bluuebunny/crossref_metadata_2025 huggingface dataset:
Phylogeny ofPopulus(Salicaceae) based on nucleotide sequences of chloroplast TRNT‐TRNF region and nuclear rDNA
Authors: Hamzeh Mona , Dayanandan Selvadurai
Published: February 2008

The species of the genusPopulus, collectively known as poplars, are widely distributed over the northern hemisphere and well known for their ecological, economical, and evolutionary importance. The extensive interspecific hybridization and high morphological diversity in this group pose difficulties in identifying taxonomic units for comparative evolutionary studies and systematics. To understand the evolutionary relationships among poplars and to provide a framework for biosystematic classification, we reconstructed a phylogeny of the genusPopulusbased on nucleotide sequences of three noncoding regions of the chloroplast DNA (intron oftrnLand intergenic regions oftrnT‐trnLandtrnL‐trnF) and ITS1 and ITS2 of the nuclear rDNA. The resulting phylogenetic trees showed polyphyletic relationships among species in the sectionsTacamahacaandAigeiros. Based on chloroplast DNA sequence data,P. nigrahad a close affinity to species of sectionPopulus, whereas nuclear DNA sequence data suggested a close relationship betweenP. nigraand species of the sectionAigeiros, suggesting a possible hybrid origin forP. nigra. Similarly, the chloroplast DNA sequences ofP. tristisandP. szechuanicawere similar to that of the species of sectionAigeiros, while the nuclear sequences revealed a close affinity to species of the sectionTacamahaca, suggesting a hybrid origin for these two Asiatic balsam poplars. The incongruence between phylogenetic trees based on nuclear‐ and chloroplast‐DNA sequence data suggests a reticulate evolution in the genusPopulus.
The tortoise and the hare II: relative utility of 21 noncoding chloroplast DNA sequences for phylogenetic analysis
Authors: Shaw Joey , Lickey Edgar B. , Beck John T. , Farmer Susan B. , Liu Wusheng , Miller Jermey , Siripun Kunsiri C. , Winder Charles T. , Schilling Edward E. , Small Randall L.
Published: February 2008

Chloroplast DNA sequences are a primary source of data for plant molecular systematic studies. A few key papers have provided the molecular systematics community with universal primer pairs for noncoding regions that have dominated the field, namely trnL‐trnF and trnK/matK. These two regions have provided adequate information to resolve species relationships in some taxa, but often provide little resolution at low taxonomic levels. To obtain better phylogenetic resolution, sequence data from these regions are often coupled with other sequence data. Choosing an appropriate cpDNA region for phylogenetic investigation is difficult because of the scarcity of information about the tempo of evolutionary rates among different noncoding cpDNA regions. The focus of this investigation was to determine whether there is any predictable rate heterogeneity among 21 noncoding cpDNA regions identified as phylogenetically useful at low levels. To test for rate heterogeneity among the different cpDNA regions, we used three species from each of 10 groups representing eight major phylogenetic lineages of phanerogams. The results of this study clearly show that a survey using as few as three representative taxa can be predictive of the amount of phylogenetic information offered by a cpDNA region and that rate heterogeneity exists among noncoding cpDNA regions.
Phenotypic plasticity to light competition and herbivory in Chenopodium album (Chenopodiaceae)
Authors: Kurashige Nile S. , Agrawal Anurag A.
Published: February 2008

Competition and herbivory are ubiquitous environmental challenges that affect most plants. We examined the influence of phenotypic responses to either competition or herbivory on the subsequent response of the plants to the other factor. The stem‐elongation response of Chenopodium album to light competition attenuated its resistance to caterpillar herbivory in terms of herbivore mortality, but not in terms of growth of the survivors. Plant responses to herbivory did not affect subsequent responses to light competition. Thus, plants were largely able to express phenotypic plasticity (a proportional increase in the phenotype) following previous exposure to a different environmental factor. Although plants were able to express sequential plasticity, the final phenotype expressed was limited by exposure to previous environmental factors: induced resistance reduced plant height and stem elongation made plants more palatable to herbivores. Phenotypic plasticity in response to competition and herbivory may thus limit the subsequent expression of adaptive phenotypes.
New perspective on the architecture of the Late Devonian arborescent lycopsid Leptophloeum rhombicum (Leptophloeaceae)
Authors: Wang Qi , Geng Bao‐Yin , Dilcher David L.
Published: February 2008

A reinvestigation of the previously described Leptophloeum rhombicum trunk from the Late Devonian (Frasnian) Huangchiateng Formation of Hubei, China provides a new perspective on the architecture of this arborescent lycopsid. It is preserved as a flattened, silicified petrification with an unevenly permineralized primary vasculature and spirally arranged rhombic leaf cushions, which agree with the diagnosis of L. rhombicum Dawson distributed worldwide in the Late Devonian. Taxonomically, this plant should be assigned to its own family and within the order Isoëtales sensu lato. The anatomy, from different levels of the trunk, demonstrates that the ontogeny of the plant may conform to a determinate growth pattern. Combining previous data with current architectural analysis, it suggested that the L. rhombicum tree had a pseudomonopodial branching pattern rather than an iso‐dichotomous branching crown as previously proposed. New reconstruction of the general habit for this tree is given and consists of three major architectural units: a stigmarian rhizomorph, a main trunk, and lateral branches. When these results are considered with recent cladistic work, L. rhombicum may have developed similar growth architecture to some Famennian and Carboniferous arborescent lycopsids. This growth represents one of the archetypal architectures found in the Isoëtales s.l. extending from the early Late Devonian.
Vernalization sensitivity in Arabidopsis thaliana (Brassicaceae): the effects of latitude and FLC variation
Authors: Stinchcombe John R. , Caicedo Ana L. , Hopkins Robin , Mays Charlotte , Boyd Elizabeth W. , Purugganan Michael D. , Schmitt Johanna
Published: February 2008

