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G Mahy

Publications and source records attributed to G Mahy.

6 recordsLinked to original sources
PubMed2000

Allozyme evidence for genetic autopolyploidy and high genetic diversity in tetraploid cranberry, Vaccinium oxycoccos (Ericaceae).

Polyploidy has been important in the evolution of angiosperms and may significantly affect population genetic diversity and structure. Nineteen isoenzyme loci were studied in diploid and tetraploid populations of Vaccinium oxycoccos (Ericaceae), and the results are compared with data previously reported for the related V. macrocarpon. Diploid V. oxycoccos and V. macrocarpon were readily discriminated based on their allozymic variation. No evidence for fixed heterozygosity was found in tetraploid V. oxycoccos. In contrast, all polymorphic loci exhibited both balanced and unbalanced heterozygotes, with some individuals exhibiting a pattern consistent with the presence of three alleles. These results support an autopolyploid origin for tetraploid V. oxycoccos. However, tetraploid V. oxycoccos possessed a suite of alleles not found in diploid V. oxycoccos; half of these alleles were shared with V. macrocarpon. This suggests that autotetraploid V. oxycoccos may have undergone hybridization with V. macrocarpon or that the autotetraploid retained the genetic variation present in an ancestral diploid species. Following theoretical expectations, proportion of polymorphic loci, mean number of alleles, and observed heterozygosity were significantly higher for the autotetraploid than for the diploid. Mean inbreeding (F(IS)) was similar for diploid and tetraploid V. oxycoccos. The latter exhibited population differentiation (F(ST)) exceeding both diploid species.

Journal Article↗
PubMed1999

Patterns of allozymic variation within calluna vulgaris populations at seed bank and adult stages

We investigated the spatial genetic structure within and between two plots of Calluna vulgaris and the extent to which the soil seed bank differed genetically from adults at seven allozyme loci. Averaged over the two plots, the seed bank and adult populations contained very similar levels of genetic diversity. Moreover, seeds contained in a single soil core (100 cm3) exhibited similar mean allozyme diversity to the surrounding adult population, indicating that the seed bank preserves genetic diversity at a very local scale. Few differences in allelic frequencies were found between the seed bank and its surrounding adult population in each plot. Mean GST indicated a lack of differentiation between the two plots at adult (GST = 0.008) and seed bank (GST = 0.002) stages. Low interplot differentiation is consistent with the outcrossing mating system of the population (tm = 0.91 in one plot) and its history of human disturbance. In contrast, spatial autocorrelation analysis of adults indicated a genetic structure at a very local scale, with positive autocorrelation for all alleles below 2 m in one plot and with a pattern of positive autocorrelation below 8 m in the two plots. Current limitation to seed dispersal rather than spatial extension of clones is thought to be responsible for local genetic structure.

Journal Article↗
PubMed1999

Allozyme variation and genetic structure of calluna vulgaris (heather) populations in scotland: the effect of postglacial recolonization

Recent fragmentation of populations as well as historical postglacial recolonization may have significantly affected the population genetic diversity of temperate plant species. Regional allozymic variability was measured at seven loci within and among 12 populations of Calluna vulgaris in the previously glaciated region of Scotland. These results were compared with existing data on south-western continental populations. Low genetic differentiation (FST = 0.024) and lack of consistent geographical pattern were found at the regional level among Scottish populations, implying a high rate of gene flow (Nm = 10.2), probably favoured by the nearly continuous range of C. vulgaris across Scotland and characteristics of the Scottish environment. Scottish populations possessed lower mean allozymic diversity (PLP = 40.48, A = 1.95, He = 0.133) than populations from all the continental regions investigated previously. Belgian populations were genetically more closely related to Scottish than to other continental populations. These last two findings are interpreted with regard to the evolutionary history of the species revealed by palynological data.

Journal Article↗
PubMed1980

Suicide and parasuicide in Barbados, 1974-1978.

This paper examines all the cases of suicide and parasuicide (non-fatal self-destructive acts) which took place on the Caribbean island of Barbados between 1974 and 1978. There were two females and 18 males who committed suicide in that period, and 14 of them were below age 44. There were 250 individuals who had attempted suicide for the first time, with a male to female ratio of 1:2.33. Most of the parasuicides were young and female, and the phenomenon is increasing. Health care officials on the island would seem to be legitimately unconcerned about the low suicide rates. However, the increasing parasuicide numbers may require more organized psychiatric care to meet the needs of this subgroup of the island's population.

Adolescent↗