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.

ABSTRACT

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.

RESUMEN

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.

https://doi.org/10.15517/rev.biol.trop..v71i1.50081

AQUATIC ECOLOGY

2Revista de Biología Tropical, ISSN: 2215-2075 Vol. 71: e50081, enero-diciembre 2023 (Publicado 27 de enero, 2023)

INTRODUCTION

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

rango-abundancia.

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?

MATERIALS AND METHODS

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.