E-commerce and Caulerpa: unregulated dispersal of invasive species

Professional aquarists and hobbyists are thought to be the source of invasions of the aquarium strain of the green macroalga Caulerpa taxi folia in the Mediterranean, southern California, and Australia. The US Department of Agriculture, Animal and Plant Health Inspection Service (USDA-APHIS) restricted interstate commerce and importation of the Mediterranean clone of C taxi folia prior to the California invasion and is currently deciding if it should strengthen regulation of this genus as more species of Caulerpa are being described as invasive. Here we document the importance of e-commerce as a mode of dispersal for many species of Caulerpa in the United States. We purchased Caulerpa from 30 internet retailers and 60 internet auction sites representing 25 states and Great Britain. Twelve different Caulerpa species were confirmed using DNA sequencing. Only 10.6% of sellers provided the correct genus and species names with their shipments. Thirty purchases of live rock provided four species of Caulerpa, as well as 53 additional marine species. Our results confirm the extensive e-commerce availability of this invasive genus and its high dispersal potential via postal services and hobbyists. We recommend that both eBay and the USDA maximize regulation of Caulerpa

The genome of the seagrass Zostera marina reveals angiosperm adaptation to the sea

Seagrasses colonized the sea(1) on at least three independent occasions to form the basis of one of the most productive and widespread coastal ecosystems on the planet(2). Here we report the genome of Zostera marina (L.), the first, to our knowledge, marine angiosperm to be fully sequenced. This reveals unique insights into the genomic losses and gains involved in achieving the structural and physiological adaptations required for its marine lifestyle, arguably the most severe habitat shift ever accomplished by flowering plants. Key angiosperm innovations that were lost include the entire repertoire of stomatal genes(3), genes involved in the synthesis of terpenoids and ethylene signalling, and genes for ultraviolet protection and phytochromes for far-red sensing. Seagrasses have also regained functions enabling them to adjust to full salinity. Their cell walls contain all of the polysaccharides typical of land plants, but also contain polyanionic, low-methylated pectins and sulfated galactans, a feature shared with the cell walls of all macroalgae(4) and that is important for ion homoeostasis, nutrient uptake and O-2/CO2 exchange through leaf epidermal cells. The Z. marina genome resource will markedly advance a wide range of functional ecological studies from adaptation of marine ecosystems under climate warming(5,6), to unravelling the mechanisms of osmoregulation under high salinities that may further inform our understanding of the evolution of salt tolerance in crop plants(7)

Genetic diversity and connectivity remain high in eelgrass Zostera marina populations in the Wadden Sea, despite major impacts

Beginning in the 1930s, eelgrass meadows declined throughout the Wadden Sea, leaving populations susceptible to extinction through patchiness, low density and isolation. Additional anthropogenic impacts have altered current regimes, nutrients and turbidity-all of which affect eelgrass. Recent abiotic modeling studies suggest that poor recovery is the result of a regime shift caused by the loss of positive feedbacks between seagrass meadows and their capacity to mediate turbidity. Additionally, it is hypothesized that genetic and demographic factors-in particular, the loss of genetic diversity and patch connectivity-have contributed to lower fitness of eelgrass, thereby further diminishing recovery potential. We assessed genetic diversity and connectivity of Zostera marina among 19 locations, covering some 950 km of coastline between Zeeland, Netherlands and Langholmen, Sweden. Both allelic and genotypic diversity were high. A Bayesian analysis of population structure revealed 6 significant clusters of subpopulations that are connected by varying degrees of dispersal. Although population divergence was significant at as little as 5 km, isolation by distance was very weak, indicating high connectivity at scales of 1.50 km. A demographic interpretation of these data suggests that realized gene flow is strong and predominantly northward, leaving the western Wadden Sea relatively isolated. The failure of eelgrass to recover in the western Wadden Sea is, therefore, due to both unsuitable physical conditions and low incoming gene flow, Nonetheless, the greater Wadden Sea can be considered a seed transfer zone providing source material for restoration efforts in any areas where abiotic conditions are more favorable

Genotypic relationships between Prochloron samples from different localities and hosts as determined by DNA-DNA reassociations

Genotypic relationships between seven Prochloron samples isolated from different didemnid ascidian hosts collected at the Palau archipelago and Munda (Solomon Islands) and one cyanobacterial (Synechocystis) strain were determined by DNA-DNA reassociations. Thermal stability values of DNA-DNA hybrids indicate that all Prochloron samples involved are mutually very closely related and only slightly related with the Synechocystis strain. It is concluded that the Prochloron samples tested are representatives of one and the same species

A fast and inexpensive DNA extraction/purification protocol for brown macroalgae

Here we describe a rapid method for extracting DNA from dried brown algae material using a microtitre plate system in conjunction with a milling instrument. The method allows the preparation of nuclear and organelle DNA of quality suitable for polymerase chain reaction amplification. It combines high throughput with low cost per sample: DNA from 192 samples can be extracted in c. 3 h for <EURO0.40 per sample, nearly tenfold cheaper than commercially available kits. Furthermore, by using microtitre plates, efficient storage and downstream processing is facilitated

Phylogeography and population structure of thornback rays (Raja clavata L., Rajidae)

The phylogeography of thornback rays (Raja clavata) was assessed from European waters, using five nuclear microsatellite loci and mitochondrial cytochome b sequences. Strong regional differentiation was found between the Mediterranean basin, the Azores and the European continental shelf. Allelic and haplotype diversities were high in Portuguese populations, consistent with the existence of a refugium along the Iberian Peninsula. Unexpectedly, high diversity was also found in the English Channel/North Sea area. The lowest genetic diversity was found in the Black Sea. Populations sampled from the Mediterranean, Adriatic and Black Seas were characterized by a single mitochondrial haplotype. This haplotype was also the most ancestral and widespread outside of the Mediterranean basin except for the Azores. Populations from the Azores were dominated by a second ancestral haplotype which was shared with British populations. Results from multidimensional scaling, amova and nested clade analysis indicate that British waters are a secondary contact zone recolonized from at least two refugia - one around the Iberian Peninsula and one possibly in the Azores. Links to a potential refugium known as the Hurd Deep, between Cornwall and Brittany, are discussed. Finally, a historical demographic analysis indicates that thornback ray populations started to expand between 580 000 and 362 000 years ago, which suggests that the Last Glacial Maximum (20 000 years ago) had mainly affected the distribution of populations rather than population size