Abstract
The Bactrocera dorsalis species complex, currently comprising about 90 entities has received much attention. During the last decades, considerable effort has been devoted to delimiting the species of the complex. This information is of great importance for agriculture and world trade, since the complex harbours several pest species of major economic importance and other species that could evolve into global threats. Speciation in Diptera is usually accompanied by chromosomal rearrangements, particularly inversions that are assumed to reduce/eliminate gene flow. Other candidates currently receiving much attention regarding their possible involvement in speciation are reproductive symbionts, such as Wolbachia, Spiroplasma, Arsenophonus, Rickettsia and Cardinium. Such symbionts tend to spread quickly through natural populations and can cause a variety of phenotypes that promote pre-mating and/or post-mating isolation and, in addition, can affect the biology, physiology, ecology and evolution of their insect hosts in various ways. Considering all these aspects, we present: (a) a summary of the recently gained knowledge on the cytogenetics of five members of the Bactrocera dorsalis complex, namely Bactrocera dorsalis s.s., Bactrocera invadens, Bactrocera philippinensis, Bactrocera papayae and Bactrocera carambolae, supplemented by additional data from a Bactrocera dorsalis s.s. colony from China, as well as by a cytogenetic comparison between the dorsalis complex and the genetically close species, Bactrocera tryoni, and, (b) a reproductive symbiont screening of 18 different colonized populations of these five taxa. Our analysis did not reveal any chromosomal rearrangements that could differentiate among them. Moreover, screening for reproductive symbionts was negative for all colonies derived from different geographic origins and/or hosts. There are many different factors that can lead to speciation, and our data do not support chromosomal and/or symbiotic-based speciation phenomena in the taxa under study.
Highlights
The Bactrocera dorsalis species complex currently consists of approximately 90 entities, whose limits are not fully resolved (Drew and Hancock 1994, Drew and Romig 2013, Krosch et al 2013, Boykin et al 2014, Schutze et al 2015)
As it has been shown by different studies (Gilchrist et al 2012; Parreño et al 2014, Zygouridis et al 2014), lab colonization is accompanied by an adaptation process including severe bottlenecks, hitch-hiking effects and extended inbreeding
Focusing on the better studied Tephritidae species (C. capitata) and species of two genera that are phylogenetically close to each other (Bactrocera and Dacus), polytene chromosome comparisons performed either in older studies or in the present study have revealed specific chromosomal rearrangements (CRs) that are diagnostic in genus, subgenus and species level
Summary
The Bactrocera dorsalis species complex currently consists of approximately 90 entities, whose limits are not fully resolved (Drew and Hancock 1994, Drew and Romig 2013, Krosch et al 2013, Boykin et al 2014, Schutze et al 2015). Recent studies have shown that efforts to resolve complex species status require multidisciplinary approaches (De Queiroz 2007, Schlick-Steiner et al 2010), wellcharacterized material and extended sampling (Schutze et al 2012, Krosch et al 2013, Boykin et al 2014) Such approaches have been followed in other Tephritidae genera where species delimitation of species complexes is an important concern, such as in Anastrepha (Selivon et al 2005, Vera et al 2006, Cáceres et al 2009). These were B. dorsalis s.s., B. papayae, B. philippinensis, B. invadens and B. carambolae
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