Late Ordovician extinction of North American and British crinoids

After reaching a diversity peak in the Caradocian, North American Ordovician crinoids underwent a gradual decline to a nadir in the early Ashgillian (Maysvillian). This interval, recording extinction of the Cleiocrinidae, Merocrinidae, Ottawacrinidae, Hybocystitidae, and several lineages of camerate crinoids, was apparently caused by major environmental shifts in seas of eastern North America resulting from a westward-prograding wedge of terrigenous clastics derived from the Taconic Highlands, possibly coupled with a marine transgression in the Maysvillian that allowed colder water slope biofacies to invade the craton. Crinoids suffered a major episode of extinction in the late Ashgillian (late Richmondian/Rawtheyan). This event, preceding the end of the Ordovician by at least one stage or 2 to 4 million years, resulted in extinction of 12 families of crinoids including the Xenocrinidae, Tanaocrinidae, Reteocrinidae, Archaeocrinidae, Anthracocrinidae, Cincinnaticrinidae, Iocrinidae, Anomalocrinidae, Carabocrinidae, Cupulocrinidae, Porocrinidae, and Hybocrinidae. Glacio-eustatic lowering of sea level may have triggered this crisis by partially draining the North American craton, resulting in changes in oceanic circulation, salinity, and temperature. Latest Ordovician (Hirnantian) carbonates of the North American mid-continent region contain pelmatozoan assemblages from which Silurian crinoids radiated. These taxa were largely unaffected by a minor extinction event at the Ordovician/Silurian boundary.     

An historical survey of the collection and study of rotifers in Britain

With reference to the author's compilation of British rotifer records, the main contributions to our knowledge of rotifers in the British Isles are outlined and the impetus provided by local natural history societies is commented upon. The usefulness and limitations of early records are examined and the scope offered to future collectors is discussed.     

A new way of looking at dendroprovenancing: Spatial field correlations of residuals

A graphical method is used to demonstrate the results of new analytical steps introduced as an aid to provenancing oak within the British Isles. The current method for determining the likely area of origin of a tree-ring series is to map the distribution of t-values obtained when the subject chronology is compared with each of the available reference chronologies. Although useful, this falls into the trap that the t-value itself is subject to variation in length of the series being compared. The first step to overcome this is to instead use the R-value, a common way of characterising inter-site tree-ring relationships. It can be seen however that with dated sites, the geographical spread of well-matching sites is often quite large (the very reason why one can have confidence in the dating). This new method introduces two new steps. The first is to subtract the regional growth signal before comparing the sites. It is then possible to focus on the often more minor local scale variations in growth, the weak relationships previously overwhelmed by the regional signal sometimes becoming apparent using the paired inter-site correlations (residuals). The second step is then introduced, exploiting the information available in these maps. Objectively quantifying the agreement between the spatial correlation fields for a single site is achieved by scoring and mapping the agreement between the inter-site correlation maps for each other site, here termed the ‘field correlation’. It is shown that this sometimes gives an improved indication of the likely area of growth, and can be used in conjunction with any other information available to suggest likely geographical origins with more confidence.     

Molecular archaeology of the mitochondrial geonome

Summary We develop a stepwise model for the net transfer of nucleic acid sequences between nonhomologous genomes. This model is then used to explain the two major patterns in the evolutionary history of mitochondrial genomes: the gross reduction of the number of genes, and the subsequent acquisition of introns.     

Methane production and methane consumption: a review of processes underlying wetland methane fluxes

Potential rates of both methane production and methane consumptionvary over three orders of magnitude and their distribution is skew.These rates are weakly correlated with ecosystem type, incubationtemperature, in situ aeration, latitude, depth and distanceto oxic/anoxic interface. Anaerobic carbon mineralisation is amajor control of methane production. The large range in anaerobicCH₄:CO₂ production rates indicate that a largepart of the anaerobically mineralised carbon is used for reduction ofelectron acceptors, and, hence, is not available for methanogenesis.Consequently, cycling of electron acceptors needs to be studied tounderstand methane production. Methane and oxygen half saturationconstants for methane oxidation vary about one order of magnitude.Potential methane oxidation seems to be correlated withmethanotrophic biomass. Therefore, variation in potential methaneoxidation could be related to site characteristics with a model ofmethanotrophic biomass.     

Additional records and notes for Wheeler's (1992) List of the Common and Scientific Names of Fishes of the British Isles

This paper compiles information new to an earlier list published in 1992. Most changes are (1) additions largely resulting from importation of freshwater species, (2) range extensions of neritic and oceanic epipelagic species, together with (3) the incidental capture of species from within the 200 m bathymetric limit of resident deep pelagic and demersal deep‐sea representatives. A list of such species with the potential to stray from residence in the deeper strata of the oceanic region to shelf waters (<200 m) is presented in appendices.     

