Increase of genetic diversity indicates ecological opportunities in recurrent-fire landscapes for wall lizards

Fire-driven animal evolution in the Pyrocene

Fire regimes are a major agent of evolution in terrestrial animals. Changing fire regimes and the capacity for rapid evolution in wild animal populations suggests the potential for rapid, fire-driven adaptive animal evolution in the Pyrocene. Fire drives multiple modes of evolutionary change, including stabilizing, directional, disruptive, and fluctuating selection, and can strongly influence gene flow and genetic drift. Ongoing and future research in fire-driven animal evolution will benefit from further development of generalizable hypotheses, studies conducted in highly responsive taxa, and linking fire-adapted phenotypes to their underlying genetic basis. A better understanding of evolutionary responses to fire has the potential to positively influence conservation strategies that embrace evolutionary resilience to fire in the Pyrocene.

Bioactivity analysis of calcium silicate-based sealers and repair cements on the phenotype and cytokine secretion profile of CD14+ monocytes: An ex vivo study

AIM

This study evaluated the immune bioactivity of testing media (TM) obtained from different calcium silicate-based sealers and cements on monocyte morphology, activation, differentiation and cytokine secretion.

METHODS

Blood-derived CD14⁺ monocytes were isolated and cultured for 5 days with 25% TM from the following calcium silicate-based materials: TotalFill BC RRM Fast-Set Putty, Biodentine, TotalFill BC Sealer and BioRoot-Root-Canal-Sealer (RCS). A resin-based endodontic cement was used as a control. The expression of surface markers such as CD86, HLA-DR, CD16, CD309 and CD209, and cytokine secretion were analysed by flow cytometry. Data were analysed using the one-way repeated measures analysis of variance (anova) multiple comparison test and a Holm-Sidak multiple comparison post-hoc test (p < .05).

RESULTS

This comparative analysis revealed that monocytes co-cultured with calcium silicate-based materials showed a spindle-shaped morphology compared with the round shape observed in the control. Regarding activation markers, BioRoot-RCS and Biodentine significantly increased CD86 expression compared with the control sample, whereas no significant differences (p > .05) were observed in HLA-DR expression. In addition, no differences were observed among the differentiation markers. When the inflammatory cytokines were analysed, BioRoot-RCS increased the secretion of IL-1β, IL-6, IL-10 and TNF-α, whereas BioRoot-RCS and Biodentine significantly decreased IL-8 production (p < .05).

CONCLUSIONS

These data showed that the calcium silicate-based materials tested changed the morphology of CD14⁺ monocytes; however, only BioRoot-RCS and Biodentine significantly upregulated CD86. In addition, BioRoot-RCS was the sealer with the highest immunomodulatory properties for cytokine production which means that it can contribute with the in vivo healing process and regeneration of periapical lesions.

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.

Altered fire regimes modify lizard communities in globally endangered Araucaria forests of the southern Andes

Wildfire regimes are being altered in ecosystems worldwide. The density of reptiles responds to fires and changes to habitat structure. Some of the most vulnerable ecosystems to human-increased fire frequency are old-growth Araucaria araucana forests of the southern Andes. We investigated the effects of wildfires on the density and richness of a lizard community in these ecosystems, considering fire frequency and elapsed time since last fire. During the 2018/2019 southern summer season, we conducted 71 distance sampling transects to detect lizards in Araucaria forests of Chile in four fire "treatments": (1) unburned control, (2) long-term recovery, (3) short-term recovery, and (4) burned twice. We detected 713 lizards from 7 species. We found that the density and richness of lizards are impacted by wildfire frequency and time of recovery, mediated by the modification of habitat structure. The lizard community varied from a dominant arboreal species (L. pictus) in unburned and long-recovered stands, to a combination of ground-dwelling species (L. lemniscatus and L. araucaniensis) in areas affected by two fires. Araucaria forests provided key habitat features to forest reptiles after fires, but the persistence of these old-growth forests and associated biodiversity may be threatened given the increase in fire frequency.

Impacts of Fire on Butterfly Genetic Diversity and Connectivity

How do novel fire regimes and a long history of fire suppression influence species genetic diversity? Genetic diversity provides the raw materials for sustaining viable populations and for allowing adaptation to novel environmental challenges, and at present, few studies address the genetic responses of animals to fire management. Here we study the genetic responses of 2 butterfly species to a landscape gradient of fire timing and severity in Yosemite National Park using a large set of genome-wide single nucleotide polymorphisms (SNPs). Butterflies are important bio-indicators of invertebrate diversity and play important roles in both bottom-up and top-down ecosystem processes, and typically increase in abundance following wildfires, due to an increase in abundance of flowering plants. However, it is not clear how genetic diversity and genetic connectivity of butterflies respond to landscape change following fire, and whether fire management has positive or negative effects. We found evidence to suggest that fire increases genetic diversity and reduces isolation in 2 butterfly species, but that aspects of the fire regime (severity, extent, timing, and frequency) differ in importance depending on the ecology of the specific species. This research is the first study to address fire management impacts on genetic diversity in invertebrates, and the results will allow fire managers to predict that fire reintroduction in protected areas will generally benefit butterfly populations.

