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Featured researches published by Alois Honek.


Journal of Applied Ecology | 2013

Temperature effects on pitfall catches of epigeal arthropods: a model and method for bias correction

Pavel Saska; Wopke van der Werf; Lia Hemerik; M. L. Luff; Timothy D. Hatten; Alois Honek

Summary Carabids and other epigeal arthropods make important contributions to biodiversity, food webs and biocontrol of invertebrate pests and weeds. Pitfall trapping is widely used for sampling carabid populations, but this technique yields biased estimates of abundance (‘activity‐density’) because individual activity – which is affected by climatic factors – affects the rate of catch. To date, the impact of temperature on pitfall catches, while suspected to be large, has not been quantified, and no method is available to account for it. This lack of knowledge and the unavailability of a method for bias correction affect the confidence that can be placed on results of ecological field studies based on pitfall data. Here, we develop a simple model for the effect of temperature, assuming a constant proportional change in the rate of catch per °C change in temperature, r, consistent with an exponential Q10 response to temperature. We fit this model to 38 time series of pitfall catches and accompanying temperature records from the literature, using first differences and other detrending methods to account for seasonality. We use meta‐analysis to assess consistency of the estimated parameter r among studies. The mean rate of increase in total catch across data sets was 0·0863 ± 0·0058 per °C of maximum temperature and 0·0497 ± 0·0107 per °C of minimum temperature. Multiple regression analyses of 19 data sets showed that temperature is the key climatic variable affecting total catch. Relationships between temperature and catch were also identified at species level. Correction for temperature bias had substantial effects on seasonal trends of carabid catches. Synthesis and Applications. The effect of temperature on pitfall catches is shown here to be substantial and worthy of consideration when interpreting results of pitfall trapping. The exponential model can be used both for effect estimation and for bias correction of observed data. Correcting for temperature‐related trapping bias is straightforward and enables population estimates to be more comparable. It may thus improve data interpretation in ecological, conservation and monitoring studies, and assist in better management and conservation of habitats and ecosystem services. Nevertheless, field ecologists should remain vigilant for other sources of bias.


Weed Science | 2006

Seed age and storage conditions influence germination of barnyardgrass (Echinochloa crus-galli)

Zdenka Martinkova; Alois Honek; Jan Lukas

Abstract Germination was investigated in 1-yr and 8-yr-old seed lots of barnyardgrass. Each seed lot was divided into a portion stored dry at 25 C (afterripening) and a portion buried in the field (stratification) in central Europe (latitude 50°N, longitude 14°E). The afterripened seed lost dormancy within 2 yr after dispersal, whereas buried seed passed through annual dormancy/nondormancy cycles. The seed was germinated at five constant temperatures between 17 and 35 C with an 18/6-h light/dark photoperiod. Germination was affected by both seed age and storage conditions. Germination percentage and rate in 8-yr-old afterripened and each of the stratified seed lots varied with temperature. Optimum temperatures for germination were between 27 and 31 C, and the range of adequate temperatures increased with seed age. A common base temperature for germination was 11.7 C. In 1-yr-old afterripened material, the proportion of germinating seed (<u20095%) and germination rate were similar at all temperatures. Barnyard...


Current opinion in insect science | 2017

Spatial and temporal changes in the abundance and compostion of ladybird (Coleoptera: Coccinellidae) communities

Alois Honek; Anthony Fg Dixon; António O. Soares; Jiri Skuhrovec; Zdenka Martinkova

Because of their services to agriculture most ladybirds (Coleoptera: Coccinellidae) are intensively studied predators of mainly phytophagous pests. The study of the long-term variation in the composition of their communities was stimulated by recent dramatic changes in the abundance of some species. We review and evaluate possible effects of the main causes cited in the literature. Agricultural and habitat changes (particularly urbanization) affect coccinellid abundance, both negatively and positively. In the temperate zone dominant species occur most frequently associated with abundant prey populations on crops, weeds and planted stands of trees resulting from human activity. Invasive non-native species of coccinellids may endanger native species through intraguild predation or competition for resources, but their supposed serious negative effects on native species can differ considerably. Climatic change may influence coccinellid species in several ways, including indirect effects through lower trophic levels and desynchronisation of the phenologies of host plants, prey and coccinellid populations. In the near future we do not expect climate warming to have important effects on ladybird diversity globally, but local changes in the composition of coccinellid communities and abundance of particular species could occur.


