Terminal Period Research Articles

Ancient Conflagration: a Reconstruction of a Middle Formative Fire at the Chiripa Mound, Bolivia

In this study, we assess competing interpretations of a burnt ceremonial structure from the terminal Middle Formative period (ca. 300–100 BCE) by analyzing the stepped platform mound at Chiripa, Bolivia, through a systematic reconstruction of the fire that destroyed it. We developed a model of potential fire pathways, their social contexts, and material indicators. Our approach contrasts incipient fires from accident or arson to planned fires initiated for functional or social ends. We assessed these pathways for the Chiripa mound fire through experimental, geoarchaeological, faunal, and botanical data. Experiments were aimed at deducing the temperature, duration, and oxidation conditions of the fire. The fire temperature and duration were approximated from geoarchaeological analyses of construction materials in comparison with controls, and thermal alteration of faunal bone. Fuels were reconstructed through paleoethnobotanical analysis of charred remains from discrete areas within the burnt structure. We conclude that an intentional fire burned the structures on the Chiripa mound to temperatures of 700 °C or higher under oxidizing conditions for several hours. The pattern of heat-altered materials recovered would have required a substantial supplemental fuel load. At the 3840 masl elevation of Chiripa, the effective control of a high temperature oxidizing fire demonstrates technical expertise in fire management. Our findings indicate the fire appears intentional, likely a ritual event. We believe the structures were burned to facilitate a socio-political change during a period of social transition at the end of the Middle Formative period in Bolivia.

Late Triassic tectonic stress field of the southwestern Ordos Basin and its tectonic implications: Insights from finite-element numerical simulations

Abstract The tectonic stress field of the southwestern Ordos Basin during the Late Triassic is controversial. The major controversy is whether the southwestern Ordos Basin was a compressional basin throughout the Late Triassic or whether it transformed from an extensional into a compressional basin during this period. We divided the Late Triassic into the early to middle and late to terminal periods. Two paleotectonic stress field simulation models of the southwestern Ordos Basin were constructed using finite-element software (ANSYS 10). Our results showed high consistency with regional geologic correlations, suggesting the credibility of the models. We found that the southwestern Ordos Basin was dominated by NE-SW extensional stress and strain during the early to middle Late Triassic, associated with strike-slip faulting along the western margin of the Ordos block. This is consistent with the development of syndepositional normal faults and was probably induced by the scissor collision from east to west between the North China craton and Yangtze block. The tectonic stress field of the southwestern Ordos Basin during the late to terminal Late Triassic mainly manifested as NE-SW compressive stress and strain. The dominant tectonic dynamics for the Ordos block during this period may have changed to northward compression of the Songpan-Ganzi and Qiangtang terranes. The southwestern Ordos Basin was characterized by compressional deformation and northeastward migration of the depocenter. The southwestern Ordos Basin transformed from an extensional basin associated with strike-slip faulting during the early to middle Late Triassic into a compressional depression basin during the late to terminal Late Triassic.

Terminal Classic Conch-Shell Gorgets from the Maya Region and Central Mexico

AbstractThis article discusses a category of conch-shell gorgets, mainly semielliptical in shape, which were produced during the Terminal Classic period in central Mexico and/or the Maya lowlands. We describe the iconography and style of these ornaments, seek precedents in other media for their themes, and use stylistic and epigraphic data to connect them to long-distance economic and political interactions between the Maya region and central Mexico. Although the portraits on most of the gorgets diverge from earlier Classic Maya conventions, neither do they conform to central Mexican canons. Further discoveries of such pendants in archaeological context may clarify their origins and social uses.

