A Y chromosome census of the British Isles

The degree of population replacement in the British Isles associated with cultural changes has been extensively debated. Recent work has demonstrated that comparisons of genetic variation in the British Isles and on the European Continent can illuminate specific demographic processes in the history of the British Isles. For example, Wilson et al. used the similarity of Basque and Celtic Y chromosomes to argue for genetic continuity from the Upper Palaeolithic to the present in the paternal history of these populations (see also ). Differences in the Y chromosome composition of these groups also suggested genetic signatures of Norwegian influence in the Orkney Islands north of the Scottish mainland, an important center of Viking activities between 800 and 1300 A.D. More recently, Weale et al. argued for substantial Anglo-Saxon male migration into central England based on the analysis of eight British sample sets collected on an east-west transect across England and Wales. To provide a more complete assessment of the paternal genetic history of the British Isles, we have compared the Y chromosome composition of multiple geographically distant British sample sets with collections from Norway (two sites), Denmark, and Germany and with collections from central Ireland, representing, respectively, the putative invading and the indigenous populations. By analyzing 1772 Y chromosomes from 25 predominantly small urban locations, we found that different parts of the British Isles have sharply different paternal histories; the degree of population replacement and genetic continuity shows systematic variation across the sampled areas.     

Temporal and spatial patterns in the recruitment of Gibbula umbilicalis

Size/frequency samples have been taken from populations of the trochid gastropod Gibbula umbilicalis at a number of sites around the British Isles each year since 1978. In the North of Scotland, close to the limit of the species distribution, recruitment was generally poor and populations were sparse and dominated by large old individuals. While such poor recruitment may reflect the low density of adults and the shortage of nursery areas, a distinct temporal pattern of recruitment was also evident. At the start of our study, the majority of sites had population structures biased towards young animals implying that conditions for the settlement of larvae or their subsequent survival had been favourable over a wide area. In the years that followed only the enclosed Loch Eriboll regularly received substantial recruitment. Further to the south, in Wales and S.W. England, recruitment was usually more regular, populations were more dense and individuals smaller.     

Contrasting Patterns of Genetic Differentiation among Blackcaps (Sylvia atricapilla) with Divergent Migratory Orientations in Europe

Migratory divides are thought to facilitate behavioral, ecological, and genetic divergence among populations with different migratory routes. However, it is currently contentious how much genetic divergence is needed to maintain distinct migratory behavior across migratory divides. Here we investigate patterns of neutral genetic differentiation among Blackcap (Sylvia atricapilla) populations with different migratory strategies across Europe. We compare the level of genetic divergence of populations migrating to southwestern (SW) or southeastern (SE) wintering areas with birds wintering in the British Isles following a recently established northwesterly (NW) migration route. The migratory divide between SW and SE wintering areas can be interpreted as a result of a re-colonization process after the last glaciation. Thus we predicted greater levels of genetic differentiation among the SW/SE populations. However, a lack of genetic differentiation was found between SW and SE populations, suggesting that interbreeding likely occurs among Blackcaps with different migratory orientations across a large area; therefore the SW/SE migratory divide can be seen as diffuse, broad band and is, at best, a weak isolating barrier. Conversely, weak, albeit significant genetic differentiation was evident between NW and SW migrants breeding sympatrically in southern Germany, suggesting a stronger isolating mechanism may be acting in this population. Populations located within/near the SW/SE contact zone were the least genetically divergent from NW migrants, confirming NW migrants likely originated from within the contact zone. Significant isolation-by-distance was found among eastern Blackcap populations (i.e. SE migrants), but not among western populations (i.e. NW and SW migrants), revealing different patterns of genetic divergence among Blackcap populations in Europe. We discuss possible explanations for the genetic structure of European Blackcaps and how gene flow influences the persistence of divergent migratory behaviors.     

