Redonda-Martínez, R., J. L. Villaseñor, and T. Terrazas (Instituto de Biología, Universidad Nacional Autónoma de México, Departamento de Botánica, Apartado postal 70-367, 04510 México, D.F.). Trichome diversity in the Vernonieae (Asteraceae) of Mexico I: Vernonanthura and Vernonia (Vernoniinae). J. Torrey Bot. Soc. 139: 235–247. 2012.—Trichomes on the leaves and florets of 17 Mexican species of Vernonanthura and Vernonia (Tribe Vernonieae, subtribe Vernoniinae) were studied using light and scanning electron microscopy (SEM), to assess their taxonomic value in distinguishing between these two genera. Earlier studies of North American Vernonieae by Jones and colleagues (Faust and Jones 1973, King and Jones 1975) showed that trichome morphology and their presence on leaves and reproductive structures could be taxonomically informative, but this work included few Mexican taxa. Glandular and nonglandular trichomes, each with several variants, were found in the two genera. Glandular trichomes were particularly abundant on the florets and the achenes while the nonglandular were more common on the leaves. A cluster analysis shows two main species groups based on trichome traits. The first group linked species lacking glandular trichomes in vegetative or reproductive organs, whereas in the second the species were grouped by the occurrence of uniseriate and glandular trichomes. Within this second group, two species possess unique features: Vernonanthura cordata has long uniseriate subtype b₂ trichomes while in Vernonia greggii there are T-shaped trichomes on the leaf abaxial surface. Our results also showed that trichomes were useful in differentiating species with similar ecological and/or geographical features (e. g., Vernonia larsenii and V. lindheimeri), but were of limited taxonomic value at the generic level in distinguishing Vernonanthura from Vernonia. These two genera share various trichome types, but L-shaped trichomes were only found in Vernonanthura. An ongoing study of the Mexican Vernonieae may reveal informative trichome characters at different taxonomic levels, such as among subtribes, or between species of other more distantly related genera.

Ramírez-Morillo, I. M., G. Carnevali-F. C., J. P. Pinzón-Esquivel, J. L. Tapia-Muñoz, and C. F. Jiménez-Nah (Herbario CICY, Centro de Investigación Científica de Yucatán, A.C. (CICY). Calle 43 No. 130, Colonia Chuburná de Hidalgo, C. P. 97200, Mérida, Yucatán, México). Recircumscription and epitypification of Hechtia schottii Baker and H. stenopetala Klotzsch (Hechtioideae: Bromeliaceae). J. Torrey Bot. Soc. 139: 248-259. 2012.—Epitypes are designated for the Mexican species Hechtia schottii and Hechtia stenopetala. Complete descriptions of the two taxa are presented as well as specimen citations and iconography depicting relevant characteristics of the species and plants in habitat. The first species, known only from the States of Campeche and Yucatán, was based upon pistillate material (old fruits and immature pistillate buds) and leaf fragments; the epitype adds the staminate flowers and complete leaves. The second species, restricted to the Veracruz State, was based upon a plant with old, open fruits; the epitype adds the staminate flowers and leaves.

