bluuebunny/crossref_metadata_2025 huggingface dataset:
Architectural effects mimic floral sexual dimorphism in Solanum (Solanaceae)
Authors: Diggle Pamela K. , Miller Jill S.
Published: February 2008

Factors underlying apparent floral sexual dimorphism were examined in six species of andromonoecious Solanum section Lasiocarpa (Solanaceae). Both multivariate and univariate analyses show that hermaphroditic flowers are significantly larger than staminate flowers for all features measured. Thus, flowers could be characterized as sexually size dimorphic. However, when size variation due to flower position (architecture) is controlled experimentally, differences between the floral genders for the nongynoecial characters disappear; there is no difference in corolla or androecium size. Staminate flowers appear to be generally smaller than hermaphroditic flowers, not because of any difference related to primary sexual function, but because they tend to occur in the distal regions of each inflorescence. In contrast, significant differences between hermaphroditic and staminate flowers for primary female traits (ovary, style, and stigma) remain after controlling for position: the two floral types are truly dimorphic for these characters. We show that consideration of architectural effects can direct and refine hypotheses concerning the evolution of andromonoecy. More generally, if architectural effects on flower size are common among taxa with unisexual flowers, then these effects may contribute to the common perception of size dimorphism in taxa with unisexual flowers.
Intraspecific diversification in North AmericanBoechera stricta(=Arabis drummondii),Boechera×divaricarpa, andBoechera holboellii(Brassicaceae) inferred from nuclear and chloroplast molecular markers—an integrative approach
Authors: Dobeš Christoph , Mitchell‐Olds Thomas , Koch Marcus A.
Published: February 2008

We performed a combined evolutionary analysis of North AmericanBoechera stricta,Boechera holboellii, and their hybridBoechera ×divaricarpausing information on ploidy level estimators, allelic microsatellite variation, noncoding regions of the plastidic genome (cpDNA), and sequences of the internal transcribed spacers 1 and 2 of the nuclear ribosomal DNA (ITS). Somatic ploidy levels of herbarium specimens were estimated based on comparison of pollen size and the number of alleles per locus at seven microsatellites. Results indicate thatB. strictaandB. holboelliiare genetically distinct from each other, although we also find evidence for occasional introgression between both parental species. Microsatellite patterns forB. strictafrom northeastern North America are genetically distinct from western populations, suggesting isolation in glacial refugia along the southeastern margin of the continuous ice shield. Microsatellites supported recent origin ofB. ×divaricarpa. Correspondence of nrDNA with cpDNA genetic variation for the majority of diploidB. holboelliiaccessions suggests a basal, sexual evolutionary unit within a polymorphicB. holboelliigroup. Hybridization of genetically distinct lineage(s) evidently played an important role in the establishment of polyploidB. holboellii. Frequency of polyploidB. holboelliiis substantially higher in the southern United States. This trend corresponds to a southerly distribution of derived chloroplast haplotypes, suggesting an evolutionary advantage of polyploidy and associated apomixis in the colonization of the Sierra Nevada and the Southern Rocky Mountains.
Phosphatized multicellular algae in the Neoproterozoic Doushantuo Formation, China, and the early evolution of florideophyte red algae
Authors: Xiao Shuhai , Knoll Andrew H. , Yuan Xunlai , Pueschel Curt M.
Published: February 2008

Phosphatic sediments of the Late Neoproterozoic (ca. 600 million years old [Myr]) Doushantuo Formation at Weng'an, South China, contain fossils of multicellular algae preserved in anatomical detail. As revealed by light microscopy and scanning electron microscopy, these fossils include both simple pseudoparenchymatous thalli with apical growth but no cortex–medulla differentiation and more complex thalli characterized by cortex–medulla differentiation and structures interpretable as carposporophytes, suggesting a multiphasic life cycle. Simple pseudoparenchymatous thalli, represented by Wengania, Gremiphyca, and Thallophycoides, are interpreted as stem group florideophytes. In contrast, complex pseudoparenchymatous thalli, such as Thallophyca and Paramecia, compare more closely to fossil and living corallinaleans than to other florideophyte orders, although they also differ in some important aspects (e.g., lack of biocalcification). These more complex thalli are interpreted as early stem group corallinaleans that diverged before Paleozoic stem groups such as Arenigiphyllum, Petrophyton, Graticula, and Archaeolithophyllum. This phylogenetic interpretation implies that (1) the phylogenetic divergence between the Florideophyceae and its sister group, the Bangiales, must have taken place before Doushantuo time—an inference supported by the occurrence of bangialean fossils in Mesoproterozoic rocks; (2) the initial diversification of the florideophytes occurred no later than the Doushantuo time; and (3) the corallinalean clade had a “soft” (uncalcified) evolutionary history in the Neoproterozoic before evolving biocalcification in the Paleozoic and undergoing crown group diversification in the Mesozoic.
Molecular evidence for bicontinental hybridogenous genomic constitution in Lepidium sensu stricto (Brassicaceae) species from Australia and New Zealand
Authors: Mummenhoff Klaus , Linder Peter , Friesen Nikolai , Bowman John L. , Lee Ji‐Young , Franzke Andreas
Published: February 2008

