Registered users receive a variety of benefits including the ability to customize email alerts, create favorite journals list, and save searches.
Please note that a BioOne web account does not automatically grant access to full-text content. An institutional or society member subscription is required to view non-Open Access content.
Contact email@example.com with any questions.
The genus Kochia and Bassia with which it has been combined, of Chenopodiaceae tribe Camphorosmeae, were at one time considered to include plants native to Eurasia, Australia, and North America, and included species of both C3 and C4 photosynthetic types. This aggregate has been reduced in size by removal of a large group of C3 Australian genera and species. Because of their intercontinental disjunction, the presence of root sprouting, and the results of recent phylogenetic studies, it appears that the two North American species Kochia americana and K. californica, of C3 photosynthetic type, should be removed as well, and we designate Neokochia as a new genus for them. In agreement with a study by other authors, comparison of pubescence characters and ploidy levels within K. americana did not give support recognition of the segregate K. vestita.
We investigated the possible spatial structure and temporal patterns that may determine the distribution and cover of Eleocharis macrostachya and Orcuttia tenuis within two vernal pools located in Tehama County, California. Rock cover, soil depth to hardpan, and basin elevation were compared with E. macrostachya and O. tenuis cover to investigate spatial structure. Yearly E. macrostachya and O. tenuis cover were compared with yearly precipitation and air temperature to assess temporal patterns.
The spatial results suggest that soil depth to hardpan may determine E. macrostachya distribution. Rock cover and basin elevation appeared to have little effect on either E. macrostachya or O. tenuis distribution.
Temporal analyses suggest that biotic interactions such as life history traits and competition may be important factors for E. macrostachya and O. tenuis distribution and density. Orcuttia tenuis cover is relatively stable at scale of 1.0 m2 but varies at a 0.25 m2. Variability at a micro scale could be due to variations in annual air temperatures causing a possible shifting mosaic steady state. Orcuttia tenuis life history traits coincide with adaptations expected for warmer temperatures.
Even though abundance is relatively stable for O. tenuis and E. macrostachya in both pools, there is significant negative correlation and spatial structure between them. Eleocharis macrostachya may dictate O. tenuis density within a pool through a combination of abiotic and biotic features.
Eriophyllum lanatum vars. achilleoides and leucophyllum intergrade in southwestern Oregon. Some populations cannot be unequivocally assigned to either variety. Chromosome counts showed polyploid populations predominating where the varieties meet in southwestern Oregon. Pollen fertility, estimated by cotton blue-lactophenol staining, was the main criterion used to assess barriers to interbreeding. Artificial hybridizations between diploids revealed barriers to interbreeding between vars. achilleoides and leucophyllum, and between each of them and a morphologically intermediate population. The barriers to interbreeding are substantially less developed than those present between most of the other eight varieties of the E. lanatum complex. Supernumerary chromosomes are postulated to be adaptive in Eriophyllum hybrid zones.
Previous phylogenetic and biogeographic studies of Iochroma (Solanaceae) suggested that I. ayabacense S. Leiva is a hybrid between I. cyaneum (Lindl.) M. L. Green and I. lehmannii Bitter. Chromosome counts for these three taxa demonstrate that all have a haploid chromosome number of n = 12, and thus that the formation of I. ayabacense did not involve changes in ploidy level. A comparison of vegetative and floral morphology revealed that I. ayabacense demonstrates a striking intermediacy between I. cyaneum and I. lehmannii. The results support the conclusion that I. ayabacense is a homoploid hybrid between I. cyaneum and I. lehmannii.
We used electrophoretic analysis of isozymes to investigate genetic structure of the Mojave Desert endemic, Yucca brevifolia. To test the hypothesis that, because of geographic isolation, most variation in allele frequencies would be between populations we sampled three subpopulations in each of five distinct populations: Arizona, Joshua Tree, Mojave, Western Mojave, and Utah. Two of nine proteins had isozymes that resolved adequately. One of these, Superoxide dismutase (SOD) was monomorphic. For the other, glucose-6-phosphate isomerase (GPI), five alleles were identified, and the three most common alleles were present in all populations sampled. For GPI, allele frequencies differed significantly between all five populations, as well as between subpopulations in both the Joshua Tree and Arizona populations.
We also tested the hypothesis that there would be strong localized genetic structure due to the high proportion of recruitment attributed to vegetative reproduction. Based on GPI data from an intensively sampled 1 ha plot, genotypes were randomly distributed, and thus sexual reproduction through outcrossing may be the principal mode of recruitment in Y. brevifolia at this site.
This study describes genetic structure within populations of Y. brevifolia based on protein variation at a single locus. Future research, using additional markers (nuclear, cytoplasmic, or both) is necessary to understand the dynamics of gene flow, genetic variation, and recruitment within the species Y. brevifolia
Recent field work and examination of specimens at cas, mich, mo, ny, sfsu, ubc and uc lead us to conclude that Bestia longipes, contrary to some earlier literature reports, is endemic to coastal regions of north-central to southern California. Based on analyses of DNA nucleotide sequence data we recognize Bestia in the Lembophyllaceae.
The taxonomic relationships of Clarkia calientensis were re-evaluated in light of information accumulated subsequent to its designation as C. tembloriensis subsp. calientensis. Closeness of relationship between C. calientensis and C. tembloriensis was based on ease of crossing and on cytological pairing configurations in intertaxon hybrids. These interpretations require the assumptions that closely related species are easy to cross, and that maximum cytological configurations are known. However, extensive crossing data show that sympatric, closely related species of Clarkia are very difficult to cross but allopatric species cross rather readily. Furthermore, the cytological data are incomplete as maximum configurations are seldom observed, and some hybrids have not been produced. In both cases, the required assumptions are not tenable. Sterile hybrids between these two easily crossed taxa are strong evidence that they are not conspecific. Consequently, C. calientensis should be recognized as an independent species. Examination of floral variation in C. tembloriensis led to the recognition of large-flowered, protandrous forms as a new subspecies: C. tembloriensis subsp. longistyla.
Baker (1991) proposed that forest differences observed on either side of a fence were attributable to differences in grazing. The study location is in a subalpine forest on the Pike National Forest adjacent to the fenced boundary of Colorado Springs watershed land. Grazing on the watershed land has been excluded for over a century, and U.S. Forest Service land has had moderate grazing over the same time period. The Forest Service land supports a relatively dense forest comprised primarily of Pinus aristata. The watershed land has a less dense cover composed primarily of Picea engelmannii. Baker (1991) attributed vegetation differences to differential grazing pressure. Additional information suggests an alternate explanation for the vegetation characteristics of this site. In the 1930's, the Forest Service began a program of monitoring areas where trees had been planted or where forest health was a concern. Included in these photographic records is a 1960 photograph of the study area that documents the differences in forest type and cover are related to tree planting activities on the Forest Service side of the fence. The evidence that these trees are planted is based on the linear pattern of trees and a general map that shows where tree planting was done.