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Naturalized Ilex aquifolium L. (English holly) was first collected in the Pacific Northwest in 1953, based on herbarium records. Field surveys showed it is now commonly naturalized from northwestern California to coastal British Columbia. Ilex crenata Thunb. and I. opaca Aiton were also found growing outside of cultivation, but rarely. A key and seed illustrations are provided to distinguish these three Ilex species. Between 2003 and 2006 twice-weekly visits to naturalized and cultivated hollies in Seattle revealed seven species of birds disseminating seeds by eating the fruits. American robins, Turdus migratorius, accounted for 96% of 2796 frugivory observations on I. aquifolium, followed by European starlings, Sturnus vulgaris (3.2%). Ilex aquifolium fruits ripened in October and persisted for six months, yet 99% of all fruit was consumed between November and February. A study of I. aquifolium seed fate found pre-dispersal diurnal seed predation was rarely observed. Bird-regurgitated seed was more frequently attacked by nocturnal rodents in a sheltered forested setting in Clark Co., Washington (39% losses), compared to an exposed urban setting in Seattle (2% losses). The percentage of viable seed surviving rodent attack was higher in the urban sample (66%) than in the forest sample (24%). Commercial and ornamental use of I. aquifolium is extensive in the coastal region and less-invasive alternatives should be considered, to provide food and cover for urban avians without degrading natural areas.
Fluctuations in plant resource availability are hypothesized to promote exotic plant invasion by allowing propagules already present in an area a chance to successfully compete for unused resources. To examine the relationship between resource enrichment and exotic species invasion, we used selective logging canopy gaps over a range of sizes (56 m2 to >1500 m2) in a redwood forest (Santa Cruz County, CA) as a surrogate for disturbance intensity and level of pulsed resource enrichment. Measurements of abiotic conditions in gaps ca. 10 yr after logging suggest light is the primary difference in current resource availability, though a pulse of light and nutrients likely occurred at the time of gap formation. Exotic species richness and relative cover increased significantly as gap size increased. In a separate manipulative experiment, we compared understory plant composition between artificially shaded and unshaded plots in 2.5-year-old logging gaps. Shaded plots had a lower proportion of exotic species than did adjacent, unshaded plots, showing that light is a critical resource for exotic species in redwood forest habitats. Taken together, these results support the view that both physical disturbance and increased availability of scarce resources contribute to a community's susceptibility to invasion and suggest a linear relationship between the size of logging gaps and the magnitude of exotic species invasion.
The Downingia yina species complex (Campanulaceae), centered in northern California and southern Oregon, currently contains three morphologically distinguished species: D. yina, D. elegans, and D. bacigalupii. This complex of species is notable for high levels of morphological and cytological variation, with chromosome counts of n = 6, 8, 10, and 12. Molecular evidence suggests three main clades within this complex, corresponding more with cytological variation than with morphological variation. Additionally, the molecular evidence suggests a phylogeographic pattern associated with the Cascade Ranges, where members of the clade characterized by chromosome counts of n = 6, 8, and 10 are distributed primarily to the west of the Cascades while members of the clade characterized by chromosome counts of n = 12 are distributed primarily to the east. A third clade characterized by n = 10 is localized in the Lake of the Woods region of southern Oregon. Evidence from morphological, cytological, interfertility, and molecular data was used to re-examine the delimitation of species within this complex. Downingia elegans and D. bacigalupii are maintained, while D. yina is split into three morphologically cryptic species (D. yina, D. willamettensis, D. pulcherrima) that do not form a clade.
We investigated the reproductive biology of the rare and endangered plant, Dudleya multicaulis at five separate sites, three natural and two mitigation sites. We employed dawn to dusk observations to determine the spectrum of pollinators visiting D. multicaulis, took pollen samples from visitors to determine floral constancy, sampled nectar to determine volume produced per flower, examined the number of flowers per inflorescence, the number of those flowers that produced seed, and total seed set to determine reproductive output, completed seed germination tests to determine viability, and transplanted germinated seedlings from Petri dishes to soil to determine how well seedlings survive transplanting. Dudleya multicaulis was visited by flower beetles, native and European honey bees, flies, and a variety of other insects. Nectar production per flower averaged 0.12 µl. Bees averaged 99% floral constancy to D. multicaulis. Reproductive output measured by flower production and fruit/seed set were not significantly different among sites. Among all populations, the average fruit set ranged from 86.9 to 94.4%. The large fruit set coupled with the diversity of floral visitors suggests that D. multicaaulis is not pollinator limited. Data suggest that D. multicaulis is capable of self-pollination in absence of vectors. Seed germination and transplanted seedling survival did not differ significantly among sites. Results suggest that sowing seed may be better for plant establishment rather than transplanting when mitigation is necessitated.
Based upon a specimen first collected by S. N. Stephenson, a new grass species, Distichlis bajaensis H. L. Bell, is described. Stephenson hypothesized that this specimen was a hybrid between D. littoralis and D. spicata. Analyses of sequences of nuclear internal transcribed spacer (ITS) and chloroplast ndhF and trnL–trnF and an examination of gross morphology, blade and lemma micromorphology, and blade transectional anatomy demonstrate that this grass is a new species that may be sister to the remaining Distichlis. The blades of D. bajaensis are yellow-green; those of D. littoralis and D. spicata are blue-green. Distichlis bajaensis can be distinguished from D. littoralis by its exserted inflorescences with glumes present and from D. spicata by its short (0.8–1.5 cm) blades with a bend toward the adaxial side. At and distal to the bend, there are antrorse hairs along the medial vascular bundle. Distichlis bajaensis is known from a single large population growing along alkaline seeps in Arroyo Rosarito in Baja California, Mexico.
Chenopodium littoreum is described as new. It had been incorrectly cited in the past as C. carnosulum Moq. var. patagonicum (Phil.) Wahl, a variety of the South American C. carnosulum. However, C. littoreum differs from the C. carnosulum complex in having narrowly elliptic to lanceolate and mostly unlobed leaves, consistently five stamens per flower, and seeds that are invariably horizontal. Chenopodium littoreum is similar to another South American taxon, C. patagonicum Phil. ( = C. philippianum Aellen), but the latter differs in having basally lobed leaves, sepals fused above the middle, and generally one or two (rarely five) stamens. Chenopodium littoreum has a range currently known only from coastal dunes of San Luis Obispo Co. and Santa Barbara Co. of the Central Coast of California, plus a single historic collection from Los Angeles Co. of the South Coast of California.