Lepidium sensu stricto (s.s.) (Brassicaceae) (ca. 150 species) is distributed worldwide with endemic species on every continent. It is represented in Australia and New Zealand by 19 and seven native species, respectively. In the present study we used a nuclear ribosomal internal transcribed spacer (ITS) phylogeny in comparison with a cpDNA phylogeny to unravel the origin of Australian/New Zealand species. Although phylogenetic relationships within Lepidium s.s. were not fully resolved, the cpDNA data were in agreement with a Californian origin of Lepidium species from Australia/New Zealand. Strongly conflicting signals between the cp‐ and nuclear DNA phylogenetic analysis clearly indicated hybridogenous genomic constitution of Australian Lepidium s.s. species: All 18 studied Australian/New Zealand Lepidium s.s. species examined shared a Californian cpDNA type. While eleven Australian/New Zealand species appeared to harbor a Californian ITS type, a group of seven species shared a South African ITS type. This pattern is most likely explained by two trans‐oceanic dispersals of Lepidium from California and Africa to Australia/New Zealand and subsequent hybridization followed by homogenization of the ribosomal DNA either to the Californian or South African ITS type in the two different lineages. Calibration of our molecular trees indicates a Pliocene/Pleistocene origin of Lepidium in Australia/New Zealand. Low levels of cpDNA and ITS sequence divergence and unresolved topologies within Australian/New Zealand species suggest a rapid and recent radiation of Lepidium after the hybridization event. This coincides with dramatic climatic changes in that geological epoch shaping the composition of the vegetation.
Morphological and RAPD analysis of hybridization betweenQuercus affinisandQ. laurina(fagaceae), two Mexican red oaks
Authors: González‐Rodríguez Antonio , Arias Dulce M. , Valencia Susana , Oyama Ken
Published: February 2008

Quercus affinisandQ. laurinaare two closely related Mexican red oaks with partially overlapping distributions. Within the area of overlap, there are localities where morphological intergradation occurs. A previous hypothesis explained this pattern as a result of secondary contact between the two species, followed by hybridization and introgression. This possibility was analyzed here by examining foliar and genetic variation in 16 localities situated along a macrogeographic gradient, which included morphologically representative populations of both species and populations from within the area of overlap. Maximum‐likelihood hybrid index scores calculated from nine semi‐diagnostic RAPD markers indicated a shift in the genetic composition of populations from one species to the other along the macrogeographic gradient, with genetically intermediate populations situated in the area of overlap. Foliar variation followed a partially congruent pattern, butQ. laurina‐like morphology predominated in some of the genetically intermediate populations. There were several instances of correlated frequency changeovers of single RAPD markers and morphological characters along the macrogeographic gradient and a few cases of markedly parallel patterns between markers. The results were interpreted as consistent with a hypothesis of secondary contact between the two oak species that has resulted in some differential introgression among markers.
Chromosome numbers and karyotype evolution in holoparasitic Orobanche (Orobanchaceae) and related genera
Authors: Schneeweiss Gerald M. , Palomeque Teresa , Colwell Alison E. , Weiss‐Schneeweiss Hanna
Published: February 2008

Chromosome numbers and karyotypes of species of Orobanche, Cistanche, and Diphelypaea (Orobanchaceae) were investigated, and 108 chromosome counts of 53 taxa, 19 counted for the first time, are presented with a thorough compilation of previously published data. Additionally, karyotypes of representatives of these genera, including Orobanche sects. Orobanche and Trionychon, are reported. Cistanche (x = 20) has large meta‐ to submetacentric chromosomes, while those of Diphelypaea (x = 19) are medium‐sized submeta‐ to acrocentrics. Within three analyzed sections of Orobanche, sects. Myzorrhiza (x = 24) and Trionychon (x = 12) possess medium‐sized submeta‐ to acrocentrics, while sect. Orobanche (x = 19) has small, mostly meta‐ to submetacentric, chromosomes. Polyploidy is unevenly distributed in Orobanche and restricted to a few lineages, e.g., O. sect. Myzorrhiza or Orobanche gracilis and its relatives (sect. Orobanche). The distribution of basic chromosome numbers supports the groups found by molecular phylogenetic analyses: Cistanche has x = 20, the Orobanche‐group (Orobanche sect. Orobanche, Diphelypaea) has x = 19, and the Phelipanche‐group (Orobanche sects. Gymnocaulis, Myzorrhiza, Trionychon) has x = 12, 24. A model of chromosome number evolution in Orobanche and related genera is presented: from two ancestral base numbers, xh = 5 and xh = 6, independent polyploidizations led to x = 20 (Cistanche) and (after dysploidization) x = 19 (Orobanche‐group) and to x = 12 and x = 24 (Phelipanche‐group), respectively.
Anatomically preserved Liquidambar (Altingiaceae) from the middle Miocene of Yakima Canyon, Washington state, USA, and its biogeographic implications
Authors: Pigg Kathleen B. , Ickert‐Bond Stefanie M. , Wen Jun
Published: February 2008

