bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolution of self‐fertilization at geographical range margins? A comparison of demographic, floral, and mating system variables in central vs. peripheral populations ofAquilegia canadensis(Ranunculaceae)
Authors: Herlihy Christopher R. , Eckert Christopher G.
Published: February 2008

Biogeographic models predict that geographically peripheral populations should be smaller, more sparsely distributed, and have a lower per‐capita reproductive rate than populations near the center of a species'range. Plants in peripheral populations may, therefore, receive less pollinator visitation and outcross pollination, which may select for self‐fertilization to provide reproductive assurance. We tested these predictions by comparing population size, plant density, seed production, floral traits, and mating system parameters between 10 populations ofAquilegia canadensisnear the northern margin of the range with 10 near the range center. Contrary to predictions, peripheral populations were not smaller, less dense, nor less productive than central populations. Nevertheless, we detected substantial regional differences in key floral traits. Plants in central populations produced larger flowers with 68% greater herkogamy and had 30% more flowers open simultaneously than plants in northern populations. However, there was no regional difference in the mating system. In northern populations, 73% (range = 60–88%) of seeds were self‐fertilized compared to 76% (51–100%) in central populations. In both regions, adult inbreeding coefficients were near zero, indicating very strong inbreeding depression despite high selfing. Marked geographic variation in key floral traits does not reflect evolutionary differentiation in the mating system.
Floral developmental evidence for the systematic position of Batis (Bataceae)
Authors: Ronse De Craene Louis P.
Published: February 2008

Molecular phylogenies have associated Bataceae with Salvadoraceae and Koeberliniaceae in an expanded Brassicales. Despite a long taxonomic history, the knowledge of the flower of Batis is still fragmentary. The floral development of pistillate and staminate inflorescences of Batis maritima was investigated to understand homologies of floral structures and to discuss the phylogenetic position of Bataceae within the Brassicales. There has been considerable controversy in the past about the male flower, especially on the nature of the petals and the tubular structure enclosing the flower. Developmental evidence confirms that the male flower is built on a basic tetramerous bauplan and that the tubular structure is derived from four congenitally fused sepal lobes with the three anterior lobes highly reduced. The development of petals and stamens is unidirectional, and the androecium initiates the median stamens before the lateral stamens, suggesting the existence of two whorls. The pistillate flowers are reduced to the bare minimum with two transversal carpels enclosed by a bract. Partial inflorescences function as a swollen dispersal unit. The vestigial stipules probably represent colleters and are not homologous with true stipules. Several characters of Batis are reminiscent of the Brassicaceae, although a link with Salvadoraceae and Koeberliniaceae cannot be excluded.
Solar radiation as a factor in the evolution of scleromorphic leaf anatomy in Proteaceae
Authors: Jordan Gregory J. , Dillon Rebecca A. , Weston Peter H.
Published: February 2008

Species of the major Southern Hemisphere family, Proteaceae, have many scleromorphic anatomical structures in their leaves. Many of these structures (very thick cuticles and five anatomically distinct structures beneath the epidermis) are associated with the leaf surface exposed to direct light. These structures increase the path through which solar radiation must pass before reaching the mesophyll. In this study, such structures are proposed to protect the mesophyll from excess solar radiation, including photosynthetically active, ultraviolet, and possibly infrared radiation. Scleromorphic structures of the upper leaf surface and nonscleromorphic photoprotective structures (dense trichomes and papillae of the upper surface) occur almost exclusively in open vegetation. Open vegetation species of Proteaceae occur in oligotrophic and/or cold and/or dry places, where protection from light in excess of photosynthetic capacity and damage from ultraviolet light should be most important. Data from 123 species and a supertree constructed from available molecular phylogenies are used to show that the proposed photoprotective structures evolved many times within Proteaceae. In tests of correlated evolution, the proposed photoprotective structures are significantly associated with open vegetation, but not with dry habitats.
Floral venation patterns in Siphocampylus (Campanulaceae)
Authors: Saburi Wlademir , Reato Lucelaine Rocha , de Godoy Silvana Aparecida Pires
Published: February 2008

Siphocampylus is a neotropical genus that comprises 221 species distributed from Costa Rica to Argentina and in the Greater Antilles. Twenty‐eight species have been reported from Brazil, mainly occupying mountainous terrain. The floral venation patterns and the origin of the hypanthium in eight Brazilian species, including three varieties, are described. Eleven ovarian vascular bundles depart from the siphonostele or receptacular stele: five of these bundles result from sepalar and staminal adnation and are alternate to five petalar bundles; the remaining bundle is central carpellary. The staminal bundles diverge from the sepalar bundles at the sinus, while the carpellary bundles form a cross, resulting in four ventral bundles; two of these feed the ovules; the other two feed the style. Apparently, the dorsal carpellary bundles diverge at the same site and then ramify profusely. The venation pattern observed is unprecedented in Siphocampylus and is quite different from other reports on genera of Campanulaceae. Further, these findings suggest that the origin of the hypanthium is appendicular, increasing knowledge of venation in this group, thus providing data for phylogenetic considerations.
Effects of crossing distance on offspring fitness and developmental stability inDalechampia scandens(Euphorbiaceae)
Authors: Pélabon Christophe , Carlson Matthew L. , Hansen Thomas F. , Armbruster W. Scott
Published: February 2008

