Correspondence Between Larval Development and Adult Residence

Latvijas entomologs 2007, 44: 109-118. 109 Correspondence Between Larval Development and Adult Residence Habitats of Dolichopodid Flies (Diptera, Empidoidea: Dolichopodidae) in a Heterogeneous Mosaic of Seacoast Grassland Habitats 1, 2 KRISTAPS VILKS 1 Department of Zoology and Animal Ecology, Faculty of Biology, University of Latvia, 4 Kronvalda Blvd., LV-1586 Rga, Latvia; e-mail: [email protected] 2 Institute of Biology, University of Latvia, 3 Miera Str., LV-2169 Salaspils, Latvia VILKS K. 2007. CORRESPONDENCE BETWEEN LARVAL DEVELOPMENT AND ADULT RESIDENCE HABITATS OF DOLICHOPODID FLIES (DIPTERA, EMPIDOIDEA: DOLICHOPODIDAE) IN A HETEROGENEOUS MOSAIC OF SEACOAST GRASSLAND HABITATS. – Latvijas entomologs, 44: 109-118. Abstract: Spatial distribution of dolichopodid adults and larvae was investigated in a heterogeneous mosaic of seacoast habitats in the Lake Engure Nature Park (Latvia) in July 2006. The patchy coastal landscape was dominated by dry dune grasslands, wet seacoast grasslands and reed beds. Larval development habitats were determined by using soil emergence traps, while the flight activity of adult flies was examined by yellow water traps. In total, 30 dolichopodid species were recorded. The most abundant species were Dolichopus nubilus, D. notatus, Teuchophorus spinigerellus, Sympucnus pulicarius, Dolichopus acuticornis, D. pennatus, D. plumipes and Sciapus maritimus. There were much higher species richness and abundance for adult flies flying above the ground in comparison with those species emerging from soils. In general, dolichopodids were more abundant in humid habitats. Flying adult dolichopodids concentrated in reed beds, while their emergence activity, representing larval development habitats, was significantly higher in wet seacoast grasslands. Thus, habitats of larval development did not correspond to adult residence habitats. The article discusses several alternative explanations for such spatial distribution of different development stages. Behavioural aspects seem to be the most important for the habitat selection of adult flies. In conclusion, this study shows that dolichopodid flies may require a highly heterogeneous environment during their life cycle. Key words: Adult flight activity, Diptera, Dolichopodidae, Empidoidea, larval development, Latvia, migration, seacoast. Introduction species (Frouz 1999). There is an urgent need to improve our knowledge on the spatial There is no doubt, that insects are the distribution of different development stages of most species-rich animal group in any terrestrial dipterans in the context of biodiversity research environment (Steffan-Dewenter, Tscharntke and bioindication. If dipteran species depend on 2002), and that they make up most of the different habitats during their life cycle, this biodiversity in the world (Speight et al. 1999). should take into account planning the Dipterans have been recorded as one of the conservation of endangered and rare dipteran largest insect order (Speight et al. 1999, Frouz species or communities. Further, species 1999), and they clearly dominate in a wide showing multi-habitat use should indicate fine- range of terrestrial habitats (Melecis et al. scale habitat or landscape heterogeneity and 1999), representing an important component of could be used as bioindicators of habitat quality soil and grass-dwelling faunas (Frouz 1999). and diversity. Despite of this, dipterans still belong to The subject of the present study is the least investigated animals, mainly due to dolichopodid flies occurring in a highly taxonomical and methodological difficulties complex seacoast landscape. Dolichopodids (Frouz 1999, Hövemeyer 2000). Furthermore, represent a diverse and species-rich dipteran the majority of ecological studies related to group worldwide (Grichanov 2006), and dipterans considers the adult stage only, and heterogeneous mosaic of clearly different thus obtains only simplified knowledge on the coastal habitats was used as a model ecosystem, actual diversity and distribution of different allowing studying small-scale distribution of 110 Correspondence Between Larval Development and Adult Residence Habitats… species. Reed beds and less frequently adjacent There are two main aims for the present lower situated grasslands were regularly study: to determine dolichopodid larval overflooded during high level of seawater. Dry development sites (1), and to try to answer the dune grasslands were formed by scarce question, weather dolichopodid larval vegetation dominated by Festuca rubra, Leymus development habitats correspond with habitats arenarius and Achilea millefolium and by dense preferred by the adult flies (2). layer of mosses, however some patches of bare sandy ground were also present. A dense Methods