bluuebunny/crossref_metadata_2025 huggingface dataset:
Phenology and fecundity in 11 sympatric pioneer species ofMacaranga(Euphorbiaceae)in Borneo
Authors: Davies Stuart J. , Ashton Peter S.
Published: April 2006

Reproductive traits of tropical tree species vary predictably in relation to successional stage, but this variation may be due to the species’ phylogenetic histories rather than selective pressures imposed by regeneration requirements. Reproductive phenology, tree size at the onset of reproduction, and fecundity of 11 sympatric, closely relatedMacarangaspecies were studied to investigate within‐species variation in reproductive traits in relation to resource availability, and among‐species variation in relation to other life‐history traits (shade tolerance, seed size and maximum tree size,Hmax) and consequently the requirements for forest‐gap colonization. Nine species reproduced in synchronous episodes, and two species reproduced continuously over 32 mo. Episodic reproduction was most intense in 1992 following a severe drought. For several species, reproductive trees had greater light availability, lower fecundity in lower light levels, and lower growth rates than nonreproductive trees, reflecting resource‐limited reproduction. Among species,Hmaxwas negatively correlated with shade tolerance and seed size. Tree size at the onset of reproduction and fecundity was strongly linked to this axis of life‐history variation, but phenological pattern was not. Absolute tree size at the onset of reproduction was positively correlated withHmaxand negatively correlated with shade tolerance. Relative size at reproductive onset was not correlated with shade tolerance orHmax. Fecundity ranged four orders of magnitude among species and was correlated positively withHmaxand negatively with seed size and shade tolerance. The interrelationships among these reproductive and other life‐history traits are strongly correlated with the species’ requirements for gap colonization.
Wood anatomy of Elaeagnaceae, with comments on vestured pits, helical thickenings, and systematic relationships
Authors: Jansen Steven , Piesschaert Frederic , Smets Erik
Published: April 2006

The secondary xylem ofElaeagnus, Hippophae,andShepherdiais described and illustrated in detail. Shrubs and small trees of Elaeagnaceae have ring‐porous or semi‐ring‐porous wood with simple perforation plates, vascular tracheids, fiber‐tracheids, diffuse or rarely paratracheal axial parenchyma, and uni‐ or biseriate rays inHippophaeandShepherdia,but wider rays inElaeagnus.Walls of vessel elements, especially narrow ones, tracheids, or fiber‐tracheids sometimes show helical thickenings; in a few instances these intergrade with small bud‐like protrusions associated with pits. Scanning electron microscopy illustrates that small to vestigial vestures are present in all species studied, although nonvestured pits are also common. The analogous nature of vestures and helical thickenings is considered. Comparative wood anatomy suggests a rather isolated position of the family Elaeagnaceae; affinities with Rhamnaceae, Proteaceae, and Thymelaeaceae are discussed.
Reorientation of daffodil(Narcissus: Amaryllidaceae) flowers inwind: drag reduction andtorsional flexibility
Authors: Etnier Shelley A. , Vogel Steven
Published: April 2006

Daffodil flowers extend laterally from the long axes of their stems; as a result, wind on a flower exerts torsional as well as flexural stress on the stem. Stems respond by twisting, and thus flowers reorient to face downwind in moderate winds, in the process reducing their drag by ∼30%. This repositioning is facilitated by the stems’ relatively low torsional stiffness. Daffodil stems have a ratio of flexural to torsional stiffness of 13.27 ± 0.96 (SD), compared with 8.33 ± 3.20 (SD) for tulip stems, which bear flowers as symmetrical extensions of their long axes, and compared with 1.5 for isotropic, incompressible, circular cylinders.
Effects of local density on pollination and reproduction in Delphinium nuttallianum and Aconitum columbianum (Ranunculaceae)
Authors: Bosch Maria , Waser Nickolas M.
Published: April 2006

Plant populations vary in density both naturally and as a consequence of anthropogenic impacts. Density in turn can influence pollination by animals. For example, plants in dense populations might enjoy more frequent visitation if pollinators forage most efficiently in such populations. We explored effects of plant density on pollination and seed set in the larkspur Delphinium nuttallianum and monkshood Aconitum columbianum. At our site in the Colorado Rocky Mountains, flowers of D. nuttallianum are pollinated primarily by queen bumble bees, solitary bees, and hummingbirds, whereas those of A. columbianum are pollinated primarily by queen and worker bumble bees. We found that the quantity of pollination service to both species (pollinator visitation rate and pollen deposition) was at best weakly related to density. In contrast, seed set declined by approximately one‐third in sparse populations relative to nearby dense populations. This decline may stem from the receipt of low‐quality pollen, for example, inbred pollen. Alternatively, sparsity may indicate poor environmental conditions that lower seed set for reasons unrelated to pollination. Our results demonstrate the value of simultaneously exploring pollinator behavior, pollen receipt, and seed set in attempting to understand how the population context influences plant reproductive success.
Experimental analysis of protogyny in Aquilegia canadensis (Ranunculaceae)
Authors: Griffin Steven R. , Mavraganis Katherine , Eckert Christopher G.
Published: April 2006