Arceo-Gómez, G. (Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Ave., Pittsburgh, PA, USA), M. L. Martínez (Red de Ecología Funcional, Instituto de Ecología A. C. carretera antigua a Coatepec N° 351 El Haya, Xalapa Veracruz, México C.P. 91070), V. Parra-Tabla (Departamento de Ecología Tropical, Campus de Ciencias Biológicas y Agropecuarias, Universidad Autónoma de Yucatán, Km. 15.5 carretera Mérida-Xmatkuil, Mérida, Yucatán, México), and J. G. García-Franco (Red de Ecología Funcional, Instituto de Ecología A. C. carretera antigua a Coatepec N° 351 El Haya, Xalapa Veracruz, México C.P. 91070). Floral and reproductive biology of the Mexican endemic Chamaecrista chamaecristoides (Fabaceae). J. Torrey Bot. Soc. 139: 260–269. 2012.—Chamaecrista chamaecristoides is an enantiostylous shrub endemic to the coast of Mexico that is being heavily impacted by human activities along the Gulf of Mexico. Chamaecrista chamaecristoides is considered a key species of the sand dune communities, particularly for its role as a nurse species and in dune stabilization. While certain aspects of its population biology have been well studied, others, such as its reproductive biology, have been overlooked. Understanding the factors that contribute to the successful reproduction of this species is crucial for its maintenance in natural populations. In this study, we examine the floral and reproductive biology of C. chamaecristoides. Specifically, we evaluate flower morphology and phenology, the breeding system and the identity and foraging patterns of floral visitors. Our results show that flower morphs are morphologically identical; however, position, size, and pollen production vary between stamens within each flower, suggesting functional differentiation. Furthermore, plants differ in their proportion of right- and left-styled flowers over the flowering season. While this could promote cross-fertilization by favoring pollen transfer among individuals with opposite floral-morph ratios, the presence of a stamen adjacent to the style, its self-compatibility and the absence of inbreeding depression all compromise the role of enantiostyly as an outcrossing strategy in this species. Finally, even though flowers are visited by at least ten different floral visitors, reproduction of C. chamaecristoides depends heavily on only three species that together account for more than 70% of the total number of visits. Overall, our results suggest that C. chamaecristoides is highly dependent on a small subset of the community of floral visitors and that it has evolved floral strategies to reduce pollen loss and enhance the efficiency of pollen transfer. For these reasons, future conservation strategies must also consider the preservation of suitable habitat for the somewhat limited pollinator community of this species.

Goldblum, D. and M. C. Kwit (Department of Geography, Northern Illinois University, DeKalb, IL 60115). The relative photosynthetic contribution of old and new fronds of the wintergreen fern Dryopteris carthusiana, Ontario, Canada. J. Torrey Bot. Soc. 139: 270–282. 2012.—A number of understory species in temperate and boreal forests are characterized by the wintergreen habit which entails retaining leaves for a portion of a second growing season. Several hypotheses have been offered to account for this trait, most commonly: old leaves serve as storage organs for nutrients required for spring growth or old leaves contribute to the overall carbon gain of the plant given their presence in the understory during the period of high radiation prior to canopy leafout. In this study, using field-derived light response curves, plant demographic data, leaf phenological data, and twice-hourly understory light levels, we model the relative contributions of old and new fronds to overall seasonal net carbon gain of a common fern, Dryopteris carthusiana, in a boreal and deciduous forest in Ontario, Canada. Approximately 43% of the total fern carbon gain in the deciduous forest occurs in the 40 days before canopy closure, compared to 46% in the boreal forest during the same period. In the deciduous forest, approximately 30% of the total fern net carbon assimilation occurs at the end of the growing season following overstory leaf fall, which was not the case in the boreal forest. Old fronds contribute 29% of overall carbon gain in the deciduous forest, but substantially more (63%) in the boreal forest. We estimate the total net carbon assimilation by D. carthusiana ferns in the deciduous forest at 90.7 kg C ha⁻¹ for the growing season and 45.5 kg C ha⁻¹ in the boreal forest. Our findings quantify the importance of the wintergreen habit for overall fern seasonal carbon gain, as well as the importance of early season high light conditions for understory plants in deciduous forests.

