The genetic basis of cone serotiny inPinus contortaas a function of mixed-severity and stand-replacement fire regimes

Abstract

!Wildfires and mountain pine beetle (MPB) attacks are important contributors to the development of stand structure in lodgepole pine, and major drivers of its evolution. The historical pattern of these events have been correlated with variation in cone serotiny (possessing cones that remain closed and retain seeds until opened by fire) across the Rocky Mountain region of Western North America. As climate change brings about a marked increase in the size, intensity, and severity of our wildfires, it is becoming increasingly important to study the genetic basis of serotiny as an adaptation to wildfire. Knowledge gleaned from these studies would have direct implications for forest management in the future, and for the future. In this study, we collected physical data and DNA samples from 122 trees of two different areas in the IDF-dk of British Columbia; multi-cohort stands (Cariboo-Chilcotin) with a history of mixed-severity fire and frequent MPB disturbances, and single-cohort stands (Logan Lake) with a history of stand replacing (crown) fire and infrequent MPB disturbances. We used QuantiNemo to construct simulated populations of lodgepole pine at five different growth rates, and compared the statistical outputs to physical data, then ran a random forest analysis to shed light on sources of variation in serotiny. We also sequenced 39 SNPs, of which 23 failed or were monomorphic. The 16 informative SNPs were used to calculate HO and HE, which were included alongside genotypes for a second random forest analysis. Our best random forest model explained 33% of variation in serotiny, using simulation and physical variables. Our results highlight the need for more investigation into this matter, using more extensive approaches, and also consideration of alternative methods of heredity such as epigenetics.

Uncovering the contribution of epigenetics to plant phenotypic variation in Mediterranean ecosystems

“…; Feduck et al . ). Congruently, with the scarcity of knowledge about the genetics of serotiny, no epigenetic mechanism for serotiny has yet been established.…”

Fire as a Selective Agent for both Serotiny and Nonserotiny Over Space and Time

“…There is much interest in the genetic versus environmental control of serotiny with the evidence so far varying from strongly to negligibly heritable (Parchman et al, 2012;Budde et al, 2014;Vincenzi and Piotti, 2014;Castellanos et al, 2015;Feduck et al, 2015). Part of the explanation for such variable results is that in most of these studies serotiny is gauged as the fraction of cones that is closed, which clearly has an age/size/growing-condition component.…”

“…Having identified what traits are involved in the serotiny/nonserotiny syndromes this opens the way for intensive study of their genetic basis and what genes control their expression. With increasing interest in the heritability of serotiny (Parchman et al, 2012, Budde et al, 2014, Vincenzi and Piotti, 2014Castellanos et al, 2015;Feduck et al, 2015), it is essential that the index reflects the extent to which viable seeds remain stored on the plant over time and is not confounded by plant age, fecundity or growing conditions. The most stable index in this regard is the slope measure of serotiny but our literature survey shows that it has only been adopted as the standard measure in Australia.…”

Evaluation of seven indices of on‐plant seed storage (serotiny) shows that the linear slope is best

“…Thus, Table 5 shows how, despite a four times greater total seed store among Banksia menziesii shrubs due to recently improved growing conditions, the slope index remains stable and also gives a robust estimate of the age of the oldest cone to open. It is likely that the very low to moderate levels so far obtained for standard indices of heritability are due to the inappropriate choice of serotiny index (% total cones serotinous) rather than this trait having a large environmental component as concluded (Feduck et al., 2015; Hernández‐Serrano et al., 2014).…”

“…There is an increasing interest in the role of serotiny in enabling exotic species to invade new habitats (Franzese & Raffaele, 2017; Ripa, Franzese, Premoli, & Raffaele, 2020), how it is affected by climate change (Vincenzi & Piotti, 2014) and its heritability, that is, the extent to which serotiny is genetically or environmentally controlled (Castellanos, González‐Martínez, & Pausas, 2015; Feduck et al., 2015). It is therefore essential that the index of serotiny chosen reflects the extent to which viable seeds remain stored on the plant over time and is not confounded by plant age or recently imposed growing conditions that do not have a genetic basis.…”