Dichogamy is very common in flowering plants and is widely thought to reduce pollen‐pistil interference, especially self‐pollination. Yet, the functional significance of dichogamy has rarely been studied. We investigated the nature and functioning of dichogamy in eastern Ontario populations of Aquilegia canadensis, a highly selfing columbine previously described as protogynous. We then manipulated flowers to determine whether increased protogyny would reduce self‐fertilization. Contrary to previous reports, A. canadensis is not dichogamous. Controlled pollinations in a greenhouse showed that pollen tubes generally begin to develop after anther dehiscence. Although stigmas can collect pollen early in floral development, naturally pollinated flowers collected from four populations had few pollen grains on stigmas and almost no pollen tubes in styles until after anther dehiscence. Limited pollen deposition before anther dehiscence was also associated with low nectar availability and limited sepal expansion. Because inbreeding depression is strong in this species, selection may favor increased protogyny if it reduces selfing. We tested this hypothesis by comparing the level of selfing in flowers rendered protogynous by the removal of the first 19 (of 39) anthers to develop, with nonprotogynous control flowers. Contrary to expectations, protogyny did not reduce selfing. Our results emphasize the importance of detailed field observations and manipulative experiments in understanding the nature and functional significance of dichogamy.
The effects of gap size and disturbance type on invasion of wet pine savanna by cogongrass, Imperata cylindrica (Poaceae)
Authors: King Sharon E. , Grace James B.
Published: April 2006

Cogongrass is a nonindigenous species perceived to threaten native communities of the southeastern United States through modification of species composition and alteration of community processes. To examine how gap size and disturbance type influence the invasion of wet pine savannas by cogongrass, we performed three field experiments to evaluate the response of cogongrass seeds and transplanted seedlings to four different gap sizes, four types of site disturbance, and recent burning of savanna vegetation. Cogongrass germinated, survived, and grew in all gap sizes, from 0 to 100 cm in diameter. Similarly, disturbance type had no effect on germination or seedling and transplant survival. Tilling, however, significantly enhanced transplanted seedling growth, resulting in a tenfold increase in biomass over the other disturbance types. Seedling survival to 1 and 2 mo was greater in burned savanna than unburned savanna, although transplant survival and growth were not affected by burning. Results of this study suggest that cogongrass can germinate, survive, and grow in wet pine savanna communities regardless of gap size or type of disturbance, including burning. Burning of savanna vegetation may enhance establishment by improving early seedling survival, and soil disturbance can facilitate invasion of cogongrass by enhancing plant growth.
Polemoniaceae phylogeny and classification: implications of sequence data from the chloroplast gene ndhF
Authors: Prather L. Alan , Ferguson Carolyn J. , Jansen Robert K.
Published: April 2006

The chloroplast gene ndhF was used to study phylogenetic relationships of the Polemoniaceae at two levels: among members of the Ericales and among genera of the family. Sequence data for interfamilial analyses consisted of 2266 bp for 14 members of the Ericales, including four species of the Polemoniaceae, plus three outgroup taxa. The Polemoniaceae were found to be related to Diospyros, Fouquieria, the Primulales, Rhododendron, and Impatiens, but relationships among taxa were generally not well supported. The precise position of the Polemoniaceae within the Ericales remains obscure. Data for intrafamilial analyses consisted of 1031 bp for 27 species of the Polemoniaceae, including at least one species from most genera of the family, plus five outgroup taxa. A single most parsimonious tree was identified. The analyses suggested that subfamily Cobaeoideae, excluding Loeselia, is monophyletic and that Huthia is sister to Cantua. Acanthogilia was sister to the remainder of subfamily Cobaeoideae. Subfamily Polemonioideae plus Loeselia formed four subclades that were strongly supported as monophyletic and represent the major lineages of the subfamily.
The cost of realized sexual reproduction: assessing patterns of reproductive allocation and sporophyte abortion in a desert moss
Authors: Stark Lloyd R. , Mishler Brent D. , McLetchie D. Nicholas
Published: April 2006

The desert moss Syntrichia caninervis exhibits one of the most skewed sex ratios in the plant kingdom, with female individuals far outnumbering male individuals (exceeding 14♀:1♂). The “cost of sex hypothesis” derives from allocational theory and predicts that the sex which is most expensive should be the rarer sex. This hypothesis, which, as considered here represents the realized cost of sexual reproduction, is contingent upon two assumptions that are explored: (1) that male sex expression is more expensive than female sex expression, and (2) that sexual reproduction is resource limited. Using inflorescence biomass and discounting sperm, male sex expression was found to be in the neighborhood of one order of magnitude more expensive than female sex expression, and this difference is reflected in higher numbers of gametangia per male inflorescence, presence of paraphyses in male inflorescences, and a much longer developmental time for male inflorescences. The realized cost of female reproduction from two communities dominated by S. caninervis was found to be lower than the realized cost of male sexual reproduction. Resource‐limited reproduction was assessed by determining the frequency of sporophyte abortion, the age distribution of sporophyte abortions, and patterns of sporophyte abortion that may be density dependent. Among ten sexually reproducing populations, abortive sporophytes occurred at a frequency of 0.64. Abortive sporophytes averaged 8% the mass of mature sporophytes, and cohort sporophytes from the same individual female were found to abort in a density‐dependent pattern. We conclude that the two assumptions, upon which the cost of sex hypothesis depends, are supported.
Sex expression, sex‐specific traits, and the effects of salinity on growth and reproduction of Amaranthus cannabinus (Amaranthaceae), a dioecious annual
Authors: Bram Margot R. , Quinn James A.
Published: April 2006

