Properties of allelic variants of phosphoglucomutase from the sea anemone Metridium senile

The phosphoglucomutase (Pgm) locus from populations of the sea anemone Metridium senile has three alleles in natural populations from the northeastern coast of North America. Two of the alleles exhibit clinal variation north of Cape Cod, suggesting a possible association of allele frequency with environmental temperature. This clinal pattern is reproducible and stable over at least brief periods of time. The allozymes encoded by each of the six Pgm genotypes have been partially purified and characterized. The symmetrical pH optimum for Vmax is pH 7.5; the apparent Km (Kmapp) of glucose-1-phosphate declines monotonically as the pH increases from 6.5 to 8.5. There are no pronounced differences in heat stabilities of PGM produced by various genotypes, nor are there significant differences in specific activities. There are no differences in the sensitivity of Vmax to temperature. Kmapp values are very low for all genotypes, ranging from about 2 to 12 microM, depending upon the temperature. Kmapp of glucose-1-phosphate declines as the temperature is raised for all genotypes, whether the pH is held constant or allowed to vary with the temperature. Under certain conditions, there are small significant differences among genotypes in Kappm values, but there is no systematic pattern to these differences. The present data provide no biochemical explanation for the maintenance of the Pgm cline by selection for functional differences under different thermal regimes.     

Assessment of the Cape Cod phylogeographic break using the bamboo worm Clymenella torquata reveals the role of regional water masses in dispersal

Previous genetic studies suggest Cape Cod, MA, as a phylogenetic break for benthic marine invertebrates; however, diffuse sampling in this area has hindered fine-scale determination of the break's location and underlying causes. Furthermore, some species exhibit breaks in different places, and others exhibit no breaks in this region. We analyze the phylogeographic patterns of 2 mitochondrial genes from 10 populations of the bamboo worm Clymenella torquata (Annelida: Maldanidae) focused around Cape Cod but extending from the Bay of Fundy, Canada, to New Jersey. A common invertebrate along the US coast, C. torquata, possesses life-history characteristics that should make it sensitive to factors such as dispersal barriers, bottlenecks, and founder events. As an inhabitant of soft sediments, C. torquata offers a unique contrast to existing research dominated by organisms dwelling on hard substrates. Our genetic data show a clear phylogenetic break and a cline of haplotype frequencies from north to south. Fine-scale sampling of populations on Cape Cod, combined with other sampled populations, confirm that this distinct break is not on the Cape Cod peninsula itself but to the south near a boundary of oceanic water masses. Low levels of gene flow occur in these populations, in an asymmetric manner congruent with coastal current patterns. No significant effect of Pleistocene glaciation was seen in the pattern of genetic diversity over the sampled range.     

Molluscan Community Recovery Following Partial Tidal Restoration of a New England Estuary, U.S.A.

Historic human-imposed tidal flow restrictions at many New England estuaries have resulted in dramatic alteration of estuarine community structure and function. East Harbor, a 291-ha coastal lagoon and salt marsh in Truro, Massachusetts, was artificially isolated from Cape Cod Bay in 1868. After the isolation, salinity decreased to near freshwater levels, and estuarine fish and invertebrate populations declined precipitously. Partial tidal flow was restored to East Harbor in 2002; since then, East Harbor has experienced substantial increases in salinity, and native fauna has begun to return to the system. The objective of this study was to obtain information on marine molluscan populations recolonizing East Harbor. Using a combination of benthic cores and direct searching, we surveyed 50 plots throughout the estuary in July and August 2005. We detected 16 molluscan species in East Harbor as a whole; the four most abundant species were Mya arenaria , Littorina spp., Mytilus edulis , and Mercenaria mercenaria . We found significant differences in species richness and abundance of these species among three regions of East Harbor that varied markedly in salinity and distance to Cape Cod Bay; diversity and abundance were both highest in Moon Pond, which has a direct connection with sources of seawater and marine biota, and lowest in the northwest cove, which receives high freshwater discharge. These findings demonstrate the effectiveness of Cape Cod National Seashore's preliminary tidal restoration efforts while underscoring the continued need for full tidal restoration at East Harbor and other tide-restricted estuaries.     