Crosses between genetically close and distant populations ofDalechampia scandens(Euphorbiaceae) were made to test whether the responses of various fitness components and measurements of developmental stability were affected by the outcrossing distance (level of outbreeding). Two fecundity traits, seed set and seed mass, decreased consistently with increasing level of outbreeding, and hybrids between the most divergent populations were sterile. Effects of the genetic distance between parental populations on viability traits, survival and vigor at 1 month of age, were highly idiosyncratic. Hybrids of one long‐distance combination had no reduction in survival and vigor, while both traits were greatly reduced in the other long‐distance combination. The expression of outbreeding depression on fecundity traits differed between reciprocal crosses in some hybrids but not others; thus, hybrid breakdown may have been due to cytoplasmic‐by‐nuclear gene interactions, reduced endosperm formation, or an interaction between progeny and maternal genotype. None of the measures of developmental stability had a consistent relationship with either genetic distance between parental populations or seedling vigor. These results suggest that fecundity and viability traits may be differentially affected by hybridization, probably due to differences in genetic architecture among populations. This study also confirms that developmental stability, as measured by the level of fluctuating asymmetry, is not a reliable index of genetic stress.
The response of plasma membrane lipid composition in callus of the halophyte Spartina patens (Poaceae) to salinity stress
Authors: Wu Jinglan , Seliskar Denise M. , Gallagher John L.
Published: February 2008

Callus cultures of the salt marsh grass Spartina patens were examined to determine changes and consistencies in membrane lipid composition in response to salt. Major membrane lipid classes remained stable at all salinity levels (0, 170, 340 mmol/L). However, the membrane protein to lipid ratio decreased significantly in response to elevated NaCl. Callus plasma membrane (PM) consisted predominantly of sterols, about 60% (mol%) of the total lipids. Glycolipid was the second largest lipid class, making up about 20% (mol%) of the total. With increasing salinity, the relative percentage of sitosterol decreased, while that of campesterol increased. The phospholipid species detected were phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylserine (PS), and phosphatidylinositol (PI). When callus was grown at 340 mmol/L NaCl, PC increased significantly. PI and PS were also significantly elevated in salinity treatments. Only 24–32% of the PM fatty acids were common plant membrane fatty acids, C16, C18, C20, and C22, while over 60% were the less common fatty acids, C11 and C14. Membrane fluidity remained stable in response to growth medium salinity. The findings on membrane responses to salinity will facilitate a better understanding of this halophyte's tactics for salt tolerance.
Linking frugivores to the dynamics of a fruit color polymorphism
Authors: Whitney Kenneth D.
Published: February 2008

Although fruit color polymorphisms are a widespread phenomenon, the role of frugivores in their maintenance is unknown. Selection would require that frugivores interact differentially with fruit color morphs to alter their relative fitnesses, but such a pattern has yet to be demonstrated. In a 3‐yr field study, the interactions of ants and birds with Acacia ligulata, an Australian shrub with a red/yellow/ orange aril color polymorphism, were examined. Bird species fell into three feeding guilds: seed dispersers, seed predators, and aril thieves; ant species acted either as seed dispersers or aril thieves. While there was no evidence of morph bias in ants, in some years birds fed more frequently on the yellow and orange morphs. Based on patterns of seedling survival and juvenile recruitment in seed deposition sites, bird seed dispersers increased the fitness of yellow and orange morphs (relative to red) in some populations, but decreased their relative fitness in others. Bird seed predators uniformly reduced relative fitness of yellow and orange morphs, while bird aril thieves had unknown effects. Altogether, consumer biases produced spatiotemporal variability in the relative fitness of A. ligulata color morphs, a pattern qualitatively consistent with maintenance of the polymorphism.
Patterns of multiple paternity in fruits of Mimulus ringens (Phrymaceae)
Authors: Mitchell Randall J. , Karron Jeffrey D. , Holmquist Karsten G. , Bell John M.
Published: February 2008

Multiply sired fruits provide unambiguous evidence that pollen from two or more donors was deposited on a stigma and successfully fertilized ovules. Such multiple paternity within fruits can have important consequences for both parental and offspring fitness, but little is known about the frequency of multiple paternity or the mechanisms causing it. In this study we quantify the extent of multiple paternity in replicate experimental arrays of Mimulus ringens (square‐stem monkeyflower) and use observations of pollinator behavior to infer mechanisms generating multiply sired fruits. In each array, floral displays were trimmed to two, four, eight, or 16 flowers per plant to span the range of display sizes observed in nature. In our sample of 204 fruits, more than 95% had two or more outcross pollen donors. The number of sires per fruit averaged 4.63 ± 0.10 (mean ± 1 SE), including selfs, and did not vary significantly with floral display treatment. Patterns of bumble bee foraging, combined with limited pollen carryover, suggest that observed levels of multiple paternity cannot be fully explained by single probes that deposited mixed pollen loads. Multiple probes to flowers, each delivering pollen from 1–3 different sires, are more likely to have caused the observed patterns. These sequential visits may reduce the potential for pollen competition and female choice based on pollen tube growth rate.
Leave it to the leaves: a molecular phylogenetic study of Malaxideae (Epidendroideae, Orchidaceae)
Authors: Cameron Kenneth M.
Published: February 2008

