Eutrophication and macroalgal blooms in temperate and tropical coastal waters: nutrient enrichment experiments with Ulva spp.

Receiving coastal waters and estuaries are among the most nutrient‐enriched environments on earth, and one of the symptoms of the resulting eutrophication is the proliferation of opportunistic, fast‐growing marine seaweeds. Here, we used a widespread macroalga often involved in blooms, Ulva spp., to investigate how supply of nitrogen (N) and phosphorus (P), the two main potential growth‐limiting nutrients, influence macroalgal growth in temperate and tropical coastal waters ranging from low‐ to high‐nutrient supplies. We carried out N and P enrichment field experiments on Ulva spp. in seven coastal systems, with one of these systems represented by three different subestuaries, for a total of nine sites. We showed that rate of growth of Ulva spp. was directly correlated to annual dissolved inorganic nitrogen (DIN) concentrations, where growth increased with increasing DIN concentration. Internal N pools of macroalgal fronds were also linked to increased DIN supply, and algal growth rates were tightly coupled to these internal N pools. The increases in DIN appeared to be related to greater inputs of wastewater to these coastal waters as indicated by high δ¹⁵N signatures of the algae as DIN increased. N and P enrichment experiments showed that rate of macroalgal growth was controlled by supply of DIN where ambient DIN concentrations were low, and by P where DIN concentrations were higher, regardless of latitude or geographic setting. These results suggest that understanding the basis for macroalgal blooms, and management of these harmful phenomena, will require information as to nutrient sources, and actions to reduce supply of N and P in coastal waters concerned.     

Changes in aboveground primary production and carbon and nitrogen pools accompanying woody plant encroachment in a temperate savanna

When woody plant abundance increases in grasslands and savannas, a phenomenon widely observed worldwide, there is considerable uncertainty as to whether aboveground net primary productivity (ANPP) and ecosystem carbon (C) and nitrogen (N) pools increase, decrease, or remain the same. We estimated ANPP and C and N pools in aboveground vegetation and surface soils on shallow clay and clay loam soils undergoing encroachment by Prosopis glandulosa in the Southern Great Plains of the United States. Aboveground Prosopis C and N mass increased linearly, and ANPP increased logarithmically, with stand age on clay loam soils; on shallow clays, Prosopis C and N mass and ANPP all increased linearly with stand age. We found no evidence of an asymptote in trajectories of C and N accumulation or ANPP on either soil type even following 68 years of stand development. Production and accumulation rates were lower on shallow clay sites relative to clay loam sites, suggesting strong edaphic control of C and N accumulation associated with woody plant encroachment. Response of herbaceous C mass to Prosopis stand development also differed between soil types. Herbaceous C declined with increasing aboveground Prosopis C on clay loams, but increased with increasing Prosopis C on shallow clays. Total ANPP (Prosopis+herbaceous) of sites with the highest Prosopis basal area were 1.2 × and 4.0 × greater than those with the lowest Prosopis basal area on clay loam and shallow clay soils, respectively. Prosopis ANPP more than offset declines in herbaceous ANPP on clay loams and added to increased herbaceous ANPP on shallow clays. Although aboveground C and N pools increased substantially with Prosopis stand development, we found no corresponding change in surface soil C and N pools (0–10 cm). Overall, our findings indicate that Prosopis stand development significantly increases ecosystem C and N storage/cycling, and the magnitude of these impacts varied with stand age, soil type and functional plant traits     

THE RELATIVE IMPORTANCE OF SHORT- AND LONG-RANGE MOVEMENT OF FLYING APHIDS

1. Aphids are notorious pests of world agriculture. Even so, uncertainty persists as to their capacity for successful aerial dispersal. Evidence exists that, under some conditions, aphids can be wind-borne over long distances, i.e. hundreds of kilometers over desert or sea. It has been argued, in the recent past, that this phenomenon may be part of a strategy to locate fresh host plants in new distant areas. However, the proportion of these insects successfully colonizing new hosts is unknown. 2. Other work using meteorological backtracking has also indicated long-distance movement, but the accuracy of such predictions is dubious unless the altitude of transport is known. Mark-releaseecapture experiments with such small insects have limited potential due to large dilution effects. Static ‘snap-shots’ of demographic population densities, using suction traps, cannot accurately distinguish local aerial density fluxes and population movements from a distance. However, genetic and physiological markers may provide more direct information on population mixing; for example, some allozyme studies have shown a limited level of inter-population gene flow. 3. Under suitable conditions, aphids take off, maintain flight and alight in response to the appropriate visual and olfactory cues. Undoubtedly successful long-distance movement occurs from time to time, but its ecological relevance may have been overstated in the past. It may be selectively disadvantageous for aphids to move from areas containing their host plants. In contrast, it is advantageous for aphids to maximise their chances of survival and reproductive success by landing on suitable plant hosts at the earliest opportunity. 4. The clonal nature of aphids (a single genotype may comprise vast numbers of individuals) means that there may be advantages to phenotypic variation between individuals in the readiness to move. Recent evidence indicates that such a variation exists in the duration of the behavioural migratory phase, the initial period of maiden flight when host-plant cues are ignored and when landing is inhibited. 5. The relative biological importance of short- us. long-distance movements is reassessed with reference to plant virus epidemiology and the spread of new genotypes, e.g. insecticide resistance. It is concluded that the biological relevance of short-distance movements have a much greater impact on population and genotype distribution than long-distance movements, which may be comparatively infrequent.     

