bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of the extent of among‐family variation in inbreeding depression in the perennial herb Scabiosa columbaria (Dipsacaceae)
Authors: Picó F. Xavier , Ouborg N. Joop , Van Groenendael Jan M.
Published: February 2008

Significantly different maternal line responses to inbreeding provide a mechanism for the invasion of a selfing variant into a population. The goal of this study was to examine the extent of family‐level variation in inbreeding depression in the mixed‐mating, perennial herb Scabiosa columbaria. Plants from one population were raised, and hand‐pollinated to produce selfed and outcrossed progeny, and the effects of inbreeding depression on life‐cycle traits were analyzed. Inbreeding depression significantly affected early life cycle traits. The pollination treatment by family interaction was significant for almost all traits, indicating a high family‐level variation in inbreeding depression. The correlations between inbreeding depression values (e.g., percentage germination and flowering date, and flowering date and aboveground biomass) exhibited alternate signs, illustrating the type of association between inbreeding depression loci for different traits across the life cycle. Overall, it is concluded that the extent of among‐family variation in inbreeding depression might allow a selfing variant of S. columbaria to invade an outcrossing population, though the pattern of correlations between inbreeding depression values might prevent effective purging of the deleterious genetic load.
Atmospheric invasion of non‐native pollen in the Mediterranean region
Authors: Belmonte Jordina , Vilà Montserrat
Published: February 2008

Most research on the impacts of plant invasion focuses on native plant performance, community structure, and ecosystem functioning. Some non‐native species can also pose a risk to human health. One such risk is the allergenic nature of the pollen of some introduced plants. We examined whether patterns of airborne pollen differed between non‐native and native taxa by summarizing data from seven Spanish Mediterranean localities monitored over 13 yr. The pollen spectra contained 27 native pollen taxa and 18 non‐native taxa. Even though pollen from native taxa were more diverse and were present longer in the atmosphere than the non‐native, in some years neither the prevalence of the two nor their weekly maximum pollen values differed significantly. However, maximum values for non‐native taxa were found earlier in the season than for native pollen. A small percentage of non‐native pollen includes pollen from introduced taxa that have not invaded natural habitats (e.g., ornamental plants). Non‐native pollen has a larger proportion of allergenic pollen than native pollen. Therefore, the results reveal that the presence of non‐native airborne pollen from naturalized and non‐naturalized plant species increases the total amount of airborne allergenic pollen grains and the period of allergenic susceptibility.
Inhibition of peptide deformylase in Nicotiana tabacum leads to decreased D1 protein accumulation, ultimately resulting in a reduction of photosystem II complexes
Authors: Hou Cai‐Xia , Dirk Lynnette M. A. , Williams Mark A.
Published: February 2008

Eukaryotic homologs of bacterial peptide deformylases were recently found in several vascular plants and may be essential in chloroplast protein processing. Treating tobacco seedlings with the peptide deformylase inhibitor actinonin resulted in leaf chlorosis and reduced growth and development, indicative of a systemic movement of the inhibitor. Photosystem II (PSII) activity was reduced, manifested as a significant decrease in the maximum quantum efficiency of photosystem II. Accumulation and assembly of nascent D1 protein into PSII monomers was also reduced, eventually leading to PSII disassembly and leaf necrosis. Processing and assembly of D1 protein in tobacco was a major and potentially critical target of peptide deformylase inhibition. These results confirm that N‐terminal deformylation is an essential step in the accumulation and assembly of PSII subunit polypeptides in the chloroplasts of vascular plants.
Obligate pollination mutualism in Breynia (Phyllanthaceae): further documentation of pollination mutualism involving Epicephala moths (Gracillariidae)
Authors: Kawakita Atsushi , Kato Makoto
Published: February 2008

