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At least 127 records · Page 7Linked to original sources
PubMed1992

The alcohol dehydrogenase polymorphism in natural populations of Drosophila melanogaster: ADH activity variation restriction site polymorphism and the Adh cline.

Alcohol dehydrogenase activity has been measured in 186 iso-second chromosome lines--104 from seven Australian populations and 82 from six Chinese populations. Restriction endonuclease variation in the Adh gene region in these lines has previously been described (Jiang & Gibson, 1991). The mean ADH activity of AdhF and AdhS lines was significantly higher in the Chinese samples than in the Australian samples. In each population on both continents the mean activity of the AdhF lines is significantly higher than that of the AdhS lines. Six lines homozygous for a thermostability variant, AdhFChD (detected in four of the Chinese populations), had intermediate levels of ADH activity and protein amount. In a subset of the lines with the highest and lowest levels of ADH, there was a correlation of 0.69 between ADH activity and ADH CRM. None of the restriction site variants was consistently associated with the amount of ADH activity. Associations between BamHI (-7.2), the Adh polymorphism and ADH activity suggest that there are modifiers of ADH 5' to the gene. The deletion (0.2) at position -2.8 on the restriction map (Jiang & Gibson, 1991) was associated with increased levels of ADH activity in AdhS lines from China. Two unique insertions in the gene region were associated with low activity in AdhF lines and a null activity allele had a deletion removing most of exon 2. A single line with a duplication of a part of the Adh coding region and of the 5' regulatory section had relatively high ADH activity. Considering all the data, the main factor affecting ADH activity levels in populations is the frequency of AdhF.

Alcohol Dehydrogenase↗
PubMed2006

Patterns of microsatellite variation through a transition zone of a chromosomal cline in Drosophila americana.

Chromosomal rearrangements have been considered as important barriers to gene flow and were often used in the delineation of species. The original taxonomic designation of Drosophila americana americana and Drosophila americana texana is based on the presence/absence of a centric fusion between the X- and fourth chromosomes. D. a. americana presents the derived fused state, whereas Drosophila a. texana presents the freely segregating ancestral state. The degree of genetic separation between the two chromosomal forms is still controversial, with different genetic markers yielding contrasting results even when the same populations were analyzed. Using 27 polymorphic microsatellites, we re-evaluated patterns of genetic differentiation between six D. americana populations sampled through a transition zone of both chromosomal forms in the central United States. Our results clearly reject a scenario of two differentiated species forming a hybrid zone in a region of parapatry and indicate that gene flow minimizes genome-wide differentiation associated with the two chromosomal arrangements.

Animals↗
PubMed2000

Variation in body size and life history traits in Drosophila aldrichi and D. buzzatii from a latitudinal cline in eastern Australia.

Latitudinal variation in thorax and wing size traits was studied in wild-caught flies of the cactophilic Drosophila species, D. aldrichi and D. buzzatii, and their laboratory-reared progeny. The flies originated from five populations in Queensland, Australia, spanning an 800-km transect. The laboratory flies were reared at controlled densities and three temperatures, 20, 25, and 30 degrees C. We measured the same traits for the laboratory-reared flies as for the wild-caught flies, plus developmental time and viability. Latitudinal variation in wild-caught flies of both species followed a similar pattern for all linear size traits, with size generally increasing from north to south, but with flies from one intermediate locality markedly smaller. A drier environment at this locality and weather conditions immediately prior to collection, most likely explain the reduced size. Laboratory-reared D. aldrichi from this locality also were smaller than those from other localities, and had the fastest developmental time and highest viability. In laboratory-reared flies, body size traits did not show any clear trend to increase with latitude. The patterns of change with latitude were different between species, with D. aldrichi more similar in pattern to that of the natural populations. D. aldrichi had comparatively higher coefficients of variation in the laboratory-reared flies and lower viability at all temperatures. However, fluctuating asymmetry was lower in D. aldrichi in both wild-caught and laboratory-reared flies. The differences among populations of D. aldrichi for all traits were much larger than for D. buzzatii. As these differences in the laboratory-reared flies are expected to be largely genetic, they most likely reflect adaptation to specific (unknown) environmental factors that do not show linear latitudinal variation on the geographical scale studied.

Animals↗
PubMed2003

Nucleotide diversity at two phytochrome loci along a latitudinal cline in Pinus sylvestris.

Forest tree species provide many examples of well-studied adaptive differentiation, where the search for the underlying genes might be possible. In earlier studies and in our common conditions in a greenhouse, northern populations set bud earlier than southern ones. A difference in latitude of origin of one degree corresponded to a change of 1.4 days in number of days to terminal bud set of seedlings. Earlier physiological and ecological genetics work in conifers and other plants have suggested that such variation could be governed by phytochromes. Nucleotide variation was examined at two phytochrome loci (PHYP and PHYO, homologues of the Arabidopsis thaliana PHYB and PHYA, respectively) in three populations: northern Finland, southern Finland and northern Spain. In our samples of 12-15 sequences (2980 and 1156 base pairs at the two loci) we found very low nonsynonymous variation; pi was 0.0003 and 0.0002 at PHYP and PHYO loci, respectively. There was no functional differentiation between populations at the photosensory domains of either locus. The overall silent variation was also low, only 0.0024 for the PHYP locus. The low estimates of silent variation are consistent with the estimated low synonymous substitution rates between Pinus sylvestris and Picea abies at the PHYO locus. Despite the low level of nucleotide variation, haplotypic diversity was relatively high (0.42 and 0.41 for fragments of 1156 nucleotides) at the two loci.

