bluuebunny/crossref_metadata_2025 huggingface dataset:
Phylogeny and circumscription of the near‐endemic Brazilian tribe Microlicieae (Melastomataceae)
Authors: Fritsch Peter W. , Almeda Frank , Renner Susanne S. , Martins Angela B. , Cruz Boni C.
Published: February 2008

The members of tribe Microlicieae in the flowering plant family Melastomataceae are nearly all endemic to the cerrado biome of Brazil. Traditional classifications of the Melastomataceae have attributed between 15 and 17 genera to the Microlicieae, but subsequent revisions have circumscribed the tribe more narrowly. The monophyly and intergeneric relationships of the Microlicieae were evaluated through phylogenetic analyses with molecular and morphological data sets. Incorporation of DNA sequences from the intron of the chloroplast gene rpl16 into a previously generated family‐wide data set yielded a clade comprising Chaetostoma, Lavoisiera, Microlicia, Rhynchanthera, Stenodon, and Trembleya (“core Microlicieae”), with Rhynchanthera as the first‐diverging lineage. The other four genera of Microlicieae sampled are placed in other clades: Eriocnema with Miconieae; Siphanthera with Aciotis, Nepsera, and Acisanthera of Melastomeae; Castratella as sister to Monochaetum of Melastomeae; and Cambessedesia as part of an unresolved polytomy in a large clade that includes most Melastomataceae. Analyses of the chloroplast genes rbcL and ndhF that included three core genera produced similar results, as did the combined analysis of all three data sets. Combined parsimony analyses of DNA sequences from rpl16 and the nuclear ribosomal intercistronic transcribed spacer (ITS) region of 22 species of core Microlicieae yielded generally low internal support values. Lavoisiera, recently redefined on the basis of several morphological characters, was strongly supported as monophyletic. A morphological phylogenetic analysis of the Microlicieae based on 10 parsimony‐informative characters recovered a monophyletic core Microlicieae but provided no further resolution among genera. Penalized likelihood analysis with two calibration time windows produced an age estimate of 3.7 million years for the time of initial divergence of strictly Brazilian core Microlicieae. This date is in general agreement with the estimated age of the most active stage of development of cerrado vegetation and implies an adaptive shift from hydric to seasonally dry habitats during the early evolution of this group.
Localization of production and emission of pollinator attractant on whole leaves of Chamaerops humilis (Arecaceae)
Authors: Caissard Jean‐Claude , Meekijjironenroj Aroonrat , Baudino Sylvie , Anstett Marie‐Charlotte
Published: February 2008

Volatile compounds, which frequently play important roles in plant–insect interaction, can be produced either by flowers to attract pollinators or by leaves to deter herbivores. The specialized structures associated with odor production differ in these two organs. The European dwarf palm Chamaerops humilis represents a unique intermediate between these two. In previous work, its leaves were shown to produce volatile organic compounds (VOCs) that attract pollinators only during flowering. Because the leaf sinuses look like a gland, the sinus was examined histologically and with environmental scanning electron microscopy (ESEM) for evidence that the sinus emits VOCs. Volatile compounds emitted by the different parts of the leaf were extracted by washes and headspace then analyzed by gas chromatograph‐mass spectrometer (GC‐MS). The sinus does not have the expected gland‐like structure; the VOCs are actually produced by the whole leaf, even if the composition of the VOCs emitted by the sinus slightly differs. Thus, attraction of pollinators does not result from specialized secreting cells in leaves of flowering European dwarf palms. The results are discussed in the context of a convergent evolution of leaves toward petals.
Herbarium specimens demonstrate earlier flowering times in response to warming in Boston
Authors: Primack Daniel , Imbres Carolyn , Primack Richard B. , Miller‐Rushing Abraham J. , Del Tredici Peter
Published: February 2008

Museum specimens collected in the past may be a valuable source of information on the response of species to climate change. This idea was tested by comparing the flowering times during the year 2003 of 229 living plants growing at the Arnold Arboretum in Boston, Massachusetts, USA, with 372 records of flowering times from 1885 to 2002 using herbarium specimens of the same individual plants. During this period, Boston experienced a 1.5°C increase in mean annual temperature. Flowering times became progressively earlier; plants flowered 8 d earlier from 1980 to 2002 than they did from 1900 to 1920. Most of this shift toward earlier flowering times is explained by the influence of temperature, especially temperatures in the months of February, March, April, and May, on flowering time. Plants with a long flowering duration appear to be as useful for detecting responses to changing temperatures as plants with a short flowering duration. Additional studies using herbarium specimens to detect responses to climate change could examine specimens from specific, intensively collected localities, such as mountain peaks, islands, and unique habitats.
Physical mapping of the 5S and 18S–25S rRNA genes by FISH as evidence thatArachis duranensisandA. ipaensisare the wild diploid progenitors ofA. hypogaea(Leguminosae)
Authors: Seijo J. Guillermo , Lavia Graciela I. , Fernández Aveliano , Krapovickas Antonio , Ducasse Daniel , Moscone Eduardo A.
Published: February 2008

