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Social-economic factors are considered as the key to understand processes contributing to biological invasions. However, there has been few quantified, statistical evidence on the relationship between economic development and biological invasion on a worldwide scale. Herein, using principal factor analysis, we investigated the relationship between biological invasion and economic development together with biodiversity for 91 economies throughout the world. Our result indicates that the prevalence of invasive species in the economies can be well predicted by economic factors (R(2) = 0.733). The impact of economic factors on the occurrence of invasive species for low, lower-middle, upper-middle and high income economies are 0%, 34.3%, 46.3% and 80.8% respectively. Greenhouse gas emissions (CO(2), Nitrous oxide, Methane and Other greenhouse gases) and also biodiversity have positive relationships with the global occurrence of invasive species in the economies on the global scale. The major social-economic factors that are correlated to biological invasions are different for various economies, and therefore the strategies for biological invasion prevention and control should be different.

Increasing levels of global trade and intercontinental travel have been cited as the major causes of biological invasion. However, indirect factors such as economic development that affect the intensity of invasion have not been quantitatively explored. Herein, using principal factor analysis, we investigated the relationship between biological invasion and economic development together with climatic information for China from the 1970s to present. We demonstrate that the increase in biological invasion is coincident with the rapid economic development that has occurred in China over the past three decades. The results indicate that the geographic prevalence of invasive species varies substantially on the provincial scale, but can be surprisingly well predicted using the combination of economic development (R(2) = 0.378) and climatic factors (R(2) = 0.347). Economic factors are proven to be at least equal to if not more determinant of the occurrence of invasive species than climatic factors. International travel and trade are shown to have played a less significant role in accounting for the intensity of biological invasion in China. Our results demonstrate that more attention should be paid to economic factors to improve the understanding, prediction and management of biological invasions.

This is the first time that the soil arthropod Community composition along a high-altitude gradient (3,837, 4,105, and 5,050 m a.s.l.) has been investigated in eastern Tibet, China. Five soil samples of 50 cm² were taken from each site and extracted for 7 days in Berlese/Tullgren funnels without heating. Acari was the dominant group of arthropods at all three elevations (79%, 53%, and 54,%, respectively, from the lower site to the upper site). Prostigmata and Oribatida were more abundant than Mesostigmata and Astigmata at all three elevations. Mesostigmata and Oribatida were most abundant at the upper elevation (about 8,300 and 29,000 individuals/m², respectively). Prostigmata and Astigmata were most abundant at the lower elevation (about 170,000 and 20,000 individuals/m², respectively). Collembola was most abundant at the middle elevation (about 68,000 individuals/m²). The insect taxa were most abundant at the lower elevation. Diptera larvae, Protura, and Homoptera were the most abundant taxa along the elevation gradient, while Hemiptera, Thysanoptera, and Protura occurred only at the lower elevation. A multivariate redundancy analysis (RDA) shows that 64% of the variance can be explained by altitude. A change in dominant mite taxa along the elevation gradient could be seen. From the lower to upper sites, the dominant taxa changed from Prostigmata to Prostigmata and Oribatida, and then to Oribatida. About 33 genera in 24 families of oribatid mites were found. The numbers of genera from the lower, middle, and upper elevation were 14, 20, and 19, respectively. [ABSTRACT FROM AUTHOR]

We analyzed genetic differentiation within metapopulations of two species of checkerspot butterfly, Euphydryas aurinia and Melitaea phoebe, in China. To generate genetic information, we used a new molecular technique, DALP — direct amplified length polymorphism. AMOVA results showed that most of the variation occurred among individuals within local populations of both E. aurinia and M. phoebe. However, while there was differentiation among local population in E. aurinia (P < 0.001), there was no subdivision in metapopulation of M. phoebe (P = 0.210). This is consistent with the behavior of M. phoebe adults being more dispersive than E. aurinia. Within the M. phoebe metapopulation, three neighboring patches were always occupied during the observation period (1998-2000). In addition, the number of individuals in these three populations accounted for the majority of M. phoebe larvae, and hence we conclude that the M. phoebe metapopulation might exist as a source-sink metapopulation. On the other hand, the E. aurinia metapopulation is an example of a classical metapopulation. Therefore, the conservation management of these two species should reflect these differences. [ABSTRACT FROM AUTHOR]

