bluuebunny/crossref_metadata_2025 huggingface dataset:
Tribal and intergeneric relationships of Mesechiteae (Apocynoideae, Apocynaceae): evidence from three noncoding plastid DNA regions and morphology
Authors: Simões André O. , Endress Mary E. , van der Niet Timotheüs , Kinoshita Luiza S. , Conti Elena
Published: February 2008

The Neotropical tribe Mesechiteae (Apocynaceae) is currently considered to include nine genera: Allomarkgrafia, Galactophora, Macrosiphonia, Mandevilla, Mesechites, Quiotania, Secondatia, Telosiphonia, and Tintinnabularia. Tribal and intergeneric relationships, however, are in dispute. To test the monophyly of the tribe and evaluate intratribal relationships, a maximum parsimony analysis was conducted based on DNA sequences from the plastid rpl16 intron, rps16 intron, and trnS‐G intergenic spacer region as well as morphological data for 23 taxa of Mesechiteae and 11 taxa from other tribes of Apocynoideae. Mesechiteae, as currently circumscribed, was found to be polyphyletic. Only removal of Secondatia and Galactophora and inclusion of Forsteronia rendered the tribe monophyletic. Thus defined, Mesechiteae forms a strongly supported clade including seven genera in three subclades: the Mesechites subclade (comprising Tintinnabularia, Allomarkgrafia, and Mesechites), the Forsteronia subclade (containing only Forsteronia) and the Mandevilla subclade (comprising Macrosiphonia, Mandevilla, and Telosiphonia). Allomarkgrafia is nested in Mesechites. Macrosiphonia and Telosiphonia form two distinct monophyletic clades. Both, however, are nested in Mandevilla. Results suggest upholding the following genera in Mesechiteae: Allomarkgrafia, Forsteronia, Mandevilla, Mesechites, and Tintinnabularia. The status of Quiotania could not be evaluated.
Bayesian analysis of combined chloroplast loci, using multiple calibrations, supports the recent arrival of Melastomataceae in Africa and Madagascar
Authors: Renner Susanne S.
Published: February 2008

A new biogeographic scenario for Melastomataceae (Morley and Dick, American Journal of Botany 90(11) pp. 1638–1645, 2003) accepts an ndhF‐based phylogeny for the family by Renner et al. (American Journal of Botany 88(7): 1290–1300, 2001), but rejects those authors'divergence time estimates. Morley and Dick concluded that Gondwanan vicariance, rather than the more recent long dispersal proposed by Renner et al. explains the presence of the family in Africa and Madagascar. To assess the strength of this conclusion, a Bayesian analysis was conducted on three times the amount of sequence data used before (ndhF, rbcL, rpl16; 3100 base pairs [bp], excluding all gaps). The Bayesian approach to divergence time estimation does not rely on a strict molecular clock and employs multiple simultaneous minimal or maximal bounds on node ages. Reliance on northern mid‐latitude fossils of Melastomataceae for calibrations was avoided or reduced by using alternative fossil and tectonic calibrations, including all those suggested by Morley and Dick. Results reaffirm the relatively recent spread of melastome lineages among the southern continents and refute the breakup of Gondwana as a plausible explanation for the presence of Dissochaeteae/Sonerileae in Madagascar and Africa and the presence of Melastomeae in Africa and Southeast Asia. Melastomeae appear to have reached Africa around 17–15 million years (my) ago, while Dissochaeteae and Sonerileae apparently reached Madagascar at 17–15 and 20–18 my ago. I also explored the effects of constraining Melastomeae to minimally 76 my old (to have reached Africa by island hopping as postulated by Morley and Dick). This resulted in an estimate for their arrival in Africa of 35 my ago and for Dissochaeteae and Sonerileae in Madagascar of 28 and 33 my ago, still implying long‐distance dispersal. The Bayesian 95% credibility ranges around these dates, however, are large. Regardless of the increasing sophistication of molecular estimates of divergence time, Gondwanan scenarios will remain untestable as long as biases in the fossil record can justifiably be invoked to explain away the absence of fossils.
A comparison of male and female responses to inbreeding in Cucurbita pepo subsp. texana (Cucurbitaceae)
Authors: Hayes C. Nelson , Winsor James A. , Stephenson Andrew G.
Published: February 2008

Accurate estimates of inbreeding depression are necessary in order to predict the evolutionary dynamics of a population, but many studies estimate inbreeding depression based solely on components of female function such as fruit set, seed set, and seed quality. Because total fitness is achieved through both male and female functions in hermaphroditic plants, estimates of both male and female fitness are needed to estimate accurately the magnitude of inbreeding depression. Seedlings of a wild gourd, Cucurbita pepo subsp. texana, with coefficients of inbreeding of 0 and 0.75 were planted in an experimental garden, and several components of male and female fitness were measured over the course of the growing season. Fitness in inbred plants was confounded by both maternal and genetic inbreeding effects. Inbred individuals produced significantly fewer fruits than outcrossed individuals, and percentage germination of seeds from inbred individuals was significantly lower than seeds from outcrossed individuals. Inbred plants also produced significantly fewer staminate flowers and marginally fewer and smaller pollen grains per flower. Pollen from inbred plants also grew significantly more slowly in vitro than pollen from outcrossed plants. Multiplicative estimates of inbreeding depression revealed inbreeding depression for both male and female functions in wild gourd, but inbreeding depression through female function was stronger than inbreeding depression through male function.
Do gymnosperm needles pull water through the xylem produced in the same year as the needle?
Authors: Maton Clarisse , Gartner Barbara L.
Published: February 2008

