bluuebunny/crossref_metadata_2025 huggingface dataset:
Resorption of thoracic disc herniation
Authors: Haro Hirotaka , Domoto Toru , Maekawa Shingo , Horiuchi Tadahiro , Komori Hiromichi , Hamada Yoshiki
Published: February 2008

✓The authors describe 2 cases of thoracic disc herniation, resulting in acute myelopathy without bladder dysfunction or progressive muscular weakness; the herniated disc apparently resorbed without surgical intervention. Thoracic disc herniations are less frequent than cervical or lumbar disc herniations and are usually associated with severe neurological deficits. In these 2 cases, the herniated discs exhibited marked decreases in size, corresponding to a favorable clinical outcome within a few months after the initiation of conservative treatment with prostaglandin E1 and/or steroids in conjunction with physical therapy. The authors conclude that thoracic herniated discs are capable of undergoing natural resorption and that conservative treatment could be indicated, even in the presence of moderate myelopathy, when the myelopathy is not accompanied by bladder dysfunction or progressive muscular weakness.
The effects of ultraviolet‐B radiation and intraspecific competition on growth, pollination success, and lifetime female fitness in Phacelia campanularia and P. purshii (Hydrophyllaceae)
Authors: Conner Jeffrey K. , Neumeier Rachel
Published: February 2008

While a considerable amount of attention has been devoted to the effects that increased ultraviolet‐B (UV‐B) radiation has on vegetative plant growth and physiological function, the impact that UV‐B may have on plant fitness has been the focus of fewer studies, with attention given primarily to a few crop species. Further, the possible interactions between UV‐B and additional potential stresses found in natural environments have rarely been studied experimentally. Because the reported effects of increased UV‐B on plant growth and fitness have been highly variable, studies that focus on factors that may lead to these differences in results are important for the formulation of accurate predictions about future plant success under varying UV‐B levels. We examined the effects of UV‐B dose and intraspecific competition on growth, phenology, pollen production, pollination success, fruit and seed production, and offspring quality in two species of Phacelia. Increased UV‐B was neutral or beneficial for all traits, while competition was neutral or detrimental. There were no significant interactions between UV‐B and competition in the parental generation. Phacelia campanularia offspring were unaffected by parental competition, but derived indirect beneficial effects on germination, growth, and fitness traits from parental enhanced UV‐B.
Post‐fire recovery of acorn production by four oak species in southern ridge sandhill association in south‐central Florida
Authors: Abrahamson Warren G. , Layne James N.
Published: February 2008

We examined post‐fire recovery of two components of acorn production (percentage of bearing ramets [stems] and number of acorns per bearing ramet) for four species of oaks in southern ridge sandhill vegetation in south‐central peninsular Florida. Annual counts of acorns on two white oaks (Quercus chapmanii and Q. geminata) and two red oaks (Q. laevis and Q. myrtifolia) were conducted annually (except in 1991) on two 2.7‐ha grids from 1969 to 1998. A prescribed burn was conducted on one of the grids in May 1993. Newly sprouted ramets of both white oaks produced acorns during the first year following the fire, whereas red oaks required 3 yr (Q. myrtifolia) or 4 yr (Q. laevis) to produce acorns. The difference in the timing of post‐fire acorn production between the white and red oak species reflected the difference in the number of years from flower bud initiation to mature acorns in the two groups, with the additional year‐long lag in Q. laevis probably attributable to the fact that it is typically a tree rather than a shrub species. The data suggested that percentage of bearing ramets in the smallest size class of the two white oak species was markedly lower in the burned than unburned grid in the first year of post‐fire acorn production and higher in the fifth year, but these trends were not evident for the red oaks. Among all four species, differences between mean number of acorns in burned and unburned grids were significant in only two cases (the largest size class of both white oak species in the fifth year). There was no evidence of recruitment from acorns on the burned grid, possibly due to the rapid redevelopment of the shrub layer because of low mortality of the extensive clonal root systems. Rapid post‐fire recovery of acorn production in xeric fire‐prone habitats is presumably the result of selection to increase the probability of recovery and persistence following sufficiently intense fires that result in high oak mortality. The timing and magnitude of post‐fire acorn production in sandhill and other xeric Florida associations has a potential impact on a wide variety of insects, birds, and mammals that feed on acorns, as well as on the species with which they interact.
Many to flower, few to fruit: the reproductive biology of Hamamelis virginiana (Hamamelidaceae)
Authors: Anderson Gregory J. , Hill James D.
Published: February 2008

Hamamelis virginiana flowers from late September to late November. In 1977, we began studying the reproductive biology of this eastern North American arborescent shrub by examining floral phenology and rewards, pollen‐ovule ratios, breeding system, pollination, pollinator and resource limitation, and seed dispersal. The homogamous, self‐incompatible flowers emit a faint odor, bear nectar with sucrose ratios typical of bee‐ and fly‐pollinated flowers, and produce abundant sticky pollen. Flowers were visited infrequently by insects representing six orders. Flies were the most common floral visitors, specifically members of the genus Bradysia, but small bees also carried high percentages of Hamamelis pollen. Despite high pollen/ovule ratios (11 445 grains/ovule), bees and flies are likely pollinators, as experiments indicate wind pollination is less likely. Pollen quantity and resource availability did not appear to limit reproductive output, but pollen quality did. Tests of >40 000 flowers showed natural fruit set to be <1%. The flowering time, breeding system, and clumped distribution of plants, likely due in part to limited seed dispersal, combine to yield this remarkably low fruit set. Because all other species of Hamamelis flower from late winter to early summer, it may be that H. virginiana evolved a fall flowering phenology to avoid competition for pollinators with the closely related H. vernalis.
Temporal changes in floral nectar production, reabsorption, and composition associated with dichogamy in annual caraway (Carum carvi; Apiaceae)
Authors: Langenberger Michael W. , Davis Arthur R.
Published: February 2008

