The morphology, histochemistry, and ultrastructural aspects of the secretion of Lavandula pinnata L. (Lamiaceae) glandular trichomes were studied in order to prepare for work on calcium distribution in normal and heat stressed plants. The secretory process was observed in both light and dark-grown plants. The secretion of the capitate glandular trichomes consists of both lipophilic and polysaccharidic substances (mainly the latter), while peltate glandular trichomes only secrete lipophilic substances. Our ultrastructural results are consistent with the finding that plastids are the main organelle that synthesizes the lipophilic substances, especially terpenes, while dictyosomes synthesize polysaccharides. The essential oil is most likely transported directly by the RER, while the polysaccharides reach the plasma membrane via Golgi-derived vesicles. Exocytosis is the main way that secretory products move from the cell to the subcuticular space. There are no differences in gland development or secretion between the light and dark-grown plants.

Two species of Manfreda Salisbury (Agavaceae) endemic to the Mexican Yucatan Peninsula are proposed as new. The new species, Manfreda paniculata L. Hernández, R. Orellana & Carnevali and M. petskinil R. Orellana, L. Hernández & Carnevali are characterized by the presence of long-lasting leaves, paniculate inflorescences, and flowers subtended by a single bracteole—the latter a unique character found within the family Agavaceae and probably within the order Asparagales. Manfreda paniculata is similar to M. sileri, differing from it by the presence of a stem, bulbils, leaves fleshier and more rigid, larger marginal teeth, with long flexible spine-like tip, pedicellated flowers, and shorter floral tube. Manfreda petskinil has been annotated in some herbaria as M. scabra, but the new species is similar to M. variegata, from which it differs by the presence of minutely pubescent and denticulate leaves, ascendant flowers, filament insertion at the mouth of the tube, and a thin style. However, both new species are most closely related to each other than any other species in the genus. Manfreda petskinil is acaulescent with narrower, linear-lanceolate leaves, finely serrulate margins and smaller than M. paniculata.

Knowledge of plant mating system attributes is essential to the conservation of endangered species. The purpose of this study was to examine the functional consequences and conservation implications of protandry, andromonoecy, and mating patterns in the critically endangered and clonal plant, Ptilimnium nodosum. We conducted intra- and interfloral phenological observations to quantify opportunities for geitonogamy and calculated floral sex ratios of sequentially blooming umbel orders. We also provide information on P. nodosum's mating system. Flowers are self-compatible, but strong intrafloral protandry precludes autonomous selfing (< 1% seed set). Weak interfloral protandry combined with vegetative reproduction, however, provided multiple opportunities for geitonogamy which characteristically decreased with umbel order. Although low, mean seed set was comparable among open pollinated (25%), manually outcrossed (26%), and geitonogamously selfed (21%) pollination treatments, suggesting a mixed-mating system dependent on insect-mediated pollination.

The significant decrease in mean seed set among higher umbel orders in open-pollinated plants is likely a consequence of low floral density and lack of pollinators late in the flowering season. Moderate reproductive output and high seed germinability suggest that environmental conditions, not mating system, regulate the distribution and abundance of P. nodosum and high immediate fitness gained by self-compatibility and vegetative reproduction plays a critical role to the species' short-term persistence.

Knowledge about the factors restricting reproduction in many rare wetland plant species is limited. One such species is Lobelia boykinii. We conducted a study of L. boykinii to determine which factors most influence its reproductive success. We examined the species' breeding system, population dynamics, degree of pollen limitation, importance of sexual versus asexual reproduction, and the role of fungal and herbivore damage on fruit production in three Carolina bay populations in North Carolina. Pollen manipulations revealed that L. boykinii is an obligate outcrosser and that sexual reproduction is pollen-limited. Population size and density, which influence pollinator attraction, can fluctuate greatly over years in the same population. The three populations differed with respects to population size and density, capsule production, vegetative reproduction, and ramet survival, and differences are partially attributable to variation in the degree and timing of herbivory and fungal damage. Herbivory ranged from < 1% to 55% of flowering shoots. Fungal infection decreased fruit production only when it coincided with the period of floral development. Our results indicate that focusing on one ecological factor to prevent extant populations from going extinct is insufficient. Multiple intrinsic and extrinsic factors influence L. boykinii's reproductive success, and populations differ in which factors most strongly influence reproduction. Given this suite of constraints, management strategies should include maintaining as many of the largest remnant populations as possible.

Two species of Stratiomyidae, Ptecticus nigrifrons Enderlein and Ptecticus sp., were reared from fallen androecia of Lecythis poiteaui Berg (Lecythidaceae) at rain forest sites in French Guiana. Floral aromas were collected by headspace adsorption from the night-blooming flowers. Gas chromatography-mass spectrometry analysis (GC-MS) identified several sulfur-containing compounds that contribute to the characteristic foul odor of the flowers. Although stratiomyids are thought to be generalist associates of decaying matter of plant and animal origin, we suggest that fetid floral attractants may make L. poiteaui flowers especially attractive to certain flies. This is the first report of Lecythidaceae flowers hosting stratiomyid flies.

