Molecular analyses of turf algae reveal a new species and an undetected introduction in the Pterosiphonieae (Rhodomelaceae,Rhodophyta)

Introduced seaweeds and undescribed species often remain undetected because marine regional floras are as yet poorly understood. DNA sequencing facilitates their detection, but databases are incomplete, so their improvement will continue to lead the discovery of these species. Here we aim to clarify the taxonomy of two turf-forming red algal Australian species that morphologically resemble the European Aphanocladia stichidiosa. We also aim to elucidate whether either of these species could have been introduced in Europe or Australia. We studied their morphology, analyzed 17 rbcL sequences of European and Australian specimens, examined their generic assignment using a phylogeny based on 24 plastid genomes, and investigated their biogeography using a taxon-rich phylogeny including 52 rbcL sequences of species in the Pterosiphonieae. The rbcL sequences of one of the Australian species were identical to A. stichidiosa from Europe, considerably expanding its known distribution. Unexpectedly, our phylogenetic analyses resolved this species in the Lophurella clade rather than in Aphanocladia and the new combination L. stichidiosa is proposed. The other Australian species is described as L. pseudocorticata sp. nov. Although L. stichidiosa was originally described in the Mediterranean ca. 70 years ago, our phylogenetic analyses placed it in a lineage restricted to the southern hemisphere, showing that it is native to Australia and introduced to Europe. This study confirms that further work using molecular tools is needed to characterize seaweed diversity, especially among the poorly explored algal turfs, and showcases the usefulness of phylogenetic approaches to uncover introduced species and to determine their native ranges.     

A quantitative approach to characterizing cell lysis caused by mechanical agitation of Streptomyces clavuligerus

Streptomyces clavuligerus is a commercially important actinomycete that is used to produce clavulanic acid, a beta-lactamase inhibitor. Observations during 10 batch cultivations with S. clavuligerus on defined media have led to the finding that the organism is very sensitive to shear when grown in batch cultures with increasing stirrer speed. The stirrer speed was increased to keep the dissolved oxygen level above 50% air saturation. A quantitative approach based on the calculation of elemental balances and a simple mathematical model is proposed to characterize the biomass lysis. Finally, a linear relation between biomass yield and observed specific growth rate is determined. Results show that cell lysis occurs at a high degradation rate, e.g., mu(max) = 0.16 h(-1) and k(d) = 0.07 h(-1), when the gassed power input increases above 1.1, 1.7, or 2.0 kW/m(3), respectively, depending on the medium composition. The overall biomass yield on substrate is dramatically reduced in all experiments (>30%).     

Context-dependent specialisation drives temporal dynamics in intra- and inter-individual variation in foraging behaviour within a generalist bird population

Individual niche variation is common within animal populations, and has significant implications for a wide range of ecological and evolutionary processes. However, individual niche differences may also temporally vary as a result of behavioural plasticity. While it is well understood how niche variation is affected by changes in resource availability, comparatively little is known about the extent to which individual niche differences may vary within the annual cycle due to internal drivers. Here, we assess how time- and energy-constraints imposed by incubating and brood rearing affect inter- and intra-individual variation in the foraging behaviour of lesser black-backed gulls, a generalist seabird with strong individual niche variation. To this end, we compared daily foraging trips of 22 breeding and 23 non-breeding GPS-tracked adult gulls from two colonies in the Southern Bight of the North Sea over the course of the breeding season. We find that breeding birds, unlike non-breeding ones, did indeed alter their foraging behaviour during the breeding season. Both sexes reduced their searching effort by increasingly revisiting earlier foraging locations, allowing for shorter and more frequent foraging trips. Breeding females also showed pronounced shifts in their habitat use and strongly specialised on urbanised foraging habitats throughout the breeding season. Hence, while individual variation in habitat use remained largely consistent within non-breeders and in breeding males, individual variation among breeding females almost completely disappeared. Female lesser black-backed gulls are on average smaller, and therefore often outcompeted by males for the most profitable food sources. The temporal specialisation on spatially reliable anthropogenic food sources during breeding hence suggests a complex interplay between intrinsic competitive constraints, resource reliability and shifting time- and energy budges in shaping temporal dynamics in individual niche variation within our study population.     

