in the western hemisphere and for study of honeybee phylogenetics.     

Ancient DNA from Bronze Age bones of European rabbit (Oryctolagus cuniculus)

The European rabbit (Oryctolagus cuniculus) is now widely distributed throughout the world as a result of transportation by man. The original populations, however, were confined to southern France and Spain. In order to investigate the role of human intervention in determining the genetic diversity of rabbit populations, we are studying the origin of rabbits introduced onto a small Mediterranean island (Zembra) near Tunis over 1400 years ago, by examining ancient DNA extracted from rabbit bones found both on Zembra and on the European mainland. Ancient DNA was successfully extracted from rabbit bones found at two archaeological sites dated to at least the Early Bronze Age (more than 3500 years ago) in south-central France, and compared to that found in modern mainland and island populations using a small variable region of the cytochromeb gene. The results confirm that the Zembra Island population is descended from that present over 1400 years ago. The technical aspects of DNA extraction from bones and the implications of this type of research for determining the origin of introduced rabbit populations are discussed.     

Low allozyme and mtDNA variability in the island endemic speciesDrosophila sechelia (D. melanogaster complex)

Summary Genetic variability ofD. sechellia is investigated at both mitochondrial and nuclear levels. The results reveal the existence of a single main type of mtDNA with very few variants and a very low enzyme polymorphism. This situation is consistent with the small population size of this specialized species.     

Genetic basis of some morphological differences between temperate and equatorial populations ofDrosophila melanogaster

The genetic basis of three morphological traits (ovariole number, sternopleural bristle number and wing length) ofDrosophila melanogaster has been investigated in natural populations that show great differences in these traits, i. e. Bordeaux (France) and Loua (Congo). F1 and F2 crosses, and chromosome substitutions between these two populations, were analysed. Maternal and/or X chromosome effects were found for sternopleural bristle number and wing length. For all traits, significant effects from each of the three chromosomes were found, but in general only one or two chromosomes had a major effect. Moreover, in all cases significant interactions between chromosomes were observed, suggesting the existence of epistatic effects. Our results are discussed and compared to those obtained from the analysis of selected laboratory strains.     

Mapping of restriction enzyme cuts by a new two-dimensional procedure

Summary A new procedure has been worked out to establish restriction maps. The method is fast, does not in general require labeled DNA and has been applied to map the linear palindromic rDNA ofPhysarum with the restriction enzymeBstEII.Acknowledgment. This work was supported by grants from the NIH (GM-30338), the NSF (PCM 8116391) and the Swiss National Science Foundation (3.075.81).     

Genetic variation in the New World: Ancient teeth,bone, and tissue as sources of DNA

Examination of ancient and contemporary Native American mtDNA variation via diagnostic restriction sites and the 9-pb Region V deletion suggests a single wave of migration into the New World. This is in contrast to data from Torroni et al.³⁴ which suggested two waves of migration into the New World (the NaDene and Amerind). All four founding lineage types are present in populations in North, Central, and South America suggesting that all four lineages came over together and spead throughout the New World. Ancient Native American DNA shows that all four lineages were present before European contact in North America, and at least two were present in South America. The presence of all four lineages in the NaDene and the Amerinds argues against separate migrations founding these two groups, although admixture between the groups is still a viable explanation for the presence of all four types in the NaDene.     

Rapid isolation of mitochondrial DNA. Mitochondrial DNA from Drosophila serrata.

A simple and rapid method for isolation of high quality mitochondrial DNA (mtDNA) is presented in this report. Using this method, isolation and restriction site maps for 10 enzymes of the mtDNA of Drosophila serrata were established.     

DNG1, a Dictyostelium homologue of tumor suppressor ING1 regulates differentiation of Dictyostelium cells

dng1 is a Dictyostelium homologue of the mammalian tumor suppressor ING gene. DNG1 protein localizes in the nucleus, and has a highly conserved PHD finger domain found in chromatin-remodeling proteins. Both dng1 disruption and overexpression impaired cell proliferation. In dng1-null cells, the progression of differentiation was delayed in a cell-density-dependent manner, and many tiny aggregates were formed. Exogenously applied cAMP pulses reversed the inhibitory effect caused by dng1 disruption on the aggregation during early development, but formation of tiny aggregates was not restored. dng1-overexpressing cells acquired the ability to undergo chemotaxis to cAMP earlier and exhibited enhanced differentiation. These phenotypes were found to be coupled with altered expressions of early genes such as cAMP receptor 1 (car1) and contact site A (csA). Furthermore, disordered histone modifications were demonstrated in dng1-null cells. These results suggest a regulatory role of dng1 in the transition of cells from growth to differentiation.Received 29 December 2004; received after revision 24 May 2005; accepted 26 May 2005