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Abstract Southern California experienced unprecedented megadrought between 2012 and 2018. During this time,Malosma laurina, a chaparral species normally resilient to single‐year intense drought, developed extensive mortality exceeding 60% throughout low‐elevation coastal populations of the Santa Monica Mountains. We assessed the physiological mechanisms by which the advent of megadrought predisposedM. laurinato extensive shoot dieback and whole‐plant death. We found that hydraulic conductance of stem xylem (Ks, native) was reduced seven to 11‐fold in dieback adult and resprout branches, respectively. Staining of stem xylem vessels revealed that dieback plants experienced 68% solid‐blockage, explaining the reduction in water transport. Following Koch's postulates, persistent isolation of a microorganism in stem xylem of dieback plants but not healthy controls indicated that the causative agent of xylem blockage was an opportunistic endophytic fungus,Botryosphaeria dothidea. We inoculated healthyM. laurinasaplings with fungal isolates and compared hyphal elongation rates under well‐watered, water‐deficit, and carbon‐deficit treatments. Relative to controls, we found that both water deficit and carbon‐deficit increased hyphal extension rates and the incidence of shoot dieback.more » « less
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Abstract Ticks are vectors of many diseases and are expanding in geographic distribution. However, how ticks will fare in their new environments, where they may experience stressful climatic conditions at the expansion front, remains unclear. Since there is a trade‐off in ticks between behaviors that promote longevity and behaviors that promote reproduction, we hypothesized that extreme climatic stress reduces the survivorship of ticks but increases the frequency of tick host‐seeking behavior, or questing. Here, we used a novel method to simulate climatic stress on individual ticks of three species—Amblyomma americanum,Dermacentor variabilis, andIxodes scapularis—to evaluate their survival, physiology, and questing behavior. The first experiment involved placing 144 adult ticks of each species in two temperature ranges (15–25°C and 25–35°C) and three relative humidity (RH) treatments (32%, 58%, and 84% RH). We assessed the ticks daily for survivorship and questing, and we measured water loss by comparing the mass of each tick when it died to when it was fully hydrated. In this first experiment, ticks in warmer and less humid conditions generally died faster than those in cooler and more humid conditions. Ticks of all three species were more likely to quest shortly before their death and consistently died after losing approximately 50%–56% of their total body water content, butIxodesreached that threshold much faster than the other two species. The second experiment involved placing 18 ticks of each species at 35°C and 32% RH. We assessed the ticks every 3 h for survivorship, questing, and water loss. Ticks again were more likely to quest shortly before their death. With frequent checks, we were able to measure the dehydration tolerance more accurately and the rate of water loss. Ticks of all three species consistently died after losing approximately 51% of their total body water content. However,Ixodeslost water approximately 5 times faster thanAmblyommaand 11 times faster thanDermacentor. These results demonstrate that severe climatic stress tilts the trade‐off toward higher questing rates but not higher overall questing time because of reduced survival rates.more » « less
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Macroalgae form important coastal ecosystems and are considered to be highly productive, yet individual macrophyte carbon uptake rates are poorly documented and methodologies forin situassessments of productivity are not well developed. In this study, we employ a13C enrichment method in benthic chambers to calculate carbon uptake rates and assessδ13C signatures of a large stock of nearshore benthic macroalgae varying in taxa and morphology in Southern California. Our objectives are to 1) identify the variability of carbon uptake and inorganic carbon use among individuals of the same species or morphology, and 2) establish accurate and accessible carbon uptake procedures for coastal benthic primary producers. We found no significant relationship between the observed ranges of environmental factors such as nutrient concentrations, PAR, temperature, conductivity, and productivity rates, suggesting that unique physiological complexions underpin the high variability of carbon uptake andδ13C in studied macrophyte samples. We consider three reasons our experimental carbon uptake rates are 3–4 orders of magnitude lower than existing literature, which reports carbon uptake in the same units despite using different methods: 1) underrepresentation ofPmax, 2) incomplete carbon fractionation corrections, and 3) reduced hydrodynamics within the benthic chambers.more » « less
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Marine protected areas (MPAs) aim to protect habitats and ecosystems to promote the diversity and health of marine populations. To evaluate the health of fish populations within and outside of MPAs in Southern California, we used flight initiation distance (FID). FID is the distance at which an individual will flee from a perceived predator and is a direct measure of boldness. Lower FIDs are indicative of bolder populations. Lower FID values indicate that fish will have the opportunity to dedicate less energy to fleeing from predators which could then be used for increased foraging. Data was collected from eight locations along the Southern California coast, four in protected areas and four in non-protected areas. FIDs were measured with a sonar-based range finder. All fish species that recreational fishermen could catch were targeted, with a focus on six core species spearfishermen catch commonly. Results showed that all fish sampled in MPAs have significantly lower FIDs than those in non-protected areas. An ANOVA showed no significant difference between different locations of the same protected status. The six core species had lower average FIDs in protected areas, three species had significant differences between protected and non-protected populations, and there was no significant difference in FIDs between species. These results show that Southern California MPAs are promoting healthier fish communities with respect to boldness behavior. This data and methods can be implemented in future projects to expand the range of metrics measured to inform management tools for California’s MPAs and MPAs at large.more » « less
