EVOLUTION, Issue 2 2005
Glacomo Bernardi
Abstract With 18 closely related endemic species that radiated in a diversity of ecological niches, the California surfperches (Embiotocidae) species flock is a good candidate for the study of sympatric speciation. Resource partitioninghas been suggested as an important driving force in the radiation of the surfperch family. Within the family, two congeneric sister species, Embiotoca jacksoni and E. lateralis, are known to compete strongly for a preferred singleood resource and may be used as a model of ecological interactions for the family. Along the California coast, the distribution of the two species differs. Embiotoca jacksoni has a continuous range, whereas E. lateralis shows a disjunction with a distribution gap in the Southern California Bight. Two hypotheses may explain this disjunct distribution. Ecological competition may have displaced E. lateralis in favor of E. jacksoni. Alternatively, a common vicariant event may have separated the species into northern and southern populations, followed by secondary contactin E. jacksoni but not in E. lateralis. The two hypotheses predict different phylogeographic and demographic signatures. Using a combined phylogeographic and coalescent approach based on mitochondrial control region data, we show that vicariance can only account for a portion of the observed divergences. Our results are compatible with a significant role played by ecological competition in the southern range of the species. [source]

SEASONAL GROWTH AND PHENOTYPIC VARIATION IN PORPHYRA LINEARIS (RHODOPHYTA) POPULATIONS ON THE WEST COAST OF IRELAND,

JOURNAL OF PHYCOLOGY, Issue 1 2007
Elena Varela-Álvarez
The phenology and seasonal growth of Porphyra linearis Grev. were investigated in two morphologically dissimilar populations from the west coast of Ireland. Thallus size and reproductive status of individuals were monitored monthly between June 1997 and June 1998. Both populations exhibited a similar phenology: gametophyte stages appeared on the shore in October, with spermatangial and zygotosporangial sori appearing the following February; the gametophyte stage began to degenerate in April and had disappeared completely by June. However, significant differences in growth and reproduction in the field and in cultures of plants from the two populations were observed. Thallus length and width of individuals from one population were significantly longer throughout the sample period, and reproduction and sporulation occurred 1 month earlier. Also, in situ relative growth rates (RGRs) of plants differed significantly and were correlated with different climatic factors (sunshine, day length, irradiance, rainfall, seawater temperature, and intertidal temperatures), suggesting that plants were affected by two different microhabitats. At one site, blades were more exposed to wave action, sunshine, and extreme minimum temperatures, while at the other site, blades were more protected in winter, spring, and early summer. In culture, RGRs of blades from the second site were higher than RGRs of blades from the first site under short days, corroborating the field results and suggesting a degree of phenotypic differentiation between the two populations. However, there were no sequence divergences of the RUBISCO spacer between strains of the two P. linearis populations. [source]

PRESENCE OF SPOROPHYLLS IN FLOATING KELP RAFTS OF MACROCYSTIS SPP. (PHAEOPHYCEAE) ALONG THE CHILEAN PACIFIC COAST,

JOURNAL OF PHYCOLOGY, Issue 5 2005
Erasmo C. Macaya
Some species of macroalgae continue to live for extended periods of time after detachment and may even maintain reproductive structures, yet very little is known about this process. Here, we describe the presence of sporophylls (with sporogenous tissues) on floating kelp rafts of Macrocystis spp. along the coast of Chile. Surveys were conducted at nine sites (18,50° S) during austral summer 2002, and floating kelp rafts were seen and collected at seven of these nine sites (between 22 and 50° S). Fifteen (26.8%) of the 56 samples had sporophylls, indicating maintenance of sporophylls after detachment. Some of the kelp sporophytes with reproductive blades showed signs of having been afloat for long periods (indicated by the large size of attached stalked barnacles). Additionally, experiments showed that floating kelps released viable zoospores. To understand the reproductive dynamics of floating kelps, we compared these results with information from attached populations of Macrocystis spp. at nearby coastal sites. In general, attached kelp had higher proportions of sporophylls than floating rafts, suggesting that detachment may negatively affect reproductive status. Nevertheless, floating kelps remained functionally reproductive, suggesting that zoospores may be dispersed via floating rafts. Published reports on other macroalgae indicate that some species (Lessoniaceae, Fucaceae, and Sargassaceae) are fertile and probably release zoospores or zygotes while floating or drifting in ocean currents. Because dispersal distances achieved by spores of most macroalgae are relatively short, release of spores from floating algae may be an alternative mechanism of long-distance dispersal. [source]