Annals of The Entomological Society of America | 2008

Synchronization of a Coleopteran Parasitoid, Brachinus spp. (Coleoptera: Carabidae), and Its Host

Pavel Saska; Alois Honek

Abstract Laboratory experiments have shown that larvae of ectoparasitoids Brachinus explodens Duftschmid and Brachinus crepitans (L.) (Coleoptera: Carabidae) develop on pupae of spring breeding species of the genus Amara (Coleoptera: Carabidae). In this study, we investigated the synchronization of the critical stages of host and parasitoid in the field. We simulated the development of both genera under field conditions in spring 2003, combining 1) field data (activity-density measured by pitfall traps and oviposition), 2) thermal constants for development (lower development threshold and sum of effective temperatures), and 3) meteorological data (average daily temperature at a depth of 2.5 cm). In early spring, adults of Amara oviposited in weedy areas, which provided plenty of seed with which to feed their larvae. Pupation was predicted to occur from June to early July. Brachinus adults arrived later than their hosts, and females started to oviposit when Amara larvae were just about to pupate, and Brachinus larvae hatched when Amara pupae became available. The synchronization of the critical stages of host and parasitoid observed in the field strongly supports the existence of a host-parasitoid relationship between Amara pupae and Brachinus larvae.


Ecological Entomology | 2015

Detecting seasonal variation in composition of adult Coccinellidae communities

Alois Honek; Zdenka Martinkova; A. F. G. Dixon

1. Following its recent global spread, Harmonia axyridis (Coleoptera: Coccinellidae), an aphid predator of East Palearctic origin, dominated local coccinellid communities. While long‐term trends in this change are well documented, little is known about seasonal changes.


Malacologia | 2007

A Field Method For Quantifying the Grazing Activity Of Slugs, With Particular Reference To Arion lusitanicus (Mollusca)

Alois Honek; Zdenka Martinkova

In earlier experiments soft, “plasticine” modelling clay was readily consumed by slugs. Therefore, a method for determining the grazing activity of Arion lusitanicus using plasticine baits was tested in the field. Plasticine was exposed on the surface of the soil in small trays shielded from mice by wire mesh screens. After several days of exposure, the quantity of plasticine consumed was determined by weighing. Laboratory experiments showed that the amount of plasticine consumed is proportional to slug body mass, plasticine is eaten over a wide range of temperatures between 6–25°C, and the presence of alternative vegetable food does not decrease consumption. In the field, consumption of such baits was positively correlated with slug numbers and revealed variation in slug grazing activity between sites during the course of a season. The use of plasticine baits is recommended for establishing slug feeding activity in the field. This is probably the best method available to date for quantitative studies. Plasticine was also eaten by several other species of slugs and snails.


Plant Ecology | 2011

Asymmetrical intraspecific competition in Echinochloa crus-galli is related to differences in the timing of seedling emergence and seedling vigour

Zdenka Martinkova; Alois Honek

Individual size is an important factor that determines fitness in annual plants. Variation in size originates at the seedling stage based on differences in seedling vigour and time of emergence, ensuing asymmetrical intraspecific competition between early- and late-established plants. The effects of the order of seedling emergence on characteristics of barnyard grass (Echinochloa crus-galli) were studied. In the first experiment, competition between pairs of plants, one of which was sown and emerged 0, 3, 6 or 12xa0days earlier than the other, was determined. In the second experiment, competition between two plants that were sown at the same time, but emerged at different times because of variation in seed quality, was determined. Competition decreased plant mass, tillering, height and the number of caryopses per panicle, but not time to earing or root/shoot ratio. Plants that were sown 3xa0days after the first plants in competing pairs grew to 32% of the size of solitary control plants, with the effect of competition accounting for 40% and asymmetrical competition 28% of the total reduction in size. When a 3-day lag in germination was determined intrinsically, plant size was reduced to 19% of the control, with the effect of competition accounting for 34%, asymmetrical competition 15% and poor intrinsic quality of the plant 32% of the total reduction in size. Small environmentally induced delays and more importantly, intrinsically induced delays in the time of emergence result in a considerable decrease in final plant size and fitness.


