bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat shock response of warm‐incubated barley aleurone layers
Authors: Shaw Alisa E. , Brodl Mark R.
Published: February 2008

Heat shock suppresses secretory protein synthesis in GA3‐stimulated barley (Hordeum vulgare cv. Himalaya) aleurone layers by selectively destabilizing their mRNAs and dissociating the stacked rough endoplasmic reticulum (ER) lamellae upon which they are translated. Heat shock also increases phosphatidylcholine (PC) synthesis, and these PC molecules have increased levels of fatty acid saturation. This appears to be adaptive, for aleurone layers maintained at heat shock temperatures for 18 h resynthesize secretory protein mRNAs, rebuild stacked ER lamellae, and resume secretory protein synthesis. In the present study aleurone layers were incubated at warmer than normal pre‐heat shock temperatures to determine whether this would favor the formation of heat‐resistant ER lamellae that could continue secretory protein synthesis during heat shock. Western blot and SDS‐PAGE analyses showed that such treatment did not induce heat shock protein (HSP) synthesis, but it preserved significant secretory protein synthesis during heat shock. Northern hybridizations revealed that levels of mRNAs encoding secretory proteins were several‐fold elevated as compared to 25°C preincubated controls, and transmission electron microscopic observations revealed stacked ER lamellae. Thin layer and gas chromatography showed that PC molecules in warm‐incubated barley aleurone layers had more fatty acid saturation than did controls. These observations indicate that previous incubation temperature influences both the induction of HSP synthesis and the suppression of normal protein synthesis in the heat shock response. However, we found that it does not affect the temperature at which heat shock becomes lethal.
Ontogenetic origins of floral bilateral symmetry in Moringaceae (Brassicales)
Authors: Olson Mark E.
Published: February 2008

Floral morphology of the 13 species of Moringa ranges from actinomorphic flowers with little hypanthium to highly zygomorphic flowers with well‐developed hypanthia. Scanning electron and light microscopy were used to identify ontogenetic differences among two actinomorphic and eight zygomorphic species. All species show traces of zygomorphy between petal organogenesis and anther differentiation. At late organogenesis, zygomorphy is manifest by one petal being larger than the others, slight unidirectional maturation of the anthers, and in many species, some staminodes may be missing. At organ differentiation and beyond, the actinomorphic species show a trend toward increasing actinomorphy, whereas the zygomorphic features of early ontogeny are progressively accentuated throughout the ontogeny of the zygomorphic species. Because of the early traces of zygomorphy throughout the family, ontogeny in Moringa does not resemble that known from the sister taxon Caricaceae, which has flowers that are actinomorphic throughout ontogeny. Great intraspecific variation was found in floral plan in the actinomorphic‐flowered species in contrast to the zygomorphic species. Each of the main clades in the family is distinguished by at least one feature of floral ontogeny. In general, ontogenetic differences that are congruent with deeper phylogenetic splits tend to occur earlier in ontogeny than those congruent with more recent divergences.
Phylogenetic relationships among Poaceae and related families as inferred from morphology, inversions in the plastid genome, and sequence data from the mitochondrial and plastid genomes
Authors: Michelangeli Fabian A. , Davis Jerrold I , Stevenson Dennis Wm.
Published: February 2008

A phylogenetic analysis of the Poales was conducted to assess relationships among Poaceae and allied families. The analysis included 40 taxa, representing all families of the Poales as circumscribed by the Angiosperm Phylogeny Group (APG), plus five of the six unplaced Commelinid families in the APG system. The data matrix included 98 informative characters representing variation in morphology and chloroplast genome structure (including three inversions in the chloroplast genome), and 563 informative characters derived from rbcL and atpA nucleotide sequences. Ecdeiocolea has the 6‐kilobase (kb) chloroplast genome inversion previously reported in Joinvillea and Poaceae, and like Joinvillea it lacks the trnT inversion that occurs in grasses. Analysis of the morphological data places Poaceae in an unresolved relationship relative to several other taxa, including Joinvillea and Ecdeiocolea, while analysis of the molecular and combined data resolves Ecdeiocolea as sister of Poaceae, with Joinvillea the sister of this group. Although the 6‐kb and trnT inversions are non‐homoplasious in the phylogenies obtained in this study, the 28‐kb inversion is optimized as having originated twice (once in Restionaceae and another time in the most recent common ancestor of Ecdeiocolea, Joinvillea, and the grasses); an alternative interpretation is that it arose once and was later lost in Anarthria. Ecdeiocolea shares with Poaceae the presence of operculate, annulate pollen that lacks scrobiculi, and a dry, indehiscent fruit.
C3shrub expansion in a C4grassland: positive post‐fire responses in resources and shoot growth
Authors: McCarron James K. , Knapp Alan K.
Published: February 2008

