Diversity and distribution of the Caddisflies (Insecta: Trichoptera) of Ecuador

Introduction

Aquatic ecosystems are among the most threatened on Earth, and the biodiversity they contain, particularly insects, is still largely undiscovered in many parts of the world (Vörösmarty et al., 2010). For example, according to species estimators we only know about 30% of the caddisfly species from the northern Andean region of South America (Venezuela, Colombia, Ecuador, Peru) (RW Holzenthal & B Ríos-Touma, unpublished data). The lack of information on the diversity of species, and their distribution and functional role in aquatic ecosystems, makes predictions of the effects of climate change on these ecosystems and their biota difficult, if not impossible (Holzenthal, Thomson & Ríos-Touma, 2015).

Trichoptera, or caddisflies, are exclusively aquatic in the larval and pupal stages except for a very few terrestrial or semi-terrestrial and brackish-water species and one family whose members are marine (Holzenthal, Thomson & Ríos-Touma, 2015). The members of this order are considered to be biological indicators of good to excellent water quality and are highly sensitive to human disturbance to running waters worldwide (Chang et al., 2014). Currently, there are about 15,000 species described, making Trichoptera the second most diverse monophyletic group of aquatic animals, surpassed only by the clade Diptera: Culicomorpha/Psychodomorpha (Malm, Johanson & Wahlberg, 2013). In Trichoptera, The Neotropical region is the 3rd most species rich in the world with 2100 species recorded as of 2008 after the Oriental and Palearctic regions (De Moor & Ivanov, 2008). In terms of endemism of genera, the Neotropics (115 endemic genera) are second only to the Australasian region (120 endemic genera) (De Moor & Ivanov, 2008)

The Neotropical country of Ecuador hosts an amazing diversity of species, many of them threatened, in two biodiversity “hotspots:” the Tropical Andes and the Tumbes-Choco-Magdalena (Myers et al., 2000). The designation of these hotspots did not include insects or any aquatic biota other than fish. However, the diversity and endemicity of aquatic insects are probably much greater in terms of species numbers than the vertebrate fauna. Considering the importance and sensitivity of aquatic invertebrate biota to changes in habitat, spanning across the watershed, increased knowledge of their taxonomy and biology is urgently needed. Trichoptera are probably one of the best known aquatic groups from the Andes of Ecuador, with some available catalogues of species and their distributions (Flint, Holzenthal & Harris, 1999; Holzenthal & Calor, in press). These baseline data, in addition to the wide range of trophic relationships and microhabitats caddisflies exploit, makes this group ideal for biodiversity and biogeographic studies (Holzenthal, Thomson & Ríos-Touma, 2015). The neighboring countries of Colombia and Peru, have full country or regional Trichoptera checklists (Flint & Reyes, 1991; Flint, 1991; Flint, 1996a; Medellín, Ramírez & Rincón, 2004; Muñoz-Quesada, 2000; Rincón-Hernández, 1999). However, there is no checklist or review of species or their distributions for any aquatic insect order for Ecuador. For these reasons the objectives in this study are to: (1) compile the first list of species of the caddisflies of Ecuador with in-country distribution data from the literature and from our own recent collections; and (2) estimate the total species richness of Ecuadorian caddisflies and define priority areas for future surveys.

Materials & Methods

To gather species information, we referred to the latest version of the Catalog of Neotropical Trichoptera (Holzenthal & Calor, in press). We then searched in the original sources to find more detailed locality information and, especially, the Ecuadorian provinces where the species were recorded. Collections of specimens are recorded in the literature from as early as 1899 (Ulmer, 1905), followed by collections in the early 1900s by Paul Rivet (Navás, 1913) with a large set of collections not appearing until the 1970s by Jeffrey Cohen and Andrea Langley under the Ecuador Peace Corps-Smithsonian Institution Aquatic Insect Survey project which are deposited in the National Museum of Natural History, Smithsonian Institution, Washington, DC, (NMNH). The main taxonomic work on this material was done by O.S. Flint, Jr. (NMNH) during the 1980–90s.

During the period covered by the literature (1899 until present), several new provinces were created in Ecuador, including Morona Santiago (1952), Napo (1959), Orellana (1998), Santa Elena (2007), Santo Domingo (2007), Sucumbios (1989), and Zamora Chinchipe (1953). Since the historical records do not reflect these new political subdivisions, we tried to relate the locality descriptions to the current province. However, the majority of records did not have exact coordinates and others lacked sufficient locality information to allow us to be certain about the collection site. With the literature information at hand, we made a first list of species (Table 1) that we then compared with our own recent collections from Ecuador from 2010 to 2015 (Table S1). Collection methods used ranged from sweep netting (mainly in páramo locations) to collecting at black lights during the early evening (at all sites). See Blahnik & Holzenthal (2004) and Blahnik, Holzenthal & Prather (2007) for a review of collecting methods, field techniques, and genitalia preparation for adult Trichoptera. We made at least two different collections in each of Chimborazo, Imbabura, Morona Santiago, Napo, Pichincha, and Santo Domingo provinces (for exact locations refer to Table S1 and Fig. 1). Specimens collected in our own research are deposited in the University of Minnesota Insect Collection, St. Paul, Minnesota, USA (UMSP), the Museo Ecuatoriano de Ciencias Naturales, Quito, Ecuador (MECN), the Museo de Ecología Acuática de la Universidad San Francisco de Quito, Ecuador (MUEA-USFQ), and the Museo de Zoología de la Universidad Tecnológica Indoamérica, Quito, Ecuador (MZUTI).