PATTERNS OF INTERSPECIFIC INTERACTIONS IN THE ULVA -DOMINATED INTERTIDAL COMMUNITY IN A SOUTHERN COAST OF KOREA

JOURNAL OF PHYCOLOGY, Issue 2000
Y.J. Bhang
In the southern coast of Korea, rocky intertidal zones where green tide commonly occurs are dominated by Ulva pertusa, red algal turf (a mixed stand of Gigartina intermedia and Gigartina teedii) and species of Enteromorpha with highly opportunistic occurrence. To investigate their interspecific interactions, a field experiment was carried out using press effect of one species removal from permanent plots (20 x 20cm) set up on two different tidal heights. Mechanisms of interaction were also attempted using artificial plants to test the possible effects of shading, scouring, allelopathy of U. pertusa on the turf algae. The turf-forming red algae lowered the abundance of U. pertusa presumably by inhibiting the recruitment of U. pertusa; this effect was consistent along the tidal height. However, the greater abundance of Enteromorpha was observed in the presence of turf in the upper zone, indicating a positive effect of turf on Enteromorpha. Once U. pertusa was successfully recruited and grown to the adult plant, it inhibited the growth of turf by shading, which was effective both in winter and summer regardless of desiccation stress. No scouring and allelopathic effects of U. pertusa on the turf were detected. When an open substrate was provided, Enteromorpha colonized the space faster than any other species in the upper zone, but the turf was the fastest one followed by U. pertusa and Enteromorpha in the lower zone. Results indicated that patterns of interaction represented a complex network with no ultimate winner and the outcomes of interaction varied over time and space. [source]

DETERMINATION OF MANATEE POPULATION TRENDS ALONG THE ATLANTIC COAST OF FLORIDA USING A BAYESIAN APPROACH WITH TEMPERATURE-ADJUSTED AERIAL SURVEY DATA

MARINE MAMMAL SCIENCE, Issue 3 2004
Bruce A. Craig
Abstract In many animal population survey studies, the construction of a stochastic model provides an effective way to capture underlying biological characteristics that contribute to the overall variation in the data. In this paper we develop a stochastic model to assess the population trend and abundance of the Florida manatee, Trichechus manatus latirostris, along the Atlantic coast of the state, using aerial survey data collected at winter aggregation sites between 1982 and 2001. This model accounts for the method by which the manatees were counted, their movements between surveys, and the behavior of the total population over time. The data suggest an overall increase in the population from 1982 to 1989 of around 5%,7%, a reduction in growth or a leveling off (0%,4% annual growth) from 1990 to 1993, and then an increase again of around 3%,6% since 1994. In winter 2001,2002 (the most recent survey season for which analyses were done), we estimated the adult manatee population along the east coast of Florida to be 1,607 individuals (range = 1,353,1,972; 95% credible interval). Our estimate of manatee abundance corresponds well with maximum counts (approximately 1,600 manatees) produced during synoptic aerial surveys under optimal conditions. Our calculations of trends correspond well with mark and recapture analyses of trends in survival of adult manatees along the east coast through the early 1990s. Our population trend estimates since that time are more optimistic than those generated by mark-recapture models. [source]

ENVIRONMENTAL FACTORS INFLUENCING THE DISTRIBUTION OF SOUTHERN RIGHT WHALES (EUBALAENA AUSTRALIS) ON THE SOUTH COAST OF SOUTH AFRICA I: BROAD SCALE PATTERNS

MARINE MAMMAL SCIENCE, Issue 3 2004
Simon H. Elwen
Abstract Aerial surveys over the last 32 yr have shown that the distribution of southern right whales Eubalaena australis along the south coast of South Africa is markedly discontinuous, but highly predictable. A GIS was used at a variety of scales to investigate whether this pattern was related to environmental characteristics. Whale distribution was analyzed as density per 20-min bin of longitude over two temporal and spatial scales, namely 15 bins for 32 yr, and a wider scale but shorter time period, 23 bins for 19 yr, as well as using three years of GPS accuracy data (15 bins) for finer scale analysis. Environmental factors tested were depth, distance from shore, sea floor slope, protection from swell, protection from wind, and shore type. The majority of whales were concentrated in areas that provided reasonable protection from open ocean swell and seasonal winds, and had sedimentary floors with gentle slopes. They generally avoided exposed rocky shorelines. Cow-calf pairs were found significantly closer to shore and in shallower water than unaccompanied whales, particularly off sandy beaches. Habitat choice at this time of year may be related both to energy conservation for calves and lactating females (calm sea conditions) and to protection of the new-born. [source]

ENVIRONMENTAL FACTORS INFLUENCING THE DISTRIBUTION OF SOUTHERN RIGHT WHALES (EUBALAENA AUSTRALIS) ON THE SOUTH COAST OF SOUTH AFRICA II: WITHIN BAY DISTRIBUTION

