Morphological intermediates between Tamarix ramosissima or T. chinensis (saltcedars) and T. aphylla (athel) were found recently in three locations in the southwestern USA, and were assumed to be hybrids or a previously unreported species. We sequenced chloroplast and nuclear DNA from putative parental and hybrid morphotypes and hybrid status of morphological intermediates was supported. Chloroplast data suggest that the seed source for these hybrids is T. aphylla. Invasive T. aphylla genotypes found in Australia match those found in the USA. Seed was collected from one of the hybrids, and a low percentage of it was viable. This hybrid combination has not been previously reported in the USA or the native ranges of the species. Although populations of this novel Tamarix hybrid appear to be uncommon at present, both parental species are considered invasive (saltcedars in North America; athel in Australia), and it is possible that more aggressive hybrid genotypes could be produced. Therefore, natural resource managers concerned with the potential spread of non-native species should be aware of the existence of these plants and monitor their future spread.

Seed bank dynamics are a critical consideration for management of arid and semi-arid shrublands. In the threatened “coastal succulent scrub” vegetation (at Punta Banda, Baja California), we studied the seed bank's composition and size, as well as its dynamics as shown by field emergence and as inferred from literature reports on germination. We also analyzed sampling effort for both seeds and seedlings. The seed bank was sampled just prior to the rainy season, with 130 soil units of 7-cm diameter ×1-cm depth distributed systematically over 1.66 ha. The field samples were mixed together then laboratory samples (17 of 14 cm³) were taken for manual extraction of seeds. We found 25 species, mostly of short-lived herbs. Some obvious species of the local flora were not encountered. Overall density was approximately 11,807 seeds m⁻², but densities differed by more than 100-fold among species. Analysis of sampling effort suggested that only 8–12 laboratory samples were needed to approach estimated asymptotes of the density of seeds and the number of species. Seedling emergence was recorded during four months on 30 randomly distributed and caged plots of 361 cm². We found 22 species, mostly short-lived herbs. Most species were uncommon and the density per plot of all species was highly skewed. Modes per plot were 3–4 species and 129–256 seedlings. Analysis of sampling effort suggested approximately 15 plots were needed to approach estimated asymptotes of the density of seedlings and the number of species. Published information on seed germination was found for 75 species which have been reported from coastal succulent scrub in the Punta Banda area. Apparently, fire-related cues were required for germination in only 13% of these, while most species may require only moist winters. However, long-term dynamics of the seed bank, and its geographic variation, remain to be studied.

Forest encroachment into grasslands is a widespread phenomenon with significant implications for land management. We examined the influence of seed dispersal and predation on the encroachment of two tree species, Lithocarpus densiflora and Pseudotsuga menziesii, into a coastal California grassland. We mapped the distributions of L. densiflora and P. menziesii seedlings and saplings and L. densiflora acorns across the forest-grassland ecotone as well as quantified the fates of seeds of both species experimentally located at five distances across the ecotone. Species distributions varied, with P. menziesii being most abundant in the grassland and at the edge and L. densiflora in the forest. Lithocarpus densiflora acorns were absent from the grassland but equally abundant at the edge and forest. Seed predation was similar for both species, being low in the grassland, variable at the edge, and high in the forest. It appears that L. densiflora encroachment into the grassland is strongly influenced by seed dispersal, while P. menziesii encroachment is more likely influenced by seed predation than dispersal.

In this study, I investigated the effects of seed size and habitat on post-dispersal predation of Quercus chrysolepis and Lithocarpus densiflora acorns in central coastal California. Tagged acorns were located at five distances across two forest-grassland ecotone sites. Although Q. chrysolepis acorns were nearly twice as large as those of L. densiflora, there was no significant difference in predation between the species or sites. There was, however, a significant difference in acorn predation between habitats, with both species having much higher rates of predation in the forest than in the grassland. While predation occurred across the forest-grassland ecotone, acorn burial only occurred in the forest. These results suggest that habitat had a stronger effect on post-dispersal predation than seed size.

Tragopogon mirus is a recently formed allotetraploid species, with Tragopogon dubius and Tragopogon porrifolius as the parental species. A study was conducted on Tragopogon populations in Oregon, USA to determine if T. dubius and T. porrifolius hybridization and subsequent polyploid speciation had occurred. We examined ploidy levels as well as nucleotide data from the chloroplast trnT-trnL spacer and nuclear ribosomal ITS regions. While no hybridization or polyploid speciation was found, a seven base pair length mutation found in the chloroplast trnT-trnL spacer region should prove useful for determining parentage in populations of T. mirus.

