This study in Lithuania showed that the abundance dynamics of the common dormouse (Muscardinus avellanarius) populations were comparatively “smooth”, without outbreaks and crashes. Decreases and increases of abundance continued for some years, and abundance differed no more than three-fold in two successive years. A close negative correlation was revealed between spring population density and percentage of juveniles in the autumnal population. The last parameter is a consequence of reproduction success, which determined the scale of population increase in autumn and was due to several factors. Among them, proportion of breeding adult females had the greatest significance and was inversely proportional to population density in spring. Some young-of-the-year females usually joined the breeding process, when population density was low. The proportion of late breeding cases, when juveniles were born in September, was also negatively correlated with spring population density. The number of litters produced by one female during the season, and the average litter size also influenced reproduction success. The negative correlation between population density and reproduction success shows the presence of a reproduction success based pattern of density dependent self-regulation in M. avellanarius in the populations investigated.
Data on nesting densities of Bembix rostrata, a digger wasp inhabiting dynamic coastal dunes, were used to document the detrimental effects of trampling by cattle and vacationers. Both types of disturbance resulted in similar sand displacement and prey availability. Nesting densities of Europe's largest digger wasp declined dramatically with increasing trampling, probably below the critical population size. Hence, additional human disturbance, although resulting in similar environmental conditions compared to natural disturbance, significantly affected local population sizes. As a result, anthropogenic has to be avoided disturbance in order to restore or conserve natural dynamics and efforts to restore natural dynamics in a more natural way should be promoted. Although this is here only documented for one, large specialised invertebrate, the application of traditional management techniques, such as grazing by large herbivores, within newly evolved landscapes may introduce new pressures that affect pre-adapted species to natural disturbances negatively within short time spans.
The effects of body size on mating success and duration of copulation were investigated in Pyrrhocoris apterus. Under laboratory conditions relative mating success of small and large males was investigated in groups of 2 males (majority sex) : 1 female (minority sex). Large males were recorded significantly more often in copulation than small males when the female was large but not when the female was small. This was also the case when the group size was 24 males : 12 females or population density decreased by increasing the area of the experimental arena. In groups of 2females : 1 male, large females were recorded in copulation significantly more often than small females when the male was large but not when the male was small. Proportion of individuals of the minority sex that copulated was similar for males and females, regardless of body size. The average duration of copulation was similar for small and large males, but shorter for small than large females. The difference in the duration of copulation of small and large females was greater when it was with small rather than large males. The prolonged guarding of large females by small males may be explained by a trade-off between increasing the probability of inseminating an uneasily accessible high quality partner and copulating with more females.
The sika deer (Cervus nippon) is native to Japan and East Asia and has been introduced almost worldwide. Despite the wide distribution of the species, only few studies on its home range in non-native areas have been conducted. We focused on home range size and its seasonal and spatial dynamics in an introduced sika deer population in the Doupovské hory Mts., north-western Czech Republic. The mean home range size, obtained from ten subadult and adult males, was 3620 ha using the minimum convex polygon method, 1163 ha using the Brownian bridges method, and 819 ha using kernel estimation. The mean intra-individual home range overlap from
month to month was about 72 %, but decreased to 28 % when calculated for three-month periods. The unusually large home range sizes observed can be explained by a relatively low population density of the sika deer in the study area and possibly by the non-territorial mating strategy of males. The high values of seasonal home range overlap together with the time series of the monthly home range maps indicate some positional shifts but do not support presence of seasonal migration.
On the basis of previous studies of the common dormouse Muscardinus avellanarius concentrated on deciduous woodlands in the southern counties of Great Britain, it was stated that optimal habitat for M. avellanarius should contain a high diversity of suitable shrub and tree species to provide continuous food supply through activity season and appropriate physical structure. However, both the present review of M. avellanarius habitats within its distributional range and recent dormouse studies in other parts of Great Britain indicate that M. avellanarius actually inhabits a much wider variety of habitats, and do not require specialised habitats as previously supposed. M. avellanarius habitats in Lithuania differ considerably from the optimal habitats described for this species, about 40 % of localities being situated in coniferous- dominated forests. Habitat quality may result in a very low average population density of only about one adult per hectare. However, despite of absence of optimal habitats and low population density, M. avellanarius is widespread in Lithuania, and no decline is observed in their abundance and distribution. Forest management (increasing forest cover, planting of native tree species, not too large fragmentation of forest tracts) has been favourable for M. avellanarius in Lithuania.
According to hunting statistics in the last two decades, both the population numbers and harvesting of roe deer in Poland have been on the increase from 597000 to 876000 animals and from 158000 to 172000 harvested individuals, respectively. The number of roe deer reported by hunters are mainly based on guesswork, therefore the objective of the study was to verify the inventory of roe deer conducted by hunting clubs in the Myślibórz Forest District (north-western Poland) and to determine the sex ratio and age structure this species. The study area is including 86 small size forest complexes and covers 12990 ha. Roe deer number were determined over four years from 2002 to 2006. In sampling plots (February 2002) data from snow tracking and driving census showed significant correlation (r = 0.663, p = 0.003) between the relative population density (N/km) – independent variable and population density (N/1000 ha) – dependent variable. Roe deer snow tracks were counted during five days each year on 16 line transects (length 66.4 km) and the relative population densities (animal per km*day–1) for the whole study area were calculated. These indices were inserted into the regression formula that was obtained from sampling plots. It allowed to calculate the population density (N/1000 ha) and then roe deer numbers inhabiting the study area. Population density ranged from 300.1-319.0 individuals/1000 hectares of forest, and the differences between the four years of study were statistically insignificant. In summer, the sex ratio of the population was 1:1.4 in favour of females, and the autumn increment of young animals amounted to 70.2 fawns/100 does. The average population number of roe deer assessed for these four years was 3568 individuals and was more than two times higher than the average population size (n = 1670) given by hunters.