The dynamics of nectar production were studied in perfect florets of two varieties (Karzo, Moran) of annual caraway (Carum carvi L., Apiaceae). Florets were protandrous and strongly dichogamous, lasting 7–15 d but producing nectar from the stylopodia for 4–12 d, in an interrupted fashion. Nectar secretion began during a floret's phase of stamen elongation and anther dehiscence. After reabsorption of uncollected nectar, at which point nectary surfaces were completely dry, the two styles elongated and a second bout of secretion commenced during the female phase, up to 5 d later, when a floret became receptive to pollination. During the male and female phases, respectively, 0.392 ± 0.064 μL and 1.083 ± 0.261 μL of nectar of similar solute concentration (844 mg/mL) was produced per ten florets. On a daily basis, florets yielded 1.5‐fold more nectar in the female than during the male phase. First‐time nectar removal throughout the female phase did not match the sum of nectar quantities from male and female phases combined, suggesting that under natural conditions, any uncollected male‐phase nectar, once reabsorbed, is not made available to visitors of the same florets when in the female phase. Nectar‐sugar composition differed between bouts of secretion; it was hexose‐rich (59.6% fructose, 26.9% glucose, 13.6% sucrose) initially, but hexose‐dominant (70.2, 26.8, 3.1) during the female phase. A 5.7‐fold difference in mean nectar production per floret occurred among plants.
Recruitment potential of two perennial grasses with different growth forms at a semiarid‐arid transition zone
Authors: Peters Debra P. C.
Published: February 2008

The objective of this study was to quantify differences in recruitment potential (seed production, seed presence in the soil) for two congeneric perennial grasses (Bouteloua gracilis, Bouteloua eriopoda [Poaceae]) that dominate adjacent arid and semiarid grassland biomes. It was hypothesized that these species have different recruitment strategies at the biome transition zone that are related to differences in their growth form and longevity. Recruitment potential for each Bouteloua species was compared in patches dominated by one or both species or codominated by the invasive shrub, Larrea tridentata (Zygophyllaceae). Regional variation in recruitment was examined for B. gracilis for cases in which comparable data were available in the literature for a site located within the semiarid grassland biome. The short‐lived stoloniferous species B. eriopoda produced more seeds per plant than the long‐lived bunchgrass B. gracilis, yet seed viability (<60%) and presence in the soil were lower. Mean viability of B. gracilis was higher (>90%) than that of B. eriopoda, and a greater percentage of seeds produced on a square meter basis was found in the soil (10–25%). Similar patterns were found for both species in all grass‐dominated patches. Bouteloua eriopoda plants growing in patches codominated by L. tridentata produced fewer seeds per plant with lower viability, and fewer seeds were found in the soil compared to grass‐dominated patches. Regional comparisons found greater seed production per square meter and more seeds in the soil for B. gracilis at the transitional site compared with a cooler, wetter site located within the semiarid grassland biome. These differences in recruitment potential along with published differences in rates of seedling establishment and vegetative spread may explain, at least in part, localized patterns in species dominance.
Occurrence and phylogenetic significance of latex in the Malpighiaceae
Authors: Vega Andrea S. , Castro Maria A. , Anderson William R.
Published: February 2008

Latex and laticifers are reported for the first time in the genera Galphimia and Verrucularia (Malpighiaceae), with description and illustration of the leaf and stem anatomy of both genera. Those genera and the other two in which latex is known (Lophanthera and Spachea) constitute a single tribe, Galphimieae, that is at or near the base of the family's phylogeny, which suggests that latex in the Malpighiaceae may indicate an ancestor shared with the Euphorbiaceae.
Additional observations on Rhynchosperma quinnii (Medullosaceae): a permineralized ovule from the Chesterian (Upper Mississippian) Fayetteville Formation of Arkansas
Authors: Dunn Michael T. , Rothwell Gar W. , Mapes Gene
Published: February 2008

New ovules from the Fayetteville Formation (Upper Mississippian) of Arkansas expand our knowledge of the morphology and anatomy of Rhynchosperma and suggest it was produced by a medullosan seed fern. Rhynchosperma has been described as radially symmetrical with a two‐layered integument and vascularization in the integument only. The apical portion of the integument is ribbed; the nucellus is fused to the integument and apically differentiated into a dome‐shaped pollen chamber. The vascular system is incompletely known and apparently restricted to the base of the integument. The new specimens are like Rhynchosperma in external shape, size, number of ribs, and numerous histological features. However, new data reveal that the nucellus is vascularized by a sheath of tracheids, the integument is vascularized by discrete bundles, the pollen chamber has a nucellar beak, and the nucellus is attached to the integument for a variable distance from the base. In addition, the integument is tripartite with an elaborate apical region; ribs formed by the integument are more pronounced at the apex; and internally open, hollow lobes form a stellate micropylar canal. The presence of a tripartite integument, the nature of the vascular system, the nucellus‐integument attachment, the pollen chamber structure, symmetry, and the association with medullosan vegetative remains suggest medullosan affinity for these ovules and strengthens the evidence for the origin of the family before the end of the Lower Carboniferous.
Molecular data place Hydnoraceae with Aristolochiaceae
Authors: Nickrent Daniel L. , Blarer Albert , Qiu Yin‐Long , Soltis Douglas E. , Soltis Pamela S. , Zanis Michael
Published: February 2008

