bluuebunny/crossref_metadata_2025 huggingface dataset:
POLLINATION BIOLOGY, SEED PRODUCTION, AND POPULATION STRUCTURE IN QUEEN‐OF‐THE‐PRAIRIE, FILIPENDULA RUBRA (ROSACEAE) AT BOTKIN FEN, MISSOURI
Authors: Aspinwall Nevin , Christian Terry
Published: January 2018

Queen‐of‐the‐prairie, Filipendula rubra (Rosaceae), is a perennial, rhizomatous herb restricted to calcareous fens, spring seeps, and wet prairies, and is distributed in the northcentral United States from Iowa to New York. Because of the scarcity of adequate habitat, F. rubra is a rare and endangered species in several states. At Botkin Fen and other fens in Missouri, F. rubra possesses limited sexual reproduction. A study was conducted to determine causal mechanisms of its limited seed production that may be barriers to establishing this rare and endangered species in other fens in Missouri. A genetic‐ecological hypothesis was supported. F. rubra was found to be self‐incompatible. At Botkin Fen, most inflorescences produced very few seeds because most (85.4%) belonged to a single clone. Pollinators (Lassioglossum sp.) had a high probability of transporting pollen with the same self‐incompatibility alleles. A few genetically different clones did produce significant quantities of seed. However, this seed, with its significant pool of genetic variability, was not recruited into the population. Apparently, competition from the dense sedges and grasses prevented the establishment of new seedlings.
VARIATION IN SEX ALLOCATION AND FLORAL MORPHOLOGY IN IPOMOPSIS AGGREGATA (POLEMONIACEAE)
Authors: Campbell Diane R.
Published: January 2018

Intrapopulational variation in biomass allocation to male vs. female function was quantified for the hermaphroditic plant Ipomopsis aggregata in terms applicable to sex allocation models. The proportions of flower biomass put into the corolla and calyx averaged 0.59 and 0.20 and were relatively constant across plants. The proportions in the stamens and pistil averaged 0.13 and 0.08, with considerable variation among plants. Phenotypic gender at the time of flowering ranged from 0.34 to 0.77 female. Pistil dry weight was correlated with stigma exsertion. Stamen weight was correlated with corolla width, which influences male pollination success, and was also correlated with anther position and pollen production. Female reproductive success as estimated by seeds per flower showed no detectable relationship with initial allocation of biomass at the time of flowering, but decreased in accelerating fashion with the proportion of final biomass including seeds that was allocated to male function.
DIAPHORODENDRACEAE, FAM. NOV. (LYCOPSIDA: CARBONIFEROUS): SYSTEMATICS AND EVOLUTIONARY RELATIONSHIPS OF DIAPHORODENDRON AND SYNCHYSIDENDRON, GEN. NOV.
Authors: DiMichele William A. , Bateman Richard M.
Published: January 2018

Synchysidendron, gen. nov., is segregated from Diaphorodendron DiMichele emend. Both genera are determinate, rhizomorphic, arborescent lycopsids that share identical reproductive organs but differ radically in growth architecture and consequently in the timing of reproduction. Cones in Synchysidendron (two species) are borne on late‐formed crown branches; in Diaphorodendron (three species) cones are borne on deciduous lateral branches, produced over much of the life of the tree. The two genera also differ in several characteristics of the stele and periderm. We hypothesize that Diaphorodendron gave rise to Synchysidendron within their shared Late Carboniferous coal‐swamp habitat, by heterochronic suppression of lateral branching during ontogeny. Together, these genera form a highly apomorphic clade, here recognized as the new family Diaphorodendraceae, that is distinguished primarily by siphonostelic axes, a bifacial periderm, distinctive megasporangia, and gulate megaspores.
ENVIRONMENTAL INFLUENCES ON NECTAR PRODUCTION IN MILKWEEDS (ASCLEPIAS SYRIACA AND A. EXALTATA)
Authors: Wyatt Robert , Broyles Steven B. , Derda Gregory S.
Published: January 2018

Cross‐comparisons of nectar production data are complicated because different workers use bags made of various materials to exclude animal visitors. Using clonal populations of Asclepias syriaca and A. exaltata in northern Virginia, we carefully measured the effects of four bagging treatments (bridal veil, pellon, paper, plastic) on microenvironment (temperature, relative humidity) and nectar production (volume, concentration, sucrose amount) over the course of a day. In general, bridal veil bags changed the microenvironment least relative to unbagged controls. Plastic bags resulted in higher temperatures and constantly higher relative humidities. Temperature and relative humidity were also elevated, though less dramatically, in paper and pellon bags. Under more humid conditions, flowers contained larger volumes of more dilute nectar. Therefore, researchers who wish to obtain nectar production data that reflect natural field conditions should use bridal veil, or a material with similar properties, to bag inflorescences. We also performed a watering experiment, involving the addition of the equivalent of a 10‐cm rain to the A. syriaca plot. After watering, nectar volumes and sucrose amounts were increased approximately twofold.
RECURRENT FORMATION AND POLYPHYLY OF NORDIC POLYPLOIDS IN DRABA (BRASSICACEAE)
Authors: Brochmann Christian , Soltis Pamela S. , Soltis Douglas E.
Published: January 2018

