Ildikó Szivák

Diel flight behaviour and dispersal patterns of aquatic Coleoptera and Heteroptera species with special emphasis on the importance of seasons

Dispersal flight is the most important and almost the only way for primary aquatic insects to find new water habitats. During a 30-week-long project, we monitored the flight dispersal behaviour of aquatic beetles and bugs with using highly and horizontally polarizing agricultural black plastic sheets laid onto the ground. Based on the flight data of more than 45,000 individuals and 92 species, we explored and described eight different diel flight activity patterns. We found that seven of eight dispersal patterns are consistent with the previous knowledge, while three conspicuous mass dispersal periods can be identified as in the mid morning and/or around noon and/or at nightfall. As an exception, we found a ‘daytime’ pattern occurred exclusively in spring, in which mass dispersal can be seen from mid morning to late afternoon. In contrast to previous studies, we emphasize here that the seasonality has to be considered in evaluation of the diurnal flight activity. According to the seasons, a ‘three code sign’ was proposed to indicate the diel dispersal flight behaviour of a species for a year. Most of the species utilize different diel activity patterns in different seasons. In spring, the daytime pattern was the preferred type, but in summer and autumn, the evening types were the most popular patterns. We stated that the seasonal change of air temperature has a crucial role in that a pattern could be manifested in a given season or not and brings a need to change the diel dispersal pattern among seasons.

Chaetopteryx bucari sp. n., a new species from the Chaetopteryx rugulosa group from Croatia (Insecta, Trichoptera, Limnephilidae) with molecular, taxonomic and ecological notes on the group

Abstract We describe a new autumnal caddisfly species Chaetopteryx bucari sp. n. from 8 localities in the Banovina region of Croatia. We also present molecular, taxonomic and ecological notes (emergence, sex ratio and seasonal dynamics) on the new species and discuss the distribution of Chaetopteryx species in general and the Chaetopteryx rugulosa group in particular. Based on Bayesian phylogenetic analysis Chaetopteryx rugulosa schmidi was separated from the clade containing the other subspecies of Chaetopteryx rugulosa. Thus the subspecies Chaetopteryx rugulosa schmidi is here raised to species level, Chaetopteryx schmidi, as it was described originally. We further present distribution data on rare species in the genus Chaetopteryx in Croatia.

Are there any differences between taxa groups having distinct ecological traits based on their responses to environmental factors

The aim of this study was to explore the differences between taxa groups with different ecological strategies for persistence, regarding their responses to environmental factors and seasonal variation. We studied the relationship between the seasonal patterns and habitat attributes of the Ephemeroptera, Plecoptera, Trichoptera (EPT) and the Colepotera, Heteroptera (CH) assemblages. Sampling was carried out in May, July and October of 2009. Samples were taken according to the AQEM protocol at 10 stream sections in the Mecsek Mountains. Based on multivariate analyses (RDA, pRDA), distinctive differences were found between the EPT and the CH taxa groups regarding their response to local chemical variables and variables describing the riparian vegetation. The measured environmental variables had a higher relative influence on the distribution patterns of EPT and CH assemblages than spatial variation of species patterns. The physical structure of aquatic habitats, including the type of bedrock, had greater effects on CH than EPT patterns, whereas the structure of riparian vegetation was more important for EPT than CH. Average density and average taxon richness of EPT were seasonally variable, but CH assemblages were not.

Niche segregation between two closely similar gammarids (Peracarida, Amphipoda) — native vs. naturalized non-native species

Closely similar species may occupy similar niches, but usually divergence can be found in one or more traits when they inhabit the same habitat. In this study, we examined how two co-occurring gammarids — the native Gammarus fossarum and the naturalized G. roeselii — are distributed among microhabitats, depending on their sympatric or allopatric distribution. We hypothesized that the larger body-sized species (G. roeselii), exploiting their advantages in competition, restrict smaller species to microhabitats with smaller particle sizes. Four headwaters were sampled in the Mecsek Mountains (SW Hungary) in May, July and October 2009, and 37 local scale environmental variables at each site were measured. Although G. fossarum is smaller in size, significantly more individuals were collected from the more favourable lithal and biotic microhabitats, whereas a strong negative association was observed between the two species. Gammarus roeselii occurred at sites characterized by degraded riparian vegetation, which indicates stronger anthropogenic impacts, but still has a disadvantage in competition in mountainous streams under anthropogenic influence.

Genetic heterogeneity reveals on-going speciation and cryptic taxonomic diversity of stream-dwelling gudgeons (Teleostei, Cyprinidae) in the Middle Danubian hydrosystem (Hungary)

Although stream-dwelling gudgeons (Cyprinidae, genus: Gobio) are widespread in Central Europe, the taxonomy of this group and the distribution of its species are still unexplored in detail. The aims of our study are to ascertain taxonomic composition and distribution of the former Gobio gobio superspecies in the inner area of the Carpathian Basin. Since the presence of cryptic species is suspected in this area, we examined the taxonomic and phylogenetic relationships of Central European Gobio taxa by sequencing the mitochondrial DNA control region (mtCR). Additionally, we characterized the genetic structure of 27 stream-dwelling gudgeon populations of this area by Amplified Fragment Length Polymorphism (AFLP). Results of mtCR analysis proved the presence of three species already known as G. obtusirostris (dominant in NW-Hungary), G. gobio (sporadic) and G. carpathicus (sporadic). Additionally, the analysis revealed the existence of one doubtful taxon, G. sp1 (dominant in NE-Hungary), and a new isolated haplogroup (dominant in SW-Hungary). Although Network analysis showed significant detachment among haplogroups, their genetic distances were quite small. Therefore Bayesian phylogenetic analysis showed weak nodal support for the branching pattern both for newly described haplotypes, and for the already accepted species. AFLP data showed distinct population structure and a clear pattern of isolation was revealed by distance of stocks. At the same time, level of separation was not affected by the altitudinal position of sites. Moreover we found three major clusters of populations which were separated according to hydrographic regions, and corresponded to the findings of mtCR analysis. Our results suggest the on-going speciation of gudgeons in the Carpathian Basin, however the separation of haplogroups seems to only be an intermediate phase. The discovered natural pattern seems to be only slightly influenced by anthropogenic impacts. Additionally our results put into question the suitability of the recently accepted within Gobio genus taxonomy.