Utilization of molecular phylogenetic information over the past decade has resulted in clarification of the position of most angiosperms. In contrast, the position of the holoparasitic family Hydnoraceae has remained controversial. To address the question of phylogenetic position of Hydnoraceae among angiosperms, nuclear SSU and LSU rDNA and mitochondrial atp1 and matR sequences were obtained for Hydnora and Prosopanche. These sequences were used in combined analyses that included the above four genes as well as chloroplast rbcL and atpB (these plastid genes are missing in Hydnoraceae and were hence coded as missing). Three data sets were analyzed using maximum parsimony: (1) three genes with 461 taxa; (2) five genes with 77 taxa; and (3) six genes with 38 taxa. Analyses of separate and combined data partitions support the monophyly of Hydnoraceae and the association of that clade with Aristolochiaceae sensu lato (s.l.) (including Lactoridaceae). The latter clade is sister to Piperaceae and Saururaceae. Despite over 11 kilobases (kb) of sequence data, relationships within Aristolochiaceae s.l. remain unresolved, thus it cannot yet be determined whether Aristolochiaceae, Hydnoraceae, and Lactoridaceae should be classified as distinct families. In contrast to most traditional classifications, molecular phylogenetic analyses do not suggest a close relationship between Hydnoraceae and Rafflesiaceae. A number of morphological features is shared by Hydnoraceae and Aristolochiaceae; however, a more resolved phylogeny is required to determine whether these represent synapomorphies or independent acquisitions.
The influence of light on paternal plants inCampanula americana(Campanulaceae): pollen characteristics and offspring traits
Authors: Etterson Julie R. , Galloway Laura F.
Published: February 2008

Offspring trait expression is determined by the combination of parental genes and parental environments. Although maternal environmental effects have been widely characterized, few studies have focused on paternal environmental effects. To determine whether light availability influences pollen and offspring traits in the woodland herbCampanula americana, we reared clones of 12 genotypes in two light levels. In the parental generation we measured pollen number and size. Plants grown under high light produced more pollen grains per flower than those grown under low light. However, the response was genotype specific; some individuals responded little to changes in light availability while others substantially reduced pollen production. As a consequence, paternity ratios may vary between light environments if more pollen is associated with greater siring success. We crossed a subset of these plants to produce the offspring generation. The paternal and maternal light environments influenced offspring seed mass, percentage germination, and days to germination, while only maternal light levels influenced later life traits, such as leaf number and size. Maternal and paternal environmental effects had opposite influences on seed mass, percentage germination and days to germination. Finally, there was no direct relationship between light effects on pollen production and offspring trait expression.
Hapsidoxylon terpsichorum gen. et sp. nov., a stem with unusual anatomy from the Triassic of Antarctica
Authors: McManus Hilary A. , Boucher Lisa , Taylor Edith L. , Taylor Thomas N.
Published: February 2008

The Middle Triassic flora of the Fremouw Formation in the central Transantarctic Mountains consists of conifers, cycads, ferns, pteridosperms, and sphenophytes. Stems with an unusual anatomy have been discovered within silicified peat from the same locality. The diameters of the stems range from 1.4 to 1.7 cm; the longest specimen is approximately 12 cm. In transverse section the vascular system consists of segments that occur as single traces or are connected in the center and anastomose at varying levels within the stem. Each segment contains a bifacial vascular cambium. Secondary tissues of each segment surround a central area of parenchyma and small tracheids presumed to represent primary xylem. Surrounding the stem is a periderm. Traces are produced near the periphery of the axis and consist of radially arranged secondary xylem and a thick periderm. The absence of leaves and reproductive organs leads to uncertain phylogenetic relationships. We are unaware of any Triassic plants with this type of vascular tissue organization, and those plants with a similar type of arrangement occur only in the Devonian and Carboniferous. Possible phylogenetic affinities with the Cladoxylales and Lycophyta are examined, but the anatomical differences, along with stratigraphic age, preclude formal assignment to any known taxon at this time. Therefore, we have assigned it to a new taxon: Hapsidoxylon terpsichorum gen. et sp. nov.
Xylem of rattans: vessel dimensions in climbing palms
Authors: Fisher Jack B. , Tan Hugh T. W. , Toh Leslie P. L.
Published: February 2008

