bluuebunny/crossref_metadata_2025 huggingface dataset:
Reproductive biology ofLactoris fernandeziana(Lactoridaceae)
Authors: Bernardello Gabriel , Anderson Gregory J. , Lopez S. Patricio , Cleland Maryke A. , Stuessy Tod F. , Crawford Daniel J.
Published: April 2006

Lactoris fernandeziana,monotypic in its family, is endemic to the cloud forests of Robinson Crusoe Island. Although there has been considerable study of the relationships ofLactoris,as a rare species and as a putative primitive paleoherb, little is known of its reproductive biology. Knowledge of the latter is essential for effective conservation programs. The species is gynomonoecious. The overall proportion of flowers is ∼1 female:1 hermaphrodite. The inconspicuous semipendulous green flowers, usually in mixed‐gender inflorescences, do not produce rewards. Hermaphrodite flowers are herkogamous and protogynous. Pollen grains are shed from the extrorse anthers in permanent dry tetrads. There is a mean of 12879 tetrads per hermaphrodite flower. Both flower types bear an average of ∼18 ovules. The P/O (pollen/ovule) ratios imply facultative or obligate xenogamy, but hand pollinations show thatLactorisis self‐compatible. No floral visitors were ever observed, but stigmata of open‐pollinated flowers bore tetrads, and 64% of such styles had pollen tubes. Flowers enclosed in large mesh (1 mm) bags bore similar numbers of tetrads and pollen tubes. Thus, we conclude thatLactorisis anemophilous, a syndrome perhaps reflected by the P/O ratio. Low genetic diversity (isozymes and DNA) supports selfing and implies limited distance wind pollen dispersal. The small size of the island, the ± 1000 extantLactorisplants, coupled with anemophily, self‐compatibility, and pendant flower position, have yielded a geitonogamous system with high seed set and low genetic diversity. If inbreeding depression is expressed, it is in seed germination and seedling vigor, forLactorisis very difficult to cultivate. For this species, effective conservation practices need to focus on habitat preservation and promotion of outcrossing.
Differential ovule development following self‐ and cross‐pollination: the basis of self‐sterility in Narcissus triandrus (Amaryllidaceae)
Authors: Sage Tammy L. , Strumas Fanny , Cole William W. , Barrett Spencer C. H.
Published: April 2006

Self‐pollination results in significantly lower seed set than cross‐pollination in tristylous Narcissus triandrus. We investigated structural and functional aspects of pollen–pistil interactions and ovule–seed development following cross‐ and self‐pollination to assess the timing and mechanism of self‐sterility. Ovule development within an ovary was asynchronous at anthesis. There were no significant differences in pollen tube behavior following cross‐ vs. self‐pollination during the first 6 d of growth, regardless of style morph type. Double fertilization was significantly higher following cross‐ vs. self‐pollination. Aborted embryo development was not detected following either pollination type up to seed maturity. Prior to pollen tube entry, a significantly greater number of ovules ceased to develop following self‐ vs. cross‐pollination. These results indicate that self‐sterility in N. triandrus operates prezygotically but does not involve differential pollen tube growth typical of many self‐incompatibility (SI) systems. Instead, low seed set following self‐pollination is caused by a reduction in ovule availability resulting from embryo sac degeneration. We hypothesize that this is due to the absence of a required stimulus for normal ovule development. If this is correct, current concepts of SI may need to be broadened to include a wider range of pollen–pistil interactions.
In situ fossil seedlings of a Metasequoia‐like taxodiaceous conifer from Paleocene river floodplain deposits of central Alberta, Canada
Authors: Falder Amy B. , Stockey Ruth A. , Rothwell Gar W.
Published: April 2006

Fossil seeds and seedlings of a Metasequoia‐like taxodiaceous conifer occur in Paleocene deposits at the Munce's Hill and Gao Mine localities of central Alberta, Canada. Compression/impression specimens are preserved in upright growth positions among seedlings of the cercidiphyllaceous dicot Joffrea speirsii Crane & Stockey. There are a large number of seeds, a few of which were buried while germinating and show a radicle or short primary root. More than 500 Metasequoia‐like seedlings have been identified that have two linear cotyledons with parallel margins and rounded tips. Three specimens have been found that display three cotyledons. Slightly older seedlings show decussate pairs of leaves attached to the stem distal to the cotyledons. Still older seedlings have axillary branches that show varying sizes and numbers of opposite leaves arranged in a single plane distal to the opposite pairs. These specimens reveal that both Joffrea and this extinct taxodiaceous conifer were early colonizers of North American floodplain communities at the beginning of the Tertiary.
Variation among populations ofClarkia Unguiculata(Onagraceae) along altitudinal and latitudinal gradients
Authors: Jonas Christine S. , Geber Monica A.
Published: April 2006

