Search

Fire has long been recognized as a significant evolutionary factor for the genus Pinus (family Pinaceae). Many pine species have developed specific fire-adaptations, such as self-pruning, resprouting, and serotiny, to persist under various fire regimes. Fire-related traits, such as needle length, bark thickness, and plant height, also can affect the survival of pines in fire-prone environments. Investigating the climate conditions of pines and analyzing the variation in fire-adaptations and fire-related traits across pines can provide insights into the evolutionary process of the genus Pinus affected by fire. However, such studies are rare, particularly those focusing on the relationship among environmental conditions, fire-adaptations, and fire-related traits with a large number of pine species. In this study, we explored the variation in climate conditions and fire-related traits (including tree height, bark thickness, and leaf length) between fire-adapted and non-fire-adapted pines, as well as among three fire survival strategies (fire-tolerators, fire-embracers, fire avoiders). We also investigated the relationships between climatic conditions and fire-related traits/fire-adaptations (including resprouting, self-pruning, the grass stage, and serotiny) across the genus Pinus. Sixty-one out of 101 pine species were found to possess one or more fire adaptations and were classified as fire-adapted pines. We found that fire-adapted pines occupy warmer and more fire-prone habitats, and exhibit longer leaves, thicker bark, and taller habits than non-fire-adapted species. Our analysis did not indicate a significant difference between fire tolerators and embracers regarding traits and climate conditions, except that fire-tolerators have thicker bark and are more associated with wildfire-prone areas. Climate conditions appeared to significantly affect fire-related traits/fire-adaptations across the genus Pinus. These findings will facilitate our understanding the evolutionary process of fire adaptations/fire-related traits in the genus Pinus and will guide sustainable fire management in different pine forests.

Information about smoke cues for seed germination is fundamental to understanding fire adaptation. Recently, lignin-derived syringaldehyde (SAL) was identified as a new smoke cue for seed germination, which challenges the assumption that cellulose-derived karrikins are the primary smoke cues. We highlight the overlooked association between lignin and the fire adaptation of plants. [ABSTRACT FROM AUTHOR]

Many animals survive wildfires; however, the mechanisms used to detect and respond to fire have been poorly studied. Sensory cues like sight and sound are used to recognize threats (e.g. predators) and elicit escape responses in prey. Similarly, these cues might be used to detect an approaching wildfire. We tested whether the western fence lizard, Sceloporus occidentalis , responds to the sound of fire as a threat. We predicted that lizards living in burned areas would be more sensitive to the sound of fire than lizards in adjacent and urban areas, where fire suppression could have induced relaxed selection on fire responsiveness. We compared the behaviours of lizards following an experimental playback where we broadcast the sound of fire along with other control sounds (a predator, a common nonpredatory bird and a novel nonpredatory bird). We conducted our playbacks in 2019 in recently burned areas (using the survivors from the 2018 Woolsey Fire, southern California, U.S.A.), unburned adjacent areas and urban areas. We found that in burned areas, lizards responded more to the sound of fire than all three controls, but in urban areas, they responded more to both the sound of a predator and the sound of fire. Our results suggest that lizard responses to fire sounds are greater in an area that has recently experienced a wildfire than in an unburned area, and that urban areas create a complex evolutionary landscape that also increased antipredator behaviour for other biologically relevant stimuli. • Lizards surviving wildfires are more alert to fire sound than those in unburned areas. • Lizards living in urban areas reacted to fire sound similarly to wildfire survivors. • Both natural and human-driven disturbances can shape the behaviour of animals. • Fires are likely to be an important selective pressure on animal behaviour. [ABSTRACT FROM AUTHOR]

Abstract Fire and frost represent two major hurdles for the persistence of trees in open grassy biomes and have both been proposed as drivers of grassland‐forest boundaries in Africa. We assess the response of young tree seedlings, which represent a vulnerable stage in tree recruitment, to traumatic fire and frost disturbances. In a greenhouse experiment, we investigated how seedling traits predicted survival and resprouting ability in response to fire versus frost; we characterized survival strategies of seedlings in response to the two disturbances, and we documented how the architecture of surviving seedlings is affected by fire versus frost injury. Survival rates were similar under both treatments. However, different species displayed different levels of sensitivity to fire and frost. Seedling survival was higher for older seedlings and seedlings with more basal leaves. Survivors of a fire event lost more biomass than the survivors of a frost event. However, the architecture of recovered fire‐ and frost‐treated seedlings was mostly similar. Seedlings that recovered from fire and frost treatments were often shorter than those that had not been exposed to any disturbance, with multiple thin branches, which may increase vulnerability to the next frost or fire event. Synthesis. Fire caused more severe aboveground damage compared with a single frost event, suggesting that fire is an important driver of tree distribution in these open grassland systems. However, the impact of repeated frost events may be equally severe and needs to be investigated. Also, woody species composition may be influenced by phenomena that affect the timing and frequency of seedling exposure to damage, as mortality was found to be dependent on seedling age. Therefore, changes in fire regime and climate are likely to result in changes in the composition and the structure of the woody components of these systems.

