NORTH-WESTERN JOURNAL OF ZOOLOGY 16 (2): 117-124 ©NWJZ, Oradea, Romania, 2020 Article No.: e201101 http://biozoojournals.ro/nwjz/index.html Odonata assemblages as indicators of stream condition – a test from northern Argentina Noelia Malena SCHRÖDER1, Camila Gisel RIPPEL2, Leonardo Horacio WALANTUS3, Pedro Darío ZAPATA1 and Pablo, PESSACQ4 1. Molecular Biotechnology Laboratory, Institute of Biotechnology Misiones, FCEQyN, UNaM. Ruta 12 km 7.5 - Posadas, Misiones, CP 3300, Argentina. 2. Institute of Subtropical Biology. CONICET. UNaM. Posadas, Misiones, Argentina. 3. Entomological Research Center. Posadas, Misiones, Argentina. 4. Esquel Research Centre, for Patagonian mountains and steppe (CIEMEP), UNPSJB. Esquel, Chubut, Argentina. * Corresponding author, N.M. Schröder, Email: [email protected] Received: 29. November 2019 / Accepted: 25. January 2020 / Available online: 30. January 2020 / Printed: December 2020 Abstract. The increasing consumption of natural resources due to population growth, and the expansion of agricultural activity have a major impact on freshwater ecosystems. The aim of this study was to verify if possible changes in habitat condition and physical-chemical variables due to different land uses are reflected by changes in Odonata assemblages. In order to do that, we evaluated the conservation status of the riparian zone and the physicochemical parameters of stream waters affected by different degrees of anthropogenic impact, and assessed richness and variation in species composition, testing for potential indicator species of habitat quality. The riparian index allowed the differentiation of three habitat condition categories: conserved, intermediate and degraded. No significant differences were found in species richness between the three conservation states, but it was possible to discriminate between the communities present. Four species showed potential as habitat quality indicators that can serve as biomonitors in future strategies of stream management and conservation. Key words: bioindicator, land use, dragonfly, IndVal, species assemblage. Introduction the biological communities, sometimes leading to the loss of species sensitive to environmental change (Carvalho et al. The increasing consumption of natural resources causes 2013, da Silva Monteiro et al. 2013, Juen et al. 2014). fragmentation, habitat loss and has a major impact on The continued growth of agricultural activity and the in- freshwater ecosystems by modifying watercourses, altering crease of human population worldwide makes every issue their hydrological regime and causing decreases in water related to the conservation of streams a research priority. quality (Bedient et al. 1994, Hooda et al. 2000, Ometo et al. Although physicochemical indicators are widely used in 2000). The different land uses practices usually extend to the environmental monitoring due to the ease of sampling pro- margins of the streams, without considering the recom- cedures and standardization, among other things, there are mended buffer zones and prohibitions of national and inter- certain limitations related to the high cost of analyses and national legislations and policies aiming their conservation. the increase in the abundance and types of polluting prod- Streams are frequently used as paths to eliminate various ucts that may hinder the evaluation (Li et al. 2010, Springer types of waste (domestic, sewage, industrial, etc.), resulting 2010). In this sense, biological indicators emerge as a way to in their consequent contamination. In addition, river banks complement physicochemical indicators and to overcome are often affected by the urbanization process and housing their limitations. Additionally, they provide tools that allow developments, causing landscape modifications, including us to understand how the environment and stress-impact the broadening and diversion of rivers, construction of artifi- factors influence species dynamics (Karr 1981, Heino et al. cial dams, lagoons or the interruption of channels (Troitiño 2015). This kind of analysis is being implemented with sev- et al. 2010). The same happens in rural contexts, where the eral organisms, however studies are still scarce, taking into streams are frequently used as a waste sink and by the live- account the diverse hydrography and the lack of protection stock taken to water, aside from the increased use of pesti- of aquatic ecosystems (Vörösmarty et al. 2010). Research on cides and fertilizers. the use of abiotic indicators and their possible influence on The loss of riparian vegetation is a common result of aquatic fauna is an effective measure to foster the manage- human activities: increasingly larger areas are assigned to ment and conservation of streams and adjacent areas (Juen et agriculture and livestock farming, urban growth and indus- al. 2016, Calvão et al. 2018). trial development. It is well known that the riparian zone is Odonata species are valuable tools for conservation and effectively protecting the fluvial system (Troitiño et al. 2010). monitoring restoration programs; they have proven to be A conserved margin reduces the erosion, diminishes the in- useful bioindicators of environmental quality (Clark & filtration of sediments and other pollutants, and contributes Samways 1996, Simaika & Samways 2009, Monteiro-Júnior to the maintenance of the autochthonous communities acting et al. 2014, Miguel et al. 2017, Rocha et al. 2019, Suárez-Tovar as a wildlife corridor (Kauffman & Krueger 1984, Zweig & et al. 2019), and they are being used in many ecological stud- Rabenni 2001, Sparovek et al. 2002). On the other hand, the ies (Sahlén & Ekestubbe 2001, Koch et al. 2014, Renner et al. removal of the riparian vegetation has a negative effect on 2016a, May 2019). These insects present a life cycle that the inflow of organic matter that constitutes the primary makes them suitable to reflect measures of habitat quality in source of energy in rivers food chains (Delong & Brusven both aquatic and terrestrial environments. In their larval 1994, Pozo et al. 1997). All these modifications result, in most stage, development occurs in water, and after several molts, cases, in the reduction of diversity, affecting in various ways an adult capable of flying emerges (Corbet 1999). The as- 118 N.M. Schröder et al. Figure 1. Study area and sampling sites evaluated in southern Misiones, Argentina, 2016-2017. sembly of adult odonates is usually influenced by the physi- 1999, Dolný et al. 2012, Oliveira-Junior et al. 2017). We also ognomy and vertical stratification of the marginal vegetation expected to find bioindicator species of habitat quality that and the presence of aquatic plants (Clark & Samways 1996, can serve as biomonitors in future stream management and Hofmann & Mason 2005), since these are parameters related conservation strategies. to habitat selection and oviposition sites (Corbet 1999). Mar- ginal vegetation also regulates local microclimatic conditions (Moore et al. 2005, Carvalho et al. 2013, Rodrigues et al. Material and Methods 2016), and sunlight is one of the determining factors in the Study area behavior of the odonates due to their thermoregulation The study was carried out in the southern range of the Misiones strategies (De Marco & Resende 2002, De Marco et al. 2015). province (Figure 1). This area corresponds to the “Campos y The order Odonata is represented by two suborders in malezales” ecoregion. It is an ecological transition among the limit- the Neotropical region, Zygoptera and Anisoptera. Broadly, ing ecoregions: Selva Paranaense to the northeast, Esteros del Iberá Zygoptera are small species, mainly classified as thermal and Espinal to the southwest (Matteucci 2012). This location, with conformers (Corbet 1999, Mckay & Herman 2008). Anisopte- the influence of different biogeographical areas, favors the presence of a rich fauna including several regional threatened species like ra on the other hand, are usually medium-to-large size spe- manned wolf and pampas deer (IUCN 2015). The landscape is con- cies, classified as heliothermic, although exceptions are stituted of pastures and grasslands with isolated forests patches. In common and some are thermal conformers or endothermic addition, a dense canopy forest is accompanying the fluvial courses. species (Corbet 1999, De Marco & Resende 2002). While the The climate is subtropical humid, with uniform rainfall throughout limits in this regard are not always clear for all species, the the year, between 1500-1700 mm annually (Cabrera 1994, Matteucci two suborders are usually treated separately in ecological 2012). The literature dealing with this region reports a great floristic studies. It has been demonstrated that different eco- diversity due to its peculiar condition of humidity and temperature physiological requirements may determine odonate species (Cabrera 1994). Despite this, it is the least protected region of the country (Chebez 2006) and at the same time one of the most threat- distribution (De Marco et al. 2015), and it is expected that ened because of its small area, increasing forestation with exotic spe- larger species replace smaller ones (e.g. zygopterans re- cies (mostly Pinus sp.) and agriculture. placed by anisopterans) when small stream riparian vegeta- For our study, we selected the most typical land use types of the tion is altered or degraded (Pereira et al. 2019). region: urban, plantation/livestock farming, forestry, and natural re- Our objective in this study was to verify if, in different