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Sand Dunes (sand + dune)
Kinds of Sand Dunes Terms modified by Sand Dunes Selected AbstractsA reconstruction of the history of a Holocene sand dune on Great Barrier Island, northern New Zealand, using pollen and phytolith analysesJOURNAL OF BIOGEOGRAPHY, Issue 6 2000M. Horrocks Abstract Aim, To reconstruct the history of a Holocene sand dune using pollen and phytolith analyses, and to identify the strengths, weaknesses and compatibility of these two methods in the interpretation of Quaternary coastal environments. Location, Great Barrier Island, northern New Zealand. Methods, Pollen and phytolith analyses were carried out on a sequence through a Holocene sand dune containing a palaeosol. Results, Phytoliths were present throughout the sequence. Grass phytoliths increased at the expense of tree phytoliths following fire disturbance. Pollen (and spores) was preserved only in the palaeosol part of the profile. Pteridium fern spores increased at the expense of tall tree pollen following the fire disturbance. Main conclusions, Lack of phytolith production by many species and problems of taxonomic specificity in many others restricts the usefulness of phytolith analysis to defining only broad vegetation types. In New Zealand, gymnosperms are invisible in the phytolith record and ferns are extremely under-represented. In contrast, pollen analysis usually provides a great deal of information regarding the composition of a particular vegetation type. The loss of microscopic charcoal fragments during the phytolith extraction process is a disadvantage in the reconstruction of environments where fires have occurred. The greater durability of phytoliths compared with pollen means that phytoliths may be found in sediments where pollen has not been preserved. The phytolith record may also provide evidence of wetter environments that are not apparent in the pollen record. Unlike grass pollen, which is widely dispersed and therefore blurs the spatial record, the presence of grass phytoliths in sediments indicates a local source. The simultaneous application of both methods potentially provides a powerful tool in ecological interpretation and the reconstruction of Quaternary coastal environments. [source] Greater capacity for division of labour in clones of Fragaria chiloensis from patchier habitatsJOURNAL OF ECOLOGY, Issue 3 2007SERGIO R. ROILOA Summary 1Unlike non-clonal plants, clonal plants can develop a division of labour in which connected ramets specialize to acquire different, locally abundant resources. This occurs as a plastic response to a patchy environment where two resources tend not to occur together and different ramets experience high availabilities of different resources. We hypothesized that if division of labour is an important advantage of clonal growth in such environments in nature, then clones from habitats where resource availabilities are negatively associated should show a greater capacity for division of labour than clones from habitats where resource availabilities are more uniform. 2To test this, we collected clones of Fragaria chiloensis from sand dune and grassland sites in each of three regions of the central coast of California, grew pairs of connected or severed ramets under low light and high N or under high light and low N, and measured leaf area, chlorophyll content and final dry mass. Given that previous work has indicated that high availabilities of light and N show a stronger tendency not to occur together in the dune than in the grassland sites, we expected that clones from dunes would show greater capacity for division of labour than clones from grasslands. 3Clones from dunes showed a greater capacity than clones from grasslands to specialize for acquisition of abundant N via high proportional mass of roots. Clones from the two types of habitats showed similar capacity to specialize for acquisition of abundant light via high leaf area and chlorophyll content of leaves. Specialization via leaf area and chlorophyll content took place mainly within the first half of the 60-day experiment. 4These results provide evidence that division of labour in a clonal plant has been selected for in natural habitats where high levels of different resources tend to be spatially separated. Results also show that division of labour can occur, not just via allocation of mass, but also via physiological traits, and that both morphological and physiological specialization can take place within a few weeks. 5Clonal plants dominate many habitats and include many highly invasive species. Division of labour is one of the most striking potential advantages of clonal growth, and is a remarkable instance of phenotypic plasticity in plants. This study further suggests that division of labour in clonal plants is an instance of adaptive plasticity and could therefore play a part in their widespread ecological success. [source] The effect of initial seed density on the structure of a desert annual plant communityJOURNAL OF ECOLOGY, Issue 3 2002Christopher J. Lortie Summary 1,Few experiments directly test the role of density dependence in natural plant communities. 