Liquidambar changii Pigg, Ickert‐Bond & Wen sp. nov. (Altingiaceae) is established for anatomically preserved, middle Miocene infructescences from Yakima Canyon, Washington, USA. Specimens are spherical, ∼2.5 cm in diameter, and have ∼25–30 tightly packed, bilocular fruits per head. Fruits are 3.4–4.7 mm wide × 2.6–3.5 mm long and wedge shaped, fused at the base, and free distally. Each locule contains 1–2 mature, elongate seeds proximally and 5–9 aborted seeds of more irregular shape distally. Mature seeds are 1.5 mm long × 1.2 mm wide, elongate, and triangular transversely, with a slight flange. Seeds have a seed coat for which three zones can be well defined, a uniseriate outer palisade layer, a middle region of isodiametric cells comprising most of the integument, and a uniseriate inner layer of tangentially elongate cells lining the embryo cavity. Liquidambar changii is most similar to the eastern Asian L. acalycina H.‐T. Chang on features of infructescence, fruit, and seed morphology and quite unlike the North American L. styraciflua L. and other species. Such a close relationship between these two species supports a Beringian biogeographic track between eastern Asia and western North America during the Miocene. Previous phylogenetic and allozyme analysis of modern Liquidambar demonstrates a close relationship between North American‐western Asian taxa and suggests a North Atlantic biogeographic track in the middle Miocene. Together, these biogeographic tracks underscore the complexity of the biogeographic history of the Altingiaceae in the Northern Hemisphere throughout the Neogene.
Phylogenetic relationships and biogeography of Fuchsia (Onagraceae) based on noncoding nuclear and chloroplast DNA data
Authors: Berry Paul E. , Hahn William J. , Sytsma Kenneth J. , Hall Jocelyn C. , Mast Austin
Published: February 2008

To examine relationships and test previous sectional delimitations within Fuchsia, this study used parsimony and maximum likelihood analyses with nuclear ITS and chloroplast trnL‐F and rpl16 sequence data for 37 taxa representing all sections of Fuchsia and four outgroup taxa. Results support previous sectional delimitations, except for F. verrucosa, which is related to a Central American clade rather than to section Fuchsia and is described here as a new section Verrucosa. The basal relationships within Fuchsia are poorly resolved, suggesting an initial rapid diversification of the genus. Among the species sampled, there is strong support for a single South Pacific lineage, a southern South American/southern Brazilian lineage, a tropical Andean lineage, and one or two Central American and Mexican lineages. There is no clear support for an austral origin of the genus, as previously proposed, which is more consistent with Fuchsia's sister group relationship with the boreal Circaea. An ultrametric molecular clock analysis (all minimal dates) places the split between Fuchsia and Circaea at 41 million years ago (mya), with the diversification of the modern‐day lineages of Fuchsia beginning at 31 mya. The South Pacific Fuchsia lineage branches off around 30 mya, consistent with fossil records from Australia and New Zealand. The large Andean section Fuchsia began to diversify around 22 mya, preceded by the divergence of the Caribbean F. triphylla at 25 mya. The Brazilian members of section Quelusia separated from the southern Andean F. magellanica around 13 mya, and the ancestor of the Tahitian F. cyrtandroides split off from the New Zealand species of section Skinnera approximately 8 mya.
The potential for genetic assimilation of a native dandelion species,Taraxacum ceratophorum(Asteraceae), by the exotic congenerT. officinale
Authors: Brock Marcus T.
Published: February 2008

Exotic plant species can threaten closely related native congeners through asymmetric hybridization and subsequent backcrossing, the process known as genetic assimilation. I explore the initial stages of this process inTaraxacum ceratophorum(Asteraceae), the native alpine dandelion, and the invasive apomictT. officinale. In central Colorado, sevenT. ceratophorumpopulations all occur in sympatry withT. officinale. In one large population on Pennsylvania Mountain, surveys further revealed that flowering phenologies and visiting insect taxa overlap almost completely for bothTaraxacumspecies. Together these results indicated that heterospecific pollen transfer is likely. Crossing experiments showed thatT. ceratophorumis an obligate outcrosser, and interspecific hand pollinations resulted in 37.3% seed set. However, molecular analysis of the F1 offspring indicated that only 33.2% of germinating seeds were hybrids; the remainder were selfed offspring produced from a breakdown in self‐incompatibility (the mentor effect). Although the mentor effect helps reduce the production of hybrids, the asymmetrical direction of hybridization creates the potential for genetic assimilation ofT. ceratophorumbyT. officinale.
Reticulate evolution in kiwifruit (Actinidia, Actinidiaceae) identified by comparing their maternal and paternal phylogenies
Authors: Chat Joëlle , Jáuregui Blanca , Petit Rémy J. , Nadot Sophie
Published: February 2008

Evolutionary relationships within Actinidia, a genus known for the contrasting mode of inheritance of its plastids and mitochondria, were studied. The phylogenetic analysis is based on chloroplast (cp) and mitochondrial (mt) restriction site and sequence data (matK, psbC‐trnS, rbcL, and trnL‐trnF for cpDNA; nad1‐2/3 and nad4‐1/2 for mtDNA). The analysis of cp sequence data confirms the hypothesis that the four currently recognized sections are not monophyletic. The detection of incongruences among phylogenies (mtDNA vs. cpDNA tree) coupled with the detection of intraspecific polymorphisms confirms some of the reticulations previously emphasized, diagnoses new hybridization/introgression events, and provides evidence for multiple origin of at least two polyploid taxa. A number of hybridization/introgression events at the diploid, tetraploid, and possibly hexaploid levels are documented. The extensive reticulate evolution undergone by Actinidia could account for the lack of clear morphological discontinuities at the species level.
Phylogenetic inferences in the dung‐moss family Splachnaceae from analyses of cpDNA sequence data and implications for the evolution of entomophily
Authors: Goffinet Bernard , Shaw A. Jonathan , Cox Cymon J.
Published: February 2008

