The influence of substrate lithology on the distribution of many vascular and nonvascular plants has long been recognized, especially in alpine, subalpine, and other rocky habitats. In particular, plants have been classified as dependent on high-calcium substrates (i.e., calcicoles) based on common restriction to habitats developed in calcareous rocks, such as limestone and marble. In a classic 1907 paper on the influence of substrate on plants, M. L. Fernald singled out a particular meadow on Mont de la Table in the Chic-Choc Mountains of Québec for its unusual co-occurrence of strict calcicole and calcifuge (i.e., acidophile) plant taxa. We re-located this site, investigated substrate factors responsible for its unusual plant diversity, and documented current plant distributions. No calcareous rocks were found on site. However, inclusions of calcareous rocks were found farther up the mountain. The highest pH and dissolved calcium concentrations in surface waters were found in a series of springs that deliver groundwater, presumably influenced by calcareous rocks up the slope. Within the habitat delineated by common occurrences of calcicole species, available soil calcium varied by a factor of five and soil pH varied by almost 1.5 units, depending on microtopography and relative connection with groundwater. Variation in hydrologic delivery of weathering products leads to large variation in chemical composition of soils and waters within calcareous-influenced habitats. Here, the fine-scale variability of habitat, rather than plasticity in the plants' tolerances, appeared to be responsible for co-occurrence of taxa considered to be strict calcicoles or calcifuges. The flora in 2005–2008 was very similar to what it was in 1906, although in-filling of woody vegetation and strong chemical gradients driven by climatically controlled hydrologic processes suggest the possibility of future vegetation changes with continued climate change.

Polyploids are thought to harbor more genetic diversity than diploids, despite the genetic bottleneck they experience upon formation. Identifying the means by which polyploids become more genetically variable can advance our understanding of the evolutionary trajectories of polyploid lineages. Gene flow is one such mechanism that can contribute to polyploid genetic diversity. Here, we used microsatellite markers to measure genetic diversity and to estimate gene flow among closely related diploid and tetraploid species of the North American plant genus Houstonia section Amphiotis. We found that tetraploid populations were more genetically variable when compared to diploid populations and that gene flow (admixture) occurred more often among tetraploid populations than among diploids. In addition, we provide evidence to support previous reports that autopolyploidy is the likely mode of polyploid formation in this group. We suggest that gene flow among closely related species, particularly among tetraploid populations, has likely contributed to the genetic diversity levels of tetraploid lineages of Houstonia species.

Recent studies of the New England flora have evaluated changes within specific geographies over a relatively long period, typically a time interval of a century or more. Here, I document floristic changes in a suburban Massachusetts location, Massachusetts Audubon Society's Broadmoor Wildlife Sanctuary, by comparing plant records from 1969 to 1980 with a survey conducted in 2008–2009. The 2008–2009 survey found a relatively high total species richness (499 species) on the 246 ha property, but lower than the 562 species reported from 1969 to 1980. A total of 177 species were not refound (31% of the original flora), and 114 species (22% of the 2009 flora) were added. With the exception of four deliberately introduced grasses and five invasive species, the additions were long-lived perennial species likely to have been present but overlooked in the prior survey. The loss of species may be attributed to several factors, including natural succession following the abandonment of agriculture, deer browse, and changes in wetland hydrology caused by beavers.

Chromosome numbers are reported for the first time for 245 individuals of 93 taxa and cultivars and two hybrids from 13 genera from eastern Canada and the eastern United States. Nearly all of the reports are for asters in Symphyotrichum plus Doellingeria, Eurybia, Oclemena, and Sericocarpus, and for goldenrods in Solidago and Euthamia. Corrections or changes in identifications for eight previous reports are also listed. The following are first documented reports for the taxa: Chrysopsis highlandsensis, 2n  =  5_II from Florida; Solidago simulans, 2n  =  36 from North Carolina; Solidago villosicarpa, 2n  =  18 from North Carolina; Symphyotrichum fontinale, 2n  =  50 from Florida; Symphyotrichum grandiflorum, 2n  =  30 from North Carolina; Symphyotrichum parviceps, 2n  =  48 from Missouri; and Symphyotrichum rhiannon, 2n  =  48 from North Carolina. A number of the counts are first reports for a particular taxon in a state: e.g., Brintonia discoidea, 2n  =  18 from Alabama; Doellingeria umbellata var. umbellata, 2n  =  18 from Tennessee, Eurybia spectabilis, 2n  =  72 from South Carolina; Symphyotrichum oolentangiense, 2n  =  32 from Tennessee.