Draba (Brassicaceae) is well known for its taxonomic complexity in arctic and alpine floras, and the polyploids in particular present vexing taxonomic problems. It has been suggested that polyploids in Draba may have formed recurrently from different populations of the parental species (polytopy), and it is also possible that a given taxonomic species may actually comprise several polyploid races, each originating from different progenitor species (polyphyly). To unravel the taxonomic complexity of polyploid Draba in the Nordic area, we investigated three of the most morphologically variable species and their possible progenitors using enzyme electrophoresis and restriction site analysis of chloroplast DNA (cpDNA) and nuclear ribosomal RNA genes (rDNA): D. norvegica (6x), D. lactea (6x), and D. corymbosa (16x). Electrophoretic analyses of progeny showed high levels of fixed heterozygosity in all three polyploids, demonstrating that all are genetic alloploids. Electrophoretic and rDNA data indicate that polytopic and/or polyphyletic origins have contributed to the complexity of these polyploids. However, a lack of cpDNA variation among the species limited the usefulness of this molecule for analysis of polyploid origins. The considerable electrophoretic variation observed in D. norvegica necessitates a minimum of three and probably 13 independent origins. Electrophoretic and rDNA data suggest that D. lactea and D. corymbosa are polyphyletic polyploids. Crossing data also support that D. corymbosa is polyphyletic. Given the widespread geographic distributions of these species and their possible progenitors, and that the populations analyzed represent only a small fraction of their geographic distributions, it is likely that these species have formed numerous times in different areas. As more molecular analyses of polyploids are completed, the data continue to suggest that multiple origins of polyploids are the rule rather than the exception.
SYSTEMATIC INFERENCES FROM VARIATION IN ISOZYME PROFILES OF ARCTIC AND ALPINE CESPITOSE FESTUCA (POACEAE)
Authors: Aiken Susan G. , Consaul Laurie L. , Davis Jerrold I. , Manos Paul S.
Published: January 2018

Variation in isozyme patterns was used to assess species boundaries in North American arctic and alpine representatives of the Festuca ovina L. complex. Isozyme profiles, in combination with chromosome number, delimit four discrete entities within the complex: F. brevissima Jurtzev (diploid); F. aggr. auriculata Drobov (diploid); F. brachyphylla Schultes (hexaploid); and tetraploid populations corresponding in morphology to F. baffinensis Polunin (arctic Canada) and F. minutiflora Rydberg (alpine United States). Although no fixed difference was detected between isozyme profiles of the latter two taxa, they are morphologically distinct. Thus variation in isozymes, morphology, and chromosome number delimits five taxa within the F. ovina complex in North America. Some alleles observed in the polyploid taxa were not detected among the diploids, and some observed in F. brachyphylla, the hexaploid taxon, were not detected in either the diploid or the tetraploid species. One possible explanation for these occurrences is that the North American polyploids originated in Eurasia, where many other potential diploid and tetraploid progenitors occur.
CYTOLOGICAL ANALYSIS OF ANTHURIUM ANDRAEANUM (ARACEAE), ITS RELATED TAXA AND THEIR HYBRIDS
Authors: Marutani Mari , Sheffer Richard D. , Kamemoto H.
Published: January 2018

Karyotypes and meiotic configurations of Anthurium andraeanum and closely related taxa were analyzed. The karyotypes of A. andraeanum, A. caperatum, A. formosum, A. kamemotoanum, A. lindenianum, A. roseospadix, A. cf. sanctifidense, A. subsignatum, A. garagaranum, and an unidentified Anthurium sp. commonly consisted of four large metacentric or submetacentric chromosomes, two fairly large acrocentric chromosomes, two satellite chromosomes, and 22 smaller chromosomes. Variation in the karyotypes of A. nymphaeifolium and A. ochranthum suggested chromosomal rearrangement in the genus. All taxa showed 15 pairs of chromosomes at prometaphase I of meiosis in pollen mother cells. Four large chromosomes appeared as ring bivalents, and the rest of the chromosomes appeared as either ring or rod bivalents. Regular bivalent formation at prometaphase I of meiosis in pollen mother cells of species hybrids suggested close genomic relationships among parental taxa. On the other hand, reduction of pollen fertility estimated by pollen stainability in those hybrids suggested genetic divergence of species.
PROLAMIN AND IMMUNOLOGICAL STUDIES IN THE POACEAE. III. SUBFAMILY CHLORIDOIDEAE
Authors: Hilu K. W. , Esen A.
Published: January 2018

Prolamin size variation and structural similarities were used as molecular characters to address questions pertaining to tribal structure and phylogenetic origin of the Chloridoideae. Prolamin polypeptides were resolved by SDS‐PAGE (sodium dodecyl sulphate polyacrylamide gel electrophoresis), and the immunological cross‐reactivities were measured by ELISA (enzyme‐linked immunosorbent assay) and immunoblotting. Thirty‐three species were examined from 24 genera belonging to six chloridoid tribes and three outgroup subfamilies (Arundinoideae, Panicoideae, and Pooideae). The study supports the inclusion of the Cynodonteae, Eragrosteae, and Sporoboleae under one tribe. Members of the Pappophoreae and Spartineae appeared as distinct lineages. The results suggest a strong evolutionary relationship between the Chloridoideae and Arundinoideae.
EXINE INITIATION AND SUBSTRUCTURE IN POLLEN OF CAESALPINIA JAPONICA (LEGUMINOSAE: CAESALPINIOIDEAE)
Authors: Takahashi Masamichi
Published: January 2018