Wildfire effects on diversity and composition in soil bacterial communities

In recent years, the Mediterranean area has witnessed an increase of both the frequency and severity of large fires, which appears to be intimately associated with climate and land use changes. To measure the impact of wildfires on living organisms, diverse indicators have been proposed. These indicators of fire severity traditionally rely on quantifying the damage caused to the vegetal component of ecosystems. However, the use of bacterial communities as severity indicators has received less attention. Here, we studied the differences between bacterial communities of three different Mediterranean ecosystems, two shrubby and one arboreal, two months after a large wildfire. Two levels of severity were compared to a control unburnt soil. The results showed that greater fire severity triggers a reduction in the diversity of soil bacterial communities. In high-severity fires, this reduction reached 40.6 and 58.6% of the control values for richness and Shannon's diversity, respectively. We also found that the greatest differences between communities could be attributed first to the severity of the fire, and second to the ecosystem from which they originated. Importantly, species of just five families of bacteria: Oxalobacteraceae, Micrococcaceae, Paenibacillaceae, Bacillaceae and Planococcaceae, became dominant in all three ecosystems. The average frequency increase for particular species was 100 times. However, due to random uncontrolled factors, the species that became dominant in each community were not always the same.

Integrating functional connectivity and fire management for better conservation outcomes

Globally, the mean abundance of terrestrial animals has fallen by 50% since 1970, and populations face ongoing threats associated with habitat loss, fragmentation, climate change, and disturbance. Climate change can influence the quality of remaining habitat directly and indirectly by precipitating increases in the extent, frequency, and severity of natural disturbances, such as fire. Species face the combined threats of habitat clearance, changing climates, and altered disturbance regimes, each of which may interact and have cascading impacts on animal populations. Typically, conservation agencies are limited in their capacity to mitigate rates of habitat clearance, habitat fragmentation, or climate change, yet fire management is increasingly used worldwide to reduce wildfire risk and achieve conservation outcomes. A popular approach to ecological fire management involves the creation of fire mosaics to promote animal diversity. However, this strategy has 2 fundamental limitations: the effect of fire on animal movement within or among habitat patches is not considered and the implications of the current fire regime for long-term population persistence are overlooked. Spatial and temporal patterns in fire history can influence animal movement, which is essential to the survival of individual animals, maintenance of genetic diversity, and persistence of populations, species, and ecosystems. We argue that there is rich potential for fire managers to manipulate animal movement patterns; enhance functional connectivity, gene flow, and genetic diversity; and increase the capacity of populations to persist under shifting environmental conditions. Recent methodological advances, such as spatiotemporal connectivity modeling, spatially explicit individual-based simulation, and fire-regime modeling can be integrated to achieve better outcomes for biodiversity in human-modified, fire-prone landscapes. Article impact statement: Land managers may conserve populations by using fire to sustain or enhance functional connectivity.

Post-fire effects on development of leaves and secondary vascular tissues in Quercus pubescens

An increased frequency of fire events on the Slovenian Karst is in line with future climate change scenarios for drought-prone environments worldwide. It is therefore of the utmost importance to better understand tree-fire-climate interactions for predicting the impact of changing environment on tree functioning. To this purpose, we studied the post-fire effects on leaf development, leaf carbon isotope composition (δ13C), radial growth patterns and the xylem and phloem anatomy in undamaged (H-trees) and fire-damaged trees (F-trees) of Quercus pubescens Willd. with good resprouting ability in spring 2017, the growing season after a rangeland fire in August 2016. We found that the fully developed canopy of F-trees reached only half of the leaf area index values measured in H-trees. Throughout the season, F-trees were characterized by higher water potential and stomatal conductivity and achieved higher photosynthetic rates compared to unburnt H-trees. The foliage of F-trees had more negative δ13C values than those of H-trees. This reflects that F-trees less frequently meet stomatal limitations due to reduced transpirational area and more favourable leaf-to-root ratio. In addition, the growth of leaves in F-trees relied more on the recent photosynthates than on reserves due to the fire disturbed starch accumulation in the previous season. Cambial production stopped 3 weeks later in F-trees, resulting in 60 and 22% wider xylem and phloem increments, respectively. A novel approach by including phloem anatomy in the analyses revealed that fire caused changes in conduit dimensions in the early phloem but not in the earlywood. However, premature formation of the tyloses in the earlywood vessels of the youngest two xylem increments in F-trees implies that xylem hydraulic integrity was also affected by heat. Analyses of secondary tissues showed that although xylem and phloem tissues are interlinked changes in their transport systems due to heat damage are not necessarily coordinated.

Hurricane-induced disturbance increases genetic diversity and population admixture of the direct-brooding isopod, Gnathia marleyi

Severe disturbances can substantially alter eco-evolutionary processes and dynamics. While the impacts of catastrophic events on the biophysical attributes of communities are sometimes assessed, their effects on the genetic patterns of species remain poorly understood. To characterize how severe disturbances impact species at the molecular level, we examined the effects of the most energetic North Atlantic hurricane season in 50 years on the genetic diversity and structure of a dispersal-limited isopod, Gnathia marleyi. We sequenced a portion of the cytochrome oxidase I gene for 432 gnathiids, collected from six localities, ranging from western Puerto Rico to St John, US Virgin Islands. Importantly, multiple years of pre-hurricane sample collection allowed us to characterize temporal genetic patterns under undisturbed conditions and detect the changes subsequent to the 2017 hurricanes. Our results revealed no change to genetic diversity or structure for the years prior to the 2017 hurricanes, with genetic structure occurring at the local and regional levels, with three main clusters corresponding to Southwest Puerto Rico, East Puerto Rico, and the US Virgin Islands. However, directly following the 2017 hurricanes, genetic diversity increased at five of the six sampled localities. Additionally, we found a clear homogenizing effect prompted by increased shared genetic diversity among geographically distant regions and sites that resulted in substantially decreased among-region and among-site differentiation. Our work shows that severe disturbances caused by major tropical hurricanes facilitate gene-flow and increase overall genetic diversity and population admixture of dispersal limited coral reef species, potentially impacting the ecology and evolution of a key regional endemic.