Microsatellite primers for the narrowly endemic shrub Eriogonum giganteum (Polygonaceae)

? Premise of the study: Microsatellite primers were designed for Eriogonum giganteum var. formosum, an endemic shrub of San Clemente Island, to investigate population structure, genetic diversity, and demographic history. ? Methods and Results: Twelve polymorphic microsatellite loci were isolated from the California Channel Island endemic Eriogonum and were screened for variability. The primers amplified one to eight alleles in the target taxon. Many primers also amplified in conspecific and congeneric (E. arborescens, E. fasciculatum, E. grande, E. latifolium, and E. parvifolium) taxa and in the closely related Chorizanthe valida. The total number of alleles per locus for all taxa screened ranged from three to 24. ? Conclusions: These primers will be useful for conservation genetic and evolutionary studies within the California Channel Island endemic Eriogonum.     

Analysis and structure of four lentic communities on the Colorado (U.S.A.) shortgrass prairie

Four natural lentic habitats on the Central Plains Experimental Range in Colorado were intensively studied physically, chemically, and biologically for 2 yr (1968–1970) and intermittently for 5 (1971–1975). Lynn Lake and Lake George were chosen as examples of ephemeral or temporary sites, while Cottonwood Pond and Spring Pond were chosen as permanent habitats. Chemically, the waters of each site were analytically separated into dissolved and suspended (sestonic) components. The temporary sites were characterized by their exceptionally high seston loads, the presence of Eubranchiopoda, the prevalence of Ca as the major dissolved cation, ana the high Fe content of their sediments. The two permanent sites, on the other hand, had high total dissolved salt content, rich and varied flora and fauna, Na as the prevalent cation in the dissolved fraction, and high Ca content in the sediments. All four of the sites were “seston digesters” with large amounts of wind-blown organic material being entrapped, decomposed, and mineralized. By comparison with adjacent soils the sediments of all four basins were much richer in K, Zn, Fe, Cu, and Mn. Both temporary and permanent sites function as nutrient sinks. Rates of daily and annual phytoplankton primary productivity are reported for the two permanent sites.     

Microbial response to drought in a Texas highplains shortgrass prairie

The population of the microbial flora of a mixed blue gramma grass (Bouteloua gracilis H. B. K.) and prickly pear (Opuntia polyacantha Haw.) prairie near Amarillo, Texas, was studied during 1971 after a severe drought. Bacteria, fungi, and algae were estimated by plate count and terminal dilution procedures. Rates of grass and paper decomposition were determined. The microbial flora of soil associated with bovine-grazed grass did not differ significantly from the flora associated with ungrazed grass, either qualitatively or quantitatively. During drought, a greater number of fungi were found in soil associated with prickly pear than in that associated with blue gramma grass. The microbial biomass decreased one full log between the surface and a depth of 50 cm, and the percentage of anaerobes increased with depth. The maximum numbers of fungi and algae detected were 8 × 10⁵ and 6 × 10⁴/g respectively. A linear relationship existed between the microbial biomass and soil moisture. The maximum number of aerobic, heterotrophic bacteria detected was 1.5 × 10⁸ viable cells per g of soil.     

Pollination limitation to reproductive success in the Missouri evening primrose, Oenothera macrocarpa (Onagraceae)

Habitat fragmentation may result in plant populations that are less attractive to pollinators and thus susceptible to reduced reproductive output due to pollination limitation. Pollination limitation was investigated in three Missouri populations of Oenothera macrocarpa, a hawk-moth-pollinated, perennial herb. The populations represented extremes in size and habitat quality. Following supplemental pollination, mean fertilization success (proportion of ovules fertilized) across populations increased from 24.3 to 44.8% and mean seed set (proportion of ovules that matured into seed) increased from 14.7 to 27.9%. These increases were statistically significant in two of the three populations. Failure to achieve 100% fertilization and seed set following supplementation indicates that other factors, in addition to pollination, were limiting to female reproductive success. Fruit set was pollination limited in only one population. Fruits matured with as few as one seed, suggesting that fruit set was not resource limited. The degree of pollination limitation was greatest in the most disturbed population. The population located in the highest-quality habitat was not significantly pollination limited. This suggests that pollination limitation is occurring, at least in part, because of reduced pollinator activity in degraded habitats.     

Notes on the genusOenothera subsect.Oenothera (Onagraceae) in the Czech Republic

Up-to-date results of taxonomic and phytogeographic studies ofOenothera subsect.Oenothera in the eastern part of the Czech Republic (Moravia and Silesia) are presented. A new hybridogenous species,Oe. moravica Jehlík etRostański (=Oe. fallax × Oe. victorini), is described from S Moravia. Several taxa and hybrids are reported for the first time for the Czech Republic:Oe. victorini Gates etCatcheside (=Oe. rostanskii Jehlík),Oe. × wienii Renner exRostański,Oe. acutifolia × Oe. victorini. Other taxa are recorded from the eastern part of the Czech Republic for the first time:Oe. acutifolia Rostański,Oe. hoelscheri Renner exRostański,Oe. parviflora L.,Oe. subterminalis Gates. The taxonomy ofOe. pycnocarpa Atkinson etBartlett is discussed. A survey of species and hybrids ofOenothera subsect.Oenothera in the Czech Republic is added.     