We investigated phenotypic variation in 15 traits in greenhouse‐grown plants from 16 populations ofClarkia unguiculatafrom three elevational habitats and six latitudinal transects. Populations from the lowest and highest elevations were geographically and ecologically marginal within the species’ range. We (1) describe patterns of trait variation with elevation and latitude; (2) compare latitutidinal variation between marginal and central areas of the species’ range; and (3) compare patterns of variation withinC. unguiculatato interspecific patterns within the genus. Although there was some evidence that traits varied clinally (i.e., increased/decreased monotonically) along environmental gradients, interaction effects between altitude and latitude dominated patterns of variation. For most traits, latitudinal trends at the low‐elevation margin of the species’ range differed from trends at mid‐ and high‐elevation areas. Based on interspecific comparisons, populations at the hotter, more arid ends of both environmental gradients were expected to have rapid development, small flowers and vegetative size, low levels of herkogamy and protandry, and high rates of gas exchange. Instead, we found that while some traits were correlated with one gradient in the expected way (e.g., development time with elevation, gas‐exchange physiology with latitude), all traits were not consistently associated with each other along both gradients, and intraspecific patterns of variation differed from interspecific patterns.
Phylogenetic relationships of land plants using mitochondrial small‐subunit rDNA sequences
Authors: Duff R. Joel , Nickrent Daniel L.
Published: April 2006

Phylogenetic relationships among embryophytes (tracheophytes, mosses, liverworts, and hornworts) were examined using 21 newly generated mitochondrial small‐subunit (19S) rDNA sequences. The “core” 19S rDNA contained more phylogenetically informative sites and lower homoplasy than either nuclear 18S or plastid 16S rDNA. Results of phylogenetic analyses using parsimony (MP) and likelihood (ML) were generally congruent. Using MP, two trees were obtained that resolved either liverworts or hornworts as the basal land plant clade. The optimal ML tree showed hornworts as basal. That topology was not statistically different from the two MP trees, thus both appear to be equally viable evolutionary hypotheses. High bootstrap support was obtained for the majority of higher level embryophyte clades named in a recent morphologically based classification, e.g., Tracheophyta, Euphyllophytina, Lycophytina, and Spermatophytata. Strong support was also obtained for the following monophyletic groups: hornworts, liverworts, mosses, lycopsids, leptosporangiate and eusporangiate ferns, gymnosperms and angiosperms. This molecular analysis supported a sister relationship betweenEquisetumand leptosporangiate ferns and a monophyletic gymnosperms sister to angiosperms. The topologies of deeper clades were affected by taxon inclusion (particularly hornworts) as demonstrated by jackknife analyses. This study represents the first use of mitochondrial 19S rDNA for phylogenetic purposes and it appears well‐suited for examining intermediate to deep evolutionary relationships among embryophytes.
Phylogenetic relationships of subtribe Ecliptinae (Asteraceae: Heliantheae) based on chloroplast DNA restriction site data
Authors: Panero Jose L. , Jansen Robert K. , Clevinger Jennifer A.
Published: April 2006

Phylogenetic analysis of chloroplast DNA restriction site data for 76 of the 302 genera of Heliantheae sensu lato using 16 restriction endonucleases reveals that subtribe Ecliptinae is polyphyletic and that its genera are distributed in four different lineages. The ecliptinous genera Squamopappus, Podachaenium, Verbesina, and Tetrachyron (of the Neurolaeninae), along with other members of subtribe Neurolaeninae are the basalmost clades of the paleaceous Heliantheae. The mostly temperate species of subtribe Ecliptinae (exemplified by Balsamorhiza, Borrichia, Chrysogonum, Engelmannia, Silphium, Vigethia, and Wyethia) are strongly nested in a clade with the Mesoamerican monotypic genus Rojasianthe as basal. The genera characterized by marcescent ray corollas traditionally classified in subtribe Zinniinae constitute a strongly supported group sister to Acmella, Spilanthes, and Salmea. The largest clade of ecliptinous genera is the most recently derived group within Heliantheae sampled. This large group of mostly Neotropical lowland genera (variously characterized by their winged cypselae, foliaceous phyllaries, and opposite phyllotaxy and exemplified by Perymenium, Wedelia, and Zexmenia) has been and continues to be the most challenging group from a taxonomic standpoint. The study provides new insights as to their relationships that will have a positive impact in future monographic studies of the group. The genera of the Espeletiinae form a monophyletic clade and are sister to members of the Milleriinae and Melampodiinae. This result is consistent with their traditional taxonomic placement with genera such as Smallanthus with which they share a tendency for functionally staminate disc flowers. The phylogenetically enigmatic genus Montanoa is sister to Melampodium. Members of subtribe Galinsoginae are clustered in two main lineages that correspond to the traditional division of the subtribe based on pappus characteristics. There is no support for the monophyly of subtribe Galinsoginae, and the same results indicate some of its genera are paraphyletic.
Genetic diversity of Typha latifolia (Typhaceae) and the impact of pollutants examined with tandem‐repetitive DNA probes
Authors: Keane Brian , Pelikan Stephan , Toth Greg P. , Smith M. Kate , Rogstad Steven H.
Published: April 2006