Additional records and notes for Wheeler's (1992) List of the Common and Scientific Names of Fishes of the British Isles

This paper compiles information new to an earlier list published in 1992. Most changes are (1) additions largely resulting from importation of freshwater species, (2) range extensions of neritic and oceanic epipelagic species, together with (3) the incidental capture of species from within the 200 m bathymetric limit of resident deep pelagic and demersal deep‐sea representatives. A list of such species with the potential to stray from residence in the deeper strata of the oceanic region to shelf waters (<200 m) is presented in appendices.     

The geographical relationships of the British and Irish flora: a comparison of pteridophytes, flowering plants, liverworts and mosses

Aim To compare the wider distribution of the pteridophytes, flowering plants, liverworts and mosses recorded as natives of Britain and Ireland, and to assess the proportion and distribution of species in each group which belong to predominantly extra-European genera. Location The species native to the British Isles are considered in relation to their distribution in the Northern Hemisphere, and predominantly extra-European genera are identified by consideration of the distribution and centre of numerical diversity of the genera worldwide. Methods A recent classification of the pteridophytes, flowering plants, liverworts and mosses into floristic elements is used in a quantitative study of the distribution of species in the four groups, the patterns of occurrence being compared by standardized residuals. Results Mosses and liverworts have more northerly distributions than the flowering plants in the Northern Hemisphere; pteridophytes show an intermediate pattern. There are marked differences in the longitudinal ranges of the groups south of the Boreal biome, with vascular plants tending to be confined to Europe or western Eurasia whereas cryptogams are more likely to occur additionally in North America or have a circumpolar distribution. The proportion of predominantly extra-European genera is particularly high in the pteridophytes and the liverworts and in these groups the rich hyperoceanic flora of the British Isles is almost entirely composed of species in genera that attain their centre of diversity in the tropics. Main conclusions Major taxonomic groups show different distribution patterns, reflecting their rates of evolution and powers of dispersal. The flowering plants, as the least mobile and most rapidly evolving group, have a greater proportion of their species in the European and Eurosiberian elements and a higher proportion of species from extra-European genera in the more northerly elements.     

Additions and amendments to the list of British smut fungi

Investigation of material of British smut fungi held in the national collections at kew (k) undertaken during preparation of the new checklist of British and Irish Basidiomycota (Legon et al. 2005) identified several species not hitherto known from the British Isles. These include taxa not previously recognised due to earlier, broader species concepts, as well as others based on earlier misidentifications or discovered during examination of herbarium material of their host plants. These taxa are fully reported here. In addition, amendments to nomenclature and taxonomy of other British species which have occurred since the monography by Mordue & Ainsworth (1984) are summarised.     

Current status of American mink Neovison vison in Great Britain: a review of the evidence for a population decline

1. The American mink Neovison vison in Great Britain is an invasive alien species, with significant impacts on native prey species. There have been suggestions that populations of mink in Britain have declined since the 1990s.
2. Three nationwide data sets include data on mink distribution and abundance. Scat surveys and the National Game Bag Census suggest population declines, but the latter does not take account of survey effort (which may also have declined) and the former is misleading because there is evidence that mink change their marking behaviour in the presence of otters Lutra lutra. National Biodiversity Network data suggest an increase in mink numbers, but this can be explained by a concomitant increase in mammal recording.
3. Although intra-guild competition between invasive mink and native otters is likely, there is no evidence that otters have caused a decline in mink numbers. There is little information on the impact of disease, or exposure to rodenticides, on wild mink – both warrant further attention. Eradication efforts can have an impact on mink populations, but currently neither implementation nor monitoring is sufficient to generate effects throughout Great Britain or to assess the impact of cumulative local and regional efforts.
4. We conclude that it is not possible, on the basis of currently available data for Great Britain, to ascertain the status of mink or assess the underlying trend in their population. We stress the importance of collaboration, coordination, and record keeping (and sharing) in future, proper interpretation of existing data, and the use of alternative data sources. We call for greater, and better, effort in both mink management and monitoring of management in Great Britain.