Exine development in pollen of Caesalpinia japonica was studied using high resolution scanning electron microscopy, with attention to the initial developmental process of protectum formation and composition. The protectum is originated on the protuberant sites of the invaginated plasma membrane during the early tetrad stage. The present study shows that the initial protectum is composed of irregularly oriented fibrous threads. The fibrous threads accumulate and form a network on the plasma membrane. Granules 10–20 nm in diameter gradually aggregate within the network of fibrous threads during the tetrad stage. Subsequently the fibrous threads are almost masked by the granules. The developing protectum has a coarse texture within the callosic tetrad envelope. At the free microspore stage the granular protectum becomes homogeneous. The present study suggests that the protectum consists of an association of fibrous threads and granules. The fibrous threads may function as receptors and/or the skeleton of the developing exine.
PHYSICAL AND ULTRASTRUCTURAL BASIS OF BLUE LEAF IRIDESCENCE IN TWO NEOTROPICAL FERNS
Authors: Graham Rita M. , Lee David W. , Norstog Knut
Published: January 2018

Iridescent blue leaf coloration in two neotropical ferns, Danaea nodosa (L.) Sm. (Marattiaceae) and Trichomanes elegans L. C. Rich. (Hymenophyllaceae), is caused by thin film constructive interference. The ultrastructural basis for the film in D. nodosa is multiple layers of cellulose microfibrils in the adaxial cell walls of the adaxial epidermis. The apparent helicoidal arrangement of the fibrils is analogous to similar color production in arthropods. In T. elegans the blue‐green coloration is caused by the remarkably uniform thickness and arrangement of grana in specialized chloroplasts adjacent to the adaxial wall of the adaxial epidermis. The selective advantage of this color production, if any, is unknown but apparently different from that previously studied in Selaginella.
FLOWER DEVELOPMENT IN DIOECIOUS SPINACIA OLERACEA (CHENOPODIACEAE)
Authors: Sherry Rebecca A. , Eckard Kathleen J. , Lord Elizabeth M.
Published: January 2018

Spinacia oleracea (Chenopodiaceae) is a potential model system for studies of mechanisms of sex expression and environmental influences on gender in dioecious species. Development of the male and female flowers and inflorescences of spinach were studied to determine when the two sex types can be distinguished. We found that female inflorescence apices are significantly larger than those of the male. Flower primordia are similar in size prior to perianth initiation, but the male primordia develop at a faster rate. Another distinguishing feature at this early stage is the larger bract subtending the female primordium. The two flower types become readily distinguishable when the perianth initiates. Male flowers produce four sepals and four stamens in a spiral pattern in close succession. Female flowers produce two alternate perianth parts that enlarge somewhat before the gynoecium becomes visible. There are no traces of gynoecia in male flowers or of stamens in female flowers. We propose that plant sex type is determined before inflorescence development, prior to or at evocation.
CYTOLOGICAL STUDIES IN LACCARIA (AGARICALES). I. MEIOSIS AND POSTMEIOTIC MITOSIS
Authors: Mueller George J. , Mueller Gregory M. , Shih Lu‐hsi , Ammirati Joe F.
Published: January 2018

In the genus Laccaria, basidial formation, dikaryotic basidia, karyogamy, and meiosis were generally similar to structures and phenomena reported for other Agaricales. The haploid nuclei of dikaryotic basidia resided side by side in the basidium prior to karyogamy. Following karyogamy a single nucleolus was observed in L. montana (four‐spored species); several nucleoli remained in the nucleus of L. tortilis (two‐spored species). The haploid number of chromosomes for L. montana appeared to be n = 9. Postmeiotic mitosis typically occurred in the basidiospores resulting in binucleate basidiospores for four‐spored species and quadrinucleate basidiospores for two‐spored species. Postmeiotic mitosis sometimes occurred in the sterigmata and basidia proper. In instances where postmeiotic mitosis occurred in basidia, mature basidiospores were not formed and the basidia were collapsed, and contained up to eight nuclei.
THE CONNECTIVE BASE OF CIRSIUM HORRIDULUM (ASTERACEAE): DESCRIPTION AND COMPARISON WITH THE VISCOELASTIC FILAMENT
Authors: Pesacreta Thomas C. , Sullivan Victoria I. , Hasenstein Karl H.
Published: January 2018

Structural, autofluorescent, and mechanical characteristics show that the so‐called “collar” of the stamen is an elongated basal portion of the connective in Cirsium horridulum. The connective base/filament boundary is precisely demarcated by epidermal cells with thick, autofluorescent walls. In the region of the connective base near the anther lobes, the autofluorescence is less intense and the cells are longer, but wall thickness does not decrease. The autofluorescence can be assayed in fresh, frozen, or rehydrated materials, and is resistant to boiling in water and to acetone. Additional features delineate the connective base from the filament. The abaxial and lateral portions of the connective base surface are relatively flat due to the underlying thick secondary walls. Ultrathin sections taken at various points along the length of the connective base and the filament show that cuticle thickness gradually increases from approximately 30 nm in the connective base to 450 nm in the filament. The connective base/filament junction appears to be a weak mechanical link within the stamen. These data establish several new connective base characteristics in Cirsium and define the connective base/filament boundary.
QUANTITATIVE COMPARISON OF FLORAL DEVELOPMENT IN VERONICA CHAMAEDRYS AND VERONICASTRUM VIRGINICUM (SCROPHULARIACEAE)
Authors: Kampny C. M. , Dickinson T. A. , Dengler N. G.
Published: January 2018

