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Plants inhabiting environments with stressful conditions often exhibit a low number of flowers, which can be attributed to the energetic cost associated with reproduction. One of the most stressful environments for plants is the Antarctic continent, characterized by limited soil water availability and low temperatures. Induction of dehydrins like those from the COR gene family and auxin transcriptional response repressor genes (IAAs), which are involved in floral repression, has been described in response to water stress. Here, we investigated the relationship between the water deficit‐induced stress response and the number of flowers in Colobanthus quitensis plants collected from populations along a latitudinal gradient. The expression levels of COR47 and IAA12 genes in response to water deficit were found to be associated with the number of flowers. The relationship was observed both in the field and growth chambers. Watering the plants in the growth chambers alleviated the stress and stimualted flowering, thereby eliminating the trade‐off observed in the field. Our study provides a mechanistic understanding of the ecological constraints on plant reproduction along a water availability gradient. However, further experiments are needed to elucidate the primary role of water availability in regulating resource allocation to reproduction in plants inhibiting extreme environments. [ABSTRACT FROM AUTHOR]

Invasive plants may displace native species. This is the case for Poa annua, the only non-native plant species successfully established in Maritime Antarctica. Nonetheless, it is uncertain which factors drive the competitive success of P. annua in the harsh environmental conditions of the region. The ability of this plant species to establish novel mutualistic interactions with resident soil fungi may be crucial for its invasiveness. Such ability may be linked to the vertical transmission of fungal endophytes via seeds. We undertook a study to assess the role of seed fungal endophytes as promoters of the establishment and invasion of Poa annua in Maritime Antarctica. We explored the composition and diversity of fungal communities associated with different P. annua tissues (seeds, leaves and roots) and the soil. We also measured parameters including germination rate, above-ground biomass, reproductive structures, and the survival of invasive P. annua as well as of the native Colobanthus quitensis and Deschampsia antarctica grown from seeds with and without endophytes. Furthermore, we conducted inter- and intraspecific competition experiments among native and invasive plants, where chemically mediated plant-to-plant interference (allelopathy) and plant growth rate were measured to calculate a relative competition index. We found that fungal endophyte taxa associated with P. annua tissues were very different from those in the soil. Fungal endophytes in P. annua differed among seed, root and shoot tissues, which suggests low transmission among different organs. The removal of endophytes from P. annua seeds was associated with reduced seed germination, plant growth and survivorship, while the competitive ability of P. annua (assessed by accumulated biomass) relative to native species, as well as levels of allelochemicals in soils, were higher in the presence of seed fungal endophytes. Our results suggest that fungal endophytes, maternally inherited through seeds, improve host fitness and may contribute to the invasive success of P. annua in Antarctica. [ABSTRACT FROM AUTHOR]

Beneficial plant-associated microorganisms, such as fungal endophytes, are key partners that normally improve plant survival under different environmental stresses. It has been shown that microorganisms from extreme environments, like those associated with the roots of Antarctica plants, can be good partners to increase the performance of crop plants and to restore endangered native plants. Nothofagus alessandrii and N. glauca , are among the most endangered species of Chile, restricted to a narrow and/or limited distributional range associated mainly to the Maulino forest in Chile. Here we evaluated the effect of the inoculation with a fungal consortium of root endophytes isolated from the Antarctic host plant Colobanthus quitensis on the ecophysiological performance [photosynthesis, water use efficiency (WUE), and growth] of both endangered tree species. We also, tested how Antarctic root-fungal endophytes could affect the potential distribution of N. alessandrii through niche modeling. Additionally, we conducted a transplant experiment recording plant survival on 2 years in order to validate the model. Lastly, to evaluate if inoculation with Antarctic endophytes has negative impacts on native soil microorganisms, we compared the biodiversity of fungi and bacterial in the rhizospheric soil of transplanted individuals of N. alessandrii inoculated and non-inoculated with fungal endophytes. We found that inoculation with root-endophytes produced significant increases in N. alessandrii and N. glauca photosynthetic rates, water use efficiencies and cumulative growth. In N. alessandrii , seedling survival was significantly greater on inoculated plants compared with non-inoculated individuals. For this species, a spatial distribution modeling revealed that, inoculation with root-fungal endophytes could potentially increase the current distributional range by almost threefold. Inoculation with root-fungal endophytes, did not reduce native rhizospheric microbiome diversity. Our results suggest that the studied consortium of Antarctic root-fungal endophytes improve the ecophysiological performance as well as the survival of inoculated trees and can be used as a biotechnological tool for the restoration of endangered tree species. [ABSTRACT FROM AUTHOR]