Heterogeneity in shortgrass prairie vegetation: the role of playa lakes

Abstract. We examined the role of playa lakes in promoting regional heterogeneity on the southern High Plains. The goals of this paper were to: (1) describe vegetation types and zonation patterns within playas, (2) evaluate patterns of species distribution and abundance within and among playas, and (3) assess patterns of heterogeneity within and among playas on a portion of the southern High Plains. Perennial grasses were the most abundant species in playa vegetation. Playa vegetation exhibited distinct and repeatable vegetation zones at the majority of sites, but the number of distinct zones varied from site to site. Agropyron smithii, Buchloë dactyloides, and Panicum obtusum were the most important species of playa interior zones, and Bouteloua gracilis, Buchloë dactyloides, and Schedonnardus paniculatus were important upland species outside of playas. Species distribution and abundance were positively correlated at 38 of 40 sites. The distributions of species occurrences among sites were unimodal both locally and regionally. The degree of heterogeneity varied from playa to playa. Local heterogeneity within playas was found to increase regional heterogeneity; therefore, playas increase both local and regional heterogeneity of vegetation. Long-term monitoring will be necessary to understand the spatial and temporal response of vegetation within and among playas to stochastic climatic factors on the southern High Plains of North America.     

Organ- and Tissue-specific Biosynthesis of Flavonoids in Seedlings of Oenothera odorata (Onagraceae)

In developing Oenothera odorata seedlings, phytochrome-mediated accumulation of various flavonoids (mainly glycosides of cyanidin and quercetin) is detectable, subsequent to a transient induction of the key enzymes of the general phenylpropanoid metabolism, L-phenylalanine ammonia lyase (PAL) and of flavonoid biosynthesis, chalcone synthase (CHS). Organ- and tissue-specific distribution of these enzymes and of the flavonoid end products was investigated in seedlings, irradiated with continuous far-red light. Anthocyanins and quercetin glycosides are mainly localized in both the upper and lower epidermis of the cotyledons and to a lesser extent also in the epidermal cell layer of the hypocotyl. An obvious organ-specific distribution was observed for the anthocyanins: cyanidin-3,5-O-diglucoside accumulates in the epidermal cells of the cotyledons, whereas cyanidin-3-O-glucoside is restricted to the epidermis of the hypocotyl. By contrast the pattern of quercetin glycosides is the same in the cotyledons and in the hypocotyl. The methylated flavonol aglycone 3-0-methylquercetin was found to be localized in the seed coat. According to this organ- and tissue-specific pattern of flavonoids, immunochemical and immunohistochemical detection of PAL and CHS revealed a predominant localization of theenzymes in the epidermal layers of the cotyledons and the hypocotyl but also in the cells surrounding the vascular bundles. The role of compartmentation in regulation of flavonoid biosynthesis and putative functions of flavonoid compounds are discussed.     

Spatiotemporal variation in the reproductive ecology of two parapatric subspecies of Oenothera cespitosa (Onagraceae)

?Premise of the study: Flowering plants that rely on pollinators for most of their reproduction may experience unpredictable and inconsistent availability of effective pollinators throughout their reproductive lifetime. We investigated the reproductive ecology of two subspecies of the tufted evening primrose, Oenothera cespitosa, which occupy geographically and edaphically distinct habitats in western North America: O. cespitosa subsp. navajoensis inhabits sandstone soils on open sites or rocky slopes in the Colorado Plateau and O. cespitosa subsp. cespitosa grows in clay soils on talus slopes and exposed rocky ridges in the western Great Plains and northern Rocky Mountains of the United States. ?Methods: Pollen augmentation and selfing experiments, floral visitor observations, and single-visit effectiveness experiments were conducted over 4 years to examine the breeding system and spatiotemporal variation in pollinator behavior, assemblage, and abundance at different populations for each subspecies. ?Key results: Both subspecies of O. cespitosa were self-incompatible and pollen-limited, suggesting that the relative abundance, effectiveness, and movement patterns of different insects as pollinators influenced the quality and quantity of seed production in these plants. Medium-sized vespertine hawkmoths (Hyles lineata, Sphinx vashti) were effective pollinators when present, as were large matinal bees (Anthophora affabilis, A. dammersi, Xylocopa tabaniformis androleuca), whereas small oligolectic Lasioglossum bees primarily functioned as pollen thieves in the evening and morning. ?Conclusions: These findings highlight the importance of variability of pollinator composition and abundance in the evolution of plant breeding systems and reproductive success at varying spatial and temporal scales.     