The 5S and the 18S–25S rRNA genes were physically mapped by fluorescent in situ hybridization (FISH) in all botanical varieties of cultivated peanutArachis hypogaea(2n= 4x= 40), in the wild tetraploidA. monticola, and in seven wild diploid species considered as putative ancestors of the tetraploids. A detailed karyotype analysis including the FISH signals and the heterochromatic bands was carried out. Molecular cytogenetic landmarks are provided for the construction of a FISH‐based karyotype inArachisspecies. The size, number, and chromosome position of FISH signals and heterochromatic bands are similar in allA. hypogaeavarieties andA. monticola, but vary among the diploid species. Genome constitution of the species is discussed and several chromosome homeologies are established. The bulk of the chromosome markers mapped, together with data on geographical distribution of the taxa, suggest that peanut originated upon domestication ofA. monticolaand evidence that the diploidsA. duranensisandA. ipaensisare the most probable ancestors of both tetraploid species. Allopolyploidy could have arisen by a single event or, if by multiple events, always from the same diploid species.
Long‐term trends in annual reproductive output of the scrub hickory: factors influencing variation in size of nut crop
Authors: Layne James N. , Abrahamson Warren G.
Published: February 2008

Reproductive output by the Florida‐endemic scrub hickory (Carya floridanaSargent) was studied over a 28‐yr period in three south‐central Florida vegetation associations: southern ridge sandhill, sand pine scrub, and scrubby flatwoods. The objectives were to describe multi‐annual patterns of variation in nut production, identify factors involved in this variation, and investigate differences in patterns among associations. Peaks (higher values bracketed by lower values) in nut production occurred in 7 yr in sandhill and scrub and 8 yr in scrubby flatwoods during the 22‐yr period for which we had continuous data. Of the total of 22 peaks in the three associations combined, 17 occurred at intervals of 2 or 3 yr, and peaks occurred in the same years in 18 of the 22 cases. Periodicities of nut production generated by spectral analyses (Fourier transforms) generally agreed with the observed peaks. Numbers of nuts per bearing ramet, proportion of ramets bearing nuts, ramet height, and light availability were positively correlated with nut production. Weather variables, specifically winter rainfall and minimum spring temperatures, accounted for a total of about one‐quarter to one‐half of the variance in nut production depending on the vegetation association. Following a prescribed fire in a sandhill plot, scrub hickory quickly regained fruit production, but over a 5‐yr period following the fire nut production by ramets in the largest size class was reduced compared with the unburned control plot.
Molecular phylogenetics of Phyllanthaceae: evidence from plastid MATK and nuclear PHYC sequences
Authors: Samuel Rosabelle , Kathriarachchi Hashendra , Hoffmann Petra , Barfuss Michael H. J. , Wurdack Kenneth J. , Davis Charles C. , Chase Mark W.
Published: February 2008

Plastid matK and a fragment of the low‐copy nuclear gene PHYC were sequenced for 30 genera of Phyllanthaceae to evaluate tribal and generic delimitation. Resolution and bootstrap percentages obtained with matK are higher than that of PHYC, but both regions show nearly identical phylogenetic patterns. Phylogenetic relationships inferred from the independent and combined data are congruent and differ from previous, morphology‐based classifications but are highly concordant with those of the plastid gene rbcL previously published. Phyllanthaceae is monophyletic and gives rise to two well‐resolved clades (T and F) that could be recognized as subfamilies. DNA sequence data for Keayodendron and Zimmermanniopsis are presented for the first time. Keayodendron is misplaced in tribe Phyllantheae and belongs to the Bridelia alliance. Zimmermanniopsis is sister to Zimmermannia. Phyllanthus and Cleistanthus are paraphyletic. Savia and Phyllanthus subgenus Kirganelia are not monophyletic.
Molecular phylogenetic systematics and biogeography of tribe Neillieae (Rosaceae) using DNA sequences of cpDNA, rDNA, and LEAFY
Authors: Oh Sang‐Hun , Potter Daniel
Published: February 2008

A phylogeny of the tribe Neillieae (Rosaceae), which comprisesNeillia,Stephanandra, andPhysocarpus, was reconstructed based on nucleotide sequences of several regions of cpDNA, the ITS and ETS regions of rDNA, and the second intron ofLEAFY, to elucidate relationships among genera and species in Neillieae and to assess the historical biogeography of the tribe. Phylogenetic analyses indicated thatPhysocarpusandNeillia‐Stephanandrawere strongly supported as monophyletic and suggested thatStephanandramay have originated by hybridization between two lineages ofNeillia. Dispersal‐vicariance analyses suggested that the most recent common ancestor of Neillieae may have occupied eastern Asia and western North America and thatPhysocarpusandNeillia‐Stephanandramay have been split by an intercontinental vicariance event in the early Miocene. The biogeographic analyses also suggested that species ofNeilliaandStephanandradiversified in eastern Asia, whereas inPhysocarpusone dispersal event from western North America to eastern Asia occurred. Two divergent types ofLEAFYsequences were found in the eastern North American species,P. opulifolius, but only one type was present in each plant. The two types of sequences may represent homeologous genes that originated by hybridization betweenP. capitatusandP. monogynus, both western North American species.
Evaluation of new Lesquerella and Physaria (Brassicaceae) oilseed germplasm
Authors: Salywon Andrew M. , Dierig David A. , Rebman Jon P. , de Rodríguez Diana Jasso
Published: February 2008

