Corps de l’article

Introduction

The ambrosia beetle genus Xyleborinus Reitter, 1913 (Xyleborini) comprises at least 84 recognized species worldwide (Cognato 2008). In North America, Rabaglia et al. (2006) listed only three species that belong to the genus Xyleborinus, including X. gracilis (Eichhoff 1868), X. alni (Niisima 1909) and X. saxesenii (Ratzeburg 1837). Of these, only X. gracilis is considered a native species to North and South America; X. alni and X. saxesenii were introduced into the Americas from Asia. Recently, Knižek (2011) proposed that X. alni (Niisima 1909) is synonymous with X. attenuatus (Blandford 1894). Furthermore, Cognato and Rubinoff (2008) identified X. andrewesi (Blandford 1896) in Hawaii. Okins and Thomas (2010) identified X. andrewesi for the first time in the eastern United States based on 24 specimens reared from branches of sugar apple (Annona squamosa L.) in North Fort Myers, Florida. Rabaglia et al. (2010) also recorded X. octiesdentatus (Murayama 1931) for the first time in North America following exotic beetle trapping surveys in Alabama and Louisiana. Rabaglia et al. (2010) provided identification keys for the five recorded species. Another recently identified alien ambrosia beetle, X. artestriatus (Eichhoff 1878), was first reported in Georgia and Texas (Cognato et al. 2013). Consequently, six Xyleborinus species have been identified in North America to date. All of these Xyleborinus species have been inventoried and included in a summary (Hulcr 2012).

In Canada, only two of these Xyleborinus species have been reported: X. saxesenii (Ratzeburg) and X. attenuatus (Blandford). Xyleborinus saxesenii was first recorded in North America in 1915 (Haack 2001). Xyleborinus saxesenii is considered a transcontinental species (Rabaglia et al. 2006) and is widely distributed in Europe (Kirkendall and Faccoli 2010; Knižek 2011). In Quebec, Canada, X. saxesenii was first recorded in 2003 by the Canadian Food Inspection Agency based on specimens recovered from hardwood (CFIA 2003).

Xyleborinus attenuatus was first reported in western North America in 1996 in Washington and Oregon (Mudge et al. 2001). However, some evidence suggests that this species was first recorded in 1995 in four different locations in the Vancouver area of British Columbia, Canada (L.H. Humble, unpublished data cited by Mudge et al. (2001)). In Canada, X. attenuatus was first officially mentioned in 1996 from British Columbia in a report from the Canadian Food Inspection Agency (CFIA 1996). Later, in a publication by Humble and Allen (2006), X. attenuatus was cited as a relatively recent introduction into Canada. Hoebeke and Rabaglia (2007) mentioned for the first time the presence of X. attenuatus in the eastern United States following extensive trapping surveys of exotic bark beetles. Xyleborinus attenuatus was recorded in 2007 in Dartmouth and Debert (Nova Scotia, Canada) during exotic species trapping survey programs of the Canadian Food Inspection Agency (CFIA 2007). In Quebec, X. attenuatus was first recorded in 2009 in Sherbrooke, based on a single specimen captured in Lindgren traps set by the Canadian Food Inspection Agency (Douglas et al. 2013).

In this article, we present new records of X. attenuatus in Quebec, Canada, following a bark beetle survey program performed for the Canadian Department of National Defence.

Material and Methods

Xyleborinus attenuatus specimens were captured during a 3-yr (2011-2013) trapping survey of bark beetle populations at the Farnham Garrison located in Farnham, Quebec, Canada, about 55 km south-east of Montreal. In 2011 and 2012, 12-unit Lindgren multi-funnel traps (Synergy Semiochemicals Corp.®, Burnaby, BC) were used for the survey of bark beetle populations. Lindgren traps were equipped with plastic cups filled with 50 ml of propylene glycol to preserve the captured insects. The traps were baited with a complex of semiochemicals, such as low-release ethanol lure, seudenol lure, frontalin and exotic bark beetle lure (Synergy Semiochemicals Corp.®). In a 2013 survey, the Lindgren traps were baited with pine shoot beetle enhanced lures (Synergy Semiochemicals Corp.®). The field trapping period ranged from the beginning of March to the end of June. Trap cups were sampled weekly, and captured specimens were preserved in 70% alcohol and subsequently mounted and pinned. The identification of captured specimens was performed according to morphological features using a Discovery V20 stereomicroscope (Carl Zeiss Canada Ltd., Toronto, ON). One specimen was also identified from Claude Chantal’s Collection (Varennes, QC). All captured specimens were deposited in the INRS-IAF entomological collection. A distribution map was drawn using ArcGIS and ArcMap 10.0 software.

