The evolutionary radiation of modern birds (Neornithes): reconciling molecules, morphology and the fossil record

The pattern, timing and extent of the evolutionary radiation of anatomically modern birds (Neornithes) remains contentious: dramatically different timescales for this major event in vertebrate evolution have been recovered by the 'clock-like' modelling of molecular sequence data and from evidence extracted from the known fossil record. Because current synthesis would lead us to believe that fossil and nonfossil evidence conflict with regard to the neornithine timescale, especially at its base, it is high time that available data are reconciled to determine more exactly the evolutionary radiation of modern birds. In this review we highlight current understanding of the early fossil history of Neornithes in conjunction with available phylogenetic resolution for the major extant clades, as well as recent advancements in genetic methods that have constrained time estimates for major evolutionary divergences. Although the use of molecular approaches for timing the radiation of Neornithes is emphasized, the tenet of this review remains the fossil record of the major neornithine subdivisions and better-preserved taxa. Fossils allowing clear phylogenetic constraint of taxa are central to future work in the production of accurate molecular calibrations of the neornithine evolutionary timescale.  © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society , 2004, 141 , 153–177.     

Efficacy of hot water drenches of Anthurium andraeanum plants against the burrowing nematode Radopholus similis and plant thermotolerance

Hot‐water drench treatments were evaluated for disinfesting roots of potted anthurium Anthurium andraeanum of the burrowing nematode Radopholus similis. A continuous drench of roots and media in pots with 50°C water for 5 to 20 min eliminated or reduced nematode populations to < 1 g^?1 of dry root. A second hot water drench, 2 months after the first drenching, tended to increase the efficacy of the heat treatment. A few survivors persisted in the roots and/or stems of a few plants 2 to 4 months after heat treatment. Non‐treatment of the shoots and possible migration from stem to root tissues are probable causes of nematode survival. Drenching potting media and roots in pot were as effective against R. similis in the roots as hot water dipping bare‐rooted plants. Plant response to hot‐water drenching varied among cultivars, but most exhibited tolerance to the heat treatments. Visual inspection of the plants showed little difference between treated and untreated plants in the heat tolerant cultivars. However, all heat‐treated ‘Marian Seefurth’ plants, especially hot water‐dipped bare‐rooted plants, appeared to suffer some degree of growth reduction as measured by lower root and stem dry weights when compared to untreated plants 3 months after treatment. Conditioning anthurium plants with hot water or hot air prior to hot water drenching did not benefit plant quality when compared to unconditioned, heat‐treated plants.     

Estimating the contribution of carnivorous waterbirds to nutrient loading in freshwater habitats

1. We estimated nitrogen (N) and phosphorus (P) loading into wetlands by carnivorous waterbirds with alternative physiological models using a food‐intake and an excreta‐production approach. The models were applied for non‐breeding and breeding Dutch inland carnivorous waterbird populations to quantify their contribution to nutrient loading on a landscape scale. 2. Model predictions based on food intake exceeded those based on excretion by 59–62% for N and by 2–36% for P, depending on dietary assumptions. Uncertainty analysis indicated that the intake model was most affected by errors in energy requirement, while the excretion model was dependent on faecal nutrient composition. 3. Per capita loading rate of non‐breeders increased with body mass from 0.3–0.8 g N day^?1 and 0.15 g P day^?1 in little gulls Larus minutus to 4.5–11.5 g N day^?1 and 2.1–3.2 g P day^?1 in great cormorants Phalacrocorax carbo. For breeding birds, the estimated nutrient loading by a family unit over the entire breeding period ranged between 17.6–443.0 g N and 8.6 g P for little tern Sterna albifrons to 619.6–1755.6 g N and 316.2–498.1 g P for great cormorants. 4. We distinguished between external (i.e. importing) and internal (i.e. recycling) nutrient loading by carnivorous waterbirds. For the Netherlands, average external‐loading estimates ranged between 38.1–91.5 tonnes N and 16.7–18.2 tonnes P per year, whilst internal‐loading estimates ranged between 53.1–140.5 tonnes N and 25.2–39.2 tonnes P and per year. The average contribution of breeding birds was estimated to be 17% and 32% for external and internal loading respectively. Most important species were black‐headed gull Larus ridibundus and mew gull Larus canus for external loading, and great cormorant and grey heron Ardea cinerea for internal loading. 5. On a landscape scale, loading by carnivorous waterbirds was of minor importance for freshwater habitats in the Netherlands with 0.26–0.65 kg N ha^?1 a^?1 and 0.12–0.16 kg P ha^?1 a^?1. However, on a local scale, breeding colonies may be responsible for significant P loading.     

