The competitive and predatory impacts of the nonindigenous crab Carcinus maenas (L.) on early benthic phase Dungeness crab Cancer magister Dana

We evaluate the potential competitive and predatory impacts of nonindigenous European green crab Carcinus maenas on native Dungeness crab Cancer magister in the northeast Pacific. The coastal estuaries of Washington State, USA, provide appropriate habitat for recently introduced green crab, yet these areas are important nursery grounds for Dungeness crab and contribute greatly to the coastal crab fishery. Juvenile Dungeness crabs are dependent on limited intertidal epibenthic shell for refuge habitat during early benthic life and experience increased mortality on open sand and mud as a result of predation by fish and birds. Early juveniles throughout the subtidal are similarly at risk due to predation by fish and especially adult conspecifics. Laboratory experiments and infrared video observations revealed that juvenile green crab displace Dungeness crab of equal size from shelters during one-on-one competition. Green crab also consistently win nocturnal foraging trials in which the species compete for fresh, damaged clams. Field and laboratory enclosure experiments show that juvenile Dungeness crab emigrate from oyster shell habitat as a result of competition and predation by adult green crab. Depending on the extent to which the two species overlap, interactions with the dominant nonindigenous species could have a negative influence on juvenile Dungeness crab survival and could conceivably impact recruitment to the fishery. However, current evidence indicates that the distribution of green crab in Washington State is far removed from nursery areas of Dungeness crab.     

Why are there so many species of bumble bees at Dungeness?

WILLIAMS, P. H., 1989. Why are there so many species of bumble bees at Dungeness? Dungeness is unique in the British Isles in that it has more species of bumble bees than any other locality. Three ideas about what governs the number of species at a locality are examined by locking at patterns of flower visits at Dungeness in comparison with those at Shoreham, a species-poor locality also in Kent. The species of bumble bees that are present at Dungeness but absent from Shoreham show no association in their distributions among 2 km grid-squares in Kent with the species of food-plants that they prefer at Dungeness, nor is there any correlation between the diversity of bees and diversity of food-plants at Dungeness and Shoreham. From the information available, Dungeness is most likely to have more species of bumble bees because it has a particularly high density of the more nectar-rich flowers that bumble bees can use. Bumble bees feed most profitably from deep flowers because these contain more nectar than shallow flowers, although direct access to deeper flowers is ultimately limited by the length of each bee's proboscis. The distribution of worker proboscis lengths among species in the species-pool in Kent is clumped about a median of 7.9 mm. The best foraging conditions for the maximum number of species should be provided when flowers of similar depths are present in sufficiently large numbers for all foragers to make near-optimal flower choices. Although there is no difference in median between the distributions of the bees' proboscis lengths and the depths of the flowers they use at Dungeness, at Shoreham the flower depths used are shorter than the proboscis lengths. Among the food-plants at Dungeness, high densities of Teucrium scorodonia and Echium vulgare are likely to be especially important.     

Recent developments at Dungeness

FINDON, R. A., 1989. Recent developments at Dungeness . The most significant development pressures at Dungeness over the last three years are discussed, namely military training, aggregate winning, water industry, electricity generation, recreation and tourism. The future prospects for Dungeness are briefly reviewed, as are the changes to the area notified as a Site of Special Scientific Interest.     

Migration studies at Dungeness Bird Observatory

McMINN, S., 1989. Migration studies at Dungeness Bird Observatory . The part played in the study of bird migration by the Dungeness Bird Observatory is outlined. Information concerning blackbird ( Tardus merula ) and robin ( Erithacus rubecula ) migration is presented as well as notes on migration over the sea.     

Management plan for the Royal Society for the Protection of Birds reserve at Dungeness, Kent

THOMAS, G. J., GLOVER, J. & MAKEPEACE, P., 1989. Management plan for the Royal Society for the Protection of Birds reserve at Dungeness, Kent . A synopsis of a new management plan for RSPB Dungeness reserve is presented.     