Results and Discussion

As a result of the 3-yr trapping survey of alien bark beetles, 16 specimens of X. attenuatus were captured as follows: 9-V-2011: three specimens at Farnham Garrison, Farnham, QC; 21-III-2012: one specimen in Varennes, QC (specimen found in Claude Chantal’s Collection); 1-V-2012: two specimens at Farnham Garrison; 17-V-2012: one specimen at Farnham Garrison; 2-V-2013: nine specimens in Farnham Garrison. Considering the previous record by Douglas et al. (2013), X. attenuatus is presently found in three locations in Quebec, Canada: Sherbrooke (45.402406o N; -71.8822763o W), Farnham (45.302716o N; -73.001981 W) and Varennes (45.678116o N; -73.418328o W) (Fig. 1). Xyleborinus attenuatus captures were improved in 2013 by using pine shoot beetle enhanced lure. The basic attractant of this lure type is α-pinene. At the Farnham military garrison, a mixture of coniferous and deciduous stands can be found. Specimens of X. attenuatus were captured mainly in young birch (Betula spp.) stands with a density of four trees per m2. Xyleborinus attenuatus recently migrated to Quebec from the south, possibly from Vermont and Maine based on the actual distribution of X. attenuatus in the northern Unites States (Atkinson 2013).

Figure 1

Map of Xyleborinus attenuatus records in Quebec, Canada (gray square – previous record; red circle – new records)

Map of Xyleborinus attenuatus records in Quebec, Canada (gray square – previous record; red circle – new records)

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Wood (2007) and Cognato (2008) have mentioned that species of the genus Xyleborinus (Reitter) are easily recognizable by the presence of a conical scutellum with the cavity surrounding this structure being abundantly filled with long hair-like setae (Fig. 2). Other related genera such as Xyleborus (Eichhoff) and Anisandrus Ferrari display a larger flat scutellum (Fig. 3) laying on the antero-medial (sutural) borders of both elytra (Holzschuh 1994; Cognato 2008). This species has been described by many authors starting with the original description reported by Blandford (1894) and a later description by Niisima (1909). More recent references regarding the morphological features of X. attenuatus have been provided by Rabaglia et al. (2006), Hoebeke and Rabaglia (2007), Cognato (2008) and Rabaglia et al. (2010). Xyleborinus attenuatus could be easily confused with the closely related species X. saxesenii. However, X. attenuatus has a longer body (2.5 to 3.0 mm) compared with X. saxesenii (1.9 to 2.4 mm), and the elytral declivity displays larger, pointed and hook-like denticles on the third interstriae (Figs. 4, 5).

Figure 2

Xyleborinus attenuatus – scutellum

Xyleborinus attenuatus – scutellum

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Figure 3

Anisandrus sayi – scutellum

Anisandrus sayi – scutellum

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Figure 4

Xyleborinus attenuatus – lateral view of elytral declivity

Xyleborinus attenuatus – lateral view of elytral declivity

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Figure 5

Xyleborinus attenuatus – dorsal view

Xyleborinus attenuatus – dorsal view

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The biology of X. attenuatus is largely unknown. Niisima (1909) provided the first data regarding the biology of this species. The insect bores oval-shaped galleries measuring about 2.4 cm in length and 1.3 cm in width. In Japan, the host plant for X. attenuatus is the grey alder, Alnus incana (L.) Moench. In Japan, adult flight activity has been reported to begin in April or May. Bright and Skidmore (1997), Wood and Bright (1992) and Mudge et al. (2001) have suggested that Alnus Mill., Betula L., Corylus L., Salix L. and Tilia L. may act as hosts for X. attenuatus in the Palearctic region. LaBonte et al. (2005) reported the genus Prunus L. as host for X. attenuatus in North America based on specimens recovered from the trunk of a flowering cherry tree. The genus Prunus L. was first mentioned as host plant in the original habitat of X. attenuatus by Wood and Bright (1992). Additionally, Nikulina et al. (2007) mentioned Populus L., Quercus L. and Fagus L. as host plants for X. attenuatus in eastern Europe. In western Europe, Holzschuh (1994) mentioned the same host plants as for eastern Europe and suggested that X. attenuatus has a large host spectrum.

Like all xyleborines, Xyleborinus species are ambrosia beetles that bore into the xylem of host trees and cultivate fungal symbionts as food for adults and larvae (Biedermann et al. 2009). Fungal symbionts of ambrosia beetles are vertically transmitted supporting the hypothesis of coevolution between two partners (Six 2003). Biedermann et al. (2013) found Raffaelea sulphurea (Batra) T.C. Harrin. and Fusicollaacetilerea (Tubaki, C. Booth and T. Harada) Gräfenhan & Seifert as fungal associates with X. saxesenii. Fungal species associated with xyleborine ambrosia beetles may cause severe tree diseases such as oak dieback in Asia (Kamata et al. 2002) and laurel wilt disease in North America (Mayfield et al. 2008; Harrington and Fraedrich 2010). Moreover, xyleborine ambrosia beetles are the perfect candidates for the invasion of new habitats because of their large host plant spectrum and their ability to inbreed. Theoretically, a single fertilized female can potentially start an entirely new population (Kirkendall 1983; Jordal et al. 2001).

In conclusion, X. attenuatus has recently arrived in Quebec and continues to spread over the province’s territory. To date, we have no information about the occurrence of this species in the neighbouring Canadian provinces of New Brunswick and Ontario. Further studies are required on the biology of this alien ambrosia beetle in order to assess the impact that this species could have on deciduous forests and ornamental trees in Quebec and eastern Canada, especially in the context of climate change.