Csaba Szinetár

ON THE NATURE OF AGROBIONT SPIDERS

Abstract Results from a 10 year survey of spiders in Hungarian arable and natural grassland habitats are cumulated in order to reveal the key characteristics of agrobiont species. We define agrobionts as species that reach high dominance in agroecosystems. The most dominant species, Pardosa agrestis, on average accounted for 40% of the total spider population in Hungarian arable fields. The presence of agrobionts led to a strong skew in arable spider community species distriibution. Regardless of the over-dominance by agrobionts, arable spider communities had a potential for very high species richness. The agrobiont segment of arable spider communities showed very little field-to-field or regional variation, i.e. the same agrobiont species occurred in all fields. Agrobionts were indicators of arable habitats, and were rare in other habitat types, but in many species preferences for specific natural habitat types could be shown. These natural habitat types were often strongly abiotically driven, frequently disturbed habitats. The life cycle of agrobionts showed synchronization with the arable crop-growing season. While many closely related non-agrobiont species had maturity and reproductive periods either earlier or later than the main crop vegetation period, agrobionts invariably reached adulthood and reproduced during that period. Association with frequently disturbed natural habitats and phenological synchronization with the annual arable disturbance regime are such traits that support the theory that agrobiont species are adapted to predictably ephemeral habitats.

Large and least isolated fragments preserve habitat specialist spiders best in dry sandy grasslands in Hungary

The role of fragment size, isolation and habitat diversity in the conservation of spider assemblages living in fragmented landscape were studied in dry sandy grasslands (East Hungary, Nyírség). Spiders were collected using pitfall traps at eight dry grassland fragments from 2001 to 2009 from March to October fortnightly. We tested the rules of island biogeography, which suggest that the species richness increases with the size and decreases with the isolation of fragments. The habitat diversity is an important factor for species richness, since large areas usually have more habitats; therefore, the number of species may be higher in these areas. During the 9-year study period, altogether 10,544 individuals belonging to 106 species were collected. Contradicting the classical theory, we found a significant negative relationship between the total number of spider species and the grassland size, while the ratio of sandy grassland specialist spider species increased with fragment size. The relationship between the ratio of generalist species and the fragment size was not significant. The overall species richness and the isolation of studied grasslands did not show a significant relationship. The ratio of sandy grassland specialist species decreased, while the ratio of generalist species increased with the increasing of isolation. The habitat diversity did not show any effect on spider species richness. We concluded that to conserve the habitat specialist species it is recommended to preserve the large and least isolated grassland fragments, furthermore to increase the size of small fragments with the restoration of the adjacent croplands.

Effects of immission load on spiders living on black pine

The effects of immission load on spiders living on black pine (Pinus nigra Arnold) were studied in a town in Western Hungary. In three sampling periods, trunk-trap catches of spiders from black pine trees planted in a control urban area were compared with those from black pines planted in an area with high immission load. In the first two sampling periods – when apart from the exclusive dwellers on or under bark of the black pine, foliage-dwelling spiders overwintering under the bark (facultative bark-dwellers) could also be trapped – the species richness and the Shannon diversity were significantly higher in the control area than in the area highly affected by immission. In these sampling periods, the composition of spider assemblages also significantly differed in the studied areas. In the third sampling period – when only the exclusive bark-dwellers could be trapped because facultative bark-dwelling spiders returned to the foliage after the overwintering – the species richness, Shannon diversity and the composition of spider assemblages were similar in the differently affected areas. Our results suggest that spiders living exclusively on or under the bark are not significantly influenced by immission load, while foliage-dwellers are sensitive to immission. Indicator species analysis also proved the clear classification of the responses of spiders to immission load. The probable direct and indirect effects of immission, causing differences in the species richness, diversity and the composition of spider assemblages, are also discussed.

