Balázs Kiss

Factors influencing cannibalism in the wolf spider Pardosa agrestis (Araneae, Lycosidae)

Abstract Cannibalistic tendencies are well known in spiders and may be a significant factor influencing population size. The wolf spider, Pardosa agrestis, is the dominant non-web-building spider in a wide range of central European agricultural habitats. Preliminary field observations indicated an extended reproductive period, which results in a very wide size distribution of juvenile instars. We hypothesised that if cannibalism is enhanced by differences in size, especially during periods when prey is scarce, these populations might be susceptible to cannibalism in an ecologically significant way. Laboratory studies were conducted on juvenile P. agrestis in arenas. We analysed the following specific aspects of cannibalism: (1) the effect of the weight ratio between the opponents; (2) the effect of weight per se, and (3) the role of hunger level in determining cannibalistic tendencies of spiders. The role of weight and hunger were analysed in separate experiments, in both cases by controlling for the other variable. The results showed that cannibalism was strongly positively correlated with both weight ratio and hunger, but absolute size/age of an individual could not predict the occurrence of a cannibalistic event. These experiments generated the plausible hypothesis that cannibalism might be an important phenomenon in the regulation of real populations, which should be tested specifically in future field experiments.

COMPARISON OF AUTUMN AND WINTER DEVELOPMENT OF TWO WOLF SPIDER SPECIES (PARDOSA, LYCOSIDAE, ARANEAE) HAVING DIFFERENT LIFE HISTORY PATTERNS

Abstract Pardosa species do not overwinter in the adult stage in the Holarctic region, therefore penultimate instars should avoid precocious maturation in autumn. We tested how artificially increased temperature and/or lengthened light regime would affect the pre-overwintering development of two common species with different phenological patterns. Juvenile instars of Pardosa agrestis (Westring 1861) and P. hortensis (Thorell 1872) were collected in autumn from the field. The experimental spiders were held either indoor at 26 °C or outdoors at ambient temperature and were exposed either to short or to long daylength. Molting events were monitored for five months. At outdoor temperatures no spiders reached adulthood and molts of younger instars occurred more frequently at long daylength. In the indoor temperature groups all P. hortensis and the majority of P. agrestis individuals reached adulthood during the experiment. Long daylength treatment enhanced the effect of increased temperature by almost halving the time needed to reach adulthood in both species. Penultimate instars of both species needed at least 17 days to molt, while earlier instars, present only in P. agrestis, responded rapidly to higher temperature by molting. This stage dependent response suggests that earlier instars can use favorable autumnal temperatures to catch up with penultimate instars which leads to higher synchrony of developmental stages in the overwintering and spring populations.

Life History Adaptation to Changeable Agricultural Habitats: Developmental Plasticity Leads to Cohort Splitting in an Agrobiont Wolf Spider

Abstract The wolf spider, Pardosa agrestis Westring (Araneae: Lycosidae), is a dominant arthropod predator in central European agricultural areas. Recent studies have indicated that this spider has a unique phenology among Pardosa species. Three years of systematic field monitoring of a P. agrestis population in Hungary confirmed that an early summer peak (P1) of adults typical of the Pardosa genus is followed by a second late summer peak (P2) that does not occur among congenerics. Rearing experiments conducted outdoors revealed that offspring from P1 can reach maturity in ≈2 mo time, well before the end of summer. Thus, P2 adults represent a second generation of the species, with a chance for a potentially successful reproduction. However, the speed of development was variable among P1 offspring; individuals, which proved to be slower developers, did not mature during P2; rather they overwintered as juveniles and matured during the following year P1 period. Thus, members of the P1 cohort followed different developmental pathways; this corresponds to a cohort-splitting strategy. Splitting occurred even among spiderlings originating from the same clutch (cocoon) at the beginning of P1. In contrast, spiderlings born at the end of P1 uniformly matured by next spring. Splitting among offspring spreads the mother’s reproductive success between risk averse slow-developing and risk prone fast-developing offspring. The facultative bivoltine life cycle arising through cohort splitting may allow P. agrestis to adapt to predictably ephemeral agricultural habitats by flexibly producing the most dispersive juvenile stages in synchrony with the appearance of vacated habitats.

