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.