Diptera) in a Wetland Habitat and Their Potential Role As Bioindicators
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Cent. Eur. J. Biol. • 6(1) • 2011 • 118–129 DOI: 10.2478/s11535-010-0098-x Central European Journal of Biology Ecology of Dolichopodidae (Diptera) in a wetland habitat and their potential role as bioindicators Research Article Ivan Gelbič*, Jiří Olejníček Biological Centre of Czech Academy of Sciences, Institute of Entomology, CZ 370 05 České Budějovice, Czech Republic Received 28 April 2010; Accepted 06 September 2010 Abstract: Ecologicalinvestigationsoflong-leggedflies(Dolichopodidae)werecarriedoutinwetmeadowwetlandsnearČeskéBudějovice, Czech Republic. Sampling was performed during the adult flies’ seasonal activity (March-October) in 2002, 2003 and 2004 using yellow pan traps, Malaise traps, emergence traps, and by sweeping. Altogether 5,697 specimens of 78 species of Dolichopodidae were collected, identified and analysed. The study examined community structure, species abundance, and diversity(Shannon-Weaver’sindex-H’;Sheldon’sequitabilityindex-E).Chrysotus cilipes,C. gramineus and Dolichopus ungulatus were the most abundant species in all three years. Species richness and diversity seem strongly affected by soil moisture. Keywords: Long-legged Flies • Ecology • Conservation • Bioindication ©VersitaSp.zo.o. usually do not fly too far from their breeding places, 1. Introduction which is convenient for their use as bioindicators. The Dolichopodid flies represent a good model for the study aims of this paper are (i) to extend our knowledge on of bioindication because they meet all necessary criteria the community structure of dolichopodid fauna and for this role [1]. Pollet has indicated four such criteria: (ii) to explore possibilities for the use of these insects as 1) easy determination of species, 2) a taxonomic bio-indicators. group comprised of a sufficient number of species, 3) satisfactory knowledge about ecology/biology of the species, and 4) species should reveal specific ecological 2. Experimental Procedures requirements [2]. North Central Europe, roughly delimited by 5–20° E 2.1 Study area and 45–55° N, has been the subject of numerous The study was carried out during 2002–2004, inclusive, at studies that have provided basic information about Švábův Hrádek near České Budějovice, Czech Republic habitat evaluation for Dolichopodidae [3-22]. Most of (Figure 1) (48°58’26.84” N, 14°25’55.93” E). The sampling these studies relate to Belgium, Czech Republic and site represents a mosaic of different landscape elements, Germany. Other studies, however, have also reported on with a wetland of less than 0.1 km2 with wet meadows, two the dipteran fauna (Nematocera: Limoniidae; Tipulidae; small permanent pools of about 25 and 300 m2 (the latter Trichoceridae; Brachycera: Empididae; Hybotidae; one is actually a chain of several connected smaller pools Dolichopodidae) in other parts of the region [23-29] and with alders, birches and oaks on their banks), and several are important in this respect. old fruit trees adjacent to the wet meadows. The sampling Larvae and adults of the dolichopodid flies are site is immediately surrounded by intensively farmed land predators [29,30] that can be found in all wet biotopes. bordering coniferous forest (mixed spruce and pine). The Larvae are mostly aquatic or semi-aquatic. Adults wetland is situated in the lower part of a former open-cast * E-mail: [email protected] 118 I. Gelbič, J. Olejníček pit for extracting clay used in bricks manufacturing, but has 2. Emergence traps (ET): Six ETs (metal construction not been in production for about the past 50 years. The of conical shape covered by black waterproof serge) upper part of the pit (outside the study location) was used were placed at various locations in the wet meadows as dump for communal refuse. Our monitoring was initiated and at the pool edges, two of them standing just in 10 years after this activity ceased. The dump was thinly shallow water (littoral) near the pool bank [10]. The covered with soil and overgrown by self-seeding plants. traps covered 0.25 m2 and the collected insects were In 2003, the entire dump was “reclaimed” by elimination trapped in a bottle containing 75% ethyl alcohol which of herbage and adding a 50 cm layer of clay followed by was emptied every two weeks. a layer of soil of the same thickness and then sown with 3. Sweeping: For an additional sampling method, we grass. This decreased the level of pool water by about used sweep nets once each month (50 sweeps linearly 50 cm and caused partial desiccation of the wet meadows for 20 min of continuously sweeping). in 2003 and 2004. Climatic data for all dates 2002 to 2004 4. Malaise traps (MT): Two MTs, each controlled were obtained from the hydro-meteorological station every two weeks, were used and the material was in České Budějovice, which is part of a meteorological collected in 75% alcohol. monitoring network. 