The seed oil of Lesquerella and the closely related genus Physaria (Brassicaceae) is rich in hydroxy fatty acids (HFAs). HFAs and their derivatives are used to produce a variety of industrial products including lubricants, nylon‐11, plastics, drying agents, protective coatings, surfactants, cosmetics, and pharmaceuticals. Lesquerella fendleri is being developed as a new crop for arid regions of the southwestern United States as an alternative source of HFAs. Between 1995 and 2001, 66 accessions from 28 species of Lesquerella were collected in the United States, 33 accessions from four species were collected in Mexico, and 41 accessions from 15 species of Physaria were collected from the southwestern United States. Mean seed mass ranged from 0.54 to 2.30 mg for Lesquerella compared to 1.70 to 5.80 mg for Physaria. Seed oil content ranged from a high of 32.2% in Lesquerella to a high of 35.4% in Physaria. The fatty acid profile of all species of Physaria and most of the lesquerolic‐acid‐rich species of Lesquerella contained from 30 to 55% lesquerolic acid, although several species contained >60%. These collections of wild germplasm provide a diverse gene pool that should enhance our breeding program in developing a domestic source of HFAs.
Trans‐species shared polymorphisms at orthologous nuclear gene loci among distant species in the conifer Picea (Pinaceae): implications for the long‐term maintenance of genetic diversity in trees
Authors: Bouillé Marie , Bousquet Jean
Published: February 2008

For each of three nuclear gene loci, intraspecific‐ as well as trans‐specific shared polymorphisms were detected in DNA among three distantly related species in the genus Picea. Few fixed interspecific polymorphisms were observed. Allele genealogies did not match species phylogenies, and species lineages were not reciprocally monophyletic. Based on molecular clocks and morphological evidence from the fossil record, the divergence time between species was estimated at 13–20 million years (my), and a mutation rate of 2.23 × 10−10 to 3.42 × 10−10 per site per year was estimated. Large historical population sizes in excess of 100 000 were inferred, which would have delayed the fixation of polymorphisms. These numbers translated into allele coalescence times in the order of 10 to 18 my, which implies the sharing of polymorphisms since common ancestry. These results suggest that trans‐species shared polymorphisms might be frequent at plant nuclear gene loci, leading to high allelic diversity. Such a trend is more likely in trees and plants characterized by ecological and life‐history determinants favoring large population sizes such as an outcrossing mating system, wind pollination, and a dominant position in ecosystem. These polymorphisms also call for caution in estimating congeneric species phylogenies from nuclear gene sequences in such plant groups.
The Crepidotaceae (Basidiomycota, Agaricales): phylogeny and taxonomy of the genera and revision of the family based on molecular evidence
Authors: Aime M. Catherine , Vilgalys Rytas , Miller Orson K.
Published: February 2008

Advances in phylogenetic systematics have clarified the position of most major homobasidiomycete lineages. In contrast, the status of the Crepidotaceae, a historically controversial family of dark‐spored agarics, remains unaddressed. In this paper, current morphology‐based classifications of the agaric genera of the Crepidotaceae were evaluated by parsimony and constraint analyses of sequence data from the nuclear large subunit rDNA. Taxa analyzed included the type species for each agaric genus allied in the family by Singer: Crepidotus, Simocybe, Pleurotellus, Tubaria, and Melanomphalia. Contrary to traditional classifications, results suggest that the crepidotoid fungi have three separate origins within the euagarics. The Crepidotaceae sensu stricto (s.s.) includes Crepidotus and Simocybe and represents a separate lineage of dark‐spored euagarics. Pleurotellus is congeneric with Crepidotus. Results indicate the exclusion of both Tubaria and Melanomphalia from the Crepidotaceae s.s. Tubaria is allied with the strophariaceous taxa Phaeomarasmius and Flammulaster, while Melanomphalia has arisen from within a lineage of light‐spored omphalinoid euagarics representing an independent acquisition of basidiospore pigmentation. Other pleisiomorphic and newly uncovered synapomorphic characters are discussed in detail along with the taxonomic status of each genus, and a revised family description is provided.
Stomatal architecture and evolution in basal angiosperms
Authors: Carpenter Kevin J.
Published: February 2008

Stomatal architecture—the number, form, and arrangement of specialized epidermal cells associated with stomatal guard cells—of 46 species of basal angiosperms representing all ANITA grade families and Chloranthaceae was investigated. Leaf clearings and cuticular preparations were examined with light microscopy, and a sample of 100 stomata from each specimen was coded for stomatal type and five other characters contributing to stomatal architecture. New stomatal types were defined, and many species were examined and illustrated for the first time. Character evolution was examined in light of the ANITA hypothesis using MacClade software. Analysis of character evolution, along with other evidence from this study and evidence from the literature on fossil angiosperms and other seed plant lineages, suggests that the ancestral condition of angiosperms can be described as anomo‐stephanocytic, a system in which complexes lacking subdidiaries (anomocytic) intergrade with those having weakly differentiated subsidiaries arranged in a rosette (stephanocytic). From this ancestral condition, tangential divisions of contact cells led to the profusion of different types seen in early fossil angiosperms and Amborellaceae, Austrobaileyales, and derived Chloranthaceae, while the state in Nymphaeales is little modified. Formation of new, derived types by tangential division appears to be a recurrent theme in seed plant evolution.
Response of root branching to abscisic acid is correlated with nodule formation both in legumes and nonlegumes
Authors: Liang Yan , Harris Jeanne M.
Published: February 2008