Previous work indicates that an evergreen shrub layer dominated by Rhododendron maximum L. and/or Kalmia latifolia L. is a critical component of Appalachian forests, potentially exerting control over forest structure and succession. Moreover, communities characterized by thickets of evergreen understory shrubs exhibit distinct patterning on the landscape associated with topographic gradients and disturbance. We compare distributions of R. maximum and K. latifolia in the warmer and drier Ridge and Valley physiographic province and on the cooler and wetter Allegheny Plateau of western Maryland and adjacent Pennsylvania and find that the relationships between community composition and the environment differ between these two physiographic provinces. Kalmia latifolia dominance is strongly associated with topographically dry locations and a history of gypsy moth defoliation, while R. maximum is associated with topographically wet positions in the Allegheny Plateau, but less so in the Ridge and Valley. ANOVA identified significant differences in midstory volume and basal area and leaf area index of canopy tree species where evergreen understory shrub species were prominent. Specifically, basal area and leaf area were lower above K. latifolia understory communities, and midstory volume was found to be lower in areas where K. latifolia and R. maximum were abundant. However, the results show that cover of K. latifolia must be sufficiently continuous (i.e., not patchy) for the midstory volume to be affected. In plots with a history of gypsy moth infestation, basal area was found to be significantly lower in plots where K. latifolia thickets were present than where it was absent, suggesting that K. latifolia impedes structural recovery from this disturbance.

Forests of the Cumberland Plateau physiographic province have undergone significant change over the past century due to anthropogenic disturbances, and the magnitude and direction of this change will have important consequences for forest management and biodiversity conservation. Cove and upland forest communities on the Cumberland Plateau are in close proximity to one another, but have maintained distinct composition due to soil differences. Several anthropogenic influences common to other southern Appalachian forest communities, including fire suppression, predator removal, and introduction of pathogens, continue to drive change in these forests but remain relatively undocumented. In this 10-year study of these two major forest types, those disturbances were expected to homogenize cove and upland forests, with compositions increasingly dominated by generalist species, similar to trends elsewhere. Composition and structure were considerably altered in both communities over the course of this study, but non-metric multidimensional scaling showed that the cove and uplands remained distinct. Both communities were experiencing a steady replacement of Quercus species by Acer species, but A. saccharum and A. rubrum dominance were limited to the cove and uplands respectively. A. saccharum expansion in the coves is in contrast to trends reported in other studies of Appalachian forests. Replacement of Quercus species by Acer species was more advanced in the high-productivity cove forest; however, the trajectory of change was more consistent among upland forest plots. Documenting long-term status and trends in these forested communities will be critical for managing disturbance regimes and predicting consequences for regional biodiversity.

Ten dry prairie remnants in south-central Wisconsin first sampled in 1950 were resampled in 2005 to determine changes in species presence and frequency and to characterize differences between species that increased and decreased in abundance. Combined species richness over all sites has increased (from 147 to 189), but this largely reflects the recruitment of exotic species, woody vegetation, and taller shade-tolerant species. Mean native species richness per site decreased (from 65.2 to 59.7) reflecting the loss of rarer and shorter forbs while mean exotic species richness increased greatly (from 0.3 to 10.1). Although the average number of habitat generalist species per site has remained constant (13.0 vs. 13.6), the number of habitat specialists has declined (from 27.4 to 21.7) contributing to declines in floristic quality. The five native species that decreased in occurrence and 15 that decreased in frequency tended to be short, non-clonal specialist forbs. The seven native increaser species tended to be tall, clonal, and/or woody generalists. Efforts to conserve dry prairies should thus focus on those species most at risk (i.e., rare, short-statured, and non-clonal) and the processes that sustain them. Burning and removing exotic species and woody vegetation appear to enhance our ability to conserve and maintain plant diversity in dry prairie remnants.

Heavy infestations of a non-indigenous shrub, Amur honeysuckle (Lonicera maackii) are frequently linked to poor individual performance and reduced species diversity. We used chronosequence methods and analysis of forest strata to investigate potential impacts of L. maackii on 1) species richness, 2) density of sub-canopy recruitment layers, 3) indicator species affinity, and 4) within- and among-strata compositional similarities. We compared sites ranging from 12 to 26 years since initial invasion as well as non-invaded, control sites. When assessing non-invaded versus long-invaded sites, we found significantly (P ≤ 0.05) reduced densities in the herb (−57%), seedling (−58%), and sapling layers (−90%), and also reduced species richness in the seedling (−34%), and sapling (−58%), and herbaceous layers (−4%). Interestingly, the germinable seed bank density showed significant increases among non-invaded and long-invaded sites ( 78%), while the species richness of the seed bank demonstrated a marked decrease (−41%). Indicator species analysis found that most species had greater frequencies and abundances in non-invaded sites, and nearly all species had greater affinities for the non-invaded sites, especially in the seedling, sapling, and seed bank layers. Responses were species-specific in the herbaceous layer. Within-layer species similarity decreased with increased time of L. maackii occupancy in all sub-canopy strata. This pattern was also found with reductions in between-layer compositional similarity for the long-invaded (r = 0.16) versus the recently-invaded (r = 0.37) and non-invaded (r = 0.51) sites. Our data suggest that in many invaded sites, habitats are experiencing wholesale alterations in species composition, structure, and successional trajectory, and invasion may also change competitive interactions in forest understories as well as alter between-layer species linkages. These results validate the candidacy of L. maackii sites for increased removal and restoration efforts.