2,We tested (i) whether different initial seed densities of the entire seed bank of an annual plant community affected performance (emergence, mean plant biomass and survival) and (ii) whether density-dependent processes were operating within the communities. We also tested whether life-stage, year and soil moisture (both on a topographic gradient and in an experimental manipulation) influenced the effects of seed density. 3,We considered two distinct phases: seed to emergent seedlings, and emergent seedlings to established plants. 4,The seed bank was collected from a semistabilized sand dune in the Negev Desert, Israel. This was added to sieved sand in plots at the same site at four different initial seed densities: 1/16×, 1/4×, 1× (natural seed density) and 2×. The experiment was repeated for three consecutive growing seasons. 5,Emergence of seedlings was significantly influenced by initial seed density in all 3 years, with higher initial seed densities having lower rates of emergence. 6,Mean final plant size was negatively density dependent and consistently unaffected by the initial seed density sown. 7,In general, there were no strong interactions of topographic position with initial seed density, processes within the vegetation were not density dependent and the experimental addition of water did not influence any of the performance measures tested. Density-dependent processes vary from year to year, while moisture effects do not. 8,We conclude that seedling emergence and some processes in the established plant community are density dependent, but the established plant community is also affected by other processes, such as resource limitation. [source] Have we neglected the societal importance of sand dunes?AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 4 2010An ecosystem services perspective Abstract 1.Coastal sand dunes are widespread worldwide, including around the coasts of the British Isles and Europe, providing a wide range of functions some of which are recognized for their socio-economic benefits. 2.In some localities, their contribution to coastal defence and to tourism and regional character have been acknowledged in local plans, but this is far from ubiquitous. 3.A rapid assessment was undertaken of the range of ecosystem services provided by coastal sand dune systems, using the Millennium Ecosystem Assessment ecosystem services classification augmented with habitat- and locally-appropriate additions. 4.Sand dunes were shown to provide a wide range of provisioning, regulatory, cultural and supporting services, many of which remain substantially overlooked. 5.Although the importance of coastal sand dune for a diversity of characteristic and often rare organisms from a variety of taxa has been addressed, many of the broader ecosystem services that these habitats provide to society have been overlooked. This suggests that coastal sand dune systems are neglected ecosystems of significant and often under-appreciated societal value. Copyright © 2010 John Wiley & Sons, Ltd. [source] Disentangling the relative effects of environmental versus human factors on the abundance of native and alien plant species in Mediterranean sandy shoresDIVERSITY AND DISTRIBUTIONS, Issue 4 2010Marta Carboni Abstract Aim, Mediterranean coastal sand dunes are characterized by both very stressful environmental conditions and intense human pressure. This work aims to separate the relative contributions of environmental and human factors in determining the presence/abundance of native and alien plant species in such an extreme environment at a regional scale. Location, 250 km of the Italian Tyrrhenian coast (Region Lazio). Methods, We analysed alien and native plant richness and fitted generalized additive models in a multimodel-inference framework with comprehensive randomizations to evaluate the relative contribution of environmental and human correlates in explaining the observed patterns. Results, Native and alien richness are positively correlated, but different variables influence their spatial patterns. For natives, human population density is the most important factor and is negatively related to richness. Numbers of natives are unexpectedly lower in areas with a high proportion of natural land cover (probably attributable to local farming practices) and, to a lesser degree, affected by the movement of the coastline. On the other hand, alien species richness is strongly related to climatic factors, and more aliens are found in sectors with high rainfall. Secondarily, alien introductions appear to be related to recent urban sprawl and associated gardening. Main conclusions, Well-adapted native species in a fragile equilibrium with their natural environment are extremely sensitive to human-driven modifications. On the contrary, for more generalist alien species, the availability of limited resources plays a predominant role. [source] Palaeomonsoon variability in the southern fringe of the Badain Jaran