Rodent handling of Araucaria araucana seeds

In an intermast year of very low seed production, we studied seed handling in an Araucaria araucana (Araucariaceae) forest in Neuquén Province, Argentina. Rodents identified in 844 photographs from automatic cameras removed 589 seeds marked with small embedded magnets. Within 12 days of removal, 460 were recovered using a magnetic field locator; 79% of recoveries were from burrows and caches in litter or soil. Rodents exhibited a diversity of seed‐handling strategies and differed in their potential as dispersal agents. Seed removal was most likely between 15.00 hours and 21.00 hours, but diurnal and nocturnal visits were recorded for all species. Oligoryzomys longicaudatus (Cricetidae) was a seed predator that took 8% of marked seeds and left none whole. Chelemys macronyx (Cricetidae) and Rattus norvegicus (Muridae) removed 25% and 19% of marked seeds respectively. These two species deposited the majority of seeds in groups of 10 or more in burrow larders that were unfavourable seedling establishment sites far from daylight. Abrothrix longipilis (Cricetidae) removed 43% of seeds, scatter‐hoarded the largest percentage of whole seeds (37%), moved some seeds farther than 40 m, and left them in favourable seedling establishment sites near daylight. For all species, the number and proportion of seeds cached whole increased as more seeds were removed. Rodents, especially A. longipilis, may play an important role in regeneration of A. araucana. Seed‐handling strategies and potentially effective dispersal are discussed in terms of masting seed production.     

A diminution in ascorbate oxidase activity affects carbon allocation and improves yield in tomato under water deficit

The regulation of carbon allocation between photosynthetic source leaves and sink tissues in response to stress is an important factor controlling plant yield. Ascorbate oxidase is an apoplastic enzyme, which controls the redox state of the apoplastic ascorbate pool. RNA interference was used to decrease ascorbate oxidase activity in tomato (Solanum lycopersicum L.). Fruit yield was increased in these lines under three conditions where assimilate became limiting for wild‐type plants: when fruit trusses were left unpruned, when leaves were removed or when water supply was limited. Several alterations in the transgenic lines could contribute to the improved yield and favour transport of assimilate from leaves to fruits in the ascorbate oxidase lines. Ascorbate oxidase plants showed increases in stomatal conductance and leaf and fruit sugar content, as well as an altered apoplastic hexose : sucrose ratio. Modifications in gene expression, enzyme activity and the fruit metabolome were coherent with the notion of the ascorbate oxidase RNAi lines showing altered sink strength. Ascorbate oxidase may therefore be a target for strategies aimed at improving water productivity in crop species.     

Phylogeny of thrips (Insecta: Thysanoptera) based on five molecular loci

The order Thysanoptera (Paraneoptera), commonly known as thrips, displays a wide range of behaviours, and includes several pest species. The classification and suggested relationships among these insects remain morphologically based, and have never been evaluated formally with a comprehensive molecular phylogenetic analysis. We tested the monophyly of the suborders, included families and the recognized subfamilies, and investigated their relationships. Phylogenies were reconstructed based upon 5299 bp from five genetic loci: 18S ribosomal DNA, 28S ribosomal DNA, Histone 3, Tubulin‐alpha I and cytochrome oxidase c subunit I. Ninety‐nine thrips species from seven of the nine families, all six subfamilies and 70 genera were sequenced. Maximum parsimony, maximum likelihood and Bayesian analyses all strongly support a monophyletic Tubulifera and Terebrantia. The families Phlaeothripidae, Aeolothripidae, Melanthripidae and Thripidae are recovered as monophyletic. The relationship of Aeolothripidae and Merothripidae to the rest of Terebrantia is equivocal. Molecular data support previous suggestions that Aeolothripidae or Merothripidae could be a sister to the rest of Terebrantia. Four of the six subfamilies are recovered as monophyletic. The two largest subfamilies, Phlaeothripinae and Thripinae, are paraphyletic and require further study to understand their internal relationships.     

Elevated atmospheric CO2: effects on phytochemistry, insect performance and insect-parasitoid interactions

This study was conducted to examine the effects of CO₂-mediated changes in tree chemistry on the performance of the gypsy moth ((Lymantria dispar L.) and the parasitold Cotesia melanoscela (Ratz.). We used carbon-nutrient balance theory to develop hypotheses regarding changes in tree chemistry and the performance of both insects under elevated CO₂. As predicted, levels of foliar nitrogen declined and concentrations of carbon-based compounds (e.g. starch and phenolics) increased under elevated CO₂. Gypsy moth performance (e.g. growth, development) was altered by CO₂-mediated changes in foliar chemistry, but the magnitude was small and varied across tree species. Larvae feeding on high CO₂ aspen exhibited the largest reduction in performance, relative to larvae feeding on birch, oak, or maple. Parasitism by C. melanoscela significantly prolonged gypsy moth development and reduced growth rates. Overall, the effect of parasitism on gypsy moth performance did not differ between CO₂ treatments. Altered gypsy moth performance on high CO₂ foliage in turn affected parasitoid performance, but the response was variable: parasitoid mortality increased and adult female size declined slightly under high CO₂, while development time and adult male size were unaffected. Our results suggest that CO₂-induced changes in plant chemistry were buffered to the extent that effects on third trophic level interactions were weak to non-existent for the system examined in this study.     