A millennium of anthropic and climate dynamics in the Lake Izabal Basin, eastern lowland Guatemala

Modern precipitation gradients across the Maya region in Central America result in a diverse vegetational mosaic that varies from scrub forest to rainforest. In this region, evidence of past changes in the distribution of vegetation indicates two main patterns: i) a Holocene long-term trend towards a more seasonal forest, and ii) sharp changes in vegetation cover resulting from human occupation. The history of vegetation in moister areas of the Maya region, however, has been mostly extrapolated from studies carried out in the Yucatan Peninsula. We reconstructed the paleoenvironmental and paleoecological dynamics of the last ∼1300 years in the Lake Izabal Basin, one of the wettest areas within the Maya region. Palynological and geochemical evidences indicate that from ∼650–1150 CE, vegetation assemblages were dominated by disturbance taxa, under relatively low erosion in the catchment area. This pattern probably resulted from anthropogenic activities during the Terminal Classic Period (800–950 CE) combined with the dry and more seasonal conditions of the Medieval Climate Anomaly. The record from 1150 to 1400 CE points to an increase in moisture availability with a change towards a forested landscape. From 1400 to 1950 CE, geochemical data indicate lower precipitation, while the vegetation appears less fragmented and a mature forest developed. Such pattern probably emerged from lower evapotranspiration associated with the Little Ice Age (1350–1850 CE) favoring vegetation recovery. During the last 1300 years, vegetation change in the Lake Izabal Basin parallels that of the Yucatan Peninsula, with anthropogenic influences and moisture availability exerting first- and second-order controls on vegetation turnover, respectively.

Phosphatized microfossils from the Miaohe Member of South China and their implications for the terminal Ediacaran biodiversity decline

The upper Ediacaran Miaohe Member (∼550 Ma) in South China is well known for exceptionally preserved macroscopic carbonaceous compression fossils (i.e., the Miaohe biota) that are pivotal in understanding the marine ecology and environment during the terminal Ediacaran Period. However, micro-organisms, which are also important biotic components of marine ecosystems, are poorly documented and largely limited to simple leiospheres and filaments in the Miaohe Member and equivalent strata in South China and around the world. Here we report a moderately diverse assemblage of cellularly preserved microfossils from phosphorites and siliceous phosphorite nodules and bands of the Miaohe Member at the Maxi section, Hubei Province, South China. Ten named species of eight genera, four open nomenclatures, and two unnamed taxa have been identified, including several multicellular algal fossils and various coccoidal and filamentous cyanobacteria. Abundant spheroidal fossils are morphologically analogous to Megasphaera, which has previously been interpreted as a putative metazoan embryo. Together with previously described microfossils from equivalent strata of Miaohe Member, these microfossils expand our understanding of the evolution of marine ecosystems prior to the Cambrian explosion. The late Ediacaran Maxi assemblage and the early Ediacaran Weng’an biota, both preserved through phosphatization, share several taxa. Notably, Doushantuo-Pertatataka-type acanthomorphs (DPAs) are absent from the Maxi assemblage but abundant in the Weng’an biota, consistent with a late Ediacaran decline of DPAs, which may have ushered in the terminal Ediacaran decline of soft-bodied macro-organisms of the Ediacara biota during the Kotlin crisis or in the last 10 million years of the Ediacaran Period.

Monumentality as traditional ecological knowledge in the northern Maya lowlands

The emergence of monumentality in the Maya lowlands has been linked to political complexity. But how did the emergence of these monuments relate to changing human-environment interactions? Here, the author proposes that Maya monumentality embodies traditional ecological knowledge, or TEK. Taking the example of Tzacauil, the gathering of fieldstone for the preparation of land for cultivation is connected to agricultural intensification and the florescence of monumentality in the Late and Terminal Formative period (300 BC–AD 250). Exploration of the relationships between monumental traditions and localised TEK practices may illuminate the entanglement of complexity, subsistence and human-environment interactions in other parts of the world.

