Gene Frequency Shift in Relict Abies pinsapo Forests Associated with Drought-Induced Mortality: Preliminary Evidence of Local-Scale Divergent Selection

Irene Cobo-Simón,Juan Carlos Linares,José Ignacio Seco,Francisco Javier Gallego,Jill Wegrzyn,Belén Méndez-Cea

doi:10.3390/f12091220

Irene Cobo-Simón, Juan Carlos Linares + Show 4 more

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https://doi.org/10.3390/f12091220

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Abstract

Current climate change constitutes a challenge for the survival of several drought-sensitive forests. The study of the genetic basis of adaptation offers a suitable way to understand how tree species may respond to future climatic conditions, as well as to design suitable conservation and management strategies. Here, we focus on selected genetic signatures of the drought-sensitive relict fir, Abies pinsapo Boiss. Field sampling of 156 individuals was performed in two elevation ecotones, characterized by widespread A. pinsapo decline and mortality. The DNA from dead trees was investigated and compared to living individuals, accounting for different ages and elevations. We studied the genes gated outwardly-rectifying K+ (GORK) channel and Plasma membrane Intrinsic Protein (PIP1) aquaporin, previously related to drought response in plant model species, to test whether drought was the main abiotic factor driving the decline of A. pinsapo forests. A combination of linear regression and factor models were used to test these selection signatures, as well as a fixation index (Fst), used here to analyze the genetic structure. The results were consistent among these approaches, supporting a statistically significant association of the GORK gene with survival in one of the A. pinsapo populations. These results provide preliminary evidence for the potential role of the GORK gene in the resilience to drought of A. pinsapo.

Highlights

Changes in the environment occur so fast that species’ adaptive capacities may be overcome [1,2,3]
Survival-related analyses were only based on the gated outwardly-rectifying K+ (GORK) gene (Tables 1, 2, and S1)
Our results suggest that the possible local adaptation observed in C would be related to conditional neutrality in the GORK gene, which would be advantageous in A. pinsapo populations subjected to severe drought

Summary

Introduction

Changes in the environment occur so fast that species’ adaptive capacities may be overcome [1,2,3]. The pace of observed climate warming, in relict tree species, implies that environmental conditions are changing faster than plant populations can adapt, acclimate or migrate [3]. Conifers have shown a slower evolutionary rate compared to angiosperms [6,7] They maintain high levels of genetic diversity and may display fast local adaptation [5]. The examination of the selection of the adaptive genetic variations will help understand the adaptive potential and the fates of endangered tree species [8] These insights might guide the design of suitable conservation and management policies, for instance, via assisted genetic migration or genotype selection [8]. Landscape genomics and genome-wide association studies are attempting to identify genetic variants that correlate with environmental factors [9,10,11] and/or sound phenotypic traits [12]

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