Nuclear ITS and plastid matK sequences were collected for 71 taxa of Malaxideae (Orchidaceae). Resulting cladograms are highly resolved and well supported by jackknife analyses. These indicate that the traditional classification system of the tribe using characters primarily related to floral morphology does not reflect the evolutionary history of these taxa. Rather, the tribe is split into two major clades: one of terrestrial species and another of epiphytes. Within the epiphytic clade, taxa with laterally compressed leaves (Oberonia) are monophyletic, whereas the remaining taxa (Liparis pro parte) have elongate conduplicate leaves and form a paraphyletic grade of at least two additional monophyletic lineages. Within the terrestrial clade, taxa with plicate leaves (Liparis p.p. and Malaxis p.p.) clearly separate from taxa with conduplicate leaves (Liparis p.p. and Malaxis p.p.). Although further taxon sampling should take place before nomenclature is changed, it seems evident that Malaxideae will need to be divided into at least seven genera. Furthermore, the transition from epiphytic to terrestrial habit is documented to have occurred only once in Malaxideae, and the value of vegetative over reproductive features in classifying some groups of orchids is again demonstrated.
A comparison of the sexual systems in the trees from the Australian tropics with other tropical biomes—more monoecy but why?
Authors: Gross C. L.
Published: February 2008

Rainforests in tropical Australia occupy a very small, discontinuous area (<1% of the continent), yet they are floristically diverse (c. 2800 vascular species) with high endemicity. There is a distinctive Gondwanan and autochthonous element, and some of the world's ancestral links to the basal angiosperms are uniquely found here. The rainforests can be evergreen or deciduous, but there is a distinct dry season with intermittent drought years. With these characters, the evolutionary pressures on species may be very different to that experienced elsewhere. Sexual systems of 1113 tree species (83 families) from northern Australia were compared with published accounts from the paleo‐ and neotropics. Hermaphroditic systems dominated all tree floras, and within all floras but Australia dioecy was the most common unisexual system. In tropical Australia, however, significantly more monoecy than dioecy occurred at landscape and community levels. Incorporating phylogeny revealed that sex and fruit types are significantly clustered. The Euphorbiaceae and Sapindaceae contributed c. 50% of the monoecious taxa. Inefficient pollinators (e.g., beetles) may have favored the maintenance of monoecy at the expense of dioecy in the Australian tropics although <1% of the flora has been studied for pollinators and none of the monoecious tree species.
Phenotypic plasticity, parental effects, and parental care in plants? I. An examination of spike reflectance inPlantago lanceolata(Plantaginaceae)
Authors: Lacey Elizabeth P. , Herr David
Published: February 2008

We explore the relationships among phenotypic plasticity, parental effects, and parental care in plants by presenting data from four experiments examining reflectance/color patterns inPlantago lanceolata. In three experiments, we measured spike (inflorescence) reflectance between 362 and 850 nm using a spectrophotometer with an integrating sphere. Experiments show that (1) spike reflectance changes seasonally within and outside the visible portion of the spectrum of radiant energy, (2) increasing ambient temperature causes an individual plant to produce flowering and fruiting spikes that reflect more/lighten in color (the greatest changes occur in the regions around 550 nm and between 750 and 850 nm, the visible and near‐infrared regions, respectively), (3) responses are reversible, (4) genotypes within populations and populations from different latitudes differ in mean reflectance and degree of phenotypic plasticity. In a fourth experiment, we measured internal spike temperature. Darker spikes, those produced at lower temperature, got hotter than did lighter spikes in full sun. Thus, plants can partially thermoregulate reproduction and the embryonic development of their offspring. In light of a previous experiment, data suggest that thermoregulation produces adaptive parental effects and is a mechanism by whichP. lanceolataprovides parental care.
Relationships within balsaminoid Ericales: a wood anatomical approach
Authors: Lens Frederic , Dressler Stefan , Jansen Steven , van Evelghem Liesbeth , Smets Erik
Published: February 2008