Latitudinal variation in climate is predicted to select for latitudinal differentiation in sensitivity to the environmental cues that signal plants to flower at the appropriate time for a given climate. In Arabidopsis thaliana, flowering is promoted by exposure to cold temperatures (vernalization), and several vernalization pathway loci are known. To test whether natural variation in vernalization sensitivity could account for a previously observed latitudinal cline in flowering time in A. thaliana, we exposed 21 European accessions to 0, 10, 20, or 30 d of vernalization and observed leaf number at flowering under short days in a growth chamber. We observed a significant latitudinal cline in vernalization sensitivity: southern accessions were more sensitive to vernalization than northern accessions. In addition, accessions that were late flowering in the absence of vernalization were more sensitive to vernalization cues. Allelic variation at the flowering time regulatory gene FLC was not associated with mean vernalization sensitivity, but one allele class exhibited greater variance in vernalization sensitivity.
Phylogenetic relationships, chromosome and breeding system evolution inTurnera(Turneraceae): inferences from its sequence data
Authors: Truyens Simon , Arbo Maria M. , Shore Joel S.
Published: February 2008

Turneraprovides a useful system for exploring two significant evolutionary phenomena—shifts in breeding system (distyly vs. homostyly) and the evolution of polyploids. To explore these, the first molecular phylogeny ofTurnerawas constructed using sequences of the internal transcribed spacer region (ITS) of nuclear ribosomal DNA for 37 taxa. We attempted to resolve the origins of allopolyploid species using single‐strand conformation polymorphism and sequencing of homeologous copies of ITS. Two allohexaploid species possessed putative ITS homeologues (T. velutinaandT. orientalis). A phylogenetic analysis to identify progenitors contributing to the origins of these polyploids was unsuccessful, possibly as a result of concerted evolution of ITS. Breeding system evolution was mapped onto the phylogeny assuming distyly to be ancestral inTurnera. Self‐compatible homostyly appears to have arisen independently at least three times inTurnera; however, we were not able to determine whether there have been independent origins of homostyly among hexaploid species in seriesTurnera. Our phylogenetic analyses suggest that seriesTurnerais monophyletic. Neither seriesMicrophyllaenorAnomalae, however, appear to be monophyletic. Future taxonomic revisions may require new circumscriptions of these latter series.
Variation in “biodiversity value” of peatmoss species inSphagnumsectionAcutifolia(Sphagnaceae)
Authors: Shaw A. Jonathan , Cox Cymon J.
Published: February 2008

Species are the most common currency by which biodiversity is measured, but species are not equivalent in “biodiversity value” because of differences in phylogenetic history and current population processes. Morphologically defined species inSphagnumsectionAcutifolia(Bryophyta) were compared with regard to how phylogenetically distinct each is from its sister species and how much nucleotide variation each encompasses. Comparisons were based on sequence variation at seven nuclear and chloroplast loci. Assignment of collections to morphospecies accounted for about 57–75% of the overall nucleotide variation at the seven loci, but morphospecies differed greatly in how much nucleotide diversity they encompass. In addition, morphospecies varied widely in their genetic distinctiveness, estimated as the length of the stem branch from the most recent common ancestor and numbers of differentially fixed and shared polymorphic nucleotides among taxa. Levels of molecular diversity within morphospecies were not correlated with their degree of isolation. Factors that affected the biodiversity value of species include age, mode of origin, demographic history, and reproductive biology.
Rapid speciation and the evolution of hummingbird pollination in neotropical Costus subgenus Costus (Costaceae): evidence from nrDNA ITS and ETS sequences
Authors: Kay Kathleen M. , Reeves Patrick A. , Olmstead Richard G. , Schemske Douglas W.
Published: February 2008

We estimate phylogenetic relationships and the biogeographic and pollination history of Costus subgenus Costus (Costaceae) using sequence data from the internal and external transcribed spacer (ITS and ETS) regions of 18S–26S nuclear ribosomal DNA. The African members of the subgenus form a series of lineages basal to a monophyletic neotropical species radiation. The neotropical species have large, showy flowers visited by either euglossine bees or hummingbirds. The hummingbird pollination syndrome is supported as a derived character state from the bee pollination syndrome, and we estimate that it has evolved independently seven or more times in the neotropics. A molecular clock approach suggests that diversification of the neotropical clade has been recent and rapid and that it coincides with dramatic climatic and geologic changes, Andean orogeny, and the closing of the Panama isthmus that occurred in the Pliocene and Pleistocene epochs. We propose a scenario for the diversification of Costus, in which rapid floral adaptation in geographic isolation and range shifts in response to environmental changes contribute to reproductive isolation among close relatives. We suggest that these processes may be common in other recently diversified plant lineages centered in Central America or the Northern Andean phytogeographic region.
Chloroplast DNA phylogeny and phylogeography of the North American plums (PrunussubgenusPrunussectionPrunocerasus, Rosaceae)
Authors: Shaw Joey , Small Randall L.
Published: February 2008

