Ex situ Diet Influences the Bacterial Community Associated with the Skin of Red-Eyed Tree Frogs (Agalychnis callidryas)

Amphibians support symbiotic bacterial communities on their skin that protect against a range of infectious pathogens, including the amphibian chytrid fungus. The conditions under which amphibians are maintained in captivity (e.g. diet, substrate, enrichment) in ex situ conservation programmes may affect the composition of the bacterial community. In addition, ex situ amphibian populations may support different bacterial communities in comparison to in situ populations of the same species. This could have implications for the suitability of populations intended for reintroduction, as well as the success of probiotic bacterial inoculations intended to provide amphibians with a bacterial community that resists invasion by the chytrid fungus. We aimed to investigate the effect of a carotenoid-enriched diet on the culturable bacterial community associated with captive red-eyed tree frogs (Agalychnis callidryas) and make comparisons to bacteria isolated from a wild population from the Chiquibul Rainforest in Belize. We successfully showed carotenoid availability influences the overall community composition, species richness and abundance of the bacterial community associated with the skin of captive frogs, with A. callidryas fed a carotenoid-enriched diet supporting a greater species richness and abundance of bacteria than those fed a carotenoid-free diet. Our results suggest that availability of carotenoids in the diet of captive frogs is likely to be beneficial for the bacterial community associated with the skin. We also found wild A. callidryas hosted more than double the number of different bacterial species than captive frogs with very little commonality between species. This suggests frogs in captivity may support a reduced and diverged bacterial community in comparison to wild populations of the same species, which could have particular relevance for ex situ conservation projects.     

Effects of Age and Region on Fecal Microflora in Elderly Subjects Living in Bama,Guangxi, China

Intestinal microflora analysis was performed on 52 healthy elderly subjects of different ages and in different regions in Bama County, Guangxi, China. The participants were assigned to three groups depending on their age and location: longevous (group M; mean age = 98 years; n = 21); rural younger elderly (group S; mean age = 70 years; n = 18); and urban elderly (group C; mean age = 82 years; n = 13). Ten groups of bacteria were quantified using real-time PCR. Age-related differences were observed in the number of Clostridium coccoides–Eubacterium rectale—there were more in longevous participants. Region affected the numbers of Bacteroides—Prevotella and Clostridium perfringens subgroup, and longevous participants had significantly more of the two bacterial groups than urban elderly participants. Region-related effects were also observed for the relative abundance of E. coli, and rural elderly participants had a lower proportion. Both age and regional effects were observed in the amount of total bacteria, and longevous participants had higher numbers than urban elderly participants. A significantly higher proportion of lactobacilli was observed in rural younger elderly participants than urban elderly participants, but independent age or regional effects did not contribute to this difference. This study suggests that age and region can affect the intestinal microflora of elderly people.     

The diversity and host interactions of Propionibacterium acnes bacteriophages on human skin

The viral population, including bacteriophages, is an important component of the human microbiota, yet is poorly understood. We aim to determine whether bacteriophages modulate the composition of the bacterial populations, thus potentially playing a role in health or disease. We investigated the diversity and host interactions of the bacteriophages of Propionibacterium acnes, a major human skin commensal implicated in acne pathogenesis. By sequencing 48 P. acnes phages isolated from acne patients and healthy individuals and by analyzing the P. acnes phage populations in healthy skin metagenomes, we revealed that P. acnes phage populations in the skin microbial community are often dominated by one strain. We also found phage strains shared among both related and unrelated individuals, suggesting that a pool of common phages exists in the human population and that transmission of phages may occur between individuals. To better understand the bacterium–phage interactions in the skin microbiota, we determined the outcomes of 74 genetically defined Propionibacterium strains challenged by 15 sequenced phages. Depending on the Propionibacterium lineage, phage infection can result in lysis, pseudolysogeny, or resistance. In type II P. acnes strains, we found that encoding matching clustered regularly interspaced short palindromic repeat spacers is insufficient to confer phage resistance. Overall, our findings suggest that the prey–predator relationship between bacteria and phages may have a role in modulating the composition of the microbiota. Our study also suggests that the microbiome structure of an individual may be an important factor in the design of phage-based therapy.     

