Soybean Aphid Predators in Québec and the Suitability of Aphis glycines as Prey for Three Coccinellidae

Since its invasion of North America in 2000, the soybean aphid, Aphis glycines Matsumura (Homoptera: Aphididae) has notably changed the arthropod community of the soybean agroecosystem. The objectives of this study were to characterize the foliar predatory fauna associated with A. glycines in commercial soybean fields in Québec, Canada, and to evaluate the suitability of A. glycines as prey for three coccinellid species: Harmonia axyridis Pallas, Propylea quatuordecimpunctata L. and Coleomegilla maculata lengi Timberlake (Coleoptera: Coccinellidae). Field surveys showed that several predators responded rapidly to expanding and increasing populations of the soybean aphid. Coccinellidae were the most important aphidophagous predators observed in 2002 (58.6%) and 2003 (44.8%), with mainly four native and naturalized species co-occurring with the soybean aphid throughout the growing season. Measurement of fitness parameters under laboratory conditions (survival, development time, longevity, fecundity) indicated that A. glycines is an excellent prey for the development and reproduction of all three of the coccinellid species studied. The intrinsic rate of natural increase (r_m) was highest for H. axyridis (0.238 d⁻¹), intermediate for P. quatuordecimpunctata (0.215 d⁻¹) and lowest for C. maculata (0.134 d⁻¹).     

Predatory Potential of Freshwater Animals on an Invasive Agricultural Pest, the Apple Snail Pomacea canaliculata (Gastropoda: Ampullariidae), in Southern Japan

The apple snail Pomacea canaliculata is an invasive species and a serious pest of rice in many Asian countries. We studied predatory activities of various animals living in Japanese freshwater habitats, by keeping each individual of a potential predator species with 36 snails of various sizes for three days in the aquarium. Forty-six species were tested, and 26 in eight classes fed on small snails. A species of leech, crabs, the common carp, turtles, the mallard duck and the Norway rat attacked even adult snails of 20–30 mm in shell height. These findings will be helpful in identifying effective predators for biological control of the pest snail. In addition, most of the animals attacking snails are reported to be common in rivers or ponds, but few live in modernized paddy fields having little connections with natural water systems. This may be a reason why this snail maintains large populations in paddy fields but not in other freshwater habitats.     

内皮祖细胞及其在组织工程中的应用

目前,组织工程化血管的构建和工程化组织器官的血管化因内皮种子细胞的扩增能力不足和生物活性不强而受到限制。内皮祖细胞(EPC)是内皮细胞的前体细胞。出生后,EPC主要存在于骨髓,可向外周血液缓慢释放,参与机体缺血组织的血管重建和损伤血管的重新内皮化。现对EPC的来源、分布、表型特征、动员、分化、归巢、分离、培养与鉴定等生物学特性和EPC在组织工程中的应用进行了全面的综述,并指出目前存在的问题和研究方向。     

Endogenous Signaling Complexity in Neuropeptides- Leucine- and Methionine-Enkephalin

1. In addition to his many fine contributions in furthering our understanding of the neurochemical action of ecosanoids, catchelomines, steroids, anandamines, cannabinoids, endorphins, and the many modifications made to these neural factors, twenty years ago Julius Axelrod published a noteworthy paper concerning the nature of neuropeptides and their potential for multiple neurophysiological effects (Redgate et al., 1986).2. In that report, Axelrod and coworkers described the neurological actions of the then recently discovered leucine- and methionine-enkephalins, and their biological functions which were novel, atypical, and in possession of neurological effects that were significantly “much more than additive.”3. In this short communication I would like to expand on this observation concerning the “additive effects” contained within the amino acid sequence of the atypical neurotransmitter peptides leucine- and methonine-enkephalin.     

Coming to Understanding: Developing Conservation through Incremental Learning in the Pacific Northwest

Lessons in conservation are often seen as resulting from cycles of overexploitation and subsequent depletion of resources, followed by catastrophic consequences of shortage and starvation, and finally, development of various strategies, including privatization of the commons, to conserve remaining resource stocks. While such scenarios have undoubtedly occurred on many occasions, we suggest that they are not the only means by which people develop conservation practices and concepts. There are other pathways leading to ecological understanding and conservation, which act at a range of scales and levels of complexity. These include: lessons from the past and from other places, perpetuated and strengthened through oral history and discourse; lessons from animals, learned through observation of migration and population cycles, predator effects, and social dynamics; monitoring resources and human effects on resources (positive and negative), building on experiences and expectations; observing changes in ecosystem cycles and natural disturbance events; trial and error experimentation and incremental modification of habitats and populations. Humans, we believe, are capable of building a sophisticated conservation ethic that transcends individual species and resources. A combination of conservation knowledge, practices, and beliefs can lead to increasingly greater sophistication of ecological understanding and the continued encoding of such knowledge in social institutions and worldview.     

The biogeography of naturalization in alien plants

Aim  This paper reviews the main geographical determinants of naturalization in plants.
Location  Global.
Methods  Comparative studies of large data sets of alien floras are the main source of information on global patterns of naturalization.
Results  Temperate mainland regions are more invaded than tropical mainland regions but there seems to be no difference in invasibility of temperate and tropical islands. Islands are more invaded than the mainland. The number of naturalized species in temperate regions decreases with latitude and their geographical ranges increase with latitude. The number of naturalized species on islands increases with temperature. Naturalized species contribute to floristic homogenization, but the phenomenon is scale-dependent.
Main conclusions  Some robust patterns are evident from currently available data, but further research is needed on several aspects to advance our understanding of the biogeography of naturalization of alien plants. For example, measures of propagule pressure are needed to determine the invasibility of communities/ecosystems/regions. The patterns discussed in this paper are derived largely from numbers and proportions of naturalized species, and little is known about the proportion of introduced species that become naturalized. Further insights on naturalization rates, i.e. the proportion of aliens that successfully naturalize within regions, and on geographical and other determinants of its variation would provide us with better understanding of the invasion process. Comparative studies, and resulting generalizations, are almost exclusively based on numbers of species, but alien species differ in their impact on native biodiversity and ecosystem processes.     