Development in Veronica and Veronicastrum was studied to elucidate the growth patterns responsible for differences between their mature flowers. Nineteen floral dimensions were measured on buds from initiation to anthesis, and representative stages were recorded with the scanning electron microscope. Bivariate plots indicate the heterochronic changes responsible for the derived flower form of Veronica. The growth patterns of the gynoecium and androecium were little changed. The calyx of Veronica showed slower size increase at the early stages, but continued to grow after that of Veronicastrum had stopped. The most striking change occurred in the corolla lobes of Veronica, where growth was retarded until the beginning of style formation, but afterward was accelerated relative to that of Veronicastrum. The corolla tube of Veronica remained short due to a later onset of growth and slower enlargement later in development. Multigroup principal components analysis (M‐PCA) was used to summarize the measurements. The distribution of points along M‐PC 1 describes size increase during floral development. Along M‐PC 2 the trajectories of the two taxa diverge after the beginning of style growth, while along M‐PC 3 they differ from the earliest stages on, corroborating differences observed with the scanning electron microscope. M‐PCA can thus be used to portray differences in patterns of floral development, facilitating simultaneous quantitative comparisons of two or more taxa.
A STUDY OF SPATIAL FEATURES OF CLONES IN A POPULATION OF BRACKEN FERN, PTERIDIUM AQUILINUM (DENNSTAEDTIACEAE)
Authors: Parks James C. , Werth Charles R.
Published: January 2018

Allozymes were used to study the spatial attributes of clones (genets) comprising a population of Pteridium aquilinum (L.) Kuhn var. latiusculum (Desv.) Underw. ex Heller (bracken fern) in the Appalachian Mountains of Virginia. Ramets (individual leaves) were sampled at intervals of 165 m (or less in some cases) and genotyped for six polymorphic isozyme loci to produce a map depicting the spatial patterning of genets. Forty‐five distinct genotypes were detected, 14 of which were sampled more than once, five of these more than four times. Genotype proportions at all loci except Pgm‐1 conformed to Hardy‐Weinberg expectations. Estimation of allele frequencies in the population used a “round‐robin” approach that removed any upward bias for rare alleles that distinguish genets. Based on these allele frequencies, the probability that each genotype could arise independently and be sampled was calculated. Some genotypes represented by widely separated ramets had very low probabilities of re‐encounter, documenting fragmentation of widespread genets. Coarse‐scale mapping indicated a population consisting of many small genets and a few very large ones (up to 1,015 m across). The larger genets tended to be irregular in shape, fragmented, and overlapping. Fine scale mapping of individual fronds in spatially discrete patches of ramets revealed extensive intergrowth of genets, indicating that P. aquilinum exhibits a “guerrilla‐type” clonal morphology.
CONTROL OF SEX RATIOS IN HAPLOID POPULATIONS OF THE MOSS, CERATODON PURPUREUS
Authors: Shaw A. Jonathan , Gaughan James F.
Published: January 2018

Female biased sex ratios occur in a number of unrelated mosses. Such ratios refer to the relative numbers of male and female gametophytes in moss populations and are therefore more comparable to the numbers of pollen grains and ovules in populations of seed plants than to the numbers of male (microsporangiate) and female (megasporangiate) sporophytes. A survey of 11 populations of the moss, Ceratodon purpureus, showed that sex ratios are heterogeneous, but that female biases occur in more than half the populations. One hundred and sixty single spore isolates representing 40 sporophytes from one population demonstrated that female gametophytes outnumbered males by a ratio of 3:2 at the time of germination. Female gametophytic clones formed significantly more biomass than male clones, and individual female shoots were more robust. Male clones, however, produced more numerous stems. These sexually dimorphic traits may be related to life history differences between male and female gametophytes since females must provide nutritional support to the “parasitic” sporophyte generation, a burden that males do not share.
RESURRECTION OF THE GENUS ENDOLEPIS AND CLARIFICATION OF ATRIPLEX PHYLLOSTEGIA (CHENOPODIACEAE)
Authors: Stutz Howard C. , Chu Ge‐lin , Sanderson Stewart C.
Published: January 2018

The genus Endolepis was first described by Torrey in 1860 with E. suckleyi (E. dioica [Nutt.] Standley) as the only species, noting that it differed from species of Atriplex by the presence of perianth parts in the female flowers. Later, Standley described two additional species: E. covillei and E. monilifera. H. M. Hall and Clements merged Endolepis with Atriplex because they thought that the presence of perianth parts in female flowers was variable in Atriplex phyllostegia. It is now clear that this observation was erroneous; A. phyllostegia never has perianth parts in its female flowers. The plants that they examined that had female flowers with perianth parts were specimens of Endolepis covillei; only those with female flowers devoid of perianth parts were specimens of Atriplex phyllostegia. These two taxa differ by several other major attributes including differences in leaf shape, leaf anatomy, fruiting‐bract size and shape, fruiting‐bract appendages, and flowering habit, and therefore justify taxonomic separation. Also, because the presence of perianth parts in bracteolate female flowers is a rare attribute in the tribe Atripliceae, consistently absent in Atriplex, but always present in Endolepis, the retention of the genus Endolepis, separate from Atriplex, is deemed warranted. We propose that the genus Endolepis comprise two species, E. dioica and E. covillei. The species named E. monilifera by Standley is based on a specimen of Atriplex serenana Nels.
CHROMOSOME NUMBERS OF CAMPANULACEAE. III. REVIEW AND INTEGRATION OF DATA FOR SUBFAMILY LOBELIOIDEAE
Authors: Lammers Thomas G.
Published: January 2018

