Four wild Spanish populations of Bactrocera oleae (Gmelin) (Dipt., Tephritidae) were studied by gel electrophoresis, in order to find out their population genetic structure and the relative importance of gene flow in that structure. A great amount of genetic variability was observed. In terms of the pattern of the genetic variability in our populations, the most noticeable characteristics were the similarity of the configuration of allelic frequencies from locality to locality, the existence of exceptions and quantitative differences within that similarity, and the heterogeneity among the variable loci. Gene flow estimated from Wright's method gave a value of Nm = 8.9. However, the FST statistic in three of the loci ranged from 0.0451 to 0.0620 indicating a substantial degree of differentiation among populations (P < 0.001). The present observations seem to support the hypothesis that although gene flow could be high (Nm = 8.9), ‘natural’ selection, probably due to agricultural practices, may be the major factor responsible for the pattern of the genetic variability observed in B. oleae.
Male mating success is an important fitness component in Drosophila. The seminal fluid conveyed with the sperm inhibits the proclivity of the female to remate and reduces her fitness. Nevertheless, females may remate before they have exhausted the sperm from the first male and consequently use sperm from both males. We have studied concurrent multiple paternity (CMP) in two Drosophila melanogaster populations, from an apple orchard and a vineyard just after harvest. CMP is high in both populations, somewhat greater than 50%; but it is not significantly higher in the vineyard, where the population density is much greater than in the orchard. Population density had been thought to be an important determinant of CMP incidence. We have used four gene loci coding for enzymes as independent markers for detecting CMP.
The RAPD-PCR technique was employed to identify three endemic Spanish species of Barbus: Barbus bocagei, B. graellsii and B. sclateri, that present very similar morphologies. Using seven primers, six diagnostic bands were found in B. bocagei, 11 in B. graellsii and nine in B. sclateri. Cluster analysis of the genetic similarity values obtained from RAPD data indicated that the species B. bocagei and B. graellsii are more related to each other than to B. sclateri. 1998 The Fisheries Society of the British Isles
The tephritid Bactrocera oleae (Gmelin) is a harmful pest of olive crops; its larvae are monophagous and feed exclusively on olive fruits. Despite the economic importance of this species, important issues remain to be clarified. In the present study, the genetic variability within and among 21 populations was assessed using random amplified polymorphic DNA–PCR (seven primers). A considerable level of intraspecific diversity was detected (at population level: P = 51–70%, Hpop = 4.61; at species level: P = 63%, Hsp = 5.38) but the genetic differentiation among the populations was low (Shannon’s diversity index 14%, amova 4–8%). However, the dendrogram and principal components analysis reflect some interesting points. The most southerly of the Mediterranean populations (Tunisia) differ significantly from the remaining populations. The general results might be explained by the length of time that has elapsed as B. oleae became established in the Mediterranean region, the large effective sizes expected of its populations and gene flow among these populations. The results strongly suggest the existence of a single, large Northern Mediterranean olive fly population rather than several small, isolated populations and have a significant value in terms of control practices.
Random amplified polymorphic DNA (RAPD) markers were used to estimate the population structure and phylogenetic relationships among the eight species of the genus Barbus that inhabit the Iberian Peninsula. Ten random oligodecamers were used to amplify DNA from 232 fish sampled from 15 populations. A total of 270 markers were detected that revealed low levels of genetic variability. The conclusions of cluster analysis indicate two main branches and three welldifferentiated groups: north-eastern, Mediterranean and
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