Recent studies have demonstrated substantial changes in the composition and structure of forests in northeastern North America following Euro-American settlement. Especially striking are the “homogenization” of tree species composition across the region and a steep decline in conifer abundance. However, the presettlement distribution and subsequent changes for individual species at a finer scale are not well documented. In this study, we examine the presettlement and current distribution of Pinus strobus L. (eastern white pine) on specific habitats in the northern hardwood forest of Wisconsin by re-surveying 201 nineteenth-century land survey corners. The status of P. strobus regeneration was evaluated in the second-growth forests, as well as in a set of remnant old-growth stands on comparable sites. P. strobus occurred across a broad range of habitats in the presettlement landscape, including highly productive, mesic sites where it rarely occurs in the modern forest. Former white pine-hemlock-hardwood forests most often transitioned to Acer or Populus dominance, matching compositional transitions of the overall landscape. Pinus strobus was retained at ∼28% of presettlement locations, but a large majority of these were dry-mesic or lower-productivity mesic/wet-mesic sites. The modern distribution of P. strobus in hemlock-hardwood forests appears to be strongly influenced by historical factors, rather than site limitations. Pinus strobus regeneration was rare across habitats in the modern landscape; thus, the habitat differences that led to differential retention may not be as influential on its future distribution. Our findings indicate that restoration of P. strobus to a wide variety of habitats, including high-productivity mesic sites, is supported by historical information and that active restoration is probably necessary across a spectrum of habitats.

Sexual reproduction is often considered essential for evolutionary change, with many plants possessing mechanisms to promote outcrossing and produce genetically variable offspring. Many plant species, however, are also capable of asexual reproduction, but its relative role in population dynamics is often overlooked. Given that sexual reproduction depends in part on mate availability and therefore plant density, would asexual reproduction predominate in rare species, especially those found in highly disturbed habitats? To explore this question, we used field and genetic techniques to investigate the reproductive system of a rare, clonal shrub, Spiraea virginiana Britton, which inhabits the frequently disturbed riparian zone. We performed controlled hand pollinations within and among individuals both within and across populations. We also quantified allelic richness and heterozygosity at a locus purported to control self-incompatibility (SI). Hand pollinations resulted in low total fruit production but more infructescences were produced with outcross pollen (20%) than with self-pollen (2.3%). Low allelic richness (2–7 alleles/population) was found at the putative SI-locus; variation at this locus did not correspond directly with the pollination results, suggesting either the SI system is leaky or that the examined SI-locus is not primarily responsible for incompatibility in this species. This study shows that rarity combined with clonality within a highly disturbed habitat may promote a combination of asexual and sexual reproduction. Although sexual reproduction can occur, it may be limited by a scarcity of available mates for S. virginiana, thereby resulting in primarily asexual reproduction in the species.

To understand the mechanisms by which fern gametophytes compete and the consequences of their interactions, we studied the effects of intraspecific and interspecific chemical competition on spore germination, sexual development, and gametophyte size in two closely related and co-occurring species of Polypodium from eastern North America. We cultured gametophytes of diploid Polypodium appalachianum Haufler & Windham and tetraploid Polypodium virginianum L. and recorded spore germination, sexual development, and gametophyte size and growth rates in a series of treatments representing different levels of competition within and between the two species. We found that mature gametophytes of both species reciprocally inhibit spore germination, sexual development, and growth of neighboring plants; we show that these effects are due to chemical interactions and not competition for resources. Competitive effects on spore germination and sexual development are similar for within- and between-species interactions, but repression of growth and gametophyte size is greater when competing gametophytes are heterospecific. An additional mechanism of intergametophytic competition via proliferous vegetative growth is also reported. We conclude that gametophytes of these species interact through a novel context-dependent chemical system that is independent from sex expression-regulating pheromones (antheridiogens). Our findings indicate that inhibition of growth and development among fern gametophytes is not solely a side effect of antheridiogens, as is generally thought.

