Geographic and ecological dimensions of host plant associated genetic differentiation and speciation in the Rhagoletis cingulata (Diptera: Tephritidae) sibling species group

Authors: DOELLMAN, MEREDITH - UNIVERSITY OF NOTRE DAME; SCHULER, HANNES - UNIVERSITY OF NOTRE DAME; SAINT JEAN, GILBERT - UNIVERSITY OF NOTRE DAME; HOOD, GLEN - UNIVERSITY OF NOTRE DAME; EGAN, SCOTT - UNIVERSITY OF NOTRE DAME; POWELL, THOMAS H.Q. - UNIVERSITY OF NOTRE DAME; GLOVER, MARY - UNIVERSITY OF NOTRE DAME; BRUZZESE, DANIEL - UNIVERSITY OF NOTRE DAME; SMITH, JAMES - MICHIGAN STATE UNIVERSITY; Yee, Wee; GOUGHNOUR, ROBERT - WASHINGTON STATE UNIVERSITY EXTENSION SERVICE; RULL, JUAN - EXPERIMENTAL PLANT FOR INDUSTRIAL MICROBIOLOGICAL PROCESSES(PROIMI); ALUJA, MARTIN - INSTITUTE DE ECOLOGIA - MEXICO; FEDER, JEFFREY - UNIVERSITY OF NOTRE DAME

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/27/2019
Publication Date: 9/29/2019
Citation: Doellman, M.M., Schuler, H., Saint Jean, G., Hood, G.R., Egan, S.P., Powell, T., Glover, M.M., Bruzzese, D.J., Smith, J.J., Yee, W.L., Goughnour, R.B., Rull, J., Aluja, M., Feder, J. 2019. Geographic and ecological dimensions of host plant associated genetic differentiation and speciation in the Rhagoletis cingulata (Diptera: Tephritidae) sibling species group. Insects. 10(9). Article 275. https://www.mdpi.com/2075-4450/10/9/275.
DOI: https://doi.org/10.3390/insects10090275

Interpretive Summary: Ascertaining the causes of adaptive radiation is central to understanding how new species arise and come to vary with their resources, but mechanisms for speciation remain elusive. Personnel at the USDA-ARS laboratory in Wapato, WA, University of Notre Dame, Notre Dame, IN, Wayne State University, Detroit, MI, Rice University, Houston, TX, Binghamton University, Binghamton, NY, Instituto de Ecologia, Veracruz, Mexico, and Division Control Biologico de Plagas, Argentina characterized patterns of genetic variation and reproductive isolation for various species of cherry fruit flies to assess the significance of ecology, geography, and non-adaptive processes for their divergence. Our results showed no evidence for reproductive isolation between two populations of allopatric species, while DNA analyses suggested strong ecologically-based reproductive isolation among sympatric species infesting different host plants. Thus, ecology associated with sympatric host shifts may be one prime initial drivers of the radiation of cherry fruit fly species

Technical Abstract: Ascertaining the causes of adaptive radiation is central to understanding how new species arise and come to vary with their resources. The ecological theory posits adaptive radiation via divergent natural selection associated with novel resource use; an alternative suggests character displacement following speciation in allopatry and then secondary contact of reproductively isolated but ecologically similar species. Discriminating between hypotheses therefore requires distinguishing a key role for ecological diversification in initiating speciation versus a secondary role in facilitating co-existence. Here, we characterize patterns of genetic variation and postzygotic reproductive isolation for tephritid fruit flies in the Rhagoletis cingulata sibling species group to assess the significance of ecology, geography, and non-adaptive processes for their divergence. Our results support the ecological theory: no evidence for intrinsic postzygotic reproductive isolation was found between two populations of allopatric species, while nuclear-encoded microsatellites implied strong ecologically-based reproductive isolation among sympatric species infesting different host plants. Analysis of mitochondrial DNA suggested, however, that cytoplasmic-related reproductive isolation may also exist between two geographically isolated populations within R cingulata. Thus, ecology associated with sympatric host shifts and cytoplasmic effects possibly associated with an endosymbiont may be the prime initial drivers of the radiation of the R. cingulata group