A 350‐million‐year legacy of fire adaptation among conifers

Abstract

Summary Current phylogenetic evidence shows that fire began shaping the evolution of land plants 125 Ma, although the fossil charcoal record indicates that fire has a much longer history (>350 Ma). Serotiny (on‐plant seed storage) is generally accepted as an adaptation to fire among woody plants. We developed a conceptual model of the requirements for the evolution of serotiny, and propose that serotiny is only expressed in the presence of a woody rachis as supporting structure, compact scales covering seeds as protective structure, seed wing as dispersal structure, and crown fire as the agent of selection and mechanism for seed release. This model is strongly supported by empirical data for modern ecosystems. We reconstructed the evolutionary history of intrinsic structural states required for the expression of serotiny in conifers, and show that these were diagnostic for early (‘transitional’) conifers from 332 Ma (late‐Carboniferous). We assessed the likely flammable characteristics of early conifers and found that scale‐leaved conifers burn rapidly and with high intensity, supporting the idea that crown fire regimes may have dominated early conifer ecosystems. Synthesis. Coupled with strong evidence for frequent fire throughout the Permian‐Carboniferous and fossil evidence for other fire‐related traits, we conclude that many early conifers were serotinous in response to intense crown fires, indicating that fire may have had a major impact on the evolution of plant traits as far back as 350 Ma.

Global trends in wildfire and its impacts: perceptions versus realities in a changing world

“…When considering some of the extreme landscape fires as a form of natural disaster, the number of deaths is actually relatively low compared with other natural disaster types. For example, data by the Emergency Events Database (EM-DAT) 2 Fire has long been a natural factor in many ecosystems around the world, from boreal forests to tropical savannas [76,77]. In these systems, fire is a necessary perturbation to preserve ecosystem health and stimulate rejuvenation [78,79].…”

“…These estimates of losses, however, only include damage to property, crops and livestock and do not reflect losses from fire events not classified as disasters. 2 Other important economic parameters not included here are the costs arising from human losses, injuries and longer-term health implications [95]. Furthermore, fire suppression costs are not considered in these figures.…”

“…Fire has been an important factor in the dynamics of the Earth's climate and in the development of biomes since its widespread occurrence began 400-350 million years ago (Ma) [1,2]. In fire-prone ecosystems, humans have always coexisted with fire in the landscape, and its use can be seen as the first anthropogenic tool that has affected ecosystem dynamics beyond the very local scale [3].…”

“…While the vast majority of 30-46 million km 2 of the global land surface burned per year (approx. 4% the global land surface) [22] has little direct impact on individuals and therefore does not attract wider attention, the media tend to report on the costly and sometimes tragic impacts of some wildfires, with a focus on the fate of individuals [21,23].…”

Shoot flammability is decoupled from leaf flammability, but controlled by leaf functional traits

“…An understanding of plant flammability can also inform fundamental research. For instance, flammability is recognized as a core plant functional trait (Cornelissen et al, ; Perez‐Harguindeguy et al, ) and is a key factor in understanding the evolution of land plants (Pausas & Moreira, ; Schwilk & Ackerly, ), particularly given the 420 million‐year shared history of plants and fire (Glasspool, Edwards, & Axe, ; He, Belcher, Lamont, & Lim, ; Scott, ). Flammability can influence the fitness, survival, reproduction and distribution of plants, as seen by the evolution of flammability strategies in fire‐prone environments (Bond & Midgley, ; Mutch, ; Pausas et al, ).…”