Flight behaviour of the bird cherry aphid, Rhopalosiphum padi

Abstract Seasonal winged forms of the bird cherry aphid, Rhopalosiphum padi L., were flown in an automated flight chamber. During their maiden flights, autumn migrants (gynoparae) had a greater initial rate of climb than summer (exules) and spring migrants (emigrants). Autumn migrants, presented with a laterally-positioned green-illuminated target for 2.5 s during each minute of flight, flew for a longer period before responding to the target (110 min) than summer migrants (36 min), while spring migrants responded after an intermediate time (72 min). This period is equivalent to the migratory phase of flight. The summer migrants were maximally responsive to targets illuminated by green monochromatic light (X, 555 nm). Targets illuminated with ultraviolet (γλ 360 nm) were attractive during the migratory and green-responsive phases of flight, but infrared (γλ700 nm) wavelengths were not attractive. The results are discussed with respect to aphid behaviour in the field.     

The identification of an aphid juvenile hormone, and its titre in relation to photoperiod

ABSTRACT. Whole body extractions from larval and adult apterous forms of Megoura viciae , and from adult Aphis fabae , were analysed for the known insect juvenile hormones (JHs) by a gas chromatography-mass spectrometric method. Low levels of JH III were detected in both aphid species, the first identification of a juvenile hormone from an homopteran insect. Although the mean titre in adult M. viciae is higher in long-day than in short-day reared insects (0.12±0.03 v. 0.04±0.01 ng/g), titres were variable and measurements overlapped. The results are discussed in the context of the hormonal control of aphid polymorphism and the question of identity of homopteran and hemipteran JH.     

A Computer Model for Reshaping of Cells in Epithelia Due to In-plane Deformation and Annealing

Although cell reshaping is fundamental to the mechanics of epithelia, technical barriers have prevented the methods of mechanics from being used to investigate it. These barriers have recently been overcome by the cell-based finite element formulation of Chen and Brodland. Here, parameters to describe the fabric of an epithelium in terms of cell shape and orientation and cell edge density are defined. Then, rectangular "patches" of model epithelia having various initial fabric parameters are generated and are either allowed to anneal or are subjected to one of several patterns of in-plane deformation. The simulations show that cell reshaping lags the deformation history, that it is allayed by cell rearrangement and that it causes the epithelium as a whole to exhibit viscoelastic mechanical properties. Equations to describe changes in cell shape due to annealing and in-plane deformation are presented.     

Palaeoenvironment and taphonomy of a Late Jurassic (Late Tithonian) Lagerstätte from central Poland

A rich assemblage of exceptionally preserved marine and terrestrial fossils occurs in fine‐grained limestones in the upper part of the Late Tithonian (Middle Volgian) shallowing upward carbonate sequence in Central Poland. The richest horizon, a deposit known locally as the Corbulomima horizon, is named after the shallow burrowing suspension feeding bivalve Corbulomima obscura, moulds of which occur in densities of up to 500 per square metre on some bedding planes. The fauna in this bed also includes organic and phosphatic remains of a wide range of other creatures including the exuviae of limulids and decapods, disarticulated fish skeletons and rare isolated pterosaur bones and teeth. There are also perfectly preserved dragonfly wings and beetle exoskeletons. The average stable carbon and oxygen isotope values for ostracod shells and fine‐grained sediment from this horizon suggest precipitation of the calcium carbonate from warm seawater of normal marine salinity. The carbonate sediments overlying the fossiliferous horizon have been interpreted as nearshore to shoreface facies. These pass abruptly into coarse reworked intraclastic sediments interpreted as possible tsunami or storm surge over‐wash deposits. The clasts in this deposit have more positive oxygen isotope values than those in the underlying limestone, which may indicate that they were lithified in a slightly more evaporative, perhaps intertidal, setting. The succession terminates with silicified fine‐grained limestones likely to have formed in extremely shallow lagoonal environments. In contrast with the Solnhofen limestones of Lower Tithonian age in south‐central Germany the Corbulomima horizon is interpreted as a transitional deposit formed in a shallow marine setting by rapid burial with elements of both Konservat‐ and Konzentrat‐Lagerstätte preservation. □Konzentrat and Konservat‐Lagerstätte, Taphonomy, Palaeoenvironment, Paleogeography, Late Jurassic, Poland.     

