Cryptic genetic variation and adaptation to waterlogging in Caledonian Scots pine, Pinus sylvestris L.

Abstract

Local adaptation occurs as the result of differential selection among populations. Observations made under common environmental conditions may reveal phenotypic differences between populations with an underlying genetic basis; however, exposure to a contrasting novel environment can trigger release of otherwise unobservable (cryptic) genetic variation. We conducted a waterlogging experiment on a common garden trial of Scots pine, Pinus sylvestris (L.), saplings originating from across a steep rainfall gradient in Scotland. A flood treatment was maintained for approximately 1 year; physiological responses were gauged periodically in terms of photochemical capacity as measured via chlorophyll fluorescence. During the treatment, flooded individuals experienced a reduction in photochemical capacity, F v /F m, this reduction being greater for material originating from drier, eastern sites. Phenotypic variance was increased under flooding, and this increase was notably smaller in saplings originating from western sites where precipitation is substantially greater and waterlogging is more common. We conclude that local adaptation has occurred with respect to waterlogging tolerance and that, under the flooding treatment, the greater increase in variability observed in populations originating from drier sites is likely to reflect a relative absence of past selection. In view of a changing climate, we note that comparatively maladapted populations may possess considerable adaptive potential, due to cryptic genetic variation, that should not be overlooked.

Heritable genetic variation but no local adaptation in a pine-ectomycorrhizal interaction

“…However, between the most eastern and most western populations, there is a lag of over 2 weeks in peak pollen production, which would limit gene flow between the geographic extremes (Whittet et al, 2017). Local adaptation has been demonstrated in these populations along the west-to-east gradient for a number of traits, including needle morphology (Donnelly et al, 2016), response to waterlogging (Donnelly et al, 2018), photochemical capacity (Salmela et al, 2011), and spring phenology (Salmela et al, 2013). Because mycorrhizal fungal communities in this pinewood system have also been shown to vary longitudinally along a rainfall gradient (Jarvis et al, 2013), we believe that the absence of local adaptation we found is due to a lack of selection for mycorrhizal response rather than the homogenizing effects of gene flow.…”

Does the definition of a novel environment affect the ability to detect cryptic genetic variation?

“…While individual publications show evidence of CGV (Badyaev, 2005;Donnelly et al, 2018;Ledón-Rettig et al, 2009McGuigan et al, 2011;Rohner et al, 2013;Rutherford & Lindquist, 1998), evidence synthesis is equivocal (Noble et al, 2019;Rowiński & Rogell, 2017;Wood & Brodie, 2015. Here, we conducted a meta-analysis using systematic criteria for defining novel environments to answer two questions: (1) Does total additive genetic variation increase in novel environments versus ancestral environments?…”

Phenotypic Plasticity & Evolution

“…Collectively, the hidden reaction norms of different genotypes express 'cryptic genetic variation' (Figure 15.1). Such cryptic genetic variation has been suggested to represent a store of variability that can be revealed in novel environments or genetic backgrounds Moczek 2008;Donnelly et al 2018;Zheng et al 2019;Pilakouta et al 2020). Zan and Carlborg (2020) investigated the organization of 130 yeast growth regulation genes in response to 20 different growth media.…”