Taxonomic and Numerical Resolutions of Nepomorpha (Insecta: Heteroptera) in Cerrado Streams

Taxonomic and Numerical Resolutions of Nepomorpha (Insecta: Heteroptera) in Cerrado Streams Nubia França da Silva Giehl1,4*, Karina Dias-Silva2, Leandro Juen3, Joana Darc Batista4, Helena Soares Ramos Cabette4,5 1 Programa de Po´s-graduaçaõ em Ecologia e Conservaçaõ, Universidade do Estado de Mato Grosso (UNEMAT), Nova Xavantina, Mato Grosso, Brasil, 2 Programa de Po´s- graduaçaõemCieˆncias Ambientais, ICB1, Universidade Federal de Goia´s, Goiaˆnia, Goia´s, Brasil, 3 Laborato´rio de Ecologia e Conservaçaõ, Instituto de Cieˆncias Biolo´gicas, Universidade Federal do Para´ (UFPA), Bele´m, Para´, Brasil, 4 Laborato´rio de Entomologia, Universidade do Estado de Mato Grosso (UNEMAT), Nova Xavantina, Mato Grosso, Brasil, 5 Departamento de Biologia, Universidade do Estado de Mato Grosso (UNEMAT), Nova Xavantina, Mato Grosso, Brasil Abstract Transformations of natural landscapes and their biodiversity have become increasingly dramatic and intense, creating a demand for rapid and inexpensive methods to assess and monitor ecosystems, especially the most vulnerable ones, such as aquatic systems. The speed with which surveys can collect, identify, and describe ecological patterns is much slower than that of the loss of biodiversity. Thus, there is a tendency for higher-level taxonomic identification to be used, a practice that is justified by factors such as the cost-benefit ratio, and the lack of taxonomists and reliable information on species distributions and diversity. However, most of these studies do not evaluate the degree of representativeness obtained by different taxonomic resolutions. Given this demand, the present study aims to investigate the congruence between species- level and genus-level data for the infraorder Nepomorpha, based on taxonomic and numerical resolutions. We collected specimens of aquatic Nepomorpha from five streams of first to fourth order of magnitude in the Pindaı´ba River Basin in the Cerrado of the state of Mato Grosso, Brazil, totaling 20 sites. A principal coordinates analysis (PCoA) applied to the data indicated that species-level and genus-level abundances were relatively similar (.80% similarity), although this similarity was reduced when compared with the presence/absence of genera (R = 0.77). The presence/absence ordinations of species and genera were similar to those recorded for their abundances (R = 0.95 and R = 0.74, respectively). The results indicate that analyses at the genus level may be used instead of species, given a loss of information of 11 to 19%, although congruence is higher when using abundance data instead of presence/absence. This analysis confirms that the use of the genus level data is a safe shortcut for environmental monitoring studies, although this approach must be treated with caution when the objectives include conservation actions, and faunal complementarity and/or inventories. Citation: Giehl NFdS, Dias-Silva K, Juen L, Batista JD, Cabette HSR (2014) Taxonomic and Numerical Resolutions of Nepomorpha (Insecta: Heteroptera) in Cerrado Streams. PLoS ONE 9(8): e103623. doi:10.1371/journal.pone.0103623 Editor: Fabio S. Nascimento, Universidade de Saõ Paulo, Faculdade de Filosofia Cieˆncias e Letras de Ribeiraõ Preto, Brazil Received December 23, 2013; Accepted June 30, 2014; Published August 1, 2014 Copyright: ß 2014 Giehl et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The authors thank the Coordenaçaõ de Aperfeiçoamento de Pessoal de Nı´vel Superior (CAPES) for a masters scholarship and PELD/CNPq for a DTI-C Scholarship; KDS thanks the Conselho Nacional de Desenvolvimento Cientı´fico e Tecnolo´gico (CNPq) for a doctoral scholarship; JDB thanks PELD/CNPq for PDJ scholarship; to the Fundaçaõ de Amparo a Pesquisa do Estado de Mato Grosso (FAPEMAT) (Proc. 98/04), Programa de Apoio a` Pos-Graduaçaõ (PROAP) and Programa de CooperaçaõTećnica (PROCAD #109/2007) for financial support for data collection. