Chironomid community structure deduced from larvae and pupal exuviae of a chalk stream

Abstract

Species abundances of Chironomidae (Insecta: Diptera) have often been excluded from studies of benthic river communities because of difficulties associated with sampling and identifying larvae . Chironomid pupal exuviae are easier to collect and identify and could be used to determine community structure if shown to be representative of local larval assemblages . Larvae were sampled along a 20 m chain secured over mid-channel gravels, upstream of two collection points for pupal exuviae . Proportional taxa abundances of pupal exuviae and larvae sampled from 130 m of stream were directly compared by a x2 test of independence and also separately fitted to four models of species abundance distribution . Observed proportions of taxa were not independent of the life stage sampled . The greatest discrepancies occurred with species of pupal exuviae that were absent as larvae from the gravel . The log series model provided the best fit with both pupal and larval data . Collections of pupal exuviae had greater species richness and evenness than samples of larvae . This was considered to be a consequence of sampling larvae from the gravel habitat alone .

Importance of floodplain waters for the conservation of chironomid (Diptera) biodiversity in a 6thorder section of the Garonne river (France)

“…Some examples of this disparity are : Wilson & Bright (1973) took 200 exu viae in the River Rhine as well as Ruse (1993Ruse ( , 1995 in the Pang river. In the River Meuse, Kuijpers et al (1992) as well as Evrard (1996) identified 300 pupal exuviae whereas Frantzen (1992) in the Lower Rhone river and Gendron & Laville (1995) in a 4 th order sec tion of the River Aude, showed that 500 exuviae was best.…”

Species abundance distribution of benthic chironomids and other macroinvertebrates across different levels of pollution in streams

“…Using chironomids collected from a large river, Fesl (2002) reported that the observed communities did not fit the various niche-oriented models including the geometric series, whereas the distribution of functional feeding groups in chironomids fitted the random fraction model. In contrast, Ruse (1995) found that the abundance patterns of larval and pupal chironomids from a chalk stream were best described by a log series model. Alternatively, Dimitriadis and Cranston (2007) studied estuarial systems, where abundance patterns of chironomid communities fitted geometric series.…”

“…Futher research is required in checking how the subdivision pattern of niche will occur in aquatic conditions in this study. In fact, a wide variety of SAD models have been proposed including random fraction or assortment (Tokeshi, 1990(Tokeshi, , 1993(Tokeshi, , 1999Fesl, 2002), log series (Ruse, 1995), geometric series (Dimitriadis and Cranston, 2007). This indicated that chironomid communites would show diverse SAD patterns in adapting to competition for resources and for environmental disturbances at study sites.…”

“…(Saether, 1979;Resh and Jackson, 1993;Rosenberg, 1993;Barbour et al, 1996Barbour et al, , 1999De Bisthoven et al, 2005;Arimoro et al, 2007;Carew et al, 2007). Although some methods have been proposed for running waters (Schmid, 1992;Ruse, 1995;Lods-Crozet et al, 2001;Calle-Martinez and Casas, 2006;Rossaro et al, 2006), previous bioassessment methods based on chironomids were mostly developed for lentic ecosystems such as lakes or reservoirs (Saether, 1979;Wiederholm, 1980;Aagaard, 1986;Rossaro et al, 2007;Hamerlik and Bitusik, 2009). Species abundance patterns deserve special attention when dealing with the structural response of communities to disturbances.…”

“…Earlier studies on SADs in chironomids have considered the impact of different stream types, covering unpolluted (Schmid, 1992;Ruse, 1995), muskeg (Boerger, 1981) and estuarial (Dimitriadis and Cranston, 2007) ecosystems. Previous research has been also carried out at sites under stressful conditions subjected to organic pollution (Calle-Martinez and Casas, 2006), or sediment clogging (Carew et al, 2007) and river regulation (Penczak et al, 2006).…”