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ZOOTAXA
ISSN 1175-5326 (print edition)
ISSN 1175-5334 (online edition)
Accepted by L. Kirkendall: 14 Apr. 2021; published: 13 May 2021 161
Zootaxa 4970 (1): 161–170
https://www.mapress.com/j/zt/
Copyright © 2021 Magnolia Press Article
https://doi.org/10.11646/zootaxa.4970.1.8
http://zoobank.org/urn:lsid:zoobank.org:pub:05DE75B6-74B1-4531-BD20-2925FC1921D8
First records of Xylosandrus compactus (Coleoptera: Curculionidae, Scolytinae)
in the Iberian Peninsula: an expanding alien species?
JOSEP M RIBA-FLINCH1, MAR LEZA2 & DIEGO GALLEGO3,4*
1Plant Pathologist and Consulting Arborist, Tossa de Mar, Spain
�
jmriba2001@gmail.com; https://orcid.org/0000-0003-3147-0737
2Department of Biology (Zoology), University of the Balearic Islands, Spain
�
mar.leza@uib.es; https://orcid.org/0000-0002-0134-0221
3Department of Ecology, University of Alicante, Spain
�
diego.gallego@ua.es; https://orcid.org/0000-0002-9258-0238
4Sanidad Agrícola Econex S.L., Santomera, Spain
*Corresponding author
Abstract
Xylosandrus compactus (Eichhoff) (Col.: Curculionidae, Scolytinae) is an ambrosia beetle species native to subtropical
Eastern Asia, with great concern due to its high invasive ability. This species has invaded 54 countries worldwide,
including 4 European countries (Italy, France, Greece, and Spain); it was detected in Mallorca (Balearic Islands, Spain) in
October 2019. In the present work, X. compactus is recorded for the first time in the Iberian Peninsula (Girona province,
NE Spain); specimens were collected in Banyoles (August 2020, attacking twigs of Laurus nobilis and Liquidambar
styraciflua) and Platja d’Aro (October 2020, attacking twigs of L. nobilis). Up-to-date information is presented about its
geographical distribution, host plants, biology, symptoms, associate damages, and the possible origin of this species in
Europe.
Key words: ambrosia beetles, Xyleborini, invasive species, alien species, Laurus nobilis, Liquidambar styraciflua,
Girona, Iberian Peninsula
Introduction
Xylosandrus compactus (Eichhoff) (Col.: Curculionidae, Scolytinae) was detected for the first time in Europe in
winter 2010, in Portici and Napoli provinces (Campania, Italy), attacking twigs of Quercus ilex in a garden. In winter
2012, its presence was reported from Lucca province (Toscana), on Laurus nobilis, also in a garden. Just a couple of
years later, the insect was recorded attacking 26 host plant genera (Bosso et al. 2012, Francardi et al. 2012, Garonna
et al. 2012, Pennacchio et al. 2012). In summer 2016, a heavy attack on 13 ha of Mediterranean maquis in Circeo
National Park (Lazio, Italy) aroused considerable concern because the infestation affected characteristic vegetation,
such as Ceratonia siliqua, L. nobilis, Pistacia lentiscus, Q. ilex, Ruscus aculeatus and Viburnum tinus (Vannini et
al. 2017). In August 2016, damages due to attacks of X. compactus in big branches and trunks of C. siliqua were
described as unusual in Sicily (Gugliuzzo et al. 2019a, 2019b, 2020). Currently, this invasive species is present in
the Italian regions of Campania (since 2011), Toscana, Liguria (since 2012), Lazio (since 2013), Lombardia (since
2015), Sicilia (since 2016), and Emilia-Romagna (since 2018) (SAMFIX 2021, EPPO 2020).
