bluuebunny/crossref_metadata_2025 huggingface dataset:
Clonal variation in floral stage timing in the common dandelion Taraxacum officinale (Asteraceae)
Authors: Collier Matthew H. , Rogstad Steven H.
Published: February 2008

We investigated the hypothesis that dandelion clones (Taraxacum officinale Weber, sensu lato; Asteraceae) differ in their floral stage timing characteristics under a constant set of environmental conditions. To test this hypothesis, plants representing nine different dandelion clones (identified by DNA fingerprinting) were grown in groups of five (N = 45) in a growth chamber for a period of 8 mo, with chamber settings similar to environmental conditions at peak dandelion flowering time for their population sites. Five flowering phenology parameters were monitored daily for a total of 301 buds developing during this time: (1) time to bud; (2) time to full opening and inflorescence maturation (i.e., first anthesis); (3) time to re‐closure of an inflorescence; (4) time to fruit (full re‐opening of the inflorescence); and (5) total flowering time. Scape length at the appearance of a fully expanded infructescence was also measured for each individual. Significant differences in mean time to inflorescence, mean time to re‐closure, mean time to fruit, and mean total flowering time were revealed among some dandelion clones (Kruskal‐Wallis, P ≤ 0.0005). No differences in mean number of inflorescence buds per plant (P = 0.2217), mean time to bud (P = 0.2396), or mean scape length (P = 0.3688) were detected among the nine clones. These results suggest that differences in floral stage timing may in part involve varying genotypic environmental response characteristics and that these differences may have potential fitness effects. Further research is needed to determine if such clonal differences are observed under a broader range of uniform environmental conditions.
A phylogeny of legumes (Leguminosae) based on analysis of the plastidmatKgene resolves many well‐supported subclades within the family
Authors: Wojciechowski Martin F. , Lavin Matt , Sanderson Michael J.
Published: February 2008

Phylogenetic analysis of 330 plastidmatKgene sequences, representing 235 genera from 37 of 39 tribes, and four outgroup taxa from eurosids I supports many well‐resolved subclades within the Leguminosae. These results are generally consistent with those derived from other plastid sequence data (rbcLandtrnL), but show greater resolution and clade support overall. In particular, the monophyly of subfamily Papilionoideae and at least seven major subclades are well‐supported by bootstrap and Bayesian credibility values. These subclades are informally recognized as theCladrastisclade, genistoid sensu lato, dalbergioid sensu lato, mirbelioid, millettioid, and robinioid clades, and the inverted‐repeat‐lacking clade (IRLC). The genistoid clade is expanded to include genera such asPoecilanthe,Cyclolobium,Bowdichia, andDiplotropisand thus contains the vast majority of papilionoids known to produce quinolizidine alkaloids. The dalbergioid clade is expanded to include the tribe Amorpheae. The mirbelioids include the tribes Bossiaeeae and Mirbelieae, with Hypocalypteae as its sister group. The millettioids comprise two major subclades that roughly correspond to the tribes Millettieae and Phaseoleae and represent the only major papilionoid clade marked by a macromorphological apomorphy, pseudoracemose inflorescences. The robinioids are expanded to includeSesbaniaand members of the tribe Loteae. The IRLC, the most species‐rich subclade, is sister to the robinioids. Analysis of thematKdata consistently resolves but modestly supports a clade comprising papilionoid taxa that accumulate canavanine in the seeds. This suggests a single origin for the biosynthesis of this most commonly produced of the nonprotein amino acids in legumes.
Phylogenetic relationships of Malvatheca (Bombacoideae and Malvoideae; Malvaceae sensu lato) as inferred from plastid DNA sequences
Authors: Baum David A. , DeWitt Smith Stacey , Yen Alan , Alverson William S. , Nyffeler Reto , Whitlock Barbara A. , Oldham Rebecca L.
Published: February 2008

Previous molecular phylogenetic analyses have revealed that elements of the former families Malvaceae sensu stricto and Bombacaceae together form a well‐supported clade that has been named Malvatheca. Within Malvatheca, two major lineages have been observed; one, Bombacoideae, corresponds approximately to the palmate‐leaved Bombacaceae, and the other, Malvoideae, includes the traditional Malvaceae (the mallows or Eumalvoideae). However, the composition of these two groups and their relationships to other elements of Malvatheca remain a source of uncertainty. Sequence data from two plastid regions, ndhF and trnK/matK, from 34 exemplars of Malvatheca and six outgroups were analyzed. Parsimony, likelihood, and Bayesian analyses of the sequence data provided a well‐resolved phylogeny except that relationships among five lineages at the base of Malvatheca are poorly resolved. Nonetheless, a 6‐bp insertion in matK suggests that Fremontodendreae is sister to the remainder of Malvatheca. Our results suggest that the Malvoideae originated in the Neotropics and that a mangrove taxon dispersed across the Pacific from South America to Australasia and later radiated out of Australasia to give rise to the ca. 1700 living species of Eumalvoideae. Local clock analyses imply that the plastid genome underwent accelerated molecular evolution coincident with the dispersal out of the Americas and again with the radiation into the three major clades of Eumalvoideae.
Phylogeny and infrageneric classification ofSymplocos(Symplocaceae) inferred from DNA sequence data
Authors: Wang Yuguo , Fritsch Peter W. , Shi Suhua , Almeda Frank , Cruz Boni C. , Kelly Lawrence M.
Published: February 2008

