Pavel Kindlmann

... ORIGINAL ARTICLE Intraguild predation: fiction or reality? Pavel Kindlmann Æ Katerina Houdková Special feature: biological control: theory and practice ... than in field conditions (eg, Pell et al. 1997; Losey and Denno 1998; Lucas et al. 1998; Hindayana et al. 2001; Burgio et al. ...

Территория, доступная энергия и долгота являются основными факторами, определяющими богатство орхидных флор. 1) видовое богатство возрастает с увеличение территории – зависимость вид-территория (ЗВТ). 2) Зависимость вид-энергия (ЗВЭ) показывает, что уровень доступной энергии, которая может быть трансформирована в биомассу, определяет видовое богатство. 3) В тропических широтах число видов на единицу площади намного превышает этот показатель для умеренных широт. Для апробации гипотезы о всех этих трех зависимостях, как определяющих видовое богатство орхидных мы вычислили Средневзвешенный растительный индекс, как меру энергии, доступной на определенных территориях. Было показано, что территория и географическая долгота гораздо более важны для видового разнообразия, чем доступная энергия.

We investigated, over the course of two years, the importance of landscape context on the abundance of aphids and their natural carabid enemies, which may help to develop effective strategies for reduction of aphid outbreaks in agricultural landscapes. This was undertaken in 12 wheat fields and in 12 maize fields each year in an agricultural landscape in western France. Our study area was characterized by hedgerows surrounding arable ?elds and permanent grasslands. Some areas did not change much over a few decades, while ?eld enlargement and removal of hedges appeared in some places following agricultural intensi?cation,. The present paper aimed at examining if the landscape context around crop fields affected the abundance of aphids (either directly, or indirectly via their natural enemies) and if this effect depends on the landscape scale considered. We observed that the abundance of aphids in the field was associated with landscape composition at large scale (500 m and 800 m). Th...

The frequency distribution of the durations of development of 516 larvae of Adalia bipunctata is unimodal, and the fast- and slow-developing larvae can be identified at the beginning of the fourth (=last) instar. To determine the advantages of fast and slow development, the survival, duration of development, growth and number of aphids consumed by fast- and slow-developing fourth instar larvae fed different numbers aphids were recorded. The percentages of fast- and slow-developing fourth instar larvae that survived when fed 0.5, 1 or an excess of aphids per day, surprisingly, did not differ. The slow-developing larvae of both sexes took longer to complete their development than the fast-developing larvae when fed 1 or an excess of aphids per day, and although the weights of the fast- and slow-developing fourth instar larvae differed at the beginning of the instar, they did not differ at the end of this instar when fed 1 aphid per day. However, when reared on an excess of aphids per ...

Foraging theory of aphidophagous ladybirds indicates that if a female is to maximize its fitness, it should not oviposit in patches where prey are scarce and/or unlikely to remain abundant long enough to support the growth of her offspring. It should therefore lay a few eggs during an “egg window” (Dixon, 1997), early in the development of a patch (Kindlmann & Dixon, 1993). Aphidophagous ladybirds lay most of their eggs over a relatively short period of time early in the development of aphid colonies. Some studies from Japan and Belgium (Jansen & Hautier, 2008; Yasuda & Katsuhiro, 1997) reported that Harmonia axyridis is a latecomer, that is, it comes later from hibernation sites and oviposits later. This means that H. axyridis does not oviposit only during the “egg window” and is able to adapt its life history strategies accordingly. For example, H. axyridis has a higher developmental threshold in comparison with other species (Sakuratani et al., 2000). Harmonia axyridis acts as a ...

Exclusion techniques, such as cages, are the most frequently used means of evaluating the efficiency of natural enemies in suppressing the abundance of their prey. The growth rates and peak densities of aphid populations within cages are usually larger than those in uncaged populations. However, cages change the microenvironment and prevent aphids from emigrating. Attempts were made to avoid the change in the microenvironment by using cages with a large (8mm) mesh. Here we test the hypothesis that because of the large mesh size, predators can easily penetrate into such cages during an experiment. Our results have shown that cages with a large (8mm) mesh size do not prevent predators from entering the cages and therefore cannot be used as "exclusion cages" for measuring the effect of predators on aphid numbers. Other methods of assessing the effectiveness of natural enemies in reducing the abundance of their prey, like removing the predators or direct observations, should b...

Over the last decades, agricultural intensification has caused a dramatic reduction of grassy habitats. This habitat loss has had a strong negative effect on many meadow-living insect populations, including butterflies. As a part of the cross-compliance measures of the Common Agricultural Policy of the European Union, subsidies for creation and maintenance of grassy field margins (GFM) have been launched. Among other environmental issues, they may serve as corridors for movement of various meadow-living species between individual meadows. Their role as corridors has, however, not yet been demonstrated at the landscape scale and their characteristics that most significantly increase landscape connectivity are unknown. Empirical data for such studies are missing, as the GFM subsidies were launched only 3 years ago. One possibility to get some predictions of their outcomes is provided by simulation models. Here we present our simulation results, using an extension of the model develope...

Some experiments indicate the ability of coccinellids to significantly suppress aphid abun- dance. Exclusion of predators by caging aphid-infested plants has repeatedly resulted in higher aphid populations and greater aphid population growth rates. However, aphidophagous coccinellids have never proved effective in controlling aphid populations in the field. To re- solve this apparent contradiction, a field experiment was used to determine

Plant species distributions are determined by the response of populations to regional climates, however, little is known about how alien plants that arrive in central Europe from climatically warmer regions cope with the temperature conditions at the early stage of population development. Ambrosia artemisiifolia (common ragweed) is an invasive annual plant causing considerable health and economic problems in Europe. Although climate-based models predict that the whole of the Czech Republic is climatically suitable for this species, it is confined to the warmest regions. To determine the factors possibly responsible for its restricted occurrence, we investigated the effects of temperature and nutrient availability on its seedlings. The plants were cultivated at one of seven temperature regimes ranging from 10 to 34 °C, combined with three nutrient levels. The data on the rate of leaf development were used to calculate the lower developmental threshold (LDT, the temperature in °C, bel...

The classical definition of evolutionary stability assumes that the fitness of each phenotype is fully determined by the composition of phenotypes in the population and by the strategies of each of these phenotypes. In natural populations, however, stochasticity often plays a crucial role in determining the fitness of an individual and a deterministic fitness function is probably rather rare. For example, choices of a new host plant, prey or oviposition patch are completely stochastic processes. Here we introduce a new definition of ESS that takes into account the effect of stochasticity on individual fitness. Then we show an application of this definition in a realistic system.

Ants are a major environmental factor for many insect species. For example, aphids and lycaenids have evolved an array of associations with ants ranging from obligate myrmecophily to the avoidance of contact. Here we (1) analyze the predictive power of different ecological and morphological traits for explaining the strength of the association between ants and aphids/lycaenids and (2) contrast different taxonomic levels with respect to the variance explained by ant attendance. Data come from a literature survey including 112 species of aphids and 103 species of lycaenids from Europe. For aphids, feeding on woody plant parts is positively associated with ant attendance, while a high degree of mobility, feeding in isolation, and the possession of wings in the adult stage are negatively associated with ant attendance. In lycaenids, feeding on inflorescences and feeding on Fabaceae host plants is closely associated with ant attendance, while living in forests bears a smaller likelihood ...