Genetic differences between early and late forms of Alaskan chinook salmon (Oncorhynchus tshawytscha) were identified using two genetic approaches: mitochondrial DNA (mtDNA) analysis and protein electrophoresis. The study populations consisted of early- and late-run chinook salmon in each of the Kenai and Kasilof rivers in Alaska, and a single population from the Minam River, Oregon, that provided a relative scale for the differences among the Alaskan populations. Two segments of mtDNA were amplified separately using the polymerase chain reaction (PCR) and then digested with 14 to 16 restriction enzymes. Results showed that the two early runs were genetically similar to each other but different from either of the late runs. The late runs were different from each other based on the frequency of the common haplotypes. The Minam River stock shared two haplotypes with the Alaskan stocks and displayed one unique haplotype. The frequency difference in the shared haplotypes together with the presence of a unique haplotype allowed us to separate the Oregon population from those in Alaska. In the protein analysis, each of the five populations was examined at 30 allozyme loci to determine variation within and between the runs. Based on 14 polymorphic loci, Minam River chinook salmon were genetically distinct from the Alaskan populations. Within the Alaskan populations, the two early runs were most similar to each other but different from the two late runs; the two late runs were also genetically most similar to each other. Based on all loci, protein electrophoresis proved to be a useful technique to separate stocks of chinook salmon. On a locus by locus basis, however, mtDNA was more powerful. Both mtDNA and allozyme analysis suggest that chinook salmon may segregate into genetically different early and late forms within a drainage. / Graduation date: 1995

The hydraulic conductance of a plant is a significant factor in determining the / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2008.

Future changes to the pH and temperature of the oceans are predicted to impact the biodiversity of marine ecosystems, particularly those animals that rely on the process of calcification. The marine intertidal gastropod Littorina littorea can be used as a model of intertidal organism for investigating the effects of ocean acidification and high temperature, alone and in combination because its ability to be quickly adapt against environmental stressor. In the first study a single species population of L. littorea was used to test for physiological and biochemical effects underpinning organismal responses to climate change and ocean acidification. Compared with control conditions, snails decreased metabolic rates by 31% in response to elevated pCO2 while by 15% in response to combined pCO2 and temperature. Decreased metabolic rates were associated with metabolic depression, a strategy to match oxygen demand and availability, and an increase in end-product metabolites in the tissue under acidified treatments, indicating an increased reliance on anaerobic metabolism. This study also showed that anthropogenic alteration of CO2 and temperature may also lead to plastic responses, a fundamental mechanism of many marine gastropods to cope environmental variability. At low pH and elevated temperature in isolation or combined showing lower shell growth than individuals kept under control conditions. Percentage change in shell length and thicknesses was also lower under acidified and temperature in isolation or combined than control condition, making shells were more globular and desiccation rates were higher. Further studies to broader latitudinal ranges for six populations of L. littorea showed that shell growth decreased in all six populations under elevated pCO2 compared to control snails particularly those at range edges. Elevated pCO2 also affected to the reduction of shell length and width that causing shell aspect ratio to increase across latitudinal gradients except individuals from Millport, UK. Percentage changes of aperture width and aperture area were also decrease under elevated pCO2 with greater reduction of aperture area were found at populations in the mid-ranges which is assumed this response might be linked to local adaptation of the individual to microclimatic conditions. This study also showed that metabolic rates were negatively affected by high pCO2 and show non-linear trend across latitudinal gradients in compared to individual kept under normal pCO2 conditions. Metabolomic analysis showed that two northern populations of Trondheim and TromsØ were distinct from other populations when exposed to low temperature (15 °C) with elevated pCO2 due to, in part, high concentrations of thymine, uracil, valine and lysine. A similar separation also occurred under medium (25 °C) and high (35 °C) temperature exposure in which one of northern population (Trondheim) was distinct from other populations and had lower concentrations of alanine, betaine and taurine while higher of valine. These results suggest that populations at northern latitudes may apply different ionic transport mechanisms under elevated pCO2 and elevated temperatures and those populations are likely to vary in terms of their physiological responses to this environmental challenge.