From the final list of species (Table 1), we calculated both country richness and province richness. We used the presence of the species per province to calculate an incidence based richness estimator (CHAO 2). This nonparametric species estimator allows for estimation of the potential richness based on the number of observed species, species that are found only in one location, and species that are observed in two locations. Despite its simplicity, a rigorous body of statistical theory demonstrates that CHAO 2 is a robust estimator of minimum richness (Shen, Chao & Lin, 2003) and is more rigorous and performs better in benchmark surveys than extrapolated asymptotic functions or other parametric species richness estimators (Gotelli & Colwell, 2011) with the kind of data used in this study.

Results

We recorded 310 species of Trichoptera in Ecuador, belonging to 15 families and 52 genera. Literature records contained 264 species for the country (Table 1). Of these, 15 did not have specific locality data, although for nine of them we were able to collect additional specimens representing new locality records. We found 48 species that were not previously reported (Table 1 and Table S1). Pichincha (n = 78), Napo (n = 75), and Pastaza (n = 70) were the provinces with the most species recorded in total. However, since these provinces have been divided into new provinces (see Methods), we could not update all records accurately by province because of incomplete locality descriptions in the historical literature. Accordingly, records for Santo Domingo, Sucumbíos, and Orellana provinces could be diminished. On the other hand, Cañar, Guayas, Bolivar, Chimborazo, El Oro, Manabí, and Esmeraldas provinces have less than 10 species recorded (Fig. 1). Carchi, Santa Elena (which was previously part of Guayas) and Galápagos have no species recorded.

A total of 188 species are only known from one province, and 66 species from three or more provinces. According to the species estimator CHAO 2, the estimated caddisfly richness for the country is 578 species, indicating that only 54% of the Ecuadorian caddisfly fauna is known.

Discussion

Hydroptilidae, Hydropsychidae, and Philopotamidae accounted for 58% of the diversity of all Ecuadorian caddisfly species. This pattern is similar to other neotropical countries (Muñoz-Quesada, 2000; Armitage & Cornejo, 2016). Forty-eight new records were added to those that are listed for the country in the current Catalog of Neotropical Caddisflies (Holzenthal & Calor, in press), yet the species estimator suggests that 46% of the species present in the country are yet to be discovered. This does not seem far from reality since, for example, Costa Rica has around 460 species recorded (Holzenthal & Calor, in press). Colombia, a country 22 times as large as Costa Rica and four times the size of Ecuador has only 210 species known (Muñoz-Quesada, 2000). Panama, on the other hand has 300 species recorded (Armitage & Cornejo, 2016). The differences between the published records are clearly related to the number of studies and surveys performed in these countries, with Costa Rica and Panama having a long tradition of biodiversity surveys. Considering the diversity of Ecuadorian ecosystems and the fact that some provinces have less than ten records, we are confident that future surveys will find more species. Most of the coastal provinces, including the Ecuadorian Chocó, are understudied and probably harbor species not known from the Amazon or the Andes. These unexplored provinces are priority areas to conduct future collections and surveys. It is important to emphasize that most of the species recorded and added through our own surveys are represented by one or a few individuals.

The land cover loss in the country is high (Sarmiento, 2002; Eva et al., 2004), especially in the Andean and coastal regions. Since several groups of Trichoptera are known to be highly regionally endemic (Previsic et al., 2009), probably some undescribed species are already lost. Also, climate change might play an important role affecting specialist species, such as those found in glacier-fed streams (Jacobsen et al., 2012). Many protected areas in the Andean and coastal regions are located in mountainous areas, protecting only certain species. We have seen that there is an altitudinal segregation for several groups (Helicopsychidae, Mortoniella), and altitudinal stratification of caddisfly assemblages has been noted (Rincón-Hernández, 1999; Blinn & Ruiter, 2009). This is also a consideration to take into account for future surveys, and the establishment of protected areas should also address altitudinal zonation.

Many new species of Neotropical caddisflies have been described in recent decades. For example, the number of described species increased from 2,214 in 1999 (Flint et al. 1999) to almost 3,260 species today (Holzenthal & Calor, in press) or an increase of more than 1,000 species in 16 years. Currently, in the material we have collected since 2010 we have tentatively identified around 80 new species and some dozens of species known from unidentifiable females. The description of these new species and the identification of others will increase the number of Ecuadorian species to around 400 with material already in hand.

A list of species is a first step in the chain of knowledge of this diverse and sensitive group of insects. However, other important factors in the protection of species diversity is an understanding of their life history and habitat requirements. Currently, we only have these data for one Ecuadorian caddisfly species, Contulma paluguillensis (Holzenthal & Ríos-Touma, 2012). Worldwide, there is a tremendous lack of information on natural history of the world’s biota (Able, 2016). Even in Europe, where almost all the species are described, life-cycle duration, reproduction, and distribution are known for <10% of caddisfly species (Hering et al., 2009). However, this information is crucial to protect and to forecast the effects of climate and land use change on populations and their distributions of this fascinating group of aquatic insects.

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