This paper reports obligate seed‐parasitic pollination mutualisms in Breynia vitis‐idea and B. fruticosa (Phyllanthaceae). The genus Breynia is closely related to Glochidion and Gomphidium (a subgenus of Phyllanthus), in which pollination by species‐specific, seed‐parasitic Epicephala moths (Gracillariidae) have been previously reported. At night, female Epicephala moths carrying numerous pollen grains on their proboscises visited female flowers of B. vitis‐idea, actively pollinated flowers, and each subsequently laid an egg. Examination of field‐collected flowers indicated that pollinated flowers of B. vitis‐idea and B. fruticosa almost invariably had Epicephala eggs, suggesting that these moths are the primary pollinators of the two species. Single Epicephala larvae consumed a fraction of seeds within developing fruit in B. vitis‐idea and all seeds in B. fruticosa. However, some of the fruits were left untouched, and many of these had indication of moth oviposition, suggesting that egg/larval mortality of Epicephala moths is an important factor assuring seed set in these plants. The overall similarity of the specialized floral structure among Breynia species may indicate that this pollination system is fairly widespread within the genus.
Environmentally induced variation in fecundity compensation in the morph‐biased male‐sterile distylous shrub Erythroxylum havanense (Erythroxylaceae)
Authors: Rosas Luis F. , Pérez‐Alquicira Jessica , Domínguez César A.
Published: February 2008

The evolution of male‐sterile individuals in hermaphroditic species represents the first step in the evolution of sex specialization. For male‐sterile individuals to persist they must have some fitness advantage that compensates for their loss of the male function. Female fecundity also depends on environmental factors as those determining the likelihood of pollination and fertilization. Here we assessed the effects of both male sterility and reproductive synchrony (an environmentally affected trait) on the magnitude of female compensation of Erythroxylum havanense, a distylous shrub with morph‐biased male sterility. In vitro measurements of pollen germination showed that thrums were more male sterile than pins. The compensatory advantage of thrums changed by a factor of five depending on flowering synchrony. Flowering in synchrony with the population increased fruit production in both morphs. However, because pins that flowered out of synchrony produced almost no fruits, the reproductive compensation of thrums was higher in these circumstances. Because the magnitude of compensation is frequently considered as a key factor in the evolution of sex specialization, the environmentally induced variation in the magnitude of the reproductive compensation of thrum plants may have profound effects on the evolutionary dynamics of the reproductive system of E. havanense.
Plant generalization on pollinators: species property or local phenomenon?
Authors: Herrera Carlos M.
Published: February 2008

Despite recent increased interest in the frequency and evolutionary consequences of generalization in plant–pollinator systems, little is known on whether plant generalization on pollinators actually is a species‐level trait. This paper addresses the following questions for the insect‐pollinated shrub Lavandula latifolia: (1) Are different populations of this pollinator‐generalist plant similarly generalized? (2) Within a highly generalized population, are all plants similarly pollinator‐generalists? Comparable values for richness in pollinator species were obtained from individual‐ or population‐specific rarefaction curves as the projected number of distinct pollinator species implicated in 100 flower visits (SRAR100). Simple counts of pollinator species recorded per individual or population (SOBS) were weakly or nonsignificantly correlated with corresponding SRAR100 figures and closely correlated with flower visitation frequency. The pollination system of L. latifolia was highly generalized at the regional level, but populations differed greatly in pollinator species richness (SRAR100). Within the population intensively studied, individual plants had quite variable degrees of generalization, comparable in magnitude to variation among populations. It is concluded that generalization was not an invariant, species‐level property in L. latifolia. Furthermore, pollinator diversity estimates based on SOBS data may be heavily contingent on aspects related to both research design (sampling effort) and biological phenomena (variation in pollinator abundance or visitation rates), which may either mask or distort underlying ecological patterns of interest.
The molecular phylogeny of Alpinia (Zingiberaceae): a complex and polyphyletic genus of gingers
Authors: Kress W. John , Liu Ai‐Zhong , Newman Mark , Li Qing‐Jun
Published: February 2008

