In the alpine valley of Valtellina there are two Robertsonian chromosomal races of house mouse, the Poschiavo (POS: 2n= 24–26) characterized by metacentric 8.12 and acrocentrics 2 and 10 and the Upper Valtellina (UV: 2n= 22–24) characterized by metacentrics 2.8 and 10.12. The races inhabit separate villages in the valley except in Sommacologna and Sondalo, where they both occur together with hybrids. A total of 179 mice from 16 villages were typed at 13 microsatellite loci. Seven of these loci were localized close to the centromeres of chromosomes 10 and 12, with the prediction that these regions on the race‐specific chromosomes would be the most likely to experience a barrier to gene flow. The remaining six loci were localized at the telomeres of chromosomes 10 and 12 and at the centromeres of chromosomes that do not differ between the races. Substantial differences in allelic frequencies were found between the villages with POS and UV races at five of the loci at the centromeres of chromosomes 10 and 12 but at none of the other loci. These differences were not found to distinguish the two races in Sommacologna and Sondalo. Therefore, the centromeric regions of race‐specific chromosomes do appear to experience a barrier to gene flow, although this can break down under intense interbreeding between the races. These results are considered in the context of Harrison's (1990) concept of the semipermeability of hybrid zones to gene exchange and in relation to parapatric speciation.
To assess whether flies and slugs acquire strains of Campylobacter jejuni and Campylobacter coli present in local ruminant faeces.Campylobacter was cultured from flies, slugs and ruminant faeces that were collected from a single farm in Scotland over a 19-week period. The isolates were typed using multi-locus sequence typing (MLST) and compared with isolates from cattle and sheep faeces. Campylobacter jejuni and Camp. coli were isolated from 5·8% (n=155, average of 75 flies per pool) and 13·3% (n=15, average of 8·5 slugs per pool) of pooled fly and slug samples, respectively. The most common sequence type (ST) in flies was Camp. coli ST-962 (approx. 40%) regardless of the prevalence in local cattle (2·3%) or sheep (25·0%) faeces. Two positive slug pools generated the same ST that has not been reported elsewhere. Despite their low carriage rate, flies are able to acquire Campylobacter STs that are locally present, although the subset carried may be biased when compared to local source. Slugs were shown to carry a previously unreported Campylobacter ST.This study has demonstrated that flies carry viable Campylobacter and may contribute to the transfer of STs within and between groups of animals on farms. Further, they may therefore present a risk to human health via their contact with ready-to-eat foods or surfaces.
Twelve microsatellites were isolated from a partial genomic library of Ostrea edulis using (GA/TC)n and (AC/GT)n probes and were subsequently sequenced. We estimate that, on average, 12,700 (GA/TC)n and 3900 (AC/GT)n microsatellites could be found in the genome assuming a random distribution. These estimates are high enough for the construction of a saturated genetic map. Primers were designed for three microsatellite loci, and analyses of polymorphism in a wild cohort revealed that one was suitable for population genetics studies (5 alleles), while the other two were highly polymorphic (between 17 and 48 alleles) and thus were more useful for paternity testing. Mendelian inheritance was tested on two full-sib families, and significant distortions of genotypic frequencies were found, although the gametic distributions seemed to be in agreement with Mendelian expectations. We interpret this as evidence for zygotic selection.
Abstract The bluetongue (BT) vector Culicoides imicola Kieffer (Diptera: Ceratopogonidae) has undergone widespread range expansion across most of the Mediterranean basin, concomitant with the largest BT epizootic outbreaks on record. Knowledge of the substructure of this vector expansion would be useful for identifying specific source−expansion systems. To this end we analysed the haplotype diversity of the mitochondrial cytochrome oxidase I gene in 273 C. imicola from 88 Mediterranean sites and outgroups. All the C. imicola haplotypes ( n = 26) formed a single, distinct clade in comparison with haplotypes of four other species of the Imicola group from southern Africa, confirming C. imicola as a single phylospecies. Haplotype distribution showed extreme differentiation across the Mediterranean basin, with four common haplotypes each predominating in different areas. Eastern and western areas characterized by distinct BT incursions accounted for most of the molecular variance in haplotype composition. Shared common haplotypes identified one area of incursion and expansion encompassing the western half of the Mediterranean basin, with evidence of population growth, and another system encompassing Anatolian Turkey, the Aegean Islands and mainland Greece. A third area of range expansion was identified in the central Mediterranean, with a possible source in Algeria and unsampled parts of central North Africa. We conclude that the expansion of C. imicola in the Mediterranean basin consists of at least three incursions followed by expansions and that the western system experiences conditions promoting high population growth.
To monitor mammals by direct observation is often very difficult. Therefore a new technique based on DNA typing of droppings has been developed. DNA typing of otter spraints can potentially provide estimates of population size, home ranges, dispersal, genetic diversity and which species are present. This article gives a set of guidelines based on two feasibility studies on how to use the spraint DNA typing method. There are three main points. First, a sample of the study population must be typed to check that levels of genetic polymorphism are high enough for individual identification. Second, spraints must be collected and stored correctly because DNA extracted from spraints is typically of poor quality and quantity. Spraint collection should take place within 12 hours after deposition and before 10 a.m., and spraints should be stored at -20°C in a solution to stop DNA breakdown. Third, laboratory technique must be meticulous in carrying out repeat assays of the same sample and in avoiding contamination among samples. The results of the feasibility studies suggest that spraint DNA typing shows promise for monitoring of otter populations. Further progress will depend on achieving higher success rates, lower cost, and developing more highly variable microsatellites and species- specific PCR assays. DNA typing of endangered and poorly known otter species could provide important information on their distribution and status. We therefore recommend that skin, tissue or DNA samples from all endangered
This paper describes a rapid, standardised method for testing the susceptibility to bluetongue virus (BTV) of northern Palaearctic Culicoides species midges that can be used to assess the competence of both field-caught and laboratory-infected midges. The method has been used to show that Culicoides scoticus can replicate btv serotype 8 and BTV serotype 9 strains to more than 3 log(10) TCID50/midge, the first evidence of the potential of this species to transmit BTV.
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