This research investigated the longevity of functional connections between leaf traces and stem xylem in 16 species of conifers to better understand the spatial use of sapwood for water transport. The first question was which ring(s) stained when a vacuum was applied to the distal end of the cut surface of a needle attached to a short stem segment. The vacuum was applied to either 1‐ or 2‐yr‐old foliage taken from 4–6‐yr‐old saplings. The 16 species were then categorized based on the growth ring that most consistently stained when the vacuum was applied to the 2‐yr‐old needles. There were three distinct stain patterns for the evergreen conifers and one pattern for the deciduous conifers. Three evergreen species could not be categorized. The second question used needle fall data to ask whether the leaf trace appeared to break because of age or stem diameter in 5‐yr‐old Pseudotsuga menziesii saplings. An apparent threshold stem diameter at which needles tended to be shed was more related to diameter than age. These xylem connection patterns could affect leaf cohort physiology and the spatial pattern of water flux in sapwood.
Colonization of volcanic deserts from productive patches
Authors: del Moral Roger , Eckert Andrew J.
Published: February 2008

Dense vegetation can augment landscape biodiversity, promote recovery of surrounding ecosystems, and facilitate colonization. However, dispersal limits affect vegetation structure early in succession to a degree that is not widely appreciated. We studied two contrasting densely vegetated habitats located on Mount St. Helens to explore their effects on surrounding vegetation. We sampled refugia and adjacent barrens and compared them to a study conducted 5 yr earlier. We sampled isolated wetlands and their surroundings. Species richness, total cover, cover of most dispersal types, the information statistic (H′), and the complement of Simpson's Index (D) were negatively correlated with distance from the refugia up to 32 m. Compared to 1997, the 2002 transects had higher cover, and adjacent samples were more similar to one another. Dominance had shifted from wind‐dispersed species to more persistent species with less effective dispersal mechanisms. The pattern of these results demonstrated that refugia were a major, but indirect source of recruitment for many species. The influence of wetlands on surrounding vegetation recovery was even more spatially localized. This study demonstrates that dispersal from surviving and rapidly recovered vegetation has been overemphasized as a mechanism for vegetation recovery. The effects of dense vegetation did not extend beyond 32 m in our studies, and local effects appear to diminish over time.
Mechanisms of selection for drought stress tolerance and avoidance in Impatiens capensis (Balsaminaceae)
Authors: Heschel M. Shane , Riginos Corinna
Published: February 2008

For longer lived annual plants, high water‐use efficiency (WUE) and low stomatal conductance are hypothesized to confer a fitness advantage under drought stress. To directly test the adaptive significance of WUE and stomatal conductance under drought stress, inbred lines of Impatiens capensis were grown in two field environments (watered and not‐watered), in a year of unusual early‐season drought. In contrast to the results from a previous study of late‐season drought in the same system, selection was detected for lower WUE, increased stomatal conductance, and early flowering time. These findings suggest that early‐season drought conditions may select for drought avoidance traits such as low WUE and early reproduction, whereas later drought selects for tolerance traits such as high WUE.
Effects of herbivory and inbreeding on the pollinators and mating system of Mimulus guttatus (Phrymaceae)
Authors: Ivey Christopher T. , Carr David E.
Published: February 2008

Most models of mating system evolution predict mixed mating to be unstable, although it is commonly reported from nature. Ecological interactions with mutualistic pollinators can help account for this discrepancy, but antagonists such as herbivores are also likely to play a role. In addition, inbreeding can alter ecological interactions and directly affect selfing rates, which may also contribute to maintaining mating system variation. We explored herbivore and inbreeding effects on pollinator behavior and selfing rates in Mimulus guttatus. First, individual spittlebug (Philaenus spumarius) herbivores were applied to native plants in two populations. Spittlebugs reduced flower size, increased anther–stigma distance, and increased selfing rates. A second experiment factorially crossed spittlebug treatment with inbreeding history (self‐ vs. cross‐fertilized), using potted plants in arrays. Spittlebugs did not affect pollinator behavior, but they reduced flower size and nearly doubled the selfing rate. Inbreeding reduced the frequency of pollinator visits and increased flower‐handling time, and this may be the first report that inbreeding affects pollinator behavior. Selfing rates of inbred plants were reduced by one half, which may reflect early inbreeding depression or altered pollinator behavior. The contrasting effects of herbivory and inbreeding on selfing rates may help maintain mating system variation in M. guttatus.
(1→3),(1→4)‐ß‐d‐Glucans in the cell walls of the Poales (sensu lato): an immunogold labeling study using a monoclonal antibody
Authors: Trethewey Jason A. K. , Campbell Lisa M. , Harris Philip J.
Published: February 2008