Host-plant resistance and biological control are considered to be cornerstones of integrated pest management programs, but there are few studies that elucidate the intricate relationships among host plant, phytophagous insect and natural enemies. Our knowledge of interactions in systems that include three or more trophic levels is limited, yet the need for such knowledge is great. First, for understanding how selection forces shape these relationships, and secondly, for knowing how we can manipulate the systems to our benefit. Two aspects related to studies of tritrophic interactions deserve special attention for those working on biological control: (i) the incorrect assumption that host-plant resistance always positively contributes to the suppressive effect of natural enemies, and (ii) the correct assumption that plants can be selected that promote the effectiveness of natural enemies. Examples are presented to illustrate the first point. A study of the relationships among cucumber, greenhouse whitefly [ Trialeurodes vaporariorum (Westwood)] and the parasitoid Encarsia formosa Gahan illustrates the second point-selection of less-hairy plants leads to the finding and killing of more hosts per unit of time by the parasitoid, and thus to improved biological control. [ABSTRACT FROM AUTHOR]

Improvements of the PPP model (X u 1987) is made to incorporate the effect of temperature and release ratio on host feeding, parasitism and super-parasitism. The behaviour of the model system is qualitatively the same as the original PPP model. However, the actual population interactions and developments of the two insect populations under different release methods can be visualized and discussed in detail. The control of whiteflies by using different methods of Encarsia formosa introduction (i.e., the Dutch method, the 'Pest in first' method and the 'Banker plant system' method) is investigated by case studies. Under 22 °C, all the three methods can effectively suppress the whitefly populations. However, the Dutch method and the 'Banker plant system' method can suppress the whiteflies to much lower densities, but the 'Pest in first' method can have more resistance to new whitefly immigrations. Zusammenfassung Verbesserung des Pflanze-Schädling-Parasitoid-Modells und seine Anwendung auf die Beziehung zwischen der Weißen Fliege und Encarsia formosa Gahan (Hym., Aphelinidae) unter verschiedenen Freisetzungsbedingungen Die Verbesserungen des Pflanze-Schädling-Parasitoid-Modells (X u 1987) wurden durchgeführt, um den Temperatureffekt und die Freisetzungsrate auf den Wirtsfraß, die Parasitierung und die Super-parasitierung mit einzubeziehen. Qualitativ entspricht das Modellsystem dem Originalmodell. Jedoch können die jeweiligen Interaktionen zwischen den Populationen und die Entwicklung der beiden Insektenpopulationen unter verschiedenen Freisetzungsbedingungen detailliert aufgezeichnet und diskutiert werden. Die Bekämpfung der Weißen Fliege mit verschiedenen Einbringungsmethoden von Encarsia formosa wird anhand von Fallstudien untersucht. Bei einer konstanten Temperatur von 22 °C wird bei allen drei Methoden eine wirkungsvolle Herabsetzung der Population der Weißen Fliege erzielt. Mit der 'holländischen Methode' und der 'Banker plant system'-Methode kann die Weiße Fliege zwar auf ein niedrigeres Niveau gebracht werden, aber die 'Pest in first'-Methode erweist sich offensichtlich als wirksamer gegenüber Neuzuwanderungen des Schädlings. [ABSTRACT FROM AUTHOR]