We examined 11 species in four genera of rattans (Calamus,Daemonorops,Korthalsia,Plectocomia) growing in their native rainforest habitat in Singapore. Using aqueous safranin dye, we found that >95% of all vascular bundles at the base of a mature stem were functioning to transport water. We determined the frequency of vessel lengths in the long stems of these climbing palms by infiltration with dilute latex paint. Separate length distributions were made for metaxylem and protoxylem vessels; in both, there were many short and a few long vessels. The longest protoxylem vessels ranged from 7.5 to 62 cm in length, but one stem had an exceptional protoxylem vessel measuring 3.0 m. Maximum metaxylem vessel diameters were positively correlated to maximum vessel lengths in these species. The longest metaxylem vessel was found inK. rigidaand was 3.96 m in length and was constructed from ∼1200 vessel elements (cells). The widest vessel in that same stem was 532 μm in diameter. Long, wide vessels decrease resistance and increase water transport efficiency. In addition, we suggest that wide metaxylem vessels may have an important function in water storage.
Impact of tree leaf phenology on growth rates and reproduction in the spring flowering species Trillium erectum (Liliaceae)
Authors: Routhier Marie‐Claude , Lapointe Line
Published: February 2008

We investigated the impact of overstory tree leaf phenology on growth rates, carbon allocation pattern, and fruit characteristics in the spring flowering species, Trillium erectum (Liliaceae). Air temperature, overstory canopy closure, and T. erectum phenology were monitored at three locations following a latitudinal gradient in Québec, Canada. Northern sugar maple trees leaf out at cooler temperatures than more southern populations, while Trillium development was initiated at the same soil temperature irrespective of the latitude. Therefore, in northern areas, the time between initiation of T. erectum leaf expansion and canopy closure was shorter than in southern areas, which left less time for northern plants to accumulate reserves before canopy closure. Differences in growth patterns were noted between T. erectum populations. From a south–north gradient, investment to reproduction, total plant biomass, and annual growth rate decreased, while specific leaf area and stem height increased, indicating shade acclimation. The length of the high light period in early spring seems to be a determinant for spring flowering plants' growth and reproduction and may explain the northern distribution limit of some of these species.
Phylogenetic relationships in the order Ericales s.l.: analyses of molecular data from five genes from the plastid and mitochondrial genomes
Authors: Anderberg Arne A. , Rydin Catarina , Källersjö Mari
Published: February 2008

Phylogenetic interrelationships in the enlarged order Ericales were investigated by jackknife analysis of a combination of DNA sequences from the plastid genesrbcL,ndhF,atpB, and the mitochondrial genesatp1andmatR. Several well‐supported groups were identified, but neither a combination of all gene sequences nor any one alone fully resolved the relationships between all major clades in Ericales. All investigated families except Theaceae were found to be monophyletic. Four families, Marcgraviaceae, Balsaminaceae, Pellicieraceae, and Tetrameristaceae form a monophyletic group that is the sister of the remaining families. On the next higher level, Fouquieriaceae and Polemoniaceae form a clade that is sister to the majority of families that form a group with eight supported clades between which the interrelationships are unresolved: Theaceae‐Ternstroemioideae withFicalhoa,Sladenia, andPentaphylacaceae; Theaceae‐Theoideae; Ebenaceae and Lissocarpaceae; Symplocaceae; Maesaceae, Theophrastaceae, Primulaceae, and Myrsinaceae; Styracaceae and Diapensiaceae; Lecythidaceae and Sapotaceae; Actinidiaceae, Roridulaceae, Sarraceniaceae, Clethraceae, Cyrillaceae, and Ericaceae.
Chimeric patterns in Juniperus chinensis ‘Torulosa Variegata’ (Cupressaceae) expressed during leaf and stem formation
Authors: Korn Robert W.
Published: February 2008

Juvenile leaves of the variegated Hollywood juniper, Juniperus chinensis ‘Torulosa Variegata’, have sectorial chimeras of variable widths and lengths. Sectors extend over several nodes often as small as 1/24 the circumference of the leaf. Other chimeras appear as light green to yellow streaks but are actually internal, dark green corpus sectors often occupying less than 1/20 of the cross sectional area of a leaf. On the basis of the sizes of these two types of sectors, there seems to be ideally about 168 founder cells comprising 63 tunica cells and 105 corpus cells; 49 of the latter are contiguous with the tunica and 66 are located deeper in the corpus. Similarly, sectoring in axillary branches of original chimeric sprays have the same types of sectoring. It is hypothesized that the outer rings of founder cells form two arcs of 12 cells around the stem apex, one for each of two leaves at a node of the decussate shoot, of a circumference of about 50 cells.
Shoot dieback during prolonged drought in Ceanothus (Rhamnaceae) chaparral of California: a possible case of hydraulic failure
Authors: Davis Stephen D. , Ewers Frank W. , Sperry John S. , Portwood Kimberly A. , Crocker Michelle C. , Adams Gerard C.
Published: February 2008