Opportunistic pollinator shifts among sexually deceptive orchids indicated by a phylogeny of pollinating and non-pollinating thynnine wasps (Tiphiidae)

The thynnine wasp genus Neozeleboria Rohwer is the main pollinating group of the sexually deceptive Australian orchid genus, Chiloglottis R.Br. In a highly specialized interaction, Chiloglottis species attract males from a single or very few Neozeleboria species through the chemical mimicry of the female wasp's sex pheromone. An earlier study examining the historical association among Chiloglottis and Neozeleboria using DNA sequence data found matching phylogenetic patterns suggestive of cospeciation between orchids and pollinators. However, patterns of constraint in Neozeleboria emergence phenology and sex pheromones suggested that the close association among orchid and wasp clades may be due to pollinator switching among closely related wasp taxa that have similar traits. In this study, we further examine the association by incorporating a morphological phylogenetic analysis of non‐pollinating as well as pollinating Neozeleboria. The morphological analysis is then compared with DNA sequence data from one nuclear and one mitochondrial gene for an increased sample of outgroup genera. The combined molecular data set finds a monophyletic Neozeleboria, although support for this was not strong in the individual data sets. A high congruence between molecular and morphological analyses was found among higher groupings of Neozeleboria. Neozeleboria species that pollinate Chiloglottis species are not found as a monophyletic group but, rather, are scattered throughout a phylogeny comprising pollinators and non‐pollinators. Under the cospeciation model, the presence of related Neozeleboria non‐pollinators carries the unlikely implication that the association between plant and pollinator has been repeatedly lost. Instead, we favour the alternative ‘preferential pollinator switching’ model that accounts for the specialization among orchid and wasp lineages in terms of similarities in traits among related Neozeleboria. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 86 , 381–395.     

Crafts, Capitalism, and Women: The Potters of La Chamba, Colombia.

Crafts, Capitalism, and Women: The Potters of La Chamba, Colombia. Ronald J. Duncan. Gainesville: University Press of Florida, 2000. 253 pp.     

Quantifying rotifer species richness in temperate lakes

1. Biodiversity assessments of lakes depend on the ability to identify the complement of species present, although the degree of sampling required is often uncertain. We utilise long‐term data to predict rotifer species richness in three habitats in three Polish lakes using rarefaction sampling methods. 2. Richness in littoral and psammon habitats did not saturate, even with up to 130 samples. Highest richness was observed in psammon habitat (119 species) in Lake Mikolajskie, followed by littoral habitat in Lakes ?uknajno (114 species) and Kuc (110 species). Littoral habitats in Lakes ?uknajno (56%) and Kuc (51%) had the most species not shared with other habitats in the same lake. 3. Species richness (Chao2) estimates ranged between 44 for pelagic and 135 for psammon habitat in Lake Mikolajskie, to 100 for psammon and 137 for littoral habitat in Lake Kuc, and 65 for pelagic and 162 for littoral habitat in Lake ?uknajno. Whole lake estimates were 167, 205 and 171 species, respectively, for these lakes, higher than the 150 to 160 species predicted by Dumont and Segers (Hydrobiologia, 1996, 341 , 125). 4. Using standardised sampling, richness was significantly higher in littoral than either pelagic or psammon habitats. Contrasts of standardised rarefaction curves revealed that richness in Lakes Kuc and Mikolajskie was described as well by littoral‐only or psammon‐only samples, respectively, as by those randomly drawn from across all habitats in the lake. 5. Species richness estimates for Lake Mikolajskie were highest in summer, followed by autumn and spring. Interannual estimates differed by up to 427%, nearly an order of magnitude greater than maximal seasonal variation of 70%. 6. Results indicate that much higher sampling intensity is required to establish species richness than is presently carried out in most lakes. Because many species can be detected only with very intensive sampling, conservation programmes must consider sampling intensity when designing studies.