Changes in land management and reductions in fire frequency have enabled woody species to increase in grasslands worldwide. Nevertheless, fire is rarely eliminated from grasslands, and for shrubs to survive, they must be able cope with fire and replace aboveground structures. Because new shoots may have more available solar radiation, greater root : shoot ratios, and thus more resources available belowground after fire compared to undisturbed shrub communities, we hypothesized that carbon, nutrient, and water relations may be enhanced in stems compared to those in an undisturbed grassland. However, this same post‐fire resource pulse stimulates the grasses and may intensify competitive interactions between shrubs and grasses. To test these predictions, we measured seasonal patterns in net photosynthesis (A), predawn xylem pressure potentials (XPP), leaf nitrogen (N) content, and productivity ofCornus drummondiishoots from shrub patches (islands) of different sizes in mesic grasslands burned annually, burned infrequently, and protected from fire. Seasonal averageAwas 20% higher (P= 0.016) in burned than in unburned shrubs, regardless of island size. Shrubs in burned sites also produced shoots with higher leaf N than unburned shrubs, and N content was higher in leaves from small islands compared to large islands (P< 0.0001). Burning caused a decrease in late summer predawn XPP in small islands (−3.1 MPa), whereas burned large islands did not differ from unburned shrubs. Post‐fire productivity of new shoots was significantly greater compared to shoots in unburned sites. These results indicate that a transient period of high resource availability after fire allows for increased growth and rapid recovery of grassland shrubs. Thus, although fire has a negative effect on aboveground biomass of shrubs, the post‐fire increases in resource availability, which enhance growth in the dominant grasses, are also important for recovery of woody species.
Missing fossils, molecular clocks, and the origin of the Melastomataceae
Authors: Morley Robert J. , Dick Christopher W.
Published: February 2008

In a recent analysis of the historical biogeography of Melastomataceae,Renner, Clausing, and Meyer (2001;American Journal of Botany88(7): 1290–1300) rejected the hypothesis of a Gondwana origin. Using a fossil‐calibrated chloroplast DNA (ndhF) phylogeny, they placed the early diversification of Melastomataceae in Laurasia at the Paleocene/Eocene boundary (ca. 55 Ma) and suggested that long‐distance oceanic dispersals in the Oligocene and Miocene (34 to 5 Ma) account for its range expansion into South America, Africa, and Madagascar. Their critical assumption—that oldest northern mid‐latitude melastome fossils reflect tribal ages and their geographic origins—may be erroneous, however, because of the sparse fossil record in the tropics. We show that rates of synonymous nucleotide substitutions derived by theRenner et al. (2001)model are up to three times faster than most published rates. Under a Gondwana‐origin model advocated here, which includes dispersals from Africa to Southeast Asia via the “Indian ark” and emphasizes filter rather than either sweepstakes dispersal or strict vicariance, rates of nucleotide substitution fall within the range of published rates. We suggest that biogeographic reconstructions need to consider the paucity of Gondwanan fossils and that frequently overlooked interplate dispersal routes provide alternatives to vicariance, boreotropical dispersal, and long‐distance oceanic dispersal as explanations for the amphi‐oceanic disjunctions of many tropical rain forest plants.
An ITS phylogeny ofBalsamorhizaandWyethia(Asteraceae: Heliantheae)
Authors: Moore Abigail J. , Bohs Lynn
Published: February 2008

The relationships among the species ofBalsamorhizaandWyethia(Asteraceae: Heliantheae) were examined using data from the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA. The ITS sequences were obtained from nine species ofBalsamorhizaand 14 species ofWyethiaas well as seven outgroup genera. Five of the outgroup genera were members of the subtribe Engelmanniinae of the tribe Heliantheae, the subtribe that includesBalsamorhizaandWyethia. The resulting trees show thatBalsamorhizaandWyethiatogether form a monophyletic group.Balsamorhizaalone is monophyletic, but neither of its two sections is monophyletic.Wyethiais paraphyletic. One group ofWyethiaspecies, including all members of sectionsAlarconiaandWyethiaas well asW. bolanderifrom sectionAgnorhiza, is monophyletic and sister toBalsamorhiza. The other species ofWyethia(all placed in sectionAgnorhiza) are part of a polytomy along with the clade composed ofBalsamorhizaplus the rest ofWyethia.
Endophytic Xylaria (Xylariaceae) among liverworts and angiosperms: phylogenetics, distribution, and symbiosis
Authors: Davis E. Christine , Franklin Joseph B. , Shaw A. Jonathan , Vilgalys Rytas
Published: February 2008

Nuclear ribosomal 18S and internal transcribed spacer (ITS) sequence data were used to identify endophytic fungi cultured from six species of liverworts collected in Jamaica and North Carolina. Comparisons with other published fungal sequences and phylogenetic analyses yielded the following conclusions: (1) the endophytes belong to the ascomycete families Xylariaceae, Hypocreaceae, and Ophiostomataceae, and (2) liverwort endophytes in the genus Xylaria are closely related to each other and to endophytes isolated from angiosperms in China, Puerto Rico, and Europe. Liverwort endophytes are expected to be foragers or endophytic specialists, although little is known about the role of these fungi in symbioses. Features that may indicate a mutualistic role for these endophytes are discussed.
Variation at a chloroplast minisatellite locus reveals the signature of habitat fragmentation and genetic bottlenecks in the rare orchid Anacamptis palustris (Orchidaceae)
Authors: Cozzolino Salvatore , Noce Maria E. , Musacchio Aldo , Widmer Alex
Published: February 2008