Progressive diebacks of outer canopy branchlets of Ceanothus crassifolius were repeatedly observed after rainless periods up to 9 mo in duration in the Santa Monica Mountains of southern California. Mean xylem pressures of branchlets near the end of drought were as low as −11.2 MPa (N = 22) with a mean of about 60 dead branchlets per shrub. Inoculation (N = 15) with three species of fungi previously isolated from the same population of C. crassifolius did not promote dieback, suggesting that the observed decline was not fungal induced, as had been proposed. Further, at least 50% of healthy‐appearing twigs, without symptoms of dieback, contained isolatible endophytic fungi. We used a centrifugal force method to determine the range of xylem pressure causing cavitation (vulnerability curves) for branchlets (N = 12) and roots (N = 16). We combined vulnerability curves with soil texture data (N = 6) into a water transport model that estimated the critical values (PLcrit) of leaf xylem pressure associated with the loss of water from soil to foliage. Maximum PLcrit was between −10 and −11 MPa and within the range of minimum measured xylem pressures of branchlets during drought and dieback. Branchlet dieback correlated with seasonal declines in xylem pressure in concert with declining safety margins from hydraulic failure. Symptoms of dieback were duplicated in the field by partially severing stem xylem that normally supplied branchlets with water. Taken together, these results indicate that loss of hydraulic conductance to foliage was the probable cause of the observed dieback in C. crassifolius. Partial dieback of peripheral branchlets, and its attendant reduction in evaporative surface area, may be a last‐resort mechanism for whole‐plant water conservation and drought survival in this species.
Morphologically complex plant macrofossils from the Late Silurian of Arctic Canada
Authors: Kotyk Michele E. , Basinger James F. , Gensel Patricia G. , de Freitas Tim A.
Published: February 2008

In addition to vegetative remains, fertile remains from ten plants, representing seven distinct taxa whose size and complexity are much greater than most contemporaneous fossils, are reported from late Ludlow (Ludfordian) sediments of Bathurst Island in Nunavut, Canada. Evidence for the age of these beds is gathered from stratigraphic relationships and index fossils including conodonts, graptolites, and brachiopods. Zosterophylls dominate the collection, some of which constitute the earliest record of fertile structures arranged in dense clusters and longitudinal rows along axes. Representatives include a plant that resembles Bathurstia, one species of Zosterophyllum, and two specimens that bear affinity to this genus. Distichophytum is also represented, as is a new zosterophyll named Macivera gracilis. The prevalence of sporangial clustering and reduced sporangial stalks in this flora leads to a discussion of the origins and significance of these morphological features. Following a review of some of the other Silurian floras, particularly the Baragwanathia‐bearing Lower Plant Assemblage of Victoria, Australia, which also shows morphological advancement over the rhyniophytoid‐dominated floras common to Laurussia, it is concluded that the Bathurst Island flora presents the best evidence to date of substantial morphological diversity, complexity, and stature of vascular land plants in this period.
Comparative floral ontogeny in Detarieae (Leguminosae: Caesalpinioideae). 2. Zygomorphic taxa with petal and stamen suppression
Authors: Tucker Shirley C.
Published: February 2008

Marked floral zygomorphy and a reduced number of petals and/or stamens are the character traits that distinguish the taxa described (species of Afzelia, Berlinia, Gilbertiodendron, Macrolobium, Neochevalierodendron, Paramacrolobium, Phyllocarpus, and Tetraberlinia). All have an “Omega”‐shaped floral apex after bracteole initiation, bracteoles large when initiated, helical sepal initiation, unidirectional petal initiation (simultaneous in Afzelia, not determinable in Tetraberlinia), and unidirectional stamen initiation. Floral zygomorphy is expressed primarily by one petal being much larger than the others and by suppression of several of the stamens. Five petals are initiated in all; suppression begins in late development. Either two petals (Neochevalierodendron, Phyllocarpus) or four petals (Afzelia, Berlinia, Macrolobium, Tetraberlinia) are suppressed. All ten stamens are initiated; at midstage, suppression begins in either three stamens (Afzelia) or seven stamens (Gilbertiodendron, Macrolobium, Paramacrolobium). Other expressions of zygomorphy may include diadelphy, stamen filament connation late in development, or displacement of the carpel from a central position to the adaxial side of the hypanthium. There is no loss of organs similar to that which occurs in some other Detarieae.
The origin of tobacco's T genome is traced to a particular lineage within Nicotiana tomentosiformis (Solanaceae)
Authors: Murad Lena , Lim K. Yoong , Christopodulou Vangellis , Matyasek Roman , Lichtenstein Conrad P. , Kovarik Ales , Leitch Andrew R.
Published: February 2008

Nicotiana tabacum (tobacco) is a natural allotetraploid. The maternal genome donor is not controversial and is probably derived from an ancestor of N. sylvestris. The paternal, T‐genome donor has been less clear, with N. tomentosiformis, N. otophora, or an introgression hybrid proposed. Here we provide evidence that the T genome of N. tabacum is derived from a particular lineage of N. tomentosiformis. We show that the repetitive sequences of geminiviral origin, GRD53 and GRD3, are present in the genomes of N. tabacum cultivars, a tobacco cell suspension culture TBY‐2, and N. tomentosiformis ac. NIC 479/84. Surprisingly, they are not present in another three varieties of N. tomentosiformis. A detailed cytogenetic analysis also revealed that N. tomentosiformis ac. NIC 479/84 most closely resembles the N. tabacum T genome in the location of other tandem repetitive sequences. Thus, tobacco formed after divergence within N. tomentosiformis, and the spectrum of potential donors of the paternal genome can be narrowed to a genotype of N. tomentosiformis characterized by the presence of GRD53 and GRD3 repeats. It is clear that future paternity studies in tobacco should use N. tomentosiformis ac. NIC 479/84 rather than any other accession.
Tackling speciose genera: species composition and phylogenetic position of Senecio sect. Jacobaea (Asteraceae) based onplastid and nrDNA sequences
Authors: Pelser Pieter B. , Gravendeel Barbara , van der Meijden Ruud
Published: February 2008