The moss family Splachnaceae is characterized by half of its members relying on insects for spore dispersal. These species grow on dung or other animal substrates. They produce small and aggregated spores, and their capsule is modified to attract coprophilous insects or carrion flies using olfactory and visual cues. Systematic concepts and implicit evolutionary inferences have relied much on variation in characters associated with the spore dispersal syndrome. Phylogenetic reconstructions based on sequence variation of two chloroplast loci (trnL‐trnF region and the rps4 gene) suggest that most supraspecific taxa are poly‐ or paraphyletic. Transformations in morphological characters associated to the syndrome thus offer little if any phylogenetically informative signal. Brachymitrion is resolved in a nested position within Tayloria. A new combination, Tayloria immersa (Goffinet) Goffinet, Shaw & Cox is proposed for B. immersum. Only one of the five subgenera of Tayloria (subg. Orthodon) is potentially monophyletic. Voitia shares a common ancestor with Tetraplodon and is thus nested within the Splachnoideae. The affinities of Aplodon remain ambiguous. Reconstruction of shifts between wind and insect spore dispersal syndromes suggests that entomophily arose more than once and may have been followed by a reversal to the generalist strategy in two lineages.
Suppression of branches in Eucalyptus trees
Authors: Senthalir P. , Sharanya S. , Paramathma M.
Published: February 2008

The effect of neem oil, which acts as a suckericide in tobacco, on branch suppression in Eucalyptus tereticornis was assessed to help maximize stem biomass. Lateral branches of selected trees were pruned, and neem oil solutions at concentrations of either 80%, 40%, 20%, 10%, or 0% (untreated control) were applied to leaf axils of the pruned branches. Regeneration of branches was suppressed, and the magnitude of suppression was proportional to the concentration of neem oil. Compared to the control, the percentage reduction in branching at 80% neem oil was 41.6%. When regenerated branches were repruned and neem oil applied at either 100%, 80%, or 0% (control), the regenerating ability of these branches was severely repressed by 78% at 100% neem oil relative to the control. Apical shoots were also topped and treated at either 100% or 0% (control) neem oil to identify the principal suppressive component in neem oil. The principal component azadirachtin was tested at 375, 750, 1500, 3125, 6250, 12 500, 25 000, 50 000, and 100 000 ppm and 0 ppm as the control. Reduction in the coppicing shoot was as high as 85%. Azadirachtin was responsible for the suppression. By pruning the lateral branches with neem oil, wasteful consumption of photosynthates can be precluded and the stem biomass maximized.
Mitosis in the yeast phase of the basidiomycetes Bensingtonia yuccicola and Stilbum vulgare and its phylogenetic implications
Authors: McLaughlin David J. , Hanson Ronald W. , Frieders Elizabeth M. , Swann Eric C. , Szabo Les J.
Published: February 2008

Phylogenetic studies of yeasts rely on an extensive molecular and biochemical data set, but structural characters are scarce. Details of mitosis in yeasts have been studied with transmission electron microscopy and immunofluorescence. Of these two methods immunofluorescence is faster and easier and yields sufficient detail for cytological comparisons. Only three basidiomycetous yeasts have been studied thus far with immunofluorescence. Mitosis in budding cells of ascomycetous yeasts occurs in the parent, while in basidiomycetous yeasts, except in Agaricostilbum pulcherrimum, it occurs in the bud. Mitosis in additional yeasts in the Agaricostilbomycetidae of the Urediniomycetes was observed using immunofluorescence localization of freeze‐substituted material. In Stilbum vulgare, mitosis occurred in the parent, but in Bensingtonia yuccicola it occurred in the bud as in most other basidiomycetous yeasts. Stilbum vulgare also had predominantly binucleate yeast cells. Nuclear small subunit rDNA sequence data showed that A. pulcherrimum and S. vulgare are more closely related to each other than to B. yuccicola within the Agaricostilbomycetidae. Based on the few taxa examined, mitotic and cytoskeletal characters provide phylogenetic information.
Life‐history variation and adaptation in the historically mobile plant Arabidopsis thaliana (Brassicaceae) in North America
Authors: Griffith Converse , Kim Eunsuk , Donohue Kathleen
Published: February 2008

We used field‐collected seeds of Arabidopsis thaliana (Brassicaceae) to simulate a colonization event of plants from diverse locations into a common environment to compare regionally “local” and “foreign” populations of this historically mobile species. Life history varied among regional groups, but most variation was found among populations within regions. While we found significant differences among populations and regional groups for important life‐history characters, we did not find significant differences in performance of plants from different populations or regional groups. Rather, we found evidence that differences in life history contributed to the ability of plants from foreign regions to perform comparably to local Kentucky plants. Had plants from different regions not differed in the timing and size of reproduction, we would have seen that Kentucky (local) plants had higher total fitness via greater reproductive success of individuals that survived to reproduce and that Michigan plants would have had the lowest fitness. The populations are comparably adapted to the environment in Kentucky but through different combinations of life‐history characters. Therefore, the life‐history variation in this mobile species appears to contribute not to fitness differences among populations but rather to success in colonizing new locations.
Revealing unknown or extinct lineages within Isoëtes (Isoëtaceae) using DNA sequencesfrom hybrids
Authors: Hoot Sara B. , Napier Nancy S. , Taylor W. Carl
Published: February 2008