Alpinia is the largest, most widespread, and most taxonomically complex genus in the Zingiberaceae with 230 species occurring throughout tropical and subtropical Asia. Species of Alpinia often predominate in the understory of forests, while others are important ornamentals and medicinals. Investigations of the evolutionary relationships of a subset of species of Alpinia using DNA sequence‐based methods specifically test the monophyly of the genus and the validity of the previous classifications. Seventy‐two species of Alpinia, 27 non‐Alpinia species in the subfamily Alpinioideae, eight species in the subfamily Zingiberoideae, one species in the subfamily Tamijioideae, and three species in the outgroup genus Siphonochilus (Siphonochiloideae) were sequenced for the plastid matK region and the nuclear internal transcribed spacer (ITS) loci. Parsimony analyses of both individual and combined data sets identified six polyphyletic clades containing species of Alpinia distributed across the tribe Alpinieae. These results were supported by a Bayesian analysis of the combined data set. Except in a few specific cases, these monophyletic groupings of species do not correspond with either Schumann's (1904) or Smith's (1990) classification of the genus. Here we build on previous molecular analyses of the Alpinioideae and propose the next steps necessary to recognize new generic boundaries in the Alpinieae.
Differences in growth trajectory and strategy of two sympatric congeneric species in an Indonesian floodplain forest
Authors: Yamada Toshihiro , Ngakan Oka Putu , Suzuki Eizi
Published: February 2008

Whole‐plant development trajectories and sapling leaf displays were compared for two sympatric congeneric species, Pterospermum diversifolium and P. javanicum, in a tropical floodplain forest in East Kalimantan, Indonesia. We assessed their growth strategies and developed hypotheses for their coexistence within the community. Pterospermum diversifolium retains a monoaxial growth habit that promotes quick stem elongation; thus, it is taller when branches are initiated than is P. javanicum. The species differed significantly in height growth and total crown expansion per unit increment of biomass: monoaxial P. diversifolium saplings devote more effort to stem elongation, whereas branched P. javanicum saplings devote more effort to branch expansion. Monoaxial P. diversifolium sustained more severe self‐shading than P. javanicum. The sapling growth strategy of P. diversifolium appears to be dynamic, emphasizing the opportunistic use of light following a disturbance, whereas that of P. javanicum appears to be static, optimizing leaf display for current light conditions. The advantages of these strategies depend on context, and the two species may coexist within a community by adopting different regeneration niches based on differing understory light conditions: P. diversifolium is favored over P. javanicum at high light levels, but the opposite is true at low light levels.
Geographic pattern of genetic diversity inPinus resinosa: contact zone between descendants of glacial refugia
Authors: Walter Rosemarie , Epperson Bryan K.
Published: February 2008

Although red pine (Pinus resinosa) generally has low or completely lacks variation for molecular markers, some variation is observed for chloroplast microsatellites (cpSSRs). We sampled and examined 10 cpSSRs for 19 populations. Analysis of these populations plus 10 previously studied populations shows that the geographic distribution of genetic diversity over the range ofP. resinosais markedly nonuniform. Although the pattern exhibits little isolation by distance, there is a region centered in northeastern New England where populations contain much greater chloroplast haplotype diversity than elsewhere. This area is band‐shaped, with the longer axis nearly parallel with latitude, and very sharply delineated. The area of high diversity was buried by the Laurentide ice sheet. The geographic pattern indicates thatP. resinosais not at equilibrium, and the species has had a more complex postglacial history than typically purported for forest trees in eastern North America. The results suggest that the area of high diversity is a stable transition zone between descendants of two distinct refugia, one in the southern Appalachians and another near the North Atlantic coastline of the Wisconsinian glacial period. Plausible explanations are given that selection between two lineages, along latitudinal zones, may have maintained the transition zone.
Influence of plant ontogeny on compensation to leaf damage
Authors: Boege Karina
Published: February 2008