In France, X. compactus was detected in summer 2015, in the departments of Alpes-Maritimes and Var, attacking
various ornamental plants, as Arbutus unedo, L. nobilis, Phillyrea sp. and Q. ilex (Chapin et al. 2016, EPPO
2017, Barnouin et al. 2020). Greece reported occurrences of X. compactus in July 2019 in the region of Argolida
(Peloponnese Peninsula), affecting mainly twigs of C. siliqua, but also in twigs of L. nobilis, Olea europaea, Cercis
siliquastrum, and Rhamnus sp. (Spanou et al. 2019). Spain was the last European country to report attacks of this
alien species when it was detected in October 2019 attacking twigs, branches, and trunk of one C. siliqua in a private
garden located in Mallorca (Balearic Islands) (Leza et al. 2020).
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162 · Zootaxa 4970 (1) © 2021 Magnolia Press
So far, the affected hosts in Italy and France are included in 54 genera of forest, agricultural and ornamental
plants: Acacia, Acer, Alnus, Arbutus, Azalea, Caesalpina, Camellia, Cassia, Castanea, Casuarina, Celtis, Ceratonia,
Cercis, Cinnamomum, Citrus, Cornus, Corylus, Croton, Diospyros, Eucalyptus, Eugenia, Euonymus, Fagus, Ficus,
Fraxinus, Gardenia, Hibiscus, Hydrangea, Jasminum, Laurus, Liquidambar, Liriodendron, Magnolia, Malus, Melia,
Olea, Ostrya, Phyllyrea, Pistacia, Pittosporum, Platanus, Prunus, Punica, Quercus, Rhamnus, Rhododendron,
Ruscus, Salix, Sambucus, Tilia, Ulmus, Viburnum, Vitex, and Vitis (ANSES 2017, CABI 2020, EPPO 2020, SAMFIX
2021). However, the attacks in Italy, France, and Greece have shown a great preference for twigs of L. nobilis and
C. siliqua (Spanou et al. 2019, Gugliuzzo et al. 2020).
Until 2019, two species belonging to Xylosandrus were found in Spain: X. germanus (Blandford, 1894) and
X. crassiusculus (Motschulsky, 1866). Xylosandrus germanus was collected in Muxica (Bizkaia, Basque Country,
Northern Spain) using traps baited with conifer bark beetles attractants in July 2003 (López et al. 2007). In 2011 and
2012, some specimens of this species were collected in other localities of Eastern Basque Country (Goldarazena et
al. 2014), also captured in baited traps. The host plant of X. germanus remain unknown in Spain, although Pfeffer
(1994) cited attacks on Fagus sylvatica, Picea abies, Pinus densiflora, and P. pentaphylla from Western Europa,
while Schott (1994) reported infestations on Alnus spp., Betula spp., Carpinus betulus, Castanea sativa, Fraxinus
spp., Picea spp., Pinus sylvestris, Populus spp., Pseudotsuga menziesii, Quercus spp., Salix spp., and Ulmus glabra
from Alsace region (France). At present, no new locations for X. germanus have been reported in Spain; so the
actual widespread of this species remains not yet clear. In the future, this situation could be worse if X. germanus,
currently recorded in the Basque Country, attacks vegetation from the Mediterranean maquis; in summer 2018, it
was captured in the Circeo National Park (Lazio, Italy), sharing habitat with X. crassiusculus and X. compactus,
when years ago its attacks were focused in deciduous (Juglans spp., Fagus sylvatica, Castanea sativa, and Quercus
petraea) and conifer forests from Northern regions (Contarini et al. 2020).
On the other hand, the occurrence of X. crassiusculus in Spain is more recent. This invasive species was reported
from Benifaió (Valencia, Eastern Spain) in October 2016, attacking C. siliqua in a residential area (Gallego et al.
2017). Currently, and thanks to the tasks developed in the LiFE SAMFIX project, the species was reported from
other four municipalities near the city of Valencia: Alfarp, Monserrat, Picassent, and Náquera, attacking exclusively
C. siliqua. This restriction in host tree diversity in Spain contrasts with the high number of host species reported for
this ambrosia beetle: a total of 124 plant species, distributed in 46 families, whose at least 12 species occur in the
invaded area, highlighting forest genera (Alnus, Populus, Quercus, Salix), crops (Diospyros, Ficus, Malus, Olea,
Prunus) and ornamental genera (Acacia, Hibiscus, Magnolia). In France, attacks of X. crassiusculus have been
reported in C. siliqua, Cercis siliquastrum, Lagerstroemia indica, and Olea europaea, although this insect shows
high preferences for C. siliqua in the Mediterranean region (Barnouin et al. 2020).
