Abstract
This study aimed to examine spatiotemporal variations in chironomid assemblages and to detect how environmental variables affect their structure. We sampled seven streams at low and high altitudes in Northwest Argentina under contrasting climate conditions (Puna and Chaco Serrano) during high- and low-water periods. The environmental variables that affected Chironomidae community structure were water temperature, conductivity, hardness, current velocity and type of substrate. Fine substrates, gravel and low water temperature favoured cold stenothermal fauna, composed of Orthocladiinae, Diamesinae and Podonominae specimens in the high-altitude streams, whereas warm waters with low conductivity and higher velocity favoured increased species diversity in lowland streams, where there was greater abundance of Chironominae (which corresponds to warm eurythermal fauna). The studied environments belong to a transition zone that should be preserved where cold stenothermic and warm eurythermal Chironomidae overlap.
Highlights
Spatiotemporal variations in Chironomidae (Diptera) assemblages have been used to assess the trophic status of rivers (Fend & Carter 1995, Paggi 2009) and examined (Jacobsen et al 1997, Lencioni & Rossaro 2005, Acosta & Prat 2010) in order to further understand the ecological functioning of rivers and biological interactions with the environment (Allan & Castillo 2007)
The variables that affect microdistribution (Lencioni & Rossaro 2005) are: current velocity (Lindegaard & Brodersen 1995), which determines substrate composition (Ruse 1992, Wantzen & Rueda Delgado 2009); type of substrate (Ruse 1994, Sanseverino & Nessimian 2001, Hepp et al 2012); water temperature (Maiolini & Lencioni 2001), which determines the distribution of Chironomidae species (Tokeshy 1995) and differences among cold stenothermal and warm eurythermal species (Cranston 1995); altitude (Lencioni et al 2007, Scheibler et al 2014); phosphorus and nitrate concentrations (Ramírez & Pringle 2006, García & Añón Suarez 2007); food resource availability (Tokeshy 1995), which is limited by temperature and velocity (Cranston 1995, Lindegaard & Brodersen 1995); the presence of macrophytes, which favours feeding and environmental aeration and contributes to the formation of refuges to avoid
We selected diverse streams located in the Puna and Chaco Serrano ecoregions (Cabrera 1971)
Summary
Spatiotemporal variations in Chironomidae (Diptera) assemblages have been used to assess the trophic status of rivers (Fend & Carter 1995, Paggi 2009) and examined (Jacobsen et al 1997, Lencioni & Rossaro 2005, Acosta & Prat 2010) in order to further understand the ecological functioning of rivers and biological interactions with the environment (Allan & Castillo 2007).The study of the Chironomidae family is important at taxonomic and ecological levels due primarily to the great density and diversity they exhibit in disparate aquatic ecosystems, as well as their great plasticity to adapt to different environmental conditions. Changes in the Chironomidae community structure have been documented for different mountain aquatic systems (Lods-Crozet et al 2001, Medina & Paggi 2004, Acosta & Prat 2010, Tejerina & Malizia 2012, Robinson et al 2016, Hamerlík et al 2017). We selected seven streams with contrasting environmental conditions, due to their differences in climate and altitude, that belong to the Puna and Chaco Serrano ecoregions. The lower aquatic systems are embedded in mountain valleys at between 700 and 2000 m elevation and belong to the dry Western Chaco subtropical forest. Streams in these systems are currently in good conservation status; this fact is reflected in the macrofauna community structure and water quality (Colla et al 2013)
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