Wood samples of 49 specimens representing 31 species and 11 genera of woody balsaminoids, i.e., Balsaminaceae, Marcgraviaceae, Pellicieraceae, and Tetrameristaceae, were investigated using light microscopy and scanning electron microscopy. The wood structure of Marcgraviaceae, Pellicieraceae, and Tetrameristaceae is characterized by radial vessel multiples with simple perforation plates, alternate vessel pitting, apotracheal and paratracheal parenchyma, septate libriform fibers, and the presence of raphides in ray cells. Tetrameristaceae and Pellicieraceae are found to be closely related based on the occurrence of unilaterally compound vessel‐ray pitting and multiseriate rays with long uniseriate ends. The narrow rays in Pelliciera are characteristic of this genus, but a broader concept of Tetrameristaceae including Pelliciera is favored. Within Marcgraviaceae, wide rays (more than five‐seriate) are typical of the genus Marcgravia. Furthermore, there is evidence that the impact of altitude and habit plays an important role in the wood structure of this family. The wood structure of Balsaminaceae cannot be compared systematically with other balsaminoids because of their secondary woodiness. Balsaminaceae wood strongly differs due to the presence of exclusively upright ray cells in Impatiens niamniamensis, the absence of rays in Impatiens arguta, and the occurrence of several additional paedomorphic features in both species.
Inter‐ and intraspecific structural variations among intervascular pit membranes, as revealed by field‐emission scanning electron microscopy
Authors: Sano Yuzou
Published: February 2008

The structure of the intervascular pit membranes of four dicotyledonous species (Salix sachalinensis, Betula platyphylla var. japonica, Acer mono, and Fraxinus mandshurica var. japonica) was examined by field‐emission scanning electron microscopy. The intervascular pit membranes of F. mandshurica var. japonica had thin surface layers and a dense middle layer, while no similar middle layer was detectable in the other three species. In F. mandshurica var. japonica, the entire area of each pit membrane was densely covered with microfibrils. In the other three species, by contrast, openings were found in the pit membranes. In some of the intervascular pit membranes of S. sachalinensis, B. platyphylla var. japonica, and A. mono, microfibrils were sparsely interwoven in small areas of the pit membranes and openings of up to several hundred nanometers in diameter were present in such regions. These porous regions tended to be located in peripheral areas of pit membranes. In S. sachalinensis and B. platyphylla var. japonica, ethanol‐soluble extracts, whose chemical nature and function remain unknown, were heavily distributed over the intervascular pit membranes. Our observations suggest that the structure of intervascular pit membranes is more complicated than has previously been acknowledged.
Pollen movement in a natural population of Arisaema serratum (Araceae), a plant with a pitfall‐trap flower pollination system
Authors: Nishizawa Toru , Watano Yasuyuki , Kinoshita Eiichiro , Kawahara Takayuki , Ueda Kunihiko
Published: February 2008

Arisaema serratum possesses a pitfall‐trap flower pollination system. However, little is known about the efficiency and pattern of pollen movement in A. serratum. Thus, the aims of this study are to (1) determine the paternal parents of the seeds and (2) elucidate pollen movement in a natural population. Paternity analysis using microsatellite markers was performed. Seeds were collected from a natural population of A. serratum in 2001 at Horigane, Japan. Small midges became trapped in female spathe tubes during the flowering period. We found that (1) seeds in a fruit were fertilized by multiple sires; (2) seeds sired by a paternal parent were either clumped, exclusively, or randomly distributed on the spadix, depending on the parent; (3) to a great extent, a few males contributed as sires; (4) distance from a female was not a factor in the inequality of reproductive success among males; (5) male reproductive success was not correlated with its size. We conclude that pollen carryover and the trap‐flower pollination system are likely to result in multiple paternity and inequality in male success.
New insights into Paleozoic charophyte morphology and phylogeny
Authors: Feist Monique , Liu Junying , Tafforeau Paul
Published: February 2008

Examination of Paleozoic charophyte fructifications using microscopy and high‐resolution x‐ray synchrotron microtomography has revealed that most of them have a utricle that forms a supplementary calcified cover around the gyrogonite. All Paleozoic families with utricles have been assigned to the Sycidiales. We consider the Moellerinaceae to occupy a central position in the phylogeny of the Charophyta. From these, one group of descendants constitutes the gyrogonites inside the utricles of the Sycidiales; a second descendant goup is thought to be the utricle‐free ancestors of the Charales prior to inversion of spiralization and reduction in cell number. The Sycidiales have a multilayered wall and an internal vesicle, but their families are distinguished by diversity in orientation of external cells, complexity of the utricle wall, and in presence or absence of antheridia. The solidly packed structure of the utricle is believed to be an organ protecting the zygote against dessication. We interpret the morphological similarities between Paleozoic Sycidiales and Mesozoic Clavatoraceae, both with a utricle, as homoplasous rather than expressing a true phylogenetic relationship. We confirm that some umbellids might correspond to utricles of charophytes.
Basal cactus phylogeny: implications of Pereskia (Cactaceae) paraphyly for the transition to the cactus life form
Authors: Edwards Erika J. , Nyffeler Reto , Donoghue Michael J.
Published: February 2008