Effect of carbon addition and predation on acetate-assimilating bacterial cells in groundwater

Groundwater microbial community dynamics are poorly understood due to the challenges associated with accessing subsurface environments. In particular, microbial interactions and their impact on the subsurface carbon cycle remain unclear. In the present project, stable isotope probing with uniformly labeled [¹³C]-acetate was used to identify metabolically active and inactive bacterial populations based on their ability to assimilate acetate and/or its metabolites. Furthermore, we assessed whether substrate availability (bottom–up control) or grazing mortality (top–down control) played a greater role in shaping bacterial community composition by separately manipulating the organic carbon supply and the protozoan grazer population. A community fingerprinting technique, terminal restriction fragment length polymorphism, revealed that the bacterial community was not affected by changes in acetate availability but was significantly altered by the removal of protozoan grazers. In silico identification of terminal restriction fragments and 16S rRNA gene sequences from clone libraries revealed a bacterial community dominated by Proteobacteria, Firmicutes , and Bacteroidetes . Elucidation of the factors that structure the bacterial community will improve our understanding of the bacterial role in the carbon cycle of this important subterranean environment.     

Carriage of antibiotic-resistant bacteria in urban versus rural wild boars

The Western European population of wild boar (Sus scrofa) has increased its distribution over the past several decades, and some populations have colonized areas strongly influenced by human activity. Wild boars are known carriers of antibiotic-resistant bacteria acquired from the environment, and urban populations of wild boars may be more exposed than their rural counterparts. In this work, we compared the frequency of antibiotic resistance in indicator bacteria (Escherichia coli, Enterococcus faecalis, Enterococcus faecium) isolated from urban wild boars with that from rural wild boars in NE Spain. We further assessed whether bacterial isolates from the urban wild boars had a higher probability of showing antibiotic resistance when their host was highly associated to urban features. Seventy-two and 100 bacterial isolates from urban and rural habitat, respectively, were screened for antibiotic resistance against a set of antibiotics (13 per bacterial species). We found a significantly higher frequency of E. faecium showing resistance to tetracycline (70.0% vs 36.4%) and high-level resistance to streptomycin (30.0% vs 4.5%) in urban wild boars compared to rural wild boars (p?<?0.05). E. faecalis was more frequently resistant to trimethoprim in urban than rural wild boars (33.3% vs 0.0%, p?<?0.05). In isolates from urban origin, 55.6% of the likelihood of detecting antibiotic resistance depended only on the bacterial species, being more likely in the enterococci than in E. coli. These results suggest that urban wild boars may be more exposed to certain antibiotic-resistant bacteria or antibiotic resistance genes that they may acquire from the urban environment, although implications are uncertain.     

The influence of urea feeding on the bacterial and archaeal community in the forestomach of collared peccary (Artiodactyla, Tayassuidae)

Aims:  This study was carried out to test whether bacterial and archaeal populations, and products of fermentation in each compartment of collared peccary stomach, vary significantly with urea feeding. Bacteria and archaeal population variation among the four stomach compartments were also compared.
Methods and Results:  Archaeal and bacterial communities in the forestomach of four individuals per treatment – peccaries fed diets with and without urea – were analysed at molecular level using PCR followed by denaturing gradient gel electrophoresis. Volatile fatty acids profiles in the three different compartments of the forestomach were also compared. The bacterial community composition varied considerably among each compartment and with urea provision, but no variation was observed between archaeal populations. Differences in bacterial communities between treatments – with and without urea – were greater than amongst stomach compartments. The acetate: propionate proportion decreased with urea provision in diet. Some differences in bacterial but not archaeal community composition were observed in each compartment of the collared peccary forestomach.
Conclusions:  There are some differences in bacterial but not archaeal populations in each compartment of collared peccary stomach. Use of urea in the diet of peccary can substantially modify the profile of volatile fatty acids released in its forestomach, but does not influence the archaeal community composition. Urea has an important effect on bacterial population DGGE profile present in the peccary's forestomach.
Significance and Impact of the Study:  These results demonstrate the ability of the collared peccary to use urea as source of nonprotein nitrogen, and confirm a hypothesis that the collared peccary has a digestive physiology more similar to ruminant than nonruminant animals.     