Desert, China, since 130 ka BPEARTH SURFACE PROCESSES AND LANDFORMS, Issue 3 2006Quanzhou Gao Abstract Taking the Chagelebulu Stratigraphic Profile as a typical example, a comprehensive study has been conducted to elucidate the palaeoclimatic and geomorphic evolution patterns in the southern fringe of the Badain Jaran Desert, which were found to be complex and polycyclic in the past 130 ka. However, the fluctuating magnitude is not as remarkable as that in the eastern China sandy region. The shift in climate from interglacial to glacial and the uplift process of the Qinghai,Xizang Plateau are the two leading forces driving the evolution of the climate and desert landforms in this area. Seventeen cycles of cold, dry and warm, humid climatic stages were recognized in the Upper Pleistocene Series of the profile. The sharp uplift of the Qinghai,Xizang Plateau superimposed a cool and arid climatic trend in this area. As a result of the climatic changes, the desert in this area has undergone multiple stages of expansion and contraction since 130 ka bp. The middle Holocene Epoch and the early stage of the Late Pleistocene Period were the main periods when the sand dunes became stabilized, and the early and late phases of the Holocene Epoch and late phase of the Pleistocene Epoch were the main periods when the previously stabilized sand dunes became mobile. The late phase of the Pleistocene Epoch was the most mobile stage, when the aeolian sand activities formed the essential geomorphic pattern of the Badain Jaran Desert. Copyright © 2005 John Wiley & Sons, Ltd. [source] Testing the assumptions of chronosequences in successionECOLOGY LETTERS, Issue 5 2008Edward A. Johnson Abstract Many introductory ecology textbooks illustrate succession, at least in part, by using certain classic studies (e.g. sand dunes, ponds/bogs, glacial till, and old fields) that substituted space for time (chronosequence) in determining the sequences of the succession. Despite past criticisms of this method, there is continued, often uncritical, use of chronosequences in current research on topics besides succession, including temporal changes in biodiversity, productivity, nutrient cycling, etc. To show the problem with chronosequence-based studies in general, we review evidence from studies that used non-chronosequence methods (such as long-term study of permanent plots, palynology, and stand reconstruction) to test the space-for-time substitution in four classic succession studies. In several cases, the tests have used the same locations and, in one case, the same plots as those in the original studies. We show that empirical evidence invalidates the chronosequence-based sequences inferred in these classic studies. [source] NATURAL SELECTION ALONG AN ENVIRONMENTAL GRADIENT: A CLASSIC CLINE IN MOUSE PIGMENTATIONEVOLUTION, Issue 7 2008Lynne M. Mullen We revisited a classic study of morphological variation in the oldfield mouse (Peromyscus polionotus) to estimate the strength of selection acting on pigmentation patterns and to identify the underlying genes. We measured 215 specimens collected by Francis Sumner in the 1920s from eight populations across a 155-km, environmentally variable transect from the white sands of Florida's Gulf coast to the dark, loamy soil of southeastern Alabama. Like Sumner, we found significant variation among populations: mice inhabiting coastal sand dunes had larger feet, longer tails, and lighter pigmentation than inland populations. Most striking, all seven pigmentation traits examined showed a sharp decrease in reflectance about 55 km from the coast, with most of the phenotypic change occurring over less than 10 km. The largest change in soil reflectance occurred just south of this break in pigmentation. Geographic analysis of microsatellite markers shows little interpopulation differentiation, so the abrupt change in pigmentation is not associated with recent secondary contact or reduced gene flow between adjacent populations. Using these genetic data, we estimated that the strength of selection needed to maintain the observed distribution of pigment traits ranged from 0.0004 to 21%, depending on the trait and model used. We also examined changes in allele frequency of SNPs in two pigmentation genes, Mc1r and Agouti, and show that mutations in the cis -regulatory region of Agouti may contribute to this cline in pigmentation. The concordance between environmental variation and pigmentation in the face of high levels of interpopulation gene flow strongly implies that natural selection is maintaining a steep cline in pigmentation and the genes underlying it. [source] Crayfish as geomorphic agents and ecosystem engineers: effect of a biomass gradient on baseflow and flood-induced transport of gravel and sand in experimental streamsFRESHWATER BIOLOGY, Issue 1 2003B. Statzner SUMMARY 1.,Using experimental streams, we studied the impact of the crayfish Orconectes limosus on (i) the transport of gravel and sand at baseflow; (ii) the sediment surface (bedform, particle consolidation, proportion of sand, algal and gravel cover); and (iii) the critical shear stress (,C) causing incipient gravel and sand motion during simulated floods. We examined (i) and (ii) in experimental outdoor flumes that replicated riffle-pool sequences and (iii) in a larger laboratory flume, in which we exposed sediments retrieved from the outdoor flumes to a progressively increasing discharge. 