Amaranthus cannabinus was studied to investigate some of the ecological factors thought to be involved in the evolution of dioecy and to investigate the effects of salinity on sex expression and sex‐specific selection. In the field portion of this study, sex ratios, stability of sex expression, spatial distribution, allocation strategies, and phenologies of the sexes were investigated in New Jersey freshwater and salt marsh populations of water hemp. To examine the effects of salinity on vegetative and reproductive development of males and females, plants were grown in the greenhouse at three salinity levels. Adult sex ratios were found to be 1:1. Temporal deviations from a 1:1 sex ratio varied by population and were due to differences in flowering phenology and mortality between the sexes. No plants were observed to change sex expression, and there was no evidence of spatial segregation of the sexes in the field. In both the field and the greenhouse, females allocated more resources to vegetative tissues and had a longer growing period than males. The results of this study suggest that increased reproductive efficiency through sex‐specific growth patterns may have been an important selective factor involved in the evolution of dioecy in A. cannabinus.
Anatomical and developmental study of petrified Quercus (Fagaceae) fruits from the Middle Miocene, Yakima Canyon, Washington, USA
Authors: Borgardt Sandra J. , Pigg Kathleen B.
Published: April 2006

The first reported petrified acorns to show internal anatomical structure are here described from Middle Miocene (∼15.6 million years old) chert of the Columbia River Basalt Group in Yakima Canyon, Washington. Quercus hiholensis Borgardt et Pigg sp. nov. is described from anatomical and morphological fruit features, as well as a little recognized anatomical feature, the umbilical complex. Acorns, each comprising a nut and its cupule, are up to 15.3 mm long and 18.8 mm wide with helically arranged, imbricate, tuberculate cupule scales. They show basal aborted ovules, short styles, broad stigmas, and lack grooves in their cotyledons. These characters and the developmental pattern seen in these fossil acorns demonstrate that Q. hiholensis conforms to genus Quercus (Fagaceae), subgenus Quercus, section Quercus (the white oaks). The correspondence of Q. hiholensis to the modern section Quercus reveals that the derived floral and fruit characters that distinguish section Quercus within the genus had evolved by the Middle Miocene.
Chromosomes of Villadia and Altamiranoa (Crassulaceae)
Authors: Uhl Charles H. , Moran Reid
Published: April 2006

Villadia, ranging from Texas to Peru with some 25 species, has a rather distinctive thyrsoid to spicate inflorescence, and we keep it as a genus separate from Sedum. Twenty species show every gametic chromosome number from 9 to 17 and also 20–22 and higher. Chromosome pairing in hybrids shows that the species differ by many translocations and that species with 21 or lower are effectively diploid. More specialized species tend to have fewer and larger chromosomes, suggesting that through time translocations have rearranged the ancestral genome into fewer units. We suspect that relocated genes may be programmed differently, affecting phenotype. Thus Villadia is like Echeveria in having a remarkably long descending series of evidently diploid chromosome numbers. Altamiranoa, often included in Villadia, with about 15 species from Mexico south, more closely resembles Sedum in its broadly cymose inflorescence. It appears polyphyletic, with no clear boundary from Sedum, and we disperse its species in Sedum. The ten species studied have gametic numbers from 20 to 29 that probably are effectively diploid, with a few higher and probably polyploid. Again, chromosome pairing in hybrids shows that the species differ by many translocations. Putative relatives in Sedum section Leptosedum have n = 26 to 31. Thus cytologically as well as morphologically Altamiranoa has remained more similar than Villadia to its Sedum relatives.
Phylogenetic relationships in Nuphar (Nymphaeaceae): evidence from morphology, chloroplast DNA, and nuclear ribosomal DNA
Authors: Padgett Donald J. , Les Donald H. , Crow Garrett E.
Published: April 2006

The genus Nuphar consists of yellow‐flowered waterlilies and is widely distributed in north‐temperate bodies of water. Despite regular taxonomic evaluation of these plants, no explicit phylogenetic hypotheses have been proposed for the genus. We investigated phylogenetic relationships in Nuphar using morphology and sequences of the chloroplast gene matK and of the internal transcribed spacer (ITS) regions of nuclear ribosomal DNA. Two major lineages within Nuphar are consistently resolved with the morphological and molecular data sets. One lineage comprises New World taxa and the other represents a primarily Old World lineage. Relationships within the major lineages were poorly resolved by morphology and ITS, yet certain relationships were elucidated by all analyses. Most notable is the strong support for a monophyletic lineage of dwarf taxa and the alliance of the North American N. microphylla with the Eurasian taxa. Minor discordance between the independent cladograms is accounted for by hybridization. The common taxonomic practice of uniting all North American and Eurasian taxa under one species is not supported phylogenetically.
Systematics of Amaryllidaceae based on cladistic analysis of plastid sequence data
Authors: Meerow Alan W. , Fay Michael F. , Guy Charles L , Li Qin‐Bao , Zaman Faridah Q , Chase Mark W.
Published: April 2006

