Some don't like it hot: microhabitat-dependent thermal and water stresses in a trailing edge population

The distributional limits of species in response to environmental change are usually studied at large temporal and/or geographical scales. However, organismal scale habitat variation can be overlooked when investigating large-scale averages of key factors such as temperature. We examine how microhabitat thermal conditions relate to physiological limits, which may contribute to recent range shifts in an intertidal alga. We defined the onset and maximum temperatures of the heat-shock response (HSR) for a southern edge population of Fucus vesiculosus, which has subsequently become extinct. The physiological threshold for resilience (assayed using chlorophyll fluorescence) coincided with declining HSR, determined from the temperature-dependent induction of seven heat-shock protein transcripts. In intertidal habitats, temperature affects physiology directly by controlling body temperature and indirectly through evaporative water loss. We investigated the relationship between the thermal environment and in situ molecular HSR at microhabitat scales. Over cm to m scales, four distinct microhabitats were defined in algal patches (canopy surface, patch edge, subcanopy, submerged channels), revealing distinct thermal and water stress environments during low-tide emersion. The in situ HSR agreed with estimated tissue temperatures in all but one microhabitat. Remarkably, in the most thermally extreme microhabitat (canopy surface), the HSR was essentially absent in desiccated tissue, providing a potential escape from the cellular metabolic costs of thermal stress. Meteorological records, microenvironmental thermal profiles and HSR data indicate that the maximum HSR is approached or exceeded in hydrated tissue during daytime low tides for much of the year. Furthermore, present-day summer seawater temperatures are sufficient to induce HSR during high-tide immersion, preventing recovery and resulting in continuous HSR during daytime low-tide cycles over the entire summer. HSR in the field matched microhabitat temperatures more closely than local seawater or atmospheric data, suggesting that the impacts of climatic change are best understood at the microhabitat scale, particularly in intertidal areas.FCT - Portuguese Science Foundation [POCTI/MAR/61105/2004, EXCL/AAG-GLO/0661/2012, SFRH/BPD/63/03/2009, SFRH/BD/74436/2010]info:eu-repo/semantics/publishedVersio

A genome-wide investigation of the worldwide invader Sargassum muticum shows high success albeit (almost) no genetic diversity

Twenty years of genetic studies of marine invaders have shown that successful invaders are often characterized by native and introduced populations displaying similar levels of genetic diversity. This pattern is presumably due to high propagule pressure and repeated introductions. The opposite pattern is reported in this study of the brown seaweed, Sargassum muticum, an emblematic species for circumglobal invasions. Albeit demonstrating polymorphism in the native range, microsatellites failed to detect any genetic variation over 1,269 individuals sampled from 46 locations over the Pacific-Atlantic introduction range. Single-nucleotide polymorphisms (SNPs) obtained from ddRAD sequencing revealed some genetic variation, but confirmed severe founder events in both the Pacific and Atlantic introduction ranges. Our study thus exemplifies the need for extreme caution in interpreting neutral genetic diversity as a proxy for invasive potential. Our results confirm a previously hypothesized transoceanic secondary introduction from NE Pacific to Europe. However, the SNP panel unexpectedly revealed two additional distinct genetic origins of introductions. Also, conversely to scenarios based on historical records, southern rather than northern NE Pacific populations could have seeded most of the European populations. Finally, the most recently introduced populations showed the lowest selfing rates, suggesting higher levels of recombination might be beneficial at the early stage of the introduction process (i.e., facilitating evolutionary novelties), whereas uniparental reproduction might be favored later in sustainably established populations (i.e., sustaining local adaptation).Agence Nationale de la Recherche - ANR-10-BTBR-04; European Regional Development Fund; Fundacao para a Ciencia e a Tecnologia - SFRH/BPD/107878/2015, UID/Multi/04326/2016, UID/Multi/04326/2019; Brittany Region;info:eu-repo/semantics/publishedVersio

Characterization and comparison of bacterial communities of an invasive and two native Caribbean seagrass species sheds light on the possible influence of the microbiome on invasive mechanisms