How coniferous forests evolved in the Northern Hemisphere remains largely unknown. Unlike most groups of organisms that generally followa latitudinal diversity gradient, most conifer species in the Northern Hemisphere are distributed in mountainous areas at middle latitudes. It is of great interest to know whether the midlatitude region has been an evolutionary cradle or museum for conifers and how evolutionary and ecological factors have driven their spatiotemporal evolution. Here, we investigated the macroevolution of Pinus, the largest conifer genus and characteristic of northern temperate coniferous forests, based on nearly complete species sampling. Using 1,662 genes from transcriptome sequences, we reconstructed a robust species phylogeny and reestimated divergence times of global pines. We found that ~90% of extant pine species originated in the Miocene in sharp contrast to the ancient origin of Pinus, indicating a Neogene rediversification. Surprisingly, species at middle latitudes are much older than those at other latitudes. This finding, coupled with net diversification rate analysis, indicates that the midlatitude region has provided an evolutionary museum for global pines. Analyses of 31 environmental variables, together with a comparison of evolutionary rates of niche and phenotypic traits with a net diversification rate, found that topography played a primary role in pine diversification, and the aridity index was decisive for the niche rate shift. Moreover, fire has forced diversification and adaptive evolution of Pinus. Our study highlights the importance of integrating phylogenomic and ecological approaches to address evolution of biological groups at the global scale. [ABSTRACT FROM AUTHOR]

Fire and frost represent two major hurdles for the persistence of trees in open grassy biomes and have both been proposed as drivers of grassland‐forest boundaries in Africa.We assess the response of young tree seedlings, which represent a vulnerable stage in tree recruitment, to traumatic fire and frost disturbances.In a greenhouse experiment, we investigated how seedling traits predicted survival and resprouting ability in response to fire versus frost; we characterized survival strategies of seedlings in response to the two disturbances, and we documented how the architecture of surviving seedlings is affected by fire versus frost injury.Survival rates were similar under both treatments. However, different species displayed different levels of sensitivity to fire and frost. Seedling survival was higher for older seedlings and seedlings with more basal leaves. Survivors of a fire event lost more biomass than the survivors of a frost event. However, the architecture of recovered fire‐ and frost‐treated seedlings was mostly similar. Seedlings that recovered from fire and frost treatments were often shorter than those that had not been exposed to any disturbance, with multiple thin branches, which may increase vulnerability to the next frost or fire event.Synthesis. Fire caused more severe aboveground damage compared with a single frost event, suggesting that fire is an important driver of tree distribution in these open grassland systems. However, the impact of repeated frost events may be equally severe and needs to be investigated. Also, woody species composition may be influenced by phenomena that affect the timing and frequency of seedling exposure to damage, as mortality was found to be dependent on seedling age. Therefore, changes in fire regime and climate are likely to result in changes in the composition and the structure of the woody components of these systems. [ABSTRACT FROM AUTHOR]

Bark thickness is a key structural feature in woody plants in the protection against fire. We used 19 provenances of Pinus halepensis, an obligate-seeder species, in a replicated common garden at two environments contrasting in water availability to assess the interacting effects of site environment and population in the relative allocation to bark, expecting lower allocation at the drier site. Secondly, given the average fire frequency, we analyzed whether trees reached the critical absolute thickness soon enough for population persistence via aerial seed bank. Our analyses indicated that trees at the moister site allocated a rather fixed quantity of resources independent of tree size, and almost all populations reached critical absolute bark thickness to eventually survive fire. In contrast, at the drier site allocation to bark reduced with tree size, and most populations did not reach the critical bark thickness. Populations from areas with higher fire frequency had thicker basal bark, while those from areas with severe droughts and short vegetative periods, had thinner bark. In conclusion, drought-stressed trees have a higher risk to die from fires before achieving reproduction and building a sufficient aerial seed bank.

Bark thickness is a key structural feature in woody plants in the protection against fire. We used 19 provenances of Pinus halepensis , an obligate-seeder species, in a replicated common garden at two environments contrasting in water availability to assess the interacting effects of site environment and population in the relative allocation to bark, expecting lower allocation at the drier site. Secondly, given the average fire frequency, we analyzed whether trees reached the critical absolute thickness soon enough for population persistence via aerial seed bank. Our analyses indicated that trees at the moister site allocated a rather fixed quantity of resources independent of tree size, and almost all populations reached critical absolute bark thickness to eventually survive fire. In contrast, at the drier site allocation to bark reduced with tree size, and most populations did not reach the critical bark thickness. Populations from areas with higher fire frequency had thicker basal bark, while those from areas with severe droughts and short vegetative periods, had thinner bark. In conclusion, drought-stressed trees have a higher risk to die from fires before achieving reproduction and building a sufficient aerial seed bank. [ABSTRACT FROM AUTHOR]