The North American plums are a closely related group that are not easily circumscribed, have overlapping morphologies, and are known to hybridize. We previously showed that the North American plums are a closely related, monophyletic group of taxa with little to no cpDNA sequence divergence between taxa. In that study, we came to the unanticipated conclusion that relationships inferred among the taxa contrast sharply with previously defined groups based on morphological characters. Here the aim was to determine if the primary cpDNA haplotypes identified in our earlier study are confined to the taxa in which they were initially observed. The cpDNArpL16intron was sequenced for 207 accessions of the 17 North American plum taxa plusPrunus texana. The results show that many taxa contain more than one of the three primary cpDNA haplotypes. Aside from the results found in sect.Prunocerasus, this study has broader implications for phylogenetics in general. The common practice of choosing a single exemplar to represent a taxon can be profoundly misleading in closely related groups. In hindsight, the possibility existed in our earlier study that we could have chosen a different combination of exemplars, which could have resulted in a different inferred phylogeny.
Evolutionary relationships among Pinus (Pinaceae) subsections inferred from multiple low‐copy nuclear loci
Authors: Syring John , Willyard Ann , Cronn Richard , Liston Aaron
Published: February 2008

Sequence data from nrITS and cpDNA have failed to fully resolve phylogenetic relationships among Pinus species. Four low‐copy nuclear genes, developed from the screening of 73 mapped conifer anchor loci, were sequenced from 12 species representing all subsections. Individual loci do not uniformly support either the nrITS or cpDNA hypotheses and in some cases produce unique topologies. Combined analysis of low‐copy nuclear loci produces a well‐supported subsectional topology of two subgenera, each divided into two sections, congruent with prior hypotheses of deep divergence in Pinus. The placements of P. nelsonii, P. krempfii, and P. contorta have been of continued systematic interest. Results strongly support the placement of P. nelsonii as sister to the remaining members of sect. Parrya, suggest a moderately well‐supported and consistent position of P. krempfii as sister to the remaining members of sect. Quinquefoliae, and are ambiguous about the placement of P. contorta. A successful phylogenetic strategy in Pinus will require many low‐copy nuclear loci that include a high proportion of silent sites and derive from independent linkage groups. The locus screening and evaluation strategy presented here can be broadly applied to facilitate the development of phylogenetic markers from the increasing number of available genomic resources.
Marked genetic divergence among sky island populations ofSedum lanceolatum(Crassulaceae) in the Rocky Mountains
Authors: DeChaine Eric G. , Martin Andrew P.
Published: February 2008

Climate change during the Quaternary played an important role in the differentiation and evolution of plants. A prevailing hypothesis is that alpine and arctic species survived glacial periods in refugia at the periphery of glaciers. Though the Rocky Mountains, south of the southernmost extent of continental ice, served as an important glacial refuge, little is known about how climate cycles influenced populations within this region. We inferred the phylogeography ofSedum lanceolatum(Crassulaceae) within the Rocky Mountain refugium to assess how this high‐elevation plant responded to glacial cycles. We sequenced 884 base pairs (bp) of cpDNA intergenic spacers (tRNA‐L to tRNA‐F and tRNA‐S to tRNA‐G) for 333 individuals from 18 alpine populations. Our highly variable markers allowed us to infer that populations persisted across the latitudinal range throughout the climate cycles, exhibited significant genetic structure, and experienced cycles of range expansion and fragmentation. Genetic differentiation inS. lanceolatumwas most likely a product of short‐distance elevational migration in response to climate change, low seed dispersal, and vegetative reproduction. To the extent thatSedumis a good model system, paleoclimatic cycles were probably a major factor preserving genetic variation and promoting divergence in high‐elevation flora of the Rocky Mountains.
Pollen and resource limitation in a gynodioecious species
Authors: Asikainen Eija , Mutikainen Pia
Published: February 2008

Differences between plant sex morphs in pollen or resource availability may affect their relative fitness and thereby the sex ratio of dimorphic species. In gynodioecious species, in which hermaphroditic and female plants coexist, a variety of factors (e.g., hermaphrodite self‐fertility or rarity or pollinator discrimination against females) might be expected to lead to stronger pollen limitation in females than in hermaphrodites. On the other hand, females have been found to be superior compared to hermaphrodites in low‐nutrient conditions. The effects of supplemental hand‐pollination and resource addition on the reproductive output of the self‐fertile gynodioecious perennial Geranium sylvaticum (Geraniaceae) were tested for several populations that differ in their female frequency (4.4–23.0%). Both pollen and resource availability limited fruit set and the number of seeds produced per plant; however, seed set (i.e., the number of seeds produced per fruit) was limited only by resources. Because pollen limitation in females did not correlate with female frequency, our results suggest that pollen limitation in females does not depend on the frequency of the pollen‐producing hermaphrodites. Furthermore, because pollen and resource availability limited reproductive output of both sex morphs, these factors may not contribute significantly to maintenance and evolution of gynodioecy in G. sylvaticum.
Inflorescence, spikelet, and floral development in Panicum maximum and Urochloa plantaginea (Poaceae)
Authors: Reinheimer Renata , Pozner Raúl , Vegetti Abelardo C.
Published: February 2008