Cladistic analyses of plastid DNA sequencesrbcLandtrnL‐Fare presented separately and combined for 48 genera of Amaryllidaceae and 29 genera of related asparagalean families. The combined analysis is the most highly resolved of the three and provides good support for the monophyly of Amaryllidaceae and indicates Agapanthaceae as its sister family. Alliaceae are in turn sister to the Amaryllidaceae/Agapanthaceae clade. The origins of the family appear to be western Gondwanaland (Africa), and infrafamilial relationships are resolved along biogeographic lines. Tribe Amaryllideae, primarily South African, is sister to the rest of Amaryllidaceae; this tribe is supported by numerous morphological synapomorphies as well. The remaining two African tribes of the family, Haemantheae and Cyrtantheae, are well supported, but their position relative to the Australasian Calostemmateae and a large clade comprising the Eurasian and American genera, is not yet clear. The Eurasian and American elements of the family are each monophyletic sister clades. Internal resolution of the Eurasian clade only partially supports currently accepted tribal concepts, and few conclusions can be drawn on the relationships of the genera based on these data. A monophyletic Lycorideae (Central and East Asian) is weakly supported.GalanthusandLeucojum(Galantheae pro parte) are supported as sister genera by the bootstrap. The American clade shows a higher degree of internal resolution. Hippeastreae (minusGriffiniaandWorsleya) are well supported, and Zephyranthinae are resolved as a distinct subtribe. An Andean clade marked by a chromosome number of 2n= 46 (and derivatives thereof) is resolved with weak support. The plastid DNA phylogenies are discussed in the context of biogeography and character evolution in the family.
Classification, origins, and patterns of diversification in New ZealandCarmichaelinae (Fabaceae)
Authors: Wagstaff Steven J. , Heenan Peter B. , Sanderson Michael J.
Published: April 2006

Analysis of ITS sequences provides support for a clade that includes Carmichaelia, Clianthus, Montigena, and Swainsona. We provide a node‐based definition and recommend that this clade be called Carmichaelinae. Results suggest that Carmichaelinae are derived from northern hemisphere Astragalinae. The clade has extensively radiated in Australia, and two independent lineages have diversified in New Zealand. The New Zealand lineages differ in species richness. One lineage consists of 24 species placed in Carmichaelia and Clianthus, while the other corresponds to the monotypic genus Montigena. The pattern of relationships inferred from ITS sequences suggests that the New Zealand radiation was recent and possibly accompanied episodes of mountain‐building and glaciation.
A developmental and evolutionary analysis of embryology in Platanus (platanaceae), abasal eudicot
Authors: Floyd Sandra K. , Lerner Veronica T. , Friedman William E.
Published: April 2006

The Platanaceae are an early derived eudicot lineage and therefore occupy a key position for understanding reproductive character diversification associated with the early evolutionary radiation of flowering plants. We conducted an embryological study of Platanus racemosa in order to provide critical data on defining angiosperm reproductive characters for this important group. Female gametophyte development is monosporic. Embryogenesis occurs in a series of stages including zygote elongation and division, development of a linear proembryo, formation of the embryo proper, histogenesis, organogenesis, and growth. Endosperm development is a complex process that includes four distinct phases: free nuclear proliferation, cellularization of the chalazal zone, centripetal cellularization of the micropylar zone, and cellular differentiation and growth. Only the outer endosperm layer persists at seed maturity. Our findings differ significantly from previously published reports for Platanus, in which endosperm development was described as ab initio cellular. A comparison of endosperm development in Platanus with several closely and distantly related free nuclear taxa reveals considerable developmental variability, consistent with a hypothesis of multiple origins of free nuclear endosperm in angiosperms. Our analysis indicates that much remains to be learned about embryology in basal angiosperms. Additional developmental and comparative studies will likely reveal critical insights into the early evolution of flowering plants.
The edaphic factor and patterns of variation in Lasthenia californica (Asteraceae)
Authors: Rajakaruna Nishanta , Bohm Bruce A.
Published: April 2006

Transectional studies of Lasthenia californica in the Jasper Ridge Biological Preserve (Stanford University) have documented the existence of two races (A and C) based upon flavonoid chemistry, achene morphology, allozymes, and flowering time differences. The two races coexist on a serpentine outcrop and have maintained a sharply defined pattern of distribution for a period of at least 15 yr. The present study has revealed significant differences in the physical and chemical features of the soils harboring the two races. Soils at the lower ends of the transects, where race A plants grow, have higher pH, cation exchange capacity, relative water content, total ionic strength, percentage clay, and sodium and magnesium concentrations than do soils harboring race C plants at the upper ends of the transects. Soils supporting race C plants have higher calcium, potassium, and nickel concentrations and higher calcium:magnesium ratios. Plant tissue concentrations of ions were also significantly different in the two races. Race A plants accumulated sodium to concentrations three times those observed with race C plants. Plants from an additional 22 sites gave very similar results. Greenhouse studies indicated that the two races from Jasper Ridge show differential responses to ridge‐top and ridge‐bottom soils. Race A achenes germinated, grew to maturity, and set seed about equally in the two soils. Race C achenes germinated in both types of soils but showed significantly poorer growth and absolutely no flowering when found in the soils of race A plants. Differential responses to edaphic conditions on the ridge may contribute to the pattern of distribution observed over the years. It is suggested that race A plants are more tolerant of edaphic stress than race C plants and that physiological specialization may contribute to the present distribution of the two races throughout the species’ range. It is not yet possible to state which is the more significant factor in driving this specialization, the chemistry of the soil or its physical characteristics, or whether there is interaction between the two. This is the first study to present evidence for soil/plant variation within a serpentine site. The linking of sodium levels to racial differentiation within the serpentine habitat is also a new discovery.
Molecular phylogenetics of Fouquieriaceae: evidence from nuclear rDNA ITS studies
Authors: Schultheis Lisa M. , Baldwin Bruce G.
Published: April 2006