Processos fisiológicos que modulam a aclimatação fotossintética e o crescimento de plantas ao aumento da concentração de CO2 atmosférico são desconhecidos para a maioria das espécies da região amazônica. Neste sentido, este estudo buscou compreender o comportamento fotossintético e a alocação de carbono em Senna reticulata. Esta espécie ocorre em regiões amazônicas que passam por períodos de seca e alagamento e como estratégia de estabelecimento possui crescimento rápido e alta capacidade fotossintética. O objetivo deste estudo foi comparar os parâmetros de trocas gasosas e de crescimento de plantas cultivadas em câmaras de topo aberto sob diferentes concentrações de CO2 (380ppm-ambiente e 760ppm-elevado). Foram realizadas 6 coletas a cada 15 dias, nas quais foram mensurados pontos relativos as curvas AxPAR e AxCi, calculando-se os parâmetros fotossintéticos de cada curva. Os parâmetros de crescimento foram medidos em coletas destrutivas (biomassa) e não destrutivas (área foliar, altura e nº de folhas). As plantas do tratamento elevado apresentaram maior assimilação fotossintética aos 30 e 45 dias de experimento. Após este período foi observada uma mudança no padrão de alocação (de folha para raízes) e as plantas do elevado apresentaram aclimatação na fotossíntese. A aclimatação foi caracterizada primeiramente por uma redução na velocidade de carboxilação da Rubisco, que foi concomitante com a redução na concentração de N e C foliar. A partir disso ocorreu aumento na senescência das folhas, redução na área foliar e redução na concentração de clorofilas. Somente aos 90 dias é que houve um aumento de 30% na biomassa total das plantas submetidas ao tratamento elevado, resultante do aumento de massa principalmente das raízes e folhas. A transpiração e a respiração das plantas do elevado tenderam a ser menores ao longo de todo o tempo, sendo esta diferença significativa apenas aos 75 dias. Apesar das folhas possuírem menor área foliar e número de folhas, foi observado pela análise de massa especifica das folhas que as plantas do tratamento elevado possuem maior massa em relação às do ambiente, possivelmente pelo maior acúmulo de amido. A eficiência no uso da água foi maior nas plantas do elevado aos 30, 75 e 90 dias. A partir desses dados é possível concluir que S. reticulata submetida ao dobro da concentração atual de CO2, desenvolve processos de aclimatação fotossintética sob longa exposição ao elevado CO2, porém consegue produzir mais biomassa. / Physiological processes that modulate growth and photosynthetic acclimation of plants to increased atmospheric CO2 concentration are unknown for most species in the Amazon region. This study aimed to understand the photosynthesis and carbon allocation in Senna reticulata. This species occurs in the Amazonian regions that experience periods of drought and flooding and it has a fast growth and a high photosynthetic capacity as a strategy for its establishment. S. reticulata plants were grown in open top chambers under different concentrations of CO2 (380ppm Ambient - 760ppm Elevated) and their gas exchange and growth were compared. The harvests were performed at 15, 30, 45, 60, 75 and 90 days of experiment. At each date, AxPAR and AxCi curves were carried out to calculate the photosynthetic parameters. Growth parameters included biomass, leaf area, height and number of leaves. The plants of elevated CO2 presented higher photosynthetic assimilation at 30 and 45 days of experiment. After this period was observed a change in the carbon allocation (e.g. root to leaf) and the plants at elevated CO2 demonstrated a photosynthetic acclimation. This acclimation was characterized primarily by a reduction in velocity of carboxylation of Rubisco, which was concomitant with the reduction in N and C concentration in leaves. Also, the plants at elevated CO2 showed an increase in leaf senescence and a reduction in leaf area and chlorophyll concentration. After 90 days there was an increase (i.e. 30%) in total biomass of plants growing under elevated CO2, due to increase of roots and leaves biomass. The transpiration and respiration rates of plants at elevated CO2 tended to be lower throughout the experiment and the significant difference was found at 75 days. Although the leaves have less leaf area and leaf number, it was observed that specific leaf area from elevated CO2 treatment showed higher biomass when compared to ambient CO2. That difference possibly occurred due to greater starch accumulation. The water use efficiency was greater in plants from the elevated CO2 at 30, 75 and 90 days. From these data we conclude that S. reticulata grown at the elevated CO2 produces more biomass despite occurs the photosynthetic acclimation under long exposure to high CO2.