     

Living archaeology: artefacts of specific nest site fidelity in wild chimpanzees

Savanna chimpanzees are known to re-use areas of the landscape for sleep, and patterns of chimpanzee sleeping site re-use are proposed as a referential model for early hominin archaeological site formation. We recorded the prevalence of deformed but healed branches and remnants of dead branches found around fresh nests at the savanna site of Issa in Ugalla, Tanzania. These old nest scars were found in 79% of 112 beds. We also randomly selected potential nesting locations for a subset of 32 beds within the same trees, and found nest scars in only 19% of these “control” locations. We then monitored 275 nests for up to 19 months for decay, regeneration of new branches, and re-use. Of these 275 nest locations, 24% were re-used within the first nine months of monitoring, and most re-use occurred when the nest had already decayed and was not easily visible from the ground. After 18 months, the proportion of specific nest positions re-used increased to 48%. This fidelity is likely a result of the creation of ideally-shaped support structures and supple new growth for mattress material with successive use of nest locations. We propose that specific nest site re-use may not be a direct product of environmental determination, but a result of “niche construction” through formation of good building sites within trees. Environmental modification through construction behaviour may have influenced both chimpanzee and early hominin ranging, and thus leaves behind recognisable patterns of artefact deposition across the landscape.     

Henderson Island prehistory: colonization and extinction on a remote Polynesian island

Situated at the extreme margin of the Indo-West Pacific biotic province, the four islands of the isolated Pitcairn Group hold interest for biogeographers and archaeologists alike. Human settlement may have been as early as the 8th century AD for the uplifted limestone island of Henderson, the most pristine island of its kind. An archaeological survey of the Pitcairn Islands is provided, while Henderson is examined in detail. Recent extensive excavations provide a record of change during 600 years of human occupation. Adaptation to the ecologically-marginal conditions is documented by artefacts, more than 150000 vertebrate bones, molluscs and subfossil plant remains recovered from stratigraphic contexts. The effects of prehistoric human occupation on the pristine environment are revealed by Polynesian plant and animal introductions, bird extinctions and range reductions, possible over-predation of marine molluscs, exploitation of sea turtles, and large-scale burning for swidden agriculture. The origin of human colonists is documented by analysing imported artefacts by geochemical characterization (x-ray fluorescence analysis). The human abandonment of Henderson, by the seventeenth century, is viewed in the context of prehistoric regional dynamics.     

The distribution of Gobius cobitis in the British Isles

Records of occuerence of Gobius cobitis on the British coast are listed from the literature and from extensive collecting in interfidal areas. In Britain the number of suitable habitats is reduced and the density of population is lower than in the Channel Islands and Brittany.     

旧石器时代砸击法剥片技术相关问题探讨

砸击法是早期人类最基本的剥片技术之一,自旧石器时代早期至现代民族学观察中一直有大量应用。相对于另一种重要的剥片技术-锤击法,砸击法独特的剥片机制有着诸多的优势和不足,其在人类演化过程中所扮演的角色一直是学术界关注的话题。目前,国内关于砸击法剥片技术的实验和讨论较少,有关砸击法剥片技术的鉴别特征和经济策略等问题一直存在争议。本文通过对砸击法相关术语的梳理,结合泥河湾盆地麻地沟遗址的石器实验研究,明确了砸击法的基本概念,讨论了砸击法的应用方式、经济效益、产品辨识特征,在此基础上分析了砸击法的适用情况,并倡导在以后的砸击法产品辨识过程中应以各地原料为基础进行实验观察,进而对遗址中砸击法产品进行对比和辨认。本文对客观解释古人类的石器技术与生存策略具有重要意义。     

Comparison of Vegetation and CO2 Dynamics Between a Restored Cut‐Away Peatland and a Pristine Fen: Evaluation of the Restoration Success

We studied the restoration success of a cut‐away peatland 10 years after restoration by comparing the vegetation and CO₂ dynamics with those of a pristine peatland of similar nutrition level and climate. Vegetation and CO₂ dynamics were monitored during one growing season. We used DCA (detrended correspondence analysis) and diversity indices to study the vegetation composition within and between the sites, and non‐linear regression models to estimate the seasonal CO₂ fluxes and balances of the sites. Based on both DCA and diversity indices, the study plots in the restored site differed more in the vegetation composition than the study plots in the pristine site. The variation in the CO₂ fluxes and balance was greater in the restored than in the pristine site, resulting from the heterogeneous vegetation in the restored site. The seasonal net CO₂ balance was positive (sink) at both sites, the restored site binding on average 500 ± 410 g CO₂/m² and the pristine site 390 ± 265 g CO₂/m² (statistically not different, p = 0.575). The results indicate that the restoration of the vegetation composition is still incomplete but the vegetation coverage is sufficient for the restored site to function as a sink of atmospheric CO₂.