Gilland, K. E. (Department of Environmental and Plant Biology, Ohio University, Athens OH 45701), C. H. Keiffer (Department of Botany, Miami University, Oxford OH 45042), and B. C. McCarthy (Department of Environmental and Plant Biology, Ohio University, Athens OH 45701). Seed production of mature forest-grown American chestnut (Castanea dentata (Marsh.) Borkh). J. Torrey Bot. Soc. 139: 283–289. 2012.—Few records concerning pre-blight seed production of forest grown American chestnut (Castanea dentata) exist. As blight resistant American chestnut becomes available to use in restoration efforts, many conservation groups are interested in reintroducing the species as a wildlife food resource. As part of a long-term ecological study involving a disjunct population of American chestnut in Wisconsin, we examined seed production of mature forest grown trees in fall 2005 and 2006. Eleven large diameter (> 23 cm DBH), overstory position, fruiting American chestnuts were selected and measured for height, crown spread, crown volume, and dbh. Because seed predation is intense on this species, we indirectly measured seed production by counting the large opened and spiny cupules (i.e., burs) beneath the tree canopy, along with any cupules remaining on the tree. Castanea dentata typically produces three seeds per cupule, allowing for a reasonably accurate estimate of seed production, and cupules are rarely moved by seed predators. One half of the total projected canopy area was sampled plus an additional meter beyond the canopy edge. This method requires no estimation for losses due to predation or trap damage as found in traditional seed trap experiments. Mean seed production per m² of basal area was 69,489 in 2005 and 74,825 in 2006. A significant relationship between total number of seeds produced and DBH was found in 2005 but not in 2006. Using basal area measurements from the stand, we would expect 1.04×10⁶ seeds produced per hectare with 2758.5 kg ha⁻¹ of mast production. Based on a sample of seeds we were able to collect from the forest floor, mean seed weight was 2.65 g (± 0.039 SE). Overall, the results indicate that the decline of American chestnut after infection by the chestnut blight likely had a very significant impact on the availability of important wildlife food resources in stands where the species was dominant.

Peroni, P. A. (Department of Biology, Box 7118, Davidson College, NC 28035). Spatial environmental variation affects seed survival and germination in artificial seed banks in a Silene latifolia (Caryophyllaceae) metapopulation. J. Torrey Bot. Soc. 139: 290-298. 2012.—This study was conducted to determine the effects of time and spatial environmental heterogeneity on the survival and germination of artificial Silene latifolia (Caryophyllaceae) seed banks. Replicate packets of Silene latifolia seeds were buried at depths of 5 cm at five randomly selected locations at each of two sites located within a southwestern Virginia metapopulation. Samples of seeds from each site and location within site were exhumed periodically over a 3.5 yr period and examined for germination during burial. Seeds that had remained intact during burial were placed into growth chamber germination trials. Thirty-six to 59% of seeds remained intact (i.e., not germinated) and viable at the end of the 3.5 yr period. Germination during burial represented the primary avenue of loss from the seed bank and varied significantly among locations within sites for the 2.5 and 3.5 yr exhumations, and between sites at the 3.5 yr exhumation. The results suggest that appreciable proportions of buried Silene latifolia seeds are able to remain intact, but viable in the study environments over a 3.5 yr period. Germination during burial accounted for most losses from the seed bank, and varied significantly among locations within sites, which suggests that the ability of Silene latifolia seed banks in this metapopulation to serve as demographic buffers for local populations may be highly dependent on local environmental factors. Spatial environmental variation in seed bank persistence could contribute to the development or maintenance of genetic structuring within both local populations and the metapopulation.

Riege, D. A. (University of Maryland University College, 17 Longmeadow Ave., Middletown, RI 02842). Surge in regeneration of Pinus strobus L. in three Wisconsin forests not projected by past demography. J. Torrey Bot. Soc. 139: 299-310. 2012.—Long-term studies of forests are needed to verify theoretical patterns of succession. I investigated three mature pine (Pinus strobus L. and P. resinosa Ait.) forests in northern Wisconsin with compositional records that date back to the 1940s, with particular emphasis on replication of data that I collected in the 1970s. In successional trends from the 1940s to the 1970s, hardwood reproduction generally exceeded that of pine. However, in 2006–2007 the stands showed a surge in regeneration of P. strobus that was not predicted from the past data or common ideas on succession, resulting in bimodal size-class distributions. I suggest a dynamic in which self thinning of mid-successional hardwoods might allow P. strobus regeneration. In another uncommon pattern, Quercus rubra has gained in dominance over Acer saccharum in most parts of a hardwood-dominated section of one forest. Future monitoring will show if the recent resurgence of P. strobus reproduction represents a major shift in the late-successional patterns of these forests.

