Nature 336, 66 - 67 (03 November 1988); doi:10.1038/336066a0

Heritable divergence of Rhagoletis pomonella host races by seasonal asynchrony

D. Courtney Smith

Department of Biology, 201 South Biology, University of Utah, Salt Lake City, Utah 84112, USA

Possible mechanisms for animal speciation in the absence of geographic isolation remain controversial. Univoltine flies of the Rhagoletis pomonella sibling species group of larval fruit parasites have been cited^1–5 as prime examples of sympatric speciation through divergence in host plant association. The recent emergence of several populations of R. pomonella associated with plants other than the fly's native hawthorn host has been attributed to the effects described by a model^2–4 of sympatric host-race formation involving host recognition and survival genes; however, direct genetic evidence of biologically meaningful differentiation among putative host races has been lacking. In contrast, the potential importance of seasonal asynchrony (of flies adapted to host plants with different fruiting phenologies) in initial restriction of gene flow has been largely undervalued. Here I report heritable divergence in seasonal emergence of R. pomonella flies collected from sympatric populations on three host plant species in Illinois, in the United States.

References

1.	Bush, G. L. Bull. Mus. comp. Zool. Harv. 134, 431−562 (1966).
2.	Bush, G. L. Evolution 23, 237−251 (1969).
3.	Bush, G. L. in Genetic Mechanisms of Specialion in Insects (ed. White, M. J. D.) 3−23 (Australian and New Zealand Book, Sydney, 1974).
4.	Bush, G. L. in Evolutionary Strategies of Parasitic Insects and Mites (ed. Price, P. W.) 187−206 (Plenum, London, 1975).
5.	Bush, G. L. & Diehl, S. R. in Insect-Plant Relationships (eds Visser, J. H. & Minks, A. K.) 297−305 (Pudoc, Wageningen, 1982).
6.	Smith, D. C. J.N.Y. ent. Soc. (in the press).
7.	Tauber, M. J., Tauber, C. A. & Masaki, S. Seasonal Adaptations of Insects (Oxford, New York, 1986).
8.	Jaenike, J. Am. Nat. 117, 830−834 (1981). | Article |
9.	Diehl, S. R. & Bush, G. L. A. Rev. Ent. 29, 471−504 (1984). | Article |
10.	Reissig, W. H. Can. Ent. 109, 631−634 (1977).
11.	Opp, S. B. & Prokopy, R. J. Fla. Ent. 70, 449−457 (1987).
12.	Pickett, A. D. & Neary, M. E. Scient. Agric. 20, 551−556 (1940).
13.	Reissig, W. H. & Smith, D. C. A. ent. Soc. Am. 71, 155−159 (1978).
14.	Futuyma, D. J. & Mayer, G. C. Syst. Zool. 29, 254−271 (1980).
15.	Smith, D. C. dissertation, Univ. Illinois (1986).
16.	Slatkin, M. A. Rev. Ecol. Syst. 16, 393−430 (1985).
17.	Paterson, H. E. H. S. Afr. J. Sci. 77, 113−119 (1981).
18.	Futuyma, D. J. & Peterson, S. C. A. Rev. Ent. 30, 217−238 (1985). | Article |
19.	McPheron, B. A., Smith, D. C. & Berlocher, S. H. Genetics 119, 445−451 (1988).