Acharadria crocea é um hidrozoário comum do Atlântico Sul-Ocidental. Na costa brasileira, a espécie possui um padrão de sazonalidade bem definido, sendo abundante nos meses frios do ano e ausente ou rara no verão e outono. Durante o inverno, a espécie apresenta intenso crescimento assexuado por brotamento, permitindo o rápido desenvolvimento da colônia. Esta se torna fértil em um curto espaço de tempo e produz uma grande quantidade de larvas, o que favorece o estabelecimento de novas colônias. Além destas características, a espécie já foi associada com transporte antrópico, por meio de incrustação em cascos de navios, o que a torna uma espécie potencialmente invasora. Este trabalho avaliou experimentalmente a tolerância ecofisiológica das larvas de A. crocea a temperatura e salinidade da água, bem como sua capacidade de colonização de diferentes substratos, tanto naturais (carapaças de cracas e mexilhões) como artificiais (fragmentos de PET e alumínio). A influência de um biofilme multiespecífico de bactérias no assentamento da espécie também foi analisada. Com base nos dados de tolerância ecofisiológica das larvas, foi realizada e modelagem de nicho da espécie utilizando GLM (Modelos Lineares Generalizados), que gerou mapas de sua distribuição potencial. Utilizando dados de ocorrência geográfica disponíveis na literatura, foram gerados também mapas de distribuição potencial das colônias adultas utilizando o algoritmo MAXENT. Para integrar as informações das fases bentônica e planctônica de A. crocea, foi realizada subsequentemente a intersecção dos mapas gerados por ambas as metodologias, gerando assim uma predição unificada de sua ocorrência. / Acharadria crocea is a common South-occidental Atlantic hydrozoan. On the Brazilian coast it presents a well defined seasonality pattern, being abundant on the cool months of the year and absent or rare on summer and autumn. During winter, the specie increases its numbers by asexual stolonal growth, as well as the colony size. The colony becomes fertile and produces a great amount of larvae, allowing the establishment of new colonies. Besides these characteristics, A. crocea was already found colonizing ship hulls, being considered a highly invasive species. This report experimentally evaluated the ecophysiological tolerance of A. crocea larvae to water temperature and salinity, as well as its ability to colonize different substrates, both natural (mussel and barnacle shells) and artificial (plastic bottles and aluminum). The influence of a bacterial film on its adaptation was also analyzed. Based on the ecophysiology of the larvae, an ecological niche modeling was built using GLM (generalized linear models) to create maps of the distribution of the larvae. Using literature based graphic occurrence data and the MAXENT algorithm, maps of the adult colonies potential distribution were also created. To relate information of benthonic and planctonic phases of A. crocea, an intersection of the maps was built from both methods.

A castanheira (Bertholletia excelsa Humb. & Bonpl.) é uma árvore nativa da região Amazônica muito valorizada por suas sementes, as castanhas-do-Brasil, que apresentam alto valor nutritivo e são uma rica fonte de selênio, um agente antioxidante. O Brasil está entre os países que mais produzem e exportam estas castanhas. As condições climáticas da região Amazônica, assim como as demais etapas da cadeia produtiva, podem favorecer a infecção fúngica neste substrato, principalmente por Aspergillus nomius, espécie extremamente relacionadas à produção de aflatoxinas. Esta micotoxina está associada ao desenvolvimento de tumores, imunossupressão e alterações hepáticas tornando-a um risco para a saúde pública. Sendo assim, a realização de estudos que forneçam informações adequadas sobre o comportamento de A. nomius é de extrema relevância, pois contribuem no conhecimento das condições propícias para a produção de aflatoxinas. Neste contexto, o objetivo deste estudo foi avaliar a resposta ecofisiológica de cepas de A. nomius isoladas de castanhas-do-Brasil (crescimento micelial, expressão gênica e produção de aflatoxinas) em diferentes temperaturas (25, 30 e 35 °C). O crescimento micelial foi mensurado diariamente a partir da inoculação de 8 cepas em ágar coco, mantidas no escuro até 7 dias. A partir destas colônias foi feita análise da expressão dos genes aflR, aflD e aflQ, envolvidos na biossíntese das aflatoxinas, com utilização de PCR em Tempo Real. Com as mesmas colônias também foi feita análise do potencial aflatoxigênico (B1, B2, G1 e G2) qualitativo (Cromatografia em Camada Delgada) e quantitativo (Cromatografia Líquida de Alta Eficiência). A temperatura ideal para crescimento micelial das cepas de A. nomius foi 30 °C. Esta condição foi a melhor para a expressão dos genes aflR, aflD e aflQ. Contudo, o gene aflQ também apresentou alta expressão a 25 °C e foi o gene mais