Symplocoscomprises ∼300 species of woody flowering plants with a disjunct distribution between the warm‐temperate to tropical regions of eastern Asia and the Americas. Phylogenetic analyses of 111 species ofSymplocosbased on the nuclear ribosomal internal transcribed spacer (ITS) region and the chloroplast genesrpl16,matK, andtrnL–trnFyielded topologies in which only one of the four traditionally recognized subgenera (Epigenia; Neotropics) is monophyletic. SectionCordyloblaste(subgenusSymplocos; eastern Asia) is monophyletic and sister to a group comprising all other samples ofSymplocos. SectionPalura(subgenusHopea; eastern Asia) is sister to a group comprising all other samples ofSymplocosexcept those of sectionCordyloblaste.Symplocos wikstroemiifolia(eastern Asia) andS. tinctoria(southeastern United States), both of subgenusHopea, form a clade that groups withS. longipes(tropical North America) and the species of subgenusEpigenia. The remaining samples of subgenusHopea(eastern Asia) form a clade. SectionNeosymplocos(subgenusMicrosymplocos; Neotropics) is well nested within a clade otherwise comprising the samples of sectionSymplocastrum(subgenusSymplocos; Neotropics). SectionUrbaniocharis(subgenusMicrosymplocos; Antilles) groups as sister to the clade comprisingSymplocastrumandNeosymplocos. The data support the independent evolution of deciduousness among sectionPaluraandS. tinctoria. The early initial divergence of sectionsCordyloblasteandPalurafrom the main group warrants their recognition at taxonomic levels higher than those at which they are currently placed. An inferred eastern Asian origin forSymplocoswith subsequent dispersal to the Americas is consistent with patterns from other phylogenetic studies of eastern Asian‐American disjunct plant groups but contrary to a North American origin inferred from the earliest fossil occurrences of the genus.
Recovery from drought stress in Lolium perenne (Poaceae): are fungal endophytes detrimental?
Authors: Cheplick Gregory P.
Published: February 2008

Perennial ryegrass (Lolium perenne) is a cool‐season, perennial species widely used for forage and turf. It is often infected by a clandestine, endophytic fungus (Neotyphodium lolii) that has the potential to affect host growth responses to abiotically stressful conditions. In some species, the grass‐endophyte symbiosis is mutualistic, but the relationship is reported to be contingent on environmental conditions and host genotype in L. perenne. The objective of this research was to determine the potential effects of endophyte infection on recovery from severe drought stress in variable genotypes of a perennial ryegrass cultivar. Sixteen infected (+E) and 16 uninfected (−E) ramets were planted in the greenhouse for each of 10 ryegrass genotypes. Eight +E and eight −E plants per genotype were exposed to three sequential droughts where water was withheld for 11–14 d, resulting in <5% soil moisture; the others (control) were watered as needed. Response variables were tiller numbers 1 wk and 4 wk after drought, and leaf area and dry mass of shoots and roots 7 wk after drought. In both control and drought, −E plants had more tillers, and greater leaf area and total mass, than +E plants, suggesting a detrimental effect of endophytic fungi. Fungal hyphae survived the drought and were abundant in post‐drought, +E plants. The effects of endophytes were specific for particular host genotypes, as exemplified by significant genotype × endophyte interactions. Root : shoot ratio and percent of mass allocated to tiller bases (a rough measure of resource storage) showed genotype × endophyte × drought interactions. There was plasticity for root : shoot ratio and genetic variation in the ability to restore root growth during recovery from drought. For 7 of 10 genotypes, −E plants showed an equal or greater allocation to tiller bases than +E plants following drought recovery, illustrating a cost to endophyte infection for some genotypes. The symbiotic relationship between L. perenne and its endophyte primarily benefits the fungus, not the host, under many environmental conditions.
Genetic diversity of the narrow endemic Astragalus oniciformis (Fabaceae)
Authors: Alexander J. Andrew , Liston Aaron , Popovich Steve J.
Published: February 2008

Astragalus oniciformis Barneby is a narrow endemic xerophyte of the upper Snake River Plain of central Idaho, USA, where it inhabits stabilized, aeolian sand deposits and previously burned, sandy sites over Quaternary basalt flows. The objective of this study was to determine the levels and distribution of genetic differentiation within and among populations of A. oniciformis. Fifteen individuals from each of eight populations, chosen from throughout the range of the species, were selected based on accessibility, density of individuals, and large population size. Inter‐simple sequence repeats were chosen as the marker to assess genetic differentiation. The two primers selected yielded 40 polymorphic loci in A. oniciformis. In an analysis of molecular variance, 88.69% of the variation was significantly attributed to variation within populations. High gene flow (Nm = 3.91–3.93; SD = 0.01) and a low percentage deviation from Hardy‐Weinberg equilibrium due to population subdivision (GST = 0.113–0.1134; SD = 0.0002) were found among sampled populations. These results suggest that current threats to this species, including changing fire patterns and habitat loss from grazing disturbance, have not yet affected the genetic diversity of this species. Preservation of large populations and smaller, intervening, dispersed patches will help preserve the genetic integrity and the genetic diversity found in A. oniciformis.
Cryptic species in an endangered pondweed community (Potamogeton, Potamogetonaceae) revealed by AFLP markers
Authors: Whittall Justen B. , Hellquist C. Barre , Schneider Edward L. , Hodges Scott A.
Published: February 2008