A comparison of the deep-water demersal fish assemblages of the Rockall Trough and Porcupine Seabight, eastern North Atlantic: continental slope to rise

Fishery surveys of the continental slope to the west of the British Isles have shown quite marked differences between areas in both the proportion and abundance of marketable or potentially marketable species. In general, the northern slopes lying to the west of Scotland were considered to have a greater potential for exploitation than the southern slopes off Ireland. Subsequent detailed studies of a northern (Rockall Trough) and a southern slope area (Porcupine Seabight) sampled the demersal fish fauna using a Granton trawl fished on paired warps to depths of 1200 m, and a semi-balloon trawl fished on a single warp to depths of about 3000 m. The Granton trawl catches differed significantly between the two areas, especially at the greatest depths fished. The semi-balloon trawl catches did not differ between the areas. This slower trawl was poor at catching large, mobile species and efficient in the capture of the deep-waler eel Synaphobranchus kaupi. This eel was numerically dominant over the mid to lower slope and probably accounts for much of the similarity between areas at these depths.     

Taxonomic notes on Cheilothela (Lindb.) Broth. and Dicranella (C. Muell.) Schimp.

Abstract

The widespread occurrence of a number of bryophytes on British saltmarshes is reported. The communities in which bryophytes are most frequently found are discussed. These communities are more common on marshes on the west coast of Britain. Differences between moss assemblages on salt marshes in England and Wales and in Scotland are emphasised and the greater range of habitat preference demonstrated by Grimmia maritima in Scotland is commented upon.     

Red and sika deer in the British Isles,current management issues and management policy

The red deer (Cervus elaphus) is one of the most widely distributed species of deer in Europe. Due to its economic value as game species or its negative impacts on forestry, agriculture and conservation areas, most populations are currently managed, with strategies and intensity of the management varying between countries. In Britain, and less certainly in Ireland, red deer have been continuously present since the end of the last glaciation and constitute the largest population of red deer in Europe. Although they thrived in the past when forests were abundant, the current distribution of red deer in the British Isles is uneven, with the largest numbers being found in Scotland and few and more localised populations in England, Wales and the Republic of Ireland. In the British Isles, as in many other parts of Europe, there is a long history of man interacting with deer populations including local extinctions, multiple translocations and introductions of exotic species of deer. Among introduced exotic species of deer, the Japanese sika (Cervus nippon) is the one of most concern. After introduction of small numbers at multiple locations in Britain and Ireland from 1860 onwards, sika have increased in population number and range in areas with good forest cover, and where they overlap with red deer there is a risk of hybridisation. Due to recent increases in numbers and range of red and sika deer, both species pose a range of management challenges which are not easy to solve. In this review we summarise the history and status of these two species in Great Britain and Ireland, describe current management and discuss management options for the future.     

The status of the otter (Lutra lutra) in the British Isles

National field surveys for otters were carried out between 1977 and 1981. The species is apparently absent from large areas of England, although healthy populations still occur in the south-west. In many other areas, populations are isolated and fragmented and there is some evidence for continuing declines. In Wales the otter is rare or absent from the south and parts of the north. Healthy populations are present in the Highland Region of Scotland, on the north and west coasts and in the islands but there is evidence of a decline in the south and east-central lowlands. Otters are widespread and common in Ireland which sustains the best of the known populations in Europe.
Pollution by pesticides probably caused the initial rapid decline of the species but habitat destruction is increasingly important and where habitat is poor, human disturbance assumes greater significance. There is no evidence of competition with mink. The otter is now a protected species but if it is to recover some of its former range, remaining habitat must be retained.
While otter populations have decreased over much of northern Europe, the animal survives, albeit somewhat precariously, in a few southern parts of the continent.     

Spatially restricted gene flow and reduced microsatellite polymorphism in the Eurasian otter Lutra lutra in Britain