X. compactus was reported for the first time in Spain in October 2019, after the detection of one carob tree
showing wilt, foliar necrosis and twig death, and a multitude of small holes with exudates, located in a private garden
of a residential area in Calvià (Mallorca, Balearic Islands) (Leza et al. 2020). In summer 2020, this species was
collected from an attacked C. siliqua in another private garden in Andratx, at 10 km from the first occurrence. Finally,
in summer–fall 2020, this species was recorded in Girona province (NE Spain), with data from several localities
and damages as reported in this work. Also they were reported to the competent authority of the Government, for
notification through the European Union Notification System for Plant Health Interceptions, EUROPHYT.
Methods
In July 2020, the gardener of a private property located in Banyoles (Girona, NE Spain; 42°06’ N, 2°45’ E) reported
sudden and generalized damages in a hedge composed by L. nobilis 5–7 m height, planted in 2008. Damages started
with foliar discoloration and twig wilts, evolving to twig dried, died, and broken. A small hole was observed in the
affected twigs, but no insects were found inside the gallery. As a caution measure, all declined twigs were pruned
and burned, and then a foliar spray treatment with deltamethrin was applied.
New affections on twigs were observed some weeks later. Samples of affected laurel twigs were collected in
3 August 2020 (Figure 1A) for visual inspection under stereomicroscope; the remaining twigs were placed inside
a special rearing cage. All collected insects were preserved in ethanol 70% until they were studied. A few days
later, in the same garden, some affected twigs from a Liquidambar styraciflua were also collected and preserved in
XYLOSANDRUS COMPACTUS IN IBERIA Zootaxa 4970 (1) © 2021 Magnolia Press · 163
the same way. One black 7-funnel trap baited with alpha-pinene and ethanol lures (Econex, Spain) was set up in a
corner of the garden, from August 27 to October 19; captures were collected on September 7 and October 19, and
all Scolytinae were preserved in ethanol 70% for identification.
On 1 October 2020, similar symptoms were detected in one specimen of L. nobilis (2 m height) in a forest
property in Platja d’Aro (Girona, Spain; 41°48’ N, 3°03’ E). Samples of affected twigs were collected and insects
found were preserved in ethanol 70%; the remaining affected twigs were pruned and burned. On 15 December. 2020,
some specimens of ornamental L. nobilis (3 m height, in pots) from Vidreres (Girona, Spain; 41°48’ N, 2°46’ E)
showed very similar symptoms and damages. Some affected twigs were collected, but no insects were found inside
the galleries. During November/December 2020, several private and public gardens, with specimens or hedges of L.
nobilis, were visited in Blanes (Girona, Spain; 41º40’ N, 2º48’ E) and Lloret de Mar (Girona, Spain; 41°41N, 2°50’
E). No symptoms of X. compactus attacks were observed in these gardens.
Results
Taxonomic keys from Wood (1982), Dole & Cognato (2010) and Hulcr & Smith (2010) for genera, and from Faccoli
(2008), Nageleisen et al. (2015) and Gallego et al. (2017) for species were used to identify the Scolytinae captures;
comparison with specimens from our personal collections was also used. Number and source of collected specimens
are summarized in Table 1. We confirm that the insects collected in Banyoles, from affected twigs (directly or
by rearing cage emergence) and captured by the baited funnel trap, are X. compactus. A total of 80 adults were
collected from the rearing cage, with 69 females (1.6–1.9 mm) and 11 males (< 1 mm). From the affected twigs of
L. styraciflua, two adult females of X. compactus were collected. From Platja d’Aro, we collected 3 adult females
by direct collection in affected twigs. The laurels from Vidreres showed signs of attack by X. compactus but the
galleries were empty.
TABLE 1. Specimen number of X. compactus collected by locality and source.