Geoclimatic changes during the Oligocene and more recent anthropogenic influences have shaped the current distribution and population structure of Mediterranean plant species. Anacamptis palustris (Orchidaceae) is a typical member of coastal wetlands, which have become increasingly fragmented and isolated. As a consequence, this orchid has become rare in the recent past. Length variation at a chloroplast minisatellite locus was used to estimate genetic variation within and between the largest extant populations of A. palustris. Genetic diversity was positively correlated with population size. Estimation of observed and expected gene diversity and analyses of haplotype number and haplotype frequency distributions provided evidence for population bottlenecks in the history of small populations. Comparison with an earlier study suggests that nuclear allozyme diversity was most likely lost during the Oligocene and could not recover subsequently due to low mutation rates, whereas genetic variation was restored at the highly variable chloroplast minisatellite locus. Population bottlenecks indicated by cpDNA variation occurred most likely as a consequence of more recent anthropogenic changes. The comparison of molecular markers with different levels of polymorphism provided valuable insights into the processes shaping genetic diversity and population structure in this rare orchid.
Analysis of within‐population spatial genetic structure inAntirrhinum microphyllum(Scrophulariaceae)
Authors: Torres Elena , Iriondo José M. , Escudero Adrián , Pérez César
Published: February 2008

Random amplified polymorphic DNA (RAPD) markers were used to study the spatial genetic structure in two populations (Bolarque and Entrepeñas) of endangered cliff specialistAntirrhinum microphyllumRothm. (Scrophulariaceae). Mantel tests found no significant linear correlations between geographic and genetic data. However, redundancy analysis (RDA) models developed using the spatial data as the constraining matrix were highly significant, and spatial data explained 13.6% and 11.1% of total genetic variation in Bolarque and Entrepeñas, respectively. Moran'sIcorrelograms and Mantel correlograms revealed a positive autocorrelation in the first distance class (15 m), which suggests a patchy distribution of genetic diversity. This distribution is consistent with the genetic vicinities that are expected from the territorial behavior of main pollinatorRhodanthidium sticticum(Megachilidae), the predominant short‐distance seed dispersal, and the patchy spatial distribution of available safe sites. The gradient pattern obtained in Entrepeñas was consistent with standard isolation‐by‐distance models. However, a differential sinusoidal pattern was obtained in Bolarque, which would indicate a more frequent gene flow between patches and might be due to lower plant density there. The spatial genetic structure coexists with a strict self‐incompatibility system in the species. Simplified RDA models obtained using a stepwise forward selection comprised the easting component in Entrepeñas and the easting and northing components in Bolarque. Similar results were obtained with directional correlograms. These differential patterns can be explained by the distinct spatial arrangement of the populations (linear and bidimensional in Entrepeñas and Bolarque, respectively).
Effects of inbreeding on male function and self‐fertility in the partially self‐incompatible herb Campanula rapunculoides (Campanulaceae)
Authors: Good‐Avila Sara V. , Nagel Thomas , Vogler Donna W. , Stephenson Andrew G.
Published: February 2008

We examined the effect of inbreeding on fitness (through both male and female functions) and changes in self‐fertility in the partially self‐incompatible species Campanula rapunculoides. Individuals in natural populations of C. rapunculoides varied extensively in their strength of self‐incompatibility (SI). We crossed 11 individuals that differed in their strength of SI to generate families with four levels of inbreeding (f = 0.0, 0.25, 0.5, and 0.75). Progeny were scored for three traits related to male fitness and for outcrossed and selfed seed production. Analyses of variance revealed significant inbreeding depression for the three male traits and seed set. Families with strong or weak SI differed in their response to inbreeding. Families with weak SI had lower levels of inbreeding depression for most traits than families with strong SI, but strong SI families had a greater increase in selfed seed set, but not self‐fertility, with inbreeding. Finally, we found evidence of a significant linear response to inbreeding for all three male reproductive traits and outcrossed seed, indicating that inbreeding depression was primarily caused by partially or fully recessive deleterious alleles. Variation in genetic load was associated with variation in self‐fertility, a finding that suggests an evolutionary role for partial self‐fertility in natural populations of C. rapunculoides.
A new species of Thuja (Cupressaceae) from the Late Cretaceous of Alaska: implications of being evergreen in a polar environment
Authors: LePage Ben A.
Published: February 2008

A branch bearing a number of seed cones of Thuja L. (Cupressaceae) has been recovered from a Late Cretaceous (Turonian) deposit from the North Slope of Alaska. This reproductive material is the oldest known for the genus and is indistinguishable from the seed cones of most of the extant species of Thuja, indicating that the seed cones of this Alaskan fossil Thuja had attained a modern morphological appearance early in the evolutionary history of the genus. From a physiological standpoint, the ability of modern species of Thuja to tolerate cold to freezing conditions and the ability of fossil representatives of the genus to survive periods of extended darkness during the polar winters supports the contention that the polar winters during the Late Mesozoic and early Cenozoic were cold.
Shoot morphogenesis associated with flowering in Populus deltoides (Salicaceae)
Authors: Yuceer Cetin , Land Samuel B. , Kubiske Mark E. , Harkess Richard L.
Published: February 2008