Evolutionary genetics of Metridium senile. II. Geographic patterns of allozyme variation

Electrophoretic surveys have demonstrated that populations of the sea anemone Metridium senile along the northeast coast of the United States are polymorphic at four enzyme loci. Phosphoglucose isomerase (PGI) has two alleles in most populations, phosphoglucomutase (PGM) has three alleles, and two leucine aminopeptidase loci have two common alleles each. Phosphoglucose isomerase displays clinal variation and an apparent association with environmental temperature. Phosphoglucomutase shows clinal variation north of Cape Cod for two of the three alleles, while the two leucine aminopeptidase loci are not clinal. All loci show a great deal of variation in populations on Cape Cod, but there is no apparent systematic pattern to this variation. Temperature may be a selective agent in the maintenance of the PGI and PGM clines, although other possibilities cannot presently be completely excluded.Supported by Grant T-4 from the Health Research and Services Foundation, NSF DEB77-14442, NIH GM25809, and NIH GM28024.     

INTRA- AND INTERCLONAL COMPETITION IN THE CLEISTOGAMOUS GRASS AMPHIBROMUS SCABRIVALVIS

The relationship of differences in life history traits among genotypes to competitive ability is not well known for most clonal plants. It has been hypothesized that genetically identical clones will compete more intensively than genetically distinct clones. The perennial grass Amphibromus scabrivalvis, which produces basal corms and cleistogamous seeds enclosed by leaf sheaths, exhibits pronounced clonal growth via rhizome and ramet production. In a controlled greenhouse experiment, clones of four genotypes of this species were grown under three regimes: alone in the absence of competition, paired with a clone of the same genotype (intraclonal competition), and paired with a clone of a different genotype (interclonal competition). There were differences in some biomass measures and in ramet and corm production among the four genotypes grown in the absence of competition. All genotypes showed a significant reduction in total biomass under both intra- and interclonal conditions, indicating that competition had occurred. For three of four genotypes, biomass allocation to corm increased under competition, while allocation to cleistogamous seeds was constant or increased slightly. Although some genotypes in specific interclonal combinations were less affected by competition than in intraclonal combinations, there was no support for the contention that the effects of competition were more intense for genetically identical clones.     

Effect of husk characters on resistance to corn earworm (Lepidoptera: Noctuidae) in high-maysin maize populations

Two maize (Zea mays L.) breeding populations with very high concentrations of maysin, a silk-expressed flavone glycoside, were tested for their ability to resist ear damage by the corn earworm, Helicoverpa zea Boddie, under field conditions. Tests were conducted in 2000 and 2001 at multiple locations in Georgia. The high maysin populations, EPM6 and SIM6, as well as resistant and susceptible checks, were scored for silk-maysin content, H. zea damage, and husk characters. In 2000, there was a negative correlation between husk tightness and earworm damage at three of five locations, while there was no significant correlation between damage and maysin content at any location. In 2001, EPM6 and SIM6 had approximately ten times the maysin content of the low-maysin control genotypes; nevertheless, earworm damage to EPM6 and SIM6 was either greater than or not significantly different from the low-maysin genotypes at all locations. The resistant control genotype, Zapalote Chico, had significantly less earworm damage than EPM6 and SIM6 for both years at all locations. The results of this study highlight the importance of identifying and quantifying husk and ear traits that are essential to H. zea resistance in maize.     

Biometrisch-genetische Untersuchungen an Klonen und Nachkommenschaften beiPhlox paniculata L.