Aim: Antarctica's remote and extreme terrestrial environments are inhabited by only two species of native vascular plants. We assessed genetic connectivity amongst Antarctic and South American populations of one of these species, Colobanthus quitensis, to determine its origin and age in Antarctica. Location: Maritime Antarctic, sub‐Antarctic islands, South America. Taxon: Antarctic pearlwort Colobanthus quitensis (Caryophyllaceae). Methods: Four chloroplast markers and one nuclear marker were sequenced from 270 samples from a latitudinal transect spanning 21–68° S. Phylogeographic, population genetic and molecular dating analyses were used to assess the demographic history of C. quitensis and the age of the species in Antarctica. Results: Maritime Antarctic populations consisted of two different haplotype clusters, occupying the northern and southern Maritime Antarctic. Molecular dating analyses suggested C. quitensis to be a young (<1 Ma) species, with contemporary population structure derived since the late‐Pleistocene. Main conclusions.: The Maritime Antarctic populations likely derived from two independent, late‐Pleistocene dispersal events. Both clusters shared haplotypes with sub‐Antarctic South Georgia, suggesting higher connectivity across the Southern Ocean than previously thought. The overall findings of multiple colonization events by a vascular plant species to Antarctica, and the recent timing of these events, are of significance with respect to future colonizations of the Antarctic Peninsula by vascular plants, particularly with predicted increases in ice‐free land in this area. This study fills a significant gap in our knowledge of the age of the contemporary Antarctic terrestrial biota. Adding to previous inferences on the other Antarctic vascular plant species (the grass Deschampsia antarctica), we suggest that both angiosperm species are likely to have arrived on a recent (late‐Pleistocene) time‐scale. While most major groups of Antarctic terrestrial biota include examples of much longer‐term Antarctic persistence, the vascular flora stands out as the first identified terrestrial group that appears to be of recent origin. [ABSTRACT FROM AUTHOR]

Functional symbiosis is considered one of the successful mechanisms by which plants that inhabit extreme environment improve their ability to tolerate different types of stress. One of the most conspicuous type of symbiosis is the endophyticism. This interaction has been noted to play a role in the adaptation of the native vascular plant Colobanthus quitensis to the stressful environments of Antarctica, characterized by low temperatures and extreme aridity. Projections of climate change for this ecosystem indicate that abiotic conditions will be less limiting due to an increase in temperature and water availability in the soil. Due to this decrease in stress induced by the climate change, it has been suggested that the positive role of fungal endophytes on performance of C. quitensis plants would decrease. In this study, we evaluated the role of endophytic fungi on osmoprotective molecules (sugar production, proline, oxidative stress) and gene expression (CqNCED1 , CqABCG25 , and CqRD22) as well as physiological traits (stomatal opening, net photosynthesis, and stomatal conductance) in individuals of C. quitensis. Individual plants of C. quitensis with (E+) and without (E−) endophytic fungi were exposed to simulated conditions of increased water availability (W+), having the current limiting water condition (W−) in Antarctica as control. The results reveal an endophyte-mediated lower oxidative stress, higher production of sugars and proline in plants. In addition, E+ plants showed differential expressions in genes related with drought stress response, which was more evident in W− than in W+. These parameters corresponded with increased physiological mechanisms such as higher net photosynthesis, stomatal opening and conductance under presence of endophytes (E+) as well as the projected water condition (W+) for Antarctica. These results suggest that the presence of fungal endophytes plays a positive role in favoring tolerance to drought in C. quitensis. However, this positive role would be diminished if the stress factor is relaxed, suggesting that the role of endophytes could be less important under a future scenario of climate change in Antarctica with higher soil water availability. [ABSTRACT FROM AUTHOR]