THE FUNCTION OF LONG COPULATION IN THE WOLF SPIDER PARDOSA AGRESTIS (ARANEAE, LYCOSIDAE) INVESTIGATED IN A CONTROLLED COPULATION DURATION EXPERIMENT

Abstract Copulation duration varies greatly in wolf spider species, ranging from a few seconds to several hours. In Pardosa agrestis (Araneae, Lycosidae), the most common ground dwelling spider in Central European fields, copulation typically takes more than two hours. Since long copulation is likely to entail certain costs, we address the question, “what is the function of long copulations?” We investigated the consequences of lengthy copulation in an experimental situation, where copulations either ended spontaneously, or were interrupted after 10 min, 40 min or 90 min. There was no difference in the number of offspring per female when treatments were compared and we conclude that ten minutes of copulation was sufficient to fertilize all the eggs of a female. Long copulations should therefore have other functions than securing the necessary amount of sperm for fertilization. We also found that neither the time until egg production after copulation, nor offspring size was affected by copulation duration. This suggests the lack of transfer of ejaculatory substances that would either stimulate the egg sac formation or increase the size of the spiderlings. We propose that prolonged copulations gain meaning in multiple mating situations and should play a role in sperm competition or other forms of sexual selection. The extra time may be used for copulatory courtship, or for the transfer of surplus sperm or other substances to manipulate the females willingness to copulate with other males, or to use sperm from them. These hypotheses remain to be tested in multiple mating experiments.

Feeding behaviour of a virus-vector leafhopper on host and non-host plants characterised by electrical penetration graphs

Many sap‐feeders are vectors of plant diseases, acquiring and inoculating pathogens at various stages of the feeding process. In oligophagous species, certain aspects of probing behaviour on hosts and non‐hosts may have implications for the range of both pathogens and plants that can be inoculated. We addressed the question of which probing phases (including ingestion) occur on non‐host plants in the case of the common leafhopper Psammotettix alienus (Dahlbom) (Hemiptera: Cicadellidae). This species is a pest on cereals, a vector of the Wheat dwarf virus, and possible carrier of other pathogens. It is regarded as oligophagous on grasses, but has been reported also on other plant families. In a combined electrical penetration graph (EPG) video observation study, we aimed to give a description of the waveforms during the probing process. EPG recordings were made on a suitable host, barley, Hordeum vulgare L. (Poaceae), and on two non‐host plants, the sedge Carex tomentosa L. (Cyperaceae) and the ragweed Ambrosia artemisiifolia L. (Asteraceae). We demonstrated that P. alienus probes on plants other than Poaceae, including dicotyledons. Univariate and multivariate analyses of general probing variables revealed that total and maximal probe durations were shorter and probing progress less advanced on non‐host plants. Waveforms of the pathway phase were stereotypical and statistically not different between the host and non‐host plants. On sedge, the waveform signifying insertion through the plant epidermis was shortened but much more frequent, indicating penetration difficulties and retrials. Most importantly, waveforms indicating phloem ingestion were not present on either of the non‐host plants. Non‐host probing events terminating during the pathway phase suggested that rejection occurred when the stylets were in the mesophyllum. Overall, the EPG signals reflected the unsuitability of A. artemisiifolia and C. tomentosa compared to barley, but the occurrence of probing and the demonstrated level of probing progress imply that pathogen transmission cannot be excluded in the case of many non‐host plants and non‐specific pathogens.

The nucleotide sequence of barley strain of Wheat dwarf virus isolated in Hungary.