Genetic diversity at variable‐number‐tandem‐repeat (VNTR) loci was examined in the common cattail, Typha latifolia (Typhaceae), using three synthetic DNA probes composed of tandemly repeated “core” sequences (GACA, GATA, and GCAC). The principal objectives of this investigation were to determine whether: (1) the previously reported almost complete lack of polymorphism at allozyme loci in this species was indicative of a reduced amount of genetic diversity at VNTR loci as well; (2) VNTR markers were informative about possible clonal propagation; and (3) significant differences in genetic structure of sampling sites were associated with differences in environmental levels of pollutants at those sites. Previously, widespread sampling across the eastern United States, surveying across ten allozyme loci, has detected only two genotypes, involving a difference at a single locus, among 104 populations. In this study, the amount of genetic diversity detected at VNTR loci: (1) among ramets (N = 40; 40 genotypes detected) collected at ∼8‐km intervals along a 320‐km transect; (2) among ramets (N = 220; 117 genotypes detected) from five study sites separated by 50–3000 m; and (3) even among ramets within each study site [N = 44 per site; from 13 to 34 genotypes detected per site (270 m2)] exceeds that previously found in those more geographically widespread allozyme surveys. Among the 260 ramets analyzed here, the mean number of bands scored per individual was 48.61 (SD = 2.80). Mean genetic similarity among ramets collected along the 320‐km transect was 0.91, which was within the range of mean genetic similarity within the five study sites (range: 0.89–0.95). Among the five study sites, 61% of the samples analyzed appeared to be clonal ramets, with up to 12 clones detected for 44 ramets sampled within a site. Clones grew intermingled and ranged up to 39 m in extent. Permutation tests of genetic similarity revealed significant genetic differentiation between each of the five study sites. Consistent with the previous allozyme studies, T. latifolia was characterized by extremely low genetic variation relative to levels of polymorphism detected at VNTR loci in other plant species. Estimated heterozygosity among ramets along the 320‐km transect ranged from 0.11 to 0.13, while that within the five study sites ranged from 0.05 to 0.12. Estimates of Fst (0.32–0.41) also indicated considerable genetic subdivision among these stands. Significantly higher genetic diversity was detected at the two study sites that chemistry and toxicity data indicate to be the most severely impacted by pollutants. Although this correlation does not establish cause and effect, the results of this study indicate that the analysis of genetic diversity at VNTR loci may be a useful tool for monitoring anthropogenic‐induced changes in the genetic structure of natural populations of plants.
Convergence and correlations among leaf size and function in seed plants: a comparative test using independent contrasts
Authors: Ackerly David D. , Reich Peter B.
Published: April 2006

Prior studies of a broad array of seed plants have reported strong correlations among leaf life span, specific leaf area, nitrogen concentration, and carbon assimilation rates, which have been interpreted as evidence of coordinated leaf physiological strategies. However, it is not known whether these relationships reflect patterns of evolutionary convergence, or whether they are due to contrasting characteristics of major seed plant lineages. We reevaluated a published data set for these seven traits measured in over 100 species, using phylogenetic independent contrasts calculated over a range of alternative seed plant phylogenies derived from recent molecular systematic analyses. In general, pairwise correlations among these seven traits were similar with and without consideration of phylogeny, and results were robust over a range of alternative phylogenies. We also evaluated relationships between these seven traits and lamina area, another important aspect of leaf function, and found moderate correlations with specific leaf area (0.64), mass‐based photosynthesis (0.54), area‐based nitrogen (−0.56), and leaf life span (−0.42). However, several of these correlations were markedly reduced using independent contrasts; for example, the correlation between leaf life span and lamina area was reduced to close to zero. This change reflects the large differences in both these traits between conifers and angiosperms and the absence of a relationship between the traits within these groups. This analysis illustrates that most interspecific relationships among leaf functional traits, considered across a broad range of seed plant taxa, reflect significant patterns of correlated evolutionary change, lending further support to the adaptive interpretation of these relationships.
Loss of water transport capacity due to xylem cavitation in roots of two CAM succulents
Authors: Linton Matthew J. , Nobel Park S.
Published: April 2006

Loss of axial hydraulic conductance as a result of xylem cavitation was examined for roots of the Crassulacean acid metabolism (CAM) succulents Agave deserti and Opuntia ficus‐indica. Vulnerability to cavitation was not correlated with either root size or vessel diameter. Agave deserti had a mean cavitation pressure of −0.93 ± 0.08 MPa by both an air‐injection and a centrifugal method compared to −0.70 ± 0.02 MPa by the centrifugal method for O. ficus‐indica, reflecting the greater tolerance of the former species to low water potentials in its native habitat. Substantial xylem cavitation would occur at a soil water potential of −0.25 MPa, resulting in a predicted 22% loss of conductance for A. deserti and 32% for O. ficus‐indica. For an extended drought of 3 mo, further cavitation could cause a 69% loss of conductance for A. deserti and 62% for O. ficus‐indica. A model of axial hydraulic flow based upon the cavitation response of these species predicted that water uptake rates are far below the maximum possible, owing to the high root water potentials of these desert succulents. Despite various shoot adaptations to aridity, roots of A. deserti and O. ficus‐indica are highly vulnerable to cavitation, which partially limits water uptake in a wet soil but helps reduce water loss to a drying soil.
Phenylurea cytokinins assayed for induction of shoot buds in the moss Funaria hygrometrica
Authors: Christianson Michael L. , Hornbuckle Jason S.
Published: April 2006