Population genetics of a successful invader: the marsh frog Rana ridibunda in Britain

We investigated the genetic outcome of successful invasion by an alien species, the marsh frog Rana ridibunda, in Britain. Twelve adults translocated from Hungary into Kent (Romney) in 1935 resulted rapidly in a large localized population. A further successful translocation in 1973 from Romney to Sussex (Lewes), together with other range extensions, provided an opportunity to test bottleneck effects during colonization events. Romney and Lewes frogs had similar genetic diversities to those in Hungary at 14 random amplified polymorphic DNA marker (RAPD) and five microsatellite loci. The introduced populations were, however, differentiated genetically from each other and from a reference population in Hungary. Fitness assessments (larval growth and survival) revealed no differences between the Lewes and Romney populations. Despite starting with few founders, significant bottleneck effects on R. ridibunda in Britain were therefore undetectable, presumably because population expansions were rapid immediately after the translocations.     

Induced seasonal reproductive performance in two breeds of sheep

The objective of the present experiment was to determine whether failure to become pregnant through out-of-season reproductive management regimes is attributable to a failure to stimulate normal corpora lutea (CL) production. Romney ewes and East Friesian Composite (EF) ewes were mated in summer, autumn, winter, and early and late spring after administration of intravaginal progesterone inserts (plus eCG in spring and summer) in a factorial (two breedsxfive mating periods) experimental design. Oestrus rate was determined from mating data, and the numbers of CL were determined by laparoscopy 9 days after ram introduction. Conception rate, pregnancy rate and litter size were determined by transabdominal ultrasonography 62 days after ram introduction. Proportions of ewes displaying oestrus did not differ significantly (75-100%) between seasons or breeds, except for the Romney ewes in summer (67%; P<0.05). Numbers of CL on Day 9 for EF ewes was lowest in autumn (1.5) and winter (1.5), and highest in late spring (2.1; P<0.05). In contrast, Romney ewes had the lowest CL count in summer (1.3), and the highest in autumn (1.8) and winter (1.6; P<0.05). Only in summer was there a difference between breeds (EF 1.8; Romney 1.3; P<0.01). The proportion of ewes that failed to conceive despite having one or more CL present was highest in late spring (EF 41%, Romney 43%), and lowest in autumn (EF 9%, Romney 4%) and winter (EF 14%, Romney 4%; P<0.05). Conception and pregnancy rates followed similar patterns with values for autumn (EF 91%, 91%; Romney 96%, 96%) and June (EF 86%, 82%; Romney 91%, 83%) being significantly (P<0.05) higher than in early (EF 50%, 40%; Romney 54%, 50%) and late spring (EF 44%, 36%; Romney 42%, 36%). Pregnancy rate in summer was higher for EF ewes (60%) than for Romney ewes (39%) but conception rates were not statistically different (EF 68%; Romney 60%). Numbers of foetuses identified at scanning was highest in autumn (1.5) and lowest in late spring (0.5 P<0.001): Litter size in pregnant EF ewes was highest in early spring and lowest in winter (1.8 versus 1.2; P<0.01), but for pregnant Romney ewes was highest in winter and lowest in early spring (1.9 versus 1.3; P<0.001). It was concluded that seasonal differences in the ability of ewes to conceive are not the consequence of failure to display oestrus or to ovulate, but probably are a result of failure of fertilisation or the establishment of pregnancy.     

Shingle-based wetlands at Dungeness

WATERS, S. J. P. & FERRY, B. W., 1989. Shingle-based wetlands at Dungeness . At Dungeness, a unique development of open water and natural wetland has occurred on the shingle beaches. Over 700–1000 years, low-lying areas have changed from saline lagoons into freshwater lakes which are now largely infilled by reedswamp and sallow carr. Since about 1970, the water-table has been lowered, by a combination of water abstraction and hydrological changes associated with gravel extraction. Water-table lowering has accelerated colonization by reedswamp and sallow carr, and has caused loss of sedge-rich marshland. Possible methods are suggested for promoting development of such marshland in artificial excavations.     