Ontogenetic changes in architecture, carbohydrate reserves, and resource allocation can constrain the ability of plants to compensate for herbivore damage. To evaluate ontogenetic changes in compensation, saplings and reproductive individuals of the tropical tree Casearia nitida were subjected to three levels of defoliation (0, 25, and 75% leaf area removed) and regrowth was quantified. The impact of defoliation on fruit production was evaluated in reproductive trees. In addition, the influence of defoliation on carbohydrate reserves and on the production of phenolic compounds was assessed. Plants at both stages were able to compensate for 25% leaf area loss, but only saplings were able to compensate at the 75% defoliation level. Negative impacts of defoliation on reproductive trees were also suggested by their tendency to produce fewer fruits when defoliated. The concentration of nonstructural carbohydrates decreased with damage in saplings but not in reproductive trees, suggesting an ontogenetic stage‐dependent impact of defoliation on carbohydrate reserves. The concentration of phenolic compounds in leaves decreased with increasing leaf damage in both ontogenetic stages. This suggests a resource based trade‐off between defense and compensation. The results from this study suggest that ontogeny needs to be considered when assessing plant responses to herbivore damage.
Variation in floral longevity between populations of Campanula rotundifolia (Campanulaceae) in response to fitness accrual rate manipulation
Authors: Giblin David E.
Published: February 2008

Floral longevity, the time between corolla expansion and senescence, contributes directly and indirectly to a plant's overall fitness. Though mating opportunities for insect‐pollinated species often differ among populations, few empirical studies have addressed whether floral longevity varies in a manner consistent with these differences. I conducted experiments at thermally distinct sites to examine whether the prevailing floral longevity model predicted such variation between a montane and an alpine population of Campanula rotundifolia. Staminate phase duration was significantly shorter for montane vs. alpine C. rotundifolia flowers in the presence of pollinators, but significantly longer when pollinators were excluded. Montane flowers had a significantly higher female fitness accrual rate, significantly shorter total longevities, and, unlike alpine flowers, were not pollen‐limited. Delaying pollinator access to pistillate phase flowers significantly increased total longevity in alpine flowers only. Significant differences in total longevity between populations resulted from an extended pistillate phase in alpine flowers. Overall, the prevailing model accurately predicted the total floral longevity trends found here. However, I provide novel evidence for geographic and gender‐specific plasticity in the floral longevity response to fitness accrual rate variation, suggesting C. rotundifolia populations in this study may be attuned to local schedules of pollinator activity.
Sexual reproduction, hybridization, apomixis, and polyploidization in the genus Boechera (Brassicaceae)
Authors: Schranz M. Eric , Dobeš Christoph , Koch Marcus A. , Mitchell‐Olds Thomas
Published: February 2008

Of the 340 genera in the Brassicaceae, apomictic reproduction is found only in the North American genus Boechera. We investigated phylogenetic relationships, ability to hybridize, mating system, and ploidy levels of 92 lines sampled from 85 populations and representing 19 Boechera species. Phylogenetic analyses based on chloroplast DNA sequences identified three lineages in the genus. Reciprocal crosses of each line were made to a common sexual diploid B. stricta tester. The resulting F1 progeny were analyzed for the inheritance of polymorphic microsatellite loci, genome size, and seed production. Intraspecific B. stricta crosses confirmed that this species is mostly diploid and sexual. Interspecific crosses revealed many other species were diploid and sexual and could be successfully hybridized with the tester. We also found obligate and facultative apomictic diploid and triploid lines. De novo F1 polyploids (either triploids or tetraploids) were derived from the union of nonreduced (from an apomictic parent) and reduced (from the tester) gametes. However, seed production of these F1 plants was generally low, suggesting a failure in the transmission of apomixis. The creation of a wide array of segregating genetic populations will facilitate future research on the evolution and inheritance of quantitative variation in Boechera.
Ecological factors influencing tetraploid establishment in snow buttercups (Ranunculus adoneus , Ranunculaceae): minority cytotype exclusion and barriers to triploid formation
Authors: Baack Eric J.
Published: February 2008