The induction of shoot buds from the filamentous protonema of moss is a classic bioassay for cytokinin. While a large literature documents this response in many species of moss and for a wide range of natural and synthetic cytokinins, to date only substituted adenine cytokinins have been examined in detail. This paper shows that at least some of the novel phenylurea cytokinins will induce bud formation in mosses. Funaria responds to thidiazuron much as it responds to benzyladenine. Exposure to either substance results in log‐linear dose‐dependent increases in bud number that reach similar maximal numbers of buds at the optimal concentration of compound. The related compound chloro‐pyridyl‐phenylurea (CPPU) is slightly less active, but induces buds over a wider range of concentration. Carbanilide (diphenylurea or DPU), an active cytokinin in other systems, induces very few buds in Funaria, but does so over a wide range of concentration. Bioassay of mixtures of benzyladenine and DPU finds no evidence of competition for cytokinin receptors. That result could support suggestions that the phenylurea cytokinins act indirectly, by altering endogenous cytokinin metabolism, but we favor another interpretation. Unlike other cytokinin‐responsive systems, the induction of buds from moss protonema involves two cytokinin‐mediated events. The number of buds is controlled by the second cytokinin‐mediated event. If DPU has little or no affinity for the receptor triggering this second event, DPU treatments will produce few to no buds, and kinetic analysis using bud number would find no evidence for competition with benzyladenine. Our results would support the hypothesis that bud induction in Funaria involves two chemically distinct cytokinin receptors.
The pollination ecology of buzz‐pollinated Rhexia virginica (Melastomataceae)
Authors: Larson Brendon M. H. , Barrett Spencer C. H.
Published: April 2006

We examined the function of floral traits associated with buzz pollination through studies of Rhexia virginica (Melastomataceae) in the Muskoka region of Ontario, Canada. Controlled pollinations demonstrated that the species is self‐compatible, but dependent on insects for pollen transfer. Bumble bees made 82 and 90% of observed insect visits to R. virginica in 1996 and 1997, respectively, and effectively buzzed flowers. Buzz pollination did not appear to be highly “specialized” since various species of bumble bee were capable of pollination, and pollen transfer efficiency appeared to be relatively low. Experimental manipulations provided little support for the hypothesis that the yellow color of melastome anthers mimics abundant pollen, thereby deceiving pollinators to visit regardless of whether most pollen has been removed. Fruit set averaged 52.6% among populations, owing largely to infrequent pollinator visits and pollen limitation. Flowers of R. virginica were infertile after a single day of anthesis, but petals were subsequently maintained for 1–2 d and stamens underwent a color change from bright yellow to red. Second‐day flowers may function to increase floral display size and hence fertility, without a concomitant increase in pollen discounting. Studies of bumble bee foraging behavior and correlates of seed set provided indirect support for this hypothesis.
Morphological variation and the process of domestication of Stenocereus stellatus (Cactaceae) in Central Mexico
Authors: Casas Alejandro , Caballero Javier , Valiente‐Banuet Alfonso , Soriano Jose Antonio , Da´vila Patricia
Published: April 2006

Morphological variation was analyzed in wild, managed in situ, and cultivated populations of the columnar cactus Stenocereus stellatus in central Mexico. The purpose was to evaluate whether morphological divergence between manipulated and wild populations has resulted from domestication processes. Variation of 23 morphological characters was analyzed among 324 individuals from 19 populations of the Tehuaca´n Valley and La Mixteca Baja. Multivariate statistical analyses were used to group individuals and populations according to their morphological similarity. Individuals grouped according to the way of management and fruit characteristics were the most relevant for grouping. Within each region, sweet fruits with pulp colors other than red were more frequent in cultivated populations, where fruits were also larger, contained more and bigger seeds, and had thinner peel and fewer spines than fruits from wild individuals. Phenotypes common in managed in situ and cultivated populations generally occur in the wild but in lower frequencies. Artificial selection has thus operated by enhancing and maintaining desirable rare phenotypes in managed in situ and cultivated populations, causing divergent patterns of morphological variation from wild populations. Cultivation has caused the strongest level of divergence, but divergence has also been significant with management of wild populations in situ.
Reproductive biology and the process of domestication of the columnar cactus Stenocereus Stellatus in Central Mexico
Authors: Casas Alejandro , Valiente‐Banuet Alfonso , Rojas‐Marti´nez Alberto , Da´vila Patricia
Published: April 2006

Pollination biology, breeding system, and floral phenology of the columnar cactus Stenocereus stellatus were studied in wild, wild managed in situ and cultivated populations of central Mexico, in order to examine whether these aspects have been modified under domestication and whether they determine reproductive barriers between wild and manipulated individuals. Individuals of both wild and manipulated populations are self‐incompatible, indicating that artificial selection has not modified the breeding system. Their pollination biology is also similar. Anthesis is mainly nocturnal, with a peak of nectar production between 0200 and 0400 when the stigma presents maximum turgidity. Nocturnal visitors are the effective pollinators. Nearly 75% of flowers exposed for nocturnal pollination set fruit, while none of the flowers exposed for diurnal pollination produced fruits. The bats Leptonycteris curasoae, L. nivalis, and Choeronycteris mexicana (Glossophaginae) are the most likely pollinators, and their time of foraging is synchronized with the time of nectar production and stigma receptivity in S. stellatus. Bats potentially move pollen over a considerable distance, so there is apparently no spatial isolation to prevent pollen exchange between wild and cultivated populations. Phenological studies showed that there are also no apparent temporal barriers. However, manual cross pollination failed between some domesticated and wild phenotypes, suggesting that gene flow between wild and cultivated populations might be limited by pollen incompatibility.
Mycorrhizal status of the genusCarex(Cyperaceae)
Authors: Miller R. Michael , Smith Christopher I. , Jastrow Julie D. , Bever James D.
Published: April 2006