(1→3),(1→4)‐ß‐Glucans had previously been detected in nonlignified cell wall preparations of only the Poaceae and five other families in the graminoid clade of the Poales (s.l.). Cell walls of vegetative organs of 12 species in nine families of the Poales (s.l.) were examined by immunogold labeling using a monoclonal antibody to (1→3),(1→4)‐ß‐glucans. Three types of wall‐labeling patterns were identified depending on the density of labeling of the nonlignified walls of epidermal and parenchyma cells and the lignified walls of sclerenchyma fibers and xylem tracheary elements: type 1 in Poaceae and Flagellariaceae, type 2 in Restionaceae and Xyridaceae, and type 3 in Cyperaceae and Juncaceae. Type 1 had the heaviest labeling of nonlignified walls and type 2 the heaviest labeling of lignified walls. Type 3 had the least wall labeling, with only very light labeling of nonlignified and lignified walls. No labeling was found over walls of Typhaceae, Sparganiaceae, or Bromeliaceae. The results are discussed in relation to Poales phylogeny.
Outbreeding, seedling establishment, and maladaptation in natural and reintroduced populations of rare and common Silene douglasii (Caryophyllaceae)
Authors: Lofflin Diana L. , Kephart Susan R.
Published: February 2008

Reintroductions are increasingly used to enhance declining populations, yet comparative data for critical germination and establishment phases are seldom available for both rare and common herbaceous perennials. After introducing a total of >1800 seeds, we compared experimentally manipulated and natural populations of widespread Silene douglasii var. douglasii relative to rare S. douglasii var. oraria, known in only three coastal headlands. Despite equivalent ex situ germination, oraria field plots produced significantly fewer juveniles than douglasii plots indicating that seedling survival limits plant establishment. We also evaluated transplant vs. seed reintroductions as restoration tools, the effect of inbreeding on fitness, and the potential importance of buried seed pools. Germination declined rapidly for seeds over 1–2 years old, and only 2.2% of newly collected seeds of oraria survived as seedlings. Transplant survival over 5 years was greatest for outbred progeny; furthermore, 75% of the new seedlings emerged near outbred progeny from the original reintroduction. Despite similar ovule numbers and pollinator visitation, transplants exhibited 49–179% maladaptation in the formerly grazed site, with significantly lower fruit and seed set than adults in more diverse natural populations. This study experimentally identifies several key factors affecting plant reintroductions, facilitating effective development of large‐scale reintroduction strategies for native perennials.
Phylogenetic analysis of Pinguicula (Lentibulariaceae): chloroplast DNA sequences and morphology support several geographically distinct radiations
Authors: Cieslak Thomas , Polepalli Jai Santosh , White Adam , Müller Kai , Borsch Thomas , Barthlott Wilhelm , Steiger Juerg , Marchant Adam , Legendre Laurent
Published: February 2008

The genus Pinguicula is one of the three genera of the carnivorous Lentibulariaceae, comprising approximately 80 species. Phylogeny inference using nucleotide sequences of the chloroplast gene matK and the trnK group II intron, as well as a set of 32 morphological characters revealed five well‐supported, major lineages within the genus. These lineages largely reflect radiations in clearly defined geographic regions, whereas most previously recognized sections of the genus are shown to be para‐ or polyphyletic. A species‐rich Mexican‐Central American‐Caribbean clade has the Eurasian P. alpina and an East Asian clade as successive sisters. All three are characterized by a production of flower buds on winter‐resting plants, a specific corolla hair structure and a very large corolla lower central lobe. Another diverse clade is composed of species with primarily European distribution including the widespread type species P. vulgaris. For this clade, vegetative reproduction during dormancy is synapomorphic. Species native to SE North America and the South American Andes and a group of Mediterranean and NE Atlantic coast species together appear in a fifth well‐supported clade, that is characterized by a tropical‐type growth habit. It is the only clade that has reached temperate zones of the southern hemisphere.
Dating phylogenetically basal eudicots usingrbcLsequences and multiple fossil reference points
Authors: Anderson Cajsa Lisa , Bremer Kåre , Friis Else Marie
Published: February 2008

A molecular dating of the phylogenetically basal eudicots (Ranunculales, Proteales, Sabiales, Buxales and Trochodendrales sensu Angiosperm Phylogeny Group II) has been performed using several fossils as minimum age constraints. AllrbcLsequences available in GenBank were sampled for the taxa in focus. Dating was performed using penalized likelihood, and results were compared with nonparametric rate smoothing. Fourteen eudicot fossils, all with a Cretaceous record, were included in this study for age constraints. Nine of these are assigned to basal eudicots and the remaining five taxa represent core eudicots. Our study shows that the choice of methods and fossil constraints has a great impact on the age estimates, and that removing one single fossil change the results in the magnitude of tens of million years. The use of several fossil constraints increase the probability of approaching the true ages. Our results suggest a rapid diversification during the late Early Cretaceous, with all the lineages of basal eudicots emerging during the latest part of the Early Cretaceous. The age of Ranunculales was estimated to 120 my, Proteales to 119 my, Sabiales to 118 my, Buxales to 117 my, and Trochodendrales to 116 my.
Timing of seed dispersal generates a bimodal seed bank depth distribution
Authors: Espinar José L. , Thompson Ken , García Luis V.
Published: February 2008