Influence of greenhouse whiteflies ( Trialeurodes vaporariorum Westwood) on cucumber plants is approached as a case study. Pest abundance is expressed as BD, the total integrated area below the population biomass curve (to incorporate age structure) against time. BD is tested for correlation with 5 plant physiological indices, which were also tested for correlation against yield and quality of the cucumbers. Based on these results, the damage threshold (DT) is estimated as BD = 54917 mg. days of pest biomass. The injury threshold (IT) is calculated as Ph (integrated photosynthetic rate, the most sensitive factor relating BD and yield) = 144.06 (mg. dm-2.h-1) × days, a decrease to 81.20% of the photosynthetic rate under control (no pest infestations). Through computer simulations of insect population dynamics, the influence of temperature, initial population density and age structure is approached. The relationship between plant intrinsic physiological characteristics and plant external features (growth indices) under pest infestations is also investigated. Zusammenfassung Funktionale Beziehungen zwischen Schädlingszahl, Pflanzenphysiologie und Ertrag am Beispiel der Weißen Gewächshausfliege, Trialeurodes vaporariorum Westw. (Hom., Aleyrodidae) Eine Annäherung an die Befalls- und Schadensgrenze Es wurde der Einfluß von T. vaporariorum auf Gewächshausgurken als Fallstudie untersucht. Die Schädlingsdichte wird als BD bezeichnet und bildet das gesamte integrierte Areal unter der gegen die Zeit aufgetragenen Populationsmasse-Kurve. BD wurde in Beziehung zu 5 pflanzenphysiologischen Parametern und zugleich zum Ertrag und zur Qualität der Gurken gesetzt. Auf der Grundlage der Ergebnisse wurde die Schadensgrenze (DT) als BD = 54 917 mg-Tage der Schädlingsbiomasse bestimmt. Die Befallsgrenze (IT) wird als Ph (integrierte Photosynthese-Rate als sensitivster Faktor in Beziehung zu BD und zum Ertrag) = 144.06 mg × dm-2 × h-1. Tage kalkuliert, was eine Abnahme auf 81,2% der bei Kontrolle (ohne Schädlingsbefall) vorhandenen Photosynthese bedeutet. Mittels Computersimulation für Insekten-Populationsdynamik wurde der Einfluß von Temperatur, Initialdichte und Altersstruktur bewertet. Die Beziehungen zwischen den inneren pflanzenphysiologischen und den äußeren Wachstumsparametern während des Schädlingsbefalls werden ebenfalls erörtert. [ABSTRACT FROM AUTHOR]

During feeding-site selection on a tomato plant, adult greenhouse whiteflies, Trialeurodes vaporariorum, do not distinguish between leaves of different age from a distance. Selection occurs after landing on the leaf, and a strong preference for young leaves is shown. Transferring a whitefly from a young leaf to an old leaf or vice versa leads to significant changes in behaviour: on the young leaf more time is spent probing (including feeding) and less time walking. Rejection of an old leaf occurs sooner if an insect has previous experience on a young leaf: inexperienced females depart from the leaf after on an average 6 probes of 3 min each; experienced females leave on an average after 3 probes of 2 min each. Young leaves have a higher content of soluble as well as protein nitrogen, compared with old leaves, so the preference may have adaptive value. Possible mechanisms which might enable feeding-site selection in the greenhouse whitefly are discussed. This includes the nature of the stimuli involved (physical, chemical) as well as the part of the leaf where those stimuli originate from (phloem contents, mesophyl, leaf surface). Zusammenfassung Zur Parasit-Wirt-Beziehung zwischen Encarsia formosa Gahan (Hymenoptera, Aphelinidae) und Trialeurodes vaporariorum (Westwood) (Homoptera, Aleyrodidae). XIX. Nahrungsplatz-Wahl von adulten Weißen Fliegen Bei der Auswahl des Nahrungsplatzes auf einer Tomatenpflanze macht Trialeurodes vaporariorum aus der Entfernung keinen Unterschied zwischen Blättern verschiedenen Alters. Die Auswahl findet erst nach der Landung auf einem Blatt statt, wobei die jungen Blätter stark bevorzugt werden. Überträgt man eine Weiße Fliege von einem jungen Blatt auf ein altes oder umgekehrt, führt das zu bedeutenden Veränderungen im Verhalten: auf dem jungen Blatt wird mehr Zeit mit Prüfbohren (einschließlich der Nahrungsaufnahme) und weniger Zeit mit Wandern verbracht. Wenn ein Insekt vorherige Erfahrung mit einem jungen Blatt hat, lehnt sie ein altes eher ab: unerfahrene Weibchen verlassen das Blatt nach durchschnittlich 6 Prüfstichen von je 3 min; erfahrene Weibchen verlassen das Blatt durchschnittlich nach 3 Prüfstichen von je 2 min. Junge Blätter enthalten sowohl mehr wasserlöslichen als auch Eiweiß-Stickstoff im Vergleich zu alten Blättern. Deshalb kann die Bevorzugung Adaptationswert haben. Mögliche Mechanismen, die bei der Weißen Fliege zur Wahl des Nahrungsplatzes führen können, werden besprochen. Das schließi sowohl die Beschaffenheit der betreffenden Stimula-tionsfaktoren (physikalische, chemische) ein, als auch den Teil des Blattes, aus welchem diese Stimulationsfaktoren stammen (Inhalt der Siebteile, Mesophyll, Oberfläche des Blattes). [ABSTRACT FROM AUTHOR]