Barley-infecting isolates of WDV were collected in the field of near Sofia. The complete genomes of two isolates were amplified by PCR, cloned into pGEM-T plasmid and sequenced. The two clones were the same size and showed complete homology. The WDV-Bg17 clone was compared with Barley dwarf virus, Oat dwarf virus and Wheat dwarf virus isolates. Based on DNA sequences WDV-Bg17 isolate shows high homology (95–97%) to Barley dwarf virus isolates and differs from Oat dwarf virus (71% homology) and Wheat dwarf virus (85% homology).

Trends in Political Communication in Hungary A Postcommunist Experience Twenty Years after the Fall of Dictatorship

The paper highlights the trends of political communications (PC) that have arisen in Hungary after the collapse of communist regime (1989). The authors have identified four main trends in the field of PC: fragmentation, the multiplication of PC channels and means, endless amount of PC arenas, Internet, Web 2.0, fragmentation of content, amateurism in PC; post-objectivity, the end of the requirement of unbiased and balanced coverage, more emphasis on the rise of opinion, on media as community focal point rather than window to the objective reality; the performative turn, the representation of self, a strong focus on act, dramaturgy, and aesthetics in PC; and popularization, the convergence of popular culture and politics, fan democracy, entertaining politics, involvement of citizens, etc.

Pace of life and behaviour: rapid development is linked with increased activity and voracity in the wolf spider Pardosa agrestis

Modern life history theory hypothesizes that pace of life is a strong predictor of life history traits. Recently, the notion that life history studies should integrate animal behaviour has emerged, because between-individual differences in behaviour are often coupled with fitness differences. So far, studies have mainly focused on interspecies or interpopulation perspectives, and research on the effects of life history differences on individual behaviour remain scarce. In the present study we aimed to contribute to the understanding of how pace of life is related to consistent individual behaviour. We investigated the relationship between developmental speed and consistent behaviour of the field wolf spider, Pardosa agrestis. In this species, individuals originating from the same clutch can typically follow either a slow or a rapid developmental pathway, characterized by a developmental time of about 10 or 3 months, respectively. We found that spiders, regardless of their developmental speed, behaved consistently in most of the tests. Our results also show that individuals developing rapidly were significantly more active during exploration and more successful in prey-catching tests than slowly developing spiders. Although rapidly developing spiders were bolder in one of the tests, this difference did not persist over the repeated measurements. Our work seems to support the notion that pace of life and animal personality are correlated, and pace of life might predict the behavioural types of individuals.

The rapid invasion of spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), in Hungary

SummaryThe invasive spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), native to South-East Asia, is a recent threat for fruit production of temperate zones worldwide. The fly was detected in 2008 for the first time in Europe (Italy and Spain) and four years later, in 2012, it was found in Hungary at a highway rest area. In this study, the results of a countrywide survey of D. suzukii in Hungarian highway rest areas in 2012–2014 are summarized and supplementary trapping results are also represented for three cities. In 2012 and 2013 the species was found only in low numbers and in a few sites in the western part of the country, while in 2014 an outbreak of D. suzukii populations was detected. Adult flies were found at most of the trapping sites all over the country. Additionally, they were also present in the three monitored cities. Our results show that D. suzukii has practically settled in the whole country in 2014.

Effect of weather conditions on cohort splitting in a wolf spider species

Abstract Cohort splitting has been described as differences in time until maturation and / or life span in the same age group. Cohort splitting generally occurs when individuals of a cohort originating from the same season experience different environmental conditions, such as in early and late progenies. However, in the wolf spider Pardosa agrestis (Westring, 1861) spiderlings of the same clutch may follow either slow or rapid development, leading to a second adult peak within a year comprised of the rapidly developing individuals. We hypothesized that weather conditions experienced by the spiderlings in their early ontogeny may contribute to a life history decision between slow and rapid development. To test this hypothesis, we have used long term collection data and non-parametric habitat modeling. We found that highest abundance of the rapidly developing phenotype was correlated with a narrow range of early weather conditions. This result is in accordance with our early choice hypothesis, although the possibility remains that differential survival of the developmental morphs also contributes to the observed pattern.