Cryptic species are morphologically indistinguishable, yet reproductively isolated. Morphological boundaries between species can also be obscured by hybridization and clonality. Determining the roles of reproductive isolation, hybridization, and clonality in morphologically indistinguishable taxa is essential to determining appropriate species‐level taxonomic rankings for conservation purposes. The taxonomic status of the endangered Little Aguja pondweed of west Texas, Potamogeton clystocarpus, is uncertain due to a lack of fixed morphological differences between it and two sympatric congeners. Morphology, amplified fragment length polymorphisms (AFLPs), and sequences of the internal transcribed spacer (ITS) region and trnL‐F intron and spacer were used to determine the degree of genetic distinctiveness, hybridization and clonality for this rare species. AFLPs indicate that P. clystocarpus is a genetically distinct lineage compared to P. pusillus and P. foliosus. No hybrids involving P. clystocarpus were detected, but two putative hybrids involving P. pusillus and P. foliosus were identified. Clonal growth was only detected in P. pusillus. A combination of morphological and molecular markers was successful in determining the genetic distinctiveness of an endangered cryptic species, Potamogeton clystocarpus. Further sampling in this and adjacent drainages is necessary to assess the degree of endemism of P. clystocarpus and confidently rule out hybridization and clonality in this taxon.
Life history, floral development, and mating system in Clarkia xantiana (Onagraceae): do floral and whole‐plant rates of development evolve independently?
Authors: Mazer Susan J. , Paz Horacio , Bell Michael D.
Published: February 2008

Autogamously self‐fertilizing taxa have evolved from outcrossing progenitors at least 12 times in the annual wildflower genus, Clarkia (Onagraceae). In C. xantiana, individuals of the selfing subspecies (ssp. parviflora) flower at an earlier age, produce successive flowers more rapidly, and produce flowers that complete their development more rapidly than their outcrossing counterparts (ssp. xantiana). Two hypotheses have been proposed to explain the joint evolution of these whole‐plant and individual floral traits. The accelerated life cycle hypothesis proposes that selection favoring a short life cycle in environments with short growing seasons (such as those typically occupied by parviflora) has independently favored genotypes with early reproduction, synchronous flower production, and rapidly developing, self‐fertilizing flowers. The correlated response to selection hypothesis similarly proposes that selection in environments with short growing seasons favors early reproduction, but that rapid floral development and increased selfing evolve as correlated responses to selection due to genetic linkage (or pleiotropy) affecting both whole‐plant and floral development. We conducted a greenhouse experiment using maternal families from two field populations of each subspecies to examine covariation between floral and whole‐plant traits within and among populations to seek support for either of these hypotheses. Our results are consistent with the accelerated life cycle hypothesis but not with the correlated response to selection hypothesis.
Gene flow betweenImpatiens radicansandI. javensis(Balsaminaceae) in Gunung Pangrango, central Java, Indonesia
Authors: Tsukaya Hirokazu
Published: February 2008

This study reports the natural hybridization of two species ofImpatiensin the mountain forests of Gunung Gede‐Pangrango, in central Java, Indonesia.Impatiens radicans, which inhabits the highest altitude zone in the mountains of this park, andI. javensis, which inhabits a zone of lower altitude, can be easily distinguished by their morphological features. However, some populations that inhabit regions between the two zones have characteristics that appear to be combinations of traits ofI. radicansandI. javensis. Sequence analysis of the 800‐bp nuclearITSregion and 449‐bp plastidtrnL‐Flocus demonstrated that hybridization between the two species has occurred, and suggests gene flow between the species.
Identification of a novel gene, HAABRC5, from Helianthus annuus (Asteraceae) that is upregulated in response to drought, salinity, and abscisic acid
Authors: Liu Xianan , Vance Baird Wm.
Published: February 2008

Using differential display of mRNA transcripts, we obtained a partial cDNA clone, RSC5‐U, that is upregulated by exposure to high salinity. A longer cDNA of 812 nucleotides, designated HaABRC5, was then cloned by rapid amplification of cDNA ends. This full‐length cDNA contains an open reading frame of 423 nucleotides encoding 141 amino acids, including a “bipartite nuclear targeting sequence.” The deduced amino acid sequence had no similarity to known genes in the database. The expression of HaABRC5 was investigated in more detail using quantitative reverse transcriptase‐polymerase chain reaction. HaABRC5 is upregulated by drought, high salinity, and exogenous application of abscisic acid (ABA). The promoter sequence of 229 nucleotides, upstream of HaABRC5, was cloned using rapid amplification of genomic ends. Three ABA‐responsive elements were found within the HaABRC5 promoter region. Therefore, HaABRC5 is probably an ABA‐responsive nuclear protein playing a role in plant stress response.
Seed production from the mixed mating system of Chesapeake Bay (USA) eelgrass (Zostera marina; Zosteraceae)
Authors: Rhode Jennifer M. , Emmett Duffy J.
Published: February 2008