Chromosome numbers are now known for 153 species in 21 genera of Lobelioideae (Campanulaceae); this represents almost 13% of the species and 70% of the genera in the subfamily. Numbers reported are n = 6, 7, 8, 9, 10, 11, 12, 13, 14, 19, 21, 35, 70. The subfamily as a whole has x = 7; the best documented exception is Downingia and its allies with x = 11. Only four genera show interspecific variation in chromosome number: Downingia (n = 6, 8, 9, 10, 11, 12); Lobelia (n = 6, 7, 9, 12, 13, 14, 19, 21); Pralia (n = 6, 7, 13, 14, 21, 35, 70); and Solenopsis (n = 11, 14). Intraspecific variation occurs in 13 species, with as many as four different cytotypes in one species. The herbaceous members of the subfamily as a group are quite variable, showing the entire range of chromosome numbers, including numerous dysploids, but are predominantly diploid. The woody species, by contrast, are much less variable; nearly all of the species are tetraploid, with only a few diploids and hexaploids and no dysploid numbers known. These data support the hypothesis that woodiness is apomorphic within the subfamily. A general trend of higher chromosome numbers at higher latitudes and higher elevations is evident within the subfamily. The chromosome number of Apetahia raiateensis (n = 14) is reported here for the first time, on the basis of a count made about 30 years ago by Peter Raven.
GENETIC EVIDENCE FOR TRACE PATERNAL TRANSMISSION OF PLASTIDS IN LIRIODENDRON AND MAGNOLIA (MAGNOLIACEAE)
Authors: Sewell Mitchell M. , Qiu Yin‐Long , Parks Clifford R. , Chase Mark W.
Published: January 2018

Transmission of plastids in Liriodendron and Magnolia was studied by examining inheritance of plastid DNA markers in interspecific crosses. In congeneric hybrids of Liriodendron and Magnolia, 2.9% and 11.1% of progeny, respectively, exhibited uniparental paternal transmission of plastids. This departure from strict uniparental maternal transmission of plastids indicates that mechanisms for the elimination of paternal plastids are not 100% efficient and that any proposed model for plastid transmission must account for a continuum of variation. Our results, and other results reviewed here, show a discrepancy with data obtained by cytological observations and point to the need of confirming the mode of plastid inheritance by genetic analysis. In addition, if paternal plastids are occasionally inherited, intensive sampling of plastid DNA in a putative hybrid population could identify both parents of hybrids and thereby aid in the phylogenetic reconstruction of hybrid zones.
EMBRYOLOGY AND KARYOMORPHOLOGY OF LACTORIDACEAE
Authors: Tobe Hiroshi , Stuessy Tod F. , Raven Peter H. , Oginuma Kazuo
Published: January 2018

The embryology and karyomorphology of Lactoris fernandeziana, representing the monotypic family Lactoridaceae, were studied in an attempt to clarify its relationships. Embryologically, Lactoris is characterized by a combination of many generalized, plesiomorphic features, which are mostly shared with Magnoliales and partly shared with Laurales and Piperales, and some specialized, apomorphic features including a tenuinucellate ovule, a small nucellus with early disintegrating nucellar tissue, a nonmultiplicative outer integument, an endothelium, and haustorial endosperm. Karyomorphologically Lactoris is confirmed to have 2n = 40 at metaphase, probably as a tetraploid of x = 10, and more or less distinctive features at inter‐ and prophase. Comparisons based on its embryological and karyomorphological features suggest that Lactoris is not closely related to any other family. Based on evidence from various sources, we hypothesize that an evolutionary line was derived from a common ancestor with Magnoliales, and then diverged into Lactoris, which retains many primitive magnolialean features, and Piperales (and possibly other groups) with more specialized characteristics. Lactoris seems best placed in its own order, Lactoridales, near Piperales.
DEVELOPMENTAL PLASTICITY, GENETIC VARIATION, AND THE EVOLUTION OF ANDROMONOECY IN SOLANUM HIRTUM (SOLANACEAE)
Authors: Diggle Pamela K.
Published: January 2018

Studies of andromonoecious species have shown that sex expression (proportions of hermaphrodite and staminate flowers) is quite variable. It is not known, however, whether this variation is due to variation among individuals for genetically fixed patterns of allocation to staminate and hermaphrodite flowers (population level variation) and/or to developmental plasticity of individuals in a heterogeneous environment (organismal level variation). Distinguishing between these two levels of variation is important for understanding the evolution of andromonoecy. This study investigates levels of variation in sex expression in the andromonoecious Solanum hirlum. Sex expression in this species is shown to be plastic among individuals of the same genotype (organismal level variation) and determined, in part, by the resource status of the individual. Among the genotypes examined there is also genetic variation for developmental plasticity. Thus, developmental plasticity can potentially respond to selection, and the evolution of this developmental system may have been instrumental in the establishment and maintenance of andromonoecy in S. hirtum.
Early primary succession on a barren volcanic plain at Mount St. Helens, Washington
Authors: Moral Roger del , Wood David M.
Published: January 2018