Acid Release at Activation and Fertilization of Starfish Oocytes

Fertilization or activation by ionophore A 23187 induces a transient acid release in prophase-blocked and in maturing oocytes of Asterias rubens and Marthasterias glacialis. 1-Methyladenine-induced maturation is not accompanied by acid release. There is no significant difference in the kinetic and amount of acid release related to the nature of activation or the stage of oocytes in each species. The amount of acid released per oocyte volume is smaller than total "fertilization acid" of sea urchin eggs but comparable to its Na-insensitive component. Cortical reaction can be initiated without significant acid release in ammonia treated oocytes. A burst of sodium influx occurs at activation or fertilization of oocytes. Kinetic and amount of Na influx are comparable to acid release. Vitelline membrane elevation is impaired upon activation of oocytes in the absence of extracellular sodium but a significant although smaller release of acid occurs. This suggests that starfish oocytes release acid by a mechanism differing from the Na⁺-H⁺ exchange of sea urchin eggs.     

Potassium limits potential growth of bog vegetation under elevated atmospheric CO2 and N deposition

The free air carbon dioxide enrichment (FACE) and N deposition experiments on four ombrotrophic bogs in Finland, Sweden, the Netherlands and Switzerland, revealed that after three years of treatment: (1) elevated atmospheric CO₂ concentration had no significant effect on the biomass growth of Sphagnum and vascular species; and (2) increased N deposition reduced Sphagnum growth, because it increased the cover of vascular plants and the tall moss Polytrichum strictum, while vascular plant biomass growth was not affected. This paper focuses on water chemistry, plant nutrient content, and litter decomposition rates. Potassium limitation, or low supply of K and P, may have prevented a significant increase of Sphagnum growth under elevated CO₂ and N deposition. Vascular plant growth under elevated CO₂ and N deposition was also limited by K, or by K in combination with P or N (N in CO₂ experiment). Elevated CO₂ and N deposition had no effect on decomposition rates of Sphagnum and vascular plant litter. Aside from a possible effect of N deposition on light competition between species, we expect that elevated atmospheric CO₂ and N deposition concentrations will not affect Sphagnum and vascular plant growth in bogs of north‐west Europe due to K‐, or K in combination with N‐ or P‐, limited growth. For the same reason we expect no effect of elevated CO₂ and N deposition on litter decomposition. Net primary production of raised ombrotrophic bogs that are at or close to steady state, is regulated by input of nutrients through atmospheric deposition. Therefore, we hypothesize that the expected increase of plant growth under elevated CO₂ and N deposition is diminished by current levels of K (and to some extent P and N) in atmospheric deposition.     

Egg size, egg composition and reproductive success in the Oystercatcher Haematopus ostralegus

We investigated the relationship between egg size and composition and their subsequent effects on hatching and fledging success in Eurasian Oystercatchers Haematopus ostralegus on the island of Schiermonnikoog (53̀30'N, 06̀10'E) in the Dutch Wadden Sea between 1986 and 1990. Egg size variation was considerable. The ratio in egg volume of the largest over the smallest egg was more than 1.5 in each of five years. Differences between females accounted for, on average, 61% of the total variance of egg volume. Individual females produced similarly sized eggs from one year to another. Nevertheless, average egg volume per clutch declined by 0.2 cm³ per year as females aged, but this explains little of the observed variation. Female size and food supplementation had no significant effect on egg volume. In absolute terms, large eggs contain more lean dry matter and lipid than small eggs, but the proportion of both constituents decreases with egg size. Consequently, the combustible energy content of eggs increases less than proportionally with egg size. Hatchability averaged 87% and was not correlated with egg volume. Hatchling weight increased with egg size, averaging 65% of fresh egg weight. Chick survival until fledging did not increase with egg volume. Consequently, within the size range observed, large and small eggs are of comparable quality. Since both the costs and benefits of large eggs compared with small eggs seem small at best, we propose that, within the size range encountered in this population, egg size can be considered an evolutionarily neutral trait.     