expresso em todas as temperaturas avaliadas. Em relação ao potencial toxigênico das cepas, a maior produção ocorreu a 25 °C. Em todas as temperaturas avaliadas houve maior produção de aflatoxinas do grupo B do que do grupo G. Pôde-se observar que a temperatura que propiciou a maior produção destas toxinas coincide com as da região Amazônica, território nativo das castanheiras. Com base nos resultados reportados, este estudo poderá servir como ferramenta na elaboração de eficientes estratégias para o controle de A. nomius e aflatoxinas em castanhas-doBrasil. / The Brazil nut tree (Bertholletia excelsa Humb. & Bonpl.) is an Amazonian native species that produce seeds with high nutritional value and rich source of selenium, an antioxidant agent. Brazil is one of the major producers and exporters of these nuts. The Amazon weather conditions in the production area and also on the productive chain play a critical role in the fungal infection, specially by Aspergillus nomius, important species associated to the aflatoxin contamination. This mycotoxin is related to the development of tumors, immunosuppression and liver alterations that becomes a risk to public health. Therefore, studies that provides adequate informations about the behavior of A. nomius are extremely relevant, contributing to better understand the favorable conditions to the aflatoxins production. The main goal of the present study was to evaluate the ecophysiological response of A. nomius strains isolated from Brazil nuts (mycelial growth, gene expression and aflatoxin production) at different temperatures (25 °C, 30 °C, and 35 °C). The mycelial growth of 8 strains was measured daily for 7 days in coconut agar. From these colonies, the expression of aflR, aflD, and aflQ genes, that are involved in aflatoxin biosynthesis was analyzed by using Real Time PCR. From the same colonies, the aflatoxigenic potential (B1, B2 , G1 and G2 ) were analyzed qualitative and quantitative by Thin Layer Chromatography and High Performance Liquid Chromatography, respectively. Mycelial growth assessment revealed that the optimal temperature for the radial growth rate and the average of final growth was at 30 °C. This was also the best condition for the expression of aflR, aflD, and aflQ genes. However, the aflQ also showed high expression at 25 °C and was the most expressed gene at all evaluated temperatures. The highest aflatoxin production occurred at 25 °C, with higher toxins production on group B than group G. It was possible to notice that the optimum temperature to aflatoxin production coincides with those in Amazon region, the most important producing area. These results also may contribute to enhance the management strategies of aflatroxin control in Brazil nuts.

Plant interactions (e.g., competition, facilitation) are critical drivers in community development and structure. The Stress Gradient Hypothesis (SGH) provides a predictive framework for how plant species interactions vary inversely across an environmental stress gradient, predicting that facilitation is stronger with increasing levels of stress. The SGH has been supported in numerous ecosystems and across a variety of stress gradients, but recent research has demonstrated contradictory results. These discrepancies have led to SGH revisions that expand its conceptual framework by incorporating additional factors, such as other stressor types and variations in species life history strategies. In this dissertation, I examine a further modification of the SGH by proposing and testing a Multiple Stress Gradient Hypothesis (MSGH) that considers how plant interactions vary along a continuous gradient of two co-occurring stressors using mangrove and salt marsh communities as a case study. In Chapter 1, I outline the predictive framework of a MSGH, by creating a series of predictions of species interactions. The components of the MSGH predict that stressors of similar types (e.g., resource and nonresource) will have similar effects and be additive. On the other hand, varying species life history strategies and life stages will lead to extremes of plant interactions. In Chapter 2, I performed a series of experiments to test the various components of the MSGH. In Chapter 3, I performed a large-scale observational study to test whether multiple co-occurring stressors altered the cumulative effects on plant interactions, and if these stressors should be grouped (e.g., resource and non-resource, abiotic and biotic, etc.) to enhance predictability. From a series of studies conducted herein, I concluded that co-occurring stressors are important factors that control complex species interactions as shown in my MSGH modeling approach. Further, future theories need to incorporate species-specific and stressor specific grouping when modeling how species interactions shape communities. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2013.