Temporal and spatial formation and differentiation of axillary buds in developing shoots of mature eastern cottonwood (Populus deltoides) were investigated. Shoots sequentially initiate early vegetative, floral, and late vegetative buds. Associated with these buds is the formation of three distinct leaf types. In May of the first growing season, the first type begins forming in terminal buds and overwinters as relatively developed foliar structures. These leaves bear early vegetative buds in their axils. The second type forms late in the first growing season in terminal buds. These leaves form floral buds in their axils the second growing season. The floral bud meristems initiate scale leaves in April and begin forming floral meristems in the axils of the bracts in May. The floral meristems subsequently form floral organs by the end of the second growing season. The floral buds overwinter with floral organs, and anthesis occurs in the third growing season. The third type of leaf forms and develops entirely outside the terminal buds in the second growing season. These leaves bear the late vegetative buds in their axils. On the basis of these and other supporting data, we hypothesize a 3‐yr flowering cycle as opposed to the traditional 2‐yr cycle in eastern cottonwood.
The cost of inbreeding inPlatanthera leucophaea(Orchidaceae)
Authors: Wallace Lisa E.
Published: February 2008

Fragmentation and isolation are expected to have a considerable impact on viability and recruitment in populations of rare species.Platanthera leucophaea(Orchidaceae), a rare orchid, currently exists in a fragmented landscape of its natural habitat. Floral morphology suggests this species is predominantly outcrossing, but surveys of allozyme diversity suggest high, variable levels of inbreeding in populations (FIS= −0.078 to 1.0). This study examines the potential cost of inbreeding and the extent to which inbreeding depression can vary temporally and in populations of different size and genetic structure. Flowers were pollinated by hand in one large population and one small population over three seasons. Seed set, seed mass, and seed viability were compared among self‐, outcross‐, and open‐pollinated fruits. Seed set was greater than 50% in both populations for all years of study. High levels of inbreeding depression were detected in seed viability but not in seed mass in both populations. However, the magnitude of inbreeding depression differed over years and between populations, a pattern that reflects differing environmental conditions and variable evolutionary and demographic histories. Consequently, conservation of this species will be most successful if outcrossing is promoted in populations by maximizing population size and genetic variability.
Effects of tree crown structure on biomass of the epiphytic fern Polypodium scouleri (Polypodiaceae) in redwood forests
Authors: Sillett Stephen C. , Bailey Mark G.
Published: February 2008

Redwood forests contain some of the largest and most structurally complex trees on Earth. The most abundant vascular epiphyte in these forests is the fern Polypodium scouleri (Polypodiaceae). We measured dimensions of all 765 P. scouleri mats on 32 trees (27 Sequoia sempervirens, 5 Picea sitchensis). Eighteen P. scouleri mats from 11 trees were randomly selected for removal and dissection in the laboratory. The total fern mat mass consisted of live fronds (3.3%), dead fronds (2.4%), live rhizomes (4.2%), dead rhizomes (8.9%), roots (34.4%), humus (28.0%), and debris (18.8%). We used multiple regression analysis to develop equations for estimation of fern masses, and we applied these equations to undisturbed fern mats on the 32 trees. Individual trees supported up to 742 kg dry mass of P. scouleri mats. These are the highest whole‐tree epiphyte masses ever reported. We also quantified crown structure and counted the number of vascular plant species occurring as epiphytes on each tree. Very large, complex trees had more fern mat mass and higher vascular epiphyte species richness than smaller, simpler trees. Desiccation‐sensitive organisms dependent on water stored in fern mats may be unable to survive in managed redwood forests lacking large, complex trees with abundant P. scouleri.
A mixed strategy in the annual endemicAster laurentianus(Asteraceae)—a stress‐tolerant, yet opportunistic species
Authors: Houle Gilles , Valéry Sébastien
Published: February 2008

Several environmental factors influence the distribution of plants in coastal salt marshes. Substrate salinity is among the major factors preventing several species from establishing near the water line. However, interspecific competition for light and nutrients is often significant in determining the upper limit of plants along the salt marsh gradient. In this study, we tested the effects of substrate salinity and light and nutrient availability on the performance of the annualAster laurentianus(Asteraceae), an endangered species of eastern Canadian salt marshes. This species is typically found in a narrow band along the shores of shallow lagoons, cornered between the high water line and the dense, herbaceous community of the upper marsh. Low light availability was the most significant factor limiting plant performance. Salinity had little effect onA. laurentianusas, unexpectedly, did nutrient availability. Yet plants were able to absorb nutrients when these were made more available. Luxury consumption, the uptake of excess nutrients, may make sense for this annual plant because the habitat in which it grows is subject to frequent disturbances (e.g., sand accretion and salinity pulses) that may kill canopy species and release suppressedA. laurentianusindividuals. These results suggest that interspecific competition for light may play a significant role in restrainingA. laurentianusfrom the upper part of salt marshes. Luxury consumption may help the species to opportunistically take advantage of release from taller species, particularly towards the upper edge of the salt marsh gradient.
Phylogenetic relationships in Gleditsia (Leguminosae) based on ITS sequences
Authors: Schnabel Andrew , McDonel Patrick E. , Wendel Jonathan F.
Published: February 2008