Four millennia of geomorphic change and human settlement in the lower Usumacinta–Grijalva River Basin, Mexico

The lower Usumacinta–Grijalva River Basin contains one of the richest biodiversity landscapes of the Maya region. Our research is based on (1) an integrative literature review of the geomorphological and archaeological papers published about the lower Usumacinta–Grijalva River Basin and (2) topographic analysis of digital elevation models using a geographical information system to explore the relationship between past human settlement and landscape accessibility along the coastal plain of Tabasco. This work provides a new synthesis of previous research and proposes new models for the geomorphic evolution of the lower Usumacinta–Grijalva River Basin in the context of four millennia of human land use and settlement. For the evolution of the strand-plain of the Usumacinta and Grijalva rivers, there are two published geochronological models that provide different chronologies. We discuss here how both geochronological models encompass Pre-Columbian human settlement in the delta. Interestingly, we notice that one of them overlaps a possible high-magnitude flood event (or events) that drove large geomorphic change around 750 CE (1200 BP), with implications for settlement patterns and chronology. Based on topographical analysis of the eastern-distal sector of the Usumacinta–Grijalva delta, we propose a new model for the evolution of this area with implications for the human occupation during the Mesoamerican Terminal Classic and Early Postclassic on the delta. As one of the main conclusions, we propose that the Pom–Atasta water bodies predate much of the Usumacinta–Grijalva delta and the most recent phase of delta building overlays the original lagoon barriers, resulting in a geomorphic setting more attractive to local human occupation after the Terminal Classic period. According to one of the geochronological models of the delta, this dates to ca. 900 CE, preceding the establishment of nearby settlements such as Atasta.

Pyrite Sulfur Isotope Systematics Suggest Low Marine Sulfate Levels across the Ediacaran–Cambrian Transition

The Ediacaran–Cambrian (E–C) transition was a critical period in Earth’s history, and it was characterized by variable but potentially significant increases in atmospheric oxygen levels (pO2). Sulfate is an essential oxidant and plays a key role in regulating Earth’s surface redox conditions. However, there is uncertainty regarding seawater sulfate levels during the E–C transition. To address this issue, organic carbon (δ13Corg) and pyrite sulfur isotope (δ34Spy) analyses of the Heyu section (the Dengying Formation) in the Sichuan Basin, South China, were carried out. The δ13Corg varies between −36.4‰ and −27.4‰, and δ34Spy ranges from −6.6‰ to 27.3‰. The TOC and pyrite content ranges from 0.13 wt.% to 4.28 wt.% and from 0.01 wt.% to 0.94 wt.%, respectively. The marine sulfate concentration was modeled using a one-dimensional diffusion–advection–reaction model (1D-DAR). The modeling results indicate that the seawater sulfate level remained at a relatively low level of ~2–6 mM. The increased pyrite burial at extensive marine anoxia during the terminal Ediacaran period was likely a driver of such a low sulfate level.

Effect of Temperature on Anaerobic Fermentation of Poplar Ethanol Wastewater: Performance and Microbial Communities.

Temperature plays an important role in anaerobic digestion (AD), and different substrates have different optimum temperatures in AD. However, the effect of temperature on the performance of AD when cellulosic ethanol wastewater was used as a substrate was rarely reported. Therefore, the digestion characteristics of cellulosic ethanol wastewater at 25, 35, 45, and 55 °C were investigated, and the microbial communities of the sludge sample were analyzed after fermentation. The results showed that the cumulative methane production was the highest at 55 °C, 906.40 ± 50.67 mL/g VS, which was 81.06, 72.42, and 13.33% higher than that at 25, 35, and 45 °C, respectively. The content of methane was 68.13, 49.26, 70.46, and 85.84% at the terminal period of fermentation at temperatures of 25, 35, 45, and 55 °C, respectively. The testing of volatile fatty acids (VFAs) indicated that the accumulation of VFAs did not occur when the fermentation was carried out at 25, 35, and 45 °C; however, the VFA content at 55 °C was much larger than that in the three groups (25, 35, and 45 °C), and the ratio of propionic acid to acetic acid was larger than 1.4 at the late stage of fermentation, so it inhibited the fermentation. The diversity of the microbial community indicated that the floral structure and metabolic pathway of fermentation were alike at 25 and 35 °C. Firmicutes and Proteobacteria were the main flora covering the 25-55 °C-based phylum or below it. The relative abundance of Methanosaeta was the highest when fermentation temperatures were 25 and 35 °C; however, its relative abundance decreased sharply and the relative abundance of Methanosarcina increased substantially when the temperature increased from 35 to 45 °C, which indicated that Methanosarcina can exist in higher temperatures. At the same time, hydrogenotrophic methanogens such as Methanoculleus and Methanothermobacter were dominant when fermentation temperatures were 45 and 55 °C, which indicated that the metabolic pathway changed from acetoclastic methanogenesis to hydrogenotrophic methanogenesis.