In monoecious plants, gametes can be exchanged in three ways: among unrelated genets (outbreeding), with close relatives (inbreeding), or within individuals (geitonogamous selfing). These different mating systems may have consequences for population demography and fitness. The experiment presented herein used artificial crosses to examine the mating system of Chesapeake Bay, Virginia, USA eelgrass (Zostera marina L; Zosteraceae), a bisexual submerged aquatic plant that can outbreed, inbreed, and self. Genetic data indicate severe heterozygosity deficiencies and patchy genotype distribution in these beds, suggesting that plants therein reproduce primarily by vegetative propagation, autogamy, or geitonogamy. To clarify eelgrass reproductive strategies, flowers from three genetically and geographically distinct beds were hand‐pollinated in outbred, inbred, and selfed matings. Fertilization success and seed production, life history stages which contribute greatly to the numeric maintenance of populations, were monitored. We found no evidence that inbreeding had negative consequences for seed production. On the contrary, selfed matings produced seeds significantly more frequently than outcrossed matings and produced significantly larger numbers of seeds than either inbred or outbred matings. These results contrast with patterns for eelgrass in other regions but might be expected for similar populations in which pollen limitation or a short reproductive season renders selfing advantageous.
Phylogenetics and biogeography of the neotropical fern genera Jamesonia and Eriosorus (Pteridaceae)
Authors: Sánchez‐Baracaldo Patricia
Published: February 2008

Jamesonia and Eriosorus are two traditionally recognized fern genera in the Neotropics that together form a monophyletic group. Molecular phylogenetic analyses for this study suggest, however, that neither genus is itself monophyletic and that several independent lineages with the jamesonia morphotype have each undergone a fairly recent radiation in páramo ecosystems. A robust phylogeny was generated based on sequence data of the nuclear external transcribed spacer (ETS) of 18S–26S rDNA, the plastid gene rps4 and the intergenic spacer rps4‐trnS. Several conclusions can be made concerning the evolutionary history and biogeographic patterns of the Jamesonia‐Eriosorus complex: (1) “jamesonia” is polyphyletic, making “eriosorus” paraphyletic; (2) all analyses recover three major clades in the Andes; (3) two well‐supported clades can be recognized, corresponding to the northern vs. central Andes; and (4) the sister taxon of the Andean radiation is the Brazilian taxon Eriosorus myriophyllus. Jamesonia is a potential example of a recent adaptive radiation because the group is characterized as being morphologically and ecologically diverse and its habitat is of recent origin.
Comparative analysis of leaf shape development in Eschscholzia californica and other Papaveraceae‐Eschscholzioideae
Authors: Gleissberg Stefan
Published: February 2008

Dissected leaves in Papaveraceae‐Eschscholzioideae have an architecture frequently encountered in the basal eudicot clade Ranunculales that could represent an ancestral condition for eudicots. Developmental morphology of foliage leaves was investigated using scanning electron microscopy and focusing on primordium formation activity (primary morphogenesis) at the leaf margin. Eschscholzia californica, E. lobii, and Hunnemannia fumariaefolia had a polyternate‐acropetal mode of leaf dissection. Segment formation continued around the whole leaf blade periphery. Differences in mature leaf architecture was traced to variations in regional blastozone activity and duration. Epidermal cell size measurements in E. californica indicated that the leaf tip tissue starts to differentiate already at the onset of organogenic activity and that tip cells remain larger than epidermal cells at the basal margins during further growth. It is argued that early differentiation of the tip does not set up a general basipetal differentiation gradient, but is a local effect that allows acropetal pinna initiation to occur in subapical blastozones. In Dendromecon, secondarily entire leaves have evolved through the loss of primordium formation activity. Marginal corrugations found in Dendromecon form late in development and are not reminiscent of lateral primordia.
Floral development and molecular phylogeny support the generic status of Tasmannia (Winteraceae)
Authors: Doust Andrew N. , Drinnan Andrew N.
Published: February 2008

The taxonomic status of and evolutionary relationship between Tasmannia and Drimys (Winteraceae) have been subjects of controversy for many years. In this paper, a molecular phylogenetic analysis of the family with sequences of previously unpublished Tasmannia and Drimys species confirms earlier conclusions that Tasmannia and Drimys do not form a monophyletic group, despite the fact that they appear to share distinctive inflorescence and floral morphological attributes. Examination of alternative hypotheses of relationships with likelihood‐ratio tests and parametric bootstrapping supports the separation of Tasmannia and Drimys. A detailed analysis of floral development in Tasmannia lanceolata and T. xerophila indicates that timing and position of sepal initiation differs between them, but that the position of subsequent organ initiation predictably follows from sepal position. This is in contrast to Drimys winteri, where a prolonged delay between sepal and petal initiation leads to the production of many phyllotactic patterns. The prolonged period of calyx tube growth leading to the formation of a calyptra in Tasmannia and Drimys probably evolved in parallel in the two lineages.
Ontogeny of triovulate cones of Ephedra intermedia and origin of the outer envelope ofovules of Ephedraceae
Authors: Yang Yong
Published: February 2008

The origin of the two envelopes of ovules of extant species of Ephedraceae has been discussed previously in different ways based only on investigation of bimerous female cones. To generalize the characteristics of the two envelopes, ontogenetic and metamorphic patterns of the two envelopes of ovules of trimerous female cones of Ephedra intermedia Schrenk et C. A. Meyer were studied using scanning electron microscopy. The outer envelope of the ovules of triovulate female cones of Ephedra intermedia is initiated as two adaxial lateral protuberances. Thus, the outer envelope of extant Ephedraceae may have been derived from three foliar components of the second proximal whorl of the secondary reproductive shoot of the ancestral compound female cone. Two adaxial lateral foliar components likely gave rise to the outer envelope by fusion, while the third abaxial foliar component was reduced. These new findings suggest that the Gnetales derived their female cones from trimerous multiaxial female reproductive organs of their progenitors. Some evolutionary aspects of female cones of Ephedra are also discussed.
Analysis of circular bordered pit function II. Gymnosperm tracheids with torus‐margo pit membranes
Authors: Hacke Uwe G. , Sperry John S. , Pittermann Jarmila
Published: February 2008