We used nucleotide sequences from the internal transcribed spacers and 5.8S gene of nuclear ribosomal DNA to test competing phylogenetic and biogeographic hypotheses in Gleditsia. Eleven of 13 Gleditsia species were sampled, along with two species of its sister genus, Gymnocladus. Analyses of ITS data and of a combined data set that included sequences of ITS and two chloroplast genes supported several conclusions that were interpreted in light of fossil data and current legume phylogeny. Gleditsia and Gymnocladus appear to have originated in eastern Asia during the Eocene. Eastern North American species of both genera most likely evolved from ancestors that migrated across the Bering land bridge, but the eastern Asian/eastern North American disjunction appears to be much older in Gymnocladus than in Gleditsia. Gleditsia amorphoides, from temperate South America, is sister to the rest of the genus, suggesting early long‐distance dispersal from Asia. The remainder of Gleditsia is divided into three unresolved clades, possibly indicating a split early in the evolution of the genus. Two of those clades contain only Asian species, and one contains Asian and North American species. The North American species, Gleditsia triacanthos and Gleditsia aquatica, are polymorphic and paraphyletic with respect to their ITS and cpDNA sequences, which suggests recent diversification.
Phylogenetic position and generic differentiation of Epithemateae (Gesneriaceae) inferred from plastid DNA sequence data
Authors: Mayer Veronika , Möller Michael , Perret Mathieu , Weber Anton
Published: February 2008

The systematic position and generic differentiation of the morphologically and geographically outstanding tribe Epithemateae (Gesneriaceae) was analyzed using the rbcL/atpB‐spacer and trnL‐F intron‐spacer regions of chloroplast DNA. In our analysis Epithemateae forms a strongly supported monophyletic clade (bootstrap [BS] = 100%; jackknife [JK] = 100%; decay index [DI] = 12) and appears as sister to the rest of the paleotropical Gesneriaceae (= subfamily Cyrtandroideae). The paleotropical Gesneriaceae form a monophyletic group (BS = 88%; JK = 85%; DI = 3) that is sister to the neotropical Gesneriaceae (subfamily Gesnerioideae) plus Austral Gesneriaceae (subfamily Coronantheroideae) (BS = 99%; JK = 98%; DI = 10). Within Epithemateae Rhynchoglossum is sister to the remaining Epithemateae (BS = 97%; JK = 96%; DI = 12), in which Epithema is sister to a clade of two genera: Loxonia/Stauranthera (BS = 68%; JK = 64%; DI = 1), which form, together with Epithema, a sister clade (BS = 85%; JK = 83%; DI = 2) to Whytockia and Monophyllaea. While the support for Loxonia and Stauranthera is moderate, the relationship of Whytockia and Monophyllaea is very strongly supported (BS = 100%; JK = 100%; DI = 13). Apart from the somewhat surprising (but well‐substantiated) isolated position of Rhynchoglossum, the results are in perfect accordance with the relationships worked out earlier on grounds of architectural and floral characters. Especially remarkable is the predicted coherence between the morphologically and geographically different genera Whytockia and Monophyllaea.
Geographic patterns in the reproductive ecology of Agave lechuguilla (Agavaceae) in the Chihuahuan desert. I. Floral characteristics, visitors, and fecundity
Authors: Silva‐Montellano Arturo , Eguiarte Luis E.
Published: February 2008

Floral characteristics such as morphology and flower color have been interpreted as adaptive traits that evolved through selective pressures generated by pollinators. Differences among populations in the expression of floral characters could result from natural selection for their adaptive value to local conditions. We describe the patterns of variation of flower morphology, color, and fecundity of Agave lechuguilla in 11 populations along a latitudinal gradient encompassing the whole range of the species in the Chihuahuan desert. We found a latitudinal pattern in flower shape and color. Flowers tended to be shorter, more open, and colorful toward the northern part of the gradient. We also recorded flower visitation, discriminating between pollinators and floral robbers. The main pollinators seems to be nocturnal hawk moths (Hyles lineata) and diurnal large bees (Bombus pennsylvanicus and Xylocopa californica). In all populations large bees were the most abundant potential pollinators. However, the abundance of the potential pollinators varied along the gradient. We observed no bat visits along the gradient. The number of visits by all potential pollinators decreased significantly with latitude as did fruit set.
Seedling competition between native Populus deltoides (Salicaceae) and exotic Tamarix ramosissima (Tamaricaceae) across water regimes and substrate types
Authors: Sher Anna A. , Marshall Diane L.
Published: February 2008

Populus deltoides subsp. wislizinii (Salicaceae), a cottonwood native to the Middle Rio Grande of New Mexico, must potentially compete against exotic Tamarix ramosissima (Tamaricaceae) during establishment after flooding. We investigated competitive interactions between seedlings of Tamarix and Populus in two substrates representing field textures and declining (i.e., draw‐down) or stagnant water tables. The experiment was performed using a full‐additive series design and interpreted with response surface models for each species. As reflected in both aboveground mass and height, Populus suppressed aboveground growth of Tamarix across all treatments, whereas competitive effects of Tamarix against Populus could only be seen at low Populus densities. Clay substrates with draw‐down stimulated the greatest growth and created the most intense competitive environment for both species. Tamarix was competitively suppressed in every substrate tested, with the weakest response in sand with no draw‐down, where growth of Populus was poorest. These results suggest that stream flow management that promotes Populus establishment could also aid in controlling Tamarix invasion across a range of substrates.
Reexamination of relationships, habital evolution, and phylogeography of checker mallows (Sidalcea; Malvaceae) based on molecular phylogenetic data
Authors: Andreasen Katarina , Baldwin Bruce G.
Published: February 2008

