We characterized the taxonomic richness of epigean coleopterans and assessed the sampling quality in Llullaillaco National Park (Antofagasta Region, Chile). The study was conducted in representative sites of the national park during the years 2017 and 2018. A total of 185 specimens were captured, belonging to 21 species grouped in 19 genera and 10 families. Entomochilus Solier and Praocis Eschscholtz being the only genera with more than one species. The accumulation curves demonstrating that the inventory of epigean coleopteran richness is still incomplete for the sampled area. This work is the first inventory of arthropod species richness in high-Andean ecosystems, but additional samplings in other habitats and seasons are required to expand the inventory of coleopteran fauna for this protected area.
Coleopterans in high-Andean ecosystems are usually vulnerable to threats to their population size since they are adapted to an extreme environment and, consequently, are very sensitive to biological perturbations (de los Santos Gomez 2010; Staunton et al., 2016) and climate change (Ponel et al., 2003). Additionally, the more restricted range and smaller size of coleopteran populations inhabiting these environments make their extinction rates higher (Alemneh et al., 2017). In that regard, Moret et al. (2016) examined the effect of rising temperatures in the Andes and identified changes in the ecological and climatic tolerance of Carabidae species. They suggest that the species' response to climate change varies according to their specialization and tolerance levels.
In high-Andean ecosystems, epigean coleopterans play multiple ecological roles (Moret, 2009). During the humid phase, they are important pollinators that help dynamize energy flow and nutrient cycles, as well as an abundant high-quality trophic resource (gravid females); during the arid phase (dry periods), in turn, they are important macrodecomposers and an abundant trophic resource for vertebrates (Whitford, 2002). However, despite their importance, knowledge of the coleopterans of the high-Andean ecosystems of northern Chile is very limited.
Some works that have studied this taxon include Cepeda-Pizarro (1997), who examines the diversity of insects in the high-mountainous areas of the Elqui valley (Coquimbo Region); Jerez (2000), who examines the geographic distribution patterns of coleopteran insects in the region of Antofagasta via a parsimony analysis of endemicity; Ferrú and Elgueta (2011), who provide a list of coleopterans, including high-altitude species, that occur in the Arica y Parinacota and Tarapacá regions; and lastly, Ferrú and Pizarro-Araya (2007), who record Pilobalia torresi Molinari, 1968, and Pilobalia escobari Peña, 1973 (Coleoptera: Tenebrionidae), in the locality of Colchane (Tarapacá Region), in the subdesert high-Andean steppe plant formation (Gajardo, 1993). These studies, however, are fragmentary and do not take into consideration the areas belonging to the National System of Protected Wild Areas (SNASPE by its Spanish acronym), such as Llullaillaco National Park (Antofagasta Region, Chile), one of the SNASPE areas that protects and preserves high-altitude biota. Considering that studies on arthropods from this park are nonexistent, we characterized the taxonomic richness of epigean coleopterans and assessed the sampling quality in Llullaillaco National Park.
This study was conducted in Llullaillaco National Park, located in the Andes of northern Chile (Antofagasta Region), between 24°30′S and 25°10′S, and 68°30′W and 69°15′W. The park has a surface area of ∼270,000 ha and an altitude ranging from 3,500 masl to 6,750 masl. It is located in a zone of transition between winter and summer rains (Arroyo et al., 1998), and is subject to significant interannual rain fluctuations (Houston and Hartley, 2003). The mean annual temperature is 2°C and precipitations do not exceed 50 mm/year, conditions that lead to a very prolonged dry phase and to the occurrence of two annual rainfall peaks in winter and summer (Peñaloza et al., 2013). The park's plant diversity is discussed in detail in Luebert and Gajardo (1999), Marticorena et al. (2004), and Peñaloza et al. (2013).