A model of xylem conduit function was applied to gymnosperm tracheids with torus‐margo pit membranes for comparison with angiosperm vessels. Tracheids from 17 gymnosperm tree species with circular bordered pits and air‐seed pressures from 0.8 to 11.8 MPa were analyzed. Tracheids were more reinforced against implosion than vessels, consistent with their double function in transport and support. Tracheid pits were 3.3 to 44 times higher in hydraulic conductivity than vessel pits because of greater membrane conductivity of the torus‐margo configuration. Tight scaling between torus and pit size maximized pit conductivity. Higher pit conductivity allowed tracheids to be 1.7–3.4 times shorter than vessels and still achieve 95% of their lumen‐limited maximum conductivity. Predicted tracheid lengths were consistent with measured lengths. The torus‐margo structure is important for maximizing the conductivity of the inherently length‐limited tracheid: replacing the torus‐margo membrane with a vessel membrane caused stem tracheid conductivity to drop by 41%. Tracheids were no less hydraulically efficient than vessels if they were long enough to reach their lumen‐limiting conductivity. However, this may only be possible for lumen diameters below approximately 60–70 μm.
Evolution of obligate pollination mutualism in New Caledonian Phyllanthus (Euphorbiaceae)
Authors: Kawakita Atsushi , Kato Makoto
Published: February 2008

About half a dozen obligate pollination mutualisms between plants and their seed‐consuming pollinators are currently recognized, including fig–fig wasp, yucca–yucca moth, and the recently discovered Glochidion tree–Epicephala moth mutualisms. A common principle among these interactions is that the pollinators consume only a limited amount of the seed crop within a developing fruit (or fig in the case of fig–fig wasp mutualism), thereby ensuring a net benefit to plant reproduction. A novel obligate, seed‐parasitic pollination mutualism between two species of New Caledonian Phyllanthus (Euphorbiaceae), a close relative of Glochidion, and Epicephala moths (Gracillariidae) is an exception to this principle. The highly specialized flowers of Phyllanthus are actively and exclusively pollinated by species‐specific Epicephala moths, whose larvae consume all six ovules of the developing fruit. Some flowers pollinated by the moths remain untouched, and thus a fraction of the fruits is left intact. Additional evidence for a similar association of Epicephala moths in other Phyllanthus species suggests that this interaction is a coevolved, species‐specific pollination mutualism. Implications for the evolutionary stability of the system, as well as differences in mode of interaction with respect to the Glochidion–Epicephala mutualism, are discussed.
Allometric gender allocation in Ambrosia Artemisiifolia (Asteraceae) has adaptive plasticity
Authors: Paquin Viviane , Aarssen Lonnie W.
Published: February 2008

Evidence is reported for size‐dependent (allometric) gender allocation in the monoecious, wind‐pollinated annual Ambrosia artemissifolia. Consistent with established theory, the pattern of allometry displayed adaptive plasticity, depending on the environmental cause of variation in plant size. Plant size gradients were generated in both field and greenhouse experiments using separate and combined gradients of shading, soil nutrient levels, and neighbor proximity. When plant size constraints involved light limitation from shading (e.g., because of close neighbor proximity), decreasing plant size was generally associated with decreasing maleness and increasing femaleness (based on relative male and female flower production, respectively). This is consistent with the “pollen‐dispersal” hypothesis in which the consequences of relatively small plant size (among larger neighbors) imposes less severe limitation for female reproductive success than for male reproductive success (because success as an outcrossing donor of wind‐dispersed pollen increases with increasing plant height, especially when neighbors are present). However, when size was constrained by soil nutrient limitation alone (i.e., without shading effects), the results had the converse allometric relationship; i.e., decreasing plant size was generally associated with increasing maleness and decreasing femaleness. This is consistent with the “size‐advantage” and “time‐limitation” hypotheses in which energetic and time limitations (respectively) associated with relatively small plant size impose a less severe limitation for male reproductive success than for female reproductive success.
The intertidal marine lichen formed by the pyrenomycete fungus Verrucaria tavaresiae (Ascomycotina) and the brown alga Petroderma maculiforme (Phaeophyceae): thallus organization and symbiont interaction
Authors: Sanders William B. , Moe Richard L. , Ascaso Carmen
Published: February 2008