Ecology and Evolution | 2014

Plasticity of the thermal requirements of exotherms and adaptation to environmental conditions

Alois Honek; Zdenka Martinkova; Jan Lukas; A. F. G. Dixon

In exothermal organisms, temperature is an important determinant of the rate of ecophysiological processes, which monotonically increase between the minimum (td min) and maximum (td max) temperatures typical for each species. In insects, td min and td max are correlated and there is a approximately 20°C interval (thermal window WT = td max − td min) between them over which insects can develop. We assumed that other exotherms have similar thermal windows because the thermal kinetics of their physiological processes are similar. In this study, we determined the thermal requirements for germination in plants. Seeds of 125 species of Central European wild herbaceous and crop plants were germinated at nine constant temperatures between 5 and 37°C, and the time to germination of 50% of the seeds D and rate of germination R (=1/D) were determined for each temperature and the Lactin model used to determine td min, td max, and WT. The average width of the thermal windows for seeds was significantly wider (mean 24°C, 95% CI 22.7–24.2°C), varied more (between 14.5 and 37.5°C) and development occurred at lower temperatures than recorded for insects. The limiting temperatures for germination, td min and td max, were not coupled, so the width of the thermal window increased with both a decrease in td min and/or increase in td max. Variation in WT was not associated with taxonomic affiliation, adult longevity, or domestication of the different species, but tends to vary with seed size. Plants are poor at regulating their temperature and cannot move to a more suitable location and as a consequence have to cope with wider ranges in temperatures than insects and possibly do this by having wider thermal windows. Synthesis: The study indicated specificity of WT in different exotherm taxa and/or their development stages.


Journal of Insect Physiology | 2012

Efficiency of host utilisation by coleopteran parasitoid

Pavel Saska; Alois Honek

In insect larvae, optimising food utilisation with respect to available meals and time is essential for achieving maximum adult body size, which is a relevant proxy of fitness. We studied the efficiency of food conversion, body size, mortality, and development time in a solitary idiobiont ectoparasitoid, Brachinus explodens (Coleoptera: Carabidae), reared in the laboratory on the pupae of another carabid genus, Amara. The efficiency of conversion index (ECI - ratio of ingested to assimilated food) was, on average, 54.1±1.1% (n=76), with a minimum of 26.9% and a maximum of 81.6%. The rate of increase in biomass gained (W(gained)) with biomass of the host was constant in females, but it decreased in males over the range of host body mass. Females, therefore, grew heavier from hosts of the same mass compared to males. Body length increased with the host mass and was correlated with W(gained) identically for both sexes. Mortality was unaffected by the host mass, but it significantly increased below 20°C. In contrast, the development time of the feeding phase of the larva increased with the host mass at 20.3 and 23.7°C, but it remained unaffected at 26.9°C and in all three temperatures considering pupal development. W(gained) increased with development time up to ca. 8 days of larval feeding at 23.7°C. To our knowledge, our data are the first on food utilisation in solitary idiobiont coleopteran ectoparasitoids, and they present the highest values of ECI in insects.


Journal of Economic Entomology | 2018

Aphids (Homoptera: Aphididae) on Winter Wheat: Predicting Maximum Abundance of Metopolophium dirhodum

Alois Honek; Zdenka Martinkova; Pavel Saska; A. F. G. Dixon

Abstract In Central Europe, the most abundant aphid infesting the leaves of small grain cereals is Metopolophium dirhodum (Walker) (Homoptera: Aphididae). Annual variation in its seasonal dynamics was evaluated using a 25-yr series of standardized weekly censuses of winter wheat plots. M. dirhodum made up >50 % of the aphids on the foliage. Date of immigration (8 May–3 July), length of period of population increase (0–9 wk), and date of attaining maximum abundance (28 May–22 July) varied greatly. For the prediction, we regressed maximum numbers/tiller on numbers recorded in the first week after heading. The regression of maximum abundance on nonzero aphid counts revealed a critical number of ≥1.50 aphids/tiller, which if exceeded resulted in a harmful maximum abundance of ≥10 aphids/tiller at the peak. Zero aphid counts resulted in 10% of cases with a harmful maximum abundance. Using this regression for prediction will result in 18% of the recorded cases being false negatives and 9% false positives. Parallel annual variation in the average maximum numbers of M. dirhodum, Sitobion avenae (Fabricius) (Homoptera: Aphididae), and Rhopalosiphum padi (Linné) (Homoptera: Aphididae) indicated the following factors that affected their abundance: temperature in winter and host plant quality. The predictions apply only in areas where M. dirhodum is holocyclic and aphids do not overwinter in wheat stands.

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Zdenka Martinkova

Research Institute of Crop Production

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Pavel Saska

Czech University of Life Sciences Prague

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A. F. G. Dixon

University of East Anglia

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Vojtech Jarosik

Charles University in Prague

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Miroslav Barták

Czech University of Life Sciences Prague

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Pavel Štys

Charles University in Prague

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Petr Bogusch

University of Hradec Králové

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Petr Janšta

Charles University in Prague

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F.J.J.A. Bianchi

Wageningen University and Research Centre

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