Clonal repeatability of in vitro pollen tube growth rates in Oenothera organensis (Onagraceae)

The concept that pollen selection is an important force driving angiosperm evolution has received a lot of attention in recent years. In order for pollen competition to have evolutionary significance, heritable variation for pollen tube growth rate must exist. In this study, I tested the clonal repeatability, a measure of broad-sense heritability, of in vitro pollen tube growth rate in Oenothera organensis. Although I found significant phenotypic differences in pollen tube growth rate, the calculated clonal repeatability value of 9.4% indicates that heritability of pollen tube growth rate in this species is quite low. In contrast, both flower identity and plant identity had highly significant effects on pollen tube growth rate, suggesting that the environment may be more important than genotype in determining pollen performance in this species.     

Microsatellite primers in Carex moorcroftii (Cyperaceae), a dominant species of the steppe on the Qinghai-Tibetan Plateau

? Premise of the study: Microsatellite markers were developed in Carex moorcroftii, a rhizomatous clonal sedge that dominates the steppes and meadows of the Qinghai-Tibetan Plateau. ? Methods and Results: Using the combined biotin capture method, 30 microsatellite primer sets were isolated and characterized. Twenty-two of these markers showed polymorphism, and the number of alleles per locus ranged from two to 11 across 96 individuals from four populations. ? Conclusions: These markers provide a useful tool to investigate the clonal structure and mating system of C. moorcroftii.     

Microsatellite primers in the white proteas (Protea section Exsertae, Proteaceae), a rapidly radiating lineage

? Premise of the study: Microsatellite primers were developed in the South African sclerophyllous shrub Protea punctata to investigate the degree of population differentiation within and between P. punctata and closely related species. ? Methods and Results: 10 primer pairs were identified from three individuals of Protea punctata. The primers amplified di- and tri-nucleotide repeats. Across all P. punctata samples, the loci have 8-49 alleles. All primers also amplified in Protea section Exsertae (P. aurea, P. aurea subsp. potbergensis, P. mundii, P. venusta, P. lacticolor, and P. subvestita). The loci had 14-69 alleles across the subgenus. ? Conclusions: These results show the broad utility of microsatellite loci for future studies of population genetics in the white proteas and their potential utility across the entire genus.     

Microsatellite primers in the Chinese dove tree, Davidia involucrata (Cornaceae), a relic species of the Tertiary

? Premise of the study: The first microsatellite primers were developed for Davidia involucrata, an endangered relic species of the Tertiary in China, to further describe its genetic variability and population structure. ? Methods and Results: Using the Fast Isolation by AFLP of Sequences Containing Repeats (FIASCO) protocol, 15 polymorphic microsatellite loci were isolated and characterized in 20 individuals from the germplasm collections of D. involucrata at the Hunan Forest Botanical Garden. High levels of polymorphism were revealed, with the total number of alleles per locus and the number of alleles per locus per individual ranging from two to 13 and from one to six, respectively. ? Conclusions: The multibanded patterns of microsatellite loci obtained in the current study confirmed that D. involucrata might be a polyploid species. The primers will be useful for studies of genetic diversity and for guiding conservation strategies for D. involucrata.     

Livestock exclusion increases the spatial heterogeneity of vegetation in Colorado shortgrass steppe

Abstract. Spatial heterogeneity, an important characteristic in semi‐arid grassland vegetation, may be altered through grazing by large herbivores. We used Moran's I, a measure of autocorrelation, to test the effect of livestock grazing on the fine scale spatial heterogeneity of dominant plant species in the shortgrass steppe of northeastern Colorado. Autocorrelation in ungrazed plots was significantly higher than in grazed plots for the cover of the dominant species Bouteloua gracilis, litter cover and density of other bunchgrasses. No species had higher autocorrelation in grazed compared to ungrazed sites. B. gracilis cover was significantly auto‐correlated in seven of eight 60‐yr ungrazed exclosures, four of six 8‐yr exclosures, and only three of eight grazed sites. Autocorrelograms showed that B. gracilis cover in ungrazed sites was frequently and positively spatially correlated at lag distances less than 5 m. B. gracilis cover was rarely autocorrelated at any sampled lag distance in grazed sites. The greater spatial heterogeneity in ungrazed sites appeared linked to patches characterized by uniformly low cover of B. gracilis and high cover of C₃ grasses. This interpretation was supported by simple simulations that modified data from grazed sites by reducing the cover of B. gracilis in patches of ca. 8 m diameter and produced patterns quite similar to those observed in ungrazed sites. In the one exclosure where we intensively sampled soil texture, autocorrelation coefficients for sand content and B. gracilis cover were similar at lag distances up to 12 m. We suggest that the negative effect of sand content on B. gracilis generates spatial heterogeneity, but only in the absence of grazing. An additional source of heterogeneity in ungrazed sites may be the negative interaction between livestock exclusion and B. gracilis recovery following patchy disturbance.