Revista de Biología Tropical, ISSN: 2215-2075, Vol. 71: e50081, enero-diciembre 2023 (Publicado 27 de enero, 2023)
Influence of ecoregion and river type on neotropical Chironomidae (Diptera)
from humid mountain to semiarid lowland
Edgardo Javier Ignacio Pero1*; https://orcid.org/0000-0002-6335-8654
Silvia Elena Torrejon2; https://orcid.org/0000-0003-0675-6645
Carlos Molineri3; https://orcid.org/0000-0003-2662-624X
1. Instituto de Biodiversidad Neotropical (IBN), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET),
Facultad de Ciencias Naturales e Instituto Miguel Lillo, Universidad Nacional de Tucumán (UNT), Tucumán,
Argentina, Universidad de San Pablo-Tucumán, Tucumán, Argentina; peroedgardo@gmail.com (Correspondence*)
2. Instituto de Ecorregiones Andinas (INECOA), Consejo Nacional de Investigaciones Científicas y Técnicas
(CONICET), Facultad de Ciencias Agrarias, Universidad Nacional de Jujuy, Alberdi 47, C. P. 4600. S. S de Jujuy,
Jujuy, Argentina; torrejonelena@gmail.com
3. Instituto de Biodiversidad Neotropical (IBN), Consejo Nacional de Investigaciones Científicas y Técnicas
(CONICET), Facultad de Ciencias Naturales e Instituto Miguel Lillo, Universidad Nacional de Tucumán (UNT),
Tucumán, Argentina; carlosmolineri@gmail.com
Received 09-VI-2022. Corrected 09-I-2023. Accepted 18-I-2023.
Introduction: Chironomidae (Diptera) is the most widespread and abundant aquatic insect family in freshwater
ecosystems. Chironomids are considered good indicators of water quality but are seldom identified at the genus
level in broad spatial scale studies.
Objective: To identify environmental conditions associated with chironomids in an altitudinal gradient.
Methods: We compared ecoregions, river types, and seasons, for chironomids in neotropical streams and rivers
(18 river sites; 2014-2018; Yungas rainforest and Western Chaco dry forest, Argentina). We used non-metric
multidimensional scaling, dissimilarity, envfit analysis and rank-abundance curves.
Results: Chironomid “assemblages” matched both ecoregions and river types. However, ecoregions presented a
better fit with species composition. The stenothermal taxa of Orthocladiinae were dominant at high elevations
and the eurythermal Chironominae in lowland rivers. Altitude, water temperature and conductivity were impor-
tant. Seasonal differences were smaller than ecoregional differences.
Conclusions: Ecoregions, altitude, water temperature and conductivity correlated with chironomid communi-
ties. Orthocladiinae were dominant at high elevations and Chironominae in lowland rivers.
Key words: non-biting midges; Tanypodinae; Diamesinae; Podonominae; macroecology, rivers, South America.
Influencia de la ecorregión y tipo de río en Chironomidae neotropical (Diptera)
desde las montañas húmedas hasta tierras bajas semiáridas
Introducción: Chironomidae (Diptera) es la familia de insectos acuáticos más extendida y abundante en los
ecosistemas dulceacuícolas. Los quironómidos se consideran buenos indicadores de la calidad del agua, pero
rara vez se identifican a nivel de género en estudios de amplia escala espacial.
Objetivo: Identificar las condiciones ambientales asociadas a los quironómidos en un gradiente altitudinal.