Phylogenetic analysis of nuclear ribosomal DNA external and internal transcribed spacer region (ETS and ITS) sequences for Sidalcea (Malvaceae) resolved five major, well‐supported lineages, three of which represent species groups that have each been noted for complex patterns of morphological variation: the oregana, malviflora, and glaucescens clades. Very low variation within each of the three groups in the sequenced regions is consistent with recent radiation of each clade. We reject the previously suggested hypothesis of monophyly for the annual species of Sidalcea. Based on our findings, the annual habit in Sidalcea arose at least four times, probably as an adaptation to seasonally dry habitats. The hypothesis that the perennial species S. hickmanii and S. malachroides represent basally divergent groups within Sidalcea is supported, but the more recently discovered S. stipularis represents an additional basally divergent lineage. The previous suggestion that the genus spread northward from Mexico along two major routes (through the Rocky Mountains and the Sierra Nevada foothills), with the Rocky Mountain species S. candida and S. neomexicana representing basally divergent lineages, is not supported. Sidalcea neomexicana is nested within the malviflora clade and is likely a lineage of relatively recent descent that originated in California and subsequently spread to the Rocky Mountains.
The wandering carpel mutation of Zea mays (Gramineae) causes misorientation and loss of zygomorphy in flowers and two‐seeded kernels
Authors: Irish Erin E. , Szymkowiak Eugene J. , Garrels Kathryn
Published: February 2008

We have isolated a new mutation, wandering carpel (wcr), which affects polarity of the maize flower, altering its orientation or converting it from zygomorphy to radial symmetry. These changes result in the development of embryos on locations other than the normal, acropetal side of the kernel. More than two carpels can develop into silks. More rarely, two ovules develop in a single ovary, giving rise to kernels with two seeds. The wcr mutation is a maternal‐sporophyte‐effect, semidominant mutation whose expression is background dependent. As spikelets with abnormal flowers are almost always paired with a normal spikelet, we hypothesize that WCR+ is required for establishing polarity in spikelet meristems during inflorescence development.
Diversification of andromonoecy in Solanum section Lasiocarpa (Solanaceae): the roles of phenotypic plasticity and architecture
Authors: Miller Jill S. , Diggle Pamela K.
Published: February 2008

Quantitative analyses of sexual expression show extensive interspecific variation in the strength of andromonoecy (proportions of hermaphroditic and staminate flowers) among Solanum species in the monophyletic section Lasiocarpa. The roles of phenotypic plasticity and inter‐ and intra‐inflorescence architecture in the diversification of andromonoecy within this small clade were analyzed. Four species that represent a range of expression of andromonoecy were examined. Staminate flowers produced within inflorescences ranged from 3% (S. candidum) to 7% (S. ferox) in weakly andromonoecious species and from 39% (S. pseudolulo) to 60% (S. quitoense) in more strongly andromonoecious species. Manipulation of fruit set on clonal replicates of multiple genotypes demonstrated variation among species for phenotypic plasticity. The strongly andromonoecious species, S. pseudolulo and S. quitoense, were not plastic and produced a large proportion of staminate flowers regardless of fruiting treatment, whereas S. candidum and S. ferox were phenotypically plastic and produced significantly more staminate flowers in the presence of developing fruit. Staminate flower production of all four species varied both within and among inflorescences. A greater proportion of staminate flowers were produced in distal (later produced) inflorescences. Within inflorescences, hermaphroditic flowers occurred in basal positions, whereas staminate flowers, when produced, occurred more distally. This pattern of staminate flower production is qualitatively the same in all species investigated; however, quantitative variation in the transition from hermaphroditic to staminate flower production within and among inflorescences is associated with variation in the strength of andromonoecy. At least three factors have contributed to the diversification of andromonoecy in section Lasiocarpa including the presence or absence of phenotypic plasticity in response to fruit set, quantitative variation in intra‐ and inter‐inflorescence architectural effects, and total flower production.
Low selfing in a mass‐flowering, endangered perennial, Eryngium alpinum L. (Apiaceae)
Authors: Gaudeul Myriam , Till‐Bottraud Irène
Published: February 2008

We investigated the reproductive ecology of an endangered alpine species, Eryngium alpinum L., to determine its selfing rate and to propose possible mechanisms that may shape its breeding system. Whereas pollinators' foraging behavior suggested a high potential for geitonogamy (70% of the flights occur within plants), microsatellite analyses of seed progenies demonstrated that plants are primarily outcrossing (outcrossing rate [tm] = 0.65, 0.96, and 1 in three populations). Given the relatively long pollen viability (at least 4–5 d) and the high number of simultaneously opened flowers on each plant, protandry is not sufficient to eliminate selfing. Second, controlled crosses demonstrated not only auto‐fertility, but also partial self‐incompatibility. Partial self‐incompatibility is probably due to the competitive advantage of cross vs. self‐pollen, and, together with protandry, could lead the species to selfing as a reproductive assurance. These results are encouraging for the maintenance of large populations. However, higher selfing was observed in a small population that could suffer inbreeding depression, as observed on experimentally selfed seeds. Thus, these populations should be carefully monitored. Finally, this study shows how molecular markers and field experiments may complement each other in our reaching a global understanding of mating patterns.
Cyathea cranhamii sp. nov. (Cyatheaceae), anatomically preserved tree fern sori from the Lower Cretaceous of Vancouver Island, British Columbia
Authors: Smith Selena Y. , Rothwell Gar W. , Stockey Ruth A.
Published: February 2008