Summary In clonus and progenies linear phenotypic and genotypic correlations and interactions between genotypes, years and locations as well as methods for the estimation of the heritability are investigated.The significant correlation coefficients found should facilitate selection for more than one character at one time. With one exception high genotypic correlations correspond to significant phenotypic ones (Table 1). Usually genotype/year and genotype/year/location-interactions were not significant, but genotype/location-interactions were regularly significant in trials carried over more than one season. There were also clear differences in the ability of genotypes to yield consistently in different locations over several seasons (ecovalence).Estimates of heritabilities both in the narrow sense and in the broad sense were relatively high, especially those of flowering date, plant height and leaf number. Both types of heritabilities showed the same ranking (Table 3). Half-sib families from polycrosses were not suitable for half-sib correlations.From the results obtained it has been concluded that one year trials with replicated clones in different locations yield useful estimates of heritability. Therefore, in breeding plants with long generation times, raising of progenies may be dispensed with in the interest of saving time.

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Angenommen durch W. Seyffert     

Use of the 16S-23S rDNA internal transcribed spacer of Roseovarius crassostreae for epizootiological studies of juvenile oyster disease (JOD)

Juvenile oyster disease (JOD) in Crassostrea virginica is caused by the marine bacterium Roseovarius crassostreae. Although the 16S rRNA genes of the bacterial isolates exhibit little variation, 2 genetic signatures (GSI and GSII) may be discerned by Ava I digestion of the 16S-23S internal transcribed spacer (ITS). In this study we analyzed isolates from JOD epizootics throughout the northeastern USA (including affected adults for the first time) to better understand how oyster populations encounter and become affected by the pathogen. Isolates from a given epizootic usually had the same ITS signature; however, the involvement of both genetic signatures was occasionally detected, even within the same oyster. Sequencing was used to localize the variable Ava I site to a 100 bp region of low sequence identity, and detection of additional base changes resulted in the identification of 11 distinct genotypes. One genotype was found only in Martha's Vineyard, Massachusetts, USA and persisted in JOD survivors. Two genotypes were associated with Maine epizootics, and both were believed to be unique to that region until 2004, when one was detected in Martha's Vineyard among oysters that had survived colonization by the local genotype. Apparent competition between those 2 genotypes was also detected among a population of juveniles. Five genotypes were found only in New York, and the other 3 were isolated from both New York and from around Cape Cod, Massachusetts. Relationships between the geographic occurrence and phylogenetic relatedness of genotypes were compared with regional current patterns to identify possible mechanisms controlling their distribution.     

Predator-mediated plasticity in morphology, life history, and behavior of Daphnia: the uncoupling of responses

We studied the way 12 traits responded to fish kairomones in a set of 16 Daphnia magna clones derived from four different habitats-two where daphnids co-occur with fish and two without fish. These clones differed widely in their response to predator kairomones, with none of the clones showing a significant response in all traits and all clones showing a response for at least one trait. Most of the clones showed a significant response in one to four traits, with no evidence for an association between different traits. Clones from fish habitats were slightly more responsive to the presence of fish kairomones than clones from fishless locations. We conclude that most clones show an induced response to the presence of their predators (fish) but that there is a large genetic variability with respect to the traits for which clones show a response. Our results indicate that the major distinction is not between inducible and noninducible genotypes but rather that the genotypes differ in the combination of traits for which they show inducible responses.     

THE ORIGIN AND DISTRIBUTION OF CLONAL DIVERSITY IN ALSOPHILA POMETARIA (LEPIDOPTERA: GEOMETRIDAE)

A survey of spatial and temporal variation in the frequency of electrophoretically defined genotypes in the geometrid moth Alsophila pometaria revealed a high diversity of uncommon or rare asexual genotypes and clinal distributions of two of the more common clones. There was substantial year-to-year variation in genotype frequencies in seven of eleven sites. Progeny tests have revealed that sexual reproduction is uncommon in two populations and that new asexual genotypes arise from the sexual population. The recurrent origin of asexual genotypes is likely to account for the high genetic and ecological diversity of the asexual contingent of this species' populations, in contrast to the lower genetic diversity in some obligately asexual species in which such recruitment does not occur.     