The density of soil seed banks is normally highest at the soil surface and declines monotonically with depth. Sometimes, for a variety of reasons, peak density occurs below the surface but, except in severely disturbed soils, it is generally true that deeper seeds are older. In seasonally dry habitats that develop deep soil cracks during the dry season, it is possible that some seeds fall down cracks and rapidly become deeply buried. We investigated this possibility for three dominant clonal perennials (Scirpus maritimus, S. litoralis, and Juncus subulatus) in the Doñana salt marsh, a nontidal marsh with a Mediterranean climate located in southwest Spain. Two species, which shed most of their seed during the dry season and have seeds with low buoyancy, had bimodal viable seed depth distributions, with peak densities at the surface and at 16–20 cm. A third species, which shed most seeds after soil cracks had closed and had seeds with high buoyancy, had viable seeds only in surface soil. Bimodal seed bank depth distributions may be relatively common in seasonally dry habitats with fine‐textured soils, but their ecological significance has not been investigated.
Development of woody branch attachments in Schefflera (Araliaceae or Apiaceae)
Authors: Tomlinson P. Barry , Fisher Jack B. , Hallé Francis , Villalobos Randol
Published: February 2008

Attachment of branches in Schefflera is unusual in that it involves fingerlike woody extensions that originate in the cortex and pass gradually into the woody cylinder of the parent shoot. We tested the hypothesis that these structures could be roots since Schefflera is a hemi‐epiphyte with aerial roots. These branch traces originate by secondary development in the many leaf traces (LTs) of the multilacunar node together with associated accessory traces. In the primary condition, the LTs may be described as cortical bundles. Leaves are long persistent and can maintain a primary stem connection across a broad cylinder of secondary xylem. Under the stimulus of branch development, the LTs form a template for secondary vascular development. Because the LT system is broad, with many traces, the branch attachment is also broad. The fingerlike extensions are attached to the surface of the woody cylinder of the parent stem but are progressively obscured as a continuous cambium is formed. Bark tissues are included within the branch axil because of the extended cortical origin of the initial attachment. The results are discussed in the context of branch‐trunk unions in tropical plants, an important component of canopy development.
Differentiation of cellular and biochemical features of the single‐cell C4 syndrome during leaf development in Bienertia cycloptera (Chenopodiaceae)
Authors: Voznesenskaya Elena V. , Koteyeva Nouria K. , Chuong Simon D. X. , Akhani Hossein , Edwards Gerald E. , Franceschi Vincent R.
Published: February 2008

The terrestrial plant Bienertia cycloptera has been shown to accomplish C4 photosynthesis within individual chlorenchyma cells by spatially separating the phases of carbon assimilation into distinct peripheral and central compartments. In this study, anatomical, physiological, and biochemical techniques were used to determine how this unique compartmentation develops. Western blots show ribulose‐1,5‐bisphosphate carboxylase (Rubisco) (chloroplastic) is present in the youngest leaves and increases during development, while levels of C4 enzymes—pyruvate,Pi dikinase (chloroplastic), phosphoenolpyruvate carboxylase (PEPC) (cytosol), and NAD‐malic enzyme (mitochondrial)—increase later in development. Immunolocalization confirmed this for Rubisco and PEPC. The youngest chlorenchyma cells have a central nucleus surrounded by monomorphic granal chloroplasts containing Rubisco. Later stages show progressive development of a central cytoplasmic compartment enriched with chloroplasts and mitochondria and of a peripheral cytoplasm with chloroplasts. A complex reticulum of connections between the compartments also developed and was characterized. δ13C isotope analyses show mature leaves have distinct C4‐type isotope composition, while the composition in younger leaves is “C4‐like.” Based on the results, this form of single‐cell C4 photosynthesis develops from a common pool of organelles through partitioning to separate compartments, and the development of biochemically and ultrastructurally dimorphic chloroplasts.
Growth irradiance effects on photosynthesis and growth in two co‐occurring shade‐tolerant neotropical perennials of contrasting photosynthetic pathways
Authors: Skillman John B. , Garcia Milton , Virgo Aurelio , Winter Klaus
Published: February 2008

Dieffenbachia longispatha (C3) and Aechmea magdalenae (Crassulacean acid metabolism, CAM) are syntopic, neotropical forest perennials in central Panama that are restricted to shaded habitats. This is of particular interest for A. magdalenae because, like other understory CAM bromeliad species, it appears functionally and structurally to be better suited to life in full sun. Growth irradiance (GI) effects on photosynthesis and growth in both species were explored in the context of sun/shade trade‐off concepts largely derived from studies of C3 plants. Potted plants were grown outdoors in 1, 55, and 100% full sun for 5 mo under well‐watered conditions. While both species grew faster in high compared to low light, maximum relative growth rates (RGR) in full sun were still extremely slow with A. magdalenae showing a RGR approximately half that of D. longispatha. Photosynthetic capacity increased with GI in D. longispatha but not in A. magdalenae. Aechmea magdalenae responded to GI with shifts in the activity of the different CAM phases. Both species were photoinhibited in full sun, but more so in A. magdalenae. Despite possessing many traits considered adaptive in high light, these results suggest that A. magdalenae is unlikely to attain sufficient growth rates to thrive in productive, high‐light habitats.
Reproductive developmental complexity in the African oil palm (Elaeis guineensis, Arecaceae)
Authors: Adam Hélène , Jouannic Stefan , Escoute Jacques , Duval Yves , Verdeil Jean‐Luc , Tregear James W.
Published: February 2008