Resource-Ratio Theory and the Control of Invasive Plants

There have been relatively few tests of resource-ratio theory in terrestrial systems. Additionally, resources are known to be an important factor determining the success of invasive species. Here I discuss how the study by Newingham and Belnap (pp. 29–40, this issue) tests predictions of resource-ratio theory and how they apply it to questions of invasion by Bromus tectorum in a terrestrial grassland.     

Effect of Plant Species on Persistence of Paecilomyces lilacinus Strain 251 in Soil and on Root Colonization by the Fungus

The effect of 12 plant species on the persistence of Paecilomyces lilacinus strain 251 in soil was investigated. After incorporating formulated conidia into non-sterile soil followed by transplanting different test plants, the population dynamic of the fungus was determined over 100 days. At termination of the experiment, the fungal population in the planted soil was compared to the density of P. lilacinus in the rhizosphere and the percent increase or decrease was calculated for each crop. In addition, the potential of P. lilacinus strain 251 to colonize roots endophytically was investigated. Comparison of the slopes describing the population dynamics of the fungus showed no significant differences between soil without plants and soil from the root zone of the majority of the test plants. Bean was the only plant species consistently exerting a negative effect on the persistence of P. lilacinus strain 251 in the soil. For the first time, P. lilacinus strain 251 was isolated in significant numbers from healthy root tissue of barley plants.     

Long-term Effects of Pre-harvest Burning and Nitrogen and Vinasse Applications on Yield of Sugar Cane and Soil Carbon and Nitrogen Stocks on a Plantation in Pernambuco, N.E. Brazil

Since the 1970s the area under sugarcane in Brazil has increased from 2 million to over 5 million ha (M ha), and it is expected to pass the 7 M ha mark in 2007. More than half of the cane is harvested to produce bioethanol as a fuel for light vehicles. The distilleries produce approximately 13 L of distillery waste (vinasse) for each litre of ethanol produced. In the 1980s there was considerable concern over the long-term effects of the disposal of this material (containing about 1% carbon and high in K) on cane yields if it was applied to the field. At the same time there was a growing movement to abandon the practice of pre-harvest burning and some research was showing that some Brazilian varieties of sugar cane were able to obtain significant contributions of N from plant-associated biological nitrogen fixation (BNF). For these reasons an experiment was installed on a cane plantation in the state of Pernambuco, NE Brazil to investigate the long-term effects of vinasse and N fertiliser additions and the practice of pre-harvest burning on crop and sugar yield, soil fertility parameters, N balance and soil C stocks. The results showed that over a 16-year period, trash conservation (abandonment of burning) increased cane yields by 25% from a mean of 46 to 58 Mg ha⁻¹. Vinasse applications (80 m³ ha⁻¹ crop⁻¹) increased mean cane and sugar yield by 12 to 13% and the application of 80 kg N ha⁻¹ as urea increased cane yields by 9%, but total sugar yield by less than 6% (from 7.0 to 7.4 Mg ha⁻¹ crop⁻¹). The total N balance for the soil/plant system when only the surface 20 cm of the soil was considered was positive in plots where no N fertiliser was added. However, the data indicated that during the 16 years of the study considerable quantities of soil organic matter were accumulated below 20 cm depth such that the N balance considering the soil to 60 cm depth was strongly positive, except where N fertiliser was added. The data indicated that there were considerable BNF inputs to the system, which was consistent with its low response to N fertiliser and low N fertiliser-use-efficiency. There were no significant effects of vinasse or urea addition, or trash conservation on soil C stocks, although the higher yields proportioned by trash conservation had potentially significant benefits for increased mitigation of CO₂ emissions where the main use of the cane was for bioethanol production.     

Optimal movement between patches under incomplete information about the spatial distribution of food items

If the food distribution contains spatial pattern, the food density in a particular patch provides a forager with information about nearby patches. Foragers might use this information to exploit patchily distributed resources profitably. We model the decision on how far to move to the next patch in linear environments with different spatial patterns in the food distribution (clumped, random, and regular) for foragers that differ in their degree of information. An ignorant forager is uninformed and therefore always moves to the nearest patch (be it empty or filled). In contrast, a prescient forager is fully informed and only exploits filled patches, skipping all empty patches. A Bayesian assessor has prior knowledge about the content of patches (i.e. it knows the characteristics of the spatial pattern) and may skip neighbouring patches accordingly by moving to the patch where the highest gain rate is expected. In most clumped and regular distributions there is a benefit of assessment, i.e. Bayesian assessors achieve substantially higher long-term gain rates than ignorant foragers. However, this is not the case in distributions with less strong spatial pattern, despite the fact that there is a large potential benefit from a sophisticated movement rule (i.e. a large penalty of ignorance). Bayesian assessors do also not achieve substantially higher gain rates in environments that are relatively rich or poor in food. These results underline that an incompletely informed forager that is sensitive to spatial pattern should not always respond to existing pattern. Furthermore, we show that an assessing forager can enhance its long-term gain rate in highly clumped and some specific near-regular food distributions, by sampling the environment in slightly larger spatial units.