The electrosensory and visual adaptations of elasmobranchs to the environment have been more studied than most other senses, however, work on these senses is mostly limited to descriptive analyses of sensitivity, morphology, and behavior. The goal of this work was to explore electrosensory and visual capabilities in a more ecological context. To gain an understanding of the content of bioelectric signals, the magnitude and frequency of these stimuli were recorded from a broad survey of elasmobranch prey items... Color vision adaptations also correlated to the photic environment of each species; cownose rays inhabit turbid, green-dominated waters and had two cone visual pigments that maximize contrast of objects against the green background... Yellow stingrays were trichromatic and likely possess the ability to discriminate colors in their clear, reef and seagrass habitats, which are spectrally rich. Both species showed evidence of ultraviolet sensitivity, which may aid in predator and conspecific detection as an enhanced communication channel. Future studies should investigate the integration of sensory input and sensory involvement in intraspecific communication to gain more insight into ecological adaptations. / by Christine N. Bedore. / Thesis (Ph.D.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

A irrigação na citricultura ganhou grande importância nos últimos oito anos, devido à utilização de porta-enxertos menos tolerantes a seca. Hoje grande parte da citricultura irrigada é feita por gotejamento, sistema em que apenas uma porcentagem do sistema radicular recebe água. Esses pontos tornam de grande valia estudos relacionados às respostas das plantas submetidas a diferentes áreas molhadas de solo e também ao estresse hídrico. Esse trabalho foi conduzido com o objetivo de avaliar as respostas fisiológicas de lima ácida Tahiti a pequenas porcentagens de área molhada. Foi avaliada condutância estomática (gs), transpiração (T), temperatura foliar (Tf), potencial de água na folha (), teor de clorofila e produtividade e qualidade de frutos. O experimento foi conduzido na fazenda Areão ESALQ/USP, Piracicaba, SP, em um pomar de 1ha de lima ácida Tahiti (Citrus latifolia Tanaka) enxertadas em citromelo Swingle (Poncitrus trifoliata (L.) x Citrus paradisi Macf.) no espaçamento 7x4m e irrigados por gotejamento. Para leituras de condutância estomática e transpiração foi utilizado um porômetro de equilíbrio dinâmico e balanço nulo LI-COR 1600 (Licor, Inc., Lincoln, EUA). Para temperatura da folha foi utilizado um termômetro de infravermelho (Scantenp). Para determinação de potencial de água na folha foi utilizado uma camâra de Scholander (Modelo 3005 Soil Mosture Equipament Co., Santa Bárbara, CA, EUA), e para determinação do teor de clorofila foi utilizado o um clorofiLOG (Falker). A avaliação de qualidade de frutos foi feita seguindo as metodologias propostas por Bleinroth et al. (1976). As diferentes porcentagens de área molhada foram dadas por diferentes números e tipos de gotejadores, de forma a aplicar sempre a mesma lâmina de irrigação. Os resultados mostraram que não houve diferença significativa entre os tratamentos para gs, T, e Tf, porém Tf foi sempre superior a temperatura do ar, podendo ser um indicador de deficiência hídrica. Quanto ao potencial hídrico das folhas, o tratamento não irrigado apresentou menores valores em relação aos tratamentos de maior área irrigada. O tratamento não irrigado também apresentou menores teores de clorofila, principalmente o teor de clorofila b, na face sul (mais sombreada). A produção e qualidade de frutos não apresentaram diferenças significativas. / The irrigation in citrus gained great importance in the last eight years, due to the use of rootstocks less tolerant to drought. Currently, much of the citrus is irrigated by drip irrigation system, where only a percentage of the root system receives water. These items make great value for studies related to the responses of plants subjected to different áreas of wet soil and also to water stress. This study aimed to evaluate the physiological responses of Tahiti lime fruit a small percentage of wetted area. Was evaluated stomatal conductance (gs), transpiration (T), leaf temperture (Tf), the leaf water potential (), chlorophyll content and productivity and quality of fruit. The experiment was conducted at the farm Areão ESALQ/USP, Piracicaba, Brazil, in a orchard of 1 ha of Tahit lime fruit (Citrus latifolia Tanaka) grafted in a citromelo Swingle (Poncitrus trifoliata (L.) x Citrus paradise Macf.) in a spacing of 7x4 m. For readings of stomatal condutance and transpiration was used a steady-state null-balcance porometer. For leaf temperature was used a infrared thermometer (Scantenp). To determine the potential of water on the sheet was used a Board of Scholander (Model 3005 - Soil Mosture Equipament Co., Santa Barbara, CA), and to determine the level of chlorophyll was used a clorofiLOG (Falker). The evaluate of quality of fruits was made following the methodology proposed by Bleinroth et al. (1976). The different percentages of wetted area were given by different numbers and types of drip, so as to always apply the same depth of irrigation. The results showed that there was no significant difference among treatments for gs, T, and Tf, but Tf was always higher than the air temperature and can be an indicator of water stress. As the water potential of the leaves, the non-irrigated treatment had lower values in relation to treatment of larger irrigated área. The nonirrigated treatment had lower levels of chlorophyll, especially the content of chlorophyll b, in the south side (more shaded). The production and quality of fruit showed no significant differences.