Molecular sequence data from the 18S–26S rDNA internal transcribed spacer (ITS) region support the monophyly of Fouquieria sensu lato (Fouquieriaceae) and the three subgenera (subg. Fouquieria, subg. Bronnia, subg. Idria) previously recognized within it. Resolution within subg. Fouquieria differs somewhat between parsimony and maximum likelihood (ML) trees. Section Fouquieria and sect. Ocotilla within subg. Fouquieria are not well supported as monophyletic groups. Uncertainty regarding placement of the root within Fouquieriaceae makes discussion of character evolution within the family difficult. Three root positions are consistent with rate‐constant evolution of ITS sequences: (1) along the branch to subg. Idria, (2) along the branch to subg. Bronnia, and (3) along the branch to subg. Fouquieria. The first root position listed is equivalent to an outgroup rooting. The third root position listed is equivalent to a midpoint rooting. Of the three root positions above, only the third is along a branch that may be sufficiently long to act as a long‐branch attractor. The first two root positions would result in character reconstruction suggesting that succulent growth forms and white floral pigmentation are ancestral within the family, with shifts to woody growth forms and to red floral pigmentation. The third root position results in equivocal reconstruction of the ancestral growth form, equivocal reconstruction of ancestral floral pigmentation in parsimony trees, and a suggestion of white floral pigmentation as ancestral in ML trees. Two previous hypotheses of polyploid origins are compatible with the molecular data presented here: (1) origin of the tetraploid F. diguetii from F. macdougalii, and (2) allopolyploid origin of the hexaploid F. burragei from the tetraploid F. diguetii and a diploid species similar to F. splendens. Direct descent of the hexaploid F. columnaris from the subg. Bronnia lineage is not supported by our data. An amphiploid origin of F. columnaris involving a member of the subg. Bronnia lineage and an extinct taxon outside subg. Bronnia, however, cannot be ruled out.
Phylogenetic relationships in Lupinus (Fabaceae: Papilionoideae) based on internal transcribed spacer sequences (ITS) of nuclear ribosomal DNA
Authors: Ainouche Abdel‐Kader , Bayer Randall J.
Published: April 2006

Internal transcribed spacer (ITS) sequences of nuclear ribosomal DNA from 44 taxa of the genus Lupinus and five outgroup taxa were used for phylogenetic analysis. Lupinus appears as a strongly supported monophyletic genus, which is unambiguously part of the Genisteae. The lupines are distributed into five main clades in general accordance with their geographical origin. In the Old World, almost all the recognized taxonomic units are well resolved. The ITS data reveal an unexpectedly close relationship between the diverse sections Angustifoli and Lutei. The ITS results suggest a geographical division between the western New World lupines and the eastern ones. They also indicate the presence of some moderately to strongly supported groups of taxa, such as the Microcarpi–Pusilli group, the L. spariflorus–L. arizonicus group, the L. mexicanus–L. elegans group in the western New World, and the notable L. multiflorus–L. paraguariensis group in the eastern New World. The latter group strongly suggests that the eastern South American compound‐ and simple‐leaved perennial lupines derive from a common ancestor. However, apart from some exceptions, relationships within the genus still remain largely unresolved based on ITS data. The lack of resolution at the base of the genus is suggestive of a rapid initial radiation of the lupines subsequent to the dispersal of their common ancestor. Relative rate tests demonstrate the presence of rate heterogeneity of ITS sequences within Lupinus. In many pairwise comparisons between taxa, substitution rate inequalities are correlated with the habit (annual, perennial), suggesting some role for the generation time effects in the evolutionary history of lupines.
Unfertilized ovules of Epilobium obcordatum (Onagraceae) continue to grow in developing fruits
Authors: Seavey Steven R. , Mangels Susan K. , Chappel Natasha J.
Published: April 2006

To determine whether unfertilized ovules continue to grow when in an ovary containing fertilized ovules, we measured ovule lengths in developing fruits of Epilobium obcordatum that were harvested 4, 5, 8, and 10 d post pollination. We found that unfertilized ovules that were in the presence of fertilized ovules continued to grow and that there was a broad range of overlap in their sizes at all sampling times. This effect was found for two types of unfertilized ovules that occur throughout the length of the ovary: normal, unfertilized ovules, apparently bypassed by pollen tubes; and sterile ovules lacking an embryo sac. In addition, there is a position effect within developing fruits. Both fertilized and unfertilized ovules are larger at the stylar end. In six samples resulting from pollination with a single pollen tetrad, a total of 18 embryos were found, and the effect on unfertilized ovules, greatest at the stylar end, diminished with distance from the ovules with embryos. Our results are consistent with the interpretation that diffusible hormones produced by developing seeds cause nearby unfertilized ovules to grow. We conclude that caution is necessary when attempting to infer ovule fertilization histories from the appearances of ovules in developing and mature fruits. What are often inferred to be aborted seeds, in many cases, may not be seeds at all. They may be enlarged, unfertilized ovules.
Phylogeny and classification of Oleaceae based on rps16 and trnL‐F sequence data
Authors: Wallander Eva , Albert Victor A.
Published: April 2006