Invasive plants, including marine macrophytes, are one of the most important threats to biodiversity by displacing native species and organisms depending on them. Invasion success is dependent on interactions among living organisms, but their study has been mostly limited to negative interactions while positive interactions are mostly underlooked. Recent studies suggested that microorganisms associated with eukaryotic hosts may play a determinant role in the invasion process. Along with the knowledge of their structure, taxonomic composition, and potential functional profile, understanding how bacterial communities are associated with the invasive species and the threatened natives (species-specific/environmentally shaped/tissue-specific) can give us a holistic insight into the invasion mechanisms. Here, we aimed to compare the bacterial communities associated with leaves and roots of two native Caribbean seagrasses (Halodule wrightii and Thalassia testudinum) with those of the successful invader Halophila stipulacea, in the Caribbean island Curaçao, using 16S rRNA gene amplicon sequencing and functional prediction. Invasive seagrass microbiomes were more diverse and included three times more species-specific core OTUs than the natives. Associated bacterial communities were seagrass-specific, with higher similarities between natives than between invasive and native seagrasses for both communities associated with leaves and roots, despite their strong tissue differentiation. However, with a higher number of OTUs in common, the core community (i.e., OTUs occurring in at least 80% of the samples) of the native H. wrightii was more similar to that of the invader H. stipulacea than T. testudinum, which could reflect more similar essential needs (e.g., nutritional, adaptive, and physiological) between native and invasive, in contrast to the two natives that might share more environment-related OTUs. Relative to native seagrass species, the invasive H. stipulacea was enriched in halotolerant bacterial genera with plant growth-promoting properties (like Halomonas sp. and Lysinibacillus sp.) and other potential beneficial effects for hosts (e.g., heavy metal detoxifiers and quorum sensing inhibitors). Predicted functional profiles also revealed some advantageous traits on the invasive species such as detoxification pathways, protection against pathogens, and stress tolerance. Despite the predictive nature of our findings concerning the functional potential of the bacteria, this investigation provides novel and important insights into native vs. invasive seagrasses microbiome. We demonstrated that the bacterial community associated with the invasive seagrass H. stipulacea is different from native seagrasses, including some potentially beneficial bacteria, suggesting the importance of considering the microbiome dynamics as a possible and important influencing factor in the colonization of non-indigenous species. We suggest further comparison of H. stipulacea microbiome from its native range with that from both the Mediterranean and Caribbean habitats where this species has a contrasting invasion success. Also, our new findings open doors to a more in-depth investigation combining meta-omics with bacterial manipulation experiments in order to confirm any functional advantage in the microbiome of this invasive seagrass.CEECINST/00114/2018info:eu-repo/semantics/publishedVersio

Response of kelps from different latitudes to consecutive heat shock

Although extensive work has focused on kelp responses to constant temperature, little is known about their response to the consecutive temperature shocks they are often exposed to in the shallow subtidal and intertidal pools. Here we characterized the responses of the two southernmost forest-forming kelp species in the Northeast Atlantic, Laminaria ochroleuca De La Pylaie and Saccorhiza polyschides (Lightf.) Batt. to multiple cycles of thermal stress. Individuals from the upper vertical limit of the geographical distribution edges where the two species co-occur forming forests, France and Portugal, were exposed to 4 consecutive cycles of thermal shock simulating a spring tide. A 24 h cycle consisted of culture at 15 degrees C, plus 1 h heat shock at one of five levels (20, 22.5, 25, 27.5 or 30 degrees C). The maximum quantum yield (Fv/Fm) of chlorophyll fluorescence of photosystem 2 (PS2) was used to detect impaired reaction center function, as a proxy for individual fitness costs, during recovery from heat shock. Both species showed resilience to temperatures from 20 to 25 degrees C. While exposure to 27.5 degrees C caused no inhibition to Fv/Fm of S. polyschides, a threshold was met above this temperature and exposure to 30 degrees C caused the death of all individuals. In contrast, L ochroleuca from France was damaged but able to survive 30 degrees C shocks and individuals from Portugal showed complete resilience to this treatment. In both species, blade elongation decreased with increasing temperature, with necrosis surpassing growth at higher temperatures. Resilience to high temperature exposure may confer an advantage to L ochroleuca to colonize intertidal pools on the Portuguese coast, in agreement with the observation that both species recruit in tide pools but only L ochroleuca reach adulthood. Our results indicate that as summer temperatures increase with climate change, the disappearance of S. polyschides from intertidal pools and a decrease in the density of L ochroleuca can be expected. (C) 2014 Elsevier B.V. All rights reserved.ASSEMBLE (ASSociation of European Marine Biological Laboratories) [227799]; Portuguese Science and Technology Foundation (FCT); FCT [PTDC/AAC-CLI/109108/2008, EXCL/AAG-GLO/0661/2012]info:eu-repo/semantics/publishedVersio