The molecular phylogeny of Senecio sect. Jacobaea (Asteraceae; Senecioneae) was studied to clarify species composition and interspecific relationships of Senecio sect. Jacobaea. This information is necessary for studies seeking explanations of the evolutionary success of Senecio, in terms of high species numbers and the evolution of chemical defense mechanisms. Parsimony analyses with 60 species of the tribe Senecioneae, representing 23 genera and 11 sections of Senecio, based on DNA sequence data of the plastid genome (the trnT‐L intergenic spacer, the trnL intron, and two parts of the trnK intron, flanking both sides of the matK gene) and nuclear genome (ITS1, 5.8S, and ITS2 gene and spacers) show that sect. Jacobaea is a strongly supported monophyletic group. Fifteen species have been identified as members of section Jacobaea, including three species that have been consistently ascribed to this section in taxonomic literature and 12 species that were either placed in other sections of Senecio or not exclusively ascribed to sect. Jacobaea. This section was traditionally circumscribed as a group of European, biennial, or perennial herbs with pinnately incised leaves, but the results of this study show that one annual species, a species from northeastern Asia, and a species growing in the Himalayas are members of sect. Jacobaea as well. Furthermore, not all species in the section have pinnately incised leaves. The genera Emilia, Packera, and Pseudogynoxys form the sister clade of sect. Jacobaea, but this relationship lacks strong bootstrap support and thus remains provisional.
Phylogenetic origins of Lophocereus (Cactaceae) and the senita cactus–senita moth pollination mutualism
Authors: Hartmann Stefanie , Nason John D. , Bhattacharya Debashish
Published: February 2008

Recent ecological research has revealed that the Sonoran Desert columnar cactus Lophocereus and the pyralid moth Upiga virescens form an obligate pollination mutualism, a rare but important case of coevolution. To investigate the phylogenetic origins of this unusual pollination system, we used molecular sequence data to reconstruct the phylogeny of the four taxa within the genus Lophocereus and to determine the phylogenetic position of Lophocereus within the North American columnar cacti (tribe Pachycereeae). Our analysis included Lophocereus, six Pachycereus species, Carnegiea gigantea, and Neobuxbaumia tetetzo within the subtribe Pachycereinae, and Stenocereus thurberi as an outgroup within the Stenocereinae. Extensive screening of chloroplast and mitochondrial genomes failed to reveal sequence variation within Lophocereus. At a deeper phylogenetic level, however, we found strong support for the placement of Lophocereus within Pachycereus as sister group to the hummingbird‐pollinated P. marginatus. We discuss possible hypotheses that may explain the transition from bat pollination (ancestral) to moth and hummingbird pollination in Lophocereus and P. marginatus, respectively. Additional phylogenetic analyses suggest that the genus Pachycereus should be expanded to include Lophocereus, Carnegiea, Neobuxbaumia, and perhaps other species, whereas P. hollianus may need to be excluded from this clade. Future study will be needed to test taxonomic distinctions within Lophocereus, to test for parallel cladogenesis between phylogroups within Lophocereus and Upiga, and to fully delineate the genus Pachycereus and relationships among genera in the Pachycereinae.
Multilocus genetic structure at contrasted spatial scales of the endangered water fernMarsilea strigosaWilld. (Marsileaceae, Pteridophyta)
Authors: Vitalis Renaud , Riba Miquel , Colas Bruno , Grillas Patrick , Olivieri Isabelle
Published: February 2008

Marsilea strigosa(Marsileaceae, Pterydophyta) is a rare water fern found in the Mediterranean basin, in temporary flooded habitats only. We analyzed the level and the distribution of genetic variation at seven microsatellite loci, both at the Mediterranean scale and at a narrower scale within a highly fragmented French metapopulation. Genetic diversity among individuals within each pond suggests thatM. strigosareproduces predominantly through selfing. The very high population differentiation at the Mediterranean scale indicates that gene flow (if any) is highly restricted. Similar differentiation is also found at the scale of a single metapopulation. The distribution of multilocus genotypes suggests that the genetic variation in this species is maintained mainly through the interplay of mutation and low recombination.
Floral biology and unique pollination system of root holoparasites, Balanophora kuroiwai and B. tobiracola (Balanophoraceae)
Authors: Kawakita Atsushi , Kato Makoto
Published: February 2008

We investigated the floral and pollination biology of two monoecious root holoparasites, Balanophora kuroiwai and B. tobiracola (Balanophoraceae), in the subtropical forests of southern Japan. Both species secrete nectar from extrafloral nectaries distributed among the flowers, which is mainly consumed by ants, cockroaches, and pyralid moths. Pollen grains were found attached to the bodies of these insects. Pyralid moths of the genera Assara and Nacoleia were observed laying eggs on the inflorescences of B. kuroiwai. In both Balanophora species, pyralid larvae were found feeding on vegetative tissue without exploiting the seeds, and adults emerged from the fruited infructescences. In B. kuroiwai, we assessed pollination success under different experimental conditions by estimating the percentage of styles that had pollen tubes reaching the ovules. This revealed that: (1) the plants were at least sporophytically self‐compatible; (2) they were generally pollinated within an inflorescence (geitonogamy); (3) outcrossing occurred, but the rates varied greatly among inflorescences; and (4) ants were probably responsible for the geitonogamy. While ants and flightless cockroaches were the most likely contributors to geitonogamous self‐pollination, we consider pyralid moths to be the most likely cross‐pollinators of Balanophora species. This is a new example of pollination mutualism involving a plant and its pollinating parasite.
Floral variation in the generalist perennial herb Paeonia broteroi (Paeoniaceae): differences between regions with different pollinators and herbivores
Authors: Sánchez‐Lafuente Alfonso M.
Published: February 2008