Phylogenetic relationships among 76 species of Oleaceae, representing all 25 recognized genera of the family, were assessed by a cladistic analysis of DNA sequences from two noncoding chloroplast loci, the rps16 intron and the trnL‐F region. Consensus trees from separate and combined analyses are congruent and agree well with nonmolecular data (chromosome numbers, fruit and wood anatomy, leaf glycosides, and iridoids). The two debated genera Dimetra and Nyctanthes, previously suggested to belong to Verbenaceae (sensu lato) or Nyctanthaceae, are shown to belong to Oleaceae, sister to the hitherto genus incertae sedis Myxopyrum. This clade is also supported by anatomical and chemical data. The subfamily Jasminoideae is paraphyletic, and a new classification is presented. The subfamily level is abandoned, and the former Jasminoideae is split into four tribes: Myxopyreae (Myxopyrum, Nyctanthes, and Dimetra), Fontanesieae (Fontanesia), Forsythieae (Abeliophyllum and Forsythia), and Jasmineae (Jasminum and Menodora). The tribe Oleeae (previous subfamily Oleoideae) is clearly monophyletic, comprising the subtribes Ligustrinae (Syringa and Ligustrum), Schreberinae status novus (Schrebera and Comoranthus), Fraxininae status novus (Fraxinus), and Oleinae (12 drupaceous genera). An rps16 sequence obtained from Hesperelaea, known only from the type specimen collected in 1875, confirmed the placement of this extinct taxon in the subtribe Oleinae.
Flowers, fruits, seeds, and pollen of Landeenia gen. nov., an extinct sapindalean genus from the Eocene of Wyoming
Authors: Manchester Steven R. , Hermsen Elizabeth J.
Published: April 2006

The new genus Landeenia is recognized on the basis of flowers, pollen, infructescences, fruits, and seeds from the middle Eocene of southwestern and northwestern Wyoming. Landeenia aralioides (MacGinitie) comb.nov. has cymose inflorescences with actinomorphic, bisexual flowers, a pentamerous calyx, about ten stamens, and a superior gynoecium of ∼18 carpels sharing a single style. The fruits are globose to oblate, loculicidally dehiscent capsules, with a persistent calyx, and contain flat, elliptical seeds that are surrounded by a small wing. Pollen removed from the anthers is tricolpate with finely striate sculpture. Although clearly dicotyledonous, the combination of characters found in Landeenia is not known in any modern genus. The familial affinities of the plant, though certainly not with the Araliaceae as previously thought, remain uncertain. However, the combination of characters is consistent with treatment as a member of the Sapindales. The fossil material is thus assigned to the rank of Sapindales‐Incertae sedis.
Biomechanical analysis of the Rolled (RLD) leaf phenotype of maize
Authors: Hay Jordan O. , Moulia Bruno , Lane Barbara , Freeling Michael , Silk Wendy K.
Published: April 2006

The pleiotropic effects of the Rld1‐O/+ mutation of Zea mays (Poaceae) on leaf phenotype include a suppression of normal transverse unrolling, a reversed top/bottom epidermal polarity, and an apparently straighter longitudinal shape. According to engineering shell theory, there might be mechanical coupling between transverse and longitudinal habit, i.e., the leaf rolling itself might produce the longitudinal straightening. We tested this possibility with quantitative curvature measurements and mechanical uncoupling experiments. The contributions of elastic bending under self weight, mechanical coupling, and rest state of leaf parts to the longitudinal and transverse habit were assessed in Rld1‐O/+ mutants and a population of sibling +/+ segregants. Elastic bending and curvature coupling are shown to be relatively unimportant. The Rld1‐O/+ mutation is shown to alter not only the unrolling process, but also the developmental longitudinal curving in the growing leaf, leading to a straighter midrib and a rolled lamina. The Rld1‐O/+ mutant is thus a suitable model to study the relation between tissue polarity and differential curvature development in the maize leaf. Since on the abaxial side of the leaf, more abundant sclerenchyma is found in +/+ than in Rld1‐O/+, a gradient in sclerification may contribute to the development of midrib curvature.
Genetic structure and AFLP variation of remnant populations in the rare plantPedicularis palustris(Scrophulariaceae) and its relation to population size and reproductive components
Authors: Schmidt Karola , Jensen Kai
Published: April 2006

