Reproductive ecology studies of rare species can provide information pertinent to population growth and persistence. One rare species confined to two disjunct localities, one on private land located in Florida and the other one that is composed of two subpopulations on public land in South Carolina, is the federally threatened Miccosukee gooseberry, Ribes echinellum. Studies were carried out in the Florida population to determine change in abundance between 1992 and 2012 and to understand the lack of seedling recruitment in the wild. In Florida, the number of patches increased in the northern part of the study area but decreased in the southern part. Hand pollination experiments indicate Ribes echinellum exhibits a mixed mating system. Although autogamous pollination occurred, it did not result in fruit production. Reduced seed set of selfed flowers and seedling size provided some support for inbreeding depression, yet small sample sizes precluded full evaluation. No asexual seed production was detected. Seeds persisted in the field less than one year, suggesting a transient seed bank. Although germination potential, estimated by staining seeds with tetrazolium, was 60%, in situ seed germination from fruits of manipulated and control flowers was only 25%. Seedling survival was zero, indicating high risk of extirpation. Either low spring precipitation during the years of this study or scarcity of compatible mates could explain the lack of seedling survival. These results are important for developing a conservation strategy for this species.

Long-term monitoring of the rare southern twayblade (Neottia bifolia; Orchidaceae) and understorey of a black spruce-tamarack, swamp community was conducted after construction of an airport taxiway above the swamp edge. Succession documented over 14 years in the treed swamp edge following disturbance involved loss of the twayblade, invasion by guilds of annuals, and shifts between original and new guilds of wetland plants. Despite changes, the twayblade was the only plant extirpated from the swamp edge community although fungal richness (mainly basidiomycete) was substantially lower in the edge than the swamp interior. NMS ordination indicated that the orchid niche is an undisturbed swamp with an intact tree canopy and unbroken mat of Sphagnum which supports a diverse mycorrhizal community adapted to summer water table drawdown and low ionic groundwater chemistry (e.g. Cl<10 mg/L). Fourteen years after the disturbance, southern twayblade populations in the swamp interior, 100 m from the edge were in steady decline. The woodland orchids may be sentinels of ecosystem integrity. Loss of the twayblade signalled the onset of a post-development, disturbance-cascade: installation of an impervious surface restricted infiltration, altered run-off quantity and quality which subsequently resulted in loss of the ecosystem engineer, Sphagnum, and keystone mycorrhizal fungi.

Ornamental plant species are frequently planted well outside of their native ranges and, in some cases, escape from cultivation to develop naturalized populations. Understanding the causes and consequences of naturalization resulting from intra-continental introductions will shed light both on mechanisms of invasion and on the potential for facilitated migration as a response to global climate change. In this study, we characterized a naturalized population of pin oak (Quercus palustris) that has recently arisen in the woodlands of Colby College in central Maine, 275 km from its native range limit. The population stemmed from trees in two small horticultural plantings, one from 1950 and one from the mid-1980′s. As an initial indication of potential invasiveness, we compared growth rates of individual pin oak trees to those of red oak (Quercus rubra), the most closely related native species and likely competitor. We also carried out genetic testing to determine how many parents gave rise to the naturalized population. Growth rates of pin oak saplings were only marginally greater than those of red oak saplings. Genetic analysis showed that at least 75% of sampled progeny descended from the six trees of the original 1950 population, with at least one-third of the progeny descending from two individual trees. Our results demonstrate that a small number of founders can be sufficient to establish a naturalized population beyond the native range limit. It is too soon to tell whether naturalized populations of pin oak in Maine will behave invasively, as might be expected with a trans-oceanic introduction, or will behave more similarly to populations at a naturally expanding range limit. There is no evidence to date that the naturalized pin oak population is detrimentally impacting the native forest community.

Red cedar woodlands on circumneutral outcrops are a rare type of natural community in New Hampshire (S1—Critically Imperiled) and across its global range (G3—Vulnerable). The most studied example in the state, first observed by New Hampshire Natural Heritage Bureau ecologists over 15 years ago, was surveyed and formally documented in 2016 and 2017 from three adjacent slopes of the ring-dike complex known as the Pawtuckaway Mountains in Nottingham and Deerfield, NH. Stand-age studies suggest the red cedar woodland may have existed as a stable community at this site for many centuries. Since examining this site in the Pawtuckaway Mountains, one other circumneutral red cedar rocky outcrop community with similar plant species composition and cover in a comparable physical setting has been documented in southern New Hampshire. Here, we newly describe the circumneutral red cedar rocky outcrop community in New Hampshire.