Isoëtes, a heterosporous lycopod with a fossil record dating back to the Paleozoic, has numerous putative allopolyploids (resulting from hybridization events coupled with doubling of chromosome number). By using the highly variable nucleotide sequences from the second intron of a LFY homologue in Isoëtes, species could be delimited and hybrid origins determined. The data suggest that reticulate evolution is both common and complex within a more derived species complex of Isoëtes. Sequences of identifiable parentage and sequences that are unlike any diploid species known were recovered, leading to the conclusion that one or both of the putative parents have not yet been discovered or are extinct. A range of observations concerning allopolyploid speciation were categorized as follows: (1) verification of previous hypotheses regarding parentage (e.g., I. riparia, I. appalachiana), (2) determination that two morphologically distinct allotetraploid species can share the same parentage (I. azorica and I. acadiensis), (3) recognition of a cryptic allotetraploid species, indicated by the presence of different parental genomes (I. “appalachiana” from Florida), and (4) identification of allotetraploid species with one or two unknown parents (e.g., I. tuckermanii, I. acadiensis, I. azorica, and I. hyemalis). Some sequences from diploid species are remarkably uniform among populations (e.g., I. echinospora from various locations in North America, Iceland, and Wales), while others are variable at the subspecies level (e.g., northern and southern populations within I. engelmannii).
Phylogenetic position and biogeography of Hillebrandia sandwicensis (Begoniaceae): a rare Hawaiian relict
Authors: Clement Wendy L. , Tebbitt Mark C. , Forrest Laura L. , Blair Jaime E. , Brouillet Luc , Eriksson Torsten , Swensen Susan M.
Published: February 2008

The Begoniaceae consist of two genera, Begonia, with approximately 1400 species that are widely distributed in the tropics, and Hillebrandia, with one species that is endemic to the Hawaiian Islands and the only member of the family native to those islands. To help explain the history of Hillebrandia on the Hawaiian Archipelago, phylogenetic relationships of the Begoniaceae and the Cucurbitales were inferred using sequence data from 18S, rbcL, and ITS, and the minimal age of both Begonia and the Begoniaceae were indirectly estimated. The analyses strongly support the placement of Hillebrandia as the sister group to the rest of the Begoniaceae and indicate that the Hillebrandia lineage is at least 51–65 million years old, an age that predates the current Hawaiian Islands by about 20 million years. Evidence that Hillebrandia sandwicensis has survived on the Hawaiian Archipelago by island hopping from older, now denuded islands to younger, more mountainous islands is presented. Various scenarios for the origin of ancestor to Hillebrandia are considered. The geographic origin of source populations unfortunately remains obscure; however, we suggest a boreotropic or a Malesian–Pacific origin is most likely. Hillebrandia represents the first example in the well‐studied Hawaiian flora of a relict genus.
Buzz‐pollinated Dodecatheon originated from within the heterostylous Primula subgenus Auriculastrum (Primulaceae): a seven‐region cpDNA phylogeny and its implications for floral evolution
Authors: Mast Austin R. , Feller Danielle M. S. , Kelso Sylvia , Conti Elena
Published: February 2008

We sequenced seven cpDNA regions from 70 spp. in Dodecatheon, Primula subgenus Auriculastrum, and outgroups, reconstructed their cpDNA phylogeny with maximum parsimony, and determined branch support with bootstrap frequencies and Bayesian posterior probabilities. Strongly supported conclusions include the (1) paraphyly of Primula subgenus Auriculastrum with respect to a monophyletic Dodecatheon, (2) sister relationship between the North American Dodecatheon and the Californian P. suffrutescens, (3) novel basal split in Dodecatheon to produce one clade with rugose and one clade with smooth anther connectives, (4) monophyly of all sections of Primula subgenus Auriculastrum, and (5) exclusion of the enigmatic Primula section Amethystina from the similar Primula subgenus Auriculastrum. These results support the origin of the monomorphic, buzz‐pollinated flower of Dodecatheon from the heterostylous flower of Primula. We marshal evidence to support the novel hypothesis that the solanoid flower of Dodecatheon represents the fixation of recessive alleles at the heterostyly linkage group (pin phenotype). Of the remaining traits associated with their solanoid flowers, we recognize at least six likely to have arisen with the origin of Dodecatheon, one that preceded it (flower coloration, a transfer exaptation in Dodecatheon), and one that followed it (rugose anther connectives, an adaptation to buzz pollination).
Northern hemisphere biogeography of Cerastium (Caryophyllaceae): insights from phylogenetic analysis of noncoding plastidnucleotide sequences
Authors: Scheen Anne‐Cathrine , Brochmann Christian , Brysting Anne K. , Elven Reidar , Morris Ashley , Soltis Douglas E. , Soltis Pamela S. , Albert Victor A.
Published: February 2008

Phylogenetic relationships and biogeography of the genus Cerastium were studied using sequences of three noncoding plastid DNA regions (trnL intron, trnL‐trnF spacer, and psbA‐trnH spacer). A total of 57 Cerastium taxa was analyzed using two species of the putative sister genus Stellaria as outgroups. Maximum parsimony analyses identified four clades that largely corresponded to previously recognized infrageneric groups. The results suggest an Old World origin and at least two migration events into North America from the Old World. The first event possibly took place across the Bering land bridge during the Miocene. Subsequent colonization of South America occurred after the North and South American continents joined during the Pliocene. A more recent migration event into North America probably across the northern Atlantic took place during the Quaternary, resulting in the current circumpolar distribution of the Arctic species. Molecular clock dating of major biogeographic events was internally consistent on the phylogenetic trees. The arctic high‐polyploid species form a polytomy together with some boreal and temperate species of the C. tomentosum group and the C. arvense group. Lack of genetic variation among the arctic species probably indicates a recent origin. The annual life form is shown to be of polyphyletic origin.
A chemotaxonomic analysis of cannabinoid variation in Cannabis (Cannabaceae)
Authors: Hillig Karl W. , Mahlberg Paul G.
Published: February 2008