Locality Coordinates Host plant Date Source Specimens/
gender
Banyoles 42°06’ N, 2°45’ E Laurus nobilis 2020/Aug/03 Collection from twigs 5 ♀
2020/Oct/01 Rearing cage 69 ♀
11 ♂
Liquidambar styraciflua 2020/Aug/03 Collection from twigs 2 ♀
2020/Sep/17 Baited trap 6 ♀
2020/Oct/19 7 ♀
Platja d’Aro 41°48’ N, 3°03’ E Laurus nobilis 2020/Oct/01 Collection from twigs 3 ♀
Vidreres 41°48’ N, 2°46’ E Laurus nobilis 2020/Dec/15 Collection from twigs No specimens
found in galleries
The mean size of attacked twigs of L. nobilis from Banyoles was 6.4 mm diameter (Figure 1, Table 2), ranging
from 3 mm up to 20 mm. The attacks in L. styraciflua occurred in twigs with a mean diameter of 4.4 mm, ranged
from 3 mm up to 6 mm. In Platja d’Aro and Vidreres, both in L. nobilis, the size was similar, with 4.7 and 4.2 mm
respectively. In the most frequent affected twigs (4 mm diameter, 15–30 cm length) a single attack hole was only
observed, whereas in the biggest affected twigs (15–20 mm diameter, 50–90 cm length) a maximum of 9 holes was
counted, spaced from 3 up to 20 cm between them. The length of galleries ranged from 13 to 30 mm, although not
all attacks were completed; 35% of inspected holes showed no brood chamber or gallery inside. A dark coloration
envelops the internal tissues around the brood gallery (Figure 1 B, C, and E), showing the saprophytic activity of the
ambrosial fungi inoculated by X. compactus.
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164 · Zootaxa 4970 (1) © 2021 Magnolia Press
TABLE 2. Size of attacked twigs. Std: standard deviation, Ø: diameter.
Locality Number and host plant Twigs Diameter (mean ± std, mm) Max Ø (mm) Min Ø (mm)
Banyoles 15 Laurus nobilis 51 6.39 ± 3.68 20 3
1 Liquidambar styraciflua 5 4.40 ± 1.14 6 3
Platja d’Aro 1 Laurus nobilis 7 4.71 ± 1.38 7 3
Vidreres 2 Laurus nobilis 5 4.20 ± 0.84 5 3
Four species of Scolytinae were collected in the baited trap set up in Banyoles during the sampled period (Table
3). In the first revision (17 September 2020), after 21 days, 6 X. compactus, 15 Xyleborinus saxesenii (Ratzeburg),
and 5 Cryphalini (possibly Hypothenemus eruditus Westwood, pending confirmation) were collected. In the second
revision (19 October 2020), 7 X. compactus, 7 X. saxesenii, 1 Xyleborus monographus (Fabricius), and 2 possible
H. eruditus were collected.
TABLE 3. Scolytinae collected in the baited trap set up in Banyoles (from 27 August 27 to 19 October 2020).
Species 17 Sep. 19 Oct. Total
Xylosandrus compactus 6 7 13
Xyleborinus saxesenii 15 7 23
Xyleborus monographus 0 1 1
Cryphalini (possibly Hypothenemus eruditus)5 2 7
Review of Biology and Ecology
X. compactus is a typical ambrosia beetle, whose larvae eat the symbiotic ambrosia fungi that grow covering the
gallery walls. These fungi spores have been transported into the thoracic micangium, located between pronote
and mesonote, by the founder females. This species breeds by haplodiploidy, with arrhenotokous parthenogenesis:
males are born from unfertilized (haploid) eggs and females from fertilized (diploid) eggs. The sex ratio is not
balanced, with 1 male per 9–10 females approximately (Hara & Beardsley 1979, Greco & Wright 2015). Males
have non-functional wings and usually live their whole life inside the gallery where born. Females are inseminated
by a brother male inside their brood gallery. Only the adult females are able to leave the natal host plant and find
new hosts, and emergence usual occurs in the afternoon hours (Hara & Beardsley 1979). Frequently, they attack
twigs and small branches (up to 20 mm diameter), but attacks on bigger branches or main trunks of C. siliqua have
been reported by Gugliuzzo et al. (2019a) from Sicily (Italy) and Leza et al. (2020) from Mallorca (Spain). Founder
females bore for oviposition until reaching the twig medulla, where they construct a brood gallery, shaped linearly,
more or less sinuous and centered in the twig, usually 10–30 mm length (up to 57 mm) and 0.5–6.5 mm width,
and forked from the entrance tunnel. But galleries have a different morphology when females bore in big branches
and trunks; in these situations, the galleries are bored in the xylem (Gugliuzzo et al. 2019b). Oviposition occurs
4–7 days after the female bores into a twig; eggs hatch 3–5 days after being laid (Greco & Wright 2015). Total egg
production per female ranges from 2 to 16 eggs (Hara & Beardsley 1979) and each gallery could produce between
10 and 40–60 new adults (Dixon et al. 2003, Gugliuzzo et al. 2019b). Larvae do not bore galleries, but live in the
brood gallery, eating the coating of ambrosia fungi.