We investigated plant reproduction in relation to genetic structure, population size, and habitat quality in 13 populations of the rare biennial plantPedicularis palustriswith 3–28500 flowering individuals. We used AFLP (amplified fragment length polymorphism) profiles to analyze genetic similarities among 129 individuals (3–15 per population). In a cluster analysis of genetic similarities most individuals (67%) were arranged in population‐specific clusters. Analysis of molecular variance indicated significant genetic differentiation among populations and among and within subpopulations (P< 0.001). Gene flow (Nem) was low (0.298). On average, plants produced 55 capsules, 17 seeds per fruit, and 42 seedlings in the following growing season. The number of seeds per capsule was independent of population size and of genetic variability. In contrast, the number of capsules per plant (P< 0.05) and the number of seedlings per plant (P< 0.05) were positively correlated with population size. The relation between population size and the number of seeds per plant was not significant (P= 0.075). The number of capsules and of seeds and seedlings per plant (P < 0.01) were positively correlated with genetic variability. Genetic variability was independent of actual population size, suggesting that historical population processes have to be taken into account, too. Stepwise multiple regressions revealed additional significant relationships of habitat parameters (soil pH, C:N ratio), vegetation composition, and standing crop on reproductive components. We conclude that populations ofP. palustrisare genetically isolated and that reproductive success most likely is influenced by population size, genetic variability, and habitat quality. Management strategies such as moderate grazing, mowing, and artificial gene flow should endeavor to increase population size as well as genetic variation.
The evolution of staminodes in angiosperms: patterns of stamen reduction, loss, and functional re‐invention
Authors: Walker‐Larsen Jennifer , Harder Lawrence D.
Published: April 2006

Stamens that have lost their primary function of pollen production, or staminodes, occur uncommonly within angiosperms, but frequently fulfill important secondary floral functions. The phylogenetic distribution of staminodes suggests that they typically arise during evolutionary reduction of the androecium. Differences in the genetic control and patterns of stamen loss between actinomorphic and zygomorphic flowers shape staminode development. In clades with actinomorphic flowers, staminodes generally replace an entire stamen whorl and staminode loss seems irreversible. In contrast, in clades with zygomorphic flowers staminodes evolve from a subset of the stamens in a whorl and staminodes can reappear in a lineage after being lost (e.g., Cheloneae, Scrophulariaceae). If staminodes do not adopt new functions during androecium reduction they are lost quickly, so that nonfunctional staminodes appear only in recently derived taxa. Alternatively, when staminodes assume new floral roles, either directly or indirectly after a nonfunctional period, they can become integral floral components which perpetuate within clades (e.g., Orchidaceae). Indirect evolution of staminode function allows greater flexibility of function by allowing staminodes to take over roles not performed by stamens, such as involvement in mechanisms to prevent self‐pollination and mechanisms of explosive pollination. Multifunctional staminodes characterize lineages with universal or widespread staminodes.
Reversion of flowering in Glycine Max (Fabaceae)
Authors: Washburn Carolyn F. , Thomas Judith F.
Published: April 2006

Photoperiodic changes, if occurring before a commitment to flowering is established, can alter the morphological pattern of plant development. In this study, Glycine max (L.) Merrill cv. Ransom plants were initially grown under an inductive short‐day (SD) photoperiod to promote flower evocation and then transferred to a long‐day (LD) photoperiod to delay flower development by reestablishing vegetative growth (SD–LD plants). Some plants were transferred back to SD after 4‐LD exposures to repromote flowering (SD–LD–SD plants). Alterations in organ initiation patterns, from floral to vegetative and back to floral, are characteristic of a reversion phenomenon. Morphological features that occurred at the shoot apical meristem in SD, LD, SD–LD, and SD–LD–SD plants were observed using scanning electron microscopy (SEM). Reverted plants initiated floral bracts and resumed initiation of trifoliolate leaves in the two‐fifths floral phyllotaxy prior to terminal inflorescence development. When these plants matured, leaf‐bract intermediates were positioned on the main stem instead of trifoliolate leaves. Plants transferred back to a SD photoperiod flowered earlier than those left in LD conditions. Results indicated that in plants transferred between SDs and LDs, photoperiod can influence organ initiation in florally evoked, but not committed, G. max plants.
Size‐dependent flowering behavior and heat production of a sequential hermaphrodite, Symplocarpus renifolius (Araceae)
Authors: Wada Naoya , Uemura Shigeru
Published: April 2006

We examined the flowering performance in a population of the protogynous perennial herb Symplocarpus renifolius (Araceae), with special consideration of plant size. Flowering of S. renifolius occurred in very early spring, soon after snow melt. The spadices generated heat throughout the pistillate (female) and bisexual phases, but heat production decreased quickly after the beginning of the staminate (male) phase. During the flowering season, the sex ratio within the population dramatically changed from a dominance of females to a dominance of males. The duration of the female phase was negatively correlated with the onset time of flowering, and the duration of the male phase was positively correlated with plant size. Larger plants began blooming earlier, produced more heat, made the transition from female to male phase more rapidly, and lasted longer as males than smaller ones. Such size‐dependent flowering performance caused unidirectional pollen flow from large to small plants. The number of seeds produced per spadix was positively correlated with the duration of the female phase, although it was not correlated with plant size. However, the estimated number of seeds sired during the male phase was positively correlated with plant size. Early flowering, rapid gender change, and higher heat production of the spadices by larger plants were factors considered to promote the higher success of the male function without decreasing the success of the female function.
Pollination biology of two chiropterophilous agaves in Arizona
Authors: Slauson Liz A.
Published: April 2006