The stem epidermis of 23 species and three subspecies of Ferocactus Britton & Rose from the tribe Cacteae-Cactaceae are described and compared using scanning electron and light microscopy. Epidermal-hypodermal samples were removed, prepared for observation, and analyzed using a similarity method. Our observations showed that most epidermal cells had an elongate-tetragonal outline with straight anticlinal walls. However, S and U-undulated anticlinal walls occurred in F. glaucescens (DC.) Britton & Rose and F. peninsulae (Engelm. ex F.A.C. Weber) Britton & Rose (Cactaceae). The microrelief of the anticlines was flat and inconspicuous or striate. The periclinal wall relief varied from none to rugose or verrucose among species; 89% of the studied species had slightly sunken or sunken parallelocytic stomata with 2 or 3 pairs of subsidiary cells. Cuticle thickness varied from 2.54 µm in F. histrix (DC.) G.E. Linds to 39.74 µm in F. flavovirens (Scheidw.) Britton & Rose and their thickness is not related to environment. Silica bodies in the hypodermis cell lumina are present in 90% of the species studied. The epidermal characters of the Ferocactus species have been described in other members of Cactoideae, none of them can be postulated as possible synapomorphies to the genus level. Pustules, which are a cutin accumulations on the outer epidermal walls are distinctive feature of F. emoryi (Engelm.) Orcutt, and here are described for the first time for the Cactaceae. The phenogram revealed three groups, and F. haematacanthus (Salm-Dyck) Bravo was revealed as the most distinct species within the genus as well as F. histrix. Both were the early derived species in the most recent phylogeny. A combination of epidermal characters can help to distinguish some Ferocactus species, but failed to support the infrageneric classifications. However, some groups of species based on their epidermal similarities agree with some clades in the most recent phylogeny.

Clonality and the mechanisms by which populations become established can affect the level and pattern of genetic diversity, which can in turn affect the ecology and evolution of those populations. We used amplified fragment length polymorphisms (AFLPs) to examine genetic diversity and clonality in four isolated populations of the rhizomatous pale pitcher plant, Sarracenia alata Alph. Wood, with particular emphasis on determining the extent of clonal spread and the likely mechanisms by which these populations became established. Genetic variation was greater within (87%) than between (13%) populations. The interpopulation genetic differentiation was a function of geographic distance. The mean (± SE) genetic diversity (H_E) within populations was 0.126 ± 0.006, and the percentage of polymorphic loci within populations ranged from 58.9 to 72.4% (64.3 ± 2.89, mean ± SE). We found no repeated multilocus genotypes among our samples, nor was there evidence of bimodality of genetic differences among individuals within populations. Significant spatial genetic correlation was generally found only within 1 m, and matrix incompatibility analysis indicated that more than 90% of the genetic differences among individuals within each population could be explained by recombination. Our results indicate that asexual spread by this species is minimal. The relatively high genetic diversity within populations, the low differentiation among populations, and the low probability of gene flow among current populations suggest that the study populations are most likely the remnants of populations that were formerly more widespread with greater probability for gene flow.

The genus Vriesea Lindl. comprises about 290 species distributed into two sections: V. sect. Vriesea and V. sect. Xiphion. The genus is recognized as polyphyletic and is historically associated with Tillandsia L., differing from it mainly due to the presence of petal appendages. Here we focus our efforts on the Vriesea taxa in its main center of diversity in southeastern Brazil that are considered to constitute a monophyletic group based on molecular analyses as well as a total evidence approach. We present a morphological description of the species from the Brazilian lineage, and the taxonomic history of the genus. We based our results on extensive bibliographic research and morphological analyses of herbarium material and living specimens, as well as illustrations of the main taxonomic characteristics of the Brazilian lineage of the genus.

In this study, five species of the genus Disciseda are reported for the semiarid region of Northeastern Brazil. Disciseda anomala (Cooke & Massee) G. Cunn. and D. hyalothrix (Cooke & Massee) Hollós are new records for South America; D. verrucosa G. Cunn. is recorded for the first time in Brazil; D. bovista (Klotzsch) P. Henn. and D. candida (Schwein.) Lloyd are new records for Northeastern Brazil. Detailed descriptions of the specimens, comments, illustrations, SEM photos of basidiospores and keys are provided.

Inocybe austrolilacina is described here from Atlantic Forest of Rio Grande do Sul, South Brazil. Its most prominent features are a small lilac pileus and stipe, metuloid hymenial cystidia, small nodulose basidiospores, and lack of caulocystidia. A description, discussion, photograph, and drawings of micromorphological features of this species are provided.