MARINE MAMMAL SCIENCE, Issue 3 2004
Simon H. Elwen
Abstract Environmental factors are thought to strongly influence the distribution and predictability of the coastal distribution of southern right whales (Eubalaena australis) off South Africa. Preferred habitat had generally shallow sloping sedimentary floors and was characteristically protected from open ocean swell and prevalent seasonal winds. This study investigated whether habitat choices at smaller scales (within bays) were similar. Fine scale distribution patterns (GPS) from three years' surveys (1997, 1999, 2000) were analyzed separately within the three main concentration areas St Sebastian Bay, De Hoop, and Walker Bay (containing ,73% of cow-calf pairs and ,49% of unaccompanied adults in the whole survey region). Whale density at this scale of within particular bays did not correlate well with predicted variables, but Chi-squared analysis strongly supported results at broader scales, in all bays. Post-hoc"choice" tests between similar areas differing in only one variable revealed that cow-calves preferred (presumed) sandy substrates and especially protection from swell. The strength and predictability of preferences shown at fine scale (where individual movement and weather variability could have great influence) provide strong support for findings at larger scales and emphasize the importance of environmental factors in the habitat choice of wintering right whales. [source]

THE 200 KM CITY: BRISBANE, THE GOLD COAST, AND SUNSHINE COAST

AUSTRALIAN ECONOMIC HISTORY REVIEW, Issue 1 2009
Peter Spearritt
Brisbane; infrastructure; Southeast Queensland; traffic; urban planning Since the 1970s, several Southeast Queensland coastal towns in areas marketed as the ,Gold Coast' and the ,Sunshine Coast' have merged with each other and joined with Brisbane to become one of the world's longest urban coastal strips. The population of this 200 km long city is fast approaching three million. This urban pattern reflects the preferences of many Australians about where and in what type of housing they would like to live. The unplanned nature of this growth raises several policy challenges relating to resource use and traffic congestion. [source]

Commercializing bycatch can push a fishery beyond economic extinction

CONSERVATION LETTERS, Issue 4 2010
Aaron Savio Lobo
Abstract Tropical bottom trawling is among the most destructive fishing practices, catching large quantities of bycatch, which are usually discarded. We used questionnaire surveys of trawl fishers to look at changes in catches over the last 30 years (1978,2008) along India's Coromandel Coast. We show that catches and income from target species have declined sharply over the last two decades. Meanwhile, costs of fishing have increased substantially and now almost exceed income from target species. Over the same period, bycatch (which was traditionally discarded) has now become increasingly marketable, being sold for local consumption, and as fish meal to supply the region's rapidly growing poultry industry. Without this income from bycatch, the fishery would scarcely be economically viable. While such a change in the use of bycatch is good news in terms of reducing waste and improving livelihoods, it is also responsible for pushing the Indian bottom trawl fishery beyond the economic extinction of its target species. [source]

COMPENSATORY RESTORATION IN A RANDOM UTILITY MODEL OF RECREATION DEMAND

CONTEMPORARY ECONOMIC POLICY, Issue 4 2010
GEORGE R. PARSONS
Natural Resource Damage Assessment cases often call for compensation in non-monetary or restoration equivalent terms. In this article, we present an approach that uses a conventional economic model, a travel cost random utility model of site choice, to determine compensatory restoration equivalents for hypothetical beach closures on the Gulf Coast of Texas. Our focus is on closures of beaches on the Padre Island National Seashore and compensation for day-trip users. We identify restoration projects that compensate for beach closures and that have good alignment in terms of compensating those who actually suffer from the closures. (JEL Q26) [source]

New Evidence of Early Holocene Agriculture from the Coast of Ecuador: A Multidisciplinary Approach

CULTURE, AGRICULTURE, FOOD & ENVIRONMENT, Issue 2 2002
Karen E. Stothert
First page of article [source]

Forest blowdown impacts of Hurricane Rita on fluvial systems

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2009
Jonathan D. Phillips
Abstract Hurricane Rita, a category three hurricane which struck the US Gulf Coast near the Louisiana/Texas border in 2005, did not cause extensive river flooding. However, the storm did result in extensive forest damage and tree blowdown. High-resolution post-storm aerial photography allowed an inventory of river bank trees blown into the channel along the lower Neches and Sabine Rivers of southeast Texas and southwest Louisiana. Blowdowns directly into the channel averaged 9·3 per kilometer in the lower Neches and 13·4 in the lower Sabine River, but individual reaches 10 to 20 km in length had rates of 20 to 44 blowdowns per kilometer. Though large woody debris (LWD) from Hurricane Rita was widely perceived to reduce the capacity of channels to convey flow, no strong evidence exists of increased flooding or significant reductions in channel conveyance capacity due to LWD from the storm. The Rita blowdown inventory also allowed an assessment of whether similar blowdown events could account for major logjams and rafts on Red, Atchafalaya, and Colorado Rivers on the Gulf Coast, which blocked navigation from tens to hundreds of kilometers in the 1800s. Results from Hurricane Rita suggest that blowdown into channels alone , not withstanding blowdown elsewhere in the river valleys or along tributaries which could deliver LWD to the river , is sufficient to completely block channels, thus providing a plausible mechanism for initiating such (pre)historic log rafts. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Associations between host migration and the prevalence of a protozoan parasite in natural populations of adult monarch butterflies