Anthropogenic environments exert variable selection on cranial capacity in mammals

It is thought that behaviourally flexible species will be able to cope with novel and rapidly changing environments associated with human activity. However, it is unclear whether such environments are selecting for increases in behavioural plasticity, and whether some species show more pronounced evolutionary changes in plasticity. To test whether anthropogenic environments are selecting for increased behavioural plasticity within species, we measured variation in relative cranial capacity over time and space in 10 species of mammals. We predicted that urban populations would show greater cranial capacity than rural populations and that cranial capacity would increase over time in urban populations. Based on relevant theory, we also predicted that species capable of rapid population growth would show more pronounced evolutionary responses. We found that urban populations of two small mammal species had significantly greater cranial capacity than rural populations. In addition, species with higher fecundity showed more pronounced differentiation between urban and rural populations. Contrary to expectations, we found no increases in cranial capacity over time in urban populations—indeed, two species tended to have a decrease in cranial capacity over time in urban populations. Furthermore, rural populations of all insectivorous species measured showed significant increases in relative cranial capacity over time. Our results provide partial support for the hypothesis that urban environments select for increased behavioural plasticity, although this selection may be most pronounced early during the urban colonization process. Furthermore, these data also suggest that behavioural plasticity may be simultaneously favoured in rural environments, which are also changing because of human activity.     

The Relative Contribution of Immigration or Local Increase for Persistence of Urban Schistosomiasis in Salvador,Bahia, Brazil

Urbanization is increasing across the globe, and diseases once considered rural can now be found in urban areas due to the migration of populations from rural endemic areas, local transmission within the city, or a combination of factors. We investigated the epidemiologic characteristics of urban immigrants and natives living in a neighborhood of Salvador, Brazil where there is a focus of transmission of Schistosoma mansoni. In a cross-sectional study, all inhabitants from 3 sections of the community were interviewed and examined. In order to determine the degree of parasite differentiation between immigrants and the native born, S. mansoni eggs from stools were genotyped for 15 microsatellite markers. The area received migrants from all over the state, but most infected children had never been outside of the city, and infected snails were present at water contact sites. Other epidemiologic features suggested immigration contributed little to the presence of infection. The intensity and prevalence of infection were the same for immigrants and natives when adjusted for age, and length of immigrant residence in the community was positively associated with prevalence of infection. The population structure of the parasites also supported that the contribution from immigration was small, since the host-to-host differentiation was no greater in the urban parasite population than a rural population with little distant immigration, and there had been little differentiation in the urban population over the past 7 years. Public health efforts should focus on eliminating local transmission, and once eliminated, reintroduction from distant migration is unlikely.     

Distinct cutaneous bacterial assemblages in a sampling of South American Amerindians and US residents

The human skin harbors complex bacterial communities. Prior studies showing high inter-individual variation focused on subjects from developed countries. We therefore compared cutaneous bacterial communities of Amerindians in the Venezuelan Amazon with subjects in the United States. Forearm skin specimens were studied from healthy Amerindians in Platanillal village in Amazonas State, and from healthy persons in New York and Colorado. All skin sampling used similar swab/buffer techniques. Multiplexed V2-targeted 16S rRNA gene pyrosequencing yielded high quality sequences from 112 samples. The results show 20 phyla, with three (Proteobacteria, Firmicutes, Actinobacteria) predominating. US residents and Venezuelan Amerindians had significantly different forearm skin bacterial community compositions, with United States dominated by Propionibacterium. Among the Amerindians, there was a deep split based on bacterial community membership, with 30 and 42 samples, respectively, falling into each of the two groups, not associated with age, gender, or body mass index. One Amerindian group had diversity similar to the United States, but was dominated by Staphylococcus rather than Propionibacterium. The other Amerindian group was significantly more diverse and even than the US or the other Amerindian group, and featured a broad range of Proteobacteria. The results provide evidence that ethnicity, lifestyle and/or geography are associated with the structure of human cutaneous bacterial communities.     

Genetic structure in urban and rural populations of Apodemus agrarius in Poland

The aims of this study were (i) to determine the genetic variability of the striped field mouse (Apodemus agrarius Pallas, 1771) population in the area of the Warsaw conurbation and the genetic differentiation among local populations of this species within the city, and (ii) to examine the influence of the degree of isolation on the appearance of such genetic structure. Comparison of the genetic structure of the urban population with that of populations inhabiting rural areas was intended to shed light on the depth of genetic changes in this species caused by life in an urban environment. Eight microsatellite loci were used for genotyping and these molecular analyses were successfully performed for 269 individuals. Genetic differentiation (F_ST) was much higher in the case of the urban population. STRUCTURE analysis indicated that this population was subdivided into several local populations, whereas for the rural locations, the highest likelihood was for a single genetic group (one genetically unstructured population). Moreover, in contrast to the rural population, we found no isolation by distance in the urban population. Despite clear subdivision of the urban population, the level of genetic variability was very similar in both analyzed groups. Our findings indicate the occurrence of an advanced process of differentiation of the urban population by microevolution, whereas populations from rural locations displayed very small and mainly insignificant genetic differentiation. Urban local populations, situated near the city borders or close to the natural ecological corridor (banks of the Vistula River), showed higher genetic variability and were less differentiated from populations inhabiting rural sites than from local populations in the city centre. These results provide support for the importance of ecological corridors in preserving the genetic variability of the urban striped field mouse population.     