The thallus formed by the marine pyrenomycete fungus Verrucaria tavaresiae and the phaeophycean alga Petroderma maculiforme was studied to elucidate the organization of the symbionts, determine the type of cellular contacts between them, and evaluate the status of the symbiosis as a lichen. Hand‐sectioned and resin‐embedded samples were examined with light and transmission electron microscopy. Within the uppermost portion of the cellular fungal tissue, separate algal filaments were arranged anticlinally. Protrusions of the fungal cell wall penetrated into adjacent algal walls but did not enter the cell lumen. A striking feature of these penetrations was the frequent separation of algal cell wall layers and insertion of fungal wall material between them. Algal filaments grew downward intrusively between fungal cells, often penetrating deeply into the fungal cell wall. Despite the exceptional nature of the phycobiont involved, the Verrucaria tavaresiae–Petroderma maculiforme symbiosis unequivocally fits the prevailing concept of a lichen. The distinctive interpenetrations observed between symbionts may be related to the integration of their different growth forms within a coherent tissue regularly subject to mechanical stresses. Periclinal cell divisions within and just below the algal layer may serve to replenish surface tissues lost to abrasion and herbivory.
Viability and longevity of pollen from transgenic and nontransgenic tall fescue (Festuca arundinacea) (Poaceae) plants
Authors: Wang Zeng‐Yu , Ge Yaxin , Scott Megann , Spangenberg German
Published: February 2008

Pollen is an important vector of gene flow in plants, particularly for outcrossing species like tall fescue. Several aspects of pollination biology were investigated using pollen from transgenic and nontransgenic plants of tall fescue (Festuca arundinacea Schreb.), the most important forage species worldwide of the Festuca genus. To effectively assess in vitro pollen viability in tall fescue, an optimized germination medium (0.8 mol/L sucrose, 1.28 mmol/L boric acid and 1.27 mmol/L calcium nitrate) was developed. Treatment with relatively high temperatures (36° and 40°C) and high doses of UV‐B irradiation (900–1500 μW/cm2) reduced pollen viability, while relative humidity did not significantly influence pollen viability. Viability of pollen from transgenic progenies (T1 and T2) was similar to that from seed‐derived control plants. Pollen from primary transgenics (T0) and primary regenerants (R0) had various levels of viability. Hand pollination using the primary regenerants and transgenics revealed that no seed set could be obtained when pollen viability was lower than 5%. Pollen from transgenic progenies and nontransgenic control plants could survive up to 22 h under controlled conditions in growth chamber. However, under sunny atmospheric conditions, viability of transgenic and nontransgenic pollen reduced to 5% in 30 min, with a complete loss of viability in 90 min. Under cloudy atmospheric conditions, pollen remained viable up to 240 min, with about 5% viability after 150 min. This report is the first on pollen viability and longevity in transgenic forage grasses and could be useful for risk assessment of transgenic plants.
DNA sequences from Miocene fossils: anndhFsequence ofMagnolia latahensis(Magnoliaceae) and anrbcLsequence ofPersea pseudocarolinensis(Lauraceae)
Authors: Kim Sangtae , Soltis Douglas E. , Soltis Pamela S. , Suh Youngbae
Published: February 2008

We report a partialndhFsequence (1528 bp) ofMagnolia latahensisand a partialrbcLsequence (699 bp) ofPersea pseudocarolinensisfrom the Clarkia fossil beds of Idaho, USA (Miocene; 17–20 million years [my] BP). ThendhFsequence fromM. latahensiswas identical to those of extantM. grandiflora,M. schiediana,M. guatemalensis, andM. tamaulipana. Parsimony analysis of thendhFsequence ofM. latahensisand previously reportedndhFsequences for Magnoliaceae placedM. latahensiswithinMagnoliaas a member of the Theorhodon clade. This result is reasonable considering that: (1) the morphology ofM. latahensisis very similar to that of extantM. grandiflora, and (2) a recent molecular phylogenetic study of Magnoliaceae showed that the maximum sequence divergence ofndhFamong extant species is very low (1.05% in subfamily Magnolioideae) compared with other angiosperm families. We reanalyzed the previously reportedrbcLsequence ofM. latahensiswith sequences for all major lineages of extant Magnoliales and Laurales. This sequence is sister toLiriodendron, rather than grouped with a close relative ofM. grandifloraas predicted by morphology and the results of thendhFanalysis, possibly due to a few erroneous base calls in the sequences. TherbcLsequence ofP. pseudocarolinensisdiffered fromrbcLof extantPerseaspecies by 3–6 nucleotides and fromrbcLof extantSassafras albidumby two nucleotides. Phylogenetic analyses ofrbcLsequences for all major lineages of Magnoliales and Laurales placed the fossilP. pseudocarolinensiswithin Lauraceae and as sister toS. albidum. These results reinforce the suggestion that Clarkia and other similar sites hold untapped potential for molecular analysis of fossils.
The development of the superior ovary in Tetraplasandra (Araliaceae)
Authors: Costello Annemarie , Motley Timothy J.
Published: February 2008

Tetraplasandra is a small Hawaiian genus of seven species with remarkable diversity in ovary position, ranging from inferior to completely superior. Tetraplasandra gymnocarpa is the only member of the Araliaceae with a fully superior ovary. A comparative study of floral anatomy and development in superior and inferior ovary species of Tetraplasandra revealed that the superior ovary in T. gymnocarpa is unusual in that it develops within an epigynous ground plan. During the course of development, the ovary changes from inferior to secondarily superior primarily by an upward expansion of the ovary from the insertion point of the perianth and androecium to the ovary apex. The superior ovary of T. gymnocarpa, evident in late ontogeny, is a modified inferior ovary; thus it is not structurally homologous to a truly superior ovary. The adaptive significance of the switch from inferior to superior ovary is reexamined. A recent phylogeny of Tetraplasandra and the biogeography of the extant species provide evidence that the change in ovary position may be associated with a shift in pollination strategy that may have occurred as recently as 2.6 million years ago.
Molecular and cytological examination ofCalopogon(Orchidaceae, Epidendroideae): circumscription, phylogeny, polyploidy, and possible hybrid speciation
Authors: Goldman Douglas H. , Jansen Robert K. , van den Berg Cassio , Leitch Ilia J. , Fay Michael F. , Chase Mark W.
Published: February 2008