Legumes are unique among higher plants in forming a symbiosis with Rhizobium. Phylogenetic studies indicate this symbiosis may have evolved as many as three times within the Fabaceae; alternatively, a predisposition for nodulation evolved early in the history of the legume lineage. We have identified a physiological trait—increased lateral root formation in response to abscisic acid (ABA)— that marks all nodulating and non‐nodulating legume species in our study set with the exception of Chamaecrista fasciculata and Cercis occidentalis. In contrast, nonlegume species tested decrease lateral root formation in response to ABA. Cercis is not a descendant of any common ancestor hypothesized to have evolved Rhizobium nodulation and has an intermediate response to ABA, partway between that of nonlegumes and legumes. We suggest that acquisition of altered responsiveness of roots to ABA is coincident with the appearance of a predisposition for nodulation within the legumes, followed by a loss in Chamaecrista. In addition, we demonstrate that altered ABA responsiveness of lateral root formation characterizes roots of the actinorhizal nodulator, Casuarina glauca, but not the closely related, nonactinorhizal species, Betula papyrifera. Thus our data provide evidence for a physiological root trait associated with nodulation both in legumes and in an actinorhizal plant.
The importance of frictional interactions in maintaining the stability of the twining habit
Authors: Silk Wendy K. , Holbrook N. Michele
Published: February 2008

The stability of twining vines under gravitational loads suggests an important role for friction. The coefficient of friction, μ, between vine stems and wood is high, often five times greater than between leather and wood, as determined by slip tests on an inclined plane. Stem trichomes function like ratchets to facilitate climbing upward (or to facilitate slipping if the stem is inverted). A mathematical model predicts large masses (kg) must be applied to the base of a twining vine to cause slipping. Vines slip as predicted when μ is low and arc length on the pole is short, and they break before slipping when μ is large or arc length is long. In contrast, twining vines are unstable in compression, collapsing when small masses (<10 g) are hung from the top of the vine. However, if the loads are applied below the uppermost gyre, the stabilizing tensional effect dominates. Therefore, in nature vines twining on a cylindrical support are stable under gravitational loads, unless these loads occur near the apex. A corollary is that a short apical coil can hold up large masses of maturing shoot.
Inversostyly: a new stylar polymorphism in an oil‐secreting plant,Hemimeris racemosa(Scrophulariaceae)
Authors: Pauw Anton
Published: February 2008

A new kind of stylar polymorphism, provisionally called inversostyly, is described. The polymorphism occurs inHemimeris racemosa(Scrophulariaceae), a common annual herb of the Cape region of South Africa. Most populations are dimorphic for style orientation: the style alternates with the two stamens and is deflected either upwards or downwards. Thus, there is reciprocal placement of the style and stamens in a vertical plane in zygomorphic flowers. The flowers are symmetrical, and the floral parts do not vary in length. All flowers on a given plant are of the same stylar orientation. Pollination is by specialized oil‐collecting bees (Redivivaspp.), which carry the pollen of the two morphs separately in discrete anterior or posterior locations on the underside of the body. Most inversostylous populations have a slightly higher proportion of the style‐down morph, and this bias increases with decreasing pollinator abundance. In contrast with inversostylous populations, all individuals in homostylous populations ofH. racemosahave the style and the stamens clustered together in the down position and high levels of autogamous seed set. Homostylous populations ofH. racemosa, as well as the homostylous speciesHemimeris sabulosa, occur where oil‐collecting bees are less abundant.
Intra‐ and interspecific phylogenetic relationships among diploid Triticum‐Aegilops species (Poaceae) based on base‐pair substitutions, indels, and microsatellites in chloroplast noncoding sequences
Authors: Yamane Kyoko , Kawahara Taihachi
Published: February 2008

This study analyzes intra‐ and interspecific variation in chloroplast DNA (cpDNA) in diploid Triticum‐Aegilops species. This analysis focused on DNA sequence variation in noncoding regions of cpDNA, which included base‐pair substitutions, insertion/deletions (indels, 50 loci pooled), microsatellites (7 loci pooled), and inversions. Nine of 13 Triticum‐Aegilops species were successfully identified and genotyped using these data. Sixty‐two haplotypes were detected in 115 accessions of 13 diploid species. Because of the large number of characters examined, novel deep relationships within and among Triticum‐Aegilops species could be identified and evaluated. Phylogenetic trees for the genus Triticum‐Aegilops were constructed with Hordeum vulgare and Dasypyrum villosum as outgroups, and the results were compared to previous studies. These data support the following inferences: (1) Aegilops species should be included in Triticum; (2) groups D, T, M, N, U, and section Sitopsis (except Ae. speltoides) underwent speciation concurrently, but most diploid species evolved independently; (3) Ae. mutica does not occupy a basal position in Triticum‐Aegilops; (4) Ae. speltoides is in a basal position and differs significantly from other Sitopsis species; (5) Ae. caudata is polyphyletic in all trees; (6) the genus Aegilops is paraphyletic with Secale.
Phylogeny of Flaveria (Asteraceae) and inference of C4 photosynthesis evolution
Authors: McKown Athena D. , Moncalvo Jean‐Marc , Dengler Nancy G.
Published: February 2008