Insights into Nasal Carriage of Staphylococcus aureus in an Urban and a Rural Community in Ghana

The epidemiology of Staphylococcus aureus in the community in Ghana was never investigated prior to this study. The aims of the study were: i) to assess prevalence of nasal S. aureus carriage in Ghanaian people living in an urban and a rural area, and ii) to identify phenotypic and genotypic traits of strains isolated from the two communities. Nasal swabs were collected from healthy individuals living in an urban community situated in the suburb of the capital city, Accra (n = 353) and in a rural community situated in the Dangme-West district (n = 234). The overall prevalence of nasal carriage was 21% with a significantly higher prevalence in the urban (28%) than in the rural community (11%) (p<0.0001). The levels of antimicrobial resistance were generally low (<5%) except for penicillin (91%) and tetracycline (25%). The only two (0.3%) MRSA carriers were individuals living in the urban area and had been exposed to hospitals within the last 12 months prior to sampling. Resistance to tetracycline (p = 0.0009) and presence of Panton-Valentine leukocidin (PVL) gene (p = 0.02) were significantly higher among isolates from the rural community compared to isolates from the urban community. Eleven MLST clonal complexes (CC) were detected based on spa typing of the 124 S. aureus isolates from the two communities: CC8 (n = 36), CC152 (n = 21), CC45 (n = 21), CC15 (n = 18), CC121 (n = 6), CC97 (n = 6), CC30 (n = 5), CC5 (n = 5), CC508 (n = 4), CC9 (n = 1), and CC707 (n = 1). CC8 and CC45 were less frequent in the rural area than in the urban area (p = 0.02). These results reveal remarkable differences regarding carriage prevalence, tetracycline resistance, PVL content and clonal distribution of S. aureus in the two study populations. Future research may be required to establish whether such differences in nasal S. aureus carriage are linked to socio-economic differences between urban and rural communities in this African country.     

Differences in measures of boldness even when underlying behavioral syndromes are present in two populations of the song sparrow (<Emphasis Type="Italic">Melospiza melodia</Emphasis>)

One commonly studied behavioral syndrome is the correlation between aggression and boldness. Studies in song sparrows (M. melodia) have found greater aggression and boldness in urban populations and a correlation between aggression and boldness in rural populations, but not within urban populations. In previous studies, boldness was measured as flight initiation distance (FID), which may reflect habituation by urban birds to human presence. In this study, we measured boldness using playbacks of heterospecific alarm calls and investigated whether higher boldness is a general trait of urban birds and whether the same pattern of correlations between aggression and boldness would be seen. We conducted trials involving FID, alarm call playbacks and conspecific song playbacks on 25 birds from both an urban and a rural site. The results showed that urban birds were bolder, as measured by FID and response to alarm calls. Boldness and aggression were correlated in rural birds with each method of measuring boldness but were correlated in urban birds only when using alarm call playbacks. Our results suggest that a behavioral syndrome exists in both urban and rural populations but that urban birds are able to decrease their response to human disturbance.     

The host species affects the microbial community in the goat rumen

AIMS: This study was carried out to determine whether bacterial and ciliate populations in goat rumen vary significantly between different goat species living in the same environment. METHODS AND RESULTS: Bacterial and ciliate communities in the rumen of three goat species were analysed at the molecular level using denaturing gradient gel electrophoresis. The microbial community varied considerably among goats living in the same environment. Interspecies variation in the bacterial population was noticeably greater than intraspecies variation. In contrast, there was considerable variation in the ciliate population among goats within the same species, and intraspecies similarities were no greater than those observed across species. CONCLUSIONS: Because environmental factors and diets were identical for all goats, differences in bacterial populations reflect species-specific differences in rumen microbes. SIGNIFICANCE AND IMPACT OF THE STUDY: Factors related to the host species have an important effect on determining the bacterial composition in the goat rumen.     