2.,Habitat changes induced by crayfish, such as bedform alterations in riffles (downstream displacement of riffle heads) and the increase of gravel on sand dunes in pools, had major impacts on the spatial and temporal patterns of the baseflow transport of gravel and sand. 3.,In addition to their impact on bedform in riffles and on gravel cover in pools, crayfish prevented the physical consolidation of particles in riffles and reduced the algal cover and the proportion of sand in the surface layer in both riffles and pools. These crayfish impacts on sediment surface variables had complex, interacting effects on the mobilisation of gravel and sand during subsequent flood simulations. For sand, crayfish progressively decreased the ,C (i.e. the sum of bedform drag and skin friction) by about 50% along the entire biomass gradient in pools, whereas the presence of crayfish abruptly decreased the ,C by about 75% in riffles. For gravel, the discharge causing motion in riffles produced a shear stress (in terms of skin friction) on an even bedform that was about 75% lower in all flumes with crayfish compared with the flumes without crayfish. Crayfish had no impact on ,C for gravel in pools. 4.,Scaling-up these experimental results to real streams suggests that crayfish could affect the patch dynamics of major sediment transport events and habitat suitability for other organisms that, at larger spatial scales, could increase the overall spatio-temporal habitat diversity and thus the overall structural and functional biodiversity of lotic communities. [source] Geoarchaeological study of the Phoenician cemetery of Tyre-Al Bass (Lebanon) and geomorphological evolution of a tomboloGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 3 2008Pilar Carmona The geoarchaeological record of the Phoenician necropolis of Al Bass (Lebanon) provides information concerning the geomorphological evolution of a late Holocene tombolo. Physical and chemical analysis of sediments indicates that the cemetery (9th century B.C.) was located near a littoral lagoon, between the dunes of a cuspate spit pointing toward the island of Tyre. From the sea apex of this spit, the moles mentioned in historical chronicles were constructed. Once mainland and island were connected, at the northern coast (where the port of Sidon was located), a sediment trap was formed, which quickly filled with silt. Afterwards, an extensive field of sand dunes buried all the archaeological remains from Phoenician to Roman times. © 2008 Wiley Periodicals, Inc. [source] Sap flow of Artemisia ordosica and the influence of environmental factors in a revegetated desert area: Tengger Desert, ChinaHYDROLOGICAL PROCESSES, Issue 10 2010Huang Lei Abstract Artemisia ordosica is considered as an excellent sand-fixing plant in revegetated desert areas, which plays a pertinent role in stabilizing the mobile dunes and sustaining the desert ecosystems. Stem sap flows of about 10-year-old Artemisia ordosica plants were monitored continuously with heat balance method for the entire growing season in order to understand the water requirement and the effects of environmental factors on its transpiration and growth. Environment factors such as solar radiation, air temperatures, relative humidity, wind speed and precipitation were measured by the eddy covariance. Diurnal and seasonal variations of sap flow rate with different stem diameters and their correlation with meteorological factors and reference evapotranspiration were analysed. At the daily time scale, there was a significantly linear relationship between sap flow rate and reference evapotranspiration with a correlation coefficient of R2 = 0·6368. But at the hourly time scale, the relationship of measured sap flow rate and calculated reference evapotranspiration (ET0) was affected by the precipitation. A small precipitation would increase the sap flow and the ET0; however, when the precipitation is large, the sap flow and ET0 decrease. Leaf area index had a coincident variation with soil water content; both were determined by the precipitation, and meteorological factors were the most significant factors that affected the sap flow of Artemisia ordosica in the following order: solar radiation > vapour pressure deficit > relative humidity > air temperature > wind speed. The close correlation between daily sap flow rate and meteorological factors in the whole growing season would provide us an accurate estimation of the transpiration of Artemisia ordosica and rational water-carrying capacity of sand dunes in the revegetated desert areas. Copyright © 2010 John Wiley & Sons, Ltd. [source] What is the origin of the carabid beetle fauna of dry, anthropogenic habitats in western