Inflorescence development in Panicum maximum and Urochloa plantaginea was comparatively studied with scanning electron and light microscopy to test the transfer of P. maximum to Urochloa and to look for developmental features applicable to future cladistic studies of the phosphoenol pyruvate carboxykinase (PCK) subtype of C4 photosynthesis clade (P. maximum and some species of Brachiaria, Chaetium, Eriochloa, Melinis, and Urochloa). Eleven developmental features not discernable in the mature inflorescence were found: direction of branch differentiation; origins of primary branches; apical vs. intercalary development of the main axis; direction of spikelet differentiation; direction of glume, lemma and palea differentiation; position of the lower glume (in some cases); size of the floret meristem; pattern of distal floret development; pattern of gynoecium abortion; differential pollen development between proximal and distal floret; and glume elongation. Inflorescence homologies between P. maximum and U. plantaginea are also clarified. Panicum maximum and U. plantaginea differ not only in their mature inflorescence structure but also in eight fundamental developmental features that exclude P. maximum from Urochloa. The following developmental events are related to sex expression: size of floret meristem, gynoecium abortion, pollen development delay in the proximal floret, glume elongation and basipetal floret maturation at anthesis.
Molecular phylogeny of Incarvillea (Bignoniaceae) based on ITS and \[bu100\]TRN\[cmL‐Fsequences
Authors: Chen Shaotian , Guan Kaiyun , Zhou Zhekun , Olmstead Richard , Cronk Quentin
Published: February 2008

Incarvillea is a herbaceous and temperate member of Bignoniaceae, previously divided into four subgenera, Niedzwedzkia, Amphicome, Incarvillea, and Pteroscleris. Niedzwedzkia and Amphicome have in the past been treated as independent genera. Different relationships have been proposed for the four subgenera. Here, maximum parsimony analysis using ITS and trnL‐F sequences resulted in similar trees and showed that the genus is monophyletic. Analysis of the combined data resulted in a single tree with five major clades highly supported and well resolved. The relationships of the five major clades are (subgenus Niedzwedzkia (Incarvillea olgae (subgenus Amphicome (subgenus Incarvillea, subgenus Pteroscleris)))). All four subgenera are well supported for monophyly, with the exception of subgenus Incarvillea, represented here by I. sinensis and I. olgae. Incarvillea olgae is not closely related to I. sinensis, a conclusion supported by morphology. The two basal monotypic subgenera are found in Central Asia. The most species‐rich subgenus, Pteroscleris, has 10 species in the Himalaya‐Hengduan Mountains and may have dispersed early from central Asia to eastern Asia. Short branch lengths on the molecular trees within Pteroscleris suggest a recent and rapid radiation of this rosette‐forming subgenus, perhaps connected with the uplift of the Himalaya‐Hengduan massif.
Genetic diversity in Chihuahuan Desert populations of creosotebush (Zygophyllaceae:Larrea tridentata)
Authors: Duran Kristy L. , Lowrey Timothy K. , Parmenter Robert R. , Lewis Paul O.
Published: February 2008

We examined isozyme variation in the dominant Chihuahuan Desert shrub,Larrea tridentata(creosotebush), to determine the genetic variation within and among populations, the biogeographic relationships of populations, and the potential inbreeding in the species. We surveyed 17 populations consisting of 20 to 50 individuals per population along a 1600‐km north–south transect across the Chihuahuan Desert. The southernmost population was near Villa Hidalgo, Mexico, and the northernmost near Isleta Pueblo, New Mexico. All 12 isozyme loci examined were polymorphic (Ht= 0.416), with up to nine alleles per locus. Despite high levels of variation, we detected moderate inbreeding inL. tridentatapopulations. Most variation was found within rather than among populations (GST= 0.118). Furthermore, recently established populations in the northern limits of the Chihuahuan Desert did not show decreased levels of genetic variation (Ho= 0.336). A significant correlation was found between pairwise genetic and geographic distances (r= 0.305).Larrea tridentatashowed and continues to show a massive range expansion into the arid and semi‐arid regions of the American Southwest, but as shown by the high genetic variation, this expansion took place as a wave, rather than a series of founder events.
Phenotypic plasticity in vegetative and reproductive traits in an invasive weed, Lythrum salicaria (Lythraceae), in response to soil moisture
Authors: Mal Tarun K. , Lovett‐Doust Jon
Published: February 2008