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * Email: [email protected] Introduction identification keys may also contribute to the lack of an accurate taxonomic resolution in many studies, few of which are capable of Human activities generate serious impacts on natural aquatic working at the species level. More often than not, then, higher environments, especially by replacing the vegetation with planta- taxonomic levels have been analyzed, and this has been justified tions and pastures [1], constructing dams and reservoirs, and based on arguments such as an effective cost-benefit ratio, the time diverting the natural course of waterways [2,3]. These processes, needed for processing samples [8], limited resources [12], a lack of either alone or in synergy, result in decreased habitat heteroge- taxonomists and/or data on the ranges and ecological require- neity, increased input of sediments into the channel, and the loss of ments of the species [11,13]. aquatic biodiversity [4,5]. Given the difficulties and demands for rapid methods for Due to major environmental problems and limited resources for bioevaluation, a priority issue is understanding the level of evaluating diversity, researchers have resorted to relatively fast and taxonomic identification required for studies of anthropogenic inexpensive methods to evaluate and monitor aquatic ecosystems impacts and the monitoring of aquatic systems [14]. The question [6–9]. In particular, while invertebrates are widely used for the of numerical resolution–whether abundance or presence/absence monitoring of freshwater systems, they are prone to a ‘‘Linnean data are more effective for the analysis of patterns of biodiversity deficit’’ [10], in which closely-related species have been diagnosed and environmental quality–has also been evaluated [9,15]. The based on subtle or even subjective morphological characters, and use of numerical resolution may be an alternative that reduces many have still not been described [11]. The lack of appropriate sample processing time and allows a comparison of results using PLOS ONE | www.plosone.org 1 August 2014 | Volume 9 | Issue 8 | e103623 Taxonomic Resolution of Nepomorpha in Streams different methods of inventory and monitoring, and across classification, first-order watercourses have no tributaries, and different regions [16]. when two first order tributaries are connected, a second-order Insects of the order Heteroptera (Nepomorpha and Gerromor- stream is formed. Thus two combined n order streams form a river pha) have aquatic and semi-aquatic habits, are widely distributed, of (n+1) order. A total of 20 sampling sites (Figure 1), with different and vary considerably in form and niche, allowing them to occupy conservation status were sampled in the Cachoeirinha, Caveira, a diversity of habitats, including both lentic and lotic bodies of Da Mata, Papagaio and Taquaral streams. The sites were visually water [17]. Most heteropterans live exclusively in water from the evaluated using the Habitat Integrity Index (HII) [30]. This index, nymphal stage until becoming adults, as in the case of the adapted from Petersen’s protocol [31] for small brazilian streams, Nepomorpha. These organisms are ecologically-important pred- is composed of twelve questions that describe the pattern of land ators, and provide a variety of ecological services, including: (i) the use outside the riparian forest, riparian forest conditions, and biological control of disease vectors, such as the larvae of stream channel characteristics. The HII provides values from 0 to Anopheles, Culex, and Aedes mosquitoes [18,19] and Biomphalaria 1, and the closer the value is to 1, the more pristine is the stream. snails [20]; (ii) the predation of aquatic and terrestrial organisms at Environments with a HII of less than 0.70 presented the water/air interface; (iii) serving as prey for fish, amphibians, considerable deforestation on one bank and the riparian vegeta- and birds [21]; and (iv) being able to respond to environmental tion, when it existed, was no more than a narrow strip. Land use disturbances [17,22,23]. outside the riparian vegetation consisted of pastures, with periodic Nepomorpha have only recently become the subjects of access of cattle to the streams, resulting in banks with excavations environmental evaluation or conservation studies [e.g. 22–26]. or deep rutting. The most disturbed stream had a weir just In brasilian studies, difficulties have been encountered with regard upstream from the section sampled. Environments with HII$0.70 to the identification of species, which are exacerbated by the lack varied from areas with clearly defined riparian vegetation (from 5 of reference material, which is often dispersed and inaccessible. to 30 m wide) to environments with intact forest without gaps in On the other hand, identification at the generic level is relatively their canopy. Sites with indices closer to 0.70 had extensive simple, being based on well-defined characters. The time pasture or soybean plantations outside the riparian vegetation. necessary for the identification of genera tends to be much shorter, the results more reliable, and there is no need to submit Collection and identification the material to experts. The specimens

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