Tree species composition of hardwood forests of the northeastern United States corresponds with soil chemistry, and differential performance along soil calcium (Ca) gradients has been proposed as a mechanism for enforcing this fidelity of species to site. We conducted studies in a southern New England forest to test if surface-soil Ca is more important than other factors in determining survival of seedlings of six common canopy tree species. Our hypothesis was that the calcicole species Acer saccharum and Fraxinus americana would show elevated survival rates at higher Ca levels, and that the calcifuge species A. rubrum, Fagus grandifolia, Quercus rubra, and Tsuga canadensis would show lower survival at high Ca. Other factors examined were 1) exchangeable magnesium (Mg), potassium (K), and aluminum (Al); 2) understory light availability; and 3) identity of overstory tree species. In one study, seedlings were transplanted into plots fertilized with Ca or Mg sulfate and survival was measured over 2 years. In the other study, 1-year or 2-year survival of naturally established seedlings in stands dominated by mature trees of one of the six study species was followed. Fertilization with Ca or Mg did not affect survival of planted seedlings, but ambient exchangeable Al was strongly negatively correlated with survival of F. americana. Of the three species with sufficient naturally established seedlings, exchangeable Al plus a proxy for light (overstory tree identity) were the most important determinants of survival. Survival of A. saccharum declined and A. rubrum and F. grandifolia increased at higher levels of exchangeable Al. This pattern is consistent with the positions of these species along the soil gradient. We conclude that soil chemistry effects on seedling survival play a role in establishing the soil relationships characteristic of these species as adults, but that Al is more important than Ca in establishing these effects during the seedling stage.

To determine whether Eleocharis tuberculosa var. pubnicoensis should be treated as a variety or as a form, herbarium material from throughout eastern North America and plants in southern Nova Scotian populations were examined. The variety pubnicoensis with smooth achene bristles was found to be confined to Great Pubnico Lake in Yarmouth County, southwestern Nova Scotia. Correlation analysis of population samples from 4 of 5 Nova Scotian lakes suggested that 4 of 5 characters associated with smooth bristles are actually a consequence of immaturity of fruiting spikes, and the remaining character is not significantly correlated. Discriminant analysis using the same characters of the same populations indicated that groupings based on bristle type were less significant and had higher misclassification rates than those based on spike maturity (based on disarticulation) and water depth. Due to a lack of confidence in a genetically based ecological and geographic integrity and a single morphological character, it seems most appropriate to treat pubnicoensis as a form.

Random Amplified Polymorphic DNA (RAPD) markers were used to determine whether populations of the global rarity Scirpus longii (Long's bulrush) are vulnerable to loss by introgression of genetic material from the weedy S. cyperinus (woolgrass). Shoots from 104 Scirpus plants were obtained from 10 sites in the watershed of the lower Medway River in Nova Scotia, Canada. A putative site of introgression (a seasonally flooded bog) was divided into five subsites: one large stand of vegetative plants and four patches of annually flowering plants clustered at one end of the site. Thirty-five dominant DNA markers were found among individuals from all sites and eight species-specific markers were identified for each of the two species. Nineteen different combinations of species-specific markers were present in the 39 individuals from the site of introgression, and, as expected for introgression, there was strong correlation (r  =  −0.80, p < 0.0001) between the numbers of the two types of markers. The vegetative and flowering subsites had distinctive hybrid indices: 0.76 and 0.27 of S. longii genome, respectively. The former indicates that S. cyperinus contributed about one-quarter of the genetic material of the plants from the subsite that accounts for more than 99% of the Scirpus at the site of introgression. Hybrid indices also show evidence of introgression in two of the 12 plants obtained at one of the presumed S. longii sites. Our results indicate that gene flow has occurred between S. cyperinus and S. longii at two S. longii populations, hybrid plants are capable of sexual reproduction, and Long's bulrush in Nova Scotia is vulnerable to loss by introgression. Conservation at the landscape level is needed to suppress anthropogenic disturbances that might allow S. cyperinus to threaten the genetic integrity of S. longii.

Seed coat morphology is examined in 16 taxa of Gentianopsis, Pterygocalyx, and Gentianella, including representatives from 14 taxa of Gentianopsis, to resolve inconsistencies in previous reports and make new observations using a low vacuum mode of SEM. Four characters are proposed to describe variation in seed coat morphology of this group: (1) the outer periclinal walls of testa; (2) sculpting of inner periclinal walls; (3) seed shape; and (4) seed length. The distinctive papillate seeds of many species of Gentianopsis are the result of inflated outer periclinal walls of testa cells. In some species, the outer periclinal walls of the testa are collapsed inwards, revealing previously unreported sculpting on the inner periclinal walls. Seeds are irregularly angular-ovate or fusiform in Gentianopsis and discoid in Pterygocalyx. Seed length varies from 0.22 to 1.0 mm. These data provide another line of evidence for phylogenetic relationships of Gentianopsis and Pterygocalyx to other members of Swertiinae, and illuminate the affinities of fossil seeds from New England that have been assigned to Gentianopsis.