In colonizing species, high phenotypic plasticity can contribute to survival and propagation in heterogenous adventive environments, and it has been suggested as a predictor of invasiveness. Observation of natural populations of an invasive species, Lythrum salicaria salicaria, indicated extensive variation in its growth and reproductive traits. Phenotypic plasticity of different life history traits of L. salicaria was investigated using vegetative clones of each of 12 genotypes from one population in Ontario, Canada. We chose soil moisture as the treatment factor because of its importance in wetland species and raised all 12 genotypes in each of four soil moisture treatments. We examined an array of vegetative and reproductive traits, including root and shoot mass, shoot and inflorescence length, total seed set, floral mass, and morphometric variables. All observed vegetative as well as reproductive traits demonstrated significant phenotypic plasticity in response to soil moisture treatment. Even the stigma–anther separation involved significant genotype by environment interactions, suggesting that soil moisture may modify the relative positions of anthers and stigma. Compared to vegetative traits, most reproductive traits demonstrated crossing reaction norms, implying that the average differences in those traits among genotypes vary with the environment maintaining the genetic variation in a population.
Reproduction and progeny of Silene latifolia (Caryophyllaceae) as affected by atmospheric CO2 concentration
Authors: Wang Xianzhong
Published: February 2008

Sexual dimorphism in plants has been known for over two millennia. However, little is known about how male and female reproduction of dioecious species will respond to anthropogenic environmental perturbations. Using growth chambers, the effects of CO2 enrichment on male and female reproduction in Silene latifolia were examined and whether parental CO2 environment affected progeny germination and sex ratio. Reproduction of male and female S. latifolia was enhanced by a similar magnitude at elevated CO2. Over the growing season, males produced 16 times as many flowers as females did fruits per plant, but no difference in reproductive biomass between genders was observed at ambient or elevated CO2. Germination of seeds produced by plants grown at different CO2 concentrations was significantly different. Female seeds from higher CO2‐grown plants tended to emerge earlier than those from ambient‐CO2‐grown plants, but emergence of male seeds was little affected. Overall, seeds from elevated‐CO2‐grown plants had 20% higher germination and were more female‐biased than those from ambient‐CO2‐grown plants. Because of the enhanced reproduction and more female‐biased progeny under elevated CO2, the population structure of this cosmopolitan weedy species will likely be altered in a future environment.
Genetic diversity and structure of natural and managed populations of Cedrus atlantica (Pinaceae) assessed using random amplified polymorphic DNA
Authors: Renau‐Morata Begoña , Nebauer Sergio G. , Sales Ester , Allainguillaume Joel , Caligari Peter , Segura Juan
Published: February 2008

Cedrus atlantica (Pinaceae) is a large and exceptionally long‐lived conifer native to the Rif and Atlas Mountains of North Africa. To assess levels and patterns of genetic diversity of this species, samples were obtained throughout the natural range in Morocco and from a forest plantation in Arbúcies, Girona (Spain) and analyzed using RAPD markers. Within‐population genetic diversity was high and comparable to that revealed by isozymes. Managed populations harbored levels of genetic variation similar to those found in their natural counterparts. Genotypic analyses of molecular variance (AMOVA) found that most variation was within populations, but significant differentiation was also found between populations, particularly in Morocco. Bayesian estimates of FST corroborated the AMOVA partitioning and provided evidence for population differentiation in C. atlantica. Both distance‐ and Bayesian‐based clustering methods revealed that Moroccan populations comprise two genetically distinct groups. Within each group, estimates of population differentiation were close to those previously reported in other gymnosperms. These results are interpreted in the context of the postglacial history of the species and human impact. The high degree of among‐group differentiation recorded here highlights the need for additional conservation measures for some Moroccan populations of C. atlantica.
Are flower‐visiting ants mutualists or antagonists? A study in a gynodioecious wild strawberry
Authors: Ashman Tia‐Lynn , King Emiley A.
Published: February 2008

Ants are common flower visitors, but their effects on plant reproductive fitness have not often been assessed. Flower‐visiting ants were studied to determine whether they are antagonists or mutualists and whether they could influence floral or breeding system evolution in gynodioecious wild strawberry (Fragaria virginiana). Ant and flying pollinator (bees/flies) access to plants was manipulated, and visitation, fruit, and seed set were assessed. Ants visited flowers of hermaphrodites more often than those of females when bees and flies were excluded, but visited the sex morphs equally when they were present. Insect class did not influence fruit or seed set of hermaphrodites. In contrast, ants had both positive and negative effects on seed set in females. Females visited only by ants had 90% of the seed set of those visited only by bees/flies, and their seed set increased with ant visitation. The spatial pattern of seed set, however, suggests that ants may also damage pistils. Lastly, in contrast to bees and flies, ants failed to increase visitation with floral display size, suggesting that ant presence at flowers could reduce selection on this attractive trait. Findings suggest that when in high abundance, flower‐visiting ants could affect breeding system and floral evolution in this gynodioecious plant.
Evolutionary and ecological correlates of early seedling morphology in East African trees and shrubs
Authors: Zanne Amy E. , Chapman Colin A. , Kitajima Kaoru
Published: February 2008

Seed size and cotyledon morphology are two key juvenile traits that have evolved in response to changes in plant species life‐history strategies and habitat associations. Correlations of these traits with each other and with other juvenile traits were examined for 70 species of trees and shrubs in Kibale National Park, Uganda. Although species with photosynthetic cotyledons were more abundant than in other tropical floras, both univariate and multivariate analyses supported trait associations expected from the literature. Trait values varied continuously across species, yet mean trait values differed significantly among habitat association types. Species with large seeds, large seedlings, thick storage cotyledons, slow germination, large‐stature adults, and dispersal by large animals were common in forest and gap habitats. An opposite suite of traits was common in open habitats (grassland and edge). Analyses incorporating phylogeny (independent contrasts and omnibus tests) confirmed that these suites of traits showed correlated evolution. Cotyledon functional morphology yielded a strong phylogenetic signal, while seed mass was labile. Nevertheless, contingent change tests found that evolutionary change from photosynthetic to reserve cotyledons was more likely when disperser and perhaps seed size of ancestral species were already large, suggesting a strong interdependency among these traits.
Genetic and clonal diversity of two cattail species, Typha latifolia and T. angustifolia (Typhaceae), from Ukraine
Authors: Tsyusko Olga V. , Smith Michael H. , Sharitz Rebecca R. , Glenn Travis C.
Published: February 2008