Adult females overwinter inside the brood galleries and the new attacks start in spring. From Italy and Southern
France, X. compactus could be bivoltine or trivoltine, from April–May to the end of November (Pennacchio et al.
2012, Roques et al. 2019). The life cycle is developed in 28–31 days at laboratory conditions (Ngoan et al. 1976,
Hara & Beardsley 1979), but it could need up to 40 days depending on the physical and chemical conditions of the
host tree and the climatic conditions (Brader 1964). Adult females live between 39 and 58 days, whereas males have
a life span of 4–6 days (Hara & Beardsley 1979). The maximum flight and attacks would be in summer, from June
to early September (Ngoan et al. 1976), and Gugliuzzo et al. (2019a) referred the, possibly exceptional, ability to
migrate more than 8 km from an infested area to a healthy area within one year.
Meteorology determines the phenology of X. compactus. The flight after overwintering comes when daily
maximum temperatures remain stable for several days above 20ºC (Gugliuzzo et al. 2019a); similar behavior has
XYLOSANDRUS COMPACTUS IN IBERIA Zootaxa 4970 (1) © 2021 Magnolia Press · 165
been reported, using baited traps, for X. germanus (Reding et al. 2013). In Sicily, X. compactus could not stablish
permanent populations above 400 m altitude, where minimum winter temperatures are usually negative (Gugliuzzo
et al. 2019a). In Banyoles, during the 2016–2019 period (Table 4), the average temperature for the coldest months
(January and February) ranged between 1.2 to 1.3 ºC, with minimum values of -3.9 ºC in February 2018 and -5 ºC
in January 2017 (SMC 2020).
TABLE 4. Meteorological data from the station located in Banyoles (42º6’N, 2º47’ E, www.meteo.cat) during the period
2016–2019; it shows (in ºC) annual mean temperature (AMeTem), minimum mean temperature (MMinT), and minimum
temperature (MinT) for January and February
Year AMeTem MMinT (Jan) MinT (Jan) MMinT (Feb) MinT (Feb)
2019 15,8 1,3 -3,5 3,9 -0,8
2018 15,6 4,5 -0,6 1,2 -3,9
2017 15,6 1,7 -5,0 5,8 -0,4
2016 15,4 4,9 -2,6 4,1 -1,2
Damages
X. compactus produces two kinds of damage on the host plant: mechanical by boring (Figure 1 D and E) and fungal
by the inoculation of the saprophytic fungi into the xylem (Figure 1 B, C, and E). Mechanical injuries are related
to the boring of the entrance hole (0.7–0.9 mm diameter; Figure 1 D) and the excavation of the brood gallery (up
to 30–57 mm long; Figure 1 E) along the twig medulla injure the vascular tissue, and the structural resistance is
also reduced. On the other hand, the ambrosia fungi cultivated inside the gallery act as pathogens to the host plant,
degrading the induced plant defenses and blocking the sap fluxes; moreover, the fungi can produce antagonistic
substances to avoid the development of other microorganisms inside the galleries (Greco & Wright 2015). Gugliuzzo
et al. (2020) reported in Italy 8 species of symbiotic fungi associated with X. compactus or its brood galleries,
usually Ambrosiella xylebori, A. macrospora, and Fusarium solani. Moreover, Bateman et al. (2016) and Vannini
et al. (2017) reported other fungi, as Acremonium, Clonostachys, Cytospora, Penicillium, and Xenoacremonium.