Globally, variability in canopy seed retention within closed cones (serotiny) among fire-adapted plant species is often associated with gradients in fire regime. Few studies have investigated the association of intraspecific variation in serotiny with geographical variation in fire and other environmental factors, especially climatic ones, and none has done so in the Cape Floristic Region (CFR) of South Africa. Yet the relationship between environmental gradients and intraspecific variation in reproductive traits may help us understand if those gradients partly shaped the evolution of the rich diversity or proteas in the CFR, and predict the resilience of fire-adapted Protea species to climate and fire regime changes in the CFR. We examined the association of the variability in serotiny in Protea repens (L.) L, the Common Sugarbush, with gradients in fire regime and climatic factors, and with plant age, cone age, and age of oldest closed cone across its 700 km-long longitudinal range in the CFR. Cone age was a significant covariate of the probability that a given cone was closed (our measure of serotiny), but plant age and age of oldest closed cone were not. Variability in the degree of serotiny was significant among populations. Serotiny was highest where fire intensity was historically high, where both mean annual precipitation and mean annual temperature were low, and where rainfall was least seasonal, but fire frequency was not a predictor of serotiny. [ABSTRACT FROM AUTHOR]

Abstract: Questions: Functional interactions between fire and fire‐dependent plant communities have been considered to select for increased community flammability. We address this concept by resolving: (a) can fossil pollen records be used to examine past variations in functional attributes; (b) can community‐level, functional responses to fire be obtained by coupling fire history with pollen derived plant traits; and (c) has directional selection promoted attributes that increase community flammability? Location: Breitenbush Lake, Oregon, USA. Methods: We developed a framework based on ecological understanding of functional traits and pollen records to analyse variations in functional attribute expressions through time. Fire‐related functional attributes that indicate sensitivity to changes in fire activity were identified and associated with taxa from a pollen record. Results: Nine of the 14 functional attributes were significantly related to fire frequency (number of fires 1,000 per year). When combined with fire history data, variation in the abundances of functional attributes suggest selection of plant community expressions that indicate community‐level responses to fire related to changes in structural development and changes in fire adaptation. Fire frequency variations may drive directional selection for fire‐adapted attributes, and against fire‐sensitive attributes. Our results indicate increased Holocene fire activity may have been linked to vegetation functional interactions with fire. Conclusions: Our method of combining paleoecological data with functional traits allowed reconstruction of community‐level changes in the expression of functional characteristics, providing evidence on structural development and changes in fire adaptation. Our results (a) highlight the capacity of paleoecological records to track plant community trait composition; (b) provide novel information on fire–vegetation relationships, independent of and complementary to conventional methods of disturbance‐based paleoecological interpretations; (c) suggest the Holocene fire trend may be linked to the type of biomass being burned through directional selection; and (d) suggest an application that may be applied to quantify community responses to various disturbances across broad temporal and spatial scales. [ABSTRACT FROM AUTHOR]

Wildfire and the threat it poses to society represents an example of the complex, dynamic relationship between social and ecological systems. Increasingly, wildfire adaptation is posited as a pathway to shift the approach to fire from a suppression paradigm that seeks to control fire to a paradigm that focuses on "living with" and "adapting to" wildfire. In this study, we seek insights into what it means to adapt to wildfire from a range of stakeholders whose efforts contribute to the management of wildfire. Study participants provided insights into the meaning, relevance, and use of the concept of fire adaptation as it relates to their wildfire-related activities. A key finding of this investigation suggests that social scale is of key importance in the conceptualization and understanding of adaptation for participating stakeholders. Indeed, where you stand in terms of understandings of fire adaptation depends in large part on where you sit. [ABSTRACT FROM AUTHOR]

Fire as a major evolutionary force has been disputed because it is considered to lack supporting evidence. If a trait has evolved in response to selection by fire then the environment of the plant must have been fire-prone before the appearance of that trait. Using outcomes of trait assignments applied to molecular phylogenies for fire-stimulated flowering, seed-release, and germination, in this Opinion article we show that fire-proneness precedes, or rarely coincides with, the evolution of these fire-adapted traits. In addition, fire remains central to understanding germination promoted by smoke among species occurring in non-fire-prone environments because of the historical association of their clade with fire. Fire-mimicking selection and associated exaptations have no place in understanding the evolution of fire-adapted traits because we find no support for any reversal in the fire–trait sequence through time. [ABSTRACT FROM AUTHOR]