Europe?JOURNAL OF BIOGEOGRAPHY, Issue 4 2000Johan Andersen Abstract Aim To study the origin of the carabid beetle fauna of dry, open anthropogenic habitats. Location Various parts of Europe. Methods Collecting by hand in habitats influenced by humans (arable land, sand pits, ruderal places, road verges, meadows) and naturally open habitats such as talus, supralittoral sand dunes, alvar as well as littoral habitats in south and central Scandinavia. Studies made in other parts of Europe were included in the discussion. Results and conclusion The material comprises about 37,700 specimens. About 8% of the Scandinavian species occurring in anthropogenic habitats may have a littoral origin, about 10% may originate from forests whereas about 9% are euryoecious. A majority of the species (about 66%) originate from primarily open, dry habitats and many of them constitute a steppe or steppe-like element. They invaded the bare landscape soon after the deglaciation and probably survived in naturally open habitats (supralittoral sand dunes, talus, alvar, old riverbeds) during the postglacial warm period, but some species have a recent origin in Scandinavia. [source] Palaeoenvironmental evolution and sea-level fluctuations along the southeastern Pampa grasslands coast of Argentina during the Holocene,JOURNAL OF QUATERNARY SCIENCE, Issue 3 2006Isabel Vilanova Abstract Holocene pollen and diatom analyses and complementary data from ,18O and ,13C, malacology and sedimentology have provided a detailed record of vegetation history and palaeoenvironmental change at arroyo Las Brusquitas, on the southeastern coast of the pampas of Argentina especially in relation to past sea levels. Holocene palaeosalinity trends were estimated by Detrended Correspondence Analysis and by salinity indexes based on pollen and diatom data. As a consequence of sea-level rise from the postglacial an extensive wave-cut platform formed over which Holocene infilling sequences were deposited unconformably. In these sequences, variation in pollen and diatom assemblages occurred in agreement with changes in mollusc diversity and abundance, isotope values, and sediment deposits. Between ca. 6700 and 6190 14C yr BP (6279,6998,cal. yr BP) saline conditions predominated in an environment highly influenced by tides and salt water during the Holocene sea-level highstand. Between ca. 6200 and 3900 14C yr BP (4235,4608,cal. yr BP) shallow brackish water bodies formed surrounded by saltmarsh vegetation that became more widespread from 5180 14C yr BP (5830,6173,cal. yr BP) to 3900 14C yr BP in relation to a sea-level stabilisation period within the regression phase. Less saline conditions marked by frequent variations in salinity predominated between ca. 3900 and 2040,yr 14C BP (1830,2160,cal. yr BP). The intertidal saltmarsh environment changed into a brackish marsh dominated by freshwater conditions and sporadic tidal influence. Halophytic vegetation increased towards ca. 200014C yr BP indicating that saline conditions may be due to either desiccation or an unusually high tide range with rare frequency. After ca. 2000 14C yr BP the sedimentary sequences were buried by aeolian sand dunes. Changes in Holocene vegetation and environments in Las Brusquitas area are in agreement with data obtained from various southeastern coastal sites of the Pampa grasslands. Copyright © 2005 John Wiley & Sons, Ltd. [source] Spatial patterns of association at local and regional scales in coastal sand dune communitiesJOURNAL OF VEGETATION SCIENCE, Issue 5 2009Estelle Forey Abstract Questions: Are positive understorey-dominant associations important in physically severe dune communities and does the strength of positive associations vary with disturbance at the local scale and with stress at the regional scale? Do associational patterns observed at the neighbourhood scale predict diversity at higher scales? Location: Coastal sand dunes, Aquitaine (France). Methods: Associational patterns with five dominant species were recorded along a local gradient of disturbance and a 240-km long regional gradient. Density, richness, cover and variance ratio of understorey species were recorded in quadrats located in dominant and in open areas. Spatial pattern of dominant plant species was recorded using a distance-based method. Results: Positive understorey-dominant associations were most frequent at both regional and local scale, although negative associations with understorey species were observed for one of the five dominants. At the regional scale, there was a shift in the magnitude of spatial associations, with higher positive associations in the most stressful sites, whereas spatial associations where not affected by the local disturbance gradient. Positive associations were not related to the size of the dominants but rather influenced by the identity of the dominant species. Conclusions: Our study highlights the potential crucial role of facilitation together with the importance of turnover of the dominants in explaining large-scale variation in diversity. However, because positive