Kinship analysis of Pacific salmon: insights into mating, homing, and timing of reproduction

Multilocus microsatellite genotypes were used to infer kinship and relatedness in two species of Pacific salmon from three populations in Washington State. Even in the absence of direct genetic data from parents, clustering of individuals according to allele sharing and reconstruction of parental genotypes allowed resolution of full- and half-sib relationships among 135 chinook salmon (Oncorhynchus tshawytscha) sampled as preemergent juveniles from 14 redds in the Dungeness River. Inferred reproductive behaviors included single-pair matings, polyandry in which females mated with two to three males at a single redd, polygyny in which males mated with two females at different redds, use of two redds by a single female, and use of one redd site by two females. Greater average relatedness (rxy) in the upper reach of the Dungeness River implied within-reach homing of returning adults. In steelhead trout (O. mykiss), the frequency of related pairs (dyads) of mature individuals that migrated up Snow Creek less than a week apart was greater than expected for randomly chosen dyads, as was the frequency of steelhead dyads that were spawned on the same day in the Forks Creek hatchery. These results imply a heritable basis for upstream migration date and maturation date in steelhead trout.     

The shingle ridge succession at Dungeness

FERRY, B. W., BARLOW, S. L. & WATERS, S. J. P., 1989. The shingle ridge succession at Dungeness . The range of plant communities which have colonized both intact shingle ridges and areas of disturbed shingle on Denge Beach, Dungeness, are described. An attempt is made to place these communities into categories of the National Vegetation Classification scheme, and further to relate them to physical and chemical gradients and variations in the shingle substrate.     

Lichens at Dungeness

LAUNDON, J. R., 1989. Lichens at Dungeness . The lichen vegetation at Dungeness is reviewed. The most important lichen communities are of three types. Firstly, there are the crustose lichens which colonize the bare pebbles. Secondly, the tracts of rich Cladonia turf which form the lichen heath and which play a major role in the vegetation cycle. Thirdly, there are the epiphytes on Prunus scrub. In addition, lichens on artificial substrates, especially wooden fences, are noteworthy. About 150 species occur, amongst the most interesting being Cladonia mitis, Lecanora helicopis, Lecidea insidiosa, Parmelia soredians, Rinodina aspersa and Umea glabrata. A new combination is made in the genus Porpidia. The term 'bird farming' is published. The fragmentation of the vegetation by building and gravel extraction receives critical comment.     

Persistence of high diversity in non-equilibrium ecological communities: implications for modern and fossil ecosystems

Explaining the origin and maintenance of biodiversity is critical for understanding the potential consequences of present-day environmental change on ecological communities, as well as the evolutionary history of ecosystems in the Earth's past. Much effort in theoretical ecology has focused on identifying mechanisms that promote stable coexistence of species at equilibrium. However, in a consumer-resource model of competition along an environmental gradient, high-diversity assemblages have the potential to persist in non-equilibrium states for millions of generations with very little species loss. Species' populations in such competitively accommodated communities show slow drift; if disrupted, they rapidly reorganize into alternative persistent states. Fossil examples of prolonged ecological stability lasting 1-5 Myr punctuated by rapid reorganization (e.g. brachiopods from the Permian Reef of west Texas) suggest that some palaeocommunities represent a record of periodically disrupted transient states rather than stable equilibria. The similarity between the theoretical results reported here and palaeontological data suggests that the maintenance of high-diversity communities, both in the past and present, may reflect long-duration, non-equilibrium transient dynamics. If so, this has implications for the response of such communities to present-day environmental change, as well as for the evolution of lineages in such systems.     

Seasonal and site specific variation in the component community structure of intestinal helminths in Apodemus sylvaticus from three contrasting habitats in south-east England

Seasonal fluctuations in the prevalence and abundance of infection with intestinal helminths were studied in Apodemus sylvaticus (wood mouse, n = 399), from three contrasting habitats in southern England, to test the hypothesis that both intrinsic (host sex, age) and extrinsic (season, site) factors influence parasite species richness and abundance. Five species of helminths were recovered but only one of these (Capillaria murissylvatici) was site-specific (Dungeness). Total species richness was therefore 5 at Dungeness and 4 at the other two sites. Mean species richness was 1.4, but in adult mice there was a pronounced difference between the sites, and an independent highly significant effect of season. Syphacia stroma and Corrigia vitta both showed marked differences between sites in respect of prevalence and abundance of infection. Capillaria murissylvatici was encountered at Dungeness mostly in the spring whereas seasonal changes in abundance of S. stroma were consistent across all three sites. Seasonal fluctuations in the abundance of Catenotaenia pusilla were compounded by differences between sites. Host sex was not a significant factor in any species, although a posteriori analysis of S. stroma worm burdens for the Isle of Wight site revealed a moderate local sex effect. Overall the principal determinants of variation in helminth burdens were the extrinsic factors, site and season.     