Background: Dioscorea is a widely distributed and highly diversified genus in tropical regions where it is represented by ten main clades, one of which diversified exclusively in Africa. In southern Africa it is characterised by a distinct group of species with a pachycaul or "elephant's foot" structure that is partially to fully exposed above the substrate. In contrast to African representatives of the genus from other clades, occurring mainly in forest or woodland, the pachycaul taxa and their southern African relatives occur in diverse habitats ranging from woodland to open vegetation. Here we investigate patterns of diversification in the African clade, time of transition from forest to more open habitat, and morphological traits associated with each habitat and evaluate if such transitions have led to modification of reproductive organs and mode of dispersal. Results: The Africa clade originated in the Oligocene and comprises four subclades. The Dioscorea buchananii subclade (southeastern tropical Africa and South Africa) is sister to the East African subclade, which is respectively sister to the recently evolved sister South African (e. g., Cape and Pachycaul) subclades. The Cape and Pachycaul subclades diversified in the east of the Cape Peninsula in the mid Miocene, in an area with complex geomorphology and climate, where the fynbos, thicket, succulent karoo and forest biomes meet. Conclusions: Diversification out of forest is associated with major shifts in morphology of the perennial tuber (specifically an increase in size and orientation which presumably led them to become pachycaul) and rotation of stem (from twining to non-twining). The iconic elephant's foot morphology, observed in grasslands and thicket biomes, where its corky bark may offer protection against fire and herbivory, evolved since mid Miocene. A shift in pollination trait is observed within the forest, but entry into open habitat does not show association with reproductive morphology, except in the seed wing, which has switched from winged all round the seed margin to just at the base or at the apex of it, or has been even replaced by an elaiosome. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Aim Palaeoendemics are clades that are ancient but geographically restricted, often because they have been selected against in other areas. Ecological similarities among palaeoendemics may be indicators of ancient environments. We determine the environmental ranges of the remarkable palaeoendemic plants of Tasmania to deduce whether they indicate the long-term persistence of particular environmental conditions. Location Tasmania, Australia, a global centre of plant palaeoendemism, containing some of the world's most relictual plant lineages. Methods Palaeoendemic clades in Tasmania were identified using a scoring system of clade age divided by the square root of the number of 10 km × 10 km grid cells occupied globally. Total palaeoendemism scores for 1199 30″ grid cells were calculated by summing scores for individual clades, and modelled against climate, topography, geology and vegetation type using Random Forest models. Palaeoendemic and non-palaeoendemic species richness in climate space was measured. The global distribution of climates favoured by palaeoendemics was assessed. Results Twenty-nine phylogenetically and ecologically diverse palaeoendemic clades (51 species) were identified. High levels of palaeoendemism occurred widely in western Tasmania, but the highest scoring areas were at or slightly above the tree line in relatively undisturbed vegetation. Palaeoendemism scores were strongly predicted by constantly moist climates lacking extreme temperatures, and by open vegetation types with rare or no fire. The palaeoendemics occupied a climate space that is globally rare and very different from that of non-palaeoendemics. Main conclusions These patterns suggest the persistence since the Cretaceous of open vegetation in constantly moist areas with equable temperatures and few or no fires. This conclusion is consistent with an increasing body of fossil and phylogenetic evidence for the antiquity of open vegetation. The methods here produce quantitative values of palaeoendemism that can be compared among regions. [ABSTRACT FROM AUTHOR]

Understanding how biotic communities respond to landscape spatial structure is critically important for conservation management as natural habitats become increasingly fragmented. However, empirical studies of the effects of spatial structure on plant species richness have found inconsistent results, suggesting that more comprehensive approaches are needed. We asked how landscape structure affects total plant species richness and the richness of a guild of specialized plants in a multivariate context. We sampled herbaceous plant communities at 56 dolomite glades (insular, fire-adapted grasslands) across the Missouri Ozarks, USA, and used structural equation modeling (SEM) to analyze the relative importance of landscape structure, soil resource availability, and fire history for plant communities. We found that landscape spatial structure, defined as the area-weighted proximity of glade habitat surrounding study sites (proximity index), had a significant effect on total plant species richness, but only after we controlled for environmental covariates. Richness of specialist species, but not generalists, was positively related to landscape spatial structure. Our results highlight that local environmental filters must be considered to understand the influence of landscape structure on communities and that unique species guilds may respond differently to landscape structure than the community as a whole. These findings suggest that both local environment and landscape context should be considered when developing management strategies for species of conservation concern in fragmented habitats. [ABSTRACT FROM AUTHOR]

Wildfire and the threat it poses to society represents an example of the complex, dynamic relationship between social and ecological systems. Increasingly, wildfire adaptation is posited as a pathway to shift the approach to fire from a suppression paradigm that seeks to control fire to a paradigm that focuses on "living with" and "adapting to" wildfire. In this study, we seek insights into what it means to adapt to wildfire from a range of stakeholders whose efforts contribute to the management of wildfire. Study participants provided insights into the meaning, relevance, and use of the concept of fire adaptation as it relates to their wildfire-related activities. A key finding of this investigation suggests that social scale is of key importance in the conceptualization and understanding of adaptation for participating stakeholders. Indeed, where you stand in terms of understandings of fire adaptation depends in large part on where you sit.

