Historical links between climate and fire on species dispersion and trait evolution

Abstract

The interaction effects between climate and fire regime in controlling the type of vegetation and species composition is well established among the Earth’s biomes. Climate and the associated fire regime are never stable for long, and annual temperatures, atmospheric carbon dioxide and oxygen levels, and burn probability have varied radically over the last 350 million years. At the scale of thousands of years, floras have oscillated between spreading and retracting as climate and the dependent fire regime have fluctuated. At the scale of millions of years, distinct traits have evolved along three lines: fire resistance, fire-stimulated dormancy release, and rapid postfire growth, all limited by the type of fire (as controlled by climate) and postfire weather. Eight pairings of fire- and postfire-related traits resulting from the interplay between fire and climate are noted here. Smoke-released seed dormancy is beneficial on two counts: it increases the chance of recruitment under the present fireprone climate and increases the chances of survival should the wet season shift to another time of year where temperatures are higher or lower. Four pathways can be recognized with respect to the fire regimes induced by climate changes: (1) from non-fireprone to fireprone habitats (gains fire-adapted trait, 13 studies covering the last 115 million years (My) described here); (2) from a surface fire to a crown fire-type habitat (gains a different fire-adapted trait, 13 studies); (3) from a crown fire-type to surface fire-type habitat (loss of fire-adapted trait, 12 studies); and (4) from moderately burnt (crown fire) to non-fireprone habitat, such as desert, rainforest, or alpine habitats (loss of fire-adapted trait, 6 studies). Four case studies, at decreasing taxonomic rank, are used to illustrate the intimate relationship between climate change with its associated vegetation and fire regime change as they promote adaptive trait evolution: gain then loss of heat-released seed dormancy in Dipterocarpaceae–Cistaceae–Bixaceae over 90 My, gain then loss of serotiny in Callitroid Cupressaceae over the last 65 My, gain then loss of smoke-released seed dormancy in Proteoid Proteaceae over the last 120 My, and gain then loss of resprouting and serotiny among Hakea species (Grevilleoid Proteaceae) over the last 20 My. Examples of within-species rates of migration and trait change, including a model describing increasing degree of serotiny with intensifying drought, are given. The relevance of this historical approach to current (anthropogenic) climate change and associated fire regime alteration is discussed. Despite major threats expected to species conservation status at both the macro-(biome) and micro-(population) scales, I conclude that insufficient time or opportunities remain for effective migration to less-stressed areas or suitable adaptive responses to climate/fire regime change to evolve.

Ancient Rhamnaceae flowers impute an origin for flowering plants exceeding 250-million-years ago

“…The fire-prone environment but rarity of seed dormancy in this latter clade implies a monsoon-dominated past ( Pausas and Lamont 2022 ) consistent with the savanna setting of many extant species assessed here ( Figure S1 ). These results now add an important fire-related trait to the growing list of ancient adaptations to fire ( He et al., 2016 ; Lamont 2022 ).…”

Climate change and altered fire regimes: impacts on plant populations, species, and ecosystems in both hemispheres

“…Some changes will arise from climate-driven alterations to different dimensions of fire regimes, such as increases in severity that are governed by the combination of fire behavior and fire-adaptive (or sensitive) plant traits (Franco et al 2022). Other changes will emerge when shifting fire regimes interact with key demographic and community dynamics pre-fire (Agne et al 2022;Gosper et al 2022;Souto-Veiga et al 2022) and post-fire (Arroyo-Vargas et al 2022;Dawe et al 2022;Brehaut and Brown 2022); some occurring over evolutionary time scales (Lamont 2022;Ladd et al 2022). Finally, some changes will emerge as surprising outcomes from disturbances interacting in a linked (Lindenmayer et al 2022) or compound (Bendall et al 2022) manner.…”

“…Similar gradients of moisture across coastal and inland areas have been related to variation in serotiny in pines on the west coast of North America (Millar 1986a(Millar , 1986b) and demonstrate critical spatial dimensions to fire adaptations within a species. Lamont (2022; this issue) explores pathways of how three classes of fire-adapted traits-fire resistance, fire-stimulated dormancy release, and rapid post-fire growth-are guided by different combinations of climate, associated fire regimes, and post-fire growing conditions. Using this historical lens through evolutionary time scales is especially relevant when considering the pace of climate and fire regime change in the twenty-first century (Pausas and Keeley 2021).…”

“…Using this historical lens through evolutionary time scales is especially relevant when considering the pace of climate and fire regime change in the twenty-first century (Pausas and Keeley 2021). The conclusions by Lamont (2022) about the mismatch between the times required for adaptation or mitigation vs the accelerating rate of global change have important implications for biodiversity conservation worldwide.…”

Gondwanan origin of the Dipterocarpaceae-Cistaceae-Bixaceae is supported by fossils, areocladograms, ecomorphological traits and tectonic-plate dynamics

“…That is certainly possible. Related work has shown how this superclade has passed through various climates and vegetation types, including fire-prone savannas that promoted evolution of various fire-related traits (Lamont 2022, Pausas andLamont 2022). Even so, there is no evidence that clades currently in rainforests had a substantially different biogeographic history.…”