Species in the carnea complex of the common green lacewing are predators of the common pistachio psylla, Agonoscena pistaciae in both cultivated pistachio plantations and on wild pistachio plants in Iran. The seasonal occurrence of common green lacewings was monitored in pistachio orchards from 2007 to 2008. In addition, the effect of different temperature regimes on preimaginal development, survival and prey consumption of the predatory lacewing Chrysoperla lucasina fed on A. pistaciae nymphs were studied under controlled conditions. The adults of common green lacewings first appeared on pistachio trees in mid April and were most abundant in early July, decreased in abundance in summer and increased again in October. The relative density of common green lacewings was higher in pistachio orchards where the ground was covered with herbaceous weeds than in those without weeds. In the laboratory females of C. lucasina laid an average of 1085 eggs over 60 days at 22.5°C. The maximum prey consumption occurred at 35°C when the larvae consumed 1812 fourth instar psyllid nymphs during their larval period. The intrinsic rate of natural increase (rm) was 0.11. The total development (egg-adult) required 385 degree-days above the theoretical lower developmental threshold of 9.6°C. and Fatemeh KAZEMI, Mohammad Reza MEHRNEJAD.
After high population densities of insect defoliators there is often a dramatic decrease in their abundance due to various limiting factors. Here, we compared gypsy moth larvae (Lymantria dispar L.) reared singly and in crowded conditions. We compared a number of physiological parameters of these insects and the effect of L. dispar population density on the activation of covert baculovirus infections in the larvae. It was found that the population density of gypsy moth larvae did not affect the mortality due to the activation of the covert virus infection or the total mortality. On the other hand, solitary-reared larvae were heavier, took longer to develop, and showed a four-fold higher concentration of dopamine in their haemolymph than larvae reared in groups. Thus, we demonstrated that an increase in the population density of larvae per se facilitates some changes in fitness and innate immunity traits but is not related to the activation of covert baculovirus infection. We suggest that an increase in population density does not increase the risk of epizootics triggered by the activation of covert baculovirus infection and that researchers should pay more attention to studying density-associated factors, such as starvation.
Throughout most of the distributional range, the fat dormouse, Glis glis, relies heavily upon European beech as a key species in its habitat. In Lithuania however, situated beyond the continuous range of the beech, pedunculate oak becomes the essential tree in habitats of G. glis. In Lithuania, the dormouse activity season lasts from mid-May to mid-October, young are born during the short period from late July to mid-August, and the mean litter size is 5.9 young. Population density is low (0.8-2.0 ind./ha after hibernation and 1.2-4.8 ind./ha in autumn), but relatively stable. The mean body weights of adults (98 g after hibernation and 128 g before hibernation) are among the lowest across the range. Lithuanian dormice differ from those living in beech-dominated habitats by their lower population density and lower body weight. Such differences may be due to acorns being less suitable food for G. glis in comparison to beech nuts. In terms of inter-annual abundance dynamics, the G. glis population is comparatively stable as years in which dormice fail to reproduce are infrequent in Lithuania.
The common pistachio psyllid (CPP) is thought to respond to nutrient availability in pistachio trees. We determined the effect of a deficiency of leaf iron (Fe) has on the abundance of the pistachio psyllid at a regional scale. First, we monitored the abundance pistachio psyllid in four pistachio orchards (24 trees as 24 repetitions) located in Maybod County, Yazd province in the centre of Iran and then measured leaf nutrient levels. Orchards were located up to 2.6 km apart. Multivariate regressions were used to determine the relationship between leaf nutrients and CPP population growth. The results indicate that the number of psyllid eggs and population growth rate of the nymphs was negatively correlated with Fe levels in the leaves, while peak numbers of psyllid eggs were positively correlated with the levels of Cu in the leaves. In a manipulative field experiment, we conducted two experiments: (1) pistachio trees treated with iron compared with control trees, and (2) pistachio trees previously treated with iron were treated with ammonium sulphate and compared with trees treated with ammonium sulphate. In the first experiment, psyllids in leaf disc-cages had a significantly greater intrinsic rate of population increase and net reproductive rate on Fe-treated trees than the control trees (Stage 1). In the second experiment, psyllids in leaf disc-cages had similar intrinsic rates of population increase and net reproduction both on the ammonium sulphate treated trees (control) and those previously treated with iron. This indicates that iron may have reacted negatively with nitrogen content of the leaves. In general, these findings indicate that when there is a deficiency of iron in the leaves, the application of nitrogen fertilizer had little effect on the performance of CPP and may have played a minor role in the population dynamics of CPP, but the application of a Fe fertilizer without considering the nitrogen content of the leaves may lead to a population outbreak.