Genetic Population Structure and Accuracy of Morphological Assessment in Alosa aestivalis (Blueback Herring) and A. pseudoharengus (Alewife)

Alosa aestivalis and A. pseudoharengus are herring congeners that are important forage species for piscivorous fish and birds. We measured population structure metrics for these species using microsatellite markers. The Southern Gulf of Maine study area allowed the assessment of these species at an inter- and intra-watershed level. We found no detectable population structure within or among watershed for either species which agrees with other recent research. Our results support regional-scale (e.g., Gulf of Maine) plans for management for A. aestivalis and A. pseudoharengus. We found that 5.4% of our samples were hybrids. Our study adds to a growing body of evidence that hybridization and introgression should be management concerns for these species, and precautions should be taken to preserve species barriers. An error rate of morphological identification was calculated by comparing morphological identifications against genetic classifications. We found an overall identification error rate of 16%, which differed significantly from zero (P = 0.008). Managers should also take note of the uncertainty in morphological identifications and adjust stock models and policies accordingly

Responses of stomatal features and photosynthesis to porewater N enrichment and elevated atmospheric CO2 in Phragmites australis, the common reed

PREMISE Biological invasions increasingly threaten native biodiversity and ecosystem services. One notable example is the common reed, Phragmites australis, which aggressively invades North American salt marshes. Elevated atmospheric CO2 and nitrogen pollution enhance its growth and facilitate invasion because P. australis responds more strongly to these enrichments than do native species. We investigated how modifications to stomatal features contribute to strong photosynthetic responses to CO2 and nitrogen enrichment in P. australis by evaluating stomatal shifts under experimental conditions and relating them to maximal stomatal conductance (g(wmax)) and photosynthetic rates.METHODS Plants were grown in situ in open-top chambers under ambient and elevated atmospheric CO2 (eCO(2)) and porewater nitrogen (N-enr) in a Chesapeake Bay tidal marsh. We measured light-saturated carbon assimilation rates (A(sat)) and stomatal characteristics, from which we calculated g(wmax) and determined whether CO2 and N-enr altered the relationship between g(wmax) and A(sat).RESULTS eCO(2) and N-enr enhanced both g(wmax) and A(sat), but to differing degrees; g(wmax) was more strongly influenced by N-enr through increases in stomatal density while A(sat) was more strongly stimulated by eCO(2). There was a positive relationship between g(wmax) and A(sat) that was not modified by eCO(2) or N-enr, individually or in combination.CONCLUSIONS Changes in stomatal features co-occur with previously described responses of P. australis to eCO(2) and N-enr. Complementary responses of stomatal length and density to these global change factors may facilitate greater stomatal conductance and carbon gain, contributing to the invasiveness of the introduced lineage

Isolation of nine microsatellite loci in Dolichogenidea homoeosomae (Hymenoptera) a parasitoid of the sunflower moth Homoeosoma electellum (Lepidoptera)

Nine microsatellite loci were isolated from the insect Dolichogenidea homoeosomae (Hymenoptera: Braconidae), an important parasitoid of the sunflower moth Homosoeosoma electellum (Lepidoptera: Pyralidae), and assayed for polymorphism. All nine loci were polymorphic within the five populations tested, with two to 14 alleles per locus. Expected and observed heterozygosities ranged from 0.39 to 0.90 and 0.25 to 0.72 respectively. These are the first microsatellite primers developed for D. homeosomae and will be useful for studies of population dynamics and connectivity. © 2006 Blackwell Publishing Ltd

Adjusting to global change through clonal growth and epigenetic variation

The earth is experiencing major changes in global and regional climates and changes are predicted to accelerate in the future. Many species will be under considerable pressure to evolve, to migrate, or be faced with extinction. Clonal plants would appear to be at a particular disadvantage due to their limited mobility and limited capacity for adaptation. However, they have outlived previous environmental shifts and clonal species have persisted for millenia. Clonal spread offers unique ecological advantages, such as resource sharing, risk sharing, and economies of scale among ramets within genotypes. We suggest that ecological attributes of clonal plants, in tandem with variation in gene regulation through epigenetic mechanisms that facilitate and optimize phenotype variation in response to environmental change may permit them to be well suited to projected conditions

Clonal Growth: Invasion or stability? A comparative study of clonal architecture and diversity in native and introduced lineages of Phragmites australis (Poaceae)

• Premise of the study: The characteristics of clonal growth that are advantageous in invasive plants can also result in native plants’ ability to resist invasion. In Maine, we compared the clonal architecture and diversity of an invasive lineage (introduced Phragmites ) and a noninvasive lineage (native Phragmites ) present in much of North America. This study is the first on stand-scale diversity using a sample size and systematic spatial-sampling scheme adequate for characterizing clonal structure in Phragmites. Our questions included: (1) Does the structure and extent of clonal growth suggest that the potential for clonal growth contributes to the invasiveness of the introduced lineage? (2) Is clonal growth common in the native lineage, acting as a possible source of ecological resistance and resilience? • Methods: Microsatellite markers were used to measure clonal sizes, architecture, and diversity within each lineage in stands within four marshes in Maine. • Key results: Clonal diversity measures indicated that clonal growth was significantly greater in stands of the native lineage than in the introduced. While lineage was a consistent predictor of clonal diversity relative ranking, the marsh location was a much stronger predictor of the absolute range of these values. • Conclusions: Our results indicate an important role for clonal growth in the space consolidation of native Phragmites and could explain why the introduced lineage, with stronger competitive traits, has not replaced the native where they co-occur. These results with regard to clone size, size distributions, singleton occurrence, and clonal architecture provide some evidence for stand development that follows a genotypic initial floristics model

Clonal Diversity in an Expanding Community of Arctic Salix spp. and a Model for Recruitment Modes of Arctic Plants

Abstract Rapid climate change in arctic environments is leading to a widespread expansion in woody deciduous shrub populations. However, little is known about the reproductive, dispersal, and establishment mechanisms associated with shrub expansion. It is assumed that harsh environmental conditions impose limitations on plant sexual reproduction in the Arctic, such that population survival and expansion is predominately a function of clonal recruitment. We present contrary evidence from microsatellite genetic data suggesting the prevalence of recruitment by seed. Further, we present a conceptual model describing modes of recruitment in relation to the abiotic environment. Climate change may be alleviating abiotic stress so that resources are available for more frequent recruitment by seed. Such changes have widespread implications for ecosystem structure and functioning, including species composition, wildlife habitat, biogeochemical cycling, and surface energy balance