Cannabinoids are important chemotaxonomic markers unique to Cannabis. Previous studies show that a plant's dry‐weight ratio of Δ9‐tetrahydrocannabinol (THC) to cannabidiol (CBD) can be assigned to one of three chemotypes and that alleles BD and BT encode alloenzymes that catalyze the conversion of cannabigerol to CBD and THC, respectively. In the present study, the frequencies of BD and BT in sample populations of 157 Cannabis accessions were determined from CBD and THC banding patterns, visualized by starch gel electrophoresis. Gas chromatography was used to quantify cannabinoid levels in 96 of the same accessions. The data were interpreted with respect to previous analyses of genetic and morphological variation in the same germplasm collection. Two biotypes (infraspecific taxa of unassigned rank) of C. sativa and four biotypes of C. indica were recognized. Mean THC levels and the frequency of BT were significantly higher in C. indica than C. sativa. The proportion of high THC/CBD chemotype plants in most accessions assigned to C. sativa was <25% and in most accessions assigned to C. indica was >25%. Plants with relatively high levels of tetrahydrocannabivarin (THCV) and/or cannabidivarin (CBDV) were common only in C. indica. This study supports a two‐species concept of Cannabis.
Amborella not a “basal angiosperm”? Not so fast
Authors: Soltis Douglas E. , Soltis Pamela S.
Published: February 2008

The sequence of the plastid genome of Amborella trichopoda, the putative sister to all other extant angiosperms, was recently reported (Molecular Biology and Evolution 20: 1499–1505). Goremykin et al. used sequence data for 61 plastid genes from Amborella and 12 other embryophytes in phylogenetic analyses and concluded that Amborella is not the sister to the remaining flowering plants; the monocots instead occupy this position. The authors attributed their results, which differ substantially from all recent phylogenetic analyses of angiosperms, to the increased character sampling (30 017 nucleotides in their aligned matrix) in their analysis relative to published studies that included fewer genes but more taxa. We hypothesized that the difference in topology is not due to limited character sampling in previous studies but to limited taxon sampling in the analysis by Goremykin et al. To test this, we conducted a series of phylogenetic analyses using a three‐gene, 12 (or more)‐taxon data set to evaluate the topological effects of (i) including three vs. 61 genes for (nearly) the same set of taxa, (ii) analyzing different codon positions, (iii) substituting representatives of other basal lineages for Amborella, (iv) replacing the grasses used to represent the monocots with other monocots, selected either for their phylogenetic position or randomly, and (v) adding other basal taxa—Nymphaea, Austrobaileya, magnoliids, and monocots—to the 12‐taxon data set. Our results demonstrate that the “monocots basal” topology obtained by Goremykin et al. is not due to increased character sampling of the plastid genome; their topology was obtained using only two plastid genes or two plastid genes and one nuclear gene. This topology was also retained when either Nymphaea or Austrobaileya was substituted for Amborella, demonstrating that any of the three basal lineages will attach to Calycanthus for lack of any other close branch. Furthermore, the “monocots basal” topology is not robust to changes in sampling of monocots. Simply adding Oncidium, for example, places Amborella sister to the other angiosperms. Thus, limited taxon sampling, focusing on organisms with complete genome sequences, can lead to artifactual results.
Reproductive ecology of distylous Palicourea padifolia (Rubiaceae) in a tropical montane cloud forest. II. Attracting and rewarding mutualistic and antagonistic visitors
Authors: Ornelas Juan Francisco , González Clementina , Jiménez Leonor , Lara Carlos , Martínez Armando J.
Published: February 2008

By definition, the floral morphs of distylous plants differ in floral architecture. Yet, because cross‐pollination is necessary for reproductive success in both morphs, they should not differ in attributes that contribute to attracting and rewarding floral visitors. Floral and vegetative attributes that function in distylous polymorphism in hummingbird‐pollinated Palicourea padifolia (Rubiaceae) and the responses of pollinators and insect herbivores to the resources offered by both morphs were investigated. The performance of each morph along multiple stages of the reproductive cycle, from inflorescence and nectar production to fruit production, was surveyed, and pollinator behavior and nectar standing crops were then observed. Costs associated with such attractiveness were also evaluated in terms of herbivore attack and of plant reproductive fitness (female function) as a function of leaf herbivory. The number of inflorescences, floral buds, open flowers, and ripe fruits offered by either floral morph were similar, but short‐styled plants almost doubled the number of developing fruits of long‐styled plants. Long‐styled flowers produced higher nectar volumes and accumulated more nectar over time than short‐styled flowers. Measures of nectar standing crop and data on pollinator behavior suggest that hummingbirds respond to this morph‐specific scheduling of nectar production. Lastly, long‐styled plants suffered a higher herbivore attack and lost more leaf area over time than those with short‐styled flowers. Herbivory was negatively correlated with fruit number and fruit mass, and long‐styled plants set significantly less fruit mass than short‐styled plants. The results suggest that pollinators and herbivores may exert selective pressures on floral and vegetative traits that could also influence gender function.
Relationships of the Macaronesian and Mediterranean floras: molecular evidence for multiple colonizations into Macaronesia and back‐colonization of the continent in Convolvulus (Convolvulaceae)
Authors: Carine Mark A. , Russell Stephen J. , Santos‐Guerra Arnoldo , Francisco‐Ortega Javier
Published: February 2008

