Small whorled pogonia, Isotria medeoloides, is a rare terrestrial orchid of temperate forests in eastern North America. It is federally threatened, and 1992 recovery criteria in place for this species need to be evaluated in light of current data. Study of I. medeoloides demography is complicated by the potential for belowground dormancy lasting one to three or more years. From 1986 to 2000, we observed 404 individuals in monitoring plots at four sites in Maine, USA, with up to 241 additional plants followed less intensively outside those plots. We used a life cycle diagram to summarize stage distribution data regarding emergence, recruitment, fruiting, and dormancy. A frequency analysis of the stage dynamics of individuals revealed no consistent patterns. Within plots, 17.9% of individuals bore fruits. Of plants that flowered, mean fruit set overall was 55%. Plant abundance within plots declined over time, possibly due to increasing shade and weather-related effects. In 1993, we removed 33% of the tree basal area over subsections of the populations at two sites while also leaving a portion of both sites untreated. We used mixed-effect regressions to test for increased recruitment and rate of capsule production as a result of the canopy treatment. As of 1993, for 187 plants in the treated zones mean capsule production per flowering plant did not decline, while it did decline in the untreated zones. In a subset of 100 paired plants matched by year and site, 95.8% of those impacted by severe herbivory were dead within 4 years, compared to 58% of counterparts with no herbivory. We used these data to evaluate the recovery criteria and recommend a change from a focus on percent flowering to a minimum of at least two capsules produced per year on average over a ten-year period.

What are the ecological consequences of allopolyploid speciation in ferns? In northeastern North America, this question is relevant to the Adiantum pedatum complex. Adiantum viridimontanum (Green Mountain maidenhair fern) is an allotetraploid hybrid derived from a sterile cross between the serpentine-restricted diploid species A. aleuticum (Aleutian maidenhair fern) and the rich-woods diploid species A. pedatum (northern maidenhair fern). In this study, we characterized the ecological niche of the allotetraploid hybrid maidenhair fern relative to the niches of its two progenitors by establishing 48 survey plots at 13 sites where the three species occur in Vermont and by measuring a set of ecological attributes in each plot, including the habitat type, light availability, topography, substrate characteristics, and soil chemistry. These data were analyzed using principal component analysis (PCA) to characterize the multivariate ecological niche of each species as circumscribed by the position of survey plots in environmental space. Along the first principal component, the ecological niche of the allotetraploid was situated between those of its progenitors in environmental space, closely overlapping the niche of A. aleuticum and slightly overlapping that of A. pedatum. Along the second principal component, a portion of the ecological niche of the allotetraploid was transgressive relative to the niches of its progenitors in environmental space; in geographic space, these survey plots correspond to northern hardwood serpentine-influenced forests, a habitat type that is novel for the species complex. Thus, the ecological outcome of allopolyploid speciation in the A. pedatum complex appears to include elements of both niche intermediacy and niche expansion into novel habitats.