title: Rapid and repeatable shifts in life-history timing of Rhagoletis pomonella (Diptera: Tephritidae) following colonization of novel host plants in the Pacific Northwestern United States.
abstract: Host shifts of phytophagous insect specialists to novel plants can result in divergent ecological adaptation, generating reproductive isolation and potentially new species. Rhagoletis pomonella fruit flies in eastern North America underwent a host shift ~160 ya from native downy hawthorn (Crataegus mollis) to introduced, domesticated apple (Malus domestica). Divergent selection on diapause phenology related to the earlier fruiting time of apples versus downy hawthorns resulted in partial allochronic reproductive isolation between the fly races. Here, we test for how rapid and repeatable shifts in life-history timing are driving ecological divergence of R. pomonella in the Pacific Northwestern USA. The fly was introduced into the region via larval-infested apples 40-65 ya and now attacks native black hawthorn (Crataegus douglasii) and introduced ornamental hawthorn (Crataegus monogyna), in addition to early- and late-maturing apple varieties in the region. To investigate the life-history timing hypothesis, we used a field-based experiment to characterize the host-associated eclosion and flight activity patterns of adults, and the feeding times of larvae at a field site in Vancouver, Washington. We also assessed the degree to which differences in host-fruiting time generate allochronic isolation among apple-, black hawthorn-, and ornamental hawthorn-associated fly populations. We conclude that host-associated fly populations are temporally offset 24.4% to 92.6% in their seasonal distributions. Our results imply that R. pomonella possesses the capacity for rapid and repeatable shifts in diapause life history to match host-fruiting phenology, which can generate ecologically based reproductive isolation, and potentially biodiversity in the process.
authors.affiliation: Department of Biology Portland State University 1719 SW 10th Ave. Science Building One Portland Oregon 97201.
authors.forename: Monte
authors.initials: M
authors.lastname: Mattsson
authors.affiliation: Department of Biological Sciences University of Notre Dame 100 Galvin Life Sciences Notre Dame Indiana 46556.
authors.forename: Glen R
authors.initials: GR
authors.lastname: Hood
authors.affiliation: Department of Biological Sciences University of Notre Dame 100 Galvin Life Sciences Notre Dame Indiana 46556.
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Feder
authors.affiliation: Department of Biology Portland State University 1719 SW 10th Ave. Science Building One Portland Oregon 97201.
authors.forename: Luis A
authors.initials: LA
authors.lastname: Ruedas
keywords: Allochronic isolation; apple maggot fly; biodiversity; ecological speciation; hawthorn; host race formation; phytophagous insects
references.citation: Bull Entomol Res. 2000 Feb;90(1):77-88
references.pmid: 10948367
references.citation: Proc Natl Acad Sci U S A. 1997 Oct 14;94(21):11417-21
references.pmid: 11038585
references.citation: Nature. 2000 Oct 12;407(6805):739-42
references.pmid: 11048719
references.citation: Evolution. 2000 Oct;54(5):1626-37
references.pmid: 11108590
references.citation: Trends Ecol Evol. 2001 Jul 1;16(7):372-380
references.pmid: 11403870
references.citation: Proc Natl Acad Sci U S A. 1994 Aug 16;91(17):7990-4
references.pmid: 11607491
references.citation: Annu Rev Entomol. 2002;47:93-122
references.pmid: 11729070
references.citation: Annu Rev Entomol. 2002;47:773-815
references.pmid: 11729091
references.citation: Philos Trans R Soc Lond B Biol Sci. 2002 Apr 29;357(1420):471-92
references.pmid: 12028786
references.citation: Genetica. 2002 Nov;116(2-3):251-67
references.pmid: 12555783
references.citation: Proc Natl Acad Sci U S A. 2003 Sep 30;100(20):11490-3
references.pmid: 14504399
references.citation: Evolution. 2005 Sep;59(9):1953-64
references.pmid: 16261733
references.citation: Mol Ecol. 2008 Jan;17(1):157-66
references.pmid: 17850269
references.citation: J Evol Biol. 2007 Nov;20(6):2101-12
references.pmid: 17956381
references.citation: J Evol Biol. 2012 May;25(5):961-71
references.pmid: 22435643
references.citation: Evolution. 2012 Nov;66(11):3632-41
references.pmid: 23106724
references.citation: J Insect Sci. 2012;12:124
references.pmid: 23451979
references.citation: J Evol Biol. 2013 Nov;26(11):2359-68
references.pmid: 24016035
references.citation: Ecol Lett. 2015 Aug;18(8):817-25
references.pmid: 26077935
references.citation: Oecologia. 1995 Apr;101(4):416-425
references.pmid: 28306956
references.citation: Evolution. 1969 Jun;23(2):237-251
references.pmid: 28562891
references.citation: Evolution. 1977 Jun;31(2):405-420
references.pmid: 28563224
references.citation: Evolution. 1985 Mar;39(2):244-259
references.pmid: 28564221
references.citation: Evolution. 1999 Feb;53(1):187-200
references.pmid: 28565200
references.citation: Evolution. 1999 Oct;53(5):1446-1457
references.pmid: 28565574