The invasion pattern on a barren plain on the eastern flank of Mount St. Helens, Washington, devastated by the 1980 volcanic eruption was monitored between 1988 and 1992. All vascular plants on a grid consisting of 400 contiguous 100‐square‐meter quadrats were recorded with a cover score. The substrate was initially homogeneous, but significant heterogeneity had developed by 1988. Vascular plant species richness increased from 24 in 1988 to 41 in 1992. Mean species richness per quadrat increased from 0.44 to 5.71, mean cover increased from 0.04% to 0.51%, and mean diversity index (H') increased from 0.08 to 1.56. A variance/mean test of species richness pattern showed that invasion occurred sporadically since plots tended to have either several or no species. By 1992, mean species richness was more evenly distributed. Most seedlings continue to result from long‐distance dispersal, but reproductive colonies of species are developing. Seedling distributions are controlled by microsites. Eleven common species strongly and similarly preferred safe‐sites created by small rocks, undulations, or rills. However, many apparent safe‐sites are empty, suggesting that seeds are scarce and that even the most favorable microsites are marginal. The niches of these species seem to overlap broadly. The Plains of Abraham is in the earliest stage of primary succession. The detailed invasion pattern permitted us to distinguish species still dependent on immigration from those now locally established. Pronounced microsite preferences emphasize that physical amelioration (e.g., nutrient input and erosion) must occur before further succession can commence. We have observed the early stages of succession where an inhospitable site is gradually and heterogeneously changed into a habitat where safe‐sites do not limit succession, but where stochastic factors remain important.
Pollinators of tropical dioecious angiosperms
Authors: Renner Susanne S. , Feil Jan Peter
Published: January 2018

Dioecy is frequent in tropical forests. It has been suggested that small, unspecialized pollinators are among the factors responsible for gender separation in this habitat. The underlying assumption is that poor fliers and/or communal foragers frequently effect selfing which in turn, given sufficiently severe inbreeding depression, should favor the establishment of dioecy. At least 10% of the genera of the angiosperms includes dioecious species; in tropical flowering plants, however, pollinators are reliably known only in a few species. Whereas temperate dioecious species commonly are wind‐ or water‐pollinated, anemophily is less important in tropical forests, but occurs in at least 30 dioecious genera. Our survey of tropical dioecious zoophilous species in 29 genera (in 21 families) for which detailed pollination information is available shows that these species have specialized flowers adapted to specific pollinators rather than generalized flowers suitable for diverse insects. Known pollinators include solitary and eusocial bees, beetles, moths, flies, wasps (including fig wasps), and rarely bats and birds, and cover a wide range in animal size and locomotive capabilities. Floral rewards comprise pollen, nectar, stylar mucilage, nutritious tissues, brood‐places, and resins. About a third of the species offer no reward in the female morph, pollination by deceit apparently being common. Our data thus do not support the hypothesis that there is a broad correlation between a dioecious breeding system and unspecialized pollination, although such a correlation may be found in certain taxa. Specialized plant‐pollinator relationships seem as critical in dioecious plants in tropical forests, where individuals often grow far apart, as they are in tropical plants with other breeding systems.
Bidirectional cytoplasmic and nuclear introgression in the New World cottons Gossypium barbadense and G. Hirsutum (Malvaceae)
Authors: Brubaker Curt L. , Koontz Jason A. , Wendel Jonathan F.
Published: January 2018

Patterns of interspecific cytoplasmic (plastid and mitochondrial) and nuclear introgression are typically asymmetrical: cytoplasmic gene flow or “capture” is frequently observed without evidence of nuclear introgression. In contrast, nuclear introgression without concomitant cytoplasmic introgression has rarely been demonstrated. Gossypium barbadense L. and G. hirsutum L. have large indigenous ranges in the New World semiarid tropics, with an extensive area of sympatry in the Caribbean and Central America. Numerous accessions of both species were surveyed for diagnostic cpDNA restriction sites. These data, in conjunction with previous information on nuclear markers, lead to several conclusions: 1) introgression between G. hirsutum and G. barbadense is bidirectional for both nuclear and cytoplasmic genes; 2) patterns of introgression between the two species are not symmetrical—in G. barbadense, introgression of G. hirsutum alleles is largely restricted to modem cultivars and is uncommon in areas of sympatry; in contrast, introgression of G. barbadense alleles into G. hirsutum is relatively common in areas of sympatry and is rare in modem cultivars; 3) nuclear introgression is geographically more widespread and more frequently detected than cytoplasmic introgression. Several mechanisms may underlie the differential patterns of cytoplasmic and nuclear gene flow observed, including differential fitness of infraspecific and interspecific cytonuclear combinations and selection against female function in interspecific backcrosses. Possible explanations for the observed asymmetrical patterns of introgression include differences in population sizes combined with phenological differences that bias interspecific pollen transfer.
Phenotypic integration and plastic correlations in Phlox drummondii (Polemoniaceae)
Authors: Waitt D. E. , Levin D. A.
Published: January 2018

Clones from two populations of Phlox drummondii were grown in three different nutrient environments to determine the extent to which the overall level and pattern of correlation among traits within an environment changes across environments. With one exception, the level of phenotypic correlation in both populations was the same across environments. Plants from Lexington, Texas exhibited a significantly lower level of phenotypic correlation when grown at a high nutrient concentration. The two populations did not differ from one another in their levels of phenotypic correlation when compared within environments. The pattern of correlation was homogenous both within populations across environments and among populations within environments. Tests of a priori hypotheses regarding the associations among functionally or developmentally related traits suggest that the correlations among traits are higher in traits that share a common function or developmental origin. We also compared the level and pattern of plasticity correlations among populations for three different components of the plastic response. We found that the level and pattern of plastic correlation for the average, linear, and nonlinear components of the plastic response did not differ among the two populations. With only one exception, the relationships among the plastic responses of different traits fit our model of functional and developmental integration. The results from our analyses of phenotypic and plastic correlations support the hypothesis that plastic correlations determine the extent to which phenotypic correlations are environment‐dependent.
Failure to establish a functional shoot meristem may be a cause of conversion failure in somatic embryos of Daucus carota (Apiaceae)
Authors: Nickle Todd C. , Yeung Edward C.
Published: January 2018