Cutaneous Bacteria of the Redback Salamander Prevent Morbidity Associated with a Lethal Disease

Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is an infectious disease that causes population declines of many amphibians. Cutaneous bacteria isolated from redback salamanders, Plethodon cinereus, and mountain yellow-legged frogs, Rana muscosa, inhibit the growth of Bd in vitro. In this study, the bacterial community present on the skin of P. cinereus individuals was investigated to determine if it provides protection to salamanders from the lethal and sub-lethal effects of chytridiomycosis. When the cutaneous bacterial community was reduced prior to Bd exposure, salamanders experienced a significantly greater decrease in body mass, which is a symptom of the disease, when compared to infected individuals with a normal bacterial community. In addition, a greater proportion of infected individuals with a reduced bacterial community experienced limb-lifting, a behavior seen only in infected individuals. Overall, these results demonstrate that the cutaneous bacterial community of P. cinereus provides protection to the salamander from Bd and that alteration of this community can change disease resistance. Therefore, symbiotic microbes associated with this species appear to be an important component of its innate skin defenses.     

The short-term effects of surface soil disturbance on soil bacterial community structure at an experimental site near Scott Base, Antarctica

Humans are visiting Antarctica in increasing numbers, and the ecological effect of rapid soil habitat alteration due to human-induced physical disturbance is not well understood. An experimental soil disturbance trial was set up near Scott Base on Ross Island, to investigate the immediate and short-term changes to bacterial community structure, following surface soil disturbance. Three blocks, each comprising an undisturbed control, and an area disturbed by removing the top 2 cm of soil, were sampled over a time series (0, 7, 14, 21, and 35 days), to investigate changes to bacterial community structure using DNA profiling by terminal restriction fragment length polymorphism. The simulated disturbance did not cause any major shifts in the structure of the bacterial communities over the 35-day sampling period. Ordination showed that the bacterial community composition correlated strongly with soil EC (R ² = 0.55) and soil pH (R ² = 0.67), rather than the removal of the top 2 cm of surface material. Although the replicate blocks were visually indistinguishable from one another, high local spatial variability of soil chemical properties was found at the study site and different populations of bacterial communities occurred within 2 m of one another, within the same landscape unit. Given the current knowledge of the drivers of bacterial community structure, that is, soil EC, soil pH, and soil moisture content, a follow-up investigation incorporating DNA and RNA-based analyses over a time frame of 2–3 years would lead to a greater understanding of the effects of soil disturbance on bacterial communities.     

Effect of Sheep Urine Deposition on the Bacterial Community Structure in an Acidic Upland Grassland Soil

The effect of the addition of synthetic sheep urine (SSU) and plant species on the bacterial community composition of upland acidic grasslands was studied using a microcosm approach. Low, medium, and high concentrations of SSU were applied to pots containing plant species typical of both unimproved (Agrostis capillaris) and agriculturally improved (Lolium perenne) grasslands, and harvests were carried out 10 days and 50 days after the addition of SSU. SSU application significantly increased both soil pH (P < 0.005), with pH values ranging from pH 5.4 (zero SSU) to pH 6.4 (high SSU), and microbial activity (P < 0.005), with treatment with medium and high levels of SSU displaying significantly higher microbial activity (triphenylformazan dehydrogenase activity) than treatment of soil with zero or low concentrations of SSU. Microbial biomass, however, was not significantly altered by any of the SSU applications. Plant species alone had no effect on microbial biomass or activity. Bacterial community structure was profiled using bacterial automated ribosomal intergenic spacer analysis. Multidimensional scaling plots indicated that applications of high concentrations of SSU significantly altered the bacterial community composition in the presence of plant species but at different times: 10 days after application of high concentrations of SSU, the bacterial community composition of L. perenne-planted soils differed significantly from those of any other soils, whereas in the case of A. capillaris-planted soils, the bacterial community composition was different 50 days after treatment with high concentrations of SSU. Canonical correspondence analysis also highlighted the importance of interactions between SSU addition, plant species, and time in the bacterial community structure. This study has shown that the response of plants and bacterial communities to sheep urine deposition in grasslands is dependent on both the grass species present and the concentration of SSU applied, which may have important ecological consequences for agricultural grasslands.     

