A monthly gridded burned area database of national wildland fire data.

We assembled the first gridded burned area (BA) database of national wildfire data (ONFIRE), a comprehensive and integrated resource for researchers, non-government organisations, and government agencies analysing wildfires in various regions of the Earth. We extracted and harmonised records from different regions and sources using open and reproducible methods, providing data in a common framework for the whole period available (starting from 1950 in Australia, 1959 in Canada, 1985 in Chile, 1980 in Europe, and 1984 in the United States) up to 2021 on a common 1° × 1° grid. The data originate from national agencies (often, ground mapping), thus representing the best local expert knowledge. Key opportunities and limits in using this dataset are discussed as well as possible future expansions of this open-source approach that should be explored. This dataset complements existing gridded BA data based on remote sensing and offers a valuable opportunity to better understand and assess fire regime changes, and their drivers, in these regions. The ONFIRE database can be freely accessed at https://zenodo.org/record/8289245 .

Fire effects on pollination and plant reproduction: a quantitative review.

BACKGROUND AND AIMS: Fire may favour plant flowering by opening the vegetation and increasing abiotic resource availability. Increased floral display size can attract more pollinators and increase the absolute fruit and seed production immediately after the fire. However, anthropogenic increases in fire frequency may alter these responses. We aim to assess the effects of fire on pollination and reproductive success of plants at the global scale. METHODS: We performed a systematic literature review and meta-analyses to examine overall fire effects as well as different fire parameters on pollination and on plant reproduction. We also explored to what extent the responses vary among pollinators, pollination vectors, plant regeneration strategies, compatibility systems, vegetation types and biomes. KEY RESULTS: Most studies were conducted in fire-prone ecosystems. Overall, single fires increased pollination and plant reproduction but this effect was overridden by recurrent fires. Floral visitation rates of pollinators were enhanced immediately following a wildfire, and especially in bee-pollinated plants. Fire increased the absolute production of fruits or seeds but not the fruit or seed set. The reproductive benefits were mostly observed in wind-pollinated (graminoids), herbaceous and resprouter species. Finally, fire effects on pollination were positively correlated with fire effects on plant reproductive success. CONCLUSIONS: Fire has a central role in pollination and plant sexual reproduction in fire-prone ecosystems. The increase in the absolute production of fruits and seeds suggests that fire benefits on plant reproduction are likely driven by increased abiotic resources and the consequent floral display size. However, reproduction efficiency, as measured by fruit or seed set, does not increase with fire. In contrast, when assessed on the same plant simultaneously, fire effects on pollination are translated into reproduction. Increased fire frequency due to anthropogenic changes can alter the nature of the response to fire.

Fire ecology in marine systems.

Wildfire byproducts enter into the oceans via terrestrial and atmospheric routes. They pose a challenge to the sustainability of marine ecosystems, especially under the current increase in fire activity. Research is needed to unravel the dynamics between wildfires and marine life, and the oceans' potential to mitigate wildfire emissions.

Postfire biodiversity database for eastern Iberia.

In the summer of 2012, two fires affected Mediterranean ecosystems in the eastern Iberian Peninsula. The size of these fires was at the extreme of the historical variability (megafires). Animals are traditionally assumed to recolonize from source populations outside of the burned area (exogenous regeneration) while plants recover from endogenous regeneration (resprouting and seeding). However, there is increasing evidence of in situ fire survival in animals. To evaluate the effect of large-scale fires on biodiversity and the mechanism of recovery, in 2013, we set up 12 plots per fire, covering burned vegetation at different distances from the fire perimeter and unburned vegetation. In each plot, we followed the postfire recovery of arthropods, reptiles (including some of their parasites), and plants for 2 to 5 years. Here we present the resulting database (POSTDIV) of taxon abundance. POSTDIV totals 19,906 records for 457 arthropod taxa (113,681 individuals), 12 reptile taxa (503 individuals), 4 reptile parasites (234 individuals), and 518 plant taxa (cover-abundance). We provide examples in the R language to query the database.

Development and characterization of microsatellite loci in Ulex parviflorus Pourr. And its cross-transferability to other Genisteae.

