Genotypic variation and plasticity in climate-adaptive traits after range expansion and fragmentation of red spruce (Picea rubensSarg.)

Abstract

Shifting range limits are predicted for many species as the climate warms. However, the rapid pace of climate change will challenge the natural dispersal capacity of long-lived, sessile organisms such as forest trees. Adaptive responses of populations will, therefore, depend on levels of genetic variation and plasticity for climate-responsive traits, which likely vary across the range due to expansion history and current patterns of selection. Here, we study levels of genetic and plastic variation for phenology and growth traits in populations of red spruce ( Picea rubens ), from the range core to the highly fragmented trailing edge. We measured more than 5000 offspring sampled from three genetically distinct regions (core, margin and edge) grown in three common gardens replicated along a latitudinal gradient. Genetic variation in phenology and growth showed low to moderate heritability and differentiation among regions, suggesting some potential to respond to selection. Phenology traits were highly plastic, but this plasticity was generally neutral or maladaptive in the effect on growth, revealing a potential liability under warmer climates. These results suggest future climate adaptation will depend on the regional availability of genetic variation in red spruce and provide a resource for the design and management of assisted gene flow. This article is part of the theme issue ‘Species’ ranges in the face of changing environments (Part II)’.

Evidence of climate‐driven selection on tree traits and trait plasticity across the climatic range of a riparian foundation species

“…Specifically, we found trees sourced from hotter environments were significantly less plastic in height and DRC compared to the colder provenance populations, but had higher plasticity in bud set and bud flush (Figure 3). These plasticity-climate relationships partially agree with another study where populations of red spruce from warmer climates had greater plasticity in both bud break and growth compared to cold-adapted populations (Prakash et al, 2022). Our results may be an example of a multivariate plasticity response, where plasticity in one trait can affect the plasticity in another trait (Nielsen & Papaj, 2022).…”

From common gardens to candidate genes: exploring local adaptation to climate in red spruce

“…We used height growth here as a proxy of early‐life fitness to demonstrate local adaptation (Blanquart et al ., 2013 ), and other work by our group indicates that genetic divergence in adaptive phenology traits (e.g. bud break and bud set) likely underlie these growth differences (Prakash et al ., 2022 ). Another recent study of red spruce provenances planted at five different trial sites in eastern Canada found a similar result in adult trees, showing that two fitness traits (height and diameter at breast height (DBH)) were correlated with climate transfer distance (Li et al ., 2020 ).…”

“…According to the results of the different GEA procedures we used in this study, the FPA gene was one of the strongest selection candidates, which regulates flowering time in Arabidopsis thaliana via the autonomous pathway, independent of daylength (Schomburg et al ., 2001 ). In common garden studies by our group, we have shown strong genetic differentiation in bud set phenology traits in red spruce, including at broad latitudinal scales (Prakash et al ., 2022 ) and at fine scales between genotypes sourced from low vs high elevations on the same mountain that experience essentially identical photoperiod regimes (Butnor et al ., 2019 ; Verrico, 2021 ). This could suggest that red spruce phenology is driven by temperature in addition to, or in interaction with, photoperiod, consistent with results from growth chamber experiments in white spruce (Hamilton et al ., 2016 ).…”

Understanding the biology of species' ranges: when and how does evolution change the rules of ecological engagement?

“…at soft limits) to climate change should largely be determined by levels of heritable variation found throughout the geographical range. Prakash et al [112] consider the case of red spruce tested in replicated common gardens across the latitudinal range of the species, demonstrating that growth and phenological responses have low to moderate heritabilities that could support in situ adaptation, albeit to varying extents across their range. However, while plastic changes in phenology were possible, they often had a maladaptive effect on growth, suggesting that existing genetic variation within populations may actually limit climate adaptation in red spruce.…”