associations may also be attributed to environmental heterogeneity or co-occurrence of microhabitat preferences of species, experiments are needed to fully assess the relative importance of facilitation versus other drivers of community diversity. [source] Oscillating vegetation dynamics in a wet heathlandJOURNAL OF VEGETATION SCIENCE, Issue 1 2005Katharina E. Urban Abstract. Question: The significance of disturbances caused by periodical inundation was investigated with respect to its effects on vegetation dynamics, species richness and fluctuations, and to the relevance of certain plant properties. Location and Method: At a sod-cut stand within nutrient-poor inland sand dunes, permanent plots along a transect were surveyed over a period of up to nine years after sod cutting. Results: In contrast to never inundated plots, periodically inundated plots were characterized by low vegetation cover and by high numbers of species belonging to many different communities, each of them with a low cover. Periodical inundations favoured the presence of pioneers, species tolerant of disturbances, species adapted to wet conditions and stoloni-ferous species. Furthermore, annual fluctuations of species within each plot were higher and most species occurred only sporadically. Discussion: A comprehensive model is presented describing the relevant processes identified in the littoral zone. Changing water tables result in the creation of gaps. The re-colonization of these gaps follows mainly from vegetative regeneration and less to the dispersion of diaspores. Highest species numbers in the zone of moderate disturbances result from a high rate of re-colonization in spite of local extinctions following each disturbance event. It is suggested that colonization abilities are among the most important features for species occurrence at a site rich in disturbances (more important than competitive abilities and more important than a slow rate of displacement). For nature conservation such sites are very important, because they allow (rare) pioneer species to survive for longer periods of time. [source] Environmental limits to the distribution of Scaevola plumieri along the South African coastJOURNAL OF VEGETATION SCIENCE, Issue 1 2003Craig I. Peter Dyer (1967) Abstract. Scaevola plumieri is an important pioneer on many tropical and subtropical sand dunes, forming a large perennial subterranean plant with only the tips of the branches emerging above accreting sand. In South Africa it is the dominant pioneer on sandy beaches along the east coast, less abundant on the south coast and absent from the southwest and west coasts. Transpiration rates (E) of S. plumieri are predictably related to atmospheric vapour pressure deficit under a wide range of conditions and can therefore be predicted from measurement of ambient temperature and relative humidity. Scaling measurements of E at the leaf level to the canopy level has been demonstrated previously. Using a geographic information system, digital maps of regional climatic variables were used to calculate digital maps of potential transpiration from mean monthly temperature and relative humidity values, effectively scaling canopy level transpiration rates to a regional level. Monthly potential transpiration was subtracted from the monthly median rainfall to produce a map of mean monthly water balance. Seasonal growth was correlated with seasonal water balance. Localities along the coast with water deficits in summer corresponded with the recorded absence of S. plumieri, which grows and reproduces most actively in the summer months. This suggests that reduced water availability during the summer growth period limits the distribution of S. plumieri along the southwest coast, where water deficits develop in summer. Temperature is also important in limiting the distribution of S. plumieri on the southwest coast of South Africa through its effects on the growth and phenology of the plant. [source] Approaches to landcare,a century of soil conservation in IcelandLAND DEGRADATION AND DEVELOPMENT, Issue 2 2005A. Arnalds Abstract Organized soil conservation in Iceland began in 1907, as a response to severe land degradation and desertification that was threatening the existence of several communities. During the first 75 years, many of the most threatening areas of accelerated soil erosion were fenced and seeded with sand stabilizers. These projects had a high success rate, halting the advancement of sand dunes and other forms of highly accelerated erosion. However, they were limited in scope, and often concentrated on the symptoms of the problems rather than the underlying causes, such as improper grazing management. On a national scale, not enough was being achieved in mitigating the extensive ecosystem degradation. This period of soil conservation in Iceland was characterized by single-issue, top-down approaches, a lack of appropriate incentives for soil conservation and weak laws for protection of the rangelands. During the last two decades there has been a gradual shift to more participatory