Furthermore, the fungal diseases associated with some Scolytinae and Platypodinae species are some of the most
important problems that have arisen in woody plants in recent decades (Ploetz et al. 2013).
We observed attacks of X. compactus in apparently healthy host plants, behavior also seen in other invasive
Xyleborini on non-native plant species (Atkinson et al., 1988; Henin & Verstein, 2004). Their attacks are more
frequent in the annual twigs (3–7 mm diameter), eliciting their death or breaking, though Gugliuzzo et al. (2019b)
found attacks in trunks and branches with maximum values of 85 cm and 36 cm, respectively. The first attack
evidence is white frass surrounding the entrance hole, followed by a turgor loss, wilt, and twig collapse, with a
progressive discoloration that ends in dryness and death of the twig from the entrance hole to the apex. This wilting
is already visible a few days after the attack, accordingly with Greco & Wright (2015) on Coffea. Other evidence
of the attack and associated damage is the cortical canker (Figure 1D) that has formed around the entrance hole
and along the brood gallery, between 1 and 21 cm length. The affected bark shows brown-purplish colorations, that
stand out from the typical brown drying (above the attacked area in the twig) and from the normal photosynthetic
green (below the attacked area). Debarking or cutting the twig on the affected area show xylem fibers with dark
colorations, due to the ambrosia fungi activity (Figure 1B, 1C and 1E). These fungi do not cause degradation of
the woody structure, but they are responsible for vascular collapse by plugging. This typology of symptoms and
damages observed are in agreement with those reported by Hara & Beardsley (1979), Chong et al. (2009), Greco &
Wright (2015), ANSES (2017), Gugliuzzo et al. (2019a, 2019b, 2020), Roques et al. (2019), Barnouin et al. (2020),
and CABI (2020).
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166 · Zootaxa 4970 (1) © 2021 Magnolia Press
FIGURE 1. (A) Affected laurel (Laurus nobilis) twig in Banyoles (Girona); (B) cross section of an affected laurel twig;
(C) Females of X. compactus were found inside the brood gallery of a small laurel twig; (D) Detail of the cortical canker on
an affected laurel twig, near the entrance hole to the brood gallery; (E) brood gallery (3 cm long) established along the twig
medulla.
Geographical distribution and possible origin of the invasion
These records about the presence for X. compactus during summer/fall 2020 in Banyoles, Platja d’Aro, and quite
possibly also in Vidreres, all of them in Girona province (NE Spain), are the first records for this species in Catalonia
(NE Spain) and also in the Iberian Peninsula; it must be remembered that the first record in Spain was reported
by Leza et al. (2020) from Mallorca (Balearic Islands) in October 2019. According to information received by the
gardener from Banyoles, the presence of a few affected twigs in the laurel hedge was already observed during summer
2019, but it did not generate too much concern. However, in summer 2020, the damages were more conspicuous and
generated alarm. This would indicate that X. compactus was present in this garden since spring 2019, at least.
The linear distance between Banyoles and Platja d’Aro is 42 km, while Platja d’Aro and Vidreres are separated
by 24 linear km. On the other hand, according to Barnouin et al. (2020), the French records closest to Girona are
located at Saint Tropez (captured in 2015 and 2017), at Bormes Les Mimosas (from 2018 and 2019), and at Saint
Raphaël (from 2019), all of them in Var Department (Figure 2); the distance between these French locations and
Banyoles is about 550 km. Probably, the introduction of X. compactus in the Iberian Peninsula is related to the
commerce of live ornamental plants. The chronology of European records for this species starts at Campania (Italy)
XYLOSANDRUS COMPACTUS IN IBERIA Zootaxa 4970 (1) © 2021 Magnolia Press · 167
in winter 2010 (Garona et al. 2012), followed by Alpes-Maritimes and Var (France) in summer 2015 (Chapin et al.