Species of the palm family (Arecaceae) are remarkably diverse in their inflorescence and floral morphologies, which make them a particularly interesting group for studies of reproductive development and its evolution. Using light and scanning electron microscopy, we describe inflorescence and flower development in the African oil palmElaeis guineensisfrom the initiation of the inflorescence meristem to flower maturity. In mature palms, the inflorescence develops over 2–3 years and is characterized by individual stages within which differentiation may be either relatively slow, as in the case of early inflorescence meristem development, or rapid, as in the case of flower organogenesis. The female inflorescence bears floral triads composed of single pistillate flowers flanked by two abortive staminate flowers, whereas the male inflorescence contains single functional staminate flowers. This suggests a possible evolutionary movement from an ancestral hermaphrodite inflorescence form containing fully functional floral triads to the situation of temporal dioecy observed at present. Wild type flowers are compared to those bearing an epigenetic homeotic abnormality, known asmantled,involving an alteration of the identity of the organs in the fertile and sterile androecium.
Inbreeding depression and selfing rate of Ipomoea hederacea var.  integriuscula (Convolvulaceae)
Authors: Hull‐Sanders Helen M. , Eubanks Micky D. , Carr David E.
Published: February 2008

Inbreeding depression and selfing rate were investigated in the self‐compatible vine Ipomoea hederacea to assess the variability of the breeding system. Inbreeding depression differed between populations and the magnitude varied at germination, growth (as measured by aboveground biomass), and reproductive potential. Plants from Macon County, Alabama, USA, had significant inbreeding depression (31%) at germination, but no significant inbreeding depression for aboveground biomass or number of reproductive structures (buds and flowers) at 45 d post germination in the greenhouse or in the field. Plants from Morgan County, Alabama, however, had significant inbreeding depression (>50%) for all three stages in the greenhouse. In allozyme comparisons, five of the 11 I. hederacea populations surveyed had high selfing rates (66.66–92.53%) and high levels of homozygosity (FIS = 0.500–0.861) in 2003, and three of four populations surveyed in 2004 had selfing rates that exceeded 50%. High selfing rates, high levels of homozygosity, and low levels of inbreeding depression suggest that inbreeding depression may not present a significant barrier to the transmission of selfing alleles in some populations of I. hederacea, but does not account for the maintenance of a mixed mating system in other populations.
Reproductive investment in male and female Eurya japonica (Theaceae) at tree and branch levels
Authors: Suzuki Alata Antonio
Published: February 2008

Intersexual differences in reproductive investments (RIs) (dry mass of reproductive tissue) at tree and branch levels in Eurya japonica were examined during two successive years. Mean total RIs per tree for males and females (adjusted for the mean trunk diameter in the combined sample trees, 25.7 mm) were 3.47 and 5.67 g dry mass. Females generally allocated about 1.6 times more biomass per tree to reproduction than males. On the other hand, male total RI per terminal branch averaged 51.6 mg dry mass and female averaged 226.6 mg. Females generally allocated about 4.4 times more biomass per terminal branch to reproduction than males. Thus, the magnitude of sexual difference at the tree level was much lower than that at the branch level. There were negative correlations between interyear fluctuation of total RI and stem diameter for both sexes. Interyear fluctuation of RI was greater for females than males in all size categories. This study revealed that conclusions from tree measures of RI differed from branch measures and suggested the importance of evaluating the average RI at the tree level for woody plants. I discussed the importance in adopting an effective sampling strategy for evaluating the RI at the tree level.
The compensatory responses of an understory herb to experimental damage are habitat‐dependent
Authors: Bruna Emilio M. , Ribeiro Maria Beatriz Nogueira
Published: February 2008

Canopy gap formation strongly influences the diversity and dynamics of both tropical and temperate forests. It is often viewed as inherently beneficial for understory plants, primarily because growth and flowering are enhanced when light is no longer a limiting resource. It can also be detrimental, however, because plants can be damaged by falling crowns or branches. To elucidate the responses of the Amazonian understory herb Heliconia acuminata to damage sustained during gap formation, we transplanted both experimentally damaged and control plants to canopy gaps and the forest understory. We then measured their patterns of growth and biomass allocation 10 mo later. Despite losing approximately 50% of their leaf area, all damaged plants survived the duration of our experiment. Furthermore, damaged plants transplanted to gaps had relative growth rates that far exceeded those of undamaged plants in both gaps and the forest understory. There were also significant interactions between damage and destination habitat type on root to shoot ratios and leaf‐area ratios. Our results suggest the ability of herbaceous plants to recover from damage, as well as patterns of post‐damage biomass allocation, may be habitat‐dependent in ways that have previously remained unexplored.
Development of nonlignified fibers in leaves of Gnetum gnemon (Gnetales)
Authors: Tomlinson P. Barry , Fisher Jack B.
Published: February 2008