Soil seed banks play a major role in the post-fire regeneration of semi-arid mountain grasslands. Plant species present before fire can determine the soil seed bank (SSB) characteristics in fire-prone ecosystems. However, it remains unclear how the density and species composition of the SSB under the canopy cover of specific shrub species may be affected by fire. Therefore, we designed a study to test the effects of prescribed burning on the viable SSBs under the canopies of two shrub species: Berberis integerrima (with open canopies) and Onobrychis cornuta (with dense canopies). We selected 20 study sites that included separate patches of the two shrub species and nearby herbaceous patches as control. Soil sampling was carried out pre- and post-burning of shrub canopies and the control patch. Soil samples were collected at two depths: 0–5 cm and 5–10 cm, and transported to the greenhouse for germination experiments. The results showed that canopy fire of shrubs decreased SSB density and species richness. However, the effects of shrub burning on SSB were species-specific and these reductions were more pronounced for canopy burning of O. cornuta than for B. integerrima. Total SSB densities decreased by 61% for B. integerrima and 71% for O. cornuta after canopy fire at soil depth of 0–5 cm. At soil depth of 5–10 cm, total SSB density decreased by 45% under O. cornuta after canopy fire, while canopy fire of B. integerrima did not affect SSB density. Herbaceous patch burning had no statistically significant effects on SSB density at soil depths of 0–5 cm and 5–10 cm. The comparison of quantitative and qualitative similarity indices between pre- and post-fire species composition of shrub canopy showed that the statistically significant effect of B. integerrima burning on SSB composition was less pronounced compared with O. cornuta. This study indicated that seeds stored within the soil under certain shrub species are at a high risk of mortality during fire. Thus, successful post-fire recovery does not rely on the seed bank reservoir under these shrubs. [Display omitted] [ABSTRACT FROM AUTHOR]

Ant seed dispersal is a globally important mutualism that occurs in over 10,000 plant species. Relatively little research has been conducted on ant seed dispersal of Corema conradii (broom crowberry), a key constituent of globally threatened coastal heathland ecosystems where fire is part of the disturbance regime. We conducted field studies at Cape Cod National Seashore, MA, USA to better understand the fruiting biology of C. conradii and to explore the benefits of ant seed dispersal. We identified how C. conradii fruit is displayed to foraging ants, determined the ant species that disperse C. conradii fruit, and quantified the distance that ants disperse fruit. We hypothesized that ants would disperse fruit away from C. conradii parent plants that become burn footprints following fire, to ensure seed dispersal to suitable germination sites, where we expected to find higher seedling establishment. We recorded eight ant species dispersing the fruit of C. conradii an average distance of 136 cm (±10.45) (range: 7-641 cm). Two ant species, Aphaenogaster treatae and Formica dolosa, dispersed 60 % of fruit in fruit-baiting experiments, suggesting they may function as primary dispersers in this system. Ants dispersed fruit outside the burn footprints 82 % of the time, and seedlings occurred outside the burn footprints 90 % of the time. Our results suggest that ant seed dispersal confers important reproductive benefits to C. conradii by directing seed dispersal sufficient distances away from parent plants onto suitable substrates for germination after intense, episodic fires. [ABSTRACT FROM AUTHOR]

We examined the effects of fire and canopy disturbance on turkeybeard (Xerophyllum asphodeloides[L.] Nutt.), a rare temperate forest herb. We used long-term data and a fire and canopy alteration experiment with controls to address our hypothesis that turkeybeard is fire-adapted. Analyses of a primary study population demonstrated that turkeybeard is a long-lived, infrequently flowering perennial with high survival and rapid postfire resprouting ability. Experimental responses showed that population-level flowering and inflorescence production increased 60–280% across treatments compared to controls in two posttreatment seasons. Seed production/inflorescence was significantly higher in treated plants. Fire and canopy removal treatments had a positive and additive effect on seed set compared to controls. Additional population surveys and pollination experiments showed that turkeybeard exhibited low flowering levels in undisturbed forest and required outcrossing for good seed set. Burning released plants from these limiting factors by inducing mass-flowering and altering the forest habitat to attract insect pollinators. Our research demonstrates that turkeybeard is one of the few known definitively fire-adapted montane forest understory herbs in the eastern United States, such that fire management including prescribed burning is recommended for its conservation and management. It also adds new impetus for studying fire’s ecological role in these lands. [ABSTRACT FROM PUBLISHER]

The origin of fire-adapted lineages is a long-standing question in ecology. Although phylogeny can provide a significant contribution to the ongoing debate, its use has been precluded by the lack of comprehensive DNA data. Here, we focus on the 'underground trees' (=geoxyles) of southern Africa, one of the most distinctive growth forms characteristic of fire-prone savannas., We placed geoxyles within the most comprehensive dated phylogeny for the regional flora comprising over 1400 woody species. Using this phylogeny, we tested whether African geoxyles evolved concomitantly with those of the South American cerrado and used their phylogenetic position to date the appearance of humid savannas., We found multiple independent origins of the geoxyle life-form mostly from the Pliocene, a period consistent with the origin of cerrado, with the majority of divergences occurring within the last 2 million yr. When contrasted with their tree relatives, geoxyles occur in regions characterized by higher rainfall and greater fire frequency., Our results indicate that the geoxylic growth form may have evolved in response to the interactive effects of frequent fires and high precipitation. As such, geoxyles may be regarded as markers of fire-maintained savannas occurring in climates suitable for forests. [ABSTRACT FROM AUTHOR]