2016), Argolida (Greece) in July 2019 (Spanou et al. 2019), Mallorca (Spain) in October 2019 (Leza et al. 2020) and
we report Girona (NE Spain) in August 2020, although it is possible that the species was present in the area as early
as 2019. The first detection of X. compactus in France happened at Alpes-Maritimes Department, near the Italian
border of Piemonte and Liguria regions. Similarly, the congeneric X. crassiusculus, was first detected for Europe
in the Italian region of Toscana (Pennachio et al. 2003) and the first record from France was in Alpes-Maritimes,
near the Italian border (Roques et al. 2019). Possibly, both species arrived in France from Italy by ornamental plant
commerce, facilitated by the garden industry from Southern France (ANSES 2017, Gallego et al. 2017, Roques
et al. 2019). A very similar situation happened in Slovenia when X. crassiusculus was recorded in August 2017
at Podsabotin and Pračina, very close to the Italian border of the region of Friuli-Venecia Julia (Kavčič 2018).
Accordingly, we suspect that live ornamental plant commerce for public and private gardens of residential areas are
also related with the presence of X. compactus in Mallorca and Girona.
FIGURE 2. Reports of X. compactus in Spain and nearest locations in France: G1: Banyoles, G2: Platja d’Aro, G3: Vidreres
(Girona) and M1: Mallorca (Leza et al. 2020) from Spain; F1: Saint Tropez, F2: Bormes Les Mimosas, and F3: Saint Raphaël
(Var Department)
Simultaneous occurrence of several populations of Xylosandrus species in different European localities, after
the first detection in Italia in 2010, could be evidence of independent introduction events, either by infested host
plants directly from native Asian areas or by internal EU plant commerce from Italian plant producers. The European
Life SAMFIX project has, between their tasks, put in light the origin of these populations by molecular techniques,
currently in progress. New samples of insects from Girona will be taken in spring 2021 and will be sent to the
SAMFIX team for analysis. The risk of invasion for these species to new areas is very high because a simple adult
female could establish a permanent colony by inbreeding, and generate up to three annual generations that could
widespread quickly and silently across extended territories.
Potential distribution models of X. compactus proposed by Urvois et al. (2021) describe as suitable territories
the Mediterranean coasts and islands, except for Tunisia, Libya, Egypt, and Southeastern Iberian Peninsula. Authors
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168 · Zootaxa 4970 (1) © 2021 Magnolia Press
also indicate that the Atlantic coast of the Iberian Peninsula, France, up to the UK are suitable areas, although
suitability decreases northwards and generally with distance from the coast. Accordingly, it is very likely that in
the next few years X. compactus will colonize new areas, expanding its distribution across suitable habitats in the
Iberian Peninsula. Kirkendall & Faccoli (2010) reported 19 alien Scolytinae species were apparently established in
Europe, 14 as potentially expanding (as X. crassiusculus), and 5 as probably currently spreading (as X. germanus).
Some years later, Rassati et al. (2016) reported 18 species in the Mediterranean Basin. Recently, Barnouin et al
(2020) listed 21 invasive species to France since XIX century, but more than half, 11 species, have been recently
introduced. Exotic and invasive Scolytinae pose a major threat to the forest, agricultural, and ornamental plant
resources around the world, and they can have serious economic and ecological consequences. A globalized trade,
aided by climate change, makes the transport of plant material colonized by these insects worldwide recognized as a
very important means of current biological invasions. So, implement new management and policy measures on live
plant commerce and early alert systems in the potential areas are indispensable to avoid future invasions.
Acknowledgements
We thank the people who, through citizen science, allowed the detection of the presence of X. compactus in some
locations from Girona, as well as for the help received and facilities they have provided us to work in their facilities:
Quim Llovera (Banyoles; Center de Jardineria 9 Jardí) and Toni Planas (Platja d’Aro; Parc d’Aventures Costa
Brava). Voucher specimens were deposited in authors’ private collections.
References
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