Genetic composition,genetic diversity,and small-scale environmental variation matter for the experimental reintroduction of a rare plant

Aims Reintroduction has become an important tool for the management of endangered plant species. We tested the little-explored effects of small-scale environmental variation, genotypic composition (i.e. identity of genotypes) and genotypic diversity on the population survival of the regionally rare clonal plant Ranunculus reptans. For this species of periodically inundated lakeshores, genetic differentiation had been reported between populations and between short-flooded and long-flooded microsites within populations.Methods We established 306 experimental test populations at a previously unoccupied lakeshore, comprising either monocultures of 32 genotypes, mixtures of genotypes within populations or mixtures of genotypes between populations. In 2000, three years after planting out at the experimental site, a long-lasting flood caused the death of half of the experimental populations. In 2003, an extreme drought resulted in the lowest summer water levels ever measured.Important findings Despite these climatic extremes, 27% of the established populations survived in December 2003. The success of experimental populations largely differed between microsites. Moreover, the success of genotype monocultures depended on genotype and source population. Genetic differentiation between microsites played a minor role for the success of reintroduction. After the flood, populations planted with genotypes from different source populations increased in abundance, whereas populations with genotypes from single source populations and genotype monocultures decreased. In 2014, several small patches of Ranunculus clones were still present, but plants were strongly intermingled, which precluded their assignment to the original treatments. We conclude that sources for reintroductions need to be selected carefully. Moreover, mixtures of plants from different populations appear to be the best choice for successful reintroduction, at least in unpredictably varying environments.     

THE DISTRIBUTION, ABUNDANCE AND SELECTED PREY OF THE HARBOR SEAL, PHOCA VITULINA CONCOLOR, IN SOUTHERN NEW ENGLAND

The seasonal distribution and abundance of harbor seals occurring south of Maine were documented by counting the number of seals at traditional haulout locations. The average number of seals counted during each survey in Massachusetts and New Hampshire was 3,560 ± 255 (95% CI), 1983–1987. The maximum number of seals counted on any individual survey was 4,736 individuals. Fifty percent of all the surveys since January 1985 have resulted in counts greater than 4,000 seals reflecting a 27% increase in the abundance of seals in our study area since that date. Seventy-five percent of the seals in southern New England are located at haulout sites on Cape Cod and Nantucket Island. The largest aggregation of seals in the eastern United States occurs mid-winter at Monomoy Island and adjacent shoals. A single high count of 1,672 seals occurred at this site during the study period. An additional 271–374 seals were also counted in Rhode Island, Connecticut and eastern Long Island Sound during surveys conducted in March 1986 and 1987. The American sandlance Ammodytes americanus was the single dominant prey item of harbor seals in waters adjacent to Cape Cod based on the modified frequency of occurrence of each prey species in scat samples collected from three haulout sites on Cape Cod between 1984–1987. During January and February sandlance was the near exclusive prey item at Monomoy (99%, n= 80). During March and April, the frequency of Atlantic herring Clupea harengus increased in the scat samples at this site. Regional differences in the diet of seals reflect distinct prey communities throughout the study area. Since 1986, the percent occurrence and importance of sandlance in the diet of seals has decreased, reflecting an overall decrease in abundance of this prey species in waters adjacent to Cape Cod. In spite of fluctuations in abundance, and regional differences in the diet of seals throughout the study area, sandlance still comprised a minimum 55% of the total prey species of harbor seals throughout the study area.     

