Implications of anthropogenic disturbance factors on the Odonata assemblage in a Mediterranean fluvial system

Abstract

During a period of nine years, from 2000 to 2008, two consecutive studies-one focusing on observations of adult Odonata, the other on collection of larvae-were carried out in the basin of the Guadiamar River in the southwestern Iberian Peninsula. In addition to monitoring Odonata, several environmental variables were assessed, including an index based on macroinvertebrate communities (IBMWP). In April 1998, this river system suffered from an accidental release of a large mass of toxic mining waste, which exterminated macroinvertebrates in the middle and lower parts and floodplain. Several years later, dragonfly communities in these areas were similar to those of unaffected upper reaches. Communities of sites less affected by general human impact were dominated by semivoltine anisopterans. In contrast, headwaters and river reaches where riparian forest had been destroyed many years ago and seasonality of river discharge was boosted by landscape management harboured chiefly uni-or bivoltine species, regardless whether a site had been affected by mining waste or not. Species assemblage was especially poor in lower river reaches that experienced permanent, diffuse urban and agricultural pollution. A few partivoltine species were recorded, but only in habitats with a high IBMWP index. It seems that over the long term, Odonata respond more to land use and catchment management than other groups included in the IBMWP index.

Dragonflies and damselflies (Odonata) in urban ecosystems: A review

“…In these cases, diversity was negatively related to sewage input (Solimini et al, 1997;Henriques-de-Oliveira et al, 2007), although most of the papers from the search were focused on aquatic macroinvertebrates and the overall group of odonates as bioindicators rather than particular species. Urban pollution was associated with increased abundance and dominance of Libellulidae and other taxa (see Table 2), but decreased abundance of Gomphidae (Ferreras-Romero et al, 2009) and overall evenness (Henriques-de-Oliveira et al, 2007). However, it is worth mentioning that even though there are many tolerant species within Libellulidae and sensitive species in Gomphidae (Ferreras-Romero et al, 2009), the sensitivity or tolerance of a stressor depends on the particular species rather than a larger taxon, therefore caution must be taken when considering libellulids or gomphids as bioindicators.…”

“…Dragonfl ies and damselfl ies (the Odonata) are highly suitable model organisms for the study of urban ecosystems because (a) they are sensitive to different stressors, such as pollutants (Ferreras-Romero et al, 2009) and temperature changes (Hassall & Thompson, 2008), therefore can be a powerful tool to assess the general conditions of the city environment; (b) they are aquatic as larvae and terrestrial as adults, hence can be used as bioindicators in both aquatic and terrestrial habitats (Oertli, 2008); (c) they have an important role as predators, hence have a wide range of interactions with different organisms in both aquatic and terrestrial ecosystems (Knight et al, 2005); (d) they are ideal for studying movement through the landscape, as their adult stage exhibits a high dispersal ability and are very conspicuous (Conrad et al, 1999), and (e) their biodiversity, ecology and evolutionary biology is well-documented, providing a robust foundation for drawing general conclusions (Córdoba-Aguilar, 2008).…”

Dragonflies (Insecta: Odonata) as indicators of habitat quality in Mediterranean streams and rivers in the province of Barcelona (Catalonia, Iberian Peninsula)

“…However, some authors point out that this type of assessment has some limitations: their application is relatively expensive and restricted to specialists and does not provide information at the species level. Besides, aquatic macroinvertebrates are rather more responsive to water quality than to changes in the general structure of the riparian habitat (Smith, Samways, & Taylor, 2006) and on that account they may not completely reflect the latter's overall conservation status (Ferreras- Romero et al, 2009;Simaika & Samways, 2011).…”

“…They have few generations per year, show high sensitivity to early changes in their environment, respond quickly to them and provide continuous information about the damage caused by the alterations, both in the larval (Ferreras-Romero, Márquez-Rodríguez, & Ruíz-García, 2009;Gómez-Anaya, 2008;Watson, Arthington, & Conrick, 1982) and the adult stage (Müller et al, 2003;Samways & Steytler, 1996;Torralba Burrial, 2009). …”

The Gomphidae of Algeria and the Maghreb: status, ecology and conservation (Insecta: Odonata)

“…Dragonfly larvae are relatively large obligate predators which may have a considerable impact on community structure of freshwater ecosystems (Woodward & Hildrew, 2001. Among Odonata, gomphids are an important component of the biota of running waters and their numbers and diversity are considered a reliable indicator of a healthy fluvial system (Ferreras-Romero, Márquez-Rodriguez, & Ruiz-Garcia, 2009). The need to update our knowledge of the Gomphidae of Algeria is clear as some species have not been recorded since the nineteenth or early twentieth centuries.…”