Recent increase in forest mortality events worldwide and their relationship with drought episodes highlight the importance of understanding tree resilience to a changing climate. Empirical models of forest mortality have been typically used and were focusing on carbon related variables such as growth to predict tree death. Recent efforts have shifted toward a more mechanistic modeling of mortality. Mechanistic approaches use tree traits and climate as inputs to model processes and represent carbon and water fluxes, all necessary to plant life. The advantage of mechanistic approaches is their ability to account for potential adaptation of trees to climate change, but also to physically explore the causes of vulnerability and resilience to droughts. Mechanistically, the atmospheric demand for moisture at the canopy level is communicated to the tree through stomata, creating a water gradient between the leaves and the roots, and resulting in the ascent of sap via the plant hydraulic structure. Depending on the climate (temperature, atmospheric dryness, light, precipitation), different architectures will perform differently at maintaining the gradient. For example, deep roots can access deep water in dry regions and shallow roots can access rare precipitation events whereas larger leaf area increases the atmospheric demand for moisture. In very harsh conditions such as extreme or lasting droughts, the hydraulic structure might suffer from a steep water gradient. Protection against excessive gradients can be achieved either through an investment in a stronger structure (denser wood) or through a regulation of the pulling force at the top of the canopy (closing leaf stomata). Evolution of structures and physiological strategies have resulted in fitness advantages and partially explain the diversity of species architectures across climates. More importantly, this diversity is at the core of the vulnerability and resilience of each species to increased aridity and frequency of extreme events, and therefore its mortality. This dissertation investigates the resilience to droughts of two co-occuring species in common woodlands of New Mexico, USA. This location is of specific interest because drought conditions (high temperature and/or low precipitation) have become more frequent as a result of global warming and because these ecosystems have suffered extensive mortality in the last decades. The two species, Pinus edulis and Juniper monosperma have very different physiological strategies, which allows for an extra level of vulnerability comprehension. To further test their resilience to extreme drought and possibly future climatic conditions, I studied trees that were subject to a six-year rain-reduction experiment. In the first part we develop a mechanistic model of the tree functioning that includes water and carbon fluxes and is based on their respective supply-demand balances. We use this simplified mechanistic model to study the sensitivity of mortality to hydraulic structure variations and to the physiological strategy of each species. We find that for both species death resulted from an irreversible damage of tissues transporting water. Despite P. edulis’s ability to close stomata to reduce the atmospheric demand, they died first because of their vulnerable tissues. In the second part, I specifically investigate P. edulis’s structural response to drought at the canopy level. By dissecting branch anatomy at an annual resolution, I find that during droughts this species increase relatively more leaf area (water demand) compared to transport area (water supply). I suggest that the structural adjustments that occur at the branch level do not contribute to the protection of the tissues transporting water. In the third part, I analyze the anatomy of these tissues in branches of P. edulis. I find that in response to long-lasting drought the trees built tissues more efficient at transporting water but also more vulnerable to future drought. By contrast, a short-intense drought decreases efficiency without changing vulnerability. I hence show that during lasting drought the anatomical adjustment of branch tissues increase the vulnerability of the piñons. This study shows the importance of considering climate responses of structure and physiology together to compare resilience across species. It also shows that adjustments of hydraulic elements in response to drought tend to decrease hydraulic resilience and could favor a run-away scenario. If the population of Pinus edulis - a dominant species of the Southwest US - were to decline, major shift should be expected in related ecosystems.