The Cyperaceae have generally been considered nonmycorrhizal, although recent evidence suggests that mycotrophy may be considerably more widespread among sedges than was previously realized. This study surveyed 23 species ofCarexoccurring in upland and wetland habitats in northeastern Illinois. Mycorrhizal infection by arbuscular fungi was found in the roots of 16 species ofCarexand appears to occur in response to many factors, both environmental and phylogenetic. While some species appear to be obligately nonmycorrhizal, edaphic influences may be responsible for infection in others. In five of the sevenCarexspecies that were nonmycorrhizal, a novel root character, the presence of bulbous‐based root hairs, was identified. The taxonomically patchy distribution of the distinctive root hair trait suggests that these structures may have evolved several times within the genus. Evidence of multiple independent origins of the root hair trait lends support to the hypothesis that root hairs represent an adaptation to nonmycotrophy. Although taxonomic position does seem to be of importance in determining the mycorrhizal dependence of sedges, the pattern may be a patchwork of both mycorrhizal clades and clades that have adapted to the nonmycorrhizal state.
The phylogenetic position of Carex section Phyllostachys and its implications for phylogeny and subgeneric circumscription in Carex (Cyperaceae)
Authors: Starr Julian R. , Bayer Randall J. , Ford Bruce A.
Published: April 2006

Wide speculation surrounds the origin and phylogenetic relationships of the most highly reduced sections in the genus Carex. In order to gain a better understanding of phylogeny in Carex, the relationship of the reduced sect. Phyllostachys to 12 putatively related sections, representing all four subgenera (Primocarex, Indocarex, Carex, Vignea), was inferred from sequences of the ITS (internal transcribed spacer) region of nrDNA. Phylogenetic reconstructions identified two main clades: (1) a “compound” clade composed of sections from subg. Indocarex, Primocarex, and a portion of subg. Carex, and (2) a “reduced” clade consisting of sections from subg. Carex (Phyllostachys) and Primocarex (Filifoliae and Firmiculmes). Subgenus Indocarex was paraphyletic within the “compound” clade supporting classifications that have merged it within a wider subg. Indocarex/Carex/Primocarex line. Subgenus Primocarex was polyphyletic. This result was consistent with theories that extreme reduction has occurred along several different evolutionary lines in Carex. Phylogenetic theories inferred from the presence or abnormal growth of the rachilla were not supported by tree topologies. Difficult sectional circumscriptions, such as the separation of sections Laxiflorae and Careyanae, were strongly upheld by sequence data. The ITS region is an effective tool for defining sectional limits and for estimating relationships among sections in Carex, but does not provide enough phylogenetic information to fully resolve relationships below the sectional level.
Genetic variation and evolutionary trade‐offs for sexual and asexual reproductive modes in Allium vineale (Liliaceae)
Authors: Ronsheim Margaret L. , Bever James D.
Published: April 2006

Populations of Allium vineale commonly include individuals with very different allocation patterns to three modes of reproduction: sexual flowers, aerially produced asexual bulbils, and belowground asexual offsets. If selection is currently acting to maintain these different allocation patterns there must be a genetic basis for variation in allocation to these three reproductive modes. In addition, negative genetic correlations between reproductive traits would imply evolutionary trade‐offs among reproductive strategies. We evaluated the heritability of these allocation patterns by growing 16 clones from a single population in the greenhouse at two levels of fertilization. Bulb mass and the mass and number of bulbils, offsets, and flowers were used as response variables, in addition to the proportion allocated to each reproductive mode. We found evidence of substantial heritable variation in allocation to sexual reproduction and in allocation within the two modes of asexual reproduction, indicating high sensitivity of these allocation patterns to natural selection. We also found evidence of strong negative genetic correlations between bulbil and flower traits, as well as between bulbil and offset traits, with one group of genotypes allocating greater resources to aerial asexual bulbils and the second group allocating more resources to belowground asexual offsets and aerial flowers. Phenotypic plasticity in allocation to above‐ vs. belowground asexual reproduction and sexual vs. asexual aerial reproduction was limited, indicating that plants are unlikely to change reproductive mode in response to nutrient availability. Together, then, we have demonstrated strong heritability for, and trade‐offs in, the reproductive allocation patterns within this plant population.
Regional specialization of Sarcodes sanguinea (Ericaceae) on a single fungal symbiont from the Rhizopogon ellenae (Rhizopogonaceae) species complex
Authors: Kretzer Annette M. , Bidartondo Martin I. , Grubisha Lisa C. , Spatafora Joseph W. , Szaro Timothy M. , Bruns Thomas D.
Published: April 2006