Although gene flow and population fragmentationwill often have opposed effects on geneticstructure, their actual effects on many elusiveanimal species are unknown. We assessed sucheffects in British populations of the Eurasianotter Lutra lutra by analysis ofgenotypes consisting of 12 microsatellites from618 carcasses representing the period 1982–1998. Spatial patterns of genetic subdivisionand levels of polymorphism in the continuouspopulation in Scotland were estimated. Theseresults were used to infer patterns of geneflow in Scottish otters and assess theinfluence of fragmentation on the geneticstructure of otters in Wales and SW England.The latter showed no higher genetic divergencethan expected given the degree of isolation bydistance found in the Scottish population, andtheir distributions of microsatellite allelesizes provided no evidence for populationbottlenecks. Nonetheless, otters in southernBritain contained significantly lower levels ofmicrosatellite polymorphism than otters inScotland, and the population in the westernpeninsula of SW England was geneticallydistinct. These results suggested that thegenetic structure of the Scottish population isdue more to restricted contemporary gene flowthan to historical fluctuations insubpopulation size, and that the geneticstructure of the southern British populationsis due more to small historical effective sizesthan to recent declines. If spatiallyrestricted gene flow is typical of all Eurasianotter populations then data on dispersal shouldbe taken into account when sitting protectedareas for this species.     

The autumn migration records of the Red-breasted Flycatcher

A census of breeding Ringed Plovers in the UK in 1984 revealed 7534 pairs and a further 1083 pairs were estimated, bringing the total to just over 8600 territorial pairs. Two-thirds of these were in Scotland. The Western Isles, particularly the dry machair, supported 2324 of these, 27% of the national total. Estimated numbers in England (2389) and Wales (224) showed, using the comparison of counted areas only, increases over 1973/74 of 19.6% and 21.1% respectively. Elsewhere, however, a similar comparison showed that numbers were stable or decreasing slightly. The large increase in the UK total over 1973/74 was primarily due to improved coverage in Scotland. Of the habitats used, open beaches throughout most of the UK and machair in the Western Isles were by far the most important. A trend was apparent, most clearly in England, for birds to spread to inland sites. The concentration of Ringed Plovers into nature reserves and other protected sites, especially in England, is discussed, along with the implications for the design of access arrangements to such areas.     

Vertically transmitted HIV infection in the British Isles.

OBJECTIVE--To describe the epidemiology of vertically acquired HIV infection in the British Isles, the level of underreporting, the vertical transmission rate, and clinical spectrum of paediatric AIDS. DESIGN--Confidential, linked registers based on reporting from obstetricians and paediatricians; anonymous unlinked neonatal HIV serosurveys. SETTING--British Isles. SUBJECTS--Children born to mothers with HIV infection. MAIN OUTCOME MEASURES--Trends in HIV infection and vertical transmission rate. RESULTS--In Scotland and the Irish Republic, where most maternal HIV infection is related to drug misuse, the annual number of reports of children born to infected mothers has fallen since 1989. In England and Wales nearly half of maternal infections have been acquired overseas, and the number of children born to these women, and to women who became infected in Britain, is increasing. In south east England the proportion of live births to women whose infection was identified before delivery was only 17% (50/287), compared with 68% (26/38) in Scotland. The vertical transmission rate was 13.7% (23/168), and 23% of infected children developed AIDS in the first year of life. 41% (38/92) of children born to infected mothers who were ascertained after delivery were breast fed, compared with 5% (12/236) of those ascertained before delivery. CONCLUSIONS--The incidence of vertically transmitted HIV infection is increasing in England and Wales. More extensive antenatal testing would enable infected women to be counselled against breast feeding, which could prevent a substantial proportion of vertical transmission in some areas, and would increase opportunities for early diagnosis and treatment of infected children.     

Nuclear microsatellites reveal contrasting patterns of genetic structure between western and southeastern European populations of the common ash (Fraxinus excelsior L.)

To determine extant patterns of population genetic structure in common ash and gain insight into postglacial recolonization processes, we applied multilocus-based Bayesian approaches to data from 36 European populations genotyped at five nuclear microsatellite loci. We identified two contrasting patterns in terms of population genetic structure: (1) a large area from the British Isles to Lithuania throughout central Europe constituted effectively a single deme, whereas (2) strong genetic differentiation occurred over short distances in Sweden and southeastern Europe. Concomitant geographical variation was observed in estimates of allelic richness and genetic diversity, which were lowest in populations from southeastern Europe, that is, in regions close to putative ice age refuges, but high in western and central Europe, that is, in more recently recolonized areas. We suggest that in southeastern Europe, restricted postglacial gene flow caused by a rapid expansion of refuge populations in a mountainous topography is responsible for the observed strong genetic structure. In contrast, admixture of previously differentiated gene pools and high gene flow at the onset of postglacial recolonization of western and central Europe would have homogenized the genetic structure and raised the levels of genetic diversity above values in the refuges.     