Byrsonima crassifolia (L.) Kunth, B. coccolobifolia Kunth and B. verbascifolia (L.) DC. (Malpighicaceae) are sympatric species with high ecological importance in the Roraima savannas of northern Brazil. The three species can be distinguished by seedling characters. The phanerocotylar, epigeal, foliaceous seedling of B. crassifolia is similar to other forest species in the genus. On the other hand, both B. coccolobifolia and B. verbascifolia have phanerocotylar, hypogeal, foliaceous seedlings, representing a newly defined seedling group among eudicot seedling types. Byrsonima verbascifolia has a reduced epicotyl and short subsequent internodes, whereas the long cotyledonary petioles are diagnostic for B. coccolobifolia. Both B. coccolobifolia and B. verbascifolia have cryptogeal germination, which involves characters that presumably protect the plumule from the recurrent fires they are subjected in savannas (e.g., plumule burying, cotyledonary node below the soil surface, and fusion of cotyledonary petioles). This is the first report of cryptogeal germination in the Malpighiaceae as well as in Neotropical eudicots. [ABSTRACT FROM AUTHOR]

The new species, Rhynchospora marliniana Naczi, W. M. Knapp & W. W. Thomas, is described, illustrated, and compared with morphologically similar species. Images are provided of its habitats, which are sunny, wet, and nutrient-poor savannas, pinelands, and streamsides in Belize, Honduras, Mexico, Nicaragua, and the southeastern USA. It is unique in Rhynchospora sect. Plumosae by having perianth bristles that are plumose only at their bases and have a smooth zone between the plumose and minutely denticulate zones. Additional diagnostic characters are dark brown proximal leaf sheaths and perianth bristles that exceed the tubercle. Rhynchospora marliniana survives burning, and quickly initiates both vegetative and reproductive growth after fire. [ABSTRACT FROM AUTHOR]

Large proportions of the Earth's land surface are covered by biomes dominated by C4 grasses. These C4-dominated biomes originated during the late Miocene, 3-8 million years ago (Ma), but there is evidence that C4 grasses evolved some 20 Ma earlier during the early Miocene/Oligocene. Explanations for this lag between evolution and expansion invoke changes in atmospheric CO2, seasonality of climate and fire. However, there is still no consensus about which of these factors triggered C4 grassland expansion., We use a vegetation model, the adaptive dynamic global vegetation model (aDGVM), to test how CO2, temperature, precipitation, fire and the tolerance of vegetation to fire influence C4 grassland expansion. Simulations are forced with late Miocene climates generated with the Hadley Centre coupled ocean-atmosphere-vegetation general circulation model., We show that physiological differences between the C3 and C4 photosynthetic pathways cannot explain C4 grass invasion into forests, but that fire is a crucial driver. Fire-promoting plant traits serve to expand the climate space in which C4-dominated biomes can persist., We propose that three mechanisms were involved in C4 expansion: the physiological advantage of C4 grasses under low atmospheric CO2 allowed them to invade C3 grasslands; fire allowed grasses to invade forests; and the evolution of fire-resistant savanna trees expanded the climate space that savannas can invade. [ABSTRACT FROM AUTHOR]

The mapping of functional traits onto chronograms is an emerging approach for the identification of how agents of natural selection have shaped the evolution of organisms. Recent research has reported fire-dependent traits appearing among flowering plants from 60 million yr ago (Ma). Although there are many records of fossil charcoal in the Cretaceous (65-145 Ma), evidence of fire-dependent traits evolving in that period is lacking. [ABSTRACT FROM AUTHOR]

Species distribution model (SDM) projections under future climate scenarios are increasingly being used to inform resource management and conservation strategies. A critical assumption for projecting climate change responses is that SDMs are transferable through time, an assumption that is largely untested because investigators often lack temporally independent data for assessing transferability. Further, understanding how the ecology of species influences temporal transferability is critical yet almost wholly lacking. This raises two questions. (1) Are SDM projections transferable in time? (2) Does temporal transferability relate to species ecological traits? To address these questions we developed SDMs for 133 vascular plant species using data from the mountain ranges of California (USA) from two time periods: the 1930s and the present day. We forecast historical models over 75 years of measured climate change and assessed their projections against current distributions. Similarly, we hindcast contemporary models and compared their projections to historical data. We quantified transferability and related it to species ecological traits including physiognomy, endemism, dispersal capacity, fire adaptation, and commonness. We found that non-endemic species with greater dispersal capacity, intermediate levels of prevalence, and little fire adaptation had higher transferability than endemic species with limited dispersal capacity that rely on fire for reproduction. We demonstrate that variability in model performance was driven principally by differences among species as compared to model algorithms or time period of model calibration. Further, our results suggest that the traits correlated with prediction accuracy in a single time period may not be related to transferability between time periods. Our findings provide a priori guidance for the suitability of SDM as an approach for forecasting climate change responses for certain taxa. [ABSTRACT FROM AUTHOR]