Genetic and clonal diversity vary between two closely related cattail species (Typha angustifolia and T. latifolia) from Ukraine. This diversity was calculated from microsatellite data. Forty‐eight percent of the total variation was partitioned between species, which formed distinct clusters in a dendrogram with no indication of hybrid populations. Typha angustifolia had higher heterozygosity at the species (Hes = 0.66) and population (Hep = 0.49) levels than did T. latifolia (Hes = 0.37 and Hep = 0.29, respectively). The higher number of alleles in T. angustifolia may be indicative of larger effective population sizes due to its higher seed production. Clonal diversity of T. angustifolia was lower than that of T. latifolia (Ng/Nr = 0.40 and 0.61, Simpson's D = 0.82 and 0.94, respectively). Correlations between clonal and genetic diversity were higher for T. latifolia than T. angustifolia, suggesting that the importance of factors and their interactions affecting this relationship are different for the two species. Latitudinal and longitudinal trends were not observed in either species despite the large sampling area. Population differentiation was relatively high with FST of 0.24 and 0.29 for T. angustifolia and T. latifolia, respectively. Weak isolation by distance was observed for T. latifolia but not for T. angustifolia.
Systematics and biogeography ofLathyrus(Leguminosae) based on internal transcribed spacer and cpDNA sequence data
Authors: Kenicer Gregory J. , Kajita Tadashi , Pennington R. Toby , Murata Jin
Published: February 2008

Lathyrus(Leguminosae; Papilionoideae) is the largest genus in tribe Fabeae and exhibits an intriguing extratropical distribution. We studied the systematics and biogeography ofLathyrususing sequence data, from accessions representing 53 species, for the internal transcribed spacer plus 5.8S‐coding region of nuclear ribosomal DNA as well as thetrnL‐FandtrnS‐Gregions of chloroplast DNA. Our results generally supported recent morphology‐based classifications, resolving clades corresponding to sectionsLathyrusandLathyrostylis, but question the monophyly of the large, widespread sectionOrobussensu Asmussen and Liston. SectionsOrobus,Aphaca, andPratensisform a predominantly northern Eurasian–New World clade. Within this clade, the North American and eastern Eurasian species, including both Holarctic species (L. palustrisandL. japonicus), form a transberingian clade of relatively recent origin and diversification. The South AmericanNotolathyrusgroup is distant from this transberingian lineage and should be reinstated as a distinct section within the northern Eurasian–New World clade. TheNotolathyruslineage reached the New World most probably through long‐distance dispersal from Eurasia. The remaining sections in the genus are centered on the Mediterranean region.
Duplication of floral regulatory genes in the Lamiales
Authors: Aagaard Jan E. , Olmstead Richard G. , Willis John H. , Phillips Patrick C.
Published: February 2008

Duplication of some floral regulatory genes has occurred repeatedly in angiosperms, whereas others are thought to be single‐copy in most lineages. We selected three genes that interact in a pathway regulating floral development conserved among higher tricolpates (LFY/FLO, UFO/FIM, and AP3/DEF) and screened for copy number among families of Lamiales that are closely related to the model species Antirrhinum majus. We show that two of three genes have duplicated at least twice in the Lamiales. Phylogenetic analyses of paralogs suggest that an ancient whole genome duplication shared among many families of Lamiales occurred after the ancestor of these families diverged from the lineage leading to Veronicaceae (including the single‐copy species A. majus). Duplication is consistent with previous patterns among angiosperm lineages for AP3/DEF, but this is the first report of functional duplicate copies of LFY/FLO outside of tetraploid species. We propose Lamiales taxa will be good models for understanding mechanisms of duplicate gene preservation and how floral regulatory genes may contribute to morphological diversity.
A phylogenetic reappraisal of the Peltophorum group (Caesalpinieae: Leguminosae) based on the chloroplast trnL‐F, rbcL and rps16 sequence data
Authors: Haston Elspeth M. , Lewis Gwilym P. , Hawkins Julie A.
Published: February 2008