A carrot cell culture line was shown to be highly embryogenic, but plantlet recovery (conversion) was low (about 14%). The majority of somatic embryos that did not convert showed pronounced vacuolation in the apical notch, leading to their inability to form primary leaves and thereby convert. Comparisons of developing meristems in the shoot apical notch of converting somatic and zygotic embryos revealed similarities in cytoplasmic density and meristem organization between the two populations. Abscisic acid (ABA) was shown to significantly increase conversion in somatic embryos of globular, torpedo, and preplantlet stages (62%, 62.5% and 40%, respectively). Somatic embryos that were treated with 50 μM ABA showed retention of the highly cytoplasmic cells in the apical notch. Histological analysis showed a resemblance between shoot apices of converting somatic embryos and ABA‐treated somatic embryos. ABA may be an induction agent for meristematic organization, or perhaps may cause cells of the apical notch to extend competence for determination as meristematic cells.
Relationship between flowering time and fruit set of the entomophilous alpine shrub, Rhododendron aureum (Ericaceae), inhabiting snow patches
Authors: Kudo Gaku
Published: January 2018

Flowering phenology, fruit set, and pollinator frequency of the ericaceous alpine dwarf shrub, Rhododendron aureum, were compared among three quadrats arranged along a snowmelt gradient on a slope. Bagging and self‐pollination experiments showed that R. aureum was physiologically self‐compatible, but pollinator visitation highly enhanced fruit set. Depending on the lateness of snowmelt, flowering time varied from mid‐June to late July among quadrats. Pollinator visitation increased as the flowering season progressed, and fruit set was significantly higher in the quadrat with latest snowmelt. Emasculation experiments suggested that later flowering might promote cross‐pollination. Thus, later flowering was advantageous for effective pollination. On the other hand, later‐flowering plants often failed to set fruits because of the onset of autumn frost and snow before fruit maturation.
Morphometric variation in oaks of the Apostle Islands in Wisconsin: evidence of hybridization betweenQuercus rubraandQ. ellipsoidalis(Fagaceae)
Authors: Jensen Richard J. , Hokanson Stan C. , Isebrands J. G. , Hancock James F.
Published: January 2018

The Apostle Islands in Lake Superior are populated by trees that are clearly related toQuercus rubraL. However, several islands have trees with morphological characteristics suggestive of hybridization withQ. ellipsoidalisHill. Leaf specimens were collected from trees in five locations: the outermost island, an intermediate island, the nearest‐shore island, the northeast shoreline, and an inland forest about 24 km from the shoreline. Seventeen landmarks were digitized for two to five leaves per tree. These landmarks were used to generate nine linear characters and three angles. These characters, along with the number of bristle tips per leaf, were used in various combinations for several principal component analyses. In addition, the landmark configurations were examined using rotational‐fit methods. The patterns observed in both types of analysis indicate phenotypic variation coincident with a line connecting the two most distant sample sites. The location nearest the geographic center of this line is also nearest the center of the two‐dimensional view of phenotypic variation. Trees at each site illustrate a distinctive pattern in the rotational‐fit analyses, and patterns of co‐variation in the morphometric characters are different for each site. The observed morphometric variation is consistent with the hypothesis that there is hybridization between these two species, most likely in the form of introgression fromQ. ellipsoidalisintoQ. rubra.
Seed ecology of dust seeds in situ: a new study technique and its application in terrestrial orchids
Authors: Rasmussen Hanne N. , Whigham Dennis F.
Published: January 2018

A method is described by which seeds of terrestrial orchids are sown and retrieved in the field under almost natural conditions. For the first time it is possible to conduct a quantitative study of orchid germination in situ and observe seasonal growth and mortality of seedlings. The technique has also enabled us to investigate the relation between the site where the seeds are sown, the availability of an appropriate fungus to infect the seeds, and seedling establishment in the soil. Five local species were studied. Corallorhiza odontorhiza, Goodyera pubescens, and Galearis spectabilis all began to germinate in May–June, after 23‐30 weeks in the soil. These species differed in their dependency on infection at germination time, but none of the seedlings developed beyond the point of rupturing the testa except when infected. Seeds of Liparis lilifolia and Tipularia discolor did not germinate within the first 12 months of the experiment. The implications and potential uses of this field sowing technique for further studies and for other kinds of minute seeds are discussed.
Effects of environmental variation on fitness of singly and multiply sired progenies of Raphanus sativus (Brassicaceae)
Authors: Karron Jeffrey D. , Marshall Diane L.
Published: January 2018

