Data from: 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

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.