Despite concern over potential detrimental effects of non-native invasive species on human and natural systems, the factors controlling regional distributions of invasive species remain unresolved. Few studies have evaluated the influence of both environmental factors and disturbance history on invasive species distributions, or assessed synthetically the importance of landscape-level disturbances like historical land-use, forest harvesting, and contemporary forest fragmentation. We analyzed vegetation, soils, and recent and historical land-use and landscape context for forests across central and western Massachusetts to identify controls on invasive species distributions. Almost half (49.3%) of 148 randomly selected sites had at least one non-native invasive plant present, and invasive species occurred more frequently on former agricultural sites than in continuous woodlands. We used logistic regression to model the probability of finding the four most common species: Japanese barberry (Berberis thunbergii DC), glossy buckthorn (Rhamnus frangula L.), multiflora rose (Rosa multiflora Thunb. ex Murr.), and oriental bittersweet (Celastrus orbiculata Thunb.). Soil richness was the most important predictor of invasive presence, with rich soils (i.e., lower C:N) being more likely to have these species. The structure of the current forested landscape (i.e., the amount of forest within a 10 km buffer around a site) is also important, with sites that are surrounded by more forest being less likely to have invasives. After accounting for variation in C:N ratios and the structure of the current forested landscape, historical land-use was not a significant predictor of non-native species occurrence; however, C:N ratios may be influenced by historical land-use and by current vegetation, thus complicating interpretations of this edaphic variable. Recent forest harvesting increased the likelihood of invasive occurrence for some but not all species. Overall, our results suggest that regional patterns of invasive plant distributions result from a complex function of edaphic conditions, and present and historical land-uses.

We investigated the influence of fungivorous soil invertebrates on seedling emergence from soil mesocosms buried in a ruderal grassland. Two out of three tested plant species, Centaurea nigra and Origanum vulgare, had a higher seedling emergence when we added the fungivorous collembolan Protaphorura fimata to mesocosms, compared to a control treatment where we excluded soil mesofauna by using defaunated soil and preventing re-colonization from the ambient soil. P. fimata increased seedling emergence to a similar extent as a treatment of the seeds with the fungicide Aathiram. In contrast, a treatment designed to allow re-colonization of defaunated soil from the ambient soil did not result in increased seedling emergence compared to the control treatment. In a third plant species, Anthriscus sylvestris, overall seedling emergence was too low for any significant treatment effects to be detected. This study corroborates the findings of a previous experiment carried out in the laboratory to explore the influence of P. fimata on seed mortality under controlled environmental conditions and shows that there are similar effects on seedling emergence under field climatic conditions.

Colonial period agriculture and vegetation clearance practices during the American Revolution destroyed the pre-Columbian forest of Inwood Hill Park, Manhattan, New York. Native species plantings in early estates spread to form the park's forest, and post-1850 estates introduced non-native species. Parks Department management practices from 1930 to 1985 reduced forest cover, filled wetlands, and caused the number of non-native and invasive shrub and vine species to nearly triple. Liriodendron tulipifera L. and Lindera benzoin (L.) Blume have been identified as the dominant species in the Valley Forest since 1930. Prunus serotina Ehrh., Sassafras albidum (Nutt.) Nees. and Viburnum acerifolium L. have continued to form fire-adapted stands in the East Ridge and Slopes Forest. In 2003, the highest density for Prunus serotina occurred in the repeatedly disturbed stands of the West Ridge and Slopes Forest. Alliaria petiolata (Bieb.) Cavara & Grande, an invasive species, was present only in the Ridge Tops Forest in 1985 and has become the dominant non-native herb species in all of the forests. The invasive shrub and vine species Celastrus orbiculatus Thunb., Lonicera japonica Thunb., L. maackii (Rupr.) Maxim., and Rosa multiflora Thunb. have become the dominants in the cleared areas of the Ridge Tops Forest. Sixteen woody invasive species are displacing native species across the park. Soil eroding into the salt marsh has caused the dominance of upland disturbance species. Replacing invasive species with native species has had mixed success because of limited funding to maintain plantings in the dry, impoverished soils of the park and areas treated with herbicides. Assessment methods for the restoration projects and for monitoring long-term species changes are recommended.