An 1800-year oxygen-isotope record of short- and long-term hydroclimate variability in the northern neotropics from a Jamaican marl lake

Hydroclimate variability on multi-decadal timescales has been a prominent feature of the circum-Caribbean region over the common era, with marked dry intervals noted in particular for the period 800–950 CE coinciding with the Terminal Classic Period (the so-called Terminal Classic Drought: TCD) in Mesoamerica, and with the Little Ice Age from about 1500 to 1800 CE, linked to complex ocean-atmosphere interactions. Previous compilations of palaeoclimate reconstructions have revealed a clear precipitation dipole between northern and southern Mesoamerica over the common era, which is consistent with meteorological data and modelling experiments. However, patterns of variability elsewhere within the region are less well understood, although palaeoclimate records do point to spatial complexity. Here, we present a ∼sub-decadal-scale lake-sediment hydroclimate reconstruction based on ostracod-shell stable isotopes from Wallywash Great Pond, Jamaica, covering the past ∼1800 years, which fills a spatial gap in records for the region. Variations in δ18O values at this site are a proxy for changes in effective moisture and they reveal a marked wet phase over the Terminal Classic Period (TCP), suggesting that the precipitation dipole over northern and southern Mesoamerica may have an east to west component. This is supported by some previous studies, although additional sites are required from strategic localities within the region to confirm this. The Little Ice Age interval at Wallywash is drier than the TCP, although the signal is less clear than at some sites within the wider region, suggesting that regional complexity in hydroclimate has characterised this interval as well.

Pathomorphological characteristics of sequelae of the black mamba bite

Pathomorphological changes in internal organs due to the toxic effects of the black mamba venom are nonspecific in nature and presume its neurotoxic and cardiotoxic effects with the development of the DIC syndrome, pulmonary edema, and brain edema in the terminal period. In forensic medicine, the development of specific diagnostic criteria, as well as an algorithm for detecting toxins of the black mamba venom in biological fluids and tissues of internal organs can become a promising topic for scientific research.

CHANGING SPHERES OF INTERACTION IN TERMINAL CLASSIC WESTERN BELIZE

Archaeological investigations in western Belize have recorded a growing body of evidence that is indicative of non-central lowland Maya influences in this Maya sub-region during the Terminal Classic period. Evidence for Yucatec and non-Maya influence in the Belize River Valley is manifested by the presence of new architectural styles and programs, and by the introduction of “foreign” artifacts and ideologically charged symbols. These cultural changes represent a departure from the previous Late Classic cultural tradition which reflects closer ties with central Peten sites. Besides providing evidence for Yucatecan style architecture and artifacts in western Belize, we suggest that these non-local traits were likely associated with the waning influence of Peten sites during a period of economic and political decline in the central Maya lowlands, and with the concurrent rise of Terminal Classic polities in the northern lowlands of the Yucatan Peninsula and the Gulf Coast of Mexico.