Aspects of the population genetics of Mytilus (Mytilidae; Mollusca) in the British Isles

Starch gel electrophoresis was used to study variation at 11 loci in mussels sampled mainly from British coastal sites. Two types of mussel were identified, Mytilus edulis, the common mussel and its southern relative Mytilus galloprovincialis. Several partially diagnostic loci were used to map the distribution of the two forms. Mytilus edulis was present at all sites sampled in Britain and Ireland but was at low frequency in SW England; M. galloprovincialis was detected in SW England, the south and west of Ireland. Scotland and NE England, but was absent from south Wales, the Irish sea coasts of Wales and Ireland, and SE England. Apart from the occurrence of M. galloprovincialis in NE England, this distribution conforms with the results of studies using morphological characters and parallels the distribution of many other southern species in Britain. At the microgeographical level, M. edulis was found to prefer more sheltered and estuarine conditions than M. galloprovincialis. Analysis using the best diagnostic loci showed that hybridization is occurring between M. edulis and M. galloprovincialis at all localities where they occur sympatrically but that the extent of hybridization varies considerably between localities. The distribution of localities having high proportions of hybrid individuals is best interpreted by assuming that hybrids have higher fitness than parental types at these localities. A study was made of variation within and between those localities where only M. edulis individuals were observed. Little significant geographic variation in allele frequency was detected, but significant deficits of heterozygotes compared with Hardy-Weinberg expectations were seen for most loci. Analysis suggests that the Wahlund effect is not involved and that the most likely cause of the deficit is low frequencies of null alleles. In M. edulis no differences in phenotypic variance in shell height and width were observed between samples of multiply heterozygous and multiply homozygous individuals and no genetic differences were found between juveniles and adults. Overall little evidence was found that balancing selection is responsible for maintenance of the polymorphisms studied in M. edulis. The pattern of geographic variation in gene frequencies in Mytilus in the British Isles is discussed in relation to variation in the south and north of Europe and North America. It is concluded that steep clines in gene frequencies in M. edulis observed by other workers in the Baltic and in Long Island Sound cannot be attributed to the presence of M. galloprovincialis.     

Rapid recovery of genetic diversity of dogwhelk (Nucella lapillus L.) populations after local extinction and recolonization contradicts predictions from life-history characteristics

The dogwhelk Nucella lapillus is a predatory marine gastropod populating North Atlantic rocky shores. As with many other gastropod species, N. lapillus was affected by tributyltin (TBT) pollution during the 1970s and 1980s, when local populations became extinct. After a partial ban on TBT in the United Kingdom in 1987, vacant sites have been recolonized. N. lapillus lacks a planktonic larval stage and is therefore expected to have limited dispersal ability. Relatively fast recolonization of some sites, however, contradicts this assumption. We compared levels of genetic diversity and genetic structuring between recolonized sites and sites that showed continuous population at three localities across the British Isles. No significant genetic effects of extinction/recolonization events were observed in SW Scotland and NE England. In SW England we observed a decrease in genetic diversity and an increase in genetic structure in recolonized populations. This last result could be an artefact, however, due to the superposition of other local factors influencing the genetic structuring of dogwhelk populations. We conclude that recolonization of vacant sites was accomplished by a relatively high number of individuals originating from several source populations (the 'migrant-pool' model of recolonization), implying that movements are more widespread than expected on the basis of development mode alone. Comparison with published data on genetic structure of marine organisms with contrasted larval dispersal supports this hypothesis. Our results also stress the importance of local factors (geographical or ecological) in determining genetic structure of dogwhelk populations.     