Space-Efficient Simulation of Quantum Computers

Traditional algorithms for simulating quantum computers on classical ones require an exponentially large amount of memory, and so typically cannot simulate general quantum circuits with more than about 30 or so qubits on a typical PC-scale platform with only a few gigabytes of main memory. However, more memory-efficient simulations are possible, requiring only polynomial or even linear space in the size of the quantum circuit being simulated. In this paper, we describe one such technique, which was recently implemented at FSU in the form of a C++ program called SEQCSim, which we releasing publicly. We also discuss the potential benefits of this simulation in quantum computing research and education, and outline some possible directions for further progress.Comment: 6 pages, 3 figures, author reprint of final submitted manuscrip

Marine forests of the Mediterranean-Atlantic Cystoseira tamariscifolia complex show a southern Iberian genetic hotspot and no reproductive isolation in parapatry

Climate-driven range-shifts create evolutionary opportunities for allopatric divergence and subsequent contact, leading to genetic structuration and hybrid zones. We investigate how these processes influenced the evolution of a complex of three closely related Cystoseira spp., which are a key component of the Mediterranean-Atlantic seaweed forests that are undergoing population declines. The C. tamariscifolia complex, composed of C. tamariscifolia s.s., C. amentacea and C. mediterranea, have indistinct boundaries and natural hybridization is suspected. Our aims are to (1) infer the genetic structure and diversity of these species throughout their distribution ranges using microsatellite markers to identify ancient versus recent geographical populations, contact zones and reproductive barriers, and (2) hindcast past distributions using niche models to investigate the influence of past range shifts on genetic divergence at multiple spatial scales. Results supported a single, morphologically plastic species the genetic structure of which was incongruent with a priori species assignments. The low diversity and low singularity in northern European populations suggest recent colonization after the LGM. The southern Iberian genetic hotspot most likely results from the role of this area as a climatic refugium or a secondary contact zone between differentiated populations or both. We hypothesize that life-history traits (selfing, low dispersal) and prior colonization effects, rather than reproductive barriers, might explain the observed genetic discontinuities.Pew Charitable Trusts (USA); MARINERA, Spain [CTM2008-04183-E/MAR]; FCT (Portugal) [FCT-BIODIVERSA/004/2015, CCMAR/Multi/04326/2013, SFRH/BPD/107878/2015, SFRH/BPD/85040/2012]; FPU fellowship of the Spanish Ministry of Education; European Community ASSEMBLE visiting grant [00399/2012]; University of Cadi

Measurement of the temperature of an ultracold ion source using time-dependent electric fields

We report on a measurement of the characteristic temperature of an ultracold rubidium ion source, in which a cloud of laser-cooled atoms is converted to ions by photo-ionization. Extracted ion pulses are focused on a detector with a pulsed-field technique. The resulting experimental spot sizes are compared to particle-tracking simulations, from which a source temperature $T = (1 \pm 2)$ mK and the corresponding transversal reduced emittance $\epsilon_r = 7.9 X 10^{-9}$ m rad $\sqrt{\rm{eV}}$ are determined. We find that this result is likely limited by space charge forces even though the average number of ions per bunch is 0.022.Comment: 8 pages, 11 figure