The aphid alarm pheromone is known to trigger wing induction in pea aphids (Acyrthosiphon pisum). In reaction to alarm pheromone, aphids drop off the plant or walk away. While searching for a new feeding site they repeatedly encounter other members of the aphid colony and this increased contact rate is assumed to be important for wing induction ("pseudo-crowding" hypothesis). Because the encounter rate is a function of aphid colony size, wing induction in aphids in the presence of a predator should be a function of the number of aphids on the plant. We placed two, seven or 13 adult pea aphids on bean plants, and exposed the different-sized colonies to synthetic alarm pheromone to test the density-dependence of predator-induced wing induction. The mean percentage of winged morphs among the offspring produced on the plants ranged from 10 to 80 percent and increased both with aphid number and exposure to alarm pheromone. There was no synergy between aphid number and alarm pheromone exposure indicating that both factors are additive. The implications for aphid metapopulation dynamics are discussed.
During the winter period 2006/2007, research was carried out on the distribution and number of black grouse in coniferous lowland forest, Bory Dolnośląskie and the Karkonosze Mountains in southwest Poland. During 27 workshops, more than 800 members of various hunting clubs and representatives of the local State Forest Service presented information about place i.e., forest compartments and date when black grouse was seen. Next, this information was put on forest maps. Birds that could be seen twice of more were arbitrarily excluded by time-space analysis. In Bory Dolnośląskie, a declining black grouse population was present in 12 hunting districts covering 50.5 thousands ha of forest. The estimate of this species was 60 birds, i.e., 1.18 birds per 1 000 ha. In the Karkonosze Mountains, increasing black grouse population occurred in 8 hunting districts within a forest area of 30.1 thousands ha. The black grouse number was estimated to 169 birds, i.e., 5.61 birds per 1 000 ha. In the heather-land of Bory Dolnośląskie, 200 artificial nests were distributed on transect lines between the habitat (A) where black grouse is still present and the one (B) where it disappeared, and 14 movable digital cameras with movement detector triggered by infrared sensor were temporarily located at randomly selected nests that were destroyed by predators. The picture analysis showed that raven (Corvus corax) destroyed 93.9% and red fox (Vulpes vulpes) 6.1% of the nests. All the nests were damaged within 7 days. The rate of nest damage was faster in habitat B. Population dynamics of lowland and mountain black grouse population is analysed and discussed.
Eurytoma robusta Mayr (Chalcidoidea) exploits host galls either as a primary or secondary parasitoid, an entomophytophagous inquiline or occasionally even as a predator. We present data on its ecology and impact on gall densities and population trends of the gall fly Urophora cardui (L.) on Cirsium arvense (L.) Scop. Habitat preference, host gall selection, clutch size, and high incidence of superparasitism causing empty gall cells show that E. robusta, a generalist with a broad host spectrum, is relatively poorly adapted to parasitising U. cardui. The influence of E. robusta on U. cardui in the Belfort-Sundgau region (1970-2004), in the Upper Rhine Valley (1973-2004) and in north-eastern Bavaria (1977-2004), differed considerably. In the forests of the Upper Rhine Valley and the Belfort-Sundgau region, where U. cardui has relatively stable source-sink populations, E. robusta is present but not the dominant mortality factor of the gall fly. In most areas of north-eastern Bavaria U. cardui occurs in fragmented populations and short lived non-equilibrium metapopulations. In these systems E. robusta became more abundant over the last five years, which resulted in a high incidence of superparasitism, an increase in the number of empty gall cells and reduced gall quality. The greatly increased degree of parasitism and an excess of empty cells resulted recently in the collapse of most local populations of U. cardui in the study area south of Bayreuth (north-eastern Bavaria). Together with earlier records the data presented here suggest that in north-eastern Bavaria E. robusta cause fluctuations in the abundance of U. cardui, which have a periodicity of 5-7 years. A remarkable feature of the oligophagous E. robusta is its high fidelity to formerly abundant U. cardui populations, which, with declining host densities, leads to overexploitation, resulting in a high incidence of superparasitism and high larval mortality. The possible influence of the habitat structure on the effect of E. robusta on the population dynamics of U. cardui is discussed. Our data plus that of other authors suggest that, with regard to U. cardui, E. robusta can develop a temporary local host specialisation.
The dietary structure and distribution patterns in pine martens Martes martes in situations of different food supply in the coniferous forest of north-eastern Belarus were investigated. A total of 1222 scats were analysed, and snowtracking of pine martens was done each winter. Seven pine martens were radiotracked (n=7549 radiolocations). Abundance of the main prey was monitored. The pine marten acts both as an active predator, mostly taking many species of rodents and birds, and as a gatherer, feeding on fruits and scavenging for carrion. In the ecologically poor woodland on sandy soil the predator specializes in feeding on carrion in the cold season, and on berries in the warm season. The richer food supply in the woodland on clay soil results in a markedly higher population density and fairly even distribution of pine martens than those in the woodland on sandy soil, where pine martens mainly live in valley habitats. The winter density of bank voles drives the pine marten numbers. Also biomass of carrion is a crucial factor determining the predator density by late winter.