ECOLOGICAL ENTOMOLOGY, Issue 2 2000
Sonia M. Altizer
Summary 1. Monarch butterflies Danaus plexippus (L.) (Lepidoptera: Nymphalidae) are susceptible to infection by the obligate protozoan parasite Ophryocystis elektroscirrha (McLaughlin and Myers) (Apicomplexa: Neogregarinida). Because monarchs form resident and migratory populations in different parts of the world, this host,parasite system provides the opportunity to examine how variation in parasite prevalence relates to host movement patterns. 2. Parasite prevalence was evaluated using 14 790 adult monarchs captured between 1968 and 1997. Comparison of three populations in North America indicated that parasite prevalence is associated negatively with host dispersal distances. A continuously breeding, nonmigratory population in southern Florida showed high prevalence (over 70% heavily infected). The western population migrates moderate distances to overwintering sites on the Pacific Coast and has intermediate prevalence (30% heavily infected). The eastern migratory population, which travels the longest distance to Mexican overwintering sites, has exhibited less than 8% infection throughout the past 30 years. 3. Variation in parasite loads within North American migratory populations was investigated to determine whether the prevalence of heavy infection and average parasite loads declined during migration or overwintering. Average parasite loads of summer-breeding adults in western North America decreased with increasing distance from overwintering sites. This suggests that heavily infected monarchs are less likely to remigrate long distances in spring. No differences in the frequency of heavily infected adults were found among eastern or western North American monarchs throughout the overwintering period, however, suggesting that this parasite does not affect overwintering mortality. 4. Changes in the prevalence of monarchs with low parasite loads demonstrate that spore transfer occurs during migration and overwintering, possibly when adult butterflies contact each other as a result of their clustering behaviour. 5. This study of geographical and temporal variation in O. elektroscirrha among populations of D. plexippus demonstrates the potential role of seasonal migration in mediating interactions between hosts and parasites, and suggests several mechanisms through which migratory behaviour may influence parasite prevalence. [source]

Bitou Bush control (after fire) in Bundjalung National Park on the New South Wales North Coast

ECOLOGICAL MANAGEMENT & RESTORATION, Issue 2 2006
Jeff Thomas
Bitou Bush has already invaded extensive coastal dunes in subtropical and temperate eastern Australia. Can it be treated at a large enough scale to make a difference? Results to date of a targeted aerial spraying program (applied after wildfire at Bundjalung National Park) are showing strong recovery of high conservation value dunal vegetation along 35 km of the northern New South Wales coastline. [source]

Site-specific marine water-quality criterion for cyanide

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2000
Kevin V. Brix
Abstract A site-specific marine water,quality criterion for cyanide was developed for Puget Sound, Washington, USA. The U.S. Environmental Protection Agency (U.S. EPA) national cyanide water-quality criterion is driven by toxicity data for the eastern rock crab, Cancer irroratus, a species not resident to the U.S. western coast (West Coast). The reported LC50 for C. irroratus is six times lower than any other marine species tested. Cyanide acute toxicity tests were conducted using first stage zoeae of all four species of Cancer spp. resident to Puget Sound to develop a site-specific criterion for this water body. Testing with Puget Sound Cancer spp. reveals sensitivities 24 times less, on average, than C. irroratus. Recalculation of the Puget Sound water-quality criterion for cyanide, by substituting the new Cancer spp. data for the C. irroratus data, results in water-quality criterion protecting marine life against acute and chronic toxicity of 9.4 and 2.9 ,g/L cyanide, compared to the U.S. EPA national value of 1.0 ,g/L for both acute and chronic toxicity. [source]

THE COMBINED EFFECTS OF RIVERS AND REFUGIA GENERATE EXTREME CRYPTIC FRAGMENTATION WITHIN THE COMMON GROUND SKINK (SCINCELLA LATERALIS)

EVOLUTION, Issue 2 2010
Nathan D. Jackson
Rivers can act as both islands of mesic refugia for terrestrial organisms during times of aridification and barriers to gene flow, though evidence for long-term isolation by rivers is mixed. Understanding the extent to which riverine barrier effects can be heightened for populations trapped in mesic refugia can help explain maintenance and generation of diversity in the face of Pleistocene climate change. Herein, we implement phylogenetic and population genetic approaches to investigate the phylogeographic structure and history of the ground skink, Scincella lateralis, using mtDNA and eight nuclear loci. We then test several predictions of a river,refugia model of diversification. We recover 14 well-resolved mtDNA lineages distributed east,west along the Gulf Coast with a subset of lineages extending northward. In contrast, ncDNA exhibits limited phylogenetic structure or congruence among loci. However, multilocus population structure is broadly congruent with mtDNA patterns and suggests that deep coalescence rather than differential gene flow is responsible for mtDNA,ncDNA discordance. The observed patterns suggest that most lineages originated from population vicariance due to riverine barriers strengthened during the Plio,Pleistocene by a climate-induced coastal distribution. Diversification due to rivers is likely a special case, contingent upon other environmental or biological factors that reinforce riverine barrier effects. [source]

