Sympatric Speciation Flies (Rhagoletis pomonella) (1) Larvae develop in hawthorns (Crataegus) Native to NE U.S. (2) Larvae develop in apples (Pyrus) Apples introduced c. 300 ya; apple flies became a pest c. 150 ya. H 0 : The flies belong to the same species; there is phenotypic plasticity in use of hosts. H 1 : Speciation has occurred; each species of fly adapted to one host species. Since hawthorns and apples are both within the range of Rhagoletis, this would represent an example of sympatric speciation.

Flies using the two types of fruit cannot be distinguished morphologically (cryptic). But, evidence of lineage splitting: 1. Allele frequency differs for 6 different proteins; therefore can be distinguished genetically. 2. Flies imprint on fruit from which they developed. –Mating takes place on the fruit. –Provides some degree of physical segregation. –Only c. 2% of matings are between misimprinted flies.

Flies are diverging because of natural selection Selective agent = timing of fruit ripening. Apples ripen “early.” Larvae in apples –Selected to develop slowly (present in some Mexican fly populations). –Prevents emergence of adults prior to winter. Hawthorns ripen ca. 3 weeks later than apples. Larvae in hawthorn fruit –Selected to develop rapidly. –Enables pupation prior to winter. A few mistakes are made: speciation nearing completion.

Allopatric Speciation by dispersal Representative Hawaiian Drosophila diversity

Aspidoscelis carmenensis A. picta A. danheimae A. franciscensis A. espiritensis A speciation problem

Unresolved: maybe not species? Grismer, L. Lee Phylogeny, taxonomy, and biogeography of Cnemidophorus hyperythrus and C. ceralbensis (Squamata: Teiidae) In Baja California, Mexico