Genotype and temperature influence pea aphid resistance to a fungal entomopathogen

Abstract. The influence of temperature on life history traits of four Acyrthosiphon pisum clones was investigated, together with their resistance to one genotype of the fungal entomopathogen Erynia neoaphidis . There was no difference among aphid clones in development rate, but they did differ in fecundity. Both development rate and fecundity were influenced by temperature, but all clones showed similar responses to the changes in temperature (i.e. the interaction term was nonsignificant). However, there were significant differences among clones in susceptibility to the pathogen, and this was influenced by temperature. Furthermore, the clones differed in how temperature influenced susceptibility, with susceptibility rankings changing with temperature. Two clones showed changes in susceptibility which mirrored changes in the in vitro vegetative growth rate of E. neoaphidis at different temperatures, whereas two other clones differed considerably from this expected response. Such interactions between genotype and temperature may help maintain heritable variation in aphid susceptibility to fungal pathogen attack and have implications for our understanding of disease dynamics in natural populations. This study also highlights the difficulties of drawing conclusions about the efficacy of a biological control agent when only a restricted range of pest genotypes or environmental conditions are considered.     

Genetic variation at the Pgi locus in the mosquito fish Gambusia affinis (Poecilidae) and a possible effect on susceptibility to an insecticide

Although some studies have been completed on genetic variation in relation to tolerance to heavy metals, none have considered pesticide pollution. This study examines the relationship between genotypes at the glucose phosphate isomerase ( Pgi ) locus in Gambusia and susceptibility to the organophosphate insecticide chlorpyrifos. Laboratory toxicity tests show significant differences in genotype frequencies between susceptible and tolerant groups offish from one site but not at others. A field survey examined genotype frequencies and levels of pesticide in the fish at seven sites. No chlorpyrifos was found at any of the sites, but a number of organochlorines were recorded. Significant correlations were found between three organochlorines (DDT/DDD, DDE and lindane) and frequences of particular genotypes. There were also significant differences in tolerance between populations and between size classes. These results are discussed in relation to previous work with heavy metals.     

The assessment of the tolerance of partially resistant potato clones to damage by the potato cyst nematode Globodera pallida at different sites and in different years

A range of potato cultivars and clones was grown at three sites infested with Globodera pallida in each of four years (1983 – 1986). Comparison of yields from nematicide treated plots with those of untreated plots provided estimates of yield losses due to G. pallida. The proportional yield losses were calculated for each genotype at each site as a measure of nematode tolerance. There were significant differences between genotypes with regard to tolerance of damage by G. pallida. There were also significant interactions between the different genotypes and the sites and years, but the interactions between years and genotypes represented only a small proportion of the observed variation. The interactions between sites and years indicate that not all of the genotypes behaved consistently between sites and years. The extent of yield losses caused by the nematodes varied significantly between sites. The implications of these results are discussed in relation to potato breeding programmes and assessing resistance and tolerance to G. pallida.     

Variation of Relative Growth Rate and Survival in Ecologically Contrasting Populations of Agrostis stolonifera

Abstract Significant differentiation in relative growth rate (RGR) was found among three ecologically contrasting populations of Agrostis stolonifera. Under low nitrogen conditions the sand dune population had the highest mean RGR. The plastic response in RGR to different levels of nitrogen supply was significantly higher in the inland meadow population than in the polder and sand dune populations. The (colonizing) polder population tended to have the highest variation for RGR. Variation in RGR within populations was mainly environmentally determined, although in the polder population significant effects of genotype and of genotype × nitrogen level were found. The repeatability for RGR in this population proved to be different from zero under both nitrogen conditions. Root/shoot ratios of the three populations were not different from each other, independent of the level of nitrogen supply. Correlations between RGR and survival of genotypes within the populations were not significant, which points at the influence of genotype × environment interactions or the possibility that genotypic differences in RGR do not necessarily indicate an adaptation to any habitat, not even the home site.     