A well‐resolved phylogeny of Flaveria is used to infer evolutionary relationships among species, biogeographical distributions, and C4 photosynthetic evolution. Data on morphology, life history, and DNA sequences (chloroplastic trnL‐F, nuclear ITS and ETS) for 21 of 23 known species were collected. Each data set was analyzed separately and in combination using maximum parsimony and Bayesian analyses. The phylogeny of Flaveria is based on the combined analysis of all data. Our phylogenetic evidence indicates that C3 Flaveria are all basal to intermediate (C3‐C4 and C4‐like) and fully expressed C4 Flaveria species. Two strongly supported clades (A and B) are present. Using this phylogeny, we evaluate the current systematics of the genus and suggest the removal and reevaluation of certain taxa. We also infer the center of origin and dispersal of Flaveria species. Multiple origins of photosynthetic pathway intermediacy in Flaveria are recognized. C3‐C4 intermediacy has evolved twice in the genus and is found to be evolutionarily intermediate in clade A, but not necessarily in clade B. C4‐like photosynthesis is also derived once in each clade. In addition, fully expressed C4 photosynthesis may have evolved up to three times within clade A.
A new Late Cretaceous ginkgoalean reproductive structure Nehvizdyella gen. nov. from the Czech Republic and its whole‐plant reconstruction
Authors: Kvaček Jiří , Falcon‐Lang Howard J. , Dašková Jiřina
Published: February 2008

During the Mesozoic Era, gingkoaleans comprised a diverse and widespread group. Here we describe ginkgoalean fossils in their facies context from the Late Cretaceous (Cenomanian) Peruc‐Korycany Formation of the Czech Republic and present a reconstruction of tree architecture and ecology. Newly described in this study is the ovuliferous reproductive structure, Nehvizdyella bipartita gen. et sp. nov. (Ginkgoales). This ovuliferous organ consists of a bifurcating axis, terminated by large cupule‐like structures, probably homologous to the collar of the recent Ginkgo. Each cupule encloses an orthotropous ovule. In specimens with the early developmental stages preserved, the entire ovule and young seed, with the exception of the micropylar area, is embedded in the cupule. Mature seeds consist of sclerotesta and sarcotesta. Monosulcate pollen grains of Cycadopites‐type are found adhering to the seeds. Although similar to Ginkgo in terms of its large size and reduced number of seeds, N. bipartita differs from the extant genus in having ovules completely enclosed in a cupule‐like structure. The co‐occurrence of N. bipartita with ginkgoalean leaves of Eretmophyllum obtusum (Velenovský) Kvaček, J., ginkgoalean short shoots of Pecinovicladus kvacekii Falcon‐Lang, and ginkgoalean trunk wood of Ginkgoxylon gruettii Pons and Vozenin‐Serra in monodominant taphocoenoses at four geographically distant localities suggests that these remains all belong to one plant. This is supported by the close morphological and anatomical similarity between the different organs. Facies analysis of plant assemblages indicates that our Cretaceous tree occupied a water‐stressed coastal salt marsh environment. It therefore represents the first unequivocal halophyte among the Ginkgoales.
Microhabitat distribution of two Florida scrub endemic plants in comparison to their habitat‐generalist congeners
Authors: Maliakal‐Witt Satya , Menges Eric S. , Denslow J. S.
Published: February 2008

Habitat‐specialist species may be restricted to a narrower range of microhabitats than habitat‐generalist species. We addressed this hypothesis by comparing microhabitats of two pairs of congeners that differ in habitat specificity and co‐occur in one distinct habitat type, Florida rosemary scrub. We characterized microhabitats of rosemary scrub specialists,Polygonella basiramiaandLechea cernua, their habitat‐generalist congeners,Polygonella robustaandLechea deckertii, and random points in the rosemary scrub habitat. Plants of both habitat specialists occurred in microhabitats with significantly more bare sand than plants of habitat‐generalist species and random points. Plants of all four species occurred in microhabitats that were farther from dominant shrubs,CeratiolaandQuercusspp., than random points. Seedlings of both habitat specialists grew larger in bare sand microhabitats, whereas ground lichens and litter did not affect seedling growth of the habitat generalists. As the time since fire increases, bare sand cover decreases,Ceratioladensity increases,Quercusdensity remains constant, and shrubs become taller. Physical characteristics, such as soil temperature, soil carbon, and soil moisture, differ slightly with respect to microhabitat. Our results suggest thatP. basiramiaandL. cernuaare specialized on bare sand microhabitats that characterize their preferred habitat, rosemary scrub. Microhabitat specialization may limit the distribution of these rare species.
Hybrid origins and F1dominance in the free‐floating, sterile bladderwort,Utricularia australisf.australis(Lentibulariaceae)
Authors: Kameyama Yoshiaki , Toyama Masahiro , Ohara Masashi
Published: February 2008

Abandonment of sexual reproduction is a well‐known characteristic in aquatic plants, while the causes, levels, and consequences of sterility are often unknown.Utricularia australisf.australis(Lentibulariaceae) is a free‐floating, sterile bladderwort distributed widely in temperate and tropical regions. Experimental crosses in cultivated conditions, AFLP analysis, and cpDNA haplotypes of natural populations clearly demonstrated thatU. australisf.australisoriginates from the asymmetric hybridization between two parental taxa:U. australisf.tenuicaulis(mostly as female) andU. macrorhiza(mostly as male). No post‐F1hybrids were detected using the additive patterns of AFLP bands combined with the observation of extensive sterility inU. australisf.australis. Recurrent hybridizations and subsequent perpetuation by asexual reproduction were demonstrated by the unique, but monomorphic, AFLP genotypes observed in eachU. australisf.australispopulation. Hybrids and parental species did not coexist, implying the superiority of the hybridU. australisf.australisin certain environmental conditions. It remains unclear whether populations ofU. australisf.australisare maintained by colonizing propagules or as relicts of past hybridization events.
Hybrid origin of “Bauhinia blakeana” (Leguminosae: Caesalpinioideae), inferred using morphological, reproductive, and molecular data
Authors: Lau Carol P. Y. , Ramsden Lawrence , Saunders Richard M. K.
Published: February 2008

