Cytogenetic and symbiont analysis of five members of the B. dorsalis complex (Diptera, Tephritidae): no evidence of chromosomal or symbiont-based speciation events

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.

The chromosomes and the mitogenome of Ceratitis fasciventris (Diptera: Tephritidae): two genetic approaches towards the Ceratitis FAR species complex resolution

“…capitata , are congruent with the concept that chromosome rearrangements, mainly paracentric inversions, are implicated in species differentiation in Diptera which is substantiated by comparative cytogenetic and genomic analyses in Drosophila and mosquitoes 46–54, 56–58 . In accordance with the above notion, comparisons among tephritids, reveal that inversions and/or transpositions on specific chromosomes, including chromosomes 3 and 5, differentiate species and support the potential value of chromosome rearrangements as phylogenetic and diagnostic markers among closely related species 70, 75–78, 80, 111 .…”

“…Likewise, the first complete mitochondrial sequence of a member of the FAR complex can be used as reference for future sequence comparisons among FAR species, aiming to reveal polymorphic mitochondrial regions suitable for the development of molecular diagnostic markers. The fact that the insects used originate from a well-characterized established colony eliminates possible problems resulting from sampling and species misidentification 80 and supports the use of both cytogenetic and mitochondrial present results as reference material.…”

“…Polytene chromosome maps are available for 11 tephritid species belonging to five genera 65–79 . Comparative analyses among most of them revealed specific CRs that are diagnostic at the genus, subgenus and species level 70, 75–78, 80 , supporting the possible involvement of CRs in speciation.…”

“…These changes could have been derived from consecutive overlapping inversions resulting in both inverted and transposed chromosome fragments 119 . Comparative analyses of polytene chromosomes among several tephritids showed that CRs are restricted to specific chromosome arms, mainly to the 3L and 5L arms 70, 76–78, 80 .

Figure 4Comparison of the 3L polytene chromosome arms of Ceratitis fashiventris and Ceratitis capitata . ( a ) The 3L polytene chromosome arm of C .

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Cytogenetic Analysis of the South American Fruit Fly Anastrepha fraterculus (Diptera:Tephritidae) Species Complex: Construction of Detailed Photographic Polytene Chromosome Maps of the Argentinian Af. sp.1 Member

“…ludens and C . capitata has been established based on both their polytene chromosome banding pattern similarities and/or in situ hybridization of selected probes [ 11 , 13 , 68 – 70 , 75 , 76 , 105 – 107 ]. These studies showed that the species are differentiated by fixed chromosomal rearrangements, mainly paracentric inversions, and are characterized by transpositions on specific chromosomes.…”