ULTRASTRUCTURE DES STATOCYSTES CHEZ SCROBICULARIA PLANA ET TELLINA TENUIS (MOLLUSQUES LAMELLIBRANCHES TELLINACEA)

The statocysts of Scrobicularia plana and Tellina tenuis arecomposed of 8 sensory hair-cells separated by giant cells characterizedby a fibrous cytoskeleton. The sensory cells bear few ciliaespecially in S. plana. These cilia are responsible both forrotation of the statolith and for the transduction of stimuli.Their basal bodies bear a side rootlet facing a basal foot anda crown composed of 9 spokes. Such statocysts seem to receiveonly multidirectional stimuli and to allow a less diversifiedbehaviour than the statocysts of Pecten. (Received 16 September 1980;     

Behavioural and community ecology of plants that cry for help

Plants respond to insect herbivory with the production of volatiles that attract carnivorous enemies of the herbivores, a phenomenon called indirect defence or 'plants crying for help'. Plants are under selection to maximize Darwinian fitness, and this can be done by making the right 'decisions' (i.e. by responding to environmental stress in ways that maximize seed production). Plant decisions related to the response to herbivory in terms of the emission of herbivore-induced volatiles include 'to respond or not to respond', 'how fast to respond', 'how to respond' and 'when to stop responding'. In this review, the state-of-the-art of the research field is presented in the context of these decisions that plants face. New questions and directions for future research are identified. To understand the consequences of plant responses in a community context, it is important to expand research from individual interactions to multispecies interactions in a community context. To achieve this, detailed information on underlying mechanisms is essential and first steps on this road have been made. This selective review addresses the ecology of herbivore-induced plant volatiles (HIPVs) by integrating information on mechanisms and ecological functions. New questions are identified as well as challenges for extending current information to community ecology.     

Adapt or disperse: understanding species persistence in a changing world

The majority of studies on environmental change focus on the response of single species and neglect fundamental biotic interactions, such as mutualism, competition, predation, and parasitism, which complicate patterns of species persistence. Under global warming, disruption of community interactions can arise when species differ in their sensitivity to rising temperature, leading to mismatched phenologies and/or dispersal patterns. To study species persistence under global climate change, it is critical to consider the ecology and evolution of multispecies interactions; however, the sheer number of potential interactions makes a full study of all interactions unfeasible. One mechanistic approach to solving the problem of complicated community context to global change is to (i) define strategy groups of species based on life‐history traits, trophic position, or location in the ecosystem, (ii) identify species involved in key interactions within these groups, and (iii) determine from the interactions of these key species which traits to study in order to understand the response to global warming. We review the importance of multispecies interactions looking at two trait categories: thermal sensitivity of metabolic rate and associated life‐history traits and dispersal traits of species. A survey of published literature shows pronounced and consistent differences among trophic groups in thermal sensitivity of life‐history traits and in dispersal distances. Our approach increases the feasibility of unraveling such a large and diverse set of community interactions, with the ultimate goal of improving our understanding of community responses to global warming.     

Woody biomass production during the second rotation of a bio-energy Populus plantation increases in a future high CO2 world

The quickly rising atmospheric carbon dioxide (CO₂)‐levels, justify the need to explore all carbon (C) sequestration possibilities that might mitigate the current CO₂ increase. Here, we report the likely impact of future increases in atmospheric CO₂ on woody biomass production of three poplar species (Populus alba L. clone 2AS‐11, Populus nigra L. clone Jean Pourtet and Populus×euramericana clone I‐214). Trees were growing in a high‐density coppice plantation during the second rotation (i.e., regrowth after coppice; 2002–2004; POPFACE/EUROFACE). Six plots were studied, half of which were continuously fumigated with CO₂ (FACE; free air carbon dioxide enrichment of 550 ppm). Half of each plot was fertilized to study the interaction between CO₂ and nutrient fertilization. At the end of the second rotation, selective above‐ and belowground harvests were performed to estimate the productivity of this bio‐energy plantation. Fertilization did not affect growth of the poplar trees, which was likely because of the high rates of fertilization during the previous agricultural land use. In contrast, elevated CO₂ enhanced biomass production by up to 29%, and this stimulation did not differ between above‐ and belowground parts. The increased initial stump size resulting from elevated CO₂ during the first rotation (1999–2001) could not solely explain the observed final biomass increase. The larger leaf area index after canopy closure and the absence of any major photosynthetic acclimation after 6 years of fumigation caused the sustained CO₂‐induced biomass increase after coppice. These results suggest that, under future CO₂ concentrations, managed poplar coppice systems may exhibit higher potential for C sequestration and, thus, help mitigate climate change when used as a source of C‐neutral energy.