The monophyly of the Peltophorum group, one of nine informal groups recognized by Polhill in the Caesalpinieae, was tested using sequence data from the trnL‐F, rbcL, and rps16 regions of the chloroplast genome. Exemplars were included from all 16 genera of the Peltophorum group, and from 15 genera representing seven of the other eight informal groups in the tribe. The data were analyzed separately and in combined analyses using parsimony and Bayesian methods. The analysis method had little effect on the topology of well‐supported relationships. The molecular data recovered a generally well‐supported phylogeny with many intergeneric relationships resolved. Results show that the Peltophorum group as currently delimited is polyphyletic, but that eight genera plus one undescribed genus form a core Peltophorum group, which is referred to here as the Peltophorum group sensu stricto. These genera are Bussea, Conzattia, Colvillea, Delonix, Heteroflorum (inedit.), Lemuropisum, Parkinsonia, Peltophorum, and Schizolobium. The remaining eight genera of the Peltophorum group s.l. are distributed across the Caesalpinieae. Morphological support for the redelimited Peltophorum group and the other recovered clades was assessed, and no unique synapomorphy was found for the Peltophorum group s.s. A proposal for the reclassification of the Peltophorum group s.l. is presented.
Evolution of reproductive structures in grasses (Poaceae) inferred by sister‐group comparison with their putative closest living relatives, Ecdeiocoleaceae
Authors: Rudall Paula J. , Stuppy Wolfgang , Cunniff Jennifer , Kellogg Elizabeth A. , Briggs Barbara G.
Published: February 2008

Despite much recent activity in the phylogeny and developmental genetics of grasses, the enigmatic homologies of their reproductive structures remain largely unresolved, partly because their highly derived morphology has resulted in a unique associated terminology. Outstanding questions include whether grass lodicules and stamens are derived from a single perianth or stamen whorl, respectively, whether the grass caryopsis is homologous with a nut, and how the scutellum evolved. We investigated the reproductive structures of the putative sister group of grasses, the southwestern Australian family Ecdeiocoleaceae, which includes two genera, Ecdeiocolea and Georgeantha. The zygomorphic arrangement of the four (rather than six) stamens in male flowers of Ecdeiocolea indicates that they may represent three outer stamens plus the adaxial inner stamen. Within Ecdeiocoleaceae, characters such as the highly unusual nucellus structure of Ecdeiocolea are autapomorphic. Sister‐group comparisons indicate that some characteristic grass features, notably the scutellum, do not occur in their putative closest relatives and that more data are needed on early‐diverging grass genera to resolve these issues. The grass caryopsis could represent one end of a transformation series embodied by the reduced gynoecial structure and indehiscent fruit of other Poales such as Flagellaria, Joinvillea, and Ecdeiocolea.
Post‐floral perianth functionality: contribution of persistent sepals to seed development in Helleborus foetidus (Ranunculaceae)
Authors: Herrera Carlos M.
Published: February 2008

The perianth persists after flowering in many plants, yet its post‐floral functionality has been little investigated, and the few studies available provide ambiguous evidence. This paper tests the hypothesis that the green persistent sepals of the perennial herb, Helleborus foetidus, contribute to the plant's fitness by enhancing seed number and/or size. Post‐floral contribution of the calyx to fruit and seed development was evaluated by manipulating sepal number and measuring the effect on follicle size, seed set, seeds per follicle, and mean seed mass. The allometric relationship between calyx size and follicle mass was examined for flower buds, open flowers, and immature fruits differing in follicle number. Calyx manipulation had no significant effect on follicle size, seed set, or number of seeds per follicle, but it did have a significant influence on the size of individual seeds. Calyx size and mean seed mass were positively, linearly related. The calyx mass/seed number ratio declined with increasing number of follicles per fruit. The persistent sepals of Helleborus do contribute resources to the development of seeds, although there is not evidence of post‐floral allometric adjustment of the calyx mass/follicle number ratio that could compensate for variations in seed number per fruit.
Wind pollination, sexual dimorphism, and changes in floral traits of Schiedea (Caryophyllaceae)
Authors: Golonka Annette M. , Sakai Ann K. , Weller Stephen G.
Published: February 2008

Both changes in sex allocation and pollination mode may promote the separation of sexes in plant populations. Simultaneous evolution of wind pollination and dimorphism has occurred in Schiedea, where species with different female frequencies provide an opportunity to observe the effect of wind pollination on sex allocation and floral morphology. Differences among species in the ratio of anther to ovary volume were not the result of sex allocation trade‐offs, but instead resulted from production of vestigial stamens in females; there were no changes in ovary volume in males and hermaphrodites (MH) of dimorphic species. Relative to hermaphroditic species, dimorphic species had more condensed inflorescences, a pattern often associated with wind pollination. Within dimorphic species, MH had longer filament lengths than females, and females had longer stigmas than MHs. These traits are characteristic of wind pollination, but there was no relationship between the degree of sexual dimorphism and female frequency. Ovary volume and ovule number and size had positive phenotypic correlations between females and MH of dimorphic species, making sex specialization more difficult. In dimorphic Schiedea species, selection for wind pollination may have a greater effect on floral traits than trade‐offs in allocation between male and female function.
High abundance of dioecious plants in a tropical coastal vegetation
Authors: Matallana Gloria , Wendt Tânia , Araujo Dorothy S. D. , Scarano Fábio R.
Published: February 2008

We examined the frequency of hermaphroditic, monoecious, and dioecious species of angiosperms in restinga (sandy coastal plain) vegetation in SE Brazil. The study site was a vegetation mosaic comprising nine plant formations, ranging from open types to forest. Dioecy (14% of 566 species) was similar to other tropical vegetations and strongly associated with woodiness and entomophily. However, more interestingly, there was an exceptionally high percentage (35%) of dioecious species among the dominant woody plants. This pattern has not been previously reported, and we discuss the extent to which it is ecologically driven. We argue that the high abundance of dioecious plants in this resource‐poor environment can be attributed to ecological traits related to long‐distance dispersal, ecological vigor, and possibly, vegetative reproduction.
Developmental programmed cell death in primary roots of Sonoran Desert Cactaceae
Authors: Shishkova Svetlana , Dubrovsky Joseph G.
Published: February 2008