Adaptation, Biological↗
PubMed2003

Clines and adaptive evolution in the methuselah gene region in Drosophila melanogaster.

In an effort to characterize further the patterns of selection and adaptive evolution at the methuselah locus in Drosophila species, we extended an analysis of geographical variation to include single nucleotide polymorphisms (SNPs) in adjacent genes on either side of the mth locus, and examined the molecular variation in a neighbouring methuselah paralogue (mth2). An analysis of 13 SNPs spanning a region of nearly 19 kilobases surrounding the mth locus demonstrated that a clinal pattern associated with the most common mth haplotype does not extend to adjacent gene loci, providing compelling evidence that the clinal pattern results from selection on as yet unidentified sites associated with the functional mth locus. mth2 exhibited a significant pattern of adaptive divergence among D. melanogaster, D. simulans and D. yakuba similar to that seen at mth. However, Ka : Ks ratios indicate a difference in levels of functional constraint at the two methuselah, loci with mth2 exhibiting a five- to six-fold reduction in levels of amino acid divergence relative to mth.

Amino Acid Sequence↗
PubMed1991

Bergmann's rule near the equator: latitudinal clines in body size of an Andean passerine bird.

Critical correlative support for Bergmann's ecogeographic rule is provided by symmetrical patterns of size variation in Diglossa carbonaria, a tropical passerine bird whose geographic range in the Andes Mountains of South America straddles the equator. Body size is positively correlated with latitude both north and south of the equator. Moreover, parapatric taxa that exhibit either partial (north-western Bolivia) or complete (northern Peru) reproductive isolation converge in body size. Relative uniformity in the length of the highly modified flower-piercing bill among populations of D. carbonaria that differ significantly in body size suggests that character displacement or interspecific competition is not responsible for these patterns. These findings support the hypothesis that climate, particularly temperature seasonality, is an important environmental determinant of geographic size variation in homeotherms. In addition they demonstrate that clinal variation correlated with subtle climatic gradients can occur in tropical environments.

Journal Article↗
PubMed1993

Molecular karyotype variation in Leishmania (Viannia) peruviana: indication of geographical populations in Peru distributed along a north-south cline.

Forty-one Leishmania peruviana isolates were selected along a north-south transect which crossed areas endemic for uta in three different biogeographical regions in the Peruvian Andes. The isolates were analysed by molecular karyotyping and hybridization with three chromosome-derived DNA probes. All the isolates could be distinguished from L. braziliensis by their pLb-134 hybridization patterns. However, the patterns with the other probes (pLb-168 and -22) could be used to cluster the Peruvian isolates in discrete groups (karyodemes) which varied in their level of similarity with L. braziliensis. The geographical distribution of these karyodemes supports the hypothesis that eco-graphical isolation has contributed to the heterogeneity of L. peruviana.

Animals↗
PubMedDate not supplied

A cline in the acid phosphatase1 distribution in the Iberian Peninsula.

Blood samples from autochthonous and unrelated persons were examined for acid phosphatase (ACP1) phenotypes. The subjects were 143 Spanish Basques, 118 people from León and 295 from Castile. The samples were typed using starch gels, with one surface coloured with phenolphthalein diphosphate (Na5 salt) and the other surface revealed with 4-methylumbelliferyl-dihydrogenphosphate. The gene frequencies observed are compared with those obtained by other authors.

Acid Phosphatase↗
PubMedDate not supplied

A cline for glyoxalase I allele frequencies in Italy.

A gradient of glyoxalase I allele frequencies is described in Italian populations. The association between longitude and allele frequency is assessed through simple and multiple correlation, and gene flow is suggested as a major factor in the origin of such a pattern.

Alleles↗
PubMed1976

Clines with variable migration.

The consequences of a discontinuity in the migration rate and of a geographical barrier in the habitat are studied in a diffusion model of migration and selection. The treatment is restricted to a single diallelic locus in a monoecious population in the absence of mutation and random drift. It is supposed further that migration is independent of genotype, the population density remains constant and uniform, and Hardy-Weinberg proportions obtain locally. It is shown that a discontinuity in the migration rate leads to a jump in the slope of the gene frequency, but not in the gene frequency itself, while a localized geographical barrier has precisely the opposite effect. These features of the gene frequency behavior are quantitatively related to the migration rate. The influence of the above inhomogeneities in migration on the maintenance of an allele in an environmental pocket is examined. The extent to which the critical condition for polymorphism is made less stringent by decreased migration outside the pocket and by a geographical barrier between the pocket and the rest of the habitat is evaluated.

Alleles↗
PubMed1992

A latitudinal cline in a Drosophila clock gene.

The clock gene period determines biological rhythmicity in Drosophila melanogaster and encodes a protein characterized by an alternating series of threonine-glycine pairs. The minisatellite region encoding the threonine-glycine repeat is polymorphic in length in natural Drosophila melanogaster populations. In this paper we report the geographical analysis of this polymorphism within Europe and North Africa. A robust clinal pattern is observed along a north-south axis. We suggest the possibility that the length polymorphism could be maintained by thermal selection because the threonine-glycine region has been shown to provide thermostability to the circadian phenotype.

Africa, Northern↗