Leaves of Gnetum gnemon have an extensive anastomosing network of thick‐walled cellulosic fibers that permeate mesophyll tissues. Brochidodromus venation is precise with major veins originating by uniseriate plate meristems. In mesophyll differentiation, laticifers appear before fibers and more or less parallel to major veins. Fiber initials appear later, mostly within the subhypodermal mesophyll cell layers, but otherwise adjacent to the leaf margin or the major veins. Fibers are early binucleate and sometimes become four‐nucleate. Fiber initials extend by symplastic but mainly intrusive apical growth, become irregular, little branched and interpenetrate other mesophyll layers. They make frequent contact with other fibers forming the anatomosing system, but remain thin‐walled until leaf expansion is complete. Sclereids are little developed, thus fibers become the main mechanical system of the mature leaf. Once expansion is complete, maturation of fibers involves rapid formation of a cellulosic but unlignified secondary wall that is non‐lamellate and almost occludes the cell lumen. These fibers are contrasted with the gelatinous (tension) fibers developed eccentrically in stems of Gnetum. Apart from their mechanical function, fibers may also have a hydraulic function in maintaining a highly hydrated internal leaf atmosphere.
Structural and mechanical peculiarities of the petioles of giant leaves of Amorphophallus (Araceae)
Authors: Hejnowicz Zygmunt , Barthlott Wilhelm
Published: February 2008

Petioles (up to 4 m tall) of huge solitary leaves of mature plants of Amorphophallus titanum and A. gigas resemble tree trunks supporting an umbrella‐like crown. In a mechanical sense, the petiole is a shell, composed of compact parenchyma with embedded collenchyma strands. The core of the shell is filled with aerenchyma. Mechanical stability of the petiole strongly depends upon the turgor pressure in the parenchyma of the shell and the core. The petiole collapses upon senescence when the turgor pressure decreases as a result of increasing osmolality of the solution permeating cell walls. The present study supports the postulate that aerenchyma serves a mechanical function. The petiole can be easily broken by animals during a collision. This risk is proposed to be lowered by the mimicry of the color pattern of the petiole's surface, which resembles a stiff tree trunk covered with lichen thalli (in both species) and with bark in the case of A. gigas. The cellular basis of these color patterns is described.
Correlation but no causation between leaf nitrogen and maximum assimilation: the role of drought and reproduction in gas exchange in an understory tropical plant Miconia ciliata (Melastomataceae)
Authors: Aragão Débora V. , Fortini Lucas B. , Mulkey Stephen S. , Zarin Daniel J. , Araujo Maristela M. , de Carvalho Cláudio J. R.
Published: February 2008

Alternative hypotheses were tested to explain a previously reported anomaly in the response of leaf photosynthetic capacity at light saturation (Amax) in Miconia ciliata to dry‐season irrigation. The anomaly is characterized by an abrupt increase in leaf Amax for nonirrigated plants at the onset of the rainy season to values that significantly exceeded corresponding measurements for plants that were irrigated during the previous dry season. Hypothesis 1 posits that a pulse in leaf nitrogen increases CO2 assimilation in nonirrigated plants at the onset of the wet season and is dampened for irrigated plants; this hypothesis was rejected because, although a wet‐season nitrogen pulse did occur, it was identical for both irrigated and nonirrigated plants and was preceded by the increase in assimilation by nonirrigated plants. Hypothesis 2 posits that a reproduction‐related, compensatory photosynthetic response occurs in nonirrigated plants following the onset of the wet season and is dampened in irrigated plants; consistent with hypothesis 2, high maximum assimilation rates for control plants in the wet season were significantly correlated with fruiting and flowering, whereas irrigation caused flowering and fruiting in the dry season, spreading M. ciliata reproductive activity in irrigated plants across the entire year.
Evolutionary increase in sexual and clonal reproductive capacity during biological invasion in an aquatic plant Butomus umbellatus (Butomaceae)
Authors: Brown Jeremy S. , Eckert Christopher G.
Published: February 2008

To test the hypothesis that increased allocation to reproduction is selected during biological invasion, we compared germination, survival, growth, and reproduction of native vs. introduced populations of the invasive aquatic plant Butomus umbellatus in a common greenhouse environment. Although seedling emergence and establishment did not differ consistently, survival thereafter was twice as high for eight introduced North American than eight native European populations. As predicted, introduced plants were more likely to produce sexual inflorescences and clonal asexual vegetative bulbils, and they invested much more biomass in both reproductive modes. Higher reproductive investment was due to higher proportional allocation of biomass rather than larger plant size. These results are consistent with selection for increased reproduction during range expansion. However, population genetic surveys indicate that recruitment from seed rarely occurs in introduced populations. Hence increased sexual allocation is not an adaptive response to invasion. Although increased clonal reproduction may be advantageous in expanding populations, genetic evidence from introduced populations of B. umbellatus suggests that increased clonal allocation may have arisen via stochastic processes during long‐distance transport or a selective filter right at introduction, rather than incremental natural selection during range expansion.
Predicting mating patterns from pollination syndromes: the case of “sapromyiophily” in Tacca chantrieri (Taccaceae)
Authors: Zhang Ling , Barrett Spencer C. H. , Gao Jiang‐Yun , Chen Jin , Cole W. W. , Liu Yong , Bai Zhi‐Lin , Li Qing‐Jun
Published: February 2008