We have sampled the mycorrhizal roots of 76 snow plants (Sarcodes sanguinea, Monotropoideae, Ericaceae) in two areas of the Sierra Nevada of California that are ∼180 km apart. To identify the fungal symbionts associated with these plants, we first analyzed restriction fragment length polymorphisms (RFLPs) of the internal transcribed spacer region (ITS) of the fungal nuclear ribosomal repeat. Fungal ITS‐RFLPs were successfully produced from 57 of the 76 plants sampled, and all symbionts shared the same DNA fragment pattern. The morphology of S. sanguinea mycorrhizae was consistent with that expected from a Rhizopogon species in section Amylopogon. To confirm and refine this identification, a total of six fungal ITS sequences were determined from S. sanguinea mycorrhizae. These sequences were analyzed together with eight existing and eight newly determined ITS sequences from Rhizopogon section Amylopogon. The newly determined sequences include an ITS sequence from the fungal symbiont of pine drops (Pterospora andromedea, Monotropoideae, Ericaceae), a plant that was previously reported to be exclusively associated with the Rhizopogon subcaerulescens group. When these sequences were analyzed together, the Sarcodes symbionts grouped tightly with several collections of R. ellenae including the holotype, one collection of R. idahoensis, and one collection of R. semireticulatus. A different lineage comprised collections of R. subgelatinosus, R. subcaerulescens, another collection of R. semireticulatus, and the Pterospora symbiont. We conclude that S. sanguinea associates exclusively with a single species in the R. ellenae species complex throughout our sampling range. These results indicate a much higher level of specificity in S. sanguinea than was previously reported and confirm the emerging pattern that nonphotosynthetic, monotropoid plants generally associate very specifically with a narrow range of ectomycorrhizal fungi.
Fitness consequences of branching in Verbascum thapsus (Scrophulariaceae)
Authors: Lortie Christopher J. , Aarssen Lonnie W.
Published: April 2006

The reserve meristem hypothesis proposes that strong apical dominance suppresses lateral meristems and branches to escape from predictable damage (herbivory). This hypothesis was tested for Verbascum thapsus and its seed predator the weevil Gynmnetron tetrum by two mensurative experiments. The following predictions were made under this hypothesis: the proportion of individuals branched within a population will increase with increased damage, the main stalk of branched plants will be more damaged, and branching increases net seed production. Fifty populations of V. thapsus were extensively surveyed, and one pair of similar‐sized individuals (branched vs. unbranched) were selected from each population to determine damage patterns and measure seed production. Two of the predictions of the reserve meristem hypothesis were clearly supported. The proportion of fruits damaged on the main stalk of branched plants was significantly greater than unbranched plants, and branched plants produced significantly more seeds. Hence, the reserve meristem hypothesis is supported as an adaptive interpretation of apical dominance in this species. This study is a potential example of overcompensation following granivory in the field.
Morphological variation ofPinus flexilis(Pinaceae), a bird‐dispersed pine, across a range of elevations
Authors: Schoettle A. W. , Rochelle S. G.
Published: April 2006

Limber pine (Pinus flexilisJames) grows across a wider range of elevations than any other tree species in the central Rockies, from ∼1600 m at Pawnee Buttes to >3300 m at Rollins Pass. In this study we investigated two possible explanations for limber pine's success across a broad range of elevations: (1) the sites on which it is found, although separated by >1000 m elevation, may not be very different with respect to environmental factors that affect tree growth, and (2) limber pine growth is insensitive to environmental factors that change with elevation. We compared site characteristics of 12 limber pine stands at elevations ranging from 1630 to 3328 m as well as the growth and morphology of trees in each of these stands. Mean daily air temperature in July decreased linearly with the elevation of the site from 22.8° to 12.6°C. The growth and morphology of limber pine leaves, shoots, and trees were, in general, not related to the elevation or July mean air temperature of the sites. There was, however, a significant decrease in stomatal density with increasing elevation, which may be an acclimational response to restrict water loss at high elevations. Our data suggest that the fundamental and realized niche of limber pine is broad with respect to air temperature. In light of the high gene flow and only slight genetic differentiation among populations of species with bird‐dispersed seeds, such as limber pine, it is especially unusual to see similar growth throughout an environmental gradient. Physiological and anatomical plasticity or wide physiological tolerance ranges may enable limber pine to uncouple its growth from its environment.
Floral ontogeny, pattern formation, and evolution in Hibbertia and Adrastaea (Dilleniaceae)
Authors: Tucker Shirley C. , Bernhardt Peter
Published: April 2006

