Genetically monomorphic invasive populations of the rapa whelk,Rapana venosa

Rapana venosa is a predatory marine gastropod native to the coastal waters of China, Korea, and Japan. Since the 1940s, R. venosa has been transported around the globe and introduced populations now exist in the Black Sea, the Mediterranean Sea, the Adriatic and Aegean seas, off the coasts of France and the Netherlands, in Chesapeake Bay, Virginia, USA, and in the Rio de la Plata between Uruguay and Argentina. This study surveyed variation in two mitochondrial gene regions to investigate the invasion pathways of R. venosa, identify likely sources for introduced populations, and evaluate current hypotheses of potential transportation vectors. Sequence data were obtained for the mitochondrial cytochrome c oxidase I and NADH dehydrogenase subunit 2 gene regions of 178 individuals from eight native locations and 106 individuals from 12 introduced locations. Collections from within the native range displayed very high levels of genetic variation while collections from all introduced populations showed a complete lack of genetic diversity; a single haplotype was common to all introduced individuals. This finding is consistent with the hypothesis that R. venosa was initially introduced into the Black Sea, and this Black Sea population then served as a source for the other secondary invasions by various introduction vectors including ballast water transport. Although non‐native R. venosa populations currently appear to be thriving in their new environments, the lack of genetic variability raises questions regarding the evolutionary persistence of these populations.     

XET-related genes and growth kinematics in barley leaves

DV, displacement velocity
GA₃, gibberellic acid
REGR, relative elemental growth rate
XET, xyloglucan-endotransglycosylase

Recently Schünmann et al. (1997 ; Plant, Cell and Environment 20, 1439–1450) investigated the correlation of spatial patterns of xyloglucan-endotransglycosylase (XET) activity, XET-related mRNAs, and growth in elongating barley ( Hordeum vulgare L.) leaves. Here, methodological difficulties in the kinematic growth analysis are discussed, and it is concluded that the role that XET-related gene activity plays in the control of spatial growth patterns remains undetermined.     

Discrimination of walleye, Stizostedion vitreum vitreum (Mitchill), stocks by isozyme analysis with cellulose acetate

Summary. Five walleye, Stizosfedion vitreum vitreum (Mitchill), populations from within the state of Minnesota were examined for isozyme gene frequencies. Of 26 loci identified and scored, nine polymorphic loci were found. The ADH*, MDH-3* and PROT-4* loci were found to be the most informative for distinguishing the populations. A north-south cline in the frequency of PROT-4* alleles was found, with a higher frequency of the fast allele being found in the southern population. This is probably a reflection of genetic isolation caused by glaciation. Cellulose acetate was used to resolve the isozymes. The advantages of cellulose acetate over starch in terms of decreased run time, smaller sample and stain volumes and superior resolution advocate the use of cellulose acetate for fish isozyme analyses. Comparisons between starch and cellulose acetate separations showed similar results with some exceptions. Cellulose acetate resolved FH* and PROT-2* polymorphisms that were not resolved on starch, but failed to resolve the MDH-1 locus. These differences did not affect the results.