**1. Introduction**

68 Zoology

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The term "biological invasion" comes with two aspects, on one hand it refers to the introduction of an exotic species, and/or non-local populations of any species to a given geographical area, while on the other hand it refers to the ecological and/or the economical consequences of such activity (Perrings et al., 2002). With accelerating socioeconomic development and globalization, issues of biological invasion are of increasing concern, as some invasive alien species are capable of causing catastrophe to local environments and the economies (Xu et al., 2006; Meyerson & Mooney, 2007).

Intentionally or accidentally, human beings constantly introduce organisms to new habitats. For those cases of intentional introduction, some were for agronomic purposes and have been proved to be beneficiary, such as potatoes, maize, peanuts, and sunflowers (Pope et al., 2001; S.M. Wang, 2004). However, others like *Eichharnia crassipes* (Martius) had caused a diversity of problems (Harley et al., 1996; Julien, 2001; T.J. Hu et al., 2009). For accidental introduction, the consequences are often more negative, as these organisms often go undetected until they have expanded their population considerably. The invasion and expansion of *Eupatorium adenophorum* Sprengel in western China is a typical example (R. Wang & Y.Z. Wang, 2006; R. Wang et al., 2011).

Yunnan Province in southwestern China is situated in the low-latitudinal plateau region (LLPR) connecting the Indochinese peninsula and the western portion of mainland China, where the terrain and climate are complex (Z.Y. Chen, 2001; S.Y. Wang & W. Zhang, 2005). Such distinct geographical position and natural environment entitle Yunnan a wide scope of ecosystems except desert and ocean in the northern hemisphere (Guo & Long, 1998). Apart from being the representative of terrestrial biodiversity, such complexity also makes Yunnan very vulnerable to invasive alien species.

The western portion of Yunnan is generally known as the longitudinal range-gorge region (LRGR) where great mountains and deep valleys run parallel through Yunnan and connect the Indochinese peninsula and the inner area of western China, which has been considered as the terrestrial pathway of biological invasion in Yunnan (He et al., 2005). The eastern

Detecting Non-Local Japanese Pine Sawyers

**2.2 Association with the pine wood nematodes** 

round of infestation (Edwards & Linit, 1992; Naves et al., 2007).

dangerous forest pest by forestry authorities worldwide.

**2.4 The pine wilt disease in China** 

(SFA, 2011) (Fig. 1).

**2.3 Economic importance of** *M. alternatus*

in Yunnan, Southwestern China via Modern Molecular Techniques 71

The pine wood nematode, *Bursaphelenchus xylophilus* (Steiner et Buhrer) (Nematoda: Aphelenchoididae), is a quarantine phytopathogenic organism of conifers indigenous to northern America but casually spread to Eurasia and southern Japan in last century (CABI & EPPO, 1997). The nematode, like other species of genus *Bursaphelenchus*, lives in the vascular tissue of their coniferous hosts, which decreases the transportation of water and resin, and subsequently weakens the hosts and causes a syndrome named the pine wilt disease (Mamiya, 1983). The pathogenicity of *B. xylophilus* varies significantly. In North America, reports on its damages are rarely seen (Wingfield et al., 1986). However, in the vast majority of Japan and China, where *B. xylophilus* is considered as an invasive species, the infestation is often fatal, and has caused catastrophic timber loss (Mamiya, 1988; X.B. Hu et al., 1997). In nature, the relocation of *Bursaphelenchus* nematodes depends on coleopterous vectors, but the association between nematodes and vectors differs with taxa (Linit, 1988). For *B. xylophilus*, the longhorned beetles of genus *Monochamus* are the major vector (Linit et al., 1983; Evans et al., 1996; Kulinich & Orlinskii, 1998), and research has confirmed that *M. alternatus* is the key vector of *B. xylophilus* in eastern Asia (Mamiya & Enda, 1972; Kobayashi et al., 1984). In infested hosts, the immature pine wood nematodes are able to locate the pupae of *M. alternatus* and board into the tracheae, and the newly eclosed adults carry the nematodes when seeking food and new hosts. During the course of feeding and ovipositing, the nematodes detach from the beetles and enter the new hosts through the feeding and ovipositing wounds to initiate a new

There are basically four aspects of economic importance of *M. alternatus*. As a stem-boring coleopteran of the conifers, the direct feeding and ovipositing of the adults damages the tender shoots, needles, and bark of the host, which may weaken the host when a sizable population occurs in a stand. The tunnels inside the host built by the larvae often cause more damage which eventually kills the host and substantially reduces the economic value of the timber (L.P. Wang, 2004). *M. alternatus* spends the entire immature stage in the host, which makes it very difficult to be detected from timber and/or wood packaging materials and can be easily relocated to new habitats via transportation in trading (Haack, 2006). As timber and/or wood packaging materials with *B. xylophilus* can also be relocated (Braasch et al., 2001; Gu et al., 2006), the concealed *M. alternatus* would subsequently introduce the nematodes into new habitats via its dispersal. Hence, *M. alternatus* has been recognized as a

In mainland China, the pine wilt disease was reported for the first time in a small patch of *Pinus thunbergii* near the Sun Yat-sen Mausoleum in Nanjing, Jiangsu Province in 1982 (Y.Y. Wang et al., 1991). Afterwards, the infested area expanded quickly throughout eastern China. From the bulletins released by the SFA (State Forestry Administration) of China, a clear tendency of westward expansion can be observed (SFA, 2004 ~ 2007). During the past two years, some counties in Henan, Shaanxi, and Sichuan provinces in northern, northwestern, and southwestern China also reported infested areas of the pine wilt disease

portion of Yunnan is the western margin of the Yunnan-Guizhou altiplano, where most of the terrain are plains with low hills with an altitude lower than the central portion of Yunnan as well as most of the LRGR (S.Y. Wang & W. Zhang, 2005). The subdued slope of this area also allows non-local organisms to enter Yunnan from the adjacent areas of China. Meanwhile, Yunnan also plays an important role in preventing invasive alien species from entering China, as the mountains lie in northern portion are natural barriers to obstruct the populations of non-local organisms from expanding. Therefore, Yunnan bears a vital strategic function of regional ecosecurity defined by the combination of terrestrial pathway and frontier prevention of biological invasion.

To enhance relevant research in detecting exotic species and/or non-local populations in Yunnan, research on invasive alien species has been conducted to reveal origin, expansion, and the mechanisms of invasion. For cases of invasive insects, researches on two exotic tephritid pests, *Bactrocera dorsalis* (Hendel) and *B. correcta* (Bezzi) have achieved the goals of population recognition and route reestablishment via modern molecular techniques (Shi et al., 2010; Liu, unpublished data). These studies demonstrated that the invasion of the two fruit flies represented the mode of natural and long-term invasion, inhabitation, and expansion. Moreover, the merits of these important research also provided ideas for the research on biological invasion in the new era. We used molecular techniques to detect nonlocal populations of a forest pest in southwestern Yunnan which strongly suggested another possible mode of biological invasion.
