Peripheral Isolates as Sources of Adaptive Diversity under Climate Change

Abstract

As climate change progresses, there is increasing focus on the possibility of using targeted gene flow (TGF, the movement of pre-adapted individuals into declining populations) as a management tool. Targeted gene flow is a relatively cheap, low-risk management option, and will almost certainly come into increased use over the coming decades. Before such action can be taken, however, we need to know where to find pre-adapted individuals. We argue that, for many species, the obvious place to look for this diversity is in peripheral isolates: isolated populations at the current edges of a species' range. Both evolutionary and ecological considerations suggest that the bulk of a species' adaptive variation may be contained in the total set of these peripheral isolates. Moreover, by exploring both evolutionary and ecological perspectives it becomes clear that we should be able to assess the potential value of each isolate using remotely sensed data and three measurable axes of variation in patch traits: population size, connectivity, and climatic environment. Locating the "sweet spot" in this trait space, however, remains a challenge. Throughout, we illustrate these ideas using Australia's Wet Tropics rainforests as a model system.

Adjusting to climate: Acclimation, adaptation and developmental plasticity in physiological traits of a tropical rainforest lizard

“…We cannot, of course, rule out transgenerational plasticity (Salinas & Munch 2012), but the weak role of developmental plasticity in our data coupled with the lack of maternal effects on the measured traits (Martins et al 2018) suggests that such effects are likely modest. This evidence of evolved variation in the climate-relevant traits of a terrestrial vertebrate lends weight to the idea of incorporating evolutionary processes into management strategies aimed at conserving species threatened by climate change (Hampe & Petit 2005;Aitken & Whitlock 2013;Kelly & Phillips 2016;Macdonald et al 2017b).…”

“…Despite the constraints around prediction, knowing that traits can shift rapidly, and that there is adaptive variation to be found across populations is encouraging. As well as revealing a natural capacity for tropical ectotherms to adapt, it also gives us options for using targeted gene flow to accelerate that process (Weeks et al 2011;Aitken & Whitlock 2013;Kelly & Phillips 2016;Macdonald et al 2017b). Tropical ectotherms may be particularly imperiled by climate change, but many of these species are likely to have at least some capacity to adjust.…”

Aneuploidy in yeast: Segregation error or adaptation mechanism?

“…Hybridisation should automatically increase the frequency of aneuploids in these environments (whether aneuploidy is beneficial or not; Rogers et al, ). At the same time, populations existing at the periphery where ecological conditions are more challenging are more likely to experience stress (Macdonald, Llewelyn, Moritz, & Phillips, ). We suggest that the convergence of these processes—hybridisation and aneuploidy—and the increased chance for them to occur at the same time and place under environmental stress may give aneuploid hybrid genomes a transient solution to adaptation.…”

Geographic variation in adult and embryonic desiccation tolerance in a terrestrial-breeding frog

“…With climate change progressing rapidly, there is increasing focus on conservation of range-edge populations that may harbour the bulk of a species' adaptive variation (e.g. Rehm et al 2015;Macdonald et al 2017…”