The oriental fruitfly Bactrocera dorsalis s.s. in East Asia: disentangling the different forces promoting the invasion and shaping the genetic make-up of populations

Abstract

The Oriental fruit fly, Bactrocera dorsalis sensu stricto, is one of the most economically destructive pests of fruits and vegetables especially in East Asia. Based on its phytophagous life style, this species dispersed with the diffusion and implementation of agriculture, while globalization allowed it to establish adventive populations in different tropical and subtropical areas of the world. We used nine SSR loci over twelve samples collected across East Asia, i.e. an area that, in relatively few years, has become a theatre of intensive agriculture and a lively fruit trade. Our aim is to disentangle the different forces that have affected the invasion pattern and shaped the genetic make-up of populations of this fruit fly. Our data suggest that the considered samples probably represent well established populations in terms of genetic variability and population structuring. The human influence on the genetic shape of populations and diffusion is evident, but factors such as breeding/habitat size and life history traits of the species may have determined the post introduction phases and expansion. In East Asia the origin of diffusion can most probably be allocated in the oriental coastal provinces of China, from where this fruit fly spread into Southeast Asia. The spread of this species deserves attention for the development and implementation of risk assessment and control measures.

Gene flow and genetic structure of Bactrocera carambolae (Diptera, Tephritidae) among geographical differences and sister species, B. dorsalis, inferred from microsatellite DNA data

“…Moreover, this area is important for the cultivation of star fruit and is a center for transportation to other cities and countries. The homogeneous genetic pattern of Bactrocera carambolae in native areas is similar to Bactrocera dorsalis collected from neighboring countries, including Thailand, Laos, and Cambodia (Aketarawong et al 2007, 2014a, Schutze et al 2012). Both not having limitations on human migration and the intensive cultivation of similar host plants could enhance gene flow, shaping genetic homogeneity among flies from nearby countries.…”

“…These populations were collected from the known distributions of Bactrocera dorsalis (http://www.cabi.org/isc/datasheet/17685) and characterized as Bactrocera dorsalis using the same methods described before (Table 1). One population is from Ratchaburi, Thailand (RB), which is a representative source of Bactrocera dorsalis in Southeast Asia (Aketarawong et al 2007, 2014a). Another is from the northern part of Thailand, Chang Mai (CM).…”

“…The other was collected from Kaohsiung, Taiwan (KS). This sample is supposed to have been introduced from mainland China and has become an isolated population (Aketarawong et al 2007, 2014a). …”

“…Despite being an important pest, knowledge of molecular ecology concerning species status and pest management is needed. There are no previous studies, except multilocus phylogeny (Boykin et al 2014), comparing it to closely related species such as Bactrocera dorsalis (Hendel) (Aketarawong et al 2007, 2011, 2014a, 2014b, Khamis et al 2009, Wan et al 2011, Shi et al 2012, Schutze et al 2012, Krosch et al 2013). …”

“…Likewise, using the genetic cluster approach based on microsatellite data can resolve intra- and interspecific relationships. Several microsatellite markers for invasive tephritid fruit flies were therefore established for studying population genetics in different geographical regions to infer colonization process (e.g., Ceratitis capitata (Bonizzoni et al 2001, 2004, Meixer et al 2002), Bactrocera dorsalis (Aketarawong et al 2007, 2014a, Khamis et al 2009, Wan et al 2011, Shi et al 2012), Zeugodacus cucurbitae (Coquillett) (Virgilio et al 2010, Wu et al 2011), Bactrocera oleae (Gmelin) (Nardi et al 2005, Zygoridis et al 2009, Dogaç et al 2013)). In addition, established markers were used for solving species status in members of species complexes.…”