The cacti are well‐known desert plants, widely recognized by their specialized growth form and essentially leafless condition. Pereskia, a group of 17 species with regular leaf development and function, is generally viewed as representing the “ancestral cactus,” although its placement within Cactaceae has remained uncertain. Here we present a new hypothesis of phylogenetic relationships at the base of the Cactaceae, inferred from DNA sequence data from five gene regions representing all three plant genomes. Our data support a basal split in Cactaceae between a clade of eight Pereskia species, centered around the Caribbean basin, and all other cacti. Two other Pereskia clades, distributed mostly in the southern half of South America, are part of a major clade comprising Maihuenia plus Cactoideae, and Opuntioideae. This result highlights several events in the early evolution of the cacti. First, during the transition to stem‐based photosynthesis, the evolution of stem stomata and delayed bark formation preceded the evolution of the stem cortex into a specialized photosynthetic tissue system. Second, the basal split in cacti separates a northern from an initially southern cactus clade, and the major cactus lineages probably originated in southern or west‐central South America.
Molecular phylogenetics of Limonium and related genera (Plumbaginaceae): biogeographical and systematic implications
Authors: Lledó M. Dolores , Crespo Manuel B. , Fay Michael F. , Chase Mark W.
Published: February 2008

Phylogenetic relationships within Limonium (Plumbaginaceae) are evaluated using sequence data from three plastid regions (rbcL, the trnL intron, and the trnL‐trnF intergenic spacer). Sixty‐six species representing the major genera of Staticoideae, including representatives of all sections and genera formerly included in Limonium, have been analyzed using four species of Plumbaginoideae as an outgroup. Analyses of each separate and combined data set yield similar results. Afrolimon is embedded in Limonium and related to L. vulgare, the type of Limonium. Limonium is split into two major clades corresponding to subgenera, but otherwise the current infrageneric classification proved to be artificial. Some groups restricted to particular areas can be recognized, and their synapomorphies are discussed. The presence of an isolated taxon in the Canary Islands is used as a calibration point for age estimates of the major events in the genus, including migrations to the Southern Hemisphere, the Canary Islands, and Asia. The rapid radiation of Limonium in the Mediterranean basin appears to coincide with the desiccation of the Mediterranean Sea in the Messinian (late Miocene).
Within‐crown variation in the timing of leaf emergence and fall of Malaysian trees in association with crown development patterns
Authors: Osada Noriyuki , Takeda Hiroshi , Okuda Toshinori , Awang Muhamad
Published: February 2008

In aseasonal tropics, timing of leaf emergence and leaf fall may differ between the shoots of different crown parts within a tree. This is important for the efficient development of crowns because leaves should be produced as soon as enough carbohydrates are accumulated. This hypothesis was tested by investigating leaf demography over a 44‐mo period for 17 Malaysian trees and comparing the timings of leaf emergence and fall between the upper and lower crowns. The timings of leaf emergence were synchronized between the upper and lower crowns, but those of leaf fall were less synchronized in most trees. Greater rates of leaf production in the upper than in the lower crowns were attributable to the differences in the number of leaves that emerged per leaf emergence event, rather than differences in frequency of leaf emergence per year. Timings of leaf emergence and leaf fall were mainly simultaneous in the upper and lower crowns, but unsynchronized leaf production and leaf fall also occurred. Such limited plasticity of leaf demography within crowns may be the result of physiological integration of branches or the compromise between the advantages of satiating herbivores and effective crown development in the trees of aseasonal tropics.
Codon usage patterns distort phylogenies from or of DNA sequences
Authors: Christianson Michael L.
Published: February 2008

Papers reporting phylogenetic reconstructions often include discussion of the nature of third position substitutions and have often treated third position data differently from other data. This paper extends such considerations. Plant biotechnologists interested in high levels of expression of foreign proteins have accumulated information on preferences for otherwise synonymous codons. This paper presents a simple analysis for codon bias. Not only is bias frequent, but bias also varies between cohorts of proteins, both by amino acid and by taxon. Analysis of codon usage in the parallel divergence of phytochromes in three model plants finds identical bias for all family members within each taxon and increasingly divergent patterns of bias between increasingly divergent taxa. The molecular constraint of taxon‐specific pools of tRNA molecules means individual triplets in a coding sequence are often not independent; algorithms designed to analyze independent characters are inappropriate for such data. Although a misestimate of the number of differences between taxa and groups of taxa can still generate an accurate description of the nesting of clades, other phylogenetic parameters will be strongly affected. Importantly, since codon bias produces smaller‐than‐expected within‐taxon variance (common use of favored triplets) and larger‐than‐expected between‐taxa variance (different favorites in different taxa), statistical support for nodes is certain to be wrong. The translational control of gene expression mediated by codon bias has implications for modern molecular systematics.
Pollination success across an elevation and sex ratio gradient in gynodioecious Daphne laureola
Authors: Alonso Conchita
Published: February 2008

Gynodioecy is a dimorphic breeding system in which hermaphrodite and female individuals coexist in populations. Sex ratio and gender‐relative lifetime seed production determine the stability of gynodioecy, and both genetic and ecological factors may influence these parameters. I analyzed the consequences of variation in population sex ratio and site elevation for the relative pollination success of female and hermaphrodite individuals of Daphne laureola in southern Spain, where previous studies failed to detect female fecundity advantages at two mid‐elevation sites. Pollination success, estimated as stigmatic pollen loads, number of pollen tubes per style, and percentage of fertilized flowers, was higher for hermaphrodites than females in populations with 20–56% females. Furthermore, female quantitative disadvantage in pollination success increased with elevation, suggesting that the higher availability of pollen due to the increased proportion of hermaphrodites could not mitigate the negative effect that other factors associated with elevation apparently had on pollination. Supplemental hand pollinations showed that female seed production was pollen limited in populations with a proportion of females >50%, although both pollination success and natural fruit set of females in these sites were the highest recorded.
Nectar traits in Nicotiana section Alatae (Solanaceae) in relation to floral traits, pollinators, and mating system
Authors: Kaczorowski Rainee L. , Gardener Mark C. , Holtsford Timothy P.
Published: February 2008