The medicinal leech, Hirudo medicinalis (L.) (Hirudinea: Gnathobdellae), at Dungeness, Kent

WILKIN, P. J., 1989. The medicinal leech, Hirudo medicinalis (L.) (Hirudinea: Gnathobdellae), at Dungeness, Kent . An account of the ecology and conservation of the medicinal leech ( Hirudo medicinalis (L.)) at Dungeness, Kent, is presented.     

The role of ecological knowledge in explaining biogeography and biodiversity in Amazonia

Biogeographical studies in Amazonia have commonly taken a historical, rather than an ecological approach. General patterns have been sought in the distribution maps of different species, and these have been explained in terms of past or present distribution barriers, especially past climates and large rivers. Implicitly, and often also explicitly, it is assumed that Amazonia is ecologically so uniform that present-day ecological conditions are rather insignificant in determining species distribution patterns and speciation. However, this assumption is more based on the lack of relevant data than on actual observations of environmental uniformity or ecological unspecialization of the species. Recent studies have indeed documented ecological heterogeneity and floristic differences among sites that were previously thought similar. In the absence of direct knowledge of the past, more complete ecological and environmental understanding of the present-day Amazonia are needed for evaluating the relative roles of historical and ecological factors in Amazonian biogeography and biodiversity.     

Microrefugia

The concept of microrefugia is widely accepted to explain the post-glacial colonization of continents, which led to the present-day biotic configuration of the Earth. However, so far, microrefugia are no more than a 'theoretical necessity' without an appropriate biogeographical and ecological characterization. Here, a tentative definition and a classification of microrefugia, based on the existing literature, are proposed for discussion. A deeper biogeographical analysis of the concept is suggested using novel ecological models and methods, in order to develop new hypotheses to be tested with palaeoecological and molecular phylogenetic tools.     

Pigmentation in Black-boned sheep (<Emphasis Type="Italic">Ovis aries</Emphasis>): association with polymorphism of the <Emphasis Type="Italic">Tyrosinase</Emphasis> gene

Measurements were made in Black-boned (n = 40) and normal (n = 23) sheep (Ovis aries) from a flock in Nanping County of Yunnan Province, China, as well as a group (n = 21) of Romney Marsh sheep (O. aries) with the view to explaining the basis of the dark pigmentation occurring in the Black-boned animals. Plasma colour was significantly darker (P < 0.01) in Black-boned sheep than in their normal flock mates, which in turn had significantly darker plasma (P < 0.01) than the Romney Marsh sheep. Similar significant (P < 0.01) differences were measured for plasma tyrosinase activity and both groups of sheep from Nanping County had similar plasma concentrations of glutathione which were significantly smaller (P < 0.01) than for the Romney Marsh sheep.A partial fragment of 750 bp of exon 1 of the gene encoding tyrosinase was constructed and found to contain two silent mutation sites (G192C and C462T) but there was no effect on amino acid sequences of tyrosinase. Using restriction fragment length polymorphism analyses two allelic variants of site G192C were identified giving rise to the genotypes GG, GC and CC; the frequencies of allele G being 0.914, 0.824 and 0.286 in the Black-boned sheep, their flock mates and the Romney Marsh sheep respectively. Plasma tyrosinase activity was similar for genotypes GG and GC and for both genotypes significantly higher (P < 0.05) than for genotype CC. The sheep from Nanping County displayed only the GG and GC genotypes and had predominantly black or black and white coat colour whereas the Romney Marsh sheep were of either genotype GC or CC and exhibited only white coat colouration. It is not appears that the dark pigmentation of the Black-boned sheep arises because of polymorphisms in the exon 1 of tyrosinase gene. However, this result could explain the differences between Black-boned and Romney Marsh sheep but not for differences between Black-boned and Nanping Normal sheep. Moreover, this result has provided evidence of genetic markers in the form of polymorphisms of the tyrosinase gene which may help to find the black traits causing mutations. There would be merit in further studies using histochemical and molecular techniques to elucidate the causes of the dark pigmentation in these Black-boned sheep.     