Fire plays an important role in the evolution of life-history characteristics of organisms living in fire-prone regions. Although there are many reports of plants exhibiting adaptations to reduce the harmful or lethal effects of fire, little is known about fire-resistance mechanisms among animals, other than fleeing responses. Here, we report observations that may represent a type of fire adaptation in a bird species: bowers in one population of the Great Bowerbird Chlamydera nuchalis remained unburned after fire. If a bower is destroyed by fire or other mechanisms during courtship and breeding season, the male may lose the opportunity to mate with females, thereby reducing his apparent fitness. Therefore, traits that minimise the damage to bowers from fires may be beneficial. By measuring the unburned areas surrounding bowers after fires, we showed that the survival of bowers after fires is unlikely to be solely related to chance. Our observations are consistent with the hypothesis that bower resistance to fire is an adaptation of the Great Bowerbird. However, it is also possible that unburned bowers are by-products of sexual selection. [ABSTRACT FROM AUTHOR]

The hypocotyls or roots of many seed plants contract during seedling growth. Anatomical evidence is here reported for the first time that 0-fibers (gelatinous or tension wood fibers) may cause contraction of roots and hypocotyls in dicotyledonous seedlings long after germination. To document repositioning of seedling buds, selected perennials (20 dicotyledons and one cycad) native to the fire-prone pine rocklands of subtropical South Florida were germinated and measured for 4-5 mo. The height of cotyledonary nodes above the soil decreased because of axis contraction or bending in eight species. Anatomy suggested that two mechanisms operate: (I) previously well-documented collapse of parenchyma cells in two species (Convolvulaceae and Zamiaceae) and (2) newly documented production of G-fibers in six species (all Fabaceae). Contraction or bending of the hypocotyl and/or taproot moved the cotyledonary and later buds of the seedling closer to the soil surface or buried them. Bud repositioning by these mechanisms may protect the lateral buds from injury by fire or other environmental stresses and allow resprouting. [ABSTRACT FROM AUTHOR]

Abstract: Resilience against fire disturbance of Mediterranean vegetation has been frequently described. However, fire regimes change due to abandonment of local land use practices and climatic change. Thus, it is useful to know the importance of fire-specific and unspecific mechanisms during regeneration in order to predict changes in species resilience under an altered fire regime. In six burnt areas in a mountainous and in a coastal region in south-eastern Spain we collected information on fire-related germination characteristics (impact of smoke, charred wood or heat) of all abundant species. We excluded those species that predominantly recover by sprouting. According to these results (germination tests and literature research) we classified species that showed a positive reaction to any of the fire-related treatments studied as potential “fire seeders”. Germination of seven out of a total of 21 tested species was significantly increased by heat whereas germination of 11 hard-seeded species was mainly triggered by mechanical and/or chemical scarification. However, none of the tested species reacted positively to the treatments of ash, charred wood, and smoke. According to a quantitative plot-based vegetation analysis we then compared the coverage of “fire seeders” on (a) fire sites at the coast (2–3 years old) with sites of similar age in the mountains and (b) fire sites in the mountains of mid-successional stages (7–9 years) with undisturbed reference sites and areas of different types of disturbance (i.e. logging and fire break areas) but of comparable age and location. Results of comparison (a) showed that “fire seeder” coverage is below 4% and even lower in the coastal area. Comparison (b) showed similar coverage (about 15%) of “fire seeders” on the fire sites and on the fire breaks (strongly disturbed sites) whereas their abundance on logging and undisturbed reference sites was significantly lower. Thus, the term “fire seeder” might be misleading as fire impact is not essential for inducing germination of heat-triggered seeds. In south-eastern Spain, the low abundance of “fire seeders” and their successful regeneration on other disturbed sites are in line with historically early and strong human disturbance and low fire frequencies as the fuel load is limited due to the dry conditions. The tested species are not dependent on a certain regular fire impact though strong disturbance is very favourable for the creation of dense populations. [Copyright &y& Elsevier]