Nicotiana section Alatae exhibits great diversity among species in floral morphology, mating system, and predominant pollinators. As a first step towards estimating nectar's role in floral evolution, we studied nectar traits to determine whether they vary in association with predominant pollinators and mating system. Daily phenology determines when nectar becomes available to pollinators and differed between hummingbird‐ and moth‐pollinated species. Nectar volume and concentration varied significantly among most species and pollinator groups, but were inversely correlated, so that total energy was similar among most species. In general, nectar volume was positively correlated with corolla length. The autogamous species, N. plumbaginifolia, had a nectar volume that matched expectations based on corolla length, but with lower concentration and total energy than predicted by corolla length, while nectar volume was lower than predicted by corolla length in the autogamous population of N. longiflora. Sugar and amino acid components (determined through HPLC) were similar among species, although differences did exist. The nectar of most species was sucrose‐dominant, but the autogamous N. plumbaginifolia had nectar that contained similar proportions of sucrose, glucose, and fructose. Many nectar traits varied in association with the predominant pollinators and, in some cases, with the mating system.
Welwitschiaceae from the Lower Cretaceous of northeastern Brazil
Authors: Dilcher David L. , Bernardes‐De‐Oliveira Mary E. , Pons Denise , Lott Terry A.
Published: February 2008

Welwitschiaceae, a family in the Gnetales, is known today from only one extant species, Welwitschia mirabilis. This species is distributed in the Namibian desert, along the western coast of southern Africa, about 10 km inland from the coast. Very little is known about the fossil record of this family. Lower Cretaceous megafossils of various organs, assigned to Welwitschiaceae, are presented here. These fossils include young stems with paired cotyledons attached (Welwitschiella austroamericana n. gen. et sp.), isolated leaves (Welwitschiophyllum brasiliense n. gen. et sp.), and axes bearing male cones (Welwitschiostrobus murili n. gen. et sp.). They were collected in the Crato Formation, which is dated by palynomorphs and ostracods as Late Aptian (114 to 112 million years ago). These sediments are exposed in the Araripe Basin of northeastern Brazil. This study brings together new information of the megafossil record of Welwitschia‐like plants and also reports of pollen said to be similar to that of Welwitschia from Lower Cretaceous sediments.
Testing for stress‐dependent inbreeding depression in Impatiens capensis (Balsaminaceae)
Authors: Heschel M. Shane , Hausmann Neil , Schmitt Johanna
Published: February 2008

The relevance of inbreeding depression to the persistence of plant populations can depend upon whether stress magnifies inbreeding depression for fitness‐related traits. To examine whether drought stress exacerbates inbreeding depression in gas exchange traits and biomass, we grew selfed and outcrossed progeny of inbred lines from two populations of Impatiens capensis in a greenhouse experiment under water‐limited and moist soil conditions. Drought stress did not magnify the degree of inbreeding depression for any of the traits measured. In fact, in one population there was a trend for stronger inbreeding depression under well‐watered, benign conditions. Furthermore, significant inbreeding depression for carbon assimilation rate and stomatal conductance was only detected in the lines from one population. In contrast, inbreeding depression for biomass was detected within both populations and differed among lines. Drought stress exerted significant selection on physiological traits, favoring increased carbon assimilation rates and decreased stomatal conductance in drought‐stressed plants. Patterns of selection did not differ between inbred and outcrossed plants but did differ marginally between populations. Thus, estimates of selection were not biased by the mixed mating system per se, but may be biased by combining individuals from populations with different histories of selection and inbreeding.
Exploitation of a specialized mutualism by a deceptive orchid
Authors: Anderson Bruce , Johnson Steven D. , Carbutt Clinton
Published: February 2008

Plants that lack floral rewards may nevertheless attract pollinators through mimetic resemblance to the flowers of co‐occurring rewarding plants. We show how a deceptive orchid (Disa nivea) successfully exploits a reciprocally specialized mutualism between a nectar‐producing plant (Zaluzianskya microsiphon) and its long‐proboscid fly pollinator (Prosoeca ganglbaueri). Disa nivea is a rare southern African orchid known only from habitats that support large populations of Z. microsiphon, which it closely resembles in both general morphology and floral spectral reflectance. Significant covariation in floral traits of Z. microsiphon and D. nivea was detected among populations. Where mimics are uncommon, flies do not appear to discriminate between the flowers of the two species. Pollination success in D. nivea was much higher at a site with abundant Z. microsiphon plants than at a site where Z. microsiphon was rare. Exploitation of a highly specialized mutualism appears to demand a high degree of phenotypic resemblance to a rewarding model by a deceptive mimic, as exemplified by D. nivea. The majority of deceptive orchids, on the other hand, exploit relatively generalized pollination systems and thus require only a vague resemblance to rewarding plants in the community in order to attract pollinators.
Speciation and hybridization amongHoustonia(Rubiaceae) species: the influence of polyploidy on reticulate evolution
Authors: Church Sheri A. , Taylor Douglas R.
Published: February 2008