2Revista de Biología Tropical, ISSN: 2215-2075 Vol. 71: e50081, enero-diciembre 2023 (Publicado 27 de enero, 2023)
Aquatic macroinvertebrates are widely
used to understand general biological distri-
butional patterns and are also used extensively
as indicators of the biological quality of fresh-
water ecosystems (Resh et al., 1995). Chiron-
omidae (Diptera) is the most widespread of
aquatic insect families (Ferrington, 2008) and
is the most abundant insect group in aquatic
ecosystems (Armitage et al., 1995; Shadrin et
al., 2017; Shadrin et al., 2019). Their immature
stages (larva and pupa) are very important in
aquatic trophic webs; constituting a consider-
able part of the diet of other invertebrates,
fishes, amphibians and birds (Armitage et al.,
1995). In addition, different taxonomic levels
of Chironomidae (subfamily, genus or spe-
cies) have been considered good indicators of
water quality for biomonitoring (Molineri et
al., 2020). However, due to taxonomic difficul-
ties, chironomids are often only identified at
family level in broad spatial scale studies and
biomonitoring programs (Lencioni et al., 2018;
Rossaro et al., 2022).
Many studies carried out in the Holartic
region have recorded variation in chironomid
larval assemblages along spatial and altitudinal
gradients (Lindergaard & Brodensen, 1995;
Rossaro et al., 2006). These studies reported
that Orthocladiinae, Diamesinae, and Prodi-
amesinae are the predominant taxa in moun-
tain streams while Chironominae (especially,
Métodos: Comparamos ecorregiones, tipos de ríos y estaciones para quironómidos en arroyos y ríos neotropi-
cales (18 sitios en ríos; 2014-2018; en un bosque tropical de Yungas y un bosque seco del Chaco Occidental,
Argentina). Utilizamos escalamiento no métrico multidimensional, disimilitud, análisis de envfit y curvas de
Resultados: Los “ensamblajes” de quironómidos coincidieron tanto con las ecorregiones como con los tipos de
ríos. Sin embargo, las ecorregiones presentaron un mejor ajuste con la composición de especies. Los taxones
estenotérmicos de Orthocladiinae fueron dominantes en las elevaciones altas y los euritermales de Chironominae
en los ríos de las tierras bajas. La altitud, la temperatura del agua y la conductividad fueron importantes. Las
diferencias estacionales fueron menores que las diferencias ecorregionales.
Conclusiones: las ecorregiones, la altitud, la temperatura del agua y la conductividad se correlacionaron con las
comunidades de quironómidos. Orthocladiinae fue dominante en los sitios altos y Chironominae en los ríos de
tierras bajas.
Palabras clave: Quironómidos; Tanypodinae; Diamesinae; Podonominae; macroecología; ríos; Sudamérica.
Chironomini) increase toward the lowlands.
Water temperature and current regime were
proposed to be the main factors related to
the distributional patterns observed in these
assemblages (Eggermont & Heiri, 2012; Run-
dle et al., 2007). In Europe, several studies
that have included data from Chironomidae at
genus level, found that the composition was
concordant with river classifications, such as
geomorphological division (Schöll & Haybach,
2004), ecotypes (Puntí et al., 2007; Puntí et al.,
2009), or ecoregions (Plóciennik & Karaouzas,
2014). However, the differences among assem-
blages were small in some cases (Puntí et al.,
2007), indicating an important overlap between
chironomid assemblages and suggesting that
a top-down classification of streams (using
ecotypes) does not necessarily imply exclusive
assemblages of chironomids.
Some studies of Chironomidae from the
Neotropical regions have reported similar dis-
tributional patterns along altitudinal gradients.
Orthocladiinae, Diamesinae and Podonominae
are more frequent in high elevation streams,
while Chironominae are dominant in lowland
rivers (Acosta & Prat, 2010; Medina et al.,
2008; Principe et al., 2008; Rodríguez Garay
et al., 2020; Scheibler et al., 2014; Tejerina &
Malizia, 2012; Tejerina & Molineri, 2007; Vil-
lamarin et al., 2021; Zanotto-Arpellino et al.,
2015). Chironomidae studies from neotropical
lowlands streams and rivers in semiarid zones
Revista de Biología Tropical, ISSN: 2215-2075, Vol. 71: e50081, enero-diciembre 2023 (Publicado 27 de enero, 2023)
such as those of the Western Chaco dry forest,
are still scarce. Nevertheless, recent studies that
analyzed benthic macroinvertebrates distribu-
tion in rivers of the Western Chaco ecoregion
revealed that chironomids are the most abun-
dant invertebrate group (Leiva et al., 2020; Pero
et al., 2019).