BACKGROUND: The genus Ulex is composed by 15 species distributed in Europe and Africa, but the majority of them are restricted to the Iberian Peninsula and Northwest Africa. Some of these species are common elements at the landscape level, and others contribute to global biodiversity as narrow endemics. Assayed nuclear and plastid Sanger-sequenced regions do not provide enough resolution to perform evolutionary studies on the genus, neither at the intraspecific population level nor at the interspecific phylogenetic level. Thus, we have developed and characterized a set of nuclear microsatellite loci in U. parviflorus to provide new highly polymorphic molecular markers for the genus Ulex. METHODS AND RESULTS: Genomic DNA enriched in microsatellite motifs using streptavidin-coated M-280 magnetic beads attached to 5'-biotinylated oligonucleotides was sequenced in a 454GS Junior System. After primer design, fluorescent-dyed amplicons were analyzed through capillary sequencing (ABI3730XL). Here we present twelve new high polimorphic SSRs markers developed in U. parviflorus specimens and tested in 120 individuals. The 12 SSR loci amplified a total of 152 alleles, and detected expected heterozygosities that ranged from 0.674 to 0.725 in the genotyped populations. Successful cross-species transferability of the 12 SSR loci to the rest of species included in the genus Ulex and three other representative Genisteae was achieved. CONCLUSIONS: The 12 novel proposed SSRs loci will contribute to perform evolutionary studies and genetic research on the genus Ulex and in other Genisteae.

Evolutionary fire ecology: An historical account and future directions.

The idea that fire acts as an evolutionary force contributing to shaping species traits started a century ago, but had not been widely recognized until very recently. Among the first to realize this force were Edward B. Poulton, R. Dale Guthrie, and Edwin V. Komarek in animals and Willis L. Jepson, Walter W. Hough, Tom M. Harris, Philip V. Wells, and Robert W. Mutch in plants. They were all ahead of their time in their evolutionary thinking. Since then, evolutionary fire ecology has percolated very slowly into the mainstream ecology and evolutionary biology; in fact, this topic is still seldom mentioned in textbooks of ecology or evolution. Currently, there is plenty of evidence suggesting that we cannot understand the biodiversity of our planet without considering the key evolutionary role of fire. But there is still research to be done in order to fully understand fire's contribution to species evolution and to predicting species responses to rapid global changes.

Quantitative genetic analysis of floral traits shows current limits but potential evolution in the wild.

The vast variation in floral traits across angiosperms is often interpreted as the result of adaptation to pollinators. However, studies in wild populations often find no evidence of pollinator-mediated selection on flowers. Evolutionary theory predicts this could be the outcome of periods of stasis under stable conditions, followed by shorter periods of pollinator change that provide selection for innovative phenotypes. We asked if periods of stasis are caused by stabilizing selection, absence of other forms of selection or by low trait ability to respond even if selection is present. We studied a plant predominantly pollinated by one bee species across its range. We measured heritability and evolvability of traits, using genome-wide relatedness in a large wild population, and combined this with estimates of selection on the same individuals. We found evidence for both stabilizing selection and low trait heritability as potential explanations for stasis in flowers. The area of the standard petal is under stabilizing selection, but the variability is not heritable. A separate trait, floral weight, presents high heritability, but is not currently under selection. We show how a simple pollination environment coincides with the absence of current prerequisites for adaptive evolutionary change, while heritable variation remains to respond to future selection pressures.

Impact of roadside burning on genetic diversity in a high-biomass invasive grass.

The invasive grass-fire cycle is a widely documented feedback phenomenon in which invasive grasses increase vegetation flammability and fire frequency, resulting in further invasion and compounded effects on fire regimes. Few studies have examined the role of short-term adaptation in driving the invasive grass-fire cycle, despite invasive species often thriving after introduction to new environments. We used a replicated (nine locations), paired sampling design (burn vs unburnt sites) to test the hypothesis that roadside burning increases genetic diversity and thus adaptive potential in the invasive, high-biomass grass Cenchrus ciliaris. Between four and five samples per site (n = 93) were genotyped using the DArTseq platform, and we filtered the data to produce panels of 15,965 neutral and 5030 non-neutral single nucleotide polymorphism (SNP) markers. Using fastSTRUCTURE, we detected three distinct genetic clusters with extremely high F ST values among them (0.94-0.97) suggesting three different cultivars. We found high rates of asexual reproduction, possibly related to clonality or apomixis common in this species. At three locations, burnt and unburnt sites were genetically different, but genetic structure was not consistently related to fire management across the study region. Burning was associated with high genetic diversity and sexual reproduction in one genetic cluster, but with low genetic diversity and clonality in another. Individual SNPs were associated with longitude and genetic clustering, but not with recent fire management. Overall, we found limited evidence that roadside burning consistently increased genetic diversity and adaptive potential in C. ciliaris; evolutionary and breeding history more strongly shaped genetic structure. Roadside burning could therefore continue to be used for managing biomass in this species, with continued monitoring. Our study provides a framework for detecting fire-related changes on a genetic level-a process that could be used as an early warning system to detect the invasive grass-fire cycle in future.