Permineralized cyatheaceous sori occur among remains of conifers, fungi, and other plants in newly discovered calcareous concretions from Early Cretaceous (Barremian) marine sediments of Vancouver Island, British Columbia, Canada. Sori are superficially attached in two rows to narrow pinnules and display a globose sphaeropteroid indusium. Annulate sporangia with multicellular stalks diverge from a basal, vascularized receptacle. The nearly vertical uniseriate annulus is not interrupted by the stalk. The sporangia bear 64 trilete spores with perispore sculpturing that ranges from irregular granulate/echinate to prominent rodlets. These specimens, described as Cyathea cranhamii sp. nov., are the first anatomically preserved tree fern sori from the fossil record. They represent the most ancient evidence for fertile structures of the Cyatheaceae and demonstrate that essentially modern species of cyatheaceous tree ferns had evolved by the Early Cretaceous.
Comparative development of aseptate and septate anthers of Annonaceae
Authors: Tsou Chih‐Hua , Johnson David M.
Published: February 2008

We compared anther development in 13 genera and 15 species of Annonaceae to document the nature and development of anther septa. In aseptate anthers, all sporogenous initials proceed to sporogenesis and meiosis. In septate anthers, a small number of sporogenous initials, in a discontinuous distribution pattern, differentiate into sporogenous cells; the remaining initials become sterile and form cellular septa that partition each anther lobe into multiple sporangial chambers. In species where the septum is 1–2 cell layers thick, the entire septum becomes tapetal (T‐type septa) and breaks down before anther dehiscence. In species in which the septum is three or more cell layers thick, only the layer in direct contact with the sporogenous cells becomes tapetal, and the remaining cells become parenchymatous (P‐type septa). These thicker P‐type septa are sometimes visible in dehisced anthers. Both types are homologous in ontogeny and are highly associated with the production of compound pollen. We propose that the evolution of anther septation in Annonaceae was mainly driven by the requirement for highly efficient nutrient and physical support to the development of large, compound pollen units.
Phylogeography of the Arctic‐Alpine Saxifraga oppositifolia (Saxifragaceae) and some related taxa based on cpDNA and ITS sequence variation
Authors: Holderegger Rolf , Abbott Richard J.
Published: February 2008

Saxifraga oppositifolia (Saxifragaceae) is an important model system for the evolution of Arctic‐Alpine plant species. Sequences of the psbA–trnH intergenic spacer of chloroplast DNA and of the internal transcribed spacer region, ITS1–5.8S–ITS2, of the nuclear ribosomal DNA were used to investigate the intraspecific evolution and phylogeography of this species. Samples from nearly the species' entire circumpolar distribution were included in the analysis as well as samples from the closely related taxa S. smalliana from Alaska and S. blepharophylla and S. biflora from the Alps (S. aizoides served as outgroup). These latter taxa showed a low number of parsimony informative characters, in both cpDNA and ITS sequences, which separated them from S. oppositifolia. Two main cpDNA haplotypes were detected within S. oppositifolia, one with a Eurasian distribution and one with an East Asian‐North American distribution. This confirmed the existence of two cpDNA lineages with different geographical distributions in this species, which had previously been reported based on a RFLP analysis. The ITS phylogeny was not useful with respect to the intraspecific evolution and phylogeography of S. oppositifolia, because it showed a largely unresolved topology with low statistical support. The cpDNA sequence analysis, however, also suggested a putative long‐distance dispersal event. All investigated taxa had cpDNA haplotypes that were congruent with their geographical origin rather than their phylogeny. This could point to putative lineage sorting in S. oppositifolia and related taxa.
Development of ovule, embryo sac, and endosperm in Triteleia (Themidaceae) relative to taxonomy
Authors: Berg Rolf Y.
Published: February 2008

Six of 14 species of Triteleia were studied. All possess septal nectaries, raphides in the ovary wall, an anatropous and crassinucellate ovule with a micropyle formed by the inner integument only, and parietal cells. A short and thick nucellus, which is not penetrated by the embryo sac, has a one‐layered apical epidermis and thickens from its subepidermal layer. The permanently two‐layered inner integument is made up of normal, i.e., not greatly enlarged, cells. The embryo sac is of the Polygonum type, and the endosperm is of the helobial type. Embryo development is of the Asterad type in Triteleia laxa and T. ixioides. From an embryological point of view, Triteleia is closely related to Muilla maritima because the two taxa are alike in all characteristics, except for the number of layers in the apical nucellar epidermis. Triteleia is only distantly related to Dipterostemon, Dichelostemma, and Brodiaea, judging from the numerous differences in embryology. Both Triteleia and Muilla maritima are embryologically more primitive than the Dipterostemon‐Dichelostemma‐Brodiaea group. Embryologically, the Themidaceae are more similar to the Hyacinthaceae than to Allium. However, all embryological similarities with Hyacinthaceae are in plesiomorphic characters.
First fossil record of transfer cells in angiosperms
Authors: Gottschling Marc , Hilger Hartmut H.
Published: February 2008