vegetation of Juncus gerardii, Lathyrus Study area palustris, Galium palustre dominated wet seacoast grasslands and Elytrigia repens, and This study was performed in the territory patches of dense grass litter were frequently of the Lake Engure Nature Park (Western present in this habitat. Both dry and wet Latvia) near the village Mrsrags. Two grasslands were slowly overgrown with sampling plots (plot A: 57°19.481Ń, common reed Phragmites australis, as habitat 23°08.249É and plot B: 57°19.461Ń, management in the investigated site has not 23°08.265É) (~30x30 m) were selected within been carried out for at least ten years. Reed beds a heterogeneous mosaic of coastal habitats were strongly dominated by a tall vegetation of composed of patches of dry dune grasslands and common reeds, although Galium palustre was wet seacoast grasslands as well reed beds in the also relatively abundant. depressions of microrelief (Fig.1). Figure 1. Scheme of the investigated sampling plots situated in a heterogeneous mosaic of three coastal habitats in the Lake Engure Nature Park (Western Latvia) and location of emergence and water traps. Sampling and identification order to decrease surface tension. Water traps were placed on the ground or 5-10 cm above Aerial activity of flying adult ground attached to piles of wood within dolichopodids was registrated by using yellow inundated reed beds as such locations allow to water traps (diameter 12 cm, depth 6 cm), which collect the highest numbers of dolichopodid have been previously recorded as an excellent species as shown by Pollet and Grootaert method for the investigation of dipteran (1994). In dense vegetation, the surrounding communities (Pollet, Grootaert 1999, De Bruyn plants were cut off at distance of 10 cm around et al. 2001). All water traps were filled at two- the water traps. thirds with a 4% formaldehyde solution to Larval distribution pattern was assessed which a few drops of detergent was added in using soil emergence traps (basal area 0.25 m2, Latvijas entomologs 2007, 44: 109-118. 111 height 50 cm), which registrate freshly emerged adults of dolichopodids from soils in such a way Data analysis allowing to detect their breeding sites. Prior to placing of the emergence traps, all vegetation in Non-parametric Kruskal-Wallis H test was the basal area of traps was cut off. In order to performed for testing differences in species obtain an effective isolation, lower margins of richness and abundance among investigated emergence traps were digged in the soil at the habitats. If significant differences were found, deep of 10 cm. Sampling bottles at the tips of non-parametric Mann-Whitney U test was used emergence traps were filled with a 4% then for the pairwise comparisons of variables. formaledhyde solution to which a few drops of Differences in the proportions were examined detergent was added. In each habitat type, six using the 2-test (Sokal, Rohlf 1995). Detailed water traps and six emergence traps were analyses for individual species were performed installed. Traps were placed with a minimum for those species only, representing 30 or more distance of 5 m from each other. individuals in the total catch. All statistical Dolichopodids were collected in July of analyses were performed using SPSS 15.0 for 2006. This period of season was selected, while, Microsoft Windows® software. according to my previous investigations (unpublished data), the majority of species Results shows the highest adult activity in July. The Dolichopodid emergence from soils materials from traps were emptied two times per investigation period. In total, 13 species with 87 individuals In the laboratory, dolichopodids were were caught with soil emergence traps (Table sorted and stored in 70% alcohol. Identification 1). Despite of low numbers of emerging was performed by means of the keys compiled individuals, the calculated mean abundance per by Grichanov (2006), Meuffels and Grootaert area was quite high, at least in the patches of (1990), Negrobov and Stackelberg (1969) and wet meadows (37 ind./m2). Dolichopus nubilus Pollet (1990, 1996). Nomenclature follows (39%), Teuchophorus spinigerellus (14%), Grichanov (2006). The materials of the sampled Achalcus vaillanti (8%), Dolichopus plumipes dolichopodids are deposited within the (8%) and D. popularis (7%) were the most collection of the Faculty of Biology of the abundant species. Latvian University (Rga). Table 1. Summary of dolichopodid species collected with water traps and emergence traps in a heterogeneous mosaic of three coastal habitats in July of 2006. Abbreviations: I – reed beds, II - wet seacoast grasslands, III – dry dune grasslands. Water traps Emergence traps Species I II III Total I II III Total Achalcus vaillanti BRUNHES, 1987 3 3 0 6

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