The Bactrocera dorsalis complex This is a large complex of almost 80 morphologically similar species that occur across the Asia-Pacific region. It represents an excellent example of a species complex in which difficulties occur for workers charged with the responsibility of identifying specimens, particularly those resulting from biosecurity surveys.At the forefront, also, is the necessity for researchers to identify and describe these sibling species, using morphology as a key procedure. The degree of divergence in genes that influence external morphological characters is not necessarily representative of the total of all genetic changes that occur during the process of speciation. In fact, the mere existence of sibling species with varying degrees of genetic similarity indicates that there is no consistent relationship between morphological and genetic change at speciation (Lambert & Paterson, 1982). This inherent problem not only raises difficulties for workers identifying species morphologically but also casts doubt on the application of molecular data based on a limited number of genes. The highest density of dorsalis complex species occurs over the Sunda Continental Shelf countries, especially those centred around Peninsular Malaysia, Indonesia (especially Sumatra), Thailand, Vietnam, Cambodia and Borneo. As an example, the number of species per country of the 34 methyl eugenol plus allies subgroup defined below is shown in Table 1. This distribution pattern matches that of the species-rich Indo-Malayan rainforests described by Whitmore (1986) and, with the exception of India, with increasing distance from this centre the numbers decline. Across the genus Bactrocera, the Philippines and Borneo possess a large number of species in common, with the Philippines also possessing its own level of endemism. This situation is also represented in the dorsalis complex, where B. occipitalis and B. papayae are shared, while B. collita is endemic to the Philippines. This situation is most likely a result of the Philippines splitting later from the main centre of speciation. Four species have been recorded in Wallacea, all endemic to that transition zone, i.e. B. floresiae Drew & Hancock, B. infulata Drew & Hancock, B. minuscula Drew & Hancock and B. sulawesiae Drew & Hancock. Further east in Papua New Guinea and related territories, the dorsalis complex is poorly represented. There are no species with dorsalis complex characters in the Pacific Region east of Papua New Guinea. In Australia there are three species, B. cacuminata (Hering), B. endiandrae (Perkins & May) and B. opiliae (Drew & Hardy).

Published as part of Drew, R. A. I. & Hancock, D. L., 2022, Biogeography, Speciation and Taxonomy within the genus Bactrocera Macquart with application to the Bactrocera dorsalis (Hendel) complex of fruit flies (Diptera Tephritidae: Dacinae), pp. 333-360 in Zootaxa 5190 (3) on pages 336-337, DOI: 10.11646/zootaxa.5190.3.2, http://zenodo.org/record/7138151

{"references": ["Lambert, D. M. & Paterson, H. E. H. (1982) Morphological resemblance and its relationship to genetic distance measures. Evolutionary Theory, 5, 291 - 300.", "Whitmore, T. C. (1986) Tropical Rainforests of the Far East. 2 nd Edition. Oxford University Press, Oxford, 352 pp."]}