Bauhinia blakeana (Leguminosae subfam. Caesalpinioideae tribe Cercideae), or the Hong Kong Orchid Tree, is of great horticultural value. It is completely sterile and is shown here to be the result of hybridization between the largely sympatric species, B. purpurea and B. variegata. Although the analysis of patterns of morphological variation revealed only a few examples of phenotypic intermediacy, study of intersimple sequence repeat (ISSR) markers enabled unequivocal identification of the parental species due to the presence of additive inheritance of alleles and the absence of any bands that are unique to B. blakeana. Investigation of aspects of the reproductive biology of the taxa furthermore revealed that the parental species are largely xenogamous, have flowering periods that overlap seasonally and temporally, and share common pollinators. Evidence is provided to show that B. blakeana is not naturally stabilized and is only maintained horticulturally by artificial propagation. It is therefore recommended that the hybrid be regarded as a horticultural cultivar rather than a naturally occurring species; a new cultivar name, Bauhinia ‘Blakeana’, is accordingly validated.
Post‐meiotic cytokinesis and pollen aperture pattern ontogeny: comparison of development in four species differing in aperture pattern
Authors: Ressayre Adrienne , Dreyer Leanne , Triki‐Teurtroy Sarah , Forchioni Arlette , Nadot Sophie
Published: February 2008

Pollen aperture patterns vary widely in angiosperms. An increasing number of studies indicate that aperture pattern ontogeny is correlated with the way in which cytokinesis that follows male meiosis is completed. The formation of the intersporal callose walls that isolate the microspores after meiosis was studied in four species with different aperture patterns (two monocots,Phormium tenaxandAsphodelus albus, and two eudicots,Helleborus foetidusandProtea lepidocarpodendron). The way in which post‐meiotic cytokinesis is performed differs between all four species, and variation in callose deposition appears to be linked to aperture pattern definition.
Monophyly of Kelloggia Torrey ex Benth. (Rubiaceae) and evolution of its intercontinental disjunction between western North America and eastern Asia
Authors: Nie Ze‐Long , Wen Jun , Sun Hang , Bartholomew Bruce
Published: February 2008

Kelloggia Torrey ex Bentham (Rubiaceae) consists of two species disjunctly distributed in western North America (K. galioides Torrey) and the western part of eastern Asia (K. chinensis Franch.). The two species exhibit a high level of morphological divergence. To test its monophyly and to infer its biogeographic history, we estimated the phylogeny of Kelloggia and its relatives from sequences of three chloroplast DNA regions (rbcL gene, atpB‐rbcL spacer, and rps16 intron). The monophyly of Kelloggia was strongly supported, and it forms a sister relationship with the tribe Rubieae. The divergence time between the two disjunct species of Kelloggia was estimated to be 5.42 ± 2.32 million years ago (mya) using the penalized likelihood method based on rbcL sequence data with fossil calibration. Our result does not support the Madrean‐Tethyan hypothesis, which assumes an earlier divergence time of 20–25 mya. Ancestral area analysis, as well as dispersal‐vicariance (DIVA) analysis, suggests the Asian origin of Kelloggia and the importance of Eurasia in the diversification of its close relatives in the Rubieae‐Theligoneae‐Paederieae group. The intercontinental disjunction in Kelloggia is suggested to have evolved via long‐distance dispersal from Asia into western North America.
Viburnum phylogeny based on combined molecular data: implications for taxonomy and biogeography
Authors: Winkworth Richard C. , Donoghue Michael J.
Published: February 2008

We investigated Viburnum phylogeny using separate and combined analyses of DNA sequence data from two chloroplast and three nuclear loci. Separate analyses of nuclear and chloroplast data sets resulted in gene trees that were generally congruent with one another and with trees from two previous analyses. Our gene trees do differ in the position of section Pseudotinus, as well as in species relationships within sections Pseudotinus and Lentago. However, tests for incongruence indicate that differences between the nuclear and chloroplast data are not significant. Furthermore, gene trees from combined analyses were highly similar to those found in separate analyses, suggesting that these localized differences do not affect other parts of the tree. Our analyses provide convincing support for numerous relationships, although there is still uncertainty at the base of the tree. To facilitate future study, we propose informal names for 12 well‐supported species groups, as well as for several higher‐level clades. We also discuss the biogeographic implications of our phylogeny, focusing on repeated, although apparently temporally incongruent, patterns of disjunction between the Old and New Worlds.
Growth and photosynthetic responses of the federally endangered shrub, Lindera melissifolia (Lauraceae), to varied light environments
Authors: Aleric Katherine M. , Katherine Kirkman L.
Published: February 2008