VICARIANCE AND DISPERSAL ACROSS BAJA CALIFORNIA IN DISJUNCT MARINE FISH POPULATIONS

EVOLUTION, Issue 7 2003
Giacomo Bernardi
Abstract., Population disjunctions, as a first step toward complete allopatry, present an interesting situation to study incipient speciation. The geological formation of the Baja California Peninsula currently divides 19 species of fish into disjunct populations that are found on its Pacific Coast and in the northern part of the Gulf of California (also called the Sea of Cortez), but are absent from the Cape (Cabo San Lucas) region. We studied the genetic makeup of disjunct populations for 12 of these 19 fish species. Phylogeographic patterns for the 12 species can be separated into two major classes: a first group (eight species) showed reciprocal monophyly and high genetic divergence between disjunct populations. A second group (four species) displayed what appeared to be panmictic populations. Population structure between Pacific Coast populations, across the Punta Eugenia biogeographic boundary, was also evaluated. While dispersal potential (inferred by pelagic larval duration) was a poor predictor of population structure between Gulf of California and Pacific populations, we found that population genetic subdivision along the Pacific Coast at Punta Eugenia was always positively correlated with differentiation between Pacific and Gulf of California populations. Vicariant events, ongoing gene flow, and ecological characteristics played essential roles in shaping the population structures observed in this study. [source]

Glechoma hederacea (Lamiaceae) in North America: invasion history and current distribution,

FEDDES REPERTORIUM, Issue 1-2 2004
M. Scholler
Glechoma hederacea L. (Ground-ivy, Lamiaceae), a perennial mat-forming herb, is native to the temperate regions of Eurasia and was introduced elsewhere (South East Asia, New Zealand and North America). Based on data obtained from herbaria, literature, online and other data bases and field studies, we documented the invasion history and current distribution of this plant in North America. At present, the plant is recorded from all but two continental states of the USA and all southern provinces of Canada. There are two main ranges: the larger one covers mainly the eastern part of the U.S.A. and a smaller one stretches along the West Coast. While published records of Glechoma hederacea date from 1814, the oldest specimen is from 1829. During the 19th century the species spread westwards at a rate of approximately 30 km/year. The spread and present range of G. hederacea can only be explained by climatic factors (degree of oceanicity) and considering human activity. Especially long distance propagation of vegetative parts of the plants and the change of the environment that accompanies human settlements may have had a major influence on these processes. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Glechoma hederacea L. (Lamiaceae) in Nordamerika: Invasionsgeschichte und derzeitige Verbreitung Glechoma hederacea (Gewöhnlicher Gundermann; Lamiaceae), eine im temperaten Eurasien beheimatete ausdauernde krautige Pflanze konnte sich als Neophyt in Südostasien, Neuseeland und Nordamerika etablieren. Basierend auf Daten aus der Literatur und Datenbanken, Belegdaten aus Herbarien und Felduntersuchungen werden die Ausbreitungsgeschichte der Art in Nordamerika und ihr gegenwärtiges Areal dokumentiert. Gegenwärtig ist die Art aus allen kanadischen Provinzen und mit Ausnahme von zwei Bundesstaaten auch von allen kontinentalen Bundesstaaten der USA dokumentiert. Es gibt zwei Hauptareale: ein großes, welches einen Großteil der östlichen USA einnimmt und ein kleineres an der Westküste. Der älteste Nachweis von 1814 von Glechoma hederacea stammt aus der Literatur, der älteste Beleg von 1829. Im Laufe des 19. Jahrhunderts breitete sich die Art mit einer Geschwindigkeit von etwa 30 km/Jahr nach Westen aus. Ausbreitungsgeschwindigkeit und das gegenwärtige Areal können nur mit Hilfe klimatischer (Ozeanität) und anthropogener Faktoren erklärt werden. Der Mensch trägt vor allem zur Verbreitung vegetativer Pflanzenteile bei und schafft in Siedlungen günstige Wachstumsbedingungen. [source]

Does MPA mean ,Major Problem for Assessments'?

FISH AND FISHERIES, Issue 4 2006
Considering the consequences of place-based management systems
Abstract Marine protected areas (MPAs) have been increasingly proposed, evaluated and implemented as management tools for achieving both fisheries and conservation objectives in aquatic ecosystems. However, there is a challenge associated with the application of MPAs in marine resource management with respect to the consequences to traditional systems of monitoring and managing fisheries resources. The place-based paradigm of MPAs can complicate the population-based paradigm of most fisheries stock assessments. In this review, we identify the potential complications that could result from both existing and future MPAs to the science and management systems currently in place for meeting conventional fisheries management objectives. The intent is not to evaluate the effects of implementing MPAs on fisheries yields, or even to consider the extent to which MPAs may achieve conservation oriented objectives, but rather to evaluate the consequences of MPA implementation on the ability to monitor and assess fishery resources consistent with existing methods and legislative mandates. Although examples are drawn primarily from groundfish fisheries on the West Coast of the USA, the lessons are broadly applicable to management systems worldwide, particularly those in which there exists the institutional infrastructure for managing resources based on quantitative assessments of resource status and productivity. [source]