Whitefly Bemisia tabaci (Homoptera: Aleyrodidae) infestation on cassava genotypes grown at different ecozones in Nigeria

Large-scale screening of cassava, Manihot esculenta Crantz, genotypes for resistance to infestation by whitefly Bemisia tabaci Gennadius, the vector of cassava mosaic geminiviruses, is limited. A range of new cassava elite clones were therefore assessed for the whitefly infestation in the 1999/2000 and 2000/2001 cropping seasons in experimental fields of International Institute of Tropical Agriculture, Ibadan, Nigeria. On each scoring day, between 0600 and 0800 hours when the whiteflies were relatively immobile, adult whitefly populations on the five topmost expanded leaves of cassava cultivars were counted. All through the 6-mo scoring period, there was a highly significant difference in whitefly infestation among the new cassava elite clones. Vector population buildup was observed in Ibadan (forest-savanna transition zone) and Onne (humid forest), 2 mo after planting (MAP). Mean infestation across cassava genotypes was significantly highest (16.6 whiteflies per plant) in Ibadan and lowest in Zaria (0.2). Generally, whitefly infestation was very low in all locations at 5 and 6 MAP. During this period, cassava genotypes 96/1439 and 91/02324 significantly supported higher infestations than other genotypes. Plants of 96/1089A and TMS 30572 supported the lowest whitefly infestation across cassava genotypes in all locations. The preferential whitefly visitation, the differences between locations in relation to whitefly population, cassava mosaic disease, and the fresh root yield of cassava genotypes are discussed.     

Diverse dengue type 2 virus populations contain recombinant and both parental viruses in a single mosquito host

Envelope (E) protein genes sampled from populations of dengue 2 (DEN-2) virus in individual Aedes aegypti mosquitoes and in serum from dengue patients were copied to cDNA, cloned, and sequenced. The nucleotide sequences of the E genes in more than 70% of the clones differed from the consensus sequence for the corresponding virus population at up to 11 sites, and 24 of the 94 clones contained at least one stop codon. Virus populations recovered up to 2 years apart yielded clones with similar polymorphisms in the E gene. For one mosquito, the clones obtained fell into two genotypes. One group of sequences was closely related to those of viruses recovered from dengue patients in the same locality (Yangon, Myanmar) since 1995 and were classified as Asian 1 genotype. The second group were Cosmopolitan genotype viruses which were also circulating in Yangon in 2000 and which were related to DEN-2 viruses sampled from southern China in 1999. Finally, one clone was identified as a recombinant genome composed of portions of these two "parental" genotypes. This is the first report of recombinant and parental dengue viruses in a single host.     

Invasion of the Red Seaweed Heterosiphonia japonica Spans Biogeographic Provinces in the Western North Atlantic Ocean

The recent invasion of the red alga Heterosiphonia japonica in the western North Atlantic Ocean has provided a unique opportunity to study invasion dynamics across a biogeographical barrier. Native to the western North Pacific Ocean, initial collections in 2007 and 2009 restricted the western North Atlantic range of this invader to Rhode Island, USA. However, through subtidal community surveys, we document the presence of Heterosiphonia in coastal waters from Maine to New York, USA, a distance of more than 700 km. This geographical distribution spans a well-known biogeographical barrier at Cape Cod, Massachusetts. Despite significant differences in subtidal community structure north and south of Cape Cod, Heterosiphonia was found at all but two sites surveyed in both biogeographic provinces, suggesting that this invader is capable of rapid expansion over broad geographic ranges. Across all sites surveyed, Heterosiphonia comprised 14% of the subtidal benthic community. However, average abundances of nearly 80% were found at some locations. As a drifting macrophyte, Heterosiphonia was found as intertidal wrack in abundances of up to 65% of the biomass washed up along beaches surveyed. Our surveys suggest that the high abundance of Heterosiphonia has already led to marked changes in subtidal community structure; we found significantly lower species richness in recipient communities with higher Heterosiphona abundances. Based on temperature and salinity tolerances of the European populations, we believe Heterosiphonia has the potential to invade and alter subtidal communities from Florida to Newfoundland in the western North Atlantic.