Distribution of Oriental and German cockroaches, Blatta orientalis and Blattella germanica (Dictyoptera), in the United Kingdom

Results are presented of a survey carried out by Rentokil Ltd on the distribution of the Oriental cockroach Blatta orientalis L. and the German cockroach Blattella germanica L. in the United Kingdom. The known ranges of both species are increased considerably by the findings of the survey, with several new vice-county records for Scotland (including the Western Isles), England and Wales. The frequency at which Blatta orientalis was observed in outdoor habitats may indicate that this species sometimes spreads to new areas without human assistance.     

Isolation by distance and gene flow in the Eurasian badger (Meles meles) at both a local and broad scale

Eurasian badgers, Meles meles, have been shown to possess limited genetic population structure within Europe; however, field studies have detected high levels of philopatry, which are expected to increase population structure. Population structure will be a consequence of both contemporary dispersal and historical processes, each of which is expected to be evident at a different scale. Therefore, to gain a greater understanding of gene flow in the badger, we examined microsatellite diversity both among and within badger populations, focusing on populations from the British Isles and western Europe. We found that while populations differed in their allelic diversity, the British Isles displayed a similar degree of diversity to the rest of western Europe. The lower genetic diversity occurring in Ireland, Norway and Scotland was more likely to have resulted from founder effects rather than contemporary population density. While there was significant population structure (F ST = 0.19), divergence among populations was generally well explained by geographic distance (P < 0.0001) across the entire range studied of more than 3000 km. Transient effects from the Pleistocene appear to have been replaced by a strong pattern of genetic isolation by distance across western Europe, suggestive of colonization from a single refugium. Analysis of individuals within British populations through Mantel tests and spatial autocorrelation demonstrated that there was significant local population structure across 3-30 km, confirming that dispersal is indeed restricted. The isolation by distance observed among badger populations across western Europe is likely to be a consequence of this restricted local dispersal.     

The origin of unique diversity in deglaciated areas: traces of Pleistocene processes in north‐European endemics from the Galium pusillum polyploid complex (Rubiaceae)

The role of glacial oscillations in shaping plant diversity has been only rarely addressed in endemics of formerly glaciated areas. The Galium pusillum group represents a rare example of an ecologically diverse and ploidy‐variable species complex that exhibits substantial diversity in deglaciated northern Europe. Using AFLP and plastid and nuclear DNA sequences of 67 populations from northern, central, and western Europe with known ecological preferences, we elucidate the evolutionary history of lineages restricted to deglaciated areas and identify the eco‐geographic partitioning of their genetic variation. We reveal three distinct endemic northern lineages: (i) diploids from southern Sweden + the British Isles, (ii) tetraploids from southern Scandinavia and the British Isles that show signs of ancient hybridization between the first lineage and populations from unglaciated central Europe, and (iii) tetraploids from Iceland + central Norway. Available evidence supports a stepwise differentiation of these three lineages that started at least before the last glacial maximum by processes of genome duplication, interlineage hybridization and/or allopatric evolution in distinct periglacial refugia. We reject the hypothesis of more recent postglacial speciation. Ecological characteristics of the populations under study only partly reflect genetic variation and suggest broad niches of postglacial colonizers. Despite their largely allopatric modern distributions, the north‐European lineages of the G. pusillum group do not show signs of rapid postglacial divergence, in contrast to most other northern endemics. Our study suggests that plants inhabiting deglaciated areas outside the Arctic may exhibit very different evolutionary histories compared with their more thoroughly investigated high‐arctic counterparts.     

Genetic diversity of the green spruce aphid (Elatobium abietinum Walker) in north-west Europe

Abstract 1 The Random Amplified Polymorphic DNA (RAPD) method was used to investigate genetic diversity of anholocyclic populations of the green spruce aphid, Elatobium abietinum Walker, in north‐west Europe. 2 The results showed that the aphid in this region was divided genetically into three major groups. Aphids from the British Isles and north‐west France comprised the first group, the second group consisted of aphids from Denmark and Iceland, and the third group consisted of aphids from Norway. 3 The results indicated a significant level of gene flow within and between sites and geographical regions, especially in the British Isles and north‐west France. Lateral migration of the aphid and/or sexual reproduction is likely to have facilitated the gene flow. 4 The implications of these findings on management of the green spruce aphid are discussed.     