Backhousia citriodora F. Muell.,Rediscovery and chemical characterization of the L -citronellal form and aspects of its breeding system

FLAVOUR AND FRAGRANCE JOURNAL, Issue 5 2001
J. C. Doran
Abstract The rare L -citronellal form of Backhousia citriodora F. Muell. was first reported in 1950 but attempts to relocate it were unsuccessful until 1996. The quest to relocate trees of this type has been driven by interest in L -citronellal for perfumery. The common, citral form of the species is already under cultivation for oil production in Australia. This paper reports on the rediscovery of the L -citronellal form, first in 1996 in a year-old provenance/progeny trial of B. citriodora in south-eastern Queensland, and then in a natural population on Queensland's Sunshine Coast in 1998. The three L -citronellal trees in the trial gave foliar oil concentrations (g/100 g dry weight) of 3.2, 2.2 and 1.8, respectively, when sampled in November 1996. The same trees sampled in March 1999 gave pale yellow oils consisting of 85,89% citronellal, 6,9% isopulegol isomers with small quantities of citronellol (approx. 3%) and several other compounds. Data on the physicochemical properties of these oils are given in the paper. Seed from a single mature L -citronellal tree gave progeny of both the L -citronellal and citral form in a ratio of approximately 1 : 1. Propagation material from many more plants of the L -citronellal form needs to be collected and assembled in breeding populations. This would form the basis of a selection and breeding programme, should this chemotype show economic potential. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Modelling approach to analyse the effects of nitrification inhibition on primary production

FUNCTIONAL ECOLOGY, Issue 1 2009
S. Boudsocq
Summary 1Wet tropical savannas have high grass productivity despite the fact that nitrogen is generally limiting for primary production and soil nutrient content is typically very low. Nitrogen recycling, and especially nitrification, is supposed to be a strong determinant of the balance between conservation and loss of nutrients at the ecosystem level. The important primary production observed in wet tropical savannas might be due to a tight nutrient cycling and the fact that some grass species inhibit soil nitrification. 2Using a general theoretical ecosystem model taking both nitrate and ammonium into account, we investigate analytically, using a four,compartment-differential-equation system the general conditions under which nitrification inhibition enhances primary production. We then estimate the quantitative impact of such a mechanism on the dynamics and budget of nitrogen in a well-documented ecosystem, the Lamto savanna (Ivory Coast). This ecosystem is dominated by the grass Hyparrhenia diplandra, which drastically reduces nitrification in the whole savanna except for a small zone. While this small zone supports a lower grass primary production, nitrification is higher, most likely due to the presence of another genotype of H. diplandra, which has no effect on nitrification processes. Ultimately, we test whether differences in nitrification fluxes can alone explain this variation in primary production. 3Model analysis shows that nitrification inhibition enhances primary production only if the recycling efficiency , that is, the fraction of nitrogen passing through a compartment that stays inside the ecosystem , of ammonium is higher than the recycling efficiency of nitrate. This condition probably manifests itself in most soils as ammonium is less mobile than nitrate and is not touched by denitrification. It also depends partially on the relative affinity of plants for ammonium or nitrate. The numerical predictions for this model in the Lamto savanna show that variations in nitrification inhibition capacity may explain observed differences in primary production. 4In conclusion we find that nitrification inhibition is a process which probably enhances ecosystem fertility in a sustainable way, particularly in situations of high nitrate leaching and denitrification fluxes. This mechanism could explain the ecological advantage exhibited by native African grasses over indigenous grasses in South-American pastures. [source]

Threatened archaeological, historic, and cultural resources of the Georgia Coast: Identification, prioritization and management using GIS technology

GEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 3 2010
Michael H. Robinson
Archaeological sites in beach and estuarine environments are continually threatened by diverse natural marine processes. Shoreline erosion, bluff retreat, and sea level rise all present potential for site destruction. Using historic maps, aerial imagery, and field survey methods in a GIS, 21 potentially significant archaeological sites on Georgia barrier islands were selected for determination of site-specific rates of shoreline change using a powerful, new, moving-boundary GIS analysis tool. A prioritized list of sites, based on the order of site loss from erosion, was generated to assist coastal managers in identifying and documenting sites most at risk. From the original selection of 21 sites, 11 sites were eroding, 8 shorelines were stable, and 2 shorelines were accreting. The methodology outlined here produces critical information on archaeological site loss rates and provides a straightforward means of prioritizing sites for detailed documentation. © 2010 Wiley Periodicals, Inc. [source]

Coastal paleogeography and human land use at Tecolote Canyon, southern California, U.S.A.

GEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 2 2004
René L. Vellanoweth
A buried archaeological site at Tecolote Canyon provides an ideal case study for relating past human land use patterns to changes in coastal paleogeography. Postglacial sea level transgression, erosion, and other marine and fluvial processes form the context for examining two deeply buried archaeological components excavated at CA-SBA-72. Archaeological shellfish assemblages provide proxy data for evaluating the evolution of local marine environments. Pismo clams dominate shellfish assemblages dated to 5800 cal yr B.P., suggesting the presence of a broad and sandy, high-energy beach environment. At 5500 cal yr B.P., the almost exclusive use of California mussels by humans signals the development of rocky intertidal habitats. During the late Holocene, estuarine species dominate the marine mollusk assemblages at CA-SBA-72, reflecting the development of local estuarine conditions or trade with nearby Goleta Slough villages. The buried components at Tecolote Canyon appear to have served as temporary camps for shellfish harvesting and processing. While general changes in coastal paleogeography and human subsistence have been reconstructed for the Santa Barbara Coast, high resolution ecological data from Tecolote Canyon suggest that Native peoples also adapted to localized and shorter-term shifts in intertidal habitats, changes not evident in most larger or more disturbed surface sites in the region. Linking these changes with shifts in human land use patterns highlights the interaction between humans and a dynamic coastal system. These data demonstrate the importance of small, buried sites in understanding the full spectrum of human subsistence and settlement choices and local environmental change. © 2004 Wiley Periodicals, Inc. [source]

THE NON-PENNSYLVANIA TOWN: DIFFUSION OF URBAN PLAN FORMS IN THE AMERICAN WEST,

GEOGRAPHICAL REVIEW, Issue 2 2006
MICHAEL P. CONZEN
ABSTRACT. Wilbur Zelinsky's classic 1977 account of the Pennsylvania town as a cultural place type,the urban component of the nationally influential Pennsylvanian culture region,acknowledged that it was not exported intact across the successive western frontiers of the United States. But, aside from Edward Price's specialized study of courthouse squares, we know little that is systematic about how town-planning ideas diffused across the continent. This investigation offers evidence from the Willamette Valley in Oregon of the eventual variety and geographical distribution of town-platting conventions that developed in this Pacific Coast "destination' setting and the possible provenance in the Ohio Valley of certain early Oregonian town-plan features. The evidence raises questions about the resilience of town-planning conventions in light of the distance carried, cultural time lags, and changing ideas about best practice and local suitability. [source]

Climate,growth relationships of tropical tree species in West Africa and their potential for climate reconstruction

GLOBAL CHANGE BIOLOGY, Issue 7 2006
JOCHEN SCHÖNGART
Abstract Most tropical regions are facing historical difficulties of generating biologically reconstructed long-term climate records. Dendrochronology (tree-ring studies) is a powerful tool to develop high-resolution and exactly dated proxies for climate reconstruction. Owing to the seasonal variation in rainfall we expected the formation of annual tree rings in the wood of tropical West African tree species. In the central-western part of Benin (upper Ouémé catchment, UOC) and in northeastern Ivory Coast (Comoé National Park, CNP) we investigated the relationship between climate (precipitation, sea surface temperature (SST)) and tree rings and show their potential for climate reconstruction. Wood samples of almost 200 trees belonging to six species in the UOC and CNP served to develop climate-sensitive ring-width chronologies using standard dendrochronological techniques. The relationship between local precipitation, monthly SST anomalies in the Gulf of Guinea, El Niño- Southern Oscillation (ENSO) and ring-width indices was performed by simple regression analyses, two sample tests and cross-spectral analysis. A low-pass filter was used to highlight the decadal variability in rainfall of the UOC site. All tree species showed significant relationships with annual precipitation proving the existence of annual tree rings. ENSO signals could not be detected in the ring-width patterns. For legume tree species at the UOC site significant relationships could be found between SST anomalies in the Gulf of Guinea indicating correlations at periods of 5.1,4.1 and 2.3 years. Our findings accurately show the relationship between tree growth, local precipitation and SST anomalies in the Gulf of Guinea possibly associated with worldwide SST patterns. A master chronology enabled the reconstruction of the annual precipitation in the UOC to the year 1840. Time series analysis suggest increasing arid conditions during the last 160 years which may have large impacts on the hydrological cycles and consequently on the ecosystem dynamics and the development of socio-economic cultures and sectors in the Guinea-Congolian/Sudanian region. [source]

Hydrogeological and Hydrogeochemical Studies for Salt Water Intrusion on the South Coast of Laizhou Bay, China

GROUND WATER, Issue 1 2000
Yuqun Xue
Sea water intrusion has occurred on the east and southeast coasts of Laizhou Bay, China, since the 1970s (Wu et al. 1993). In 1981, on the adjacent south coast, the intrusion of salt water originating from brine was observed. In this area, the salt water intrusion was caused by the excessive pumping of fresh water in aquifers. Moreover, the simultaneous pumping of fresh water and salt water/brine formed a complicated ground water flow field. The data obtained from observation wells were used to analyze the origin of the salt water and brine, and the genesis of the bicarbonate/sodium water zone. All data suggest that the brine originated from ancient sea water, and that the bicarbonate/sodium water was formed by cation exchange. The variations of chemical compositions along representative flowpaths and the relationships between such variations and salt water intrusion were also discussed. [source]

