Intraspecific trait variation across elevation predicts a widespread tree species' climate niche and range limits

Abstract

Global change is widely altering environmental conditions which makes accurately predicting species range limits across natural landscapes critical for conservation and management decisions. If climate pressures along elevation gradients influence the distribution of phenotypic and genetic variation of plant functional traits, then such trait variation may be informative of the selective mechanisms and adaptations that help define climatic niche limits. Using extensive field surveys along 16 elevation transects and a large common garden experiment, we tested whether functional trait variation could predict the climatic niche of a widespread tree species (Populus angustifolia) with a double quantile regression approach. We show that intraspecific variation in plant size, growth, and leaf morphology corresponds with the species' total climate range and certain climatic limits related to temperature and moisture extremes. Moreover, we find evidence of genetic clines and phenotypic plasticity at environmental boundaries, which we use to create geographic predictions of trait variation and maximum values due to climatic constraints across the western US.Overall, our findings show the utility of double quantile regressions for connecting species distributions and climate gradients through trait-based mechanisms. We highlight how new approaches like ours that incorporate genetic variation in functional traits and their response to climate gradients will lead to a better understanding of plant distributions as well as identifying populations anticipated to be maladapted to future environments. K E Y W O R D Sadaptation, climate range, ecological niche models, elevation gradient, functional traits, intraspecific variation, phenotypic plasticity, quantile regression

Stacked distribution models predict climate-driven loss of variation in leaf phenology at continental scales

“…Further, genotypes from the trailing-edge population are an important source of heat and water stress-tolerant individuals, making them critically important for conservation. If the loss of genetic variation in these populations is non-random (i.e., driven by selection) as our models suggest, and genetic variation in functional traits supports variation in ecosystem functions on the landscape 22 , 35 , 48 , then climate driven loss of genetic variation may be an important driver of ecosystem disassembly.…”

“…Though important, it is problematic that functional trait distribution has received little attention at broad spatial scales 17 , 18 . Though there has been an increase in research examining spatial genetic variation generally 19 , less is known about the ecological and evolutionary responses of functional traits to environmental change across species’ ranges or how traits may mediate or constrict population responses to climate change 16 , 20 – 22 . Some of the strongest responses to environmental change have occurred in traits like survival, fecundity, or phenology 23 that influence many abiotic and biotic components of ecosystems 24 , 25 .…”

Distinct Cold Acclimation of Productivity Traits in Arabidopsis thaliana Ecotypes

“…Reich [68] proposed that integration at the whole-plant level of how traits respond to the environment may create a generalizable response. Combining genomic/transcriptomic information with information on the response of functional traits may further aid in gaining a holistic understanding of plant response [69]. It was proposed that an essential next step in the quest to understand how plants respond to different environments is the identification of underlying themes of how genotypes interact with the environment [70].…”

Reciprocal transplants reveal asymmetric local adaptation of Himalayan Rhododendron approaching elevational range limit

“…Results from these studies have been diverse. Plants sampled from different elevations may not differ at all (Fetched et al, 2000) or, when they do differ, the divergence can be mostly in heritable traits (Clausen & Hiesey, 1958), in plasticity (Pfennigwerth et al, 2017), or in both (Van Nuland et al, 2020).…”