Acquisition of phosphorus and other poorly mobile nutrients by roots. Where do plant nutrition models fail?

Background

In the context of increasing global food demand, ecological intensification of agroecosystems is required to increase nutrient use efficiency in plants while decreasing fertilizer inputs. Better exploration and exploitation of soil resources is a major issue for phosphorus, given that rock phosphate ores are finite resources, which are going to be exhausted in decades from now on.

Scope

We review the processes governing the acquisition by plants of poorly mobile nutrients in soils, with a particular focus on processes at the root?Csoil interface. Rhizosphere processes are poorly accounted for in most plant nutrition models. This lack largely explains why present-day models fail at predicting the actual uptake of poorly mobile nutrients such as phosphorus under low input conditions. A first section is dedicated to biophysical processes and the spatial/temporal development of the rhizosphere. A second section concentrates on biochemical/biogeochemical processes, while a third section addresses biological/ecological processes operating in the rhizosphere.

Conclusions

New routes for improving soil nutrient efficiency are addressed, with a particular focus on breeding and ecological engineering options. Better mimicking natural ecosystems and exploiting plant diversity appears as an appealing way forward, on this long and winding road towards ecological intensification of agroecosystems.     

Minimum Effective Dose of Cattle and Sheep BSE for Oral Sheep Infection

The minimum dose required to cause infection of Romney and Suffolk sheep of the ARQ/ARQ or ARQ/ARR prion protein gene genotypes following oral inoculation with Romney or Suffolk a sheep Bovine spongiform encephalopathy (BSE)-derived or cattle BSE-derived agent was investigated using doses ranging from 0.0005g to 5g. ARQ/ARQ sheep which were methionine (M) / threonine (T) heterozygous or T/T homozygous at codon 112 of the Prnp gene, dosed ARQ/ARR sheep and undosed controls did not show any evidence of infection. Within groups of susceptible sheep, the minimum effective oral dose of BSE was found to be 0.05g, with higher attack rates following inoculation with the 5g dose. Surprisingly, this study found no effect of dose on survival time suggesting a possible lack of homogeneity within the inoculum. All clinical BSE cases showed PrP^d accumulation in brain; however, following cattle BSE inoculation, LRS involvement within Romney recipients was found to be significantly lower than within the Suffolk sheep inoculated group which is in agreement with previous reports.     

Defining past ecological status and in situ reference conditions using benthic foraminifera: A case study from the Oslofjord,Norway

Characterizing marine water bodies and defining ecological status, both present and past (pre-impacted), has become an important task for EU's Member States and their associates during the last decade due to the implementation of the Water Framework Directive (WFD). However, none of the methods used to define Ecological Quality Status (EcoQS) are able to accurately define the status for both the present-day and reference conditions at a given site (i.e., in situ). Recent studies have revealed a significant correlation between the diversity of living (stained) fossilizable benthic foraminifera (protists) and associated environmental parameters (e.g., dissolved oxygen concentration). The present study takes this relationship a step further by applying methods used to define present-day EcoQS on fossil benthic foraminiferal assemblages and, thereby, defining past EcoQS (PaleoEcoQS). This is particularly useful for defining reference condition in areas where biological- and instrumental time-series are limited or lacking. Our case study from the Oslofjord, Norway, shows that (1) the “Foraminiferal method” can define temporal developments in in situ EcoQS from reference to present-day conditions, (2) results of the “Foraminiferal method” reflect available historical biological records and hydrographic time series, (3) data (1993 and 2009) on macrofauna (traditional bio-monitoring tool) and benthic foraminifera from the same sites define the same EcoQS, and (4) the changes in foraminiferal diversity through time are due to human activity (pollution), rather than climate change. Using in situ data to define ecological reference conditions is preferable compared to modeling or comparisons with present-day supposedly similar reference conditions.