strategies, community involvement, and ecosystem management for multiple benefits. These changes have greatly increased community involvement in projects, stimulated conservation awareness and improved land use. The ties between agricultural policy and soil-conservation issues are also being strengthened, especially by linking part of governmental subsidies for sheep production to land-use factors. Copyright © 2005 John Wiley & Sons, Ltd. [source] Living on the edge: demographic and phylogeographical patterns in the woodlouse-hunter spider Dysdera lancerotensis Simon, 1907 on the eastern volcanic ridge of the Canary IslandsMOLECULAR ECOLOGY, Issue 15 2007LETICIA BIDEGARAY-BATISTA Abstract The Eastern Canary Islands are the emerged tips of a continuous volcanic ridge running parallel to the northeastern African coast, originated by episodic volcanic eruptions that can be traced back to the Miocene and that, following a major period of quiescence and erosion, continued from the Pliocene to the present day. The islands have been periodically connected by eustatic sea-level changes resulting from Pleistocene glacial cycles. The ground-dwelling spider Dysdera lancerotensis Simon, 1907 occurs along the entire ridge, except on recent barren lavas and sand dunes, and is therefore an ideal model for studying the effect of episodic geological processes on terrestrial organisms. Nested clade and population genetic analyses using 39 haplotypes from 605 base pairs of mitochondrial DNA cytochrome c oxidase I sequence data, along with phylogenetic analyses including two additional mitochondrial genes, uncover complex phylogeographical and demographic patterns. Our results indicate that D. lancerotensis colonized the ridge from north to south, in contrast to what had been expected given the SSW-NNE trend of volcanism and to what had been reported for other terrestrial arthropods. The occurrence of several episodes of extinction, recolonization and expansion are hypothesized for this species, and areas that act as refugia during volcanic cycles are identified. Relaxed molecular clock methods reveal divergence times between main haplotype lineages that suggest an older origin of the northern islets than anticipated based on geological evidence. This study supports the key role of volcanism in shaping the distribution of terrestrial organisms on oceanic islands and generates phylogeographical predictions that warrant further research into other terrestrial endemisms of this fascinating region. [source] Effects of long-term grazing management on sand dune vegetation of high conservation interestAPPLIED VEGETATION SCIENCE, Issue 1 2010Katharina Plassmann Abstract Question: Can long-term grazing management maintain and restore species-rich sand dune plant communities within a sand dune site of high conservation interest? Location: Newborough Warren, North Wales, UK. Methods: Vegetation changes that occurred between 1987 and 2003, subsequent to grazing by domestic livestock being introduced to the site after decades with little or no stock grazing, were analysed using data collected from permanent monitoring quadrats over a 16-year period. Results: At the plant community level, grazing brought about a shift from a tall-grass dominated, species-poor community to a more species-rich community in the dry dunes, but did not change community type in dune slacks. However, at the species level, grazing enhanced the abundance of some desired perennial, annual and biennial species, graminoids and bryophytes in both habitat types. The increased frequency of positive indicator species for habitat condition suggests that grazing was beneficial for species of conservation interest. Ellenberg nitrogen (N) values decreased after grazing in dry habitats but showed no long-term change independent of grazing, suggesting no increase in site fertility over the study period. Surprisingly, light (L) values also decreased in the dry dunes after grazing. Conclusions: Long-term grazing management can play an important role for the conservation of dune communities and associated species. Because of its positive effects on species diversity, plant communities and habitat condition in sand dunes, livestock grazing is recommended for conservation management. [source] Have we neglected the societal importance of sand dunes?AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 4 2010An ecosystem services perspective Abstract 1.Coastal sand dunes are widespread worldwide, including around the coasts of the British Isles and Europe, providing a wide range of functions some of which are recognized for their socio-economic benefits. 2.In some localities, their contribution to coastal defence and to tourism and regional character have been acknowledged in local plans, but this is far from ubiquitous. 3.A rapid assessment was undertaken of the range of ecosystem services provided by coastal sand dune systems, using the Millennium Ecosystem Assessment ecosystem services classification augmented with habitat- and locally-appropriate additions. 