The orchid genusCalopogonR.Br. (Orchidaceae), native to eastern North America and the northern Caribbean, currently contains five species and up to three varieties. Using nuclear internal transcribed spacer (ITS) ribosomal DNA sequences, amplified fragment length polymorphisms (AFLPs), chloroplast DNA restriction fragments, and chromosome counts, we present a phylogenetic and taxonomic study of the genus.Calopogon multiflorusandC. pallidusare consistently sister species, but the relationships ofC. barbatus,C. oklahomensis, andC. tuberosusare not as clear. In the ITS analysisC. oklahomensisis sister toC. barbatus, whereas it is sister toC. tuberosusin the plastid restriction fragment analysis. Furthermore, all species were found to have chromosome numbers of 2n= 38 and 40, with the exception of the putatively hybrid‐derivedC. oklahomensiswith 2n= 114 and 120. The hexaploidy of the latter, plus the discrepancy in its position between the ITS and plastid restriction fragment trees, could suggest that it is of hybrid origin. However, the presence of unique morphological and molecular characters might indicate that it is either an ancient hybrid or not of hybrid derivation at all. Finally, using these molecular methods all taxa appear to generally be discrete groups, with the exception ofC. tuberosusvars.latifoliusandtuberosus, the former of which is best combined with the latter.
Complex origins of breadfruit (Artocarpus altilis, Moraceae): implications for human migrations in Oceania
Authors: Zerega Nyree J. C. , Ragone Diane , Motley Timothy J.
Published: February 2008

Breadfruit (Artocarpus altilis, Moraceae), a traditional starch crop in Oceania, has enjoyed legendary status ever since its role in the infamous mutiny aboard the H.M.S. Bounty in 1789, yet its origins remain unclear. Breadfruit's closest relatives are A. camansi and A. mariannensis. DNA fingerprinting data (AFLP, amplified fragment length polymorphisms) from over 200 breadfruit cultivars, 30 A. camansi, and 24 A. mariannensis individuals were used to investigate the relationships among these species. Multivariate analyses and the identification of species‐specific AFLP markers indicate at least two origins of breadfruit. Most Melanesian and Polynesian cultivars appear to have arisen over generations of vegetative propagation and selection from A. camansi. In contrast, most Micronesian breadfruit cultivars appear to be the result of hybridization between A. camansi‐derived breadfruit and A. mariannensis. Because breadfruit depends on humans for dispersal, the data were compared to theories on the human colonization of Oceania. The results agree with the well‐supported theory that humans settled Polynesia via Melanesia. Additionally, a long‐distance migration from eastern Melanesia into Micronesia is supported.
Damped oscillations of the giant reed Arundo donax (Poaceae)
Authors: Speck Olga , Spatz Hanns‐Christof
Published: February 2008

The slender upright culms of the giant reed (Arundo donax L.) are often exposed to dynamic wind loads causing significant swaying. The giant reed has slightly tapered hollow stems (4–6 m high) with flat leaves and an extensive underground rhizomatous system with solid branches bearing adventitious roots. Quantitative analyses of videorecordings prove that A. donax responds to dynamic deflections of the stem with damped harmonic bending oscillations. The logarithmic decrement can be used to calculate the relative damping, as a measure of the plant's capacity to dissipate vibrational energy. Plants with leaves have a significantly higher damping compared to plants without leaves. A comparison of the relative damping of plants with and without leaves shows that this finding is only partly due to aerodynamic resistance of the leaves. Structural damping also contributes considerably to the overall damping of the foliate A. donax stem. By stepwise removal of the underground plant organs the influence of rhizome, roots, and soil on the vibrational behavior was determined. The data indicate that underground plant organs as well as leaf sheaths covering the nodes have no significant influence on damping.
Chromosome numbers, meiotic behavior, and pollen viability of species of Vriesea and Aechmea genera (Bromeliaceae) native to Rio Grande do Sul, Brazil
Authors: Palma‐Silva Clarisse , dos Santos Daniel G. , Kaltchuk‐Santos Eliane , Bodanese‐Zanettini Maria H.
Published: February 2008

Chromosome number, meiotic behavior, and pollen viability were analyzed in 15 species of two genera, Vriesea and Aechmea, native to Rio Grande do Sul, Brazil. This study is the first cytogenetic analysis of these taxa. The chromosome numbers are all n = 25, consistent with the proposed base number of x = 25 for Bromeliaceae. All examined taxa displayed regular bivalent pairing and chromosome segregation at meiosis. Observed meiotic abnormalities include univalents in metaphase I; missing or extra chromosomes and precocious division of centromeres in metaphase II; laggards in telophase I and anaphase II/telophase II. The high pollen viability (>88%) reflects a regular meiosis.
Trade‐offs among anti‐herbivore resistance traits: insights from Gossypieae (Malvaceae)
Authors: Rudgers Jennifer A. , Strauss Sharon Y. , Wendel Jonathan F.
Published: February 2008