Two hypotheses have been proposed concerning possible fitness advantages of multiple paternity. According to the Elbow Room hypothesis, the magnitude of resource partitioning is positively correlated with the genetic diversity of competitors. This leads to the prediction that the mean fitness of competing half‐siblings will exceed the mean fitness of competing full‐siblings. The Lottery hypothesis suggests that in a patchy environment a genetically diverse sibship increases the probability that a mother will produce winning phenotypes for each of several different microsites. Both hypotheses were tested in a greenhouse experiment with wild radish, Raphanus sativus. Progeny derived from factorial crosses were raised in competition as full‐ or half‐siblings. To simulate environmental variation, the experiment was replicated across a gradient of nutrient concentrations. After 9 weeks, the aboveground biomass of all plants was harvested and oven‐dried. Although dry weights were strongly influenced by nutrient level, within nutrient classes there were no significant differences in the mean dry weight of full‐ and half‐sib competitors. Thus, there was no evidence for the Elbow Room hypothesis. In addition, there were no significant differences in numbers of winning phenotypes in the two competition regimes. Therefore, there was also no support for the Lottery hypothesis. Although competition regime did not influence the mean fitness of competing progeny, it significantly affected variation in dry weight of seedlings within pots. Higher coefficients of variation in half‐sib pots suggest that interference competition may be greater in genetically diverse sibships.
Speciation in lichens of the Ramalin a siliquosa complex (Ascomycotina, Ramalinaceae): gene flow and reproductive isolation
Authors: Culberson William Louis , Culberson Chicita F. , Johnson Anita
Published: January 2018

The lichens of the rock‐inhabiting Ramalina siliquosa complex of maritime cliffs of western Europe are differentiated into six chemotypes characterized by a replacement series of β‐orcinol depsidones. These chemotypes are sharply zoned from the most sheltered to the most exposed positions in the supralittoral zone. Since artificial crosses in lichens are impossible, the breeding system was investigated by an analysis of the progeny of matemals from nature—some growing in pure zones and others growing intermixed with different chemotypes where zones overlap. Overall, the chemotypes are highly reproductively isolated, the progeny tending to be chemically identical to their respective maternal individuals. Only one pair of chemotypes appears to represent a clear polymorphism; the remainder are apparently ecologically differentiated sibling species. Two chemotypes, which interbreed where their zones overlap, are apparently kept distinct by strong selection against unadapted sporelings in the “wrong” niche. Spermatia function over only short distances, also contributing to the reproductive isolation.
The mating system and relative performance of selfed and outcrossed progeny inArabis fecunda (Brassicaceae)
Authors: Hamilton Matthew B. , Mitchell‐Olds Thomas
Published: January 2018

We estimated rates of self‐fertilization and inbreeding depression in the hermaphroditic perennial Arabis fecunda. Crosses were made on mesh‐bagged wild plants, yielding 12 plants producing self‐, outcross‐, and naturally fertilized seeds that were then grown in a greenhouse. Analysis of variance indicated aboveground dry weight at 160 days differed among pollination treatments, but mean seed weight, number of seeds per fruit, and days to germination did not. For dry weight, selfed progeny have 9.4% reduction and naturally pollinated progeny a 3.7% reduction compared to outcrossed progeny, suggesting a 39% selling rate in Arabis. Significant inbreeding depression and a mixed mating system are evidence that the deleterious effects of self‐fertilization are maintained through high rates of mildly deleterious mutation. Significant maternal‐parent‐by‐pollination‐treatment interactions for mean seed weight and dry weight are consistent with inbreeding depression caused by deleterious recessives and varying past maternal inbreeding.
Comparisons of ectomycorrhizae on pinyon pines (Pinus edulis; Pinaceae) across extremes of soil type and herbivory
Authors: Gehring Catherine A. , Whitham Thomas G.
Published: January 2018

Using field and greenhouse studies, we examined the relationships among pinyon pines (Pinus edulis), their ectomycorrhizal mutualists, and their moth herbivores as a function of soil fertility. We studied two soil types—the ash and cinder soils of the San Francisco volcanic field and nearby sandy loam soils. In the field, pinyons growing in cinders suffered from reduced moisture, negative nitrogen mineralization rates, low phosphate levels, reduced growth, and high moth herbivory relative to pinyons growing in sandy loam. Pinyons growing in cinders also had twofold higher levels of ectomycorrhizal colonization than their noncinder counterparts. Similarly, in the greenhouse, seedlings grown in cinders had higher levels of ectomycorrhizal colonization and greater numbers of ectomycorrhizae than seedlings grown in sandy loam. Seedling shoot growth was significantly enhanced by ectomycorrhizae in both soils. These patterns support three conclusions. First, field and greenhouse studies demonstrated that trees growing in nutrient‐poor soils had higher levels of ectomycorrhizal colonization than trees growing in better soils. Second, across soil types, variation in ectomycorrhizal colonization was better predicted by soil fertility than by herbivory. However, herbivory negatively affected ectomycorrhizae in the stressful cinder environment. Third, although mycorrhizae can be parasitic under some conditions, ectomycorrhizae had mutualistic impacts on pinyon seedlings across the environmental extremes we studied.
A model and lexicon for pollen fate
Authors: Inouye David W. , Gill Douglas E. , Dudash Michele R. , Fenster Charles B.
Published: January 2018

As pollination biology undergoes unprecedented growth as a discipline, confusion in the use of terms has become increasingly common. The need for a flexible yet unambiguous terminology has become urgent. As an example we discuss how the term “pollination efficiency” is used differently by 18 studies, and “pollinator effectiveness” by seven others. Here we present flowcharts of two general models of pollination systems (biotic and abiotic) that trace all the events from pollen production to development of seed or fruit, and we develop a lexicon for the quantities of pollen, processes of transfers (to a vector, to a stigma), and ratios of quantities that are of interest in studies of pollination and mating systems. An appendix includes a glossary of the definitions we suggest.