Chloroplast and nuclear DNA sequence variation among populations and species was used to examine the phylogenetic history and hybridization of the North AmericanHoustonialineage. The ancestral species in the lineage do not show evidence of hybridization; however, the more recently derived species in eastern North America contain a wide degree of morphological and genetic variation both within and among species. Furthermore, there is a clear association between hybridization and polyploidy in theHoustonialineage, with all potential hybrids occurring among species that contain polyploid populations. This suggests that polyploidy may break down species barriers and allow hybridization among lineages. These results indirectly support speciation models that involve genetic incompatibilities among species arising from gene silencing or genomic reorganization.
Biomechanics and development of the climbing habit in two species of the South American palm genusDesmoncus(Arecaceae)
Authors: Isnard Sandrine , Speck Thomas , Rowe Nick P.
Published: February 2008

Mechanical properties are investigated inDesmoncus orthacanthosandD. polyacanthosfrom French Guiana, South America. Differences in size and axis stiffness are related to different trellis requirements and habitats. The leaf sheath surrounds the stem, increasing stiffness of young self‐supporting stages and apical parts of older climbing plants. Senescence of the leaf sheath reduces stiffness of older climbing axes of both species. Its eventual loss inD. orthacanthosfacilitates deformation into coils and loops when plants slip from their supports following senescence of leaves bearing attachment organs. In smaller climbing axes ofD. polyacanthos, the senescent leaf sheath remains attached and axes rarely form loops and coils below attachment. An increase in stiff mechanical properties toward the base of both species is radically different from that of many dicotyledonous lianas. Besides the presence of attachment organs, stem mechanical properties ofDesmoncusare similar to those of erect though not fully self‐supporting stems ofBactris major, a sympatric species of the sister group genus toDesmoncus. The climbing habit inDesmoncusmay have evolved via (1) heterochronic processes including early elongation of internodes relative to increase in stem diameter (reduction of the establishment phase) and (2) increased persistence of leaf sheaths.
Nuclear DNA, chloroplast DNA, and ploidy analysis clarified biological complexity of the Vandenboschia radicans complex (Hymenophyllaceae) in Japan and adjacent areas
Authors: Ebihara Atsushi , Ishikawa Hiroshi , Matsumoto Sadamu , Lin Su‐Juan , Iwatsuki Kunio , Takamiya Masayuki , Watano Yasuyuki , Ito Motomi
Published: February 2008

Species complexes consisting of ill‐defined “species” are widely known among ferns, and their involvement with reticulate evolution is expected. Nevertheless approaches to reticulation history with DNA markers are not yet commonly adopted. We have successfully elucidated the biological status of the Vandenboschia radicans complex in East Asian islands by combining analyses of ploidy level, a cpDNA marker (rbcL), and a nuclear DNA marker (GapCp). The results based on 266 individuals collected from 174 localities throughout Japan and Taiwan suggest that complicated hybridizations have occurred involving at least three parental diploid species from within the V. radicans complex and Vandenboschia liukiuensis, which was formerly considered to be distinct from this complex. Triploids are the most common cytotype, but they show no evidence of apogamous reproduction, while all nonhybrid diploids are rare and have very limited distribution. Possible accounts of this phenomenon will be briefly discussed including the possibility of relict distribution and occasional apogamous reproduction.
Life history and systematics of the aquatic discomycete Mitrula (Helotiales, Ascomycota) based on cultural, morphological, and molecular studies
Authors: Wang Zheng , Binder Manfred , Hibbett David S.
Published: February 2008

Mitrula species represent a group of aquatic discomycetes with uncertain position in the Helotiales and an unknown life history. Mitrula species were studied using a combination of cultural, morphological, and molecular techniques. Pure colonies were isolated from Mitrula elegans, and conidia were induced in vitro. Herbarium materials from Europe, Asia, and North America were studied. Sequences of rDNA, including partial small subunit rDNA, large subunit DNA and ITS, were used to infer phylogenetic relationships both within Mitrula and between Mitrula and other inoperculate discomycetes, with special attention to fungi that resemble Mitrula in morphology or ecology. Equally weighted parsimony analyses, likelihood analyses, constrained parsimony analyses, and Bayesian analyses were performed. Results suggest that (1) the anamorph of M. elegans produces brown bicellular conidia, (2) a new subalpine species M. brevispora is distinct, (3) more than six lineages and clades can be recognized in Mitrula, (4) the morphological species M. elegans is not monophyletic, (5) a close relationship between Mitrula and either Geoglossaceae or Sclerotiniaceae is not supported, (6) the Helotiaceae is paraphyletic, and (7) Mitrula belongs to a clade within the Helotiales that also includes other aero‐aquatic genera, Cudoniella, Hydrocina, Vibrissea, Ombrophila, and Hymenoscyphus.
The evolution and expression of RBCL in holoparasitic sister‐genera Harveya and Hyobanche (Orobanchaceae)
Authors: Randle Christopher P. , Wolfe Andrea D.
Published: February 2008