SEA-LEVEL RISE AND SETTLEMENT AT EK WAY NAL: CORING THE PAST

Excavations in the spring and summer of 2022 were carried out at the underwater ancient Maya salt work of Ek Way Nal in Punta Ycacos Lagoon, Paynes Creek National Park, Belize. Ek Way Nal provided salt to the ancient Maya during the Late and Terminal Classic periods (600-900 C.E.). In additional to excavations in buildings at the site, a 1 X 2 m unit was excavated to extract a sediment column for examining the relationship between the ancient Maya settlement at Ek Way Nal and sea-level rise. In this article, the excavations, extraction of the sediment column, and processing it for laboratory analyses are described. Field observations are discussed. Fine red mangrove root (Rhizophora mangle) and charcoal samples were extracted from the sediment column for radiocarbon dating. The results from the datum core excavation indicate that sea-level rise occurred before, during, and after the ancient Maya occupation at Ek Way Nal.

Cardiovascular safety pharmacology of ivermectin assessed using the isoflurane-anesthetized beagle dogs: ICH S7B follow-up study.

Antiparasitic ivermectin has been reported to induce cardiovascular adverse events, including orthostatic hypotension, tachycardia and cardiopulmonary arrest, of which the underlying pathophysiology remains unknown. Since its drug repurposing as an antiviral agent is underway at higher doses than those for antiparasitic, we evaluated the cardiovascular safety pharmacology of ivermectin using isoflurane-anesthetized beagle dogs (n=4). Ivermectin in doses of 0.1 followed by 1 mg/kg was intravenously infused over 10 min with an interval of 20 min, attaining peak plasma concentrations of 0.94 ± 0.04 and 8.82 ± 1.25 μg/mL, which were 29-31 and 276-288 times higher than those observed after its antiparasitic oral dose of 12 mg/body, respectively. The latter peak concentration was > 2 times greater than those inhibiting proliferation of dengue virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and hepatitis B virus in vitro. Ivermectin decreased heart rate without altering mean blood pressure, suggesting that ivermectin does not cause hypotension or tachycardia directly. Ivermectin hardly altered atrioventricular nodal or intraventricular conduction, indicating a lack of inhibitory action on Ca2+ or Na+ channel in vivo. Ivermectin prolonged QT interval/QTcV in a dose-related manner and tended to slow the repolarization speed in a reverse frequency-dependent manner, supporting previously described its IKr inhibition, which would explain Tpeak-Tend prolongation and heart-rate reduction in this study. Meanwhile, ivermectin did not significantly prolong J-Tpeakc or terminal repolarization period, indicating torsadogenic potential of ivermectin leading to the onset of cardiopulmonary arrest would be small. Thus, ivermectin has a broad range of cardiovascular safety profiles, which will help facilitate its drug repurposing.

TRANSFORMATION, GROWTH, AND GOVERNANCE AT CARACOL, BELIZE

Around 650 CE the city of Caracol was one of the largest cities in the world. However, it did not begin as a large city. Instead Ux Witz Ha’ (“three stone place” – the city’s hieroglyphic name) came into being from the conurbation of three separate centers. Three architectural complexes formed the initial districts of the larger city – Downtown Caracol, Hatzcap Ceel, and Cahal Pichik – between the Preclassic and Early Classic Periods. This unification resulted in a path-dependent urban form with future growth focused on multiple monumental nodes and a dendritic causeway system. Settlement growth relied on the incorporation or construction of public plazas and monumental architecture to provide urban infrastructure and administrative cohesion over the landscape. What follows is a preliminary temporal sequence for the districts, tracing the growth of the city from the Preclassic to the Terminal Classic Periods. By combining lidar, archaeology, and hieroglyphic data a broader interpretation of governance within the city can be elucidated. Over time, Caracol shifted back and forth between more collective and more autocratic governance systems until the political, economic, and demographic collapse of the city around 900 CE.