Tacca, a genus of tropical herbs, possesses near black flowers, conspicuous involucral bracts and whisker‐like filiform bracteoles. These features have been assumed to function as a “deceit syndrome” in which reproductive structures resemble decaying organic material attracting flies that facilitate cross‐pollination (sapromyiophily). We investigated pollination and mating in Tacca chantrieri populations from SW China to evaluate this assumption. Contrary to this expectation, populations were highly selfing. Pollinator visitation was infrequent and bagged flowers set abundant seed. Pollen loads on stigmas indicated autonomous self‐pollination, some of which occurred prior to flower opening. The seed set of inflorescences with bracts and bracteoles removed was not significantly different from unmanipulated inflorescences, suggesting that these structures play a limited role in pollinator attraction, at least at our study sites. Pollen : ovule ratios averaged 49, a value expected in a highly selfing species. Selfing rates estimated in four populations using allozyme markers averaged 0.86 (range 0.76–0.94), thus corroborating this inference. Our results indicate that despite considerable investment in extravagant display, populations of T. chantrieri are highly selfing. We propose several hypotheses to resolve this paradox and argue that future studies of pollination syndromes would benefit by investigation of both pollination and mating biology.
Aglaia (Meliaceae): an evaluation of taxonomic concepts based on DNA data and secondary metabolites
Authors: Muellner Alexandra N. , Samuel Rosabelle , Chase Mark W. , Pannell Caroline M. , Greger Harald
Published: February 2008

We performed maximum parsimony and Bayesian analyses (nuclear ITS rDNA, plastid rps16 intron) to estimate phylogenetic relationships within Aglaia (over 100 species in Southeast Asia, the Pacific, and Australia) and its relations among Aglaieae (Meliaceae). Based on 67 accessions of Aglaieae, three taxa of Guareae, and two taxa of Melieae (outgroup), this study provides the first assessment of the current circumscription of Aglaieae, Aglaia, and its sections and to a more limited extent of species concepts in Aglaia. DNA data are compared to recently collected data on chemical profiles. Our analyses indicate (1) the monophyly of Aglaieae; (2) the polyphyly of Aphanamixis; (3) the paraphyly of Aglaia; (4) the existence of at least three entities with respect to Aglaia: (a) the core group of Aglaia section Amoora (dehiscent fruits) with close relationships to Lansium and Reinwardtiodendron, (b) a group comprising morphological intermediates between the two sections, and (c) the core group of Aglaia section Aglaia (indehiscent fruits). Macro‐ and micromolecular data indicate that complex species are more heterogeneous, i.e., probably containing more than one taxon each, than taxonomically isolated species. A third section in Aglaia is recognized to accommodate A. lawii, A. teysmanniana, and A. beccarii.
Polyphyly ofMussaendainferred from ITS and trnT‐F data and its implication for generic limits in Mussaendeae (Rubiaceae)
Authors: Alejandro Grecebio D. , Razafimandimbison Sylvain G. , Liede‐Schumann Sigrid
Published: February 2008

Although recognition ofMussaendaas a separate genus has been widely accepted, its generic circumscriptions have always been controversial. In this first molecular phylogenetic study focused specifically onMussaendasensu lato (s.l.) and its allied genera, parsimony analyses were based on both ITS andtrnT‐Fsequence data to (1) test the monophyly ofMussaendas.l. as presently circumscribed, (2) assess the phylogenetic relationships within the tribe Mussaendeae as currently delimited, (3) evaluate the phylogenetic value of the morphological characters traditionally and/or currently used to circumscribe Mussaendeae, (4) and make inferences on the biogeographical origin ofMussaenda. Of the 63trnT‐Fand 38 ITS sequences included in our studies, 52 and 36 sequences, respectively, are newly published here. Our results highly support the polyphyly ofMussaendas.l. as currently delimited but further support the monophyly of Mussaendeae sensu Bremer and Thulin. The MalagasyMussaendaare more closely related toLandiopsisthan they are to the African and AsianMussaenda.Pseudomussaendaand the Afro‐AsianMussaendaclade are resolved as sister groups.Aphaenandrais nested within the Afro‐AsianMussaendaclade. As a result, we mergeAphaenandrainMussaenda, which is now restricted to include only the African and AsianMussaendarepresentatives. We describe a new genusBremeriato accommodate all Indian Ocean (Madagascar and the Mascarenes)Mussaendaspecies and make 19 new combinations. The newly delimitedMussaendais diagnosed by reduplicate‐valvate aestivation and glabrous styles, whereasBremeriacan be distinguished from the remaining Mussaendeae genera by having both reduplicate‐ and induplicate‐valvate aestivation and densely pubescent styles. Our studies strongly suggest an African origin of the newly delimitedMussaenda. Finally, descriptions of the newly circumscribedMussaendaandBremeriaare provided.
Phylogenetic relationships within the tribe Malveae (Malvaceae, subfamily Malvoideae) as inferred from ITS sequence data
Authors: Tate Jennifer A. , Fuertes Aguilar Javier , Wagstaff Steven J. , La Duke John C. , Bodo Slotta Tracey A. , Simpson Beryl B.
Published: February 2008

Phylogenetic relationships among genera of tribe Malveae (Malvaceae, subfamily Malvoideae) were reconstructed using sequences of the internal transcribed spacer (ITS) region of the 18S–26S nuclear ribosomal repeat. Newly generated sequences were combined with those available from previous generic level studies to assess the current circumscription of the tribe, monophyly of some of the larger genera, and character evolution within the tribe. The ITS data do not support monophyly of most generic alliances as presently defined, nor do the data support monophyly of several Malveae genera. Two main well‐supported clades were recovered, which correspond primarily to taxa that either possess or lack involucral bracts, respectively. Chromosomal evolution has been dynamic in the tribe with haploid numbers varying from n = 5 to 36. Aneuploid reduction, hybridization, and/or polyploidization have been important evolutionary processes in this group.
Extinction threat in the Pedilanthus clade (Euphorbia, Euphorbiaceae), with special reference to the recently rediscovered E. conzattii (P. pulchellus)
Authors: Olson Mark E. , Lomelí S José A. , Cacho N. Ivalú
Published: February 2008

