Shifting Conservation Perspectives of Local Adaptation along the Continuum From Population Declines to Population Reintroductions

In order to remain adaptive, I will argue that salmonid conservation programs need to shift from preserving local adaptations to manipulating them as populations decline and approach extirpation. Currently, much conservation research focuses on genetic changes that occur via genetic drift and inbreeding as populations become fragmented and small. Yet environmental selective regimes may dramatically shift as populations change from being abundant-and-stable to small-and-declining. These selective regime shifts imply that locally adaptive population features - often the targets for conservation efforts - will not remain static, nor will they be necessarily replaceable. Thus when environmental selective regime shifts are sufficiently strong to result in local population extirpation in the wild, species re-establishment may depend on foreign populations with adaptations related to the new environmental regime, or mixed populations. Key conservation questions therefore include: (i) At what point during local population decline do the benefits of population mixing (i.e. preventing extirpation) outweigh the costs (e.g. loss of local adaptation)? (ii) How much environmental change can still allow for reintroduction of the local population, and when should different foreign populations or mixed populations be favoured? Empirical examples from Canadian Atlantic salmon populations are used to address these questions, with a focus on balancing preservationist and restorationist goals in conservation.