4.Sand dunes were shown to provide a wide range of provisioning, regulatory, cultural and supporting services, many of which remain substantially overlooked. 5.Although the importance of coastal sand dune for a diversity of characteristic and often rare organisms from a variety of taxa has been addressed, many of the broader ecosystem services that these habitats provide to society have been overlooked. This suggests that coastal sand dune systems are neglected ecosystems of significant and often under-appreciated societal value. Copyright © 2010 John Wiley & Sons, Ltd. [source] Risk factors in relation to human deaths and other tsunami (2004) impacts in Sri Lanka: the fishers'-eye view,AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2009A. J. Venkatachalam 1.This study examines the perceptions of 500 Sri Lankan fishers about influences on the outcome of the 2004 Asian tsunami. It is based upon analysis of questionnaire data on 13 natural environmental and development risk factors, in relation to human deaths and house damage (impact indicators). 2.Mangroves, coral reefs and sand dunes afforded protection against tsunami damage (67,94% of fisher responses), as did housing and roads. 3.Fishers overall believed rivers/estuaries, concave coastlines and hotels exacerbated impacts. However, a significantly greater proportion of fishers living within 100,m of the coast reported that rivers/estuaries had a protective role than those living further inland. Rivers seemingly diverted ,tsunami water' far inland, where it overflowed and caused damage. 4.Risk and damage are multi-faceted concepts and measurable in different ways. Findings are considered in the light of ecological studies and modelling, with special reference to mangroves, whose alleged protective role has become equivocal during post-tsunami research. 5.Insights of fishers and other communities with intuitive knowledge add a valuable perspective to the understanding of natural disasters and environmental change. This approach is seen as complementary rather than an alternative approach to purely ,scientific' research. Copyright © 2008 John Wiley & Sons, Ltd. [source] Factors affecting habitat selection in a specialist fossorial skinkBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2009AARON C. GREENVILLE Habitat specialists maximize their fitness by using a subset of the habitats that are potentially available to them and fare poorly if they move elsewhere. The factors that constrain habitat use are diverse and often difficult to identify, but are important to distinguish if we are to understand the trade-offs that drive species to become specialists. In the present study, we investigated habitat use in a fossorial skink, Lerista labialis, and explore the factors that confine it to the crests of sand dunes in the Simpson Desert, central Australia. Models positing that L. labialis selects dune crests because of their sparse cover of vegetation, more favourable temperatures, and greater abundance of preferred prey, received no support. Instead, a model positing that dune crests provide soft and less compacted sand that facilitates movement by L. labialis, was strongly supported. Sand on the crests was consistently softer that that on the sides and swales of the dunes; the skinks preferred soft rather than hard sand for movement in captivity, and were captured more often on experimentally softened sand than on compacted sand in the field. There was no evidence that L. labialis responds to attributes of the substrate other than softness because captive animals used loose sand from the dune crests, sides, and swales equally. We suggest that the dune crest environment allows L. labialis to reduce the energetic costs of locomotion, provides priority of access to the subterranean galleries of its termite prey, and also a secure refuge from surface-active predators and extreme surface temperatures. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 531,544. [source] Bahiaxenidae, a "living fossil" and a new family of Strepsiptera (Hexapoda) discovered in BrazilCLADISTICS, Issue 6 2009Freddy Bravo An adult male of a newly discovered strepsipteran species from Brazil,Bahiaxenos relictus,is described. A new family Bahiaxenidae is suggested based on cladistic analyses of comprehensive morphological data sets with a broad taxon sampling including the stem group. It is unambiguously placed as the sister group of all other extant families of Strepsiptera. Bahiaxenos relictus is the only species of basal, i.e. non-stylopidian, Strepsiptera occurring in the New World. It appears to be a relict taxon that has survived in the fossil sand dunes of the São Francisco River (Bahia State). The loss of the 8th antennomere and the greatly reduced labrum are autapomorphies of Strepsiptera s.s. excluding Bahiaxenidae. The sister group relationship between,Protoxenidae and the remaining Strepsiptera, and between ,Cretostylops and a clade comprising ,Mengea and Strepsiptera s.s., is confirmed, as is the monophyly of Stylopidia and Stylopiformia. [source] | ||||||||||||||||||||||||||||