Empirical Evidence for Complex Source-Sink Dynamics with Alternative States in a Butterfly Metapopulation

Abstract

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Geographic mosaics of species' association: a definition and an example driven by plant–insect phenological synchrony

“…We write ''tentative'' because the expectation of fitness on Ctor is reduced, to an unknown extent, by the existence of multiple behavioral adaptations to Psem, for example in geotaxis and clutch size . Despite this caveat, the hindcast matches observation: the mean rate of population growth was faster on Ctor in logged clearings than on Psem in undisturbed patches, and densities of emerging adults were higher in clearings , Boughton 1999. As hindcast, the anthropogenic habitat was more suitable for the insects than the traditional habitat.…”

“…Insects attempting to host-shift to Ctor at Psem-using sites would therefore encounter a phenological barrier (cf. Boughton 1999). These data identify a source of spatially variable natural selection on insect diet that operated across all seven sites in the directions expected if it were to drive the geographic mosaic of species' association.…”

“…Host shifts are known to be important precursors of phylogenetic diversification in butterflies (Nylin andJanz 2009, Fordyce 2011), and Melitaeine butterflies, the group to which our study insect, Euphydryas editha, belongs, typically undergo frequent host shifts . Melitaeines, especially Melitaea cinxia and E. editha, have proven amenable to field investigations of their relationships with host plants, a topic on which considerable information has accumulated (Thomas 1986, Singer et al 1988, Boughton 1999, Hanski 1999, Kuussaari et al 2000, Hanski and Singer 2001, Hellmann 2002, Van Nouhuys et al 2003, Ehrlich and Hanski 2004, Singer and Parmesan 2010.…”

“…E. editha is an insect of sedentary habit (Ehrlich 1961, Gilbert and Singer 1973, Harrison et al 1988, Boughton 1999) distributed in isolated populations and metapopulations across the western United States, western Canada, and northwestern Baja California (Parmesan 1996, Singer andWee 2005). At montane sites such as those in this study, E. editha has a single generation per year.…”

“…An E. editha larva feeding on a senescent plant is not necessarily doomed; even first-instar larvae have some ability to leave their natal host and search for another (Hellmann 2002), and this ability improves in succeeding instars. Nonetheless, E. editha larvae do frequently die from phenological asynchrony with their annual hosts (Weiss et al 1988, Moore 1989, Boughton 1999, Singer and Parmesan 2010.…”