Feedbacks in ecology and evolution.

Ecology and evolutionary biology have focused on how organisms fit the environment. Less attention has been given to the idea that organisms can also modify their environment, and that these modifications can feed back to the organism, thus providing a key factor for their persistence and evolution. There are at least three independent lines of evidence emphasizing these biological feedback processes at different scales: niche construction (population scale); alternative biome states (community scale); and the Gaia hypothesis (planetary scale). These feedback processes make us rethink traditional concepts like niche and adaptation. We argue that organism-environment feedbacks must become a regular part of ecological thinking, especially now that the Earth is quickly changing.

Fire-released seed dormancy - a global synthesis.

Seed dormancy varies greatly between species, clades, communities, and regions. We propose that fireprone ecosystems create ideal conditions for the selection of seed dormancy as fire provides a mechanism for dormancy release and postfire conditions are optimal for germination. Thus, fire-released seed dormancy should vary in type and abundance under different fire regimes. To test these predictions, we compiled data from a wide range of fire-related germination experiments for species in different ecosystems across the globe. We identified four dormancy syndromes: heat-released (physical) dormancy, smoke-released (physiological) dormancy, non-fire-released dormancy, and non-dormancy. In fireprone ecosystems, fire, in the form of heat and/or chemical by-products (collectively termed 'smoke'), are the predominant stimuli for dormancy release and subsequent germination, with climate (cold or warm stratification) and light sometimes playing important secondary roles. Fire (heat or smoke)-released dormancy is best expressed where woody vegetation is dense and fires are intense, i.e. in crown-fire ecosystems. In such environments, seed dormancy allows shade-intolerant species to take advantage of vegetation gaps created by fire and synchronize germination with optimal recruitment conditions. In grassy fireprone ecosystems (e.g. savannas), where fires are less intense but more frequent, seed dormancy is less common and dormancy release is often not directly related to fire (non-fire-released dormancy). Rates of germination, whether controls or postfire, are twice as fast in savannas than in mediterranean ecosystems. Fire-released dormancy is rare to absent in arid ecosystems and rainforests. The seeds of many species with fire-released dormancy also possess elaiosomes that promote ant dispersal. Burial by ants increases insulation of seeds from fires and places them in a suitable location for fire-released dormancy. The distribution of these dormancy syndromes across seed plants is not random - certain dormancy types are associated with particular lineages (phylogenetic conservatism). Heat-released dormancy can be traced back to fireprone floras in the 'fiery' mid-Cretaceous, followed by smoke-released dormancy, with loss of fire-related dormancy among recent events associated with the advent of open savannas and non-fireprone habitats. Anthropogenic influences are now modifying dormancy-release mechanisms, usually decreasing the role of fire as exaptive effects. We conclude that contrasting fire regimes are a key driver of the evolution and maintenance of diverse seed dormancy types in many of the world's natural ecosystems.

Fire and summer temperatures interact to shape seed dormancy thresholds.

BACKGROUND AND AIMS: In Mediterranean ecosystems, the heat shock of wildfire disrupts physical seed dormancy in many plant species. This triggers germination in the post-fire environment where seedling establishment is optimal due to decreased competition and increased resource availability. However, to maintain the soil seed bank until a fire occurs, the minimum heat capable of breaking seed dormancy (i.e. the lower heat threshold) must be above the maximum temperatures typically observed in the soil during the summer. We therefore hypothesized that summer temperatures have shaped heat requirements for physical dormancy release. Specifically, we predicted that seeds from populations growing under warmer summers will have higher values of the lower heat threshold. METHODS: To evaluate this prediction, we collected seeds from two Cistus species in 31 populations (20 Cistus albidus and 11 Cistus salviifolius) along a climate gradient of summer temperatures on the eastern coast of Spain. For each population, seeds were treated to 10 min heat shocks, from 30 to 120 °C in 5 °C increments (19 treatments), to simulate increasing heat doses from summer to fire-related temperatures. Seeds were then germinated in the lab. KEY RESULTS: For all populations, maximum germination was observed when applying temperatures associated with fire. Lower heat thresholds varied among populations, with a positive relationship between summer temperatures at seed population origin and the heat dose required to break dormancy. CONCLUSIONS: Our results suggest that fire drives maximum dormancy release for successful post-fire germination, while summer temperatures determine lower heat thresholds for ensuring inter-fire seed bank persistence. Significant among-population variation of thresholds also suggests that post-fire seeder species have some potential to modify their dormancy release requirements in response to changing climate.

Turkish postfire action overlooks biodiversity.

[Figure: see text].

The legacy of the extinct Neotropical megafauna on plants and biomes.