Climate warming increases soil erosion,carbon and nitrogen loss with biofuel feedstock harvest in tallgrass prairie

Anthropogenic soil erosion severely affects land ecosystems by reducing plant productivity and stimulating horizontal carbon and nitrogen movement at the surface. Climate warming may accelerate soil erosion by altering soil temperature, moisture, and vegetation coverage. However, no experiments have been carried out to quantify soil erosion with warming. In a long‐term field experiment, we explored how annual clipping for biofuel feedstock production and warming caused soil erosion and accompanying carbon and nitrogen losses in tallgrass prairie in Oklahoma, USA. We measured relative changes in soil surface elevation between clipped and unclipped plots with or without experimental warming. Our results show that average relative erosion depth caused by clipping was 1.65±0.09 and 0.54±0.08 mm yr^?1, respectively, in warmed and control plots from November 21, 1999 to April 21, 2009. The soil erosion rate was 2148±121 g m^?2 yr^?1 in the warmed plots and 693±113 g m^?2 yr^?1 in the control plots. Soil organic carbon was lost at a rate of 69.6±5.6 g m^?2 yr^?1 in the warmed plots and 22.5±2.7 g m^?2 yr^?1 in the control plots. Total nitrogen was lost at a rate of 4.6±0.4 g m^?2 yr^?1 in the warmed plots and 1.4±0.1 g m^?2 yr^?2 in the control plots. The amount of carbon and nitrogen loss caused by clipping is equivalent to or even larger than changes caused by global change factors such as warming and rising atmospheric CO₂ concentration. In addition, soil erosion rates were significantly correlated with clipping‐induced changes in soil moisture. Our results suggest that clipping for biofuel harvest results in significant soil erosion and accompanying losses of soil carbon and nitrogen, which is aggravated by warming.     

Maternal impact on egg development in Lymnaea stagnalis: a growth factor is produced by the albumen gland in the reproductive tract

Summary

In the freshwater snail Lymnaea stagnalis, perivitellin fluid is the main source of nutrition for developing embryos; it contains predominantly galactogen and proteins. The fluid is produced by the albumen gland, a large exocrine organ in the female reproductive tract. To further define the protein products of this gland and provide more information about the maternal contribution to egg development, albumen glands were extracted and the extracts purified by reversed-phase HPLC. One major HPLC peak fraction exhibited neurotrophic activity when bioassayed on identified Lymnaea neurons in vitro; it has been partially sequenced and has the highest degree of sequence identity with epidermal growth factor (EGF). These results demonstrate that a growth factor with neurotrophic activity is produced by the albumen gland, and is packaged along with the eggs to serve a growth-promoting function in the embryo.     

RADULAR PRODUCTION RATES IN TWO SPECIES OF LACUNA TURTON (GASTROPODA: LITTORINIDAE)

The molluscan radula is a dynamic organ, both in terms of itsuse and production. New rows of teeth are constantly producedat the posterior end of the radula, while older, worn teethare shed anteriorly, producing a dynamic equilibrium. We useda cold-shock to mark the radular ribbon and measure tooth rowproduction rates in two gastropod species, Lacuna vincta (Montagu)and L. vanegata Carpenter. We found that the average tooth rowproduction rate at 10–11°C did not differ betweenthese two species, and was 2.94 (SE = 0.002) rows per day forLacuna vincta and 2.97 (SE = 0 002) for L. vanegata Inter-individualvariability in production rate was very low, and was correlatedwith shell length, smaller individuals had slightly higher productionrates. The total length of the radular nbbon varied greatlyamong individuals, ranging from 47 to 94 (2.57 to 5.68 mm) rowsin L vincta and 53 to 99 rows (2.80 to 7.14 mm) in L vanegata,and was only somewhat correlated with the length of the shelLThis great variability will result in large differences amongindividuals in the time it takes to replace the radula totally,from 14.96 to 35.44 days in L vincta and from 17 43 to 39 69days in L. vanegata. (Received 1 September 1995; accepted 20 November 1995)