A molecular phylogenetic analysis of the Macaronesian endemic species of Convolvulus was undertaken using data from the nuclear ribosomal internal transcribed spacer (ITS) regions. The results of the analysis support two introductions into Macaronesia from distantly related clades within Convolvulus and a subsequent back‐colonization to the continent from within one of the clades. Hypothesized relationships between Macaronesian species and New World taxa and between the Canarian endemic C. caput‐medusae and the Moroccan C. trabutianus are refuted. Both Macaronesian clades are shown to have Mediterranean sister groups although one is predominantly western Mediterranean and the other predominantly eastern Mediterranean in distribution. The patterns of colonization into Macaronesia demonstrated by Convolvulus and also by other multiple colonizing genera conform to either a pattern of phylogenetic distinctiveness or a checkerboard distribution of island lineages. Both are consistent with the hypothesis that niche preemption is responsible for the limited number of colonizations into the region. A review of sister group relationships demonstrates that, in common with Convolvulus, most Macaronesian groups have sister groups distributed in the near‐continent (i.e., western Mediterranean). Disjunct sister group relationships (including Eastern Mediterranean disjunctions) occur in only 18% of groups.
Bryophyte dispersal inferred from colonization of an introduced substratum on Whiteface Mountain, New York
Authors: Miller Norton G. , McDaniel Stuart F.
Published: February 2008

A long‐standing debate in bryophyte biogeography concerns the frequency of long‐distance spore dispersal. The diversity of bryophytes on mortared rock walls along the Veterans Memorial Highway on Whiteface Mountain, New York, USA, was studied to document the recruitment of species over the 65 years since the highway was constructed. The highway is situated in the Adirondack Mountains, a relatively unpopulated region with a largely acidic flora. The introduction of mortar has increased the bryophyte diversity by 50% above that of native lithic substrata on the mountain. The composition of the native and mortar floras differed greatly, suggesting that the walls were not colonized by locally abundant ruderal species. Many of the species sampled on the walls are typically found only in lower elevation forested sites, distant (∼5 km or more) from the highway, and not on anthropogenic calcium carbonate. These results suggest that a bryophyte community consisting of common and uncommon species assembled from distant sites at the rate of at least one species per year in the last 65 years. These data provide the ecological context for experimental and phylogeographic studies and suggest that some bryophytes may be capable of routine dispersal over distances of at least 5 km.
Variation in sex allocation and male–female trade‐offs in six populations of Collinsia parviflora (Scrophulariaceae s.l.)
Authors: Parachnowitsch Amy L. , Elle Elizabeth
Published: February 2008

Assumed trade‐offs between male and female functions in hermaphroditic flowers have been difficult to demonstrate. Collinsia parviflora (Scrophulariaceae) is a winter annual that exhibits significant among‐population variation in corolla size in British Columbia, Canada. We asked whether reduction in secondary male allocation (i.e., the attractive corolla), a preliminary indicator of mating system, was matched by a reduction in primary male allocation (i.e., pollen production), and whether there were allocation trade‐offs between male and female function both within and among six study populations. Larger‐flowered populations allocated more to male function (androecium and corolla biomass), and because populations did not vary in female biomass allocation (gynoecium and calyx), population differences were not due to simple allometric scaling. Populations also differed in per‐flower gamete production (pollen and ovules). We found male–female trade‐offs within populations between androecium and gynoecium mass and between corolla and calyx mass. Among populations, there was a marginal trade‐off between pollen and ovule production and a significant within‐male trade‐off between pollen grain size and number. Trade‐offs between the sexes were primarily apparent when we controlled for flower size in the analysis. Variation among populations in sex allocation may reflect different optima related to the mating system.
Origin of the disjunct tetraploid Cardamine amporitana (Brassicaceae) assessed with nuclear and chloroplast DNA sequence data
Authors: Lihová Judita , Fuertes Aguilar Javier , Marhold Karol , Nieto Feliner Gonzalo
Published: February 2008

Seventy‐four nucleotide sequences from the ITS regions of nuclear ribosomal DNA and 76 from the trnL‐trnF spacer of chloroplast DNA were used to address the origin of tetraploid Cardamine amporitana, the conspecifity of central Italian and northeastern Spanish populations, and the possible cause for such geographic disjunction. Because of the complex lineage relationships in Cardamine, the sampling included 22 taxa. In the results, both data sets are highly congruent in supporting a close relationship of C. amporitana to the widespread Eurasian C. amara. Low genetic variability in northeastern Spanish populations of C. amporitana suggests long‐distance dispersal from central Italy. The interior position of the single northeastern Spanish haplotype in a statistical parsimony network of trnL‐trnF haplotypes however does not support this scenario and invokes other plausible phylogeographic explanations. The disappearance of geographically intermediate populations and genetic impoverishment by migration and isolation, both probably associated with Quaternary climatic oscillations, appears as an alternative hypothesis to explain the phylogeographic pattern. A recent hybridization event is reported between C. amporitana and a diploid from the C. pratensis group in central Italy on the basis of additive polymorphisms in ITS for all the 22 distinguishing nucleotides.
Anatomically preserved seeds of Nuphar (Nymphaeaceae) from the Early Eocene of Wutu, Shandong Province, China
Authors: Chen Iju , Manchester Steven R. , Chen Zhiduan
Published: February 2008