Large mammal herbivores are important drivers of plant evolution and vegetation patterns, but the extent to which plant trait and ecosystem geography currently reflect the historical distribution of extinct megafauna is unknown. We address this question for South and Central America (Neotropical biogeographic realm) by compiling data on plant defence traits, climate, soil, and fire, as well as on the historical distribution of extinct megafauna and extant mammal herbivores. We show that historical mammal herbivory, especially by extinct megafauna, and soil fertility explain substantial variability in wood density, leaf size, spines and latex. We also identified three distinct regions (''antiherbiomes''), differing in plant defences, environmental conditions, and megafauna history. These patterns largely matched those observed in African ecosystems, where abundant megafauna still roams, and suggest that some ecoregions experienced savanna-to-forest shifts following megafauna extinctions. Here, we show that extinct megafauna left a significant imprint on current ecosystem biogeography.

Resilience of reptiles to megafires.

Extreme climate events, together with anthropogenic land-use changes, have led to the rise of megafires (i.e., fires at the top of the frequency size distribution) in many world regions. Megafires imply that the center of the burnt area is far from the unburnt; therefore, recolonization may be critical for species with low dispersal abilities such as reptiles. We aimed to evaluate the effect of megafires on a reptile community, exploring to what extent reptile responses are spatially shaped by the distance to the unburnt area. We examined the short-term spatiotemporal response of a Mediterranean reptile community after two megafires (>20,000 ha) that occurred in summer 2012 in eastern Spain. Reptiles were sampled over 4 years after the fire in burnt plots located at different distances from the fire perimeter (edge, middle, and center), and in adjacent unburnt plots. Reptile responses were modeled with fire history, as well as climate and remotely sensed environmental variables. In total, we recorded 522 reptiles from 12 species (11 species in the burnt plots and nine in the unburnt plots). Reptile abundance decreased in burnt compared with unburnt plots. The community composition and species richness did not vary either spatially (unburnt and burnt plots) or temporally (during the 4 years). The persistence of reptiles in the burnt area supported their resilience to megafires. The most common lizard species was Psammodromus algirus; both adults and juveniles were found in all unburnt and burnt plots. This species showed lower abundances in burnt areas compared with the unburnt and a slow short-term abundance recovery. The lizard Psammodromus edwarsianus was much less abundant and showed a tendency to increase its abundance in burnt plots compared with unburnt plots. Within the megafire area, P. algirus and P. edwarsianus abundances correlated with the thermal-moisture environment and vegetation recovery regardless of the distance from the fire edge. These results indicated the absence of a short-term reptile recolonization from the unburnt zone, demonstrating that reptiles are resilient (in situ persistence) to megafires when environmental conditions are favorable.

Fire reduces parasite load in a Mediterranean lizard.

Wildfires are a natural disturbance in many ecosystems. However, their effect on biotic interactions has been poorly studied. Fire consumes the vegetation and the litter layer where many parasites spend part of their life cycles. We hypothesize that wildfires reduce habitat availability for parasites with consequent potential benefits for hosts. We tested this for the lizard Psammodromus algirus and its ectoparasites in a Mediterranean ecosystem. We predicted that lizards in recently burned areas would have lower parasite load (cleaning effect) than those in unburned areas and that this phenomenon implies that lizards spending their entire lives in postfire conditions experience a lower level of parasitism than those living in unburned areas. We compared the ectoparasite load of lizards between eight paired burned/unburned sites, including recent (less than 1 year postfire) and older fires (2-4 years). We found that lizards' ectoparasites prevalence was drastically reduced in recently burned areas. Likewise, lizards in older burned areas showed less evidence of past parasitic infections. Fire disrupted the host-parasite interaction, providing the opportunity for lizards to avoid the negative effects of ectoparasites. Our results suggest that wildfires probably fulfil a role in controlling vector-borne diseases and pathogens, and highlight ecological effects of wildfires that have been overlooked.

Functional trait effects on ecosystem stability: assembling the jigsaw puzzle.

Under global change, how biological diversity and ecosystem services are maintained in time is a fundamental question. Ecologists have long argued about multiple mechanisms by which local biodiversity might control the temporal stability of ecosystem properties. Accumulating theories and empirical evidence suggest that, together with different population and community parameters, these mechanisms largely operate through differences in functional traits among organisms. We review potential trait-stability mechanisms together with underlying tests and associated metrics. We identify various trait-based components, each accounting for different stability mechanisms, that contribute to buffering, or propagating, the effect of environmental fluctuations on ecosystem functioning. This comprehensive picture, obtained by combining different puzzle pieces of trait-stability effects, will guide future empirical and modeling investigations.