Oceanic and temperate rainforest climates and their epiphyte indicators in Britain

A biogeographic zone with high oceanicity is a well described feature of the European Atlantic region. This oceanic zone intersects with a zone of European temperate rainforest that has received increasing conservation recognition. Although having a degree of spatial overlap, the terminology applied to these different zones is not synonymous. Temperate rainforest is one example of an oceanic system, alongside others such as blanket bog or liverwort heath. Conversely, oceanic systems provide one type of climatic setting suitable to the development of temperate rainforest, alongside other and contrasting landscapes such as the orographic climate of continental mountains. Zones of high oceanicity and temperate rainforest are both strongly represented in the British Isles, and this study examines the degree of spatial overlap in Britain for standard definitions of each. Lichen epiphyte indicators associated with zones of oceanic woodland or temperate rainforest were quantified, and subsequently tested for conservation priority Atlantic oakwoods (Annex 1 Habitat Code 91A0: old sessile oak woods with Ilex and Blechnum in the British Isles). Discrepancies between oceanic woodland and temperate rainforest led to slightly different sets of indicator species that could be applied in biodiversity and habitat quality assessments. The definition of oceanic systems appeared to include warmer and lowland situations for example in coastal Wales and south-west England. In contrast, temperate rainforest extended to cooler upland areas in north-eastern Scotland. The species indicators for oceanic and temperate rainforest were nevertheless effective in identifying sites with different conservation priorities, such as for protection or restoration.     

Phylogeography and recent historical biogeography of Hydroporus glabriusculus Aubé (Goleoptera: Dytiscidae) in the British Isles and Scandinavia

The genetic relationships of populations of the diving beetle Hydroporus glabriusculus in the British Isles and Sweden were examined using allozyme electrophoresis. H. glabriusculus is widespread in the far north of Eurasia, and occurs further south in western and central Europe as isolated relict colonies in fens whose development dates back to the early Postglacial. Study of genetic distance data reveals that the relict colonies of this insect in the British Isles do not form a distinct phylogeographic lineage, but instead belong to a number of separate groups, one of which also occurs in Sweden. Beetles from Ireland, Scotland and Norfolk appear to have diverged from each other during the Pleistocene, and colonized the British Isles in the early Postglacial in separate waves. Populations in the Norfolk Breck are closely related to the Swedish population studied, these two groups apparently having diverged during the Windermere Interstadial. All Norfolk colonies show remarkably similar depauperate levels of genetic variability, which is considered to have resulted from bottlenecking of an ancestral populaton in the Late Glacial. This study demonstrates that the recent historical biogeography of the biota of north-west Europe may be more complex than would appear from a simple consideraton of Holocene events.     

Conservation of genetic uniqueness in remaining populations of red squirrels (Sciurus vulgaris L.) in the South of England

The Eurasian red squirrel (Sciurus vulgaris) is an emblematic species for conservation, and its decline in the British Isles exemplifies the impact that alien introductions can have on native ecosystems. Indeed, red squirrels in this region have declined dramatically over the last 60 years due to the spread of squirrelpox virus following the introduction of the gray squirrel (Sciurus carolinensis). Currently, red squirrel populations in Britain are fragmented and need to be closely monitored in order to assess their viability and the effectiveness of conservation efforts. The situation is even more dramatic in the South of England, where S. vulgaris survives only on islands (Brownsea Island, Furzey Island, and the Isle of Wight). Using the D‐loop, we investigated the genetic diversity and putative ancestry of the squirrels from Southern England and compared them to a European dataset composed of 1,016 samples from 54 populations. We found that our three populations were more closely related to other squirrels from the British Isles than squirrels from Europe, showed low genetic diversity, and also harbored several private haplotypes. Our study demonstrates how genetically unique the Southern English populations are in comparison with squirrels from the continental European range. We report the presence of four private haplotypes, suggesting that these populations may potentially harbor distinct genetic lineages. Our results emphasize the importance of preserving these isolated red squirrel populations for the conservation of the species.