CHALLENGES IN BUILDING ARCHAEOLOGICAL CHRONOLOGIES IN THE STANN CREEK DISTRICT

Key to archaeological research is our ability to recognize and define material-culture patterns and organize such patterns in time and space. Since 2014, the Stann Creek Regional Archaeology Project (SCRAP) has focused on understanding processes of settlement development and growth at the Ancestral Maya town of Alabama in East-Central Belize, constructed and occupied primarily during the transition period between the late facet of the Late Classic to Terminal Classic periods. While we may never know precisely who settled Alabama and why, we aim to answer questions about the where, when, and how of its development in our ongoing research. In following these lines of inquiry, we have had to grapple with several obstacles that have frustrated standard practices of building archaeological chronologies at the site. Such barriers include earthen-core architecture with minimal artifact refuse within platform cores. Additionally, local and regional soil conditions that result in a poorly preserved and highly fragmentary ceramic assemblage and no preservation of human or faunal remains to date. Finally, we face the difficulties of constraining the radiocarbon calibration curve during the primary period of Alabama’s settlement and growth. This paper details these problems and outlines our various approaches in their confrontation.

Hemşirelik Öğrencileri Terminal Dönemindeki Çocuk Hastanın Bakımı Hakkında Ne Düşünüyor? Odak Grup Çalışması

Aim: Nursing students face many patients who require palliative care in the terminal period. This study aims to determine the student nurses' experiences with the palliative care provided to children in the terminal period.
 Method: The study was conducted using focus group interviews, which are qualitative research methods. The sample was constituted of 12 intern student nurses who were working in the pediatric hospital of the university in 2017 in Turkey. The research inclusion criteria for students were that they must have provided palliative care or seen death. The focus group interview was held in the meeting room at the Nursing School on the day and hour when the nurses were available with four researchers. Data were analyzed together by using conventional content analysis.
 Results: Three main themes were determined (Preparing for death, self-care, and meeting the demands of the child and the family). It was found that nursing students providing care to pediatric patients in the terminal period experience many feelings including fear, nervousness, helplessness, shock, emotional deterioration, etc. and they do not know how to deal with these emotions. These students believe that symptom management and self-care requirements should be managed in the best way and that emotional support should be provided. The students pointed out the families' information needs and emotional support needs. They also emphasized the emotional effects associated with themself. 
 Conclusions and Suggestions: Educational programs related to care for the child in the terminal period and preparation for death should be added to the nursing education and training process. Organize individual and group meetings to provide nursing students opportunities to express their feelings regarding the care and death of the child in the terminal period.

Maya molded-carved ceramics as boundary objects: Terminal classic ceramic production and the forging of political relations in the mopan valley of Guatemala

• Terminal Classic period Mopan Valley potters produced a range of decorated serving vessels including ‘Ahk’ utu’ Molded-carved, Portia Molded-carved, and Local Fine Orange ceramics. • In addition to producing their own ceramics, inhabitants of the middle Mopan Valley sites of Ucanal, La Blanca, and Calzada Mopan had access to ceramics produced in or close to the Upper Belize Valley, the Holmul River, and the Usumacinta River region, underscoring their diverse social and political relationships throughout the Southern Maya Lowlands. • Microphotography and portable X-ray fluorescence (pXRF) analyses of ceramic pastes complement visual typology studies to provide a more holistic perspective of archaeological ceramics that can address both different and overlapping pottery communities of practice. • We find that Terminal Classic polities often shared in an overlapping network of ceramic production and gift exchange that bridged different political communities, a pattern that contrasted with the most elaborate polychrome ceramic traditions of the earlier Late Classic period, which were more highly controlled and circumscribed in nature. Fine Orange ceramics, speciality serving wares of the Terminal Classic (ca. A.D. 810–950/1000) in the Maya area, have long been implicated in the identification of changing political and social relationships. Some previously subordinate political centers thrived during this time as many of the dominant Classic polities were embroiled in crises and reductions in their populations. This paper examines molded-carved Fine Orange and “imitation” Fine Orange ceramics from a trio of closely-located sites that prospered during the Terminal Classic period: Ucanal, La Blanca, and Calzada Mopan in the middle Mopan Valley in Petén, Guatemala. Chemical paste analyses using a portable X-ray fluorescence instrument, microphotography, and traditional Ware-Type-Variety analyses reveal that potters in this region did not blindly imitate Fine Orange ceramics, but picked and chose techniques and designs that drew from multiple communities of practice. Furthermore, these sites had access to decorative serving vessels that were produced in multiple regions throughout the Southern Maya Lowlands, placing them at an important nexus of political, economic, and social interaction. We argue that molded-carved and other decorated ceramics served as boundary objects, which articulated different pottery producing communities and forged marriage and political ties between different polities in a new decentralized political landscape.