Transfer cells are specialized plant cells that optimize short‐distance transport by an extension of the interior surface of the cell walls. Using scanning electron microscopy (SEM), we found transfer cells in the fossil seed coat of Ehretia clausentia (Ehretiaceae, Boraginales) from the London Clay flora (Lower Eocene). This is the first fossil record of transfer cells in angiosperms.
Facilitated selfing offers reproductive assurance: a mutualism between a hemipteran and carnivorous plant
Authors: Anderson Bruce , Midgley Jeremy J. , Stewart Barbara A.
Published: February 2008

Reproductive assurance is frequently used to explain the evolution of selfing but has become controversial from lack of evidence. We studied the pollination system of the near carnivorous plant genus Roridula and showed that reproductive assurance is important in this system. Hemipterans have a digestive mutualism with Roridula and have been implicated in pollination but flowers show adaptations to hymenopteran pollination. We deduce that hemipterans are the primary pollinators of Roridula because seed set is significantly reduced when hemipterans are excluded from the flowers. Using allozyme electrophoresis, we show that hemipterans are responsible for mostly selfed progeny. Although bees still pollinate Roridula on very rare occasions, their exclusion does not affect seed set. The complicated floral structures that occur in Roridula most likely evolved as adaptations for bee pollination. Resident hemipterans facilitate selfing by Roridula, and this acts as a reproductive assurance mechanism because it increases seed production and ensures that plants still reproduce in the absence of more motile, outcrossing pollinators.
Temporal and spatial patterns of mass flowerings on the Malay Peninsula
Authors: Numata Shinya , Yasuda Masatoshi , Okuda Toshinori , Kachi Naoki , Noor Nur Supandi Md.
Published: February 2008

We propose a hypothesis to explain the temporal and spatial patterns of mass flowerings in dipterocarp tree species on the Malay Peninsula. The literature on these mass flowerings reveals that during 1980–2002 at least 11 flowerings occurred at irregular intervals of 1–6 yr in a lowland rain forest. Five of them were typical mass flowerings—a high density of flowering trees and the characteristic sequential flowering of Shorea species. The 11 flowerings were classified into two flowering times: spring and autumn. There is evidence that low temperature and drought triggered the flowerings. Therefore, the seasonality of mass flowerings is characterized by the annual patterns of rainfall and low temperature. In addition, changes in El Niño–Southern Oscillation (ENSO) may play important roles in determining the supra‐annual occurrence of mass flowerings. Flowering surveys on the Malay Peninsula implied that regions with spring or autumn mass flowerings corresponded geographically to those regions that had one cool season (December–February) or two (December–February and June–August), respectively. This finding anticipates the seasonal pattern and geographical distribution of mass flowerings on the Malay Peninsula.
Phylogenetic relationships in Cyperaceae subfamily Mapanioideae inferred from pollen and plastid DNA sequence data
Authors: Simpson David A. , Furness Carol A. , Hodkinson Trevor R. , Muasya A. Muthama , Chase Mark W.
Published: February 2008

Cyperaceae are the third largest monocotyledon family, with considerable economic and conservation importance. In subfamily Mapanioideae there is particular specialization of the inflorescence into units termed spicoids. The structural homology of the spicoid is difficult to interpret, making determination of intrafamilial relationships problematic. To address this, pollen from eight species in Mapanioideae was investigated using light microscopy and scanning and transmission electron microscopy. Pollen development was also examined to identify the type of pollen present in these species. We also analyzed DNA sequence data using the trnL‐F and rps16 regions from 25 genera and 35 species of Cyperaceae, Juncaceae, and Thurniaceae. Two types of pollen, Mapania‐type and pseudomonad, were identifed. Analysis of combined DNA and pollen data resolved a clade sister to the rest of Cyperaceae, corresponding to Mapanioideae. Within this, two further clades were resolved. One comprised taxa assigned to tribe Hypolytreae, which had Mapania‐type pollen. The other comprised taxa mainly assigned to tribe Chrysitricheae, but included two taxa from Hypolytreae, Capitularina and Exocarya. All taxa in this clade had pseudomonad pollen. Thus new groupings within the subfamily have been discovered based on the specialization of some taxa in terms of their pollination biology.
Dispersal biology of Liatris scariosa var. novae‐angliae (Asteraceae), a rare New England grassland perennial
Authors: Gravuer Kelly , von Wettberg Eric J. , Schmitt Johanna
Published: February 2008

Propagule dispersal biology is a crucial avenue of research for rare plant species, especially those adapted to disturbance, such as northern blazing star (Liatris scariosa var. novae‐angliae), a rare, early‐successional New England grassland perennial. We examined the dispersal ability of northern blazing star propagules collected from 14 populations covering the entire latitudinal range of the taxon. Multiple regression demonstrated that dispersal ability, as measured by drop time in still air and flight distance in a low‐speed wind tunnel, decreased significantly with propagule size and achene length, and increased with achene width and (for flight distance) pappus length. We used this multiple regression model to test for differences in predicted dispersal capability among maternal families, populations, and inland, coastal, and island habitats. Dispersal capability differed significantly among families and populations but not regions, and allometric relationships between morphological measurements were consistent across populations. Overall, dispersal capability was negatively correlated with germination success in a common greenhouse environment. However, germination success for a given dispersal ability, as well as achene shape, differed among populations. These results suggest specific populations to be targeted for management efforts promoting dispersal and establishment.