Photosynthetic, morphological, and growth responses to light environment can be useful measurements to determine favorable habitat conditions for the conservation of endangered species. For Lindera melissifolia (Walt.) Blume, we compared morphological and photosynthetic responses under natural and controlled light regimes, and growth under three light treatments: 100%, 42%, and 19% full sunlight. Typical sun–shade morphological responses to decreasing light levels included decreased stomatal density, increased specific leaf area, and increased leaf area ratio. Photosynthetic capacity (3–6 μmol CO2 · m−2 · s−1) was consistent with other shade‐tolerant species. Light‐saturated rates of photosynthesis of experimental plants increased with increasing light up to 42% sunlight, but declined at 100% sunlight. The 100% light treatment also resulted in lower plant biomass, primarily from a reduction in root biomass. Results indicate that canopy conditions at levels below 40% sunlight are optimal for plant growth and should be considered in management and reintroduction efforts for this species.
Endozoochorous dispersal of aquatic plants: does seed gut passage affect plant performance?
Authors: Figuerola Jordi , Santamaría Luis , Green Andy J. , Luque Isabel , Alvarez Raquel , Charalambidou Iris
Published: February 2008

The ingestion of seeds by vertebrates can affect the germinability and/or germination rate of seeds. It is, however, unclear if an earlier germination as a result of ingestion affects later plant performance. For sago pondweed, Potamogeton pectinatus, the effects of seed ingestion by ducks on both germinability and germination rate have been previously reported from laboratory experiments. We performed an experiment to determine the effects of seed ingestion by ducks on germination, seedling survival, plant growth and asexual multiplication. Both at the start and end of the winter, seeds were fed to three captive shovelers (Anas clypeata) and planted outdoors in water‐filled containers. Plant biomass and its allocation to vegetative parts (shoot and roots), tubers, and seeds were determined in autumn. More duck‐ingested seeds than control (uningested) seeds germinated in early winter, but this difference disappeared for seeds planted in late winter, when the treatments were first stratified for 3 mo. None of the variables for measuring seedling survival and plant performance varied between treatments. Under our experimental conditions (no herbivory or competition), ingestion by ducks in early winter resulted in increased performance for seeds surviving gut passage due to enhanced seed germinability, without other costs or benefits for the seedlings.
Genome evolution among cruciferous plants: a lecture from the comparison of the genetic maps of three diploid species—Capsella rubella, Arabidopsis lyrata subsp. petraea, and A. thaliana
Authors: Koch Marcus A. , Kiefer Markus
Published: February 2008

Comparative mapping in cruciferous plants is ongoing, and recently two additional genetic maps of diploid Capsella and Arabidopsis lyrata subsp. petraea have been presented. We compared both maps with each other using the sequence map and genomic data resources from Arabidopsis thaliana as a reference. The ancestors of the species pair Capsella–Arabidopsis diverged from one another approximately 10–14 million years ago (mya), whereas Arabidopsis thaliana and Arabidopsis lyrata have been separated since roughly 5–6 mya. Our analysis indicated that among diploid Capsella and Arabidopsis lyrata all eight genetic linkage groups are totally colinear to each other, with only two inversions significantly differentiating these two species.

By minimizing the number of chromosomal rearrangements during genome evolution, we presented a model of chromosome evolution involving all three species. From this scenario, it is obvious that Arabidopsis thaliana underwent a dramatic genome reconstruction, with a base chromosome number reduction from five to eight and with approximately 1.3 chromosomal rearrangements per million years. In contrast, the terminal lineage leading to Capsella has only undergone less than 0.09 rearrangements per million years. This is the same rate as calculated for Arabidopsis lyrata since its separation from the Capsella lineage 10–14 mya. These results are in strong contrast to all overestimated rates calculated from comparisons of the systems Arabidopsis thaliana and Brassica, and our data demonstrate the problematic nature of both model systems.
Microsatellite analysis reveals genetically distinct populations of red pine (Pinus resinosa, Pinaceae)
Authors: Boys Jacquelyn , Cherry Marilyn , Dayanandan Selvadurai
Published: February 2008

Red pine (Pinus resinosaAit.) is an ecologically and economically important forest tree species of northeastern North America and is considered one of the most genetically depauperate conifer species in the region. We have isolated and characterized 13 nuclear microsatellite loci by screening a partial genomic library with di‐, tri‐, and tetranucleotide repeat oligonucleotide probes. In an analysis of over 500 individuals representing 17 red pine populations from Manitoba through Newfoundland, five polymorphic microsatellite loci with an average of nine alleles per locus were identified. The mean expected and observed heterozygosity values were 0.508 and 0.185, respectively. Significant departures from Hardy‐Weinberg equilibrium with excess homozygosity indicating high levels of inbreeding were evident in all populations studied. The population differentiation was high with 28–35% of genetic variation partitioned among populations. The genetic distance analysis showed that three northeastern (two Newfoundland and one New Brunswick) populations are genetically distinct from the remaining populations. The coalescence‐based analysis suggests that “northeastern” and “main” populations likely became isolated during the most recent Pleistocene glacial period, and severe population bottlenecks may have led to the evolution of a highly selfing mating system in red pine.
Physiological mechanism of population differentiation in shade‐avoidance responses between woodland and clearing genotypes ofImpatiens capensis
Authors: von Wettberg Eric J. , Schmitt Johanna
Published: February 2008

