Individual-based genetic analyses support asexual hydrochory dispersal in Zostera noltei

Dispersal beyond the local patch in clonal plants was typically thought to result from sexual reproduction via seed dispersal. However, evidence for the separation, transport by water, and re-establishment of asexual propagules (asexual hydrochory) is mounting suggesting other important means of dispersal in aquatic plants. Using an unprecedented sampling size and microsatellite genetic identification, we describe the distribution of seagrass clones along tens of km within a coastal lagoon in Southern Portugal. Our spatially explicit individual-based sampling design covered 84 km(2) and collected 3 185 Zostera noltei ramets from 803 sites. We estimated clone age, assuming rhizome elongation as the only mechanism of clone spread, and contrasted it with paleo-oceanographic sea level change. We also studied the association between a source of disturbance and the location of large clones. A total of 16 clones were sampled more than 10 times and the most abundant one was sampled 59 times. The largest distance between two samples from the same clone was 26.4 km and a total of 58 and 10 clones were sampled across more than 2 and 10 km, respectively. The number of extremely large clone sizes, and their old ages when assuming the rhizome elongation as the single causal mechanism, suggests other processes are behind the span of these clones. We discuss how the dispersal of vegetative fragments in a stepping-stone manner might have produced this pattern. We found higher probabilities to sample large clones away from the lagoon inlet, considered a source of disturbance. This study corroborates previous experiments on the success of transport and re-establishment of asexual fragments and supports the hypothesis that asexual hydrochory is responsible for the extent of these clones.Fundacao para a Ciencia e a Tecnologia, Portugal [PTDC/MAR/099887/2008]; Fundacao para a Ciencia e Tecnologia [SFRH/BD/68570/2010

Past climate changes and strong oceanographic barriers structured low-latitude genetic relics for the golden kelp Laminaria ochroleuca

Aim Drivers of intraspecific biodiversity include past climate-driven range shifts and contemporary ecological conditions mediating connectivity, but these are rarely integrated in a common comprehensive approach. This is particularly relevant for marine organisms, as ocean currents strongly influence population isolation or connectivity, keeping or diluting the signatures left by past climates. Here we ask whether the coupling between past range shifts and contemporary connectivity explain the extant gene pools of Laminaria ochroleuca, a large brown alga structuring important marine forests from shallow to deep infralittoral grounds. Location Northeastern Atlantic Ocean. Taxon Laminaria ochroleuca. Methods We estimated population genetic diversity and structure of L. ochroleuca across its entire distribution range using 15 polymorphic microsatellite markers. This was compared with the outcomes of a palaeoclimatic model predicting latitudinal and depth range shifts from the Last Glacial Maximum (LGM) to the present. Genetic differentiation was further compared with potential connectivity inferred with a biophysical model developed with high-resolution data from HYCOM (Hybrid Coordinate Ocean Model). Results The biogeographical distribution of genetic variability showed overall agreement with the predictions from independently inferred past range shifts. Multiple regions of persistence were identified in deep and upwelling settings at the lowest latitudes of the current species distribution, where higher and unique genetic diversity was retained. The biophysical model revealed that despite the possibility of long-distance migration, contemporary oceanographic barriers strongly restrict connectivity of isolated genetic lineages. Main conclusions Integrating different processes at biogeographical scales explained the extant gene pools of marine forests of L. ochroleuca. Low-latitude genetic relics harbour a disproportional evolutionary significance, persisting as ancient populations in isolated deep and upwelling climate refugia. Their inferred rates of dispersal may be insufficient to accommodate anticipated climate warming

Past climate changes and strong oceanographic barriers structured low‐latitude genetic relics for the golden kelp Laminaria ochroleuca

Aim Drivers of intraspecific biodiversity include past climate-driven range shifts and contemporary ecological conditions mediating connectivity, but these are rarely integrated in a common comprehensive approach. This is particularly relevant for marine organisms, as ocean currents strongly influence population isolation or connectivity, keeping or diluting the signatures left by past climates. Here we ask whether the coupling between past range shifts and contemporary connectivity explain the extant gene pools of Laminaria ochroleuca, a large brown alga structuring important marine forests from shallow to deep infralittoral grounds. Location Northeastern Atlantic Ocean. Taxon Laminaria ochroleuca. Methods We estimated population genetic diversity and structure of L. ochroleuca across its entire distribution range using 15 polymorphic microsatellite markers. This was compared with the outcomes of a palaeoclimatic model predicting latitudinal and depth range shifts from the Last Glacial Maximum (LGM) to the present. Genetic differentiation was further compared with potential connectivity inferred with a biophysical model developed with high-resolution data from HYCOM (Hybrid Coordinate Ocean Model). Results The biogeographical distribution of genetic variability showed overall agreement with the predictions from independently inferred past range shifts. Multiple regions of persistence were identified in deep and upwelling settings at the lowest latitudes of the current species distribution, where higher and unique genetic diversity was retained. The biophysical model revealed that despite the possibility of long-distance migration, contemporary oceanographic barriers strongly restrict connectivity of isolated genetic lineages. Main conclusions Integrating different processes at biogeographical scales explained the extant gene pools of marine forests of L. ochroleuca. Low-latitude genetic relics harbour a disproportional evolutionary significance, persisting as ancient populations in isolated deep and upwelling climate refugia. Their inferred rates of dispersal may be insufficient to accommodate anticipated climate warming

Room-Temperature Negative Capacitance in a Ferroelectric–Dielectric Superlattice Heterostructure

We demonstrate room-temperature negative capacitance in a ferroelectric–dielectric superlattice heterostructure. In epitaxially grown superlattice of ferroelectric BSTO (Ba_0.8Sr_0.2TiO₃) and dielectric LAO (LaAlO₃), capacitance was found to be larger compared to the constituent LAO (dielectric) capacitance. This enhancement of capacitance in a series combination of two capacitors indicates that the ferroelectric was stabilized in a state of negative capacitance. Negative capacitance was observed for superlattices grown on three different substrates (SrTiO₃ (001), DyScO₃ (110), and GdScO₃ (110)) covering a large range of substrate strain. This demonstrates the robustness of the effect as well as potential for controlling the negative capacitance effect using epitaxial strain. Room-temperature demonstration of negative capacitance is an important step toward lowering the subthreshold swing in a transistor below the intrinsic thermodynamic limit of 60 mV/decade and thereby improving energy efficiency