Molecular Phylogeny of Grey Mullets Based on Mitochondrial DNA Sequence Analysis: Evidence of a Differential Rate of Evolution at the Intrafamily Level

The phylogeny of the grey mullets is considered problematic both at the intra- and interfamily level. Such a difficulty arises from the highly homogeneous morphology displayed by this group of fish and, consequently, from the paucity of the key morphological characters suitable to address their phylogeny and evolution. In the present work, we have approached the phylogenetic and evolutionary relationships of seven species of Mugilidae, six of which from the Mediterranean Sea, on the basis of the DNA sequences of two mitochondrial genes (cytochromeband 12S rRNA). Despite the morphological homogeneity exhibited by the taxa considered, the two species of the genusMugil(M. cephalusandM. curema) showed a remarkable genetic divergence compared to all the other members of the family. The relative rate test revealed a significantly higher rate of evolution along theMugillineage.     

EVIDENCE FOR SELECTION ON A CHORDATE HISTOCOMPATIBILITY LOCUS

Allorecognition is the ability of an organism to differentiate self or close relatives from unrelated individuals. The best known applications of allorecognition are the prevention of inbreeding in hermaphroditic species (e.g., the self‐incompatibility [SI] systems in plants), the vertebrate immune response to foreign antigens mediated by MHC loci, and somatic fusion, where two genetically independent individuals physically join to become a chimera. In the few model systems where the loci governing allorecognition outcomes have been identified, the corresponding proteins have exhibited exceptional polymorphism. But information about the evolution of this polymorphism outside MHC is limited. We address this subject in the ascidian Botryllus schlosseri, where allorecognition outcomes are determined by a single locus, called FuHC (Fusion/HistoCompatibility). Molecular variation in FuHC is distributed almost entirely within populations, with very little evidence for differentiation among different populations. Mutation plays a larger role than recombination in the creation of FuHC polymorphism. A selection statistic, neutrality tests, and distribution of variation within and among different populations all provide evidence for selection acting on FuHC, but are not in agreement as to whether the selection is balancing or directional.     

Miscanthus × giganteus and Arundo donax shoot and rhizome tolerance of extreme moisture stress

Crops grown for bioenergy production are a mandated component of the United States energy portfolio. Giant miscanthus (Miscanthus × giganteus) is a leading bioenergy crop similar in habit to the invasive plant giant reed (Arundo donax). To characterize the environmental tolerance of giant miscanthus, we compared the soil moisture stress tolerance of giant miscanthus and giant reed under glasshouse conditions. We subjected both species to soil moisture conditions of severe drought (?4.2 MPa), mild drought (?0.5 MPa), field‐capacity (control), and flooded soils. These conditions were applied to two cohorts: one in which soil moisture conditions were imposed on newly planted rhizome fragments, and one in which conditions were imposed on established plants after 8 weeks of growth in field‐capacity soil. After 16 weeks, we harvested all plants, measured above‐ and belowground biomass, and evaluated the reproductive viability of rhizome fragments. The total biomass of each species under flooded conditions was not different from the field‐capacity control groups regardless of cohort. However, drought did affect the two cohorts differently. In the cohort treated after 8 weeks of growth, mild and severe drought conditions resulted in 56% and 66% reductions in biomass, averaged over both species, compared with the controls. In the cohort treated for the entire 16 weeks, mild and severe drought conditions resulted in 92% and 94% reductions in biomass. Rhizome fragments from both species and both cohorts showed 100% viability following flooded and control treatments; drought treatments reduced rhizome viability in both species, with a greater impact on giant miscanthus. Although giant miscanthus does not appear to have the potential to escape and establish in relatively dry upland ecosystems, it does show tolerance to flooded conditions similar to giant reed.     

Isolation and characterization of microsatellites in the Adriatic sturgeon (Acipenser naccarii)

We isolated and characterized seven polymorphic microsatellite loci from a partial genomic library of the Adriatic sturgeon (Acipenser naccarii) enriched for GATA repeats. Variability was tested in 20 specimens of this endangered species. Our data support the tetraploid condition for A. naccarii and will be useful for the investigation of the remnant genetic variability of this species as well as for genetic tagging studies.