I studied the pollination biology of two closely related species of agave, Agave palmeri and A. chrysantha (Agavaceae), which exhibit several chiropterophilous (bat‐pollinated) traits. Floral studies, floral visitor observations, and pollination studies were conducted over four summers at six different sites to examine floral traits and determine the relative importance of diurnal vs. nocturnal pollinators. Agave chrysantha appears to have developed minor shifts in several floral characters that enhance diurnal pollination. Although floral shifts towards diurnal pollination were fewer in A. palmeri, stigmas were diurnally receptive and copious floral rewards were available in the morning, indicating that some adaptations exist to allow for multiple pollinators. Differences in fruit and seed set between naturally day‐ and night‐pollinated umbels for both species were either not significant or significantly higher in day‐pollinated plants. Bats were not important pollinators of A. chrysantha, and the mutualistic relationship between A. palmeri and the lesser long‐nosed bat was found to be asymmetric. “Bat‐adapted” floral traits appear to be flexible enough to respond to the climatic and pollinator unpredictability experienced by agaves at the northern edge of their distribution. This variability may be a more important factor affecting evolution of floral characters than a particular pollinator.
Pollen quality limits seed set in Burchardia umbellata (Colchicaceae)
Authors: Ramsey Mike , Vaughton Glenda
Published: April 2006

In self‐incompatible plants, interference by self pollen or genetically related pollen can potentially exacerbate pollen limitation, although this has rarely been demonstrated. We examined the breeding system, pollen limitation, and pollen interference using self‐ and cross‐ pollinations and pollen supplementations in Burchardia umbellata, an insect‐pollinated lilioid monocot. Ovule fertilization and seed set were less following selfing than crossing (22 vs. 78% and 4 vs. 73%, respectively), indicating partial self‐incompatibility. Flowers were partially protandrous, and flowers opened concurrently on plants potentially allowing self pollen interference. Natural seed set was pollen limited and varied within and among years, probably due to variation in flowering plant density. Interference by self or genetically related pollen caused pollen limitation as evidenced by increased seed set of bagged cross‐pollinated plants compared to unbagged pollen‐supplemented plants in two years. In 1996, both fertilization and seed set increased in response to cross‐pollination, indicating that interference occurred in the style and ovary. In 1997, only seed set increased after cross‐pollination indicating that interference occurred in the ovary. Inappropriate pollen deposition may contribute to pollen limitation more often than previously recognized and should select for floral traits that decrease deposition of self or related pollen.
Phylogenetic resolution within the tribe Episcieae (Gesneriaceae): congruence of ITS and NDHF sequences from parsimony and maximum‐likelihood analyses
Authors: Smith James F.
Published: April 2006

Generic relationships within Episcieae were assessed using ITS and ndhF sequences. Previous analyses of this tribe have focussed only on ndhF data and have excluded two genera, Rhoogeton and Oerstedina, which are included in this analysis. Data were analyzed using both parsimony and maximum‐likelihood methods. Results from partition homogeneity tests imply that the two data sets are significantly incongruent, but when Rhoogeton is removed from the analysis, the data sets are not significantly different. The combined data sets reveal greater strength of relationships within the tribe with the exception of the position of Rhoogeton. Poorly or unresolved relationships based exclusively on ndhF data are more fully resolved with ITS data. These resolved clades include the monophyly of the genera Columnea and Paradrymonia and the sister‐group relationship of Nematanthus and Codonanthe. A closer affinity between Neomortonia nummularia and N. rosea than has previously been seen is apparent from these data, although these two species are not monophyletic in any tree. Lastly, Capanea appears to be a member of Gloxinieae, although C. grandiflora remains within Episcieae. Evolution of fruit type, epiphytic habit, and presence of tubers is re‐examined with the new data presented here.
Biased sex ratios in the dioecious annual Croton texensis (Euphorbiaceae) are not due to environmental sex determination
Authors: Decker Karin L. , Pilson Diana
Published: April 2006

At Arapaho Prairie, in the sandhills of western Nebraska, the dioecious annual Croton texensis (Euphorbiaceae) exhibits biased sex ratios. Moreover, the direction of bias changes from year to year: in 1994 the study population was significantly female biased, in 1995 and 1996 it was significantly male biased, and in 1997 and 1998 the sex ratio did not differ from 1 : 1. Such variation in the observed sex ratio in plants is frequently attributed to environmental sex determination (ESD), which is favored by natural selection if the rate of fitness gain across an environmental gradient is greater for one sex than the other. We performed experiments to determine: (1) whether variation in the sex ratio is correlated with environmental conditions, as would be expected if ESD is operating, and (2) whether ESD, if present, would be favored by natural selection. In a common garden experiment in which water and fertilizer were manipulated the sex ratio was marginally male biased in treatments in which water was added, but not different from 1 : 1 in other treatments. In field plots into which seeds were planted none of several soil characteristics, nor overall plot quality for C. texensis (measured as average plant biomass) were correlated with plot sex ratio. However, plots in which a large number of planted seeds emerged tended to be female biased. These results provide very weak evidence for sex ratio bias across an environmental gradient, and thus provide little evidence for ESD. Moreover, sex‐by‐environment interactions for fitness, which are required for the evolution of ESD, were absent for all measured variables. Thus, ESD does not appear to be favored by natural selection in this population. Instead, these biases may have been caused by differences between the sexes in germination and/or early mortality.