Intensive grazing opens spider assemblage to invasion by disturbance-tolerant species

Abstract Grazing is an established conservation tool for maintaining grassland habitats and under some circumstances may enrich arthropod assemblages. However, even if enrichment occurs, it is not granted that conservation value signified by rare and specialist species will also increase. To assess how some preset levels of grazing suit conservation aims, we studied spider assemblages of ungrazed, sparsely grazed and intensively grazed areas of a pasture in Hungary for three years by pitfall trapping and suction sampling. At ground level there was no significant difference among grazing areas, while at higher strata increasing grazing intensity negatively affected number of individuals and species. C-score analysis indicated equally neutral community assembly in all three grazing areas. All statistical methods that took into account species identity indicated virtually no difference between the spider assemblages of the sparsely grazed and ungrazed areas; however, there was a marked difference between these and the intensively grazed area. Spider species in the intensive grazing area had significantly lower affinity but wider tolerance for habitat naturalness, preferred more open habitats and had a lower rarity status. In the intensive grazing area a number of disturbance-tolerant species, among them agrobionts, were present, whereas the exclusion of rare or specialist species in the intensively grazed area occurred infrequently. The primary effect seen at the intensive grazing area was the opening of the spider assemblage to disturbance-tolerant species, while species richness was likely maintained by neighboring source populations. Overall, we experienced a marked decrease in the naturalness status of the spider assemblage in the intensive grazing area.

Rare Species Indicate Ecological Integrity: An Example of an Urban Nature Reserve Island

Ecological integrity is a complex notion referring to the quality of an ecological system. Wild ecosystems are considered to possess complete ecological integrity. Undisturbed by humans, such ecosystems follow their natural path of succession and evolution. If perturbed, they have a high capacity to return to this path (Westra & Lemons, 1995).

DATA ON THE BIOLOGY OF ALOPECOSA PSAMMOPHILA BUCHAR 2001 (ARANEAE, LYCOSIDAE)

Abstract This paper presents electron micrographs of the genitalia of Alopecosa psammophila, describes the morphological characteristics of the species and also gives information on its habitat preference, the co-occurring ground-dwelling spiders, and the phenological characteristics of the species. Barber pitfall trappings have been carried out since 2000 in dry sandy grasslands in three regions of Hungary: the Kiskunság area (Kiskunság National Park); the Nyírség area (Hortobágy National Park); and since 2004 the Kisalföld area (Fertő-Hanság National Park). Specimens of the species, hitherto unknown in Hungary, have been collected from 17 localities in all three areas. We collected specimens in calciferous open sand steppes and in acidic open sand steppes. In the females, two activity periods were apparent (from April to end July and in October). A few males were collected in April and in October–November they had an extreme activity peak. We assume that the species has adult specimens throughout the winter. Alopecosa psammophila is most similar to Xysticus ninni Thorell, 1872 and Zelotes longipes (L. Koch 1866) in terms of its environmental needs.

CERATOTHOA RETUSA (SCHIŒDTE & MEINERT, 1883) (ISOPODA, CYMOTHOIDAE), A VARIABLE SPECIES OF FISH PARASITIC MARINE ISOPOD FROM THE INDIAN OCEAN

Ceratothoa retusa (Schiœdte & Meinert, 1883) is redescribed from the lectotype (here designated) collected from Mozambique, and the range is extended to include the Gulf of Suez in the Red Sea. Ceratothoa retusa is distinctive within the genus with a manifestly small head deeply immersed into pereonite 1, which has prominent, but variable, projecting anterolateral margins. Ceratothoa retusa has a tropical and subtropical Indian Ocean distribution, extending from eastern Africa (and now the Red Sea) eastwards to northern Australia and Indonesia. The only known hosts are the halfbeaks, Hemiramphus far (Forsskal, 1775) and H. robustus Gunther, 1866 (Hemiraphidae).

On the identity of the Palearctic species of the wolf spider genus Trebacosa (Araneae: Lycosidae)

In this paper we propose Trebacosa brunhesi Villepoux, 2007 as a junior synonym of Trebacosa europaea Szinetár & Kan-csal, 2007 based on the examination of specimens from all the localities from where those species are known. Illustration of the type species of the genus, Trebacosa marxi (Stone, 1890) and specimens from all known localities of T. europaea are given to show both the inter- and the intraspecific differences of the genus. Scanning electron micrographs were used to illustrate the detailed structure of the females genitalia.