Primary roots of two species of Sonoran Desert Cactaceae, Stenocereus gummosus and Pachycereus pringlei, have a determinate pattern of growth: meristematic cells divide only for a limited time and then differentiate. Detecting DNA fragmentation by terminal deoxynucleotide transferase‐mediated dUTP nick‐end labeling (TUNEL), we have shown that programmed cell death (PCD) was not involved in meristem exhaustion. However, we found TUNEL‐positive nuclei in the root hair and root cap cells of both species. Programmed cell death in root hair cells has not been previously reported, and the pattern of PCD events in the root cap differed from that described earlier. These data suggest that in the studied Cactaceae, PCD is involved in developmental adaptations related to the formation of a compact root system important for rapid seedling establishment in a desert environment. Participation of PCD in developmental loss of the root cap and in root hair renovation proposed in the current study implicates an evolutionary conserved link between PCD and differentiation processes in plants.
Species richness and distribution of ferns along an elevational gradient in Costa Rica
Authors: Watkins James E. , Cardelús Catherine , Colwell Robert K. , Moran Robbin C.
Published: February 2008

To better understand changes in the distribution and diversity within plant functional types along an elevational gradient and the potential mechanisms driving such changes, we studied species richness of ferns at six elevations along a forested elevational gradient in Costa Rica, from La Selva Biological Station at 30 m a.s.l. up the slopes of Volcán Barva to 2960 m a.s.l. Among the samples from all the sites combined, we found 264 species from 60 genera. Sixty‐nine species were terrestrial, 113 were canopy epiphytes, and 121 were low‐trunk epiphytes. Only one species occupied both canopy and terrestrial habitats at any of the study sites. Overlap of canopy and low‐trunk species composition was relatively low (18%), and lower still was the overlap of terrestrial and low‐trunk species (12%). Total species richness peaked at the 1000‐m site for canopy and low‐trunk epiphytic species. In contrast, the richness of terrestrial species rose to a mid‐elevation maximum and remained relatively constant at higher elevations. In an effort to explain elevational patterns of species richness, we examined mean annual rainfall and temperature, light intensities in the canopy and at ground level, and the mid‐domain effect. Of the explanatory factors examined, the mid‐domain effect accounted for most of the elevational pattern. We found little evidence that environmental gradients drive patterns of fern species richness on this spatial scale.
Effects of insect‐resistance transgenes on fecundity in rice (Oryza sativa, Poaceae): a test for underlying costs
Authors: Chen Liang‐Yan , Snow Allison A. , Wang Feng , Lu Bao‐Rong
Published: February 2008

Understanding the balance between yield benefits and possible underlying yield costs that are associated with transgenic cultivars is useful for evaluating crop performance and the fitness of crop‐wild hybrid progeny, but few researchers have tested for such costs under rigorous experimental conditions. We examined shifts in net costs and benefits of insect‐resistance transgenes in cultivated rice (Oryza sativa) using two levels of insect pressure (low vs. moderate) and two types of competition (pure vs. mixed lines). We compared the growth and fecundity of potted rice plants from three transgenic lines, Bt, CpTI, and Bt/CpTI, relative to isogenic control plants at outdoor locations in Fuzhou, China. Net yield costs were detected, but only in Bt/CpTI plants in mixed‐line competition with low insect pressure. These plants produced 16% fewer tillers, 6% smaller seeds, and 30% fewer seeds than competing control plants. Under moderate insect pressure, Bt and Bt/CpTI plants produced 36–65% more seeds than controls, but the net benefit for Bt/CpTI plants disappeared in mixed‐line competition pots. To our knowledge, this is the first report of yield costs in cultivars with transgenic insect resistance. Our results suggest that these costs may be negligible in monotypic rice fields, especially when target insects are abundant.
Biomimetics and technical textiles: solving engineering problems with the help of nature's wisdom
Authors: Milwich Markus , Speck Thomas , Speck Olga , Stegmaier Thomas , Planck Heinrich
Published: February 2008

The significance of inspiration from nature for technical textiles and for fibrous composite materials is demonstrated by examples of already existing technical solutions that either parallel biology or are indeed inspired by biological models. The two different basic types of biomimetic approaches are briefly presented and discussed for the “technical plant stem.” The technical plant stem is a biomimetic product inspired by a variety of structural and functional properties found in different plants. The most important botanical templates are the stems of the giant reed (Arundo donax, Poaceae) and of the Dutch rush (Equisetum hyemale, Equisetaceae). After analysis of the structural and mechanical properties of these plants, the physical principles have been deduced and abstracted and finally transferred to technical applications. Modern computer‐controlled fabrication methods for producing technical textiles and for structuring the embedding matrix of compound materials render unique possibilities for transferring the complex structures found in plants, which often are optimized on several hierarchical levels, into technical applications. This process is detailed for the technical plant stem, a biomimetic, lightweight, fibrous composite material based on technical textiles with optimized mechanical properties and a gradient structure.