Floral development was compared with scanning electron microscopy in 12 Australian species of Hibbertia representing most of its morphological variation, and in the related Adrastaea (Dilleniaceae). Calyx and corolla arise in quincuncial helices in radially symmetrical species, while the petals initiate unidirectionally from one side in zygomorphic species. Stamen number (3–200+) proliferates by centrifugal addition of individual primordia or by innovations of common primordia and ring meristems. Common primordia arise in single‐stamen positions alternately with petals, and each produces one to several stamens centrifugally that remain attached to a shared base and form a stamen fascicle. A ring meristem in Adrastaea initiates a whorl of five stamens, alternate with the first stamens but outside their whorl. In radially symmetrical species of Hibbertia, a first ring of stamens is supplemented centrifugally by additional stamens on a meristem ring. The first stamens in zygomorphic species of Hibbertia initiate as a terminal ridge on the floral apex, with subsequent stamens added centrifugally on one side and two carpels initiated on the opposite side. The carpels arise as a simultaneous ring in radially symmetrical flowers, or as a simultaneous pair in zygomorphic species. Staminodial presence is viewed as of minor significance. Four pollinator syndromes are proposed for Hibbertia, related to differing floral architecture.
Pollen dispersal in Yucca filamentosa (Agavaceae): the paradox of self‐pollination behavior by Tegeticula yuccasella (Prodoxidae)
Authors: Marr Deborah L. , Leebens‐Mack Jim , Elms Lindsey , Pellmyr Olle
Published: April 2006

We investigated pollen dispersal in an obligate pollination mutualism between Yucca filamentosa and Tegeticula yuccasella. Yucca moths are the only documented pollinator of yuccas, and moth larvae feed solely on developing yucca seeds. The quality of pollination by a female moth affects larval survival because flowers receiving small amounts of pollen or self‐pollen have a high abscission probability, and larvae die in abscised flowers. We tested the prediction that yucca moths primarily perform outcross pollinations by using fluorescent dye to track pollen dispersal in five populations of Y. filamentosa. Dye transfers within plants were common in all populations (mean ± 1 SE, 55 ± 3.0%), indicating that moths frequently deposit self‐pollen. Distance of dye transfers ranged from 0 to 50 m, and the mean number of flowering plants between the pollen donor and recipient was 5 (median = 0), suggesting that most pollen was transferred among near neighbors. A multilocus genetic estimate of outcrossing based on seedlings matured from open‐pollinated fruits at one site was 94 ± 6% (mean ± 1 SD). We discuss why moths frequently deposit self‐pollen to the detriment of their offspring and compare the yucca–yucca moth interaction with other obligate pollinator mutualisms in which neither pollinator nor plant benefit from self‐pollination.
Paternal inheritance of chloroplast DNA in interspecific hybrids in the genus Larrea (Zygophyllaceae)
Authors: Yang Tien Wei , Yang Yoko A. , Xiong Zhongguo
Published: April 2006

The mode of chloroplast DNA (cpDNA) inheritance was investigated in the genus Larrea (Zygophyllaceae) by polymerase chain reaction (PCR) amplification of cpDNA fragments using three pairs of chloroplast universal primers. A total of 20 F1s from interspecific crosses among five different taxa in the section Bifolium was examined. Twelve F1s were from six crosses between L. cuneifolia (4x) and L. divaricata (2x) (Peru or Argentina) or L. tridentata (2x or 4x). Eight F1s were from two sets of reciprocal crosses between L. divaricata (2x) (Argentina) and L. tridentata (2x). Length polymorphism was observed in all three regions of cpDNA that separated L. cuneifolia parents from L. divaricata and L. tridentata parents and in one of the three cpDNA regions that differentiated L. divaricata (Argentina) parents from L. tridentata (2x) parents. In each case, it was the paternal cpDNA marker that appeared in the F1 individuals. This was further confirmed by restriction fragment length polymorphism (RFLP) analysis of the amplified cpDNA fragments. Larrea may be the fifth genus reported in angiosperms with a paternal bias in cpDNA transmission. Possible mechanisms that may result in paternal cpDNA inheritance were briefly reviewed. Based on the observed uniparental paternal inheritance of cpDNA, restriction analysis of the three cpDNA regions and previous cytogenetic studies, L. divaricata was probably the maternal progenitor of L. cuneifolia.
Phylogenetic relationships in Taxodiaceae and Cupressaceae sensu stricto based on matK gene, chlL gene, trnL‐trnF IGS region, and trnL intron sequences
Authors: Kusumi Junko , Tsumura Yoshihiko , Yoshimaru Hiroshi , Tachida Hidenori
Published: April 2006

Nucleotide sequences from four chloroplast genes, the matK, chlL, intergenic spacer (IGS) region between trnL and trnF, and an intron of trnL, were determined from all species of Taxodiaceae and five species of Cupressaceae sensu stricto (s.s.). Phylogenetic trees were constructed using the maximum parsimony and the neighbor‐joining methods with Cunninghamia as an outgroup. These analyses provided greater resolution of relationships among genera and higher bootstrap supports for clades compared to previous analyses. Results indicate that Taiwania diverged first, and then Athrotaxis diverged from the remaining genera. Metasequoia, Sequoia, and Sequoiadendron form a clade. Taxodium and Glyptostrobus form a clade, which is the sister to Cryptomeria. Cupressaceae s.s. are derived from within Taxodiaceae, being the most closely related to the Cryptomeria/Taxodium/Glyptostrobus clade. These relationships are consistent with previous morphological groupings and the analyses of molecular data. In addition, we found acceleration of evolutionary rates in Cupressaceae s.s. Possible causes for the acceleration are discussed.
Germination and establishment of forest sedges (Carex, Cyperaceae): tests for home‐site advantage and effects of leaf litter
Authors: Vellend Mark , Lechowicz Martin J. , Waterway Marcia J.
Published: April 2006