Fraxetin suppresses the proliferation, migration, and invasion of ovarian cancer cells by inhibiting the TLR4/STAT3 signaling pathway

Background Little therapeutic effect can be exerted on malignant ovarian cancer at the terminal period. Traditional Chinese medicine (TCM) has been a potential way for the treatment of various diseases. In this research, we probed into the potential curative effect of Fraxetin (FXT), a TCM monomer, on ovarian cancer. Methods Ovarian cancer cells were treated with FXT at different concentrations for 12 h, or pretreated by 0.5 μM of colivelin, a STAT3 activator, for 1 h and then treated with 80 μM of FXT for 12 h. The viability of ovarian cancer cells was measured by MTT assay, and the cell colony number was counted after colony formation assay. Transwell assay was conducted for investigating the relationship between the FXT at different concentrations and the invasion as well as migration rates of ovarian cancer cells. The expressions of epithelial-to-mesenchymal transition (EMT)-associated markers and TLR4/STAT3 signaling pathway-related proteins in ovarian cancer cells after the treatment of FXT were measured by western blot. Results FXT inhibited the viability, invasion, migration, and proliferation of SKOV3 and SW626 cells and suppressed EMT, but colivelin reversed the impacts of FXT. FXT also suppressed the expressions of N-cadherin, snail, vimentin, TLR4, phosphorylated (P)-STAT3, cyclin D1, and C-myc, whilst promoting that of E-cadherin by inhibiting the activation of TLR4/STAT3 signaling pathway. Conclusion FXT exerts a therapeutic effect on ovarian cancer by repressing the TLR4/STAT3 signaling pathway. With the accumulating concentrations of FXT, the therapeutic effect becomes more and more obvious.

Climatic origin of provenances of Corymbia calophylla affects canker disease susceptibility, caused by Quambalaria coyrecup, and interactions with drought stress

AbstractMany forest ecosystems are in decline around the world due to increasing biotic and abiotic stresses. Marri (Corymbia calophylla) is an endemic and common eucalypt species of southwestern Australia, which is in decline primarily due to stem canker caused by the pathogenic fungus Quambalaria coyrecup. This study determined to what extent disease susceptibility and plant growth were associated with climate at origin for eight provenances of marri. Plants of all provenances were grown in a common garden with or without pathogen inoculation. Disease development and physiological performance of plants were monitored during an initial irrigated and subsequent terminal drought period. Provenances from drier regions were more susceptible to the fungal pathogen than those from wetter regions, having on average 31% higher incidence rates at 20 days post‐inoculation (dpi) and larger canker lesions at 130 dpi (on average 49% increase) and 230 dpi (on average 42% increase). However, canker development for each provenance was fastest during the initial irrigated wetter growing period. Overall, the average relative canker growth rate was 4‐fold higher during the irrigated period compared to the terminal drought period (p < .001). There were no significant differences between the provenances in leaf water status, photosynthetic rates, or relative growth rates (p > .05). Canker infection reduced both photosynthetic rates and growth rates but only during the later part of the terminal drought period, with significant (p < .05) reductions observed in two out of eight provenances, when plants had relatively large canker sizes. This effect tended to be strongest in the provenances from drier regions as they had relatively larger canker sizes than the provenances from wetter regions. We propose that the increased susceptibility of drier provenances is related to their lower exposure to the pathogen in their drier habitats. Since this is potentially due to suboptimal defence responses, using provenances from drier locations to ‘future‐proof’ local restoration outcomes in a drying climate may be counterproductive due to plant–pathogen interactions.