Understanding Sierra Leone in Colonial West Africa: A Synoptic Socio-Political History

HISTORY COMPASS (ELECTRONIC), Issue 3 2009
Joseph Bangura
Sierra Leone played a pivotal role in the success of the British colonial project in West Africa in the 19th century. In 1866, it served as the administrative headquarters for the colonies of Lagos, the Gold Coast now Ghana and Bathurst Gambia. Professionals, clergymen, and intellectuals from Sierra Leone, particularly Creoles, served as civil servants, engineers, and medical doctors in Nigeria, Ghana, and the Gambia in the 18th and 19th centuries. Sierra Leone also educated one of the first crops of Western-educated elites in West Africa. In short, despite experiencing a devastating civil war, evidently Sierra Leone is gradually regaining its quintessential role as one of the oldest, peaceful, and democratic states in West Africa. [source]

Hurricane Katrina and the Burdens of History

HISTORY COMPASS (ELECTRONIC), Issue 2 2006
Adam Rothman
Almost three months after Hurricane Katrina made landfall on the Gulf Coast, a New York Times editorial mourns, "We are about to lose New Orleans." The city remains crippled. Whole neighborhoods have been reduced to rubble. The federal, state, and local governments dither. Basic services are yet to be fully restored. Only a fraction of its residents have returned, and many never will. By the last count, more than a thousand New Orleanians died in the disaster. The sad truth is that we have already lost New Orleans. Whatever replaces it will not be the same. The city is history.1 [source]

Distribution of genetic variation among chromosomal forms of Anopheles gambiae s.s.: introgressive hybridization, adaptive inversions, or recent reproductive isolation?

INSECT MOLECULAR BIOLOGY, Issue 1 2001
W. C. Black IV
Abstract A series of four papers in this issue explores the reproductive status of the five chromosomal forms of An. gambiae s.s. using molecular techniques to examine the variation among twelve different genes located throughout the An. gambiae s.s. genome. Results of these and previous studies are consistent with a hypothesis of at least partial barriers to gene flow between some chromosomal forms in the Ivory Coast and other West African countries to the north and west, but introgression between S and M types in Benin and countries to the east. Collectively, these studies indicate the need for a broader geographical sampling of An. gambiae s.s., increased research on mechanisms of prezygotic reproductive isolation and field-based studies of survival and fecundity in hybrids to test for postzygotic reproductive isolation. [source]

Features of cross-Pacific climate shown in the variability of China and US precipitation

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 13 2005
Q. Li
Abstract In this study, we have analyzed the climate features of China and the United States with a focus on the differences, similarities, connectivity, and predictability of precipitation and the relationships between precipitation and large-scale patterns of natural variability. China precipitation is characterized by large seasonality, with a maximum in summer and a minimum in winter. The seasonality of precipitation shows an increasing linear tendency in northwest China, with a change of about 20% from 1901 to 1998. A relatively weaker increasing tendency also appears in the Big Bend of Yellow River (BBYR) and the Tibetan Plateau, while southwest China experiences a decreasing tendency. Furthermore, the seasonality in the BBYR shows particularly significant interdecadal variability, while that of southern and eastern China has decreased slightly in the recent decades. Compared to China, the United States as a whole has less precipitation in summer but more precipitation in other seasons. Here, the seasonality of precipitation is only about 24% of that in China. The annual mean precipitation is 64.1 mm per month in the United States, compared to 54.6 mm per month in China. The seasonality of precipitation exhibits a decreasing tendency in the southeast, Pacific Northwest, and Gulf Coast and an increasing tendency in the Great Lakes. The seasonality in the Great Plains exhibits large interdecadal variability. The long-term variations of precipitation are highly seasonally dependent. In summer, a decreasing trend is observed in north China and an increasing trend is found in eastern-central China. However, these trends are almost opposite in spring. In addition, the fall precipitation decreases with time nearly everywhere in China except for the middle and lower reaches of the Yangtze River Valley. Results also indicate that the El Niño/Southern Oscillation (ENSO), the Arctic Oscillation (AO), the North Atlantic Oscillation (NAO), the Pacific Decadal Oscillation (PDO), and the North Pacific (NP) fluctuation affect strongly the variations of China and US precipitation. Although these influences vary with regions and seasons, we in particular emphasize the importance of AO and NAO for China precipitation and NP and PDO for US precipitation. In fall, ENSO and PDO are the two phenomena that influence predominantly precipitation variability in both China and the United States We also identify the common phenomena that influence China and US regional precipitation and provide a better understanding of the physical mechanism for precipitation variability through the associated changes in atmospheric and oceanic conditions. Furthermore, we develop a linear regression model, based on multiple regression method by combining the regionally and seasonally varying impacts, to increase the skill of precipitation prediction. Copyright © 2005 Royal Meteorological Society [source]