We investigated aspects of germination and seedling establishment that might influence the distribution and diversity ofCarexspecies growing in the forest understory. We tested the ability ofCarex communisandC. platyphyllato germinate and establish at plots where adult individuals of one of these two species, or one of two otherCarexspecies (C. backiiandC. plantaginea), occurred in an old‐growth forest in southern Québec, Canada. We also tested for effects of leaf litter on germination and establishment of these sedges. From a series of experiments in the field and in a lath house, we found no evidence of home‐site advantage with respect to germination or seedling establishment. Leaf litter had a negative effect on germination and establishment. The results emphasize the importance of dispersal and colonization events in determining local diversity and distribution ofCarexspecies in upland forests. High frequency of occurrence ofC. communisat our study site may result from relatively wide dispersal provided by ants, and a suite of traits associated with ant dispersal in some understoryCarexspecies.
Effects of atmospheric CO2 enrichment on the growth and development of Hymenocallis littoralis (Amaryllidaceae) and the concentrations of several antineoplastic and antiviral constituents of its bulbs
Authors: Idso Sherwood B. , Kimball Bruce A. , Pettit George R. , Garner Lynnette C. , Pettit George R. , Backhaus Ralph A.
Published: April 2006

Two 2‐yr crops of tropical spider lily (Hymenocallis littoralis) plants were grown in field soil in clear‐plastic‐wall open‐top enclosures in the Sonoran Desert environment of central Arizona. Half of the plants were exposed to ambient air of 400 ppm atmospheric CO2 concentration and half of them were exposed to air of 700 ppm CO2. This 75% increase in the air's CO2 content resulted in a 48% increase in aboveground plant biomass and a 56% increase in belowground (bulb) biomass. It also increased the concentrations of five bulb constituents that have been demonstrated to possess anticancer and antiviral activities. Mean percentage increases in these concentrations were 6% for a two‐constituent (1:1) mixture of 7‐deoxynarciclasine and 7‐deoxy‐trans‐dihydronarciclasine, 8% for pancratistatin, 8% for trans‐dihydronarciclasine, and 28% for narciclasine, for a mean active ingredient percentage concentration increase of 12%. Combined with the 56% increase in bulb biomass, these percentage concentration increases resulted in a mean active ingredient increase of 75% for the 75% increase in the air's CO2 concentration used in our experiments.
Production and survivorship of the functional stolons of giant cutgrass, Zizaniopsis miliacea (Poaceae)
Authors: Fox Alison M. , Haller William T.
Published: April 2006

Giant cutgrass [Zizaniopsis miliacea], a tall emergent grass native to the southeastern United States, was studied in two Florida lakes. In Lake Seminole (15 176 ha) giant cutgrass forms large expanding stands, but in Lake Alice (9 ha) it is confined to a stable narrow fringe. By monitoring individual plants in Lake Seminole, it was found that an average decumbent flowering stem produced three flowers and ten nodes, 80% of which became rooted in the substrate. Such flowering stem development could potentially result in stand expansion of 2.2–2.7 m/yr, depending upon water levels and rates of node rooting. Once flowering stems became decumbent in Lake Alice, they typically broke, producing no more than two flowers with four nodes in a growing season. While still attached to the parent plant, few of these nodes were able to become rooted in the substrate, limiting the rate of stand expansion in Lake Alice. Sections of flowering stems bearing axillary shoots that were detached from the parent plant and free‐floating could become rooted on reaching shallow water and produce robust, new, flowering plants. This interesting mode of population dispersal and spread has important implications for the distribution and management of giant cutgrass.
Dissecting the causes of variation in intra‐inflorescence allocation in a sexually polymorphic species, Fragaria virginiana (Rosaceae)
Authors: Ashman Tia‐Lynn , Hitchens Michael S.
Published: April 2006

In this study we dissect the causes of variation in intra‐inflorescence allocation in a sexually polymorphic species, Fragaria virginiana. We separated out the effects of resource competition during flowering from those of inflorescence architecture, as well as identified the effects of sex morph and genotype. We found position‐based variation in petal length, ovule, pollen, and flower number to be influenced more by architecture than by our resource manipulations during flowering. We also found both genotype‐ and sex‐specific intra‐inflorescence patterns. Furthermore, our data indicate that the sex morph‐specific intra‐inflorescence patterns result from architectural modifications of the basic pattern. In fact, sex‐differential intra‐inflorescence patterns suggest that fitness through male and female function may be maximized by different resource distribution patterns within the inflorescence and may have been modified by past selection. Specifically, females invested heavily in ovules at positions where fruit set was most likely (primary and secondary), at the expense of flower number and allocation per flower at more distal positions. Whereas functional males invested minimally in ovules at all flower positions and produced the most abundantly flowered inflorescences, hermaphrodites, on the other hand, showed intermediate patterns, implying a compromise between sex functions. We suggest that consideration of intra‐inflorescence allocation and inflorescence architecture may reveal the mechanism underlying sexual dimorphism in flower allocation and number.