Analysis of bacterial communities in rhizosphere soil of continuously cropped healthy and diseased konjac

The bacterial community and diversity in healthy and diseased konjac rhizosphere soils with different ages of continuous cropping were investigated using next-generation sequencing. The results demonstrated that the number of years of continuous cropping significantly altered soil bacterial community and diversity. Soil bacterial Shannon diversity index and Chao 1 index decreased with the increasing cropping years of konjac. After 1 year of cropping, the soil exhibited the highest bacterial relative abundance and diversity. Of the 44 bacterial genera (relative abundance ratio of genera greater than 0.3%), 14 were significantly affected by the duration of continuous cropping and plant status. With increasing continuous cropping, Alicyclobacillus decreased, while Achromobacter, Lactobacillus, Kaistobacter, Rhodoplanes increased after 3 years continuous cropping. Continuous cropping altered the structure and composition of the soil bacterial community, which led to the reduction in the beneficial bacteria and multiplication of harmful bacteria. These results will improve our understanding of soil microbial community regulation and soil health maintenance in konjac farm systems.     

Living in the city: urban environments shape the evolution of a native annual plant

Urban environments are warmer, have higher levels of atmospheric CO₂ and have altered patterns of disturbance and precipitation than nearby rural areas. These differences can be important for plant growth and are likely to create distinct selective environments. We planted a common garden experiment with seeds collected from natural populations of the native annual plant Lepidium virginicum, growing in five urban and nearby rural areas in the northern United States to determine whether and how urban populations differ from those from surrounding rural areas. When grown in a common environment, plants grown from seeds collected from urban areas bolted sooner, grew larger, had fewer leaves, had an extended time between bolting and flowering, and produced more seeds than plants grown from seeds collected from rural areas. Interestingly, the rural populations exhibited larger phenotypic differences from one another than urban populations. Surprisingly, genomic data revealed that the majority of individuals in each of the urban populations were more closely related to individuals from other urban populations than they were to geographically proximate rural areas – the one exception being urban and rural populations from New York which were nearly identical. Taken together, our results suggest that selection in urban environments favors different traits than selection in rural environments and that these differences can drive adaptation and shape population structure.     

Archaeal and Bacterial Communities Associated with the Surface Mucus of Caribbean Corals Differ in Their Degree of Host Specificity and Community Turnover Over Reefs

Comparative studies on the distribution of archaeal versus bacterial communities associated with the surface mucus layer of corals have rarely taken place. It has therefore remained enigmatic whether mucus-associated archaeal and bacterial communities exhibit a similar specificity towards coral hosts and whether they vary in the same fashion over spatial gradients and between reef locations. We used microbial community profiling (terminal-restriction fragment length polymorphism, T-RFLP) and clone library sequencing of the 16S rRNA gene to compare the diversity and community structure of dominant archaeal and bacterial communities associating with the mucus of three common reef-building coral species (Porites astreoides, Siderastrea siderea and Orbicella annularis) over different spatial scales on a Caribbean fringing reef. Sampling locations included three reef sites, three reef patches within each site and two depths. Reference sediment samples and ambient water were also taken for each of the 18 sampling locations resulting in a total of 239 samples. While only 41% of the bacterial operational taxonomic units (OTUs) characterized by T-RFLP were shared between mucus and the ambient water or sediment, for archaeal OTUs this percentage was 2-fold higher (78%). About half of the mucus-associated OTUs (44% and 58% of bacterial and archaeal OTUs, respectively) were shared between the three coral species. Our multivariate statistical analysis (ANOSIM, PERMANOVA and CCA) showed that while the bacterial community composition was determined by habitat (mucus, sediment or seawater), host coral species, location and spatial distance, the archaeal community composition was solely determined by the habitat. This study highlights that mucus-associated archaeal and bacterial communities differ in their degree of community turnover over reefs and in their host-specificity.     

Genetic variation in rural and urban populations of Epipactis helleborine (L.) Crantz. (Orchidaceae) in Britain

Genetic variation in Epipactis helleborine in the British Isles was assessed using starch gel electrophoresis of isozymes; 273 individuals were sampled from 13 populations and examined for genetic variation using eight enzyme systems encoded for by 13 loci. Overall, 46% of the loci examined were polymorphic, with an average of 1.69 alleles per locus. Within populations, a mean of 33% of the loci were polymorphic, with a mean number of 1.46 alleles per locus. Levels of genetic variation were compared between urban and well established rural populations to assess the genetic consequences of colonization of the urban sites. The average levels of genetic variation detected in urban populations were lower than that found in rural populations, although there was a much greater range of variation among the urban populations. Large urban populations actually have patterns of variation similar to rural populations and show evidence of multiple founders. This indicates that the high dispersibility of Epipactis seeds can in some cases overcome the predicted loss of genetic variation associated with founder effects during colonization. Small urban populations, however, show significantly lower levels of genetic variation compared with these large urban populations and the rural populations, and it seems likely that this is attributable to single founding events and/or genetic drift.