2.3 Material processing, identification and 2.2 Sampling statistical analysis During 2002 to 2004, from March to October, Preservation and mounting: individual specimens were Dolichopodid flies were collected in the above site using dried prior to identification. Flies preserved in alcohol the following sampling strategy: were dried by: 1) transferring from alcohol to an alcohol- 1. Yellow pan traps (YT): Thirty plastic rectangular formaldehyde mixture; 2) transferring to alcohol-diethyl dishes (size 10x7x4cm), each containing 1% of ether mixture; then 3) transferring to diethyl ether, the formaldehyde solution with a few drops of the detergent evaporation of which left the material dried. Dried flies Lena natur®, were distributed linearly (with 5 m distances were mounted on triangular paper labels. between two neighbouring dishes) at the investigated Several monographs were used for identification locality. YTs were in operation for one day per week and [34-47]. The relative abundance (%) of each species yields were transferred to and stored in 75% ethanol. was calculated separately for each year of the three-year According to Pollet and Grootaert [32] and Barták [33], study. The following scale of dominance was used: more yellow pan traps are the most effective collecting method than 10% of total number of Dolichopodidae caught per for the majority of species of the family Dolichopodidae studied year was regarded as eudominant (ED), 5–10% although the traps are less suitable for the primarily dominant (D), 2–5% subdominant (SD), 1–2% recedent arboreal subfamily Medeterinae. (R) and less than 1% subrecedent (SR). The Shannon- Figure 1. Picture of the studied locality (part of a wet meadow with pools). 119 Ecology of Dolichopodidae (Diptera) in a wetland habitat and their potential role as bioindicators Weaver diversity index (H’) and equitability index On the other hand, analysis of the sex ratio shows the (E) were monitored for each year. A linear regression greatest disproportion in the genera Chrysotus and was fitted to a linear model to determine relationships Sybistroma. In species of the genera Chrysotus and between the size of the studied area and biodiversity. Sybistroma males predominated over females. Just the reverse was true in P. nobilitatus. Moreover, the degree of sexual disproportion rose with increasing level of 3. Results and Discussion dominancy (compare Figure 2 with Table 1). 3.1 General results and sex ratio 3.2 Community structure The total number of dolichopodid specimens collected Semi aquatic localities are typical for most species of during 2002–2004 was 5,697 (3,700, 1,659 and 338 the Dolichopodidae, and specimens of this family often in 2002, 2003 and 2004, respectively). The taxonomic represent the most frequent captures in samples from representation encompassed 18 genera and 78 species such biotopes. (57 species in 2002, 48 species in 2003 and 37 species Table 1 shows the total number of individuals of in 2004; see Table 1). Most of this material was obtained each species captured, their relative abundance (%), using the yellow water trap method. Only three species and the classification of dominancy. Only three species (Achalcus cinereus, Medetera apicalis, and Syntormon – Chrysotus cilipes, Ch. gramineus and Dolichopus bicolorellum) were collected by a different method – the ungulatus – were consistently dominant or eudominant emergence traps. Yellow water traps were most effective in all three years, but none of these species was itself in catching males (Figure 2). This is consistent with the eudominant for all three years. Dolichopus latilimbatus, observations of Pollet and Grootaert [10] who noted that D. plumipes, Poecilobothrus nobilitatus and Poecilobothrus in-water traps located on the soil surface, the frequency chrysozygos were dominant or eudominant for one year of males is higher than in traps at 25 cm height. Figure 2 only. An unexpectedly large number of species for such presents the percentages for species that were at least a small locality was detected during the first year of subdominant in at least one of the monitored years. Sex monitoring, although there was a decrease in individual ratio is generally close to 1:1, and this was shown in and species abundance after drainage of the locality the majority of investigated species of Dolichopodidae. caused partial drying of the wetland. 89% 90 84% 90 83% ♂ 78% 80% ♂ ♂ ♂ ♂ 70 66% 67% 70 61% 63% ♂ 58% ♂ ♂ ♂ 52% ♂ 47% 50 45% ♂ 50 ♂ ♂ 39% ♂ 30 30 10 10 Ch. angulicornis Ch. cilipes Ch. cupreus Ch. gramineus Ch. neglectus festivus D. D. latilimbatus D. plumipes D. trivialis D. ungulatus H. chrysozygos N. nodicornis P. nobilitatus zetterstedti R. ♂