he painted lady butterfly (Vanessa cardui) (Lepidoptera: Nymphalidae: Nymphalinae) is well known for its seasonal long-distance migrations and for its dramatic population fluctuations between years. Although parasitism has occasionally been noted as an important mortality factor for this butterfly, no comprehensive study has quantified and compared its parasitoid complexes in different geographical areas or seasons. In 2009, a year when this butterfly was extraordinarily abundant in the western Palaearctic, we assessed the spatial and temporal variation in larval parasitism in central Morocco (late winter and autumn) and north-east Spain (spring and late summer). The primary parasitoids in the complexes comprised a few relatively specialized koinobionts that are a regular and important mortality factor in the host populations. However, there was a strong seasonal variation in the level of parasitism. In Spain percentage parasitism was more than four times higher in late summer than in spring (77.3% vs. 18%), while in Morocco it was five times higher by the end of winter than in the autumn (66.2% vs. 13.2%). In both regions the build up of parasitoid populations occurred after V. cardui had bred in the same general area over successive generations, and this may represent a selective force favouring seasonal migration to enemy-free space., Constanti Stefanescu ... [et al.]., and Obsahuje seznam literatury
This study reports seasonal presence of Coccinella septempunctata L. (Coleoptera: Coccinellidae) in Southeast Turkey, in 2008, 2009 and 2010. Samples were collected from crops in agricultural areas at altitudes of 10 m, 800 m and 1400 m from stands of wild herbaceous plants , and at 1750 m from stone debris fields. First C. septempunctata adults were collected at the beginning of June at Tentcamp (800 m) and Tozlu (1400 m), early in July at Sarikiz (1700 m) when the mean air temperature reached 30°C. Adults became active in spring, after aestivating around Sarikiz and overwintering there under snow. First adults emerged on 2nd April in 2009 around Edremit Gulf when mean air temperature reached 14.8°C. Adult and immature stages of C. septempunctata were recorded attacking aphid populations till the end of June. C. septempunctata was present there for only one period each year during which they completed one generation. Adult individuals of this generation returned to Mount Ida to aestivate. Maximum numbers of adults present on Mount Ida in the first week of August in 2009 and 2010 were recorded. C. septempunctata adults aestivate and overwinter at Sarikiz on Mount Ida after completing their development on aphids in April, May and June around Edremit Gulf., Ali Özpinar, Ali Kürşat Şahin, Burak Polat., and Obsahuje bibliografii
Species diversity and potential impact of cocoon parasitoids on the abundance of the common pine sawfly, Diprion pini L. (Hymenoptera: Diprionidae), were explored in different forest habitats, with endemic sawfly populations, by the regular exposure of laboratory reared sawfly cocoons. Different cocoon spinning sites of the sawfly were simulated by exposing cocoons at several strata (soil, litter, trunk and stem of pine trees) in a forest. In more fertile, mixed spruce/pine-forests, parasitism on exposed cocoons was lower than in typical outbreak stands with a lower vegetational diversity. The parasitoid communities comprised of up to nine parasitoid species, which showed temporal and spatial niche separation. The ichneumonid Pleolophus basizonus Grav. (Hymenoptera: Phygadeuontinae) occured throughout the season at all strata as well as in all forest types. The ichneumonid Gelis cursitans F. (Hymenoptera: Phygadeuontinae) was only found in pine forests with sparsely developed ground vegetation, parasitizing exposed cocoons in the upper story in spring. The torymids Monodontomerus dentipes Dalm. (Hymenoptera: Torymidae) and M. minor Ratz. (Hymenoptera: Torymidae) were present in all forest types, but parasitized commonly only cocoons in the upper story in summer. Apparently, these generalists can quickly respond to increased densities of upper story exposed "summer" cocoons and thus limit the population growth of the pine sawfly due to the development of a second generation.
The ladybird beetle Harmonia axyridis Pallas was investigated under laboratory conditions to clarify the relationship between food abundance or scarcity and ovarian development or oosorption. Four conditions were used: (1) fully fed for 24 h, (2) 24-h starvation, (3) 48-h starvation, and (4) 24-h starvation followed by 24-h re-feeding. Body length and initial body weight were not significantly related to the number of ovarioles per female. Both starvation conditions significantly increased the percentage of oosorptive individuals and ovarioles per female, and significantly decreased the percentage of mature ovarioles per female. Re-feeding for 24 h after a 24-h starvation resulted in a significantly higher percentage of mature ovarioles per female; however, the percentage of mature ovarioles remained lower than in the fully fed condition. Oosorption mainly occurred during the intermediate developmental stage of the ovarioles. The rates of ovarian development and oosorption in predatory H. axyridis were much faster compared with those in herbivorous ladybird beetles. Body length, initial body weight, and the number of ovarioles were significantly correlated with the number of eggs laid during the last 24 h of each experimental condition. From an analysis of the weight loss and the number of eggs laid during the last 24 h of each experimental condition, it appears that the realized weight of the eggs may be directly determined by the amount of food digested by the adult. The ovarian development and oosorption were asymmetric in the right and left ovaries. These may be important strategies for oviposition in H. axyridis, because selective provision of maturing ovarioles in the right or left ovary with digested nutrients would favor their development. In addition, the energy loss through oosorption during the intermediate developmental stage of oocytes would be less than the energy loss resulting from the resorption of mature oocytes. Therefore, one role of the ovary in H. axyridis, in addition to egg production, might be as a kind of energy storage system for increasing reproductive success. An immediate start of ovarian development under favorable feeding conditions and rapid oosorption during food scarcities may be an adaptive ovipositional and survival strategy for female adults of H. axyridis in response to heterogeneous and fluctuating resource conditions.