To determine the geographical variation in serotiny in a common New Zealand shrub as a contemporary indicator of past fire regimes. The distribution of serotiny could then be used to explore factors limiting the spread of fire-dependent vegetation. South Island, New Zealand. Serotiny was assessed as the proportion of closed capsules on a shoot of standard stem diameter for 5–35 plants in 45 widely scattered populations of Leptospermum scoparium. Site characteristics, including locality, altitude, rainfall, habitat type and minimum burnable area were recorded at sampling sites. Serotiny was distributed bimodally within and among populations with capsules either mostly closed or mostly open. There was considerable geographical variation in capsule behaviour, most of which we attribute to variation in fire history. In wetlands and other sites unsuitable for forest growth, populations were all serotinous above a minimum area of 30 km2 and nonserotinous below this threshold. In grassy habitats in the drier eastern areas, most populations were serotinous. The nonserotinous exceptions occurred in areas thought to have been cleared of forests by Polynesian settlers before the arrival of Europeans or in areas with numerous barriers to fire in the form of large rivers, floodplains, glaciers and barren mountain tops. We suggest that serotiny in L. scoparium is a reflection of a long history of fire in the South Island. As such, it provides a contemporary signature of a past fire regime. Landscape barriers to the spread of fire were major obstacles limiting the spread of serotiny and associated fire-dependent vegetation. Rivers, lakes, glaciers, and sparsely vegetated floodplains prevented the spread of fire in high rainfall regions more than the lack of dry weather. People, by igniting fires in small open areas seldom struck by lightning, could radically increase the importance of fire on islands. [ABSTRACT FROM AUTHOR]

The life history of Spanish pines and their relation to fire as the main disturbance factor in their ecosystems was analysed. The primary ecological attributes studied were the canopy seed bank (onset of cone production, percentage and persistence of serotinous cones), seed and cone morphology, sprouting and bark thickness. Four ecological groups were separated using multivariate cluster analysis and their life-history characteristics are discussed. Serotiny and early flowering in Pinus halepensis and P. pinaster reflect their evader strategy in relation to fire as this character is advantageous to survive frequent crown fires and to attain successful post-fire recruitment. Late flowering and absence of serotinous cones in P. nigra, P. sylvestris and P. uncinata indicate that their natural forest did not evolve under frequent crown fires. P. canariensis and P. pinea appeared in two single groups because of their sprouting capability and their seed size respectively. Intraspecific variation in P. pinaster was also analysed using the same criteria and high variability was found in its life history traits. A group of P. pinaster populations showed high levels of serotiny and thin bark as a possible adaptation to frequent stand-replacing crown fires. In contrast, a group of non- or weakly-serotinous populations seems to have evolved under a low-intensity fire regime where the best fitness corresponds to thick-barked individuals capable of surviving ground fires. Intermediate strategies were also evident in this species and were discussed in relation to the effect of different fire regimes caused by the understorey vegetation. [ABSTRACT FROM AUTHOR]

Longleaf pine (Pinus palustris Mill.) forest is a well-known fire-dependent ecosystem. The historical dominance of longleaf pine in the southeast United States has been attributed to its adaptation known as the grass stage, which allows longleaf pine seedlings to survive under a frequent surface fire regime. However, factors affecting post-fire survival of grass stage seedlings are not well understood. In this study, we measured live and dead longleaf pine grass stage seedlings to quantify the role of seedling size, root collar position, and sprouting in seedling survival following a wildfire in the sandhills of South Carolina. We found that fire resulted in almost 50% mortality for longleaf pine grass stage seedlings. Fire survival rate increased with seedling size, but a size threshold for fire tolerance was not supported. Fire survival depended on the position of root collar relative to the mineral soil. Seedlings with protected root collars (i.e., buried in or at the level of mineral soil) experienced <21%, while seedlings with exposed root collars (i.e., elevated above mineral soil) suffered >90% post-fire mortality. Ability to resprout contributed to 45.6% of the total fire survival, with the small seedlings (root collar diameter (RCD) < 7.6 mm) almost exclusively depending on resprouting. Our findings had significant implications for fire management in longleaf pine ecosystems, and the current frequency of prescribed fire in sandhills might need to be lengthened to facilitate longleaf pine natural regeneration. [ABSTRACT FROM AUTHOR]

How coniferous forests evolved in the Northern Hemisphere remains largely unknown. Unlike most groups of organisms that generally follow a latitudinal diversity gradient, most conifer species in the Northern Hemisphere are distributed in mountainous areas at middle latitudes. It is of great interest to know whether the midlatitude region has been an evolutionary cradle or museum for conifers and how evolutionary and ecological factors have driven their spatiotemporal evolution. Here, we investigated the macroevolution of Pinus , the largest conifer genus and characteristic of northern temperate coniferous forests, based on nearly complete species sampling. Using 1,662 genes from transcriptome sequences, we reconstructed a robust species phylogeny and reestimated divergence times of global pines. We found that ∼90% of extant pine species originated in the Miocene in sharp contrast to the ancient origin of Pinus , indicating a Neogene rediversification. Surprisingly, species at middle latitudes are much older than those at other latitudes. This finding, coupled with net diversification rate analysis, indicates that the midlatitude region has provided an evolutionary museum for global pines. Analyses of 31 environmental variables, together with a comparison of evolutionary rates of niche and phenotypic traits with a net diversification rate, found that topography played a primary role in pine diversification, and the aridity index was decisive for the niche rate shift. Moreover, fire has forced diversification and adaptive evolution of Pinus Our study highlights the importance of integrating phylogenomic and ecological approaches to address evolution of biological groups at the global scale., Competing Interests: The authors declare no competing interest., (Copyright © 2021 the Author(s). Published by PNAS.)