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The mammary microbiome is a newly characterized bacterial niche that might offer biological insight into the development of breast cancer. Together with in-depth analysis of the gut microbiome in breast cancer, current evidence using next-generation sequencing and metabolic profiling suggests compositional and functional shifts in microbial consortia are associated with breast cancer. In this review, we discuss the fundamental studies that have progressed this important area of research, focusing on the roles of both the mammary tissue microbiome and the gut microbiome. From the literature, we identified the following major conclusions, (I) There are unique breast and gut microbial signatures (both compositional and functional) that are associated with breast cancer, (II) breast and gut microbiome compositional and breast functional dysbiosis represent potential early events of breast tumor development, (III) specific breast and gut microbes confer host immune responses that can combat breast tumor development and progression, and (IV) chemotherapies alter the microbiome and thus maintenance of a eubiotic microbiome may be key in breast cancer treatment. As the field expectantly advances, it is necessary for the role of the microbiome to continue to be elucidated using multi-omic approaches and translational animal models in order to improve predictive, preventive, and therapeutic strategies for breast cancer.more » « less
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Stevenson, Brian (Ed.)Ticks are the most important vectors of zoonotic disease-causing pathogens in North America and Europe. Many tick species are expanding their geographic range. Although correlational evidence suggests that climate change is driving the range expansion of ticks, experimental evidence is necessary to develop a mechanistic understanding of ticks’ response to a range of climatic conditions. Previous experiments used simulated microclimates, but these protocols require hazardous salts or expensive laboratory equipment to manipulate humidity. We developed a novel, safe, stable, convenient, and economical method to isolate individual ticks and manipulate their microclimates. The protocol involves placing individual ticks in plastic tubes, and placing six tubes along with a commercial two-way humidity control pack in an airtight container. We successfully used this method to investigate how humidity affects survival and host-seeking (questing) behavior of three tick species: the lone star tick ( Amblyomma americanum ), American dog tick ( Dermacentor variabilis ), and black-legged tick ( Ixodes scapularis ). We placed 72 adult females of each species individually into plastic tubes and separated them into three experimental relative humidity (RH) treatments representing distinct climates: 32% RH, 58% RH, and 84% RH. We assessed the survival and questing behavior of each tick for 30 days. In all three species, survivorship significantly declined in drier conditions. Questing height was negatively associated with RH in Amblyomma , positively associated with RH in Dermacentor , and not associated with RH in Ixodes . The frequency of questing behavior increased significantly with drier conditions for Dermacentor but not for Amblyomma or Ixodes . This report demonstrates an effective method for assessing the viability and host-seeking behavior of tick vectors of zoonotic diseases under different climatic conditions.more » « less
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Gibbons, Sean M. (Ed.)ABSTRACT Microbiota studies have reported changes in the microbial composition of the breast upon cancer development. However, results are inconsistent and limited to the later phases of cancer development (after diagnosis). We analyzed and compared the resident bacterial taxa of histologically normal breast tissue (healthy, H, n = 49) with those of tissues donated prior to (prediagnostic, PD, n = 15) and after (adjacent normal, AN, n = 49, and tumor, T, n = 46) breast cancer diagnosis ( n total = 159). DNA was isolated from tissue samples and submitted for Illumina MiSeq paired-end sequencing of the V3-V4 region of the 16S gene. To infer bacterial function in breast cancer, we predicted the functional bacteriome from the 16S sequencing data using PICRUSt2. Bacterial compositional analysis revealed an intermediary taxonomic signature in the PD tissue relative to that of the H tissue, represented by shifts in Bacillaceae , Burkholderiaceae , Corynebacteriaceae , Streptococcaceae , and Staphylococcaceae . This compositional signature was enhanced in the AN and T tissues. We also identified significant metabolic reprogramming of the microbiota of the PD, AN, and T tissue compared with the H tissue. Further, preliminary correlation analysis between host transcriptome profiling and microbial taxa and genes in H and PD tissues identified altered associations between the human host and mammary microbiota in PD tissue compared with H tissue. These findings suggest that compositional shifts in bacterial abundance and metabolic reprogramming of the breast tissue microbiota are early events in breast cancer development that are potentially linked with cancer susceptibility. IMPORTANCE The goal of this study was to determine the role of resident breast tissue bacteria in breast cancer development. We analyzed breast tissue bacteria in healthy breast tissue and breast tissue donated prior to (precancerous) and after (postcancerous) breast cancer diagnosis. Compared to healthy tissue, the precancerous and postcancerous breast tissues demonstrated differences in the amounts of breast tissue bacteria. In addition, breast tissue bacteria exhibit different functions in pre-cancerous and post-cancerous breast tissues relative to healthy tissue. These differences in function are further emphasized by altered associations of the breast tissue bacteria with gene expression in the human host prior to cancer development. Collectively, these analyses identified shifts in bacterial abundance and metabolic function (dysbiosis) prior to breast tumor diagnosis. This dysbiosis may serve as a therapeutic target in breast cancer prevention.more » « less