Forest understory plants often respond less intensely to reduced ratios of red to far red (R : FR) light, an important signal of foliage shade, than conspecific or congeneric plants from open‐canopy sites. Reduced responsiveness to low R : FR in plants from closed‐canopy sites could be caused by two physiological mechanisms. First, closed‐canopy plants could have less sensitive shade‐avoidance responses to low R : FR. Second, the high irradiance response to FR (FR‐HIR), which allows seedling de‐etiolation under low R : FR, might be stronger or persist longer after de‐etiolation in closed‐canopy plants, thus counteracting shade‐avoidance responses to low R : FR. These hypotheses were tested using diodes that emit red and far‐red light to distinguish the responses to altered R : FR of genotypes ofImpatiens capensiscollected from a pair of open‐ and closed‐canopy populations that have previously been shown to differ in sensitivity to R : FR. Genotypes from the open‐canopy environment exhibited typical shade‐avoidance responses, elongating in response to supplemental FR. However, genotypes from the closed‐canopy environment responded to supplemental FR by elongatinglessthan under ambient control conditions, indicating a persistent FR‐HIR. Thus, the observed population differentiation in response to low R : FR may be linked to population differences in FR‐HIR.
Theory for why dioecious plants have equal length sex chromosomes
Authors: Gorelick Root
Published: February 2008

Dioecy and sex chromosomes almost certainly evolved from ancestral hermaphrodites that only possessed autosomes. There is a growing body of evidence that genes for female or male function were then epigenetically suppressed in some of these hermaphrodites, creating the first males or females and nascent sex chromosomes. The incipient sex‐determining epigenetic signals, such as cytosine methylation, then drove Muller's ratchet in many animals, resulting in shorter Y chromosomes. Based on this theory of sex chromosome evolution and limited data on gametophyte gene expression, I argue that plants should be largely immune from Muller's ratchet and therefore retain their ancestral state of equal length sex chromosomes, unless they incur chromosomal rearrangements or large‐scale insertions of duplicated genomes. Usually heteromorphic sex chromosomes canalize dioecy, but extensive polyploidy or polysomy can provide an escape from this canalized dioecy. This theory implies that dioecy due to heteromorphic sex chromosomes should be evolutionarily ephemeral in bryophytes and homosporous pteridophytes because of their extraordinarily high incidences of polyploidy. And, if anything, these very high incidences of polyploidy are responsible for translocation or gradual addition of beneficial genes, rather than gradual reduction in the length of a sex chromosome.
The evolution of unisexual flowers: morphological and functional convergence results from diverse developmental transitions
Authors: Mitchell Caroline H. , Diggle Pamela K.
Published: February 2008

Unisexual flower morphology was examined within a phylogenetic context in order to identify developmental transitions associated with the multiple origins of dioecy in flowering plants. Historically, two categories of unisexual flowers have been recognized: type I flowers exhibit rudiments of the nonfunctional organ type, while type II flowers bear no vestigial sexual organs. Mapping of these flower types onto a composite phylogeny shows that type II morphology is homoplasious and has resulted from at least four distinct evolutionary developmental pathways. The historical assignment of unisexual flowers into only two morphological types has masked important developmental and evolutionary dynamics.
Correlations of climate and plant ecology to leaf size and shape: potential proxies for the fossil record
Authors: Royer Dana L. , Wilf Peter , Janesko David A. , Kowalski Elizabeth A. , Dilcher David L.
Published: February 2008

The sizes and shapes (physiognomy) of fossil leaves are widely applied as proxies for paleoclimatic and paleoecological variables. However, significant improvements to leaf‐margin analysis, used for nearly a century to reconstruct mean annual temperature (MAT), have been elusive; also, relationships between physiognomy and many leaf ecological variables have not been quantified. Using the recently developed technique of digital leaf physiognomy, correlations of leaf physiognomy to MAT, leaf mass per area, and nitrogen content are quantified for a set of test sites from North and Central America. Many physiognomic variables correlate significantly with MAT, indicating a coordinated, convergent evolutionary response of fewer teeth, smaller tooth area, and lower degree of blade dissection in warmer environments. In addition, tooth area correlates negatively with leaf mass per area and positively with nitrogen content. Multiple linear regressions based on a subset of variables produce more accurate MAT estimates than leaf‐margin analysis (standard errors of ±2 vs. ±3°C); improvements are greatest at sites with shallow water tables that are analogous to many fossil sites. The multivariate regressions remain robust even when based on one leaf per species, and the model most applicable to fossils shows no more signal degradation from leaf fragmentation than leaf‐margin analysis.
N, P, and C stoichiometry ofEranthis hyemalis(Ranunculaceae) and the allometry of plant growth
Authors: Niklas Karl J. , Cobb Edward D.
Published: February 2008

We report the nitrogen (N), phosphorus (P), and carbon (C) stoichiometry for each of the five organ‐types (leaves, aerial stems, reproductive organs, roots, and tubers) of 17 actively growingEranthis hyemalisplants differing in size (as measured in g C). We also report the N, P, and C stoichiometry of 20 winterized tubers, which are the only perennial organs of this species. Comparisons between whole‐plant and winterized N/C and P/C levels indicate that N was resorbed from aerial organs and stored in tubers by the end of the growing season. Leaves were substantial reservoirs for N and P. With few exceptions, N scaled isometrically with respect to C for each organ‐type, whereas P scaled as the 3/4 power of C. Thus, N is proportional to P3/4, which is proportional to C regardless of organ‐type. Additionally, annual growth rateGof shoots (leaves and aerial stems) scaled as the −3 power of leaf N/P quotients such thatGwas proportional to the 3/4 power of leaf P. We suggest that these scaling relationships (together with previously reported allometric trends across herbaceous species) show that growth is constrained by organ‐specific N and P allocation patterns (presumably to proteins and ribosomes, respectively).