Effects of artificial freshets on substratum composition,benthic invertebrate fauna and invertebrate drift in two impounded rivers in mid-Wales

Artificial discharges of water from reservoirs caused a six-fold and three-fold increase in discharge in the R. Tywi and R. Elan respectively but did not significantly alter particle size composition (by weight) and the porosity of the substratum or the organic matter content of fine particles (<0.5 mm). Freshets in both rivers resulted in a consistent, though not significant, reduction in total densities of invertebrates and the densities of many major taxa and abundant species. During the freshet in the R. Elan, maximum concentration and total load of suspended solids were about 11 and 35 times greater than pre-release values respectively while invertebrate drift was dominated by Chironomidae (65%) and Plecoptera (25%). Total numbers and densities of drifting chironomids increased immediately in response to the flow increase; in contrast, numbers and densities of plecopterans increased later, during the night.     

A computer program for the calculation of sedimentation coefficients and molecular weights of nucleic acids

A procedure is described for the purification of nuclei and identification of chromatin proteins in transformed epithelial cell lines from mammalian bladder and salivary gland. Nuclear purification was performed by homogenization, in hypotonic buffer containing polyamines to stabilize the nuclear structure, followed by 0.1–0.2% Triton X-100 washing and centrifugation through 2.2 m sucrose. Chromatin was liberated from nuclei by freeze-thawing in hypotonic buffer and the chromatin proteins were extracted with 7 m urea/3 m NaCl. The chromatin proteins were identified using NEPHGE two-dimensional electrophoresis and fluorographic autoradiography. This procedure enabled detection of histones and a range of basic nonhistone chromatin proteins, following cell culture in the presence of low levels of l-(4,5-³H)leucine.     

Iron age to medieval entomogamous vegetation and Rhinolophus hipposideros roost in South-Eastern Wales (UK)

Karst cave systems are well developed in Wales (UK) and, in some instances, constitute important bat roosts. Ogof Draenen, near Blaenavon in south-east Wales, is the most recent major cave discovery (1994) with already > 70 km of passages explored spanning a vertical range of 148 m.With the exception of one small chamber (Siambre Ddu) located directly above the main Ogof Draenen system, very few bats have been noticed inside. Extensive accumulations of guano, attributable to Rhinolophus hipposideros, are however found in parts of the Ogof Draenen system. In places covering many square metres and sometimes building heaps > 0.5 m thick, these represent volumes not yet found in any other cave system in the British Isles.Although the date of the abandonment of the main Ogof Draenen system as a bat roost remains unknown, six radiocarbon dates on guano from Ogof Draenen place the occupation in the Iron Age to Medieval period at least. Palynological analysis was undertaken on ten samples distributed through the cave. Comparisons were made with a moss polster and a lake mud sample from the area to provide a first approximation of the regional modern pollen rain and with two modern guano samples, one from Siambre Ddu and one from Agen Allwedd cave (5 km to the north-west) to provide a temporal comparison with the fossil guano. Agen Allwedd cave currently is one of the largest active roosts for Lesser Horseshoe bats in Britain and lies close to the present northern limit of this endangered species in Europe.The main results are that (1) the cave appears to have been used both as a summer and a winter roost; (2) most of the Ogof Draenen guano is formed within c. 1600 ¹⁴C years and, if the largest heap is continuous, it has accumulated within 750 ¹⁴C years, i. e. 0.16 mm yr^− 1; 3) the fossil guano samples reflect a relatively closed oak forest with more abundant ivy (Hedera) and holly (Ilex) than at present; (4) insect-pollinated plants such as Ilex, Acer, Hedera and Impatiens glandulifera are over-represented in the guano samples; (5) in addition to the usual causes of bat roost decline (pesticides, pollution), in the case of Ogof Draenen, we may add entrance blocked by rock collapse and decline of the local forest cover as well as change in its composition.     