The captures were conducted from April 13 to April 21, 2017. Following Cheli and Corley (2010), four traps were installed 50 meters away from the sampling reference point (samples) and remained active for three nights (SIMEF, 2017). The sampling was conducted on 18 conglomerates (samples) present in Llullaillaco National Park and adjacent areas. In 2018 (May 12 to May 20) the captures were conducted in six conglomerates (25343, 25344, 25345, 24372, 24371 and 24458). The sampled sites' elevations ranged from 2,000 masl to 2,800 masl (25343, 25344, 25345, 25346, 25347, 25348), 3,600 masl to 3,900 masl (25274, 25195, 25196, 25120, 24870, 24871, 24872, 24873, 24874), and 4,000 masl to 4,150 masl (24371, 24372, 24458) (Fig. 1). The collected material was preserved in 70% alcohol until processing and mounting, and is currently deposited at the Laboratorio de Entomología Ecológica of the Universidad de La Serena, Chile (LEULS).
To assess the sampling quality and the relation between the sampling effort (number of samples) and the observed number of species, rarefaction curves were constructed based on the number of samples (i.e., sites). The performance of the ACE, ICE, Chao 1, and Jacknife 1 non-parametric richness estimators was assessed and compared with the observed richness (Sobserved). To remove the effect caused by the samples' order of addition to the curve, we used 100 randomizations with substitutions following Walther and Moore (2005) and Colwell (2013) in the software EstimateS v.9.1.0 (Colwell, 2013).
A total of 185 specimens were captured, belonging to 21 species grouped in 19 genera and 10 families (Table 1). The family Tenebrionidae was represented by 9 species and 7 genera, with Entomochilus and Praocis being the only genera with more than one species. The species Praocis sp. in the subgenus Filotarsus and Praocis sp. in the subgenus Orthogonoderes, have not yet been identified or recorded in sites above 3,700 masl. Species of both these genera inhabit central and northern Chile, western and northern Argentina, eastern Bolivia, and southern Peru (Flores and Pizarro-Araya, 2014), in the biogeographic provinces of Puna, Atacama, Coquimbo, Santiago, Prepuna, Monte, and Central Patagonia (Morrone, 2015). Orthogonoderes species occur from coastal dunes in the coast up to an altitude of 4,200 m in the high Puna plateau (Flores and Pizarro-Araya, 2014), whereas Filotarsus species occur from 1,600 m in high altitudinal valleys of the Andes range to an altitude of 5,200 m in the high Puna plateau (Ferrú and Elgueta, 2011; Flores and Pizarro-Araya, 2014).
The accumulation curves did not show a well-defined asymptote, demonstrating that the inventory of epigean coleopteran richness is still incomplete for the sampled area. All non-parametric estimators showed values greater than the observed values (Sobserved) (Fig. 2). It should be noted that, although the observed coleopteran richness was low, most of the sampling was conducted at 4,000–4,150 masl. This work is the first inventory of arthropod species richness in high-Andean ecosystems, but additional samplings in other habitats and seasons (November to January) are required to expand the inventory of coleopteran fauna for this protected area. More comprehensive samplings in difficult-to-access areas may expand the distribution range of the recorded taxa. In that regard, Jerez (2000) and Girardello et al., (2018) points out that most of the data available in collections and in the literature corresponds to collection campaigns conducted near small towns or close to the road network, therefore providing incomplete information about the area. This work may serve as a basis for building a general inventory and categorizing the future conservation status of coleopterans in the high-Andean ecosystems of northern Chile, which would help to manage this wild area more effectively.
We thank CONAF (the Chilean National Forestry Corporation) for permitting us to work in Llullaillaco National Park (Project N° 008/2017) and especially to Jorge Vega and Nelson Amado. Our special thanks also to Alexis Soto, Oscar Zepeda, Osvaldo Urzúa, and Rodrigo Galleguillos (Minera Escondida, Antofagasta Region), and sergeant major Nelson Colillán Vasquez and first officer Cristian Vergara Galdames (Alemania Police Station, Aguas Verdes, Antofagasta Region), for their extraordinary help with field logistics. We are also grateful to Máximo Hurtado Galaz for providing field assistance and Cristián Delpiano (University of La Serena) for providing SIG support. This research was funded by the Integrated Forest Ecosystem Assessment and Monitoring System (SIMEF by its Spanish acronym), INFOR-IEB Agreement.