In addition, it is also important to know the
seasonal variations of freshwater ecosystems
features across contrasting climatic but contig-
uous regions, mainly because of the uncertain
challenges of climate change (Tonkin et al.,
2019) and for the inference of reference con-
ditions for the bioassessment (Hawkins et al.,
2010). Some studies associated seasonal dis-
turbances in streams, such as spates and floods,
as important features structuring Chironomidae
assemblages (Langton & Casas, 1998; Rossaro
et al., 2006). The relative abundance of Chi-
ronomidae subfamilies also showed temporal
variation in neotropical streams, such as those
of Yungas forest. For example, Orthocladiinae
was better represented during low water period
whereas Chironominae was more abundant in
high-water period (Tejerina & Malizia, 2012).
Nonetheless, Acosta and Prat (2010) found that
in both the dry and rainy seasons, the subfamily
Orthocladiinae was dominant, surpassing 70 %
of the total of Chironomidae in high elevation
streams of Andean region of Peru.
It is important to know the distributional
variations of these aquatic insects in reference
conditions along the landscape to improve
water quality bioassessments (Nicasio & Juen,
2015) and extend our knowledge about how
climatic and ecoregional gradients influence
the distribution and function of the freshwater
neotropical biota. Therefore, our main goal was
to explore the vertical and spatial distribution
of chironomids in Northwestern Argentina,
expanding the study area in the Yungas Forest
with respect to Tejerina and Malizia (2012) and
including a comparative analysis with rivers of
the little-explored and highly threatened West-
ern Chaco ecoregion (which represent the first
specific study on chironomids for this region).
Hence, we aimed to answer: (1) How do the
composition and structure of Chironomidae
assemblages (genus and subfamilies) vary
between Yungas and Western Chaco ecoregions
and among mountains, foothills and lowlands
in Northwestern Argentina? (2) How do com-
position and structure of Chironomidae vary
between hydrological seasons (low and high-
water periods)? (3) How is Chironomidae dis-
tribution related to the environmental features
of the studied rivers?
Study Area: The study area is located
between (26°-28° S & 66°-64° W) and covers
approximately 20 000 km2 including most of
Tucumán province and its limits with San-
tiago del Estero province in Northwestern
Argentina (Fig. 1). In this study, we sampled
reaches of fluvial channels located in two dif-
ferent ecoregions: Yungas subtropical cloud
forest and Western Chaco dry forest (Brown &
Pacheco, 2006).
The Yungas subtropical cloud forest or
Yungas forest is a narrow belt of mountain
rainforest, ranging from 400 to over 3 000
m.a.s.l. (Brown, 2000). The climate is warm
and humid, with annual average temperatures
ranging from 14 to 26 °C and rainfall from
1 000 to 2 500 mm (Brown et al., 2001). The
Yungas forest is stratified into 3 vegetation
belts. In general, Yungas altitudinal levels are
not considered sub-ecoregion units, but in this
study, we evaluated them as differentiated units
within the Yungas forest because each altitudi-
nal level presents particular climatic features
and floristic composition (Brown & Pacheco,
2006). The high montane forest (1 500-3 000
m.a.s.l.) contains monospecific tree stands that
are usually either Alnus acuminata (Kunth) or
Podocarpus parlatorei (Pilg.). Annual rainfall
reaches 1 000 mm. The low montane for-
est (700-1 500 m.a.s.l.) has the most diverse
vegetation, with many evergreen species, and
is dominated by Cinnamomum porphyrium
(Griseb.) Kosterm. and Blepharocalyx salicifo-
lius (Kunth) O. Berg. The low montane forest
also has the highest precipitation (2 000 mm
annual) and least seasonal hydrological regime.