Effects of fire on long-unburned Florida uplands

Abstract. The widespread suppression of fire during the 20th century has created extensive areas of fire-prone ecosystems that are in long-unburned condition. Plant species of flatwoods and scrubby flatwoods (= oak scrub) in the southeastern USA possess adaptations that facilitate resprouting, clonal spread, or seeding following fire. While the majority of the woody species of these associations can persist for long periods without fire, fire suppression reduces the populations of ephemeral herbs. Long-unburned (> 35 yr) flatwoods and scrubby flatwoods were burned after five annual vegetation censuses. Both stands were resampled five times over a >8-yr recovery period. One recently burned (<20 yr) flatwoods and two recently burned scrubby flatwoods were censused prior to fire and were recensused over a 5-yr or 11-yr period following fire depending on the stand. In spite of the variety of recovery strategies and time since fire, there were limited changes in the compositions and structures of post-burn stands compared to their preburn states. Detrended Correspondence Analysis showed that recently burned stands returned to preburn states within 1–2 yr. However, the reintroduction of a single fire to long-unburned stands did not restore the populations of herbs typical of recently burned stands. Our results suggest that a single fire may not be effective in restoring flatwoods and scrubby flatwoods that have experienced fire suppression to states more characteristic of recently burned stands.     

Determining diatom ecotones and their relationship to terrestrial ecoregion designations in the central Canadian Arctic Islands

Ecotones are key areas for the detection of global change because many are predicted to move with shifts in climate. Prince of Wales Island, in the Canadian Arctic Archipelago, spans the transition between mid‐ to high‐Arctic ecoregions. We analyzed limnological variables and recent diatom assemblages from its lakes and ponds to determine if assemblages reflected this ecotone. Limnological gradients were short, and water chemistry explained 20.0% of diatom variance in a redundancy analysis (RDA), driven primarily by dissolved organic carbon, Ca and SO₄. Most taxa were small, benthic forms; key taxa such as planktonic Cyclotella species were restricted to the warmer, southern portion of the study area, while benthic Staurosirella were associated with larger, ice‐dominated lakes. Nonetheless, there were no significant changes in diatom assemblages across the mid‐ to high‐Arctic ecoregion boundary. We combined our data set with one from nearby Cornwallis Island to expand the study area and lengthen its environmental gradients. Within this expanded data set, 40.6% of the diatom variance was explained by a combination of water chemistry and geographic variables, and significant relationships were revealed between diatom distributions and key limnological variables, including pH, specific conductivity, and chl‐a. Using principal coordinates analysis, we estimated community turnover with latitude and applied piecewise linear regression to determine diatom ecotone positions. A pronounced transition was present between Prince of Wales Island and the colder, more northerly Cornwallis Island. These data will be important in detecting any future northward ecotone movement in response to predicted Arctic climate warming in this highly sensitive region.     

Immigrant narratives and nation-building in a stateless nation: the case of Italians in post-devolution Wales

This article aims to contribute to the study of migration and nation-building in stateless nations. It explores the media portrayal of Italian immigration in Wales after the 1997 devolution. It assesses why Italian immigrant narratives have figured prominently in the Welsh media after devolution. It shows that, being seen as Wales's ‘model minority’, Italians have ideally served a reinforcement of the surrounding inclusive rhetoric, one that draws on an old-standing Welsh tolerance-myth. Thus, this article argues that stateless nations aiming to gain increasing autonomy can use their immigration history to construct and disseminate a tolerant and inclusive national image, one that aims to foster both indigenous people and migrants' sense of national belonging.     

Responses of Fish to Experimental Introduction of Structural Woody Habitat in Riffles and Pools

The declining condition of river systems associated with rapid development of human societies has led to substantial declines in fish diversity. One cause of decline is the loss of in‐stream Structural Woody Habitat (SWH), an important component of stream ecosystems, particularly as fish habitat. As a result there has been an increase in the number of rehabilitation programs that introduce SWH into rivers. This paper assesses fish responses to SWH introduction in riffles and pools in the Hunter River, eastern Australia, using a Multiple‐Before‐After‐Control‐Impact (MBACI) experimental and analytical design. In the riffle experiment, species richness was comparable among all control and treatment riffles across the entire study period. However, there were significant differences in assemblage structure, fish abundance, and biomass between control and treated riffles. The introduction of SWH (bank embedded deflector jams) appeared to create additional habitat which was utilized by one native fish species (Retropinna semoni—Australian smelt) and one alien species (Gambusia holbrooki—mosquito fish). In pools there were no significant changes in fish species richness, abundance, or biomass following introduction of SWH (pool jams). These findings have important practical and cost implications in terms of the design and implementation of rehabilitation strategies using SWH to restore fish assemblages in degraded streams.     