The type locality of the slipper spurge Euphorbia conzattii has been in doubt because the 1917 type is a mixed collection with vague label data. In recent field work, the species was found on Cerro Espino, Pochutla District, Oaxaca, Mexico. We used the Method for Evaluation of Risk of Extinction for Mexican Wild Species (MER), required to protect a species under Mexican law, to assess the conservation status of E. conzattii and found it to be endangered. We discuss the mixture in the type of this species with E. calcarata and present an updated description and an illustration of E. conzattii. Preliminary MER assessments of the other Mexican Pedilanthus clade species show two species to be extinct (E. cyri, E. dressleri) and four threatened (including E. colligata, E. finkii, E. tehuacana). The remaining eight have more favorable outlooks. We comment on MER robustness and aspects vulnerable to confusion and offer clarifications. Extinction risk is not distributed evenly throughout the clade, with a subclade of leafy treelets from a variety of habitats having the greatest number of endangered species. Extinction risk is distributed across all Pedilanthus‐clade habitats; the strongest association noted is that both species from moist highlands are endangered.
Stomatal frequency responses in hardwood‐swamp vegetation from Florida during a 60‐year continuous CO2 increase
Authors: Wagner Friederike , Dilcher David L. , Visscher Henk
Published: February 2008

In a stomatal frequency analysis of leaf remains of Quercus nigra, Acer rubrum, Myrica cerifera, Ilex cassine, and Osmunda regalis that were preserved in precisely dated peat deposits of north‐central Florida, the stomatal index decreased as a response to an atmospheric CO2 increase from 310 ppmv to 370 ppmv over the past 60 years. The observations indicate that CO2 responsiveness may occur in different canopy levels of hardwood‐swamp vegetation. Apart from common woody plants, long‐lived ferns of the undergrowth appear to be affected by CO2 changes. Response rates are most pronounced in M. cerifera, I. cassine, and O. regalis. The potential of these species for quantifying past atmospheric CO2 levels is assessed by a combined analysis of the well‐dated buried leaf record and herbarium material collected during the past century. Leaf remains of the widely occurring species M. cerifera and I. cassine are concluded to be highly suitable for CO2 reconstructions, by which the application range of the stomatal frequency proxy is extended into the warm‐temperate to subtropical realm of North America.
Does cladode inclination restrict microhabitat distribution for Opuntia puberula (Cactaceae)?
Authors: Sortibrán Lugui , Tinoco‐Ojanguren Clara , Terrazas Teresa , Valiente‐Banuet Alfonso
Published: February 2008

In contrast with other Opuntia species, most of the cladodes of Opuntia puberula have a horizontal position. This study explores whether the horizontal cladodes are an adaptive trait to increase light interception in the understory or are a neutral trait, and if this characteristic may prevent its distribution in full sun habitats. Cladode inclination angle and its effect on light interception, cladode temperature, and carbon gain are characterized, and anatomical and physiological traits of upper and lower cladode surfaces are described. Inclination angle was under 50° for 95% of the cladodes, and the frequency of low inclination angles increases as light availability decreases. Nocturnal acid accumulation increased with total daily PPFD intercepted, but no significant differences were detected between typical horizontal cladodes and the few vertical cladodes. Chlorophyll content differed in the upper and lower surfaces of horizontal cladodes; however, chlorenchyma thickness, stomatal conductance, and nocturnal acid accumulation were similar between surfaces. The horizontal position of O. puberula cladodes, which is anatomically determined, restricts it to shaded habitats, where the plants do not overheat, but seems to have no effect on carbon gain.
Floral phenology and compatibility of sawgrass, Cladium jamaicense (Cyperaceae)
Authors: Snyder Jenise M. , Richards Jennifer H.
Published: February 2008

Sawgrass, Cladium jamaicense, is the dominant macrophyte in the Florida Everglades. We examined sawgrass flowering phenology and compatibility reactions in ex situ and in situ populations over 2 yr. Sawgrass flowers in May in southern Florida. Flower maturation was relatively synchronous within an inflorescence. Along the entire inflorescence, functionally male flowers emerged initially, followed by stigmas, then anthers of hermaphroditic flowers. Flowers of each sex expanded over 2 d with less than 1 d in between, totaling 6– 7 d for an inflorescence to complete flowering. Hand pollinations showed that sawgrass was self‐compatible and not pollen‐limited, because open pollinations produced fruit set similar to self‐ and cross‐pollinations. Fruit set was low in autogamy and manipulation treatments. Manipulation treatments were used to study the effect of exposure to airborne pollen during hand pollinations. This treatment thus provides a useful technique for studies on the in situ compatibility of wind‐pollinated graminoids. Sawgrass was able to self‐fertilize, but the timing of flower maturation on an inflorescence promoted outcrossing. Actual outcrossing rates in sawgrass thus depend on clonal architecture and the timing of floral maturation on other inflorescences within a clone rather than on inflorescences of other genets in a population.