This paper investigates the differences in floral phenotype in Paeonia broteroi (Paeoniaceae) in four populations at two distant mountainous regions in southern Spain. Paeonia broteroi flowers exhibit traits of a highly generalized pollination system, but previous studies have revealed that not all flower visitors are effective at pollen delivery. Plants differed between regions in the number of flowers per plant, petal size, number of stamens per flower, and ovules per carpel. Differences between regions could not be attributable to differences in the size structure of the plants. Flower visitors in the two regions differed in assemblage and body size at all the spatiotemporal scales. Larger visitors were more effective as pollinators in the region with the largest and more rewarding (as measured by the number of stamens) flowers, suggesting that pollinators may create opportunities for selection of certain floral traits. In contrast, the two regions did not differ in the probability of damage by herbivores, which did not select flowers based on any of the measured traits, nor affected maternal fecundity. Despite the differences in flower phenotype, potential maternal fecundity, and pollinator effectiveness, plants did not differ between regions in seed production. The role of pollinators as determinants of the differences between regions in floral phenotype, through male and female reproductive success, is discussed. Also, alternative explanations to divergence are addressed, with special reference to the patterns of resource allocation between sexual functions and genetic drift.
Do floral herbivores respond to variation in flower characteristics in Gelsemium sempervirens (Loganiaceae), a distylous vine?
Authors: Leege Lissa M. , Wolfe Lorne M.
Published: February 2008

We tested the hypothesis that traits traditionally thought to function in pollination can also influence attack by floral herbivores. Because distylous species produce two different flower types, we used Gelsemium sempervirens, a distylous vine of southeastern USA, to examine the frequency and pattern of floral herbivory in relation to floral characteristics. Flowers of the short‐styled morph had larger corollas but showed no difference in the volume or concentration of nectar produced. Over the 2 yr of this study, 20–30% of plants suffered floral herbivory. The pattern of damage was morph‐specific. Long‐styled flowers were more likely to have damaged pistils, while stamens were more often damaged in short‐styled flowers. In this distylous species, exserted flower organs were more likely to be eaten. Such differential herbivory based on the position of floral organs within a flower may result in reduced fitness via either male (short‐styled morph) or female function (long‐styled morph).
A phylogenetic evaluation of a biosystematic framework: Brodiaea and related petaloid monocots (Themidaceae)
Authors: Pires J. Chris , Sytsma Kenneth J.
Published: February 2008

Phylogenetic analyses of plastid DNA sequences of ndhF, trnL‐F intron and spacer regions, and rpl16 are presented separately and combined for 41 taxa from all 12 genera of the Themidaceae and for 20 taxa from nine related families in the higher Asparagales. The results from the combined analysis are the most resolved and provide a high level of support for the monophyly of Themidaceae. Within Themidaceae, the Milla complex of Mexico is supported as monophyletic within a paraphyletic Brodiaea complex of western North America. Four major clades are identified in each of the individual and combined analyses: (1) the Milla complex; (2) Brodiaea, Dichelostemma, and Triteleiopsis; (3) Triteleia, Bloomeria, and Muilla clevelandii; and (4) Androstephium and the other species of Muilla. These well‐defined clades suggest that morphological characters (e.g., an extended perianth tube) that have been traditionally used to circumscribe the genera within the Brodiaea complex have evolved independently at least twice. In addition, common biogeographic distribution patterns (e.g., Brodiaea and Triteleia having centers of diversity in northern California and the Pacific Northwest) appear to be the result of separate evolutionary radiations.
Photosynthetic characteristics of invasive and noninvasive species of Rubus (Rosaceae)
Authors: McDowell Susan C. L.
Published: February 2008

The prolific amount of growth and reproduction in invasive plants may be achieved by greater net photosynthesis and/or resource‐use efficiency. I tested the hypotheses that leaf‐level photosynthetic capacity and resource‐use efficiency were greater in two invasive species of Rubus as compared with two noninvasive species that have overlapping distributions in the Pacific Northwest. The invasive species had significantly higher photosynthetic capacity and maintained net photosynthesis (A) over a longer period of the year than the noninvasive species. The construction cost (CC) of leaf tissue per unit leaf mass was comparable among the four species, but the invasive species allocated less nitrogen (N) per unit leaf mass. On a leaf area basis, both leaf CC and N were higher for the invasive species. The specific leaf area (SLA) was also lower in the invasive species, indicating less photosynthetic area per gram leaf tissue. The invasive species achieved high A at lower resource investments than the noninvasive species, including having higher maximum photosynthetic rate (Amax) per unit dark respiration (Rd), greater Amax per unit leaf N (photosynthetic nitrogen‐use efficiency), and greater water‐use efficiency as measured by instantaneous rates of A per unit transpiration (A/E) and by integrated A/E inferred from stable carbon isotope ratios (δ13C). Using discriminant analysis, these photosynthetic characteristics were found to be powerful in distinguishing between the invasive and noninvasive Rubus. Amax and A/E were identified as the most useful variables for distinguishing between the species, and therefore, may be important factors contributing to the success of these invasive species.
Intragenomic and interspecific 5S rDNA sequence variation in five Asian pines
Authors: Liu Zhan‐Lin , Zhang Daming , Wang Xiao‐Quan , Ma Xiao‐Fei , Wang Xiao‐Ru
Published: February 2008