Most studies of alpine vegetation communities focus on the variation occurring across large scales, in which diverse environmental habitats are assessed across the landscape and detailed plant associations are described. However, community patterns occurring at more intricate scales are easily concealed by such a broad perspective. To complement large-scale studies, we assessed smaller-scale patterns occurring at the extremes of moisture and exposure gradients in an alpine environment. We studied the variation in plant community composition among and within seven ridges extending down two rocky metamorphic peaks in Yosemite National Park. Species cover and environmental factors (proximity to a summit, elevation, aspect, slope, and substrate size) were sampled in 281 2 × 2-meter plots. Variation among ridges was primarily determined by differences in aspect. Within the ridges, although the physical environment in which we sampled was seemingly homogenous, ordinations identified two distinct vegetation types: (1) high diversity and high cover vegetation (HD), dominated by cushion plants and (2) low diversity and low cover vegetation (LD), dominated by plants in large clumps or small rosettes. In general, LD vegetation was found nearer to the summit and was highly variable in its component species, while HD vegetation was found farther along the ridgeline and was relatively uniform. This non-intuitive pattern in which cushion plants do not dominate the most exposed habitat occurred independent of elevation. Instead, our data suggest that along with changes in rock size and aspect, proximity to a summit is a meaningful factor governing alpine community structure. We discuss the water limited conditions imposed by the absence of smaller rock structure at the summit and how this may allow for only the sparse LD vegetation to persist there.

Insect herbivory has been shown to have substantial impacts on plant growth and reproduction in many systems. However, the effect of insect herbivores on rare and endangered plants has not been widely studied, even though natural limitations on growth and reproduction, in combination with anthropogenic changes in habitat quality and quantity, likely contribute to population decline. In the current study, an insect exclusion experiment was used to assess the effects of insect herbivory on a federally listed endangered annual plant: Chorizanthe robusta var. robusta (Polygonaceae). The primary insect herbivore was a microlepidopteran larva, an undescribed species of Aroga (Gelechiidae). Excluding Aroga larvae led to a 30% increase in seed output compared to water control. No change in plant survivorship or seed/flower ratios was found with insect exclusion. Control plants given supplemental water had increased seed production, but only in the absence of Aroga infestation, an indication that infested plants could not fully exploit additional resources. These results show that rare annuals are potential host plants for insect herbivores, and herbivory is an important factor to consider when evaluating endangered plant populations.

Ecological data are lacking for many species covered in multi-species habitat conservation plans and other regional conservation plans. Erodium macrophyllum (Geraniaceae) is a rare native annual forb found throughout California, southern Oregon, and northern Baja California (Mexico) for which very little ecology is known. I report on the habitat characteristics and current and historical distribution of E. macrophyllum by collecting data on populations in Riverside and San Louis Obispo Counties and by conducting an herbaria search and electronic-mail survey. Erodium macrophyllum population sizes range from a few individuals to over 1000 and are restricted to heavy clay soils. Most populations are found on the eastern side of the coast ranges in California. The clay soils on which it is found typically have low cover of native and exotic species but often have other rare species. They are also generally low in nitrogen and phosphorus, but there is considerable variation. Based on herbaria records and the e-mail survey, E. macrophyllum was probably once more common and may have occurred on other soil types.

Phylogenetic studies of Lessingia Cham. show that different corolla coloration (pink/white vs. yellow) diagnoses the two major clades of Lessingia sensu stricto. There are no taxonomic changes in the “pink/white group” but two taxa within the “yellow group,” recognized by Lane (1993) as L. glandulifera A. Gray and L. lemmonii A. Gray, are not monophyletic and have therefore been realigned to reflect natural lineages. The circumscription of L. lemmonii sensu Lane (1993) has been expanded and now includes the type specimen of L. glandulifera, a name that has priority over L. lemmonii. Plants included in a narrowed circumscription of L. glandulifera sensu Lane (1993) will now be recognized as L. pectinata Greene. Lessingia glandulifera A. Gray var. peirsonii (J. T. Howell) Markos and L. pectinata Greene var. tenuipes (J. T. Howell) Markos are new combinations.

The new combination Boechera holboellii (Hornem.) Löve & Löve var. pendulocarpa (A. Nelson) N. Snow is made to accommodate this taxon at the rank of variety in that genus for the Southern Rocky Mountain Flora project.

A new variety of Ericameria discoidea is described and illustrated. The variety is known from two locations in southeast Idaho and southwest Wyoming. It resembles E. discoidea var. linearis but has broader leaves that lack the glands that are usually present in var. linearis.

Thirty-four mosses and two liverworts are reported new for the state of Nevada. The moss family Scouleriaceae is new for the state. Genera new for Nevada include: Blindia, Dichodontium, Eucladium, Molendoa, Orthodicranum, Porotrichum, Pterigynandrum, Rhizomnium, Roellia and Scouleria.

In 1853 the Kaweah River delta (western Tulare County) was one of California's richest natural habitats, the so-called Giant Oak Forest its leading feature. By 1920 this unique formation was completely cleared, drained, and leveled for intensive agricultural use. We present a reconstruction of the 1853 vegetation pattern based on U.S. General Land Office survey notes.