Introduction
Eucalyptus trees (Myrtaceae) were initially introduced in South America in the early and mid-19th century to meet increasing demands of wood, coal, and firewood in the region (FAO, 1981). Commercial plantations of Eucalyptus have rapidly expanded in the last three decades and together with pine trees, today they constitute the base of forestry development in many countries of South America (Estay, 2020). In Ecuador, several species of Eucalyptus (mostly E. globulus ) were first introduced in 1865 largely for firewood and construction materials (FAO, 1981). They have also been extensively planted for reforestation and erosion control programs, making them very common and even dominant in many landscapes of the Ecuadorian Andes (Granda, 2006). Although Eucalyptus trees mainly occur in the inter-Andean valleys of the country, a massive plantation program to produce wood chips for paper pulp was established in the early 2000 in the coastal province of Esmeraldas. Today, E. globulus is one of the most important tree species in the Ecuadorian forestry sector, which directly employs more than 230 000 people (c.a. 5.5% of the economically active population) and contributes around 2 to 3% to Ecuador’s GDP (Grijalva et al., 2015).
Eucalyptus snout beetles are a complex of cryptic species (Gonipterus scutellatus complex) that feed on Eucalyptusleaves (Schröder et al., 2020). These beetles are native to Eastern Australia and Tasmania. Species of the complex have been accidentally introduced into Western Australia (at an unknown date), New Zealand in 1890, Africa in 1916, South America in 1925, Europe in 1975 and North America in 1994. In South America, they have been introduced in Argentina in 1925, Uruguay in 1937, Brazil in 1955, Chile in 1998 (Estay, 2020; González et al., 2010; Marelli, 1927), and more recently, Colombia in 2016 (Madrigal-Cardeño, 2019; Schröder et al., 2020). The morphological similarity between the species of the Gonipterus scutellatus complex has led to uncertainty and confusion regarding the identity of introduced populations (Mapondera et al., 2012; Schröder et al., 2020). According to the most recent taxonomy (Mapondera et al., 2012), two species of the complex are invasive in South America:G. platensis in Argentina, Brazil, Chile, Colombia and Uruguay, and G. pulverulentus in Uruguay. Correctly identifying newly introduced populations of Eucalyptus snout beetles is a first essential step towards effective management strategies.
In areas outside of their native range, Eucalyptus snout beetles cause severe damage to Eucalyptus trees, with both adults and larvae feeding on leaves and producing important economic losses (Mapondera et al., 2012). Damage includes crown defoliation, stag-horned or witches’ broom appearance, epicormic and stunted growth, reduced tree vigor, and loss of apical dominance (CABI, 2021; Lanfranco & Dungey, 2001), all of which make the trees more susceptible to attack by other organisms (Fiorentino & Medina, 1991). Indeed, Eucalyptus snout beetle infestations were projected to produce between 20 to 85% losses in wood production over a 10-year growth period (Reis et al., 2012). These impacts have raised repeated concern and motivated the development of control programs with the parasitoid Anaphes nitens (de Souza, 2016; González et al., 2010; Hanks et al., 2000; Reis et al., 2012). However, biological control strategies have not always been successful, mainly due to geographical or seasonal mismatch between host and parasite (Mapondera et al., 2012; Reis et al., 2012). This highlights the need for further study of the ecology, taxonomy and life history of the beetles and their natural enemies, such as A. tasmaniae ,A. inexpectatus (Hymenoptera: Mymaridae), Entedon magnificus (Hymenoptera: Eulophidae), and even entomopathogenic fungi that could potentially be used in biological control programs (de Souza, 2016; Garcia et al., 2019; González et al., 2010; Gumovsky et al., 2015; Lobos Peirano, 2018). Finally, given that these beetles are listed as quarantine pests by several plant protection agencies (e.g., EPPO, CPCC, NAPPO) (CABI, 2021), and the long-term presence and uses of this tree in forestry in South America, countries that export Eucalyptusproducts should strive to detect, adequately manage or prevent the introduction and spread of these insects.
Identifying potentially suitable environments where introduced species may thrive can help in mitigation and conservation planning efforts. Potential distributions of alien species into new geographic areas can be estimated with ecological niche models. These predictive models provide estimates of species’ potentially occupied environmental niches based on the relationship between their occurrences and the environmental characteristics of the landscapes where they occur (Jiménez-Valverde et al., 2011; Peterson et al., 2011; Soto-Centeno & Steadman, 2015). Such procedures enable the construction of risk maps that identify areas suitable for invading or potentially invasive alien species and may aid in the implementation of successful biosecurity strategies (Pili et al., 2020).
In this study, we report for the first time the presence of theEucalyptus snout beetle in the city of Quito, Ecuador (Fig. 1). We suspected that these beetles belong to the species G. platensis due to its presence in several other countries of South America (as opposed to G. pulverulentus that is only present in Uruguay) and its recently reported presence in the neighboring country of Colombia (Schröder et al., 2020). To confirm this identification, we sequenced the COI gene of nine specimens collected in different sites in Quito and inferred a phylogeny using additional published sequences. Additionally, under an ecological niche modeling approach, we determined areas of suitable habitat in South America, with a focus on Ecuador, to set a baseline for possible areas at risk of invasion.