New records of marine benthic algae from New South Wales, eastern Australia

Twenty‐four species of marine macroalgae are recorded from the mainland coast of New South Wales for the first time. One species, Laurencia platyclada Boergesen, represents a new record for Australia and the Pacific Ocean. Included in these new records is the introduced, invasive and cold‐tolerant strain of the green alga Caulerpa taxifolia, which was formerly known only as native, non‐invasive populations from Lord Howe Island. Based on published accounts, the composition of the marine benthic algae for the state of New South Wales now stands at 131 green, 140 brown and 449 red macroalgae. This baseline information adds significantly to our knowledge of the overall marine biodiversity of the state, as well as to the phycogeography of the southwestern Pacific region.     

New morganucodontans from an Early Jurassic fissure filling in Wales (United Kingdom)

Abstract: Two new genera and species of morganucodontans, Bridetherium dorisae and Paceyodon davidi, are recognized as members of the Morganucodon‐sphenodont fauna preserved in a fissure filling (Pant 4) exposed in Pant Quarry, Vale of Glamorgan, southern Wales. Both taxa are based on isolated molariforms. Mode of occlusion of upper and lower molariforms in B. dorisae differs from the embrasure shearing pattern of Megazostrodon and the offset pattern characteristic of Morganucodon. Lack of a clear correlation between different patterns of occlusion and morphologies of their molariforms supports the working hypothesis that a close correlation between function and morphology of the molars characteristic of therian mammals, for example, was not present in morganucodontans. P. davidi is based on an isolated morganucodontan molariform that is significantly larger than any yet discovered. Several isolated morganucodontan‐like molariforms cannot be referred to these taxa. The new Welsh morganucodontans added to records from other sites indicate the group achieved considerable taxonomic diversity and a near global distribution by the Early Jurassic.     

Comparing methods used in estimating biodiversity on sandy beaches: Pitfall vs. quadrat sampling

We compared the two most commonly used sampling methods, pitfall trapping and quadrat sieving, to study community diversity and talitrid abundance on sandy beaches. They are both widely used methods, however they are related to different behaviors: surface activity (pitfall traps) and burrowing in the substrate (quadrat sieving). To detect bias intrinsically generated by the use of different sampling methods, we applied both methods on a set of five beaches in New South Wales, Australia. The set included non-contiguous beaches, exposed and sheltered, more or less affected by recreational use. The results indicated a high fluctuation in biodiversity features. However, the most human-frequented beaches were grouped together by Multi Dimensional Scaling, and substrate-modifiers talitrid amphipods (sand-hoppers), played a major role in this scaling. The analysis of similarities (ANOSIM) indicated the roles of exposure and human recreational use in shaping the community, while the methods (quadrats vs. traps) resulted in higher fluctuation within samples than between, and informative outliers. Generalized Linear Models developed to estimate the probability of capture of talitrids by sampling method pointed to a higher probability to capture both sand-hoppers and beach-hoppers with the quadrat method. We finally suggest: (1) the comparative use of both sampling methods whenever possible, to capture multiple information and avoid bias in biodiversity estimates; and (2) an ad-hoc strategy when dealing with target populations. In particular, attention should be paid when targeting co-occurring talitrid species characterized by different ecology and behavioral traits: sand-hoppers (substrate modifiers) appeared to be more sensitive than beach-hoppers (non-substrate modifiers) to the impacts considered. In terms of biodiversity assessment the methods were equal, but for talitrid sampling quadrat sieving was more efficient.