Most climate and environmental change models predict significant increases in temperature and precipitation by the end of the 21st Century, for which the current functional output of certain symbioses may also be altered. In this context we address the following questions: 1) How the expected changes in abiotic factors (temperature, and water) differentially affect the ecophysiological performance of the plant Colobanthus quitensis? and 2) Will this environmental change indirectly affect C. quitensis photochemical performance and biomass accumulation by modifying its association with fungal endophytes? Plants of C. quitensis from King George Island in the South Shetland archipelago (62°09′ S), and Lagotellerie Island in the Antarctic Peninsula (65°53′ S) were put under simulated abiotic conditions in growth chambers following predictive models of global climate change (GCC). The indirect effect of GCC on the interaction between C. quitensis and fungal endophytes was assessed in a field experiment carried out in the Antarctica, in which we eliminated endophytes under contemporary conditions and applied experimental watering to simulate increased precipitation input. We measured four proxies of plant performance. First, we found that warming (+W) significantly increased plant performance, however its effect tended to be less than watering (+W) and combined warming and watering (+T°+W). Second, the presence of fungal endophytes improved plant performance, and its effect was significantly decreased under experimental watering. Our results indicate that both biotic and abiotic factors affect ecophysiological performance, and the directions of these influences will change with climate change. Our findings provide valuable information that will help to predict future population spread and evolution through using ecological niche models under different climatic scenarios. [ABSTRACT FROM AUTHOR]

Questions Is the macrolichen Usnea antarctica a 'nurse' species to Antarctic flora? Are positive plant-plant interactions more frequent than negative interactions in Antarctic ecosystems? Are microclimatic modifications by cushions of U. antarctica responsible for the nurse effect? Location Two sites in Antarctica: King George Island, South Shetland (62°11′ S, 58°56′ W; 62°11′ S, 58°59′ W). Methods We evaluated the association of plant species with U. antarctica cushions by recording species growing - in equivalent areas - within and outside U. antarctica cushions. Additionally, we performed transplant experiments with Deschampsia antarctica individuals to assess if U. antarctica cushions enhance plant survival. In both study sites we monitored temperature, moisture and nutrient status of soil outside and within the cushions to provide insights into potential mechanisms underlying possible interactions between U. antarctica and other plant species. Results Eight out of 13 species were positively associated with cushions of the widespread lichen U. antarctica, while only one species ( U. aurantiaco-atra) showed a negative association with U. antarctica. Survival of Deschampsia was enhanced when growing associated with U. antarctica cushions. Our results indicate that cushions ameliorated the extreme conditions of Antarctic islands through increased temperature and soil moisture, decreased radiation and evaporative water loss and increased nutrient availability. Conclusions The nurse effect of U. antarctica is verified. Cushions of this macrolichen may be a key component in structuring the Antarctic landscape and maintaining local species richness, and their presence might influence range expansion of other species. [ABSTRACT FROM AUTHOR]

In a current article in the Journal of Vegetation Science, Casanova-Katny et al. addressed a comment about an article by Molina-Montenegro et al., which demonstrated the climate modification induced by the macrolichen Usnea antarctica and its role as facilitator. They provided useful corrections concerning species identification and pointed out several issues that, in their view, weakened our study. They indicated that the role of U. antarctica as a facilitative species in the maritime Antarctica is merely philosophical and has no ecological relevance. In this commentary, we argue why these critiques are unsubstantial, and provide evidence that the macrolichen can modify the microclimate, ameliorating the harsh conditions prevailing in Antarctica, establishing positive interactions and eventually facilitating vascular species. Thus, the macrolichen U. antarctica would act as a 'nurse species', playing a key role in structuring the maritime Antarctic plant community. [ABSTRACT FROM AUTHOR]

Maritime Antarctica is one of the most stressful environments for plant life worldwide. However, two vascular plant species (Deschampsia antarctica and Colobanthus quitensis) have been able to colonize this hostile environment. Although it has been proposed that C. quitensis possesses tolerance mechanisms and adaptations allowing survival and growth under such stressful conditions, the underlying molecular/transcriptional mechanisms are currently unknown. Furthermore, the impact of global warming on the endophytic and epiphytic organisms associated with C. quitensis remains unclear. Here, a metatranscriptomic approach was used to determine the effect of an in situ simulated global warming scenario on C. quitensis plants. We found a large number of differentially expressed genes successfully annotated (2,997), suggesting that climate change modulates the metatranscriptome of C. quitensis plants and associated endophytes and epiphytes. Interestingly, 50.5% and 26.8% of up- and down-regulated genes, respectively, are from non-plant species (putative endophytic and epiphytic organisms, such as fungi). Interestingly, Gene Ontology analysis pointed out several biological processes differentially enriched in non-plant microorganisms associated with C. quitensis grown in a simulated global warming scenario. Taken together, these results suggest that climatic drivers are shaping plant-microorganism interactions, and that endophytes/epiphytes may play crucial roles in plant adaptation to extreme environmental conditions. [ABSTRACT FROM AUTHOR]