Variation of aquatic insect assemblages among seasons and microhabitats in Hungarian second-order streams

The assemblages of aquatic insects are important members of water ecosystems. Based on former studies among the most important factors structuring the assemblages are numerous abiotic ones, such as the sort and the particle size of the substratum. Most of the sampling protocols, e.g. AQEM, determine microhabitats based on those. Nevertheless, we have no information yet about whether or not these different, precisely determined microhabitats have different assemblages. In this study we compared the aquatic insect assemblages of different microhabitat types in three seasons using ADONIS and linear discriminant analyses. We proved that seasonal changes of abiotic factors had a major role in structuring the assemblages. In spring and summer the assemblages differed significantly, however, in autumn no significant differences were found. We supposed that the variation among the assemblages was due to the abundance patterns of frequent species instead of the presence of rare or sparse species. The indicator species analyses also corroborated this suppososition while symmetrical indicator species were not found.

Spatial distribution and diversity of chironomid assemblages in a small hilly stream (Diptera: Chironomidae)

In 2006–2007, spatial variations of chironomid assemblages of a small chalky watercourse were investigated in the hilly region of Balaton Upland, Hungary. Samplings were carried out every three weeks at seven characteristically different sites along the whole length of the watercourse. Altogether 2966 specimens were collected and identified. The chironomid fauna of the stream was relatively rich with 40 taxa belonging to four subfamilies (eight Tanypodinae, one Prodiamesinae, 17 Orthocladiinae, 14 Chironominae). The lowest number of species and number of individuals was found at the spring, and the highest at the middle reach. Based on multivariate analysis the different sections of the creek were characterised by distinctive chironomid communities. Although longitudinal changes in the chironomid community of the Örvényesi creek were detectable due to changes in natural environmental factors, land-use changes also significantly influenced the chironomid community composition and diversity. The natural and anthropogenic effects were hardly distinguishable. Furthermore, we found that the response of different diversity indices to environmental variability was different. This draws attention to the difficulties in evaluating the relationships between stream communities and environmental variables using different diversity indices. The taxonomic diversity, which incorporates the taxonomical relationships between the specimens, proved to be one of the most useful diversity indices to characterise the stream chironomid assemblages.

Highly variable abiotic environment induced changes in taxonomic and functional composition of headwater chironomid assemblages within a small mountain range

The spatial variability of Chironomidae larvae assemblages was investigated at 6 near-pristine, temperate headwaters in Hungary. Sites were located within a relatively small mountain range but belong to two different catchment areas characterized by highly variable abiotic conditions. We hypothesised there would be differences in taxonomic composition but not in functional composition between different catchment areas and aimed to assess the primary influencing spatial factors structuring the taxonomic and functional compositions of chironomid assemblages. The spatial distribution of chironomid assemblages was examined 4 times during a 1 year period at microhabitat to catchment scales. At each site, streambed morphology, physicochemical attribute, riparian vegetation, microclimate and hydrology data were collected. Three main traits (saprobic preference, stream zonation preference, functional feeding groups) were used to characterize the functional composition of chironomid assemblages. Sharp differences were detected in taxonomic composition between the two sides of the mountain range within a relatively small spatial distance and moderate, but statistically significant differences in functional composition between catchments. The observed spatial changes in taxonomic and functional composition of midges accompanied changes in physicochemical characteristics, riparian vegetation, microclimate and altitude. Internal microhabitat heterogeneity also played a major role in structuring the taxonomic and the functional patterns of chironomid assemblages.

Ecological divergence of Chaetopteryx rugulosa species complex (Insecta, Trichoptera) linked to climatic niche diversification

Climate is often considered to be an important, but indirect driver of speciation. Indeed, environmental factors may contribute to the formation of biodiversity, but to date this crucial relationship remains largely unexplored. Here we investigate the possible role of climate, geological factors, and biogeographical processes in the formation of a freshwater insect species group, the Chaetopteryx rugulosa species complex (Trichoptera) in the Western Balkans. We used multi-locus DNA sequence data to establish a dated phylogenetic hypothesis for the group. The comparison of the dated phylogeny with the geological history of the Western Balkans shows that lineage formation coincided with major past Earth surface and climatic events in the region. By reconstructing present-day habitat conditions (climate, bedrock geology), we show that the lineages of C. rugulosa species complex have distinct climatic but not bedrock geological niches. Without exception, all splits associated with Pliocene/Pleistocene transition led to independent, parallel split into ‘warm’ and ‘cold’ sister lineages. This indicates a non-random diversification on the C. rugulosa species complex associated with late Pliocene climate in the region. We interpreted the results as the diversification of the species complex were mainly driven by ecological diversification linked to past climate change, along with geographical isolation.