Plant defense theories commonly predict negative correlations among anti‐herbivore resistance traits. Although this prediction has been widely accepted, the majority of empirical studies have failed to account for similarities among species due to common ancestry, thus risking pseudoreplication. Wild cotton plants possess traits conferring both direct resistance (toxic leaf glands and trichomes) and indirect resistance (extrafloral nectaries that reward enemies of herbivores). The evidence for negative phenotypic correlations among these resistance traits was examined at two levels: withinGossypium thurberi(wild cotton) and across species in the cotton clade (Gossypieae). A phylogenetic analysis controlled for shared ancestry among species. Across the Gossypieae, a strong negative correlation emerged between the direct resistance traits, leaf gland and trichomes. This correlation may reflect costs of these traits, a negative genetic correlation, or redundancy in their actions against herbivores. In contrast, the direct resistance traits (glands and trichomes) were not correlated with the indirect resistance trait of extrafloral nectar, either within or across species. The robust lack of correlation suggests that these direct and indirect resistance mechanisms evolve independently over evolutionary time scales. This conclusion conflicts with both predictions of plant defense theory and the majority of prior comparisons of direct and indirect resistance traits and may reflect the facultative nature of indirect resistance in Gossypieae.
Addressing the “hardest puzzle in American pomology:” Phylogeny of Prunus sect. Prunocerasus (Rosaceae) based on seven noncoding chloroplast DNA regions
Authors: Shaw Joey , Small Randall L.
Published: February 2008

Prunus subg. Prunus sect. Prunocerasus (Rosaceae) is a North American taxon with 17 commonly recognized taxa. To test the hypothesis of monophyly for the section we sequenced the trnG and rpL16 introns and the trnH‐psbA and trnS‐trnG intergenic spacers for at least two representatives of each of the five subgenera in Prunus. Additionally we sampled heavily among Prunus subg. Prunus sections Prunus and Armeniaca and Prunus subg. Amygdalus because these groups are putatively most closely related to Prunocerasus. Once monophyly of sect. Prunocerasus was shown we added the sequences of trnL and rpS16 introns and the trnL‐trnF spacer in an attempt to increase resolution within the section. The species of sect. Prunocerasus showed an initial split with P. subcordata, the only species from western North America, sister to the rest of the group. The remaining species fell into three primary clades. Within each of the three primary clades there was little phylogenetic resolution. Lastly, we present evidence that P. texana, previously classified in subg. Amygdalus, may be a plum or at least contain a Prunocerasus chloroplast. This is the first phylogenetic hypothesis presented for sect. Prunocerasus, and the clades recovered contrast sharply with previously defined groups based on morphological characters.
Phylogenetic studies ofMammillaria(Cactaceae)—insights from chloroplast sequence variation and hypothesis testing using the parametric bootstrap
Authors: Butterworth Charles A. , Wallace Robert S.
Published: February 2008

The genusMammillariais likely the most species‐rich and morphologically variable genus in the Cactaceae. There is doubt as to whether the genus is monophyletic, and past infrageneric treatments differ regarding generic circumscription. Phylogenetic questions aboutMammillariawere addressed using chloroplast DNA sequence data from therpl16intron and thepsbA‐trnHintergenic spacer for 125 taxa (113Mammillaria, 10Coryphantha,Escobaria,Neolloydia,Pelecyphora,Ortegocactus, and two outgroup taxa fromFerocactusandStenocactus). Parsimony analyses were conducted using various heuristic search strategies. Bayesian analyses were conducted using the F81 and F81 + I + G models of sequence evolution. Tree topologies from the parsimony and Bayesian analyses were largely congruent. Hypothesis testing was undertaken using the parametric bootstrap to test the monophyly of the genus and the taxonomic status ofMammillaria candida. Phylogenies derived from the parsimony and Bayesian analyses indicate thatMammillariais not monophyletic and that the genusMammilloydia(synonymMammillaria) is embedded within a “core” group ofMammillariaspecies. Both these results were corroborated by the parametric bootstrap tests. The entirerpl16intron was deleted from species in theMammillaria crinitagroup.
Salvia (Lamiaceae) is not monophyletic: implications for the systematics, radiation, and ecological specializations of Salvia and tribe Mentheae
Authors: Walker Jay B. , Sytsma Kenneth J. , Treutlein Jens , Wink Michael
Published: February 2008

Salvia, with over 900 species from both the Old and New World, is the largest genus in the Lamiaceae. Unlike most members of the subfamily Nepetoideae to which it belongs, only two stamens are expressed in Salvia. Although the structure of these stamens is remarkably variable across the genus, generally each stamen has an elongate connective and divergent anther thecae, which form a lever mechanism important in pollination. In a preliminary investigation of infrageneric relationships within Salvia, the monophyly of the genus and its relationship to other members of the tribe Mentheae were investigated using the chloroplast DNA regions rbcL and trnL‐F. Significant conclusions drawn from the data include: Salvia is not monophyletic, Rosmarinus and Perovskia together are sister to an Old World clade of Salvia, the section Audibertia is sister to subgenus Calosphace or the monotypic Asian genus Dorystaechas, and the New World members of section Heterosphace are sister to section Salviastrum. Owing to the non‐monophyly of Salvia, relationships at the next clearly monophyletic level, tribe Mentheae, were investigated.