The evolution of holoparasitism decreases the adaptive value of genes maintaining the photosynthetic apparatus. These may become pseudogenes through insertion or deletion events resulting in frameshift mutations, or by the evolution of premature stop codons. The holoparasitic sister genera Harveya and Hyobanche have undergone alternate pathways of evolution and expression at the plastid locus rbcL. An open reading frame in all but a single species of Harveya is maintained by purifying selection and is expressed. However, the function of Rubisco in this putative holoparasite is unknown. Conversely, Hyobanche has undergone rbcL pseudogene formation, and comparison of synonymous and nonsynonymous rates of evolution indicates that selection has not played a role in its evolution. This is complicated by the following findings: multiple pseudogene copies of rbcL exist in tissues of Hyobanche, rbcL transcripts also encode pseudogenes, and the large subunit is present in some tissues of Hyobanche. We hypothesize that the rbcL operon is in a state of degradation as may be expected in a holoparasite and is not endogenously expressed. Rather, the large subunit may be taken up from the host plants, and accumulate in tissues as a result of transpiration.
Floral development in three species of Impatiens (Balsaminaceae)
Authors: Caris Pieter L. , Geuten Koen P. , Janssens Steven B. , Smets Erik F.
Published: February 2008

The floral morphological and developmental patterns in three species of Impatiens (Balsaminaceae), namely I. columbaria, I. hawkeri, and I. niamniamensis, were studied to contribute to a better understanding of floral evolution in the genus. Strangely enough, the highly diverse floral morphology and ontogeny of this horticulturally important genus have never been studied thoroughly (e.g., using scanning electron microscopic techniques). We discuss the position and the developmental sequence of the different perianth members. We hypothesized that in the course of evolution, the anterolateral sepals become reduced and that a morphocline can be recognized going from species with five sepals, over species with rudimentary sepals that fuse postgenitally with the anterior petal, to species where congenital fusion between these sepals and the anterior petal has taken place. Ovules generally are in one or two vertical rows per locule, but there are several vertical rows per locule in I. columbaria. The outer parts of the septa disintegrate to enable the explosive dehiscence of the capsules.
The interactive effects of light and temperature on heat‐shock protein accumulation in Solidago altissima (Asteraceae) in the field and laboratory
Authors: Barua Deepak , Heckathorn Scott A.
Published: February 2008

Heat‐shock proteins (HSPs) protect cells from abiotic stresses. However, most work on HSPs in plants has been carried out in laboratory‐grown crop or model species. Few studies have examined field expression of HSPs or HSP expression in response to multiple stresses that often occur simultaneously in nature. Heat stress in nature is frequently accompanied by high light, and photoinhibition is a major limitation for photosynthesis. Light induction of HSPs may help ameliorate damage from excess light. In this study, we asked if accumulation of representative HSPs differed in naturally occurring Solidago altissima (goldenrod) in contrasting light microclimates (open sun vs. shade) and on cool vs. warm days. Our results show that HSP content in field‐grown plants, undergoing natural temperature stress, was greater in open sun than shaded environments. Supporting these results, both light and temperature significantly affected accumulation of HSPs in the laboratory. This is the first study to show that the interaction of light microclimate and temperature can significantly influence HSP accumulation in field‐grown plants.
Genome size evolution in holoparasitic Orobanche (Orobanchaceae) and related genera
Authors: Weiss‐Schneeweiss Hanna , Greilhuber Johann , Schneeweiss Gerald M.
Published: February 2008

Genome size was estimated using Feulgen densitometry for 76 accessions of 40 taxa of Orobanche and two taxa each of the related genera Phelypaea and Cistanche, providing the first data set for any group of nonphotosynthetic angiosperms. The 2C‐values were 16.8–19.9 pg in Cistanche, 2.9–11.6 pg in Orobanche sect. Orobanche, 6.8–10.8 pg in sect. Trionychon, 4.3–5.1 pg in sect. Myzorrhiza, and 4.9–5.8 pg and 10.5 pg in the two diploid species Phelypaea coccinea and P. tournefortii, respectively. Distribution of genome size is congruent with phylogenetic lineages identified by analyses of nuclear ITS sequence data, in particular regarding the distinctness of O. anatolica from the rest of sect. Orobanche. With the exception of tetraploid O. transcaucasica, polyploid taxa of sect. Orobanche are among those with the smallest C‐values, suggesting substantial genome downsizing after polyploidization (as in other angiosperm groups). In O. sect. Orobanche, genome size evolved more rapidly in earlier stages of its evolution than in later stages. This might be indicative of adaptive radiation, but this hypothesis requires corroboration in the form of genome size estimates on more taxa and accessions.