Well‐preserved seeds from the early Eocene of Wutu, Shandong, China are assigned to the genus Nuphar (Nymphaeaceae) based on morphology and anatomy. The seeds of Nuphar wutuensis sp. nov. are ellipsoidal to ovoid, 4–5 mm long with a clearly visible raphe ridge, and a truncate apex capped by a circular operculum ca. 1 mm in diameter bearing a central micropylar protrusion. These features, along with the testa composed of a uniseriate outer layer of equiaxial pentagonal to hexagonal surface cells and a middle layer 4–6 cells thick composed of thick‐walled, periclinally elongate sclereids, correspond to the morphology and anatomy of extant Nuphar and distinguish this fossil species from all other extant and extinct genera of Nymphaeales. These seeds provide the oldest record for the genus in Asia and are supplemented by a similar well‐preserved specimen from the Paleocene of North Dakota, USA. These data, together with the prior recognition of Brasenia (Cabombaceae) in the middle Eocene, indicate that the families Nymphaeaceae and Cabombaceae had differentiated by the early Tertiary.
Chloroplast small heat‐shock proteins protect photosynthesis during heavy metal stress
Authors: Heckathorn Scott A. , Mueller J. Kathleen , LaGuidice Stephanie , Zhu Bin , Barrett Tara , Blair Brian , Dong Yan
Published: February 2008

Plants can accumulate heavy metals when exposed to them at high levels. These metals can interfere with photosynthesis. Limited evidence suggests that increased synthesis of some heat‐shock proteins (Hsps) may be a general plant response to metal stress, but the specific functions or structures protected by Hsps remain unidentified. Chloroplast small Hsps (smHsps) protect photosynthetic electron transport (Phet) during heat, oxidative, and photoinhibitory stress, but it is not known if chloroplast smHsps are synthesized during metal stress and protect photosynthesis. Zea mays (corn) plants were exposed to varying soil concentrations of Cu, Ni, Pb, and Zn to determine if chloroplast smHsps are induced by heavy metals, if smHsps protect Phet, and any effects on chloroplast smHsp and photosynthesis. Net photosynthesis (Phn) decreased with all metals—more so at higher levels and with longer exposures. Decreases in Phn resulted from damage to photosynthetic metabolism, including Phet. All metals increased chloroplast smHsp content, which increased with time of exposure. In vitro, Phet was protected from Pb (but not Ni) by purified chloroplast smHsp added to thylakoids. In vivo, Phn was protected from Ni and Pb by increases in smHsp in a heat‐tolerant Agrostis stolonifera selection genotype expressing additional chloroplast smHsps compared to a near‐isogenic heat‐sensitive genotype. These results are evidence that Hsps protect photosynthesis from heavy metals and are among the first to demonstrate specific functions protected by Hsps during metal stress.
Multi‐scale genetic analysis of Uniola paniculata (Poaceae): a coastal species with a linear, fragmented distribution
Authors: Franks Steven J. , Richards C. L. , Gonzales E. , Cousins J. E. , Hamrick J. L.
Published: February 2008

Geographic and fine‐scale population genetic structures of Uniola paniculata, the dominant coastal dune grass in the southeastern USA, were examined. The linear, naturally fragmented distribution of this native perennial was hypothesized to lead to high genetic structure and lower genetic diversity at the margin of the species range. The extensive ramet production and low seed germination of this species were also expected to cause populations to be dominated by a few large clones. At 20 sites throughout the range of the species, leaf tissue was collected from 48 individuals. Clonal structure was examined using leaf tissue collected from an additional 60 individuals, each in four patches at two sites. Starch gel electrophoresis was used to resolve 27 allozyme loci. The results indicated that Uniola had greater genetic structure (GST = 0.304) than most other outcrossing species, indicating moderate barriers to gene flow. There was a weak but significant positive relationship between genetic distance and geographic distance, supporting an isolation‐by‐distance model of gene flow. There were no obvious disjunctions between regions. Genetic diversity (He) was relatively uniform throughout most of the range of the species but was lower in all western Gulf of Mexico populations. Clonal diversity varied both within and among sites, but clones were often small, suggesting that sexual reproduction and recruitment from seeds are important factors maintaining genetic diversity.
Radiation of the Australian Salicornioideae (Chenopodiaceae)—based on evidence from nuclear and chloroplast DNA sequences
Authors: Shepherd K. A. , Waycott M. , Calladine A.
Published: February 2008

In phylogenetic analyses of nuclear ITS and chloroplasttrnLDNA sequences, the mostly endemic Australian genera;Halosarcia,Pachycornia,Sclerostegia,Tecticornia, andTegicorniaof the subfamily Salicornioideae (Chenopodiaceae) together form a monophyletic group, congruent with the hypothesis that they evolved from a common ancestor. However, limited genetic differentiation evident in both nrDNA and cpDNA sequences among these taxa suggests a possible rapid radiation. Based on fossil pollen records and climatic models of other authors, it is hypothesized that the expansion of the Australian endemic Salicornioideae most likely occurred during the Late Miocene to Pliocene, when increasing aridity caused the formation of extensive salt lakes along endorheic paleodrainage channels. Moreover, AustralianSarcocorniarepresentatives were supported as monophyletic, nested within a paraphyleticSarcocorniaclade that also comprised EuropeanSalicorniain the ITS analysis. This suggests thatSarcocorniaarrived in Australia subsequent to the ancestor of the Australian endemic genera most likely via long‐distance dispersal.