Patterns of intragenomic and interspecific variation of 5S rDNA in Pinus (Pinaceae) were studied by cloning and sequencing multiple 5S rDNA repeats from individual trees. Five pines, from both subgenera, Pinus and Strobus, were selected. The 5S rDNA repeat in pines has a conserved 120‐base pair (bp) transcribed region and an intergenic spacer region of variable length (382–608 bp). The evolutionary rate in the spacer region is three‐ to sevenfold higher than in the genic region. We found substantial sequence divergence between the two subgenera. Intragenomic sequence heterogeneity was high for all species, and more than 86% of the clones within each individual were unique. The 5S gene tree revealed that different 5S repeats within individuals are polyphyletic, indicating that their ancestral divergence preceded the speciation events. The degrees of interspecific and intragenomic divergence among diploxylon pines are similar. The observed sequence patterns suggest that concerted evolution has been acting after the diversification of the two subgenera but very weak after the speciation of the four diploxylon pines. Sequence patterns in P. densata are consistent with hybrid origin. It had higher intragenomic diversity and maintained polymorphic copies of the parental types in addition to new and recombinant types unique to the hybrid.
Leaf biomechanics, morphology, and anatomy of the deciduous mesophyte Prunus serrulata (Rosaceae) and the evergreen sclerophyllous shrub Heteromeles arbutifolia (Rosaceae)
Authors: Balsamo Ronald A. , Bauer Aaron M. , Davis Stephen D. , Rice Benita M.
Published: February 2008

Leaf tensile properties were compared between the mesic deciduous tree Prunus serrulata (var. “Kwanzan”) and the xeric and sclerophyllous chaparral evergreen shrub Heteromeles arbutifolia (M. Roem). All values for biomechanical parameters for H. arbutifolia were significantly greater than those of P. serrulata. The fracture planes also differed between the two species with P. serrulata fracturing along the secondary veins, while H. arbutifolia most often fractured across the leaf irrespective of the vein or mesophyll position, thus yielding qualitative differences in the stress‐strain curves of the two species. Anatomically, P. serrulata exhibits features typical for a deciduous mesophytic leaf such as a thin cuticle, a single layer of palisade mesophyll, isodiametric spongy mesophyll, and extensive reticulation of the laminar veins. Heteromeles arbutifolia leaves, however, are typically two‐ to three‐fold thicker with a 35% higher dry mass/fresh mass ratio. The vascular tissue is restricted to the interface of the palisade and spongy mesophyll near the center of the leaf. Both epidermal layers have a thick cuticle. The palisade mesophyll is tightly packed and two to three layers thick. The spongy mesophyll cells are ameboid in shape and tightly interlinked both to other spongy cells as well as to the overlying palisade layer. We conclude that the qualitative and quantitative biomechanical differences between the leaves of these two species are likely due to a complex interaction of internal architectural arrangement and the physical/chemical differences in the properties of their respective cell walls. These studies illustrate the importance that morphological and anatomical correlates play with mechanical behavior in plant material and ultimately reflect adaptations present in the leaves of chaparral shrubs that are conducive to surviving in arid environments.
Integrating gene flow, crop biology, and farm management in on‐farm conservation of avocado (Persea americana, Lauraceae)
Authors: Birnbaum Kenneth , DeSalle Rob , Peters Charles M. , Benfey Philip N.
Published: February 2008

Maintaining crop diversity on farms where cultivars can evolve is a conservation goal, but few tools are available to assess the long‐term maintenance of genetic diversity on farms. One important issue for on‐farm conservation is gene flow from crops with a narrow genetic base into related populations that are genetically diverse. In a case study of avocado (Persea americana var. americana) in one of its centers of diversity (San Jerónimo, Costa Rica), we used 10 DNA microsatellite markers in a parentage analysis to estimate gene flow from commercialized varieties into a traditional crop population. Five commercialized genotypes comprised nearly 40% of orchard trees, but they contributed only about 14.5% of the gametes to the youngest cohort of trees. Although commercialized varieties and the diverse population were often planted on the same farm, planting patterns appeared to keep the two types of trees separated on small scales, possibly explaining the limited gene flow. In a simulation that combined gene flow estimates, crop biology, and graft tree management, loss of allelic diversity was less than 10% over 150 yr, and selection was effective in retaining desirable alleles in the diverse subpopulation. Simulations also showed that, in addition to gene flow, managing the genetic makeup and life history traits of the invasive commercialized varieties could have a significant impact on genetic diversity in the target population. The results support the feasibility of on‐farm crop conservation, but simulations also showed that higher levels of gene flow could lead to severe losses of genetic diversity even if farmers continue to plant diverse varieties.