Wyckoff, P. H., R. Greiman, A. Krueger, and L. Luce. (Biology Discipline, University of Minnesota, Morris, MN 56267). Forest dynamics at Minnesota's prairie-forest border driven by invasive buckthorn (Rhamnus cathartica) and native bur oak (Quercus macrocarpa). J. Torrey Bot. Soc. 139: 311–322. 2012.—Quercus macrocarpa Michx. (bur oak) is the key pioneer species as forests establish at the prairie-forest ecotone in western Minnesota, but invasive Rhamnus cathartica L. (European buckthorn) is an abundant and increasing secondary tree. Here we contrast microsite utilization and growth as a function of light and soil moisture for Q. macrocarpa and R. cathartica saplings at an ecotonal forest in an effort to establish the roles these two species are likely to play in near-term forest dynamics. Compared to Q. macrocarpa, R. cathartica saplings are found, on average, in darker microsites (P < 0.001) with higher soil moisture (P < 0.001), though the range of light levels at which saplings were seen to occur is much larger for Q. macrocarpa than for R. cathartica. We fit a variety of models which predict sapling growth and compared fits using AICc. With our best fitting models, light, size, and soil moisture together explain approximately half of the variation in growth among R. cathartica saplings and two-thirds of the variation in Q. macrocarpa. Most similar studies utilize models that include an a priori assumption that growth will asymptote with increasing light availability, but we find no evidence to support the use of asymptotic models. All top ranked models include light and sapling size, but the calculated importance of both light and soil moisture is dependent on the choice of growth metric, a disturbing finding given the variety of metrics utilized in the sapling growth literature. For neither species does the addition of soil moisture significantly improve growth models if the growth metric used is absolute radial stem growth increment, but soil moisture becomes important when absolute basal area increment is the growth metric for Q. macrocarpa, and when relative growth increment is used for either species. Limited success of R. cathartica in light, dry microsites suggests that the invasive tree may be near its climatic limit at our ecotonal forest site. At the same time, the relative success of the species in the dark understory of our warm dry forest suggests that near-term warming, with an expected increase in continental-climate drought, is unlikely to limit R. cathartica across the bulk of forests it has invaded in North America.

Harris, T. B. (WRA, Inc., 2169-G East Francisco Boulevard, San Rafael, CA 94901), N. Rajakaruna (College of the Atlantic, 105 Eden Street, Bar Harbor, ME 04069), S. J. Nelson (Senator George J. Mitchell Center for Environmental and Watershed Research and Department of Plant, Soil and Environmental Sciences, University of Maine, 5710 Norman Smith Hall, Orono, ME 04469), and P. D. Vaux (Senator George J. Mitchell Center for Environmental and Watershed Research, University of Maine, 5710 Norman Smith Hall, Orono, ME 04469). Stressors and threats to the flora of Acadia National Park, Maine: Current knowledge, information gaps, and future directions. J. Torrey Bot. Soc. 139: 323–344. 2012.— Acadia National Park is a center of plant diversity in northeastern North America. The Park's varied habitats and flora are sensitive to a number of natural and anthropogenic perturbations. Stressors such as invasive plants, pest and pathogens, ozone, acidic fog and sulfur deposition, nitrogen deposition, heavy metals, fire and fire suppression, over-browsing, visitor use, hurricanes, and climate change have all had effects on the Park's habitats and plant species at some point and it is unclear how many of these stressors are currently affecting the flora of Acadia National Park. We discuss the botanical diversity of Acadia, assess the natural and anthropogenic stressors and threats affecting the Park's flora, and summarize critical information gaps to better assess the known stressors and threats to the flora. Understanding these stressors and threats is critical to making informed management decisions to preserve the botanical diversity of Acadia and other regional parks.

Medeiros D., L. Senna-Valle, and R. J. V. Alves (Universidade Federal do Rio de Janeiro, Museu Nacional, Department of Botany, Quinta da Boa Vista s.n., Bairro Imperial de São Cristóvão, Rio de Janeiro, 20.940-040, Brazil). Validation of the names Croton lenheirensis and Croton pradensis (Euphorbiaceae). J. Torrey Bot. Soc. 139: 345–346. 2012.— The species Croton lenheirensis D. Medeiros, Senna-Valle & Alves and Croton pradensis D. Medeiros, Senna-Valle & Alves from Brazil were published invalidly in 2009, not specifically designating in which herbarium the respective holotypes were deposited. This oversight is corrected with the validation of the specific names; the holotypes are deposited in R.