DNA sequencing and anatomy demonstrate that Pacific Codium simulans is a genetically variable species found in the floras of Bermuda and Florida

When DNA sequences from Bermuda plants described as Codium isthmocladum ssp. clavatum and a recent collection from Florida originally thought to be C. decorticatum were analyzed, they were found to be a genetic match to the Pacific Mexican species C. simulans. Historical voucher collections assigned to C. isthmocladum ssp. clavatum show that this Pacific lineage has been present in Bermuda (Atlantic) waters for over a century, thus precluding a very recent introduction from the Pacific. We hypothesize that C. simulans may have hitched a ride on the ballast rocks of early commercial ships plying their trade between the Pacific and Atlantic Oceans.     

Climate change impact on seaweed meadow distribution in the North Atlantic rocky intertidal

The North-Atlantic has warmed faster than all other ocean basins and climate change scenarios predict sea surface temperature isotherms to shift up to 600 km northwards by the end of the 21st century. The pole-ward shift has already begun for many temperate seaweed species that are important intertidal foundation species. We asked the question: Where will climate change have the greatest impact on three foundational, macroalgal species that occur along North-Atlantic shores: Fucus serratus, Fucus vesiculosus, and Ascophyllum nodosum? To predict distributional changes of these key species under three IPCC (Intergovernmental Panel on Climate Change) climate change scenarios (A2, A1B, and B1) over the coming two centuries, we generated Ecological Niche Models with the program MAXENT. Model predictions suggest that these three species will shift northwards as an assemblage or “unit” and that phytogeographic changes will be most pronounced in the southern Arctic and the southern temperate provinces. Our models predict that Arctic shores in Canada, Greenland, and Spitsbergen will become suitable for all three species by 2100. Shores south of 45° North will become unsuitable for at least two of the three focal species on both the Northwest- and Northeast-Atlantic coasts by 2200. If these foundational species are unable to adapt to the rising temperatures, they will lose their centers of genetic diversity and their loss will trigger an unpredictable shift in the North-Atlantic intertidal ecosystem.     

Phylogeny and taxonomy of Halimeda incrassata,including descriptions of H. kanaloana and H. heteromorpha spp. nov. (Bryopsidales,Chlorophyta)

The tropical green algal genus Halimeda is one of the best studied examples of pseudo-cryptic diversity within the algae. Previous molecular and morphometric studies revealed that within Halimeda section Rhipsalis, Halimeda incrassata included three pseudo-cryptic entities and that the morphological boundaries between H. incrassata and Halimeda melanesica were ill-defined. In this paper, the taxonomy of H. incrassata is revised: two pseudo-cryptic entities are described as new species, Halimeda kanaloana and Halimed heteromorpha, while H. incrassata is redefined to encompass a single, monophyletic entity. Similarities and differences between the three species and H. melanesica are discussed. Monophyly of H. heteromorpha, which was questioned in a former study, is reinvestigated using sets of 32 ITS1–ITS2 and 21 plastid rps3 sequences and various alignment and inference methods. The phylogenetic relationships within Halimeda section Rhipsalis are inferred from nuclear 18S–ITS1–5.8S–ITS2 and concatenated plastid sequences (tufA & rpl5–rps8–infA) and interpreted in a biogeographic context.     

Protein lysine methylation contributes to modulating the response of sensitive and tolerant Arabidopsis species to cadmium stress

The mechanisms underlying the response and adaptation of plants to excess of trace elements are not fully described. Here, we analysed the importance of protein lysine methylation for plants to cope with cadmium. We analysed the effect of cadmium on lysine-methylated proteins and protein lysine methyltransferases (KMTs) in two cadmium-sensitive species, Arabidopsis thaliana and A. lyrata, and in three populations of A. halleri with contrasting cadmium accumulation and tolerance traits. We showed that some proteins are differentially methylated at lysine residues in response to Cd and that a few genes coding KMTs are regulated by cadmium. Also, we showed that 9 out of 23 A. thaliana mutants disrupted in KMT genes have a tolerance to cadmium that is significantly different from that of wild-type seedlings. We further characterized two of these mutants, one was knocked out in the calmodulin lysine methyltransferase gene and displayed increased tolerance to cadmium, and the other was interrupted in a KMT gene of unknown function and showed a decreased capacity to cope with cadmium. Together, our results showed that lysine methylation of non-histone proteins is impacted by cadmium and that several methylation events are important for modulating the response of Arabidopsis plants to cadmium stress.