Polyploid speciation is an ongoing, important source of angiosperm diversity. However, the barriers to polyploid speciation and mechanisms of establishment remain poorly understood for all but a few species. Several factors likely to have influenced tetraploid establishment, including barriers to triploid formation, consequences of mixed‐ploidy pollen loads, and the reproductive success of the minority cytotype, were examined in snow buttercups (Ranunculus adoneus) through a series of pollination and transplant experiments. Tetraploid snow buttercups do not have stigmatic barriers to pollen from diploid plants, nor does pollen from tetraploid plants have an advantage over pollen from diploids when on tetraploid stigmas. Tetraploid plants transplanted into a diploid population produced 50% fewer seeds than tetraploid plants in a tetraploid population. Intrinsic barriers to triploid formation were relatively weak, but few triploid seeds formed when mixed‐ploidy pollen was present. Fecundity of triploid plants was very low, and no tetraploid offspring resulted. These results indicate that in snow buttercups, a triploid plant will contribute 0.8% of the tetraploid seeds of a minority tetraploid plant making it a minor contributor to the demographics of tetraploid establishment. The reproductive costs facing minority cytotype plants may explain the previously observed spatial segregation in snow buttercups.
Inbreeding depression in perennial Lychnis viscaria (Caryophyllaceae): effects of population mating history and nutrient availability
Authors: Mustajärvi Kaisa , Siikamäki Pirkko , Åkerberg Anne
Published: February 2008

We studied inbreeding depression in a perennial plant, Lychnis viscaria, in three populations differing in their inbreeding history and population size by measuring several traits at two nutrient levels over the plant's life cycle. The observed levels of inbreeding depression (cumulative inbreeding depression, from −0.057 to 0.629) were high for a plant with a mixed mating system. As expected, the population with a low level of isozyme variation expressed the least inbreeding depression for seed germination. Highest inbreeding depression for germination was found in the largest and genetically most variable population. No clear differences between populations in expression of inbreeding depression in the later life stages were found. The population level inbreeding depression varied with the nutrient conditions and among populations and life stages, but we found no evidence that inbreeding depression increased with lower nutrient availability. These results emphasize the importance of measuring inbreeding depression under several environmental conditions and over life stages.
Functional associations of floret and inflorescence traits among grass species
Authors: Friedman Jannice , Harder Lawrence D.
Published: February 2008

The aerodynamics of wind pollination selects for an intimate relation between form and function in anemophilous plants. Inflorescence architecture and floral morphology vary extensively within the Poaceae, but the functional implication of this variation remains largely unknown. Here we quantify associations between floret, culm, and inflorescence characteristics for 25 grass species in Kananaskis, Alberta, Canada, and consider whether different architectures may implement unique mechanisms to aid pollination. The species cluster into four categories defined by all combinations of floret size (small vs. large) and inflorescence architecture (compact vs. diffuse). Species differed significantly for all 18 traits that we measured, with 12 traits differing only between floret‐size classes, three differing only between inflorescence types, and three differing among both (independently or by an interaction). Based on these morphological associations, we discuss the aerodynamic and functional consequences of each category for wind pollination. The independence of inflorescence and floral traits has probably allowed exploration of all possible combinations of inflorescence architecture and floret size during the evolution of the Poaceae.
Development of the calcium oxalate crystal macropattern in pomegranate (Punica granatum, Punicaceae)
Authors: Lersten Nels R. , Horner Harry T.
Published: February 2008

Oxalate crystals are very common in angiosperms, but few descriptions of their macropattern (crystal types, their tissue distribution, and development) exist. Because unusually large prismatic crystals and druses, are known from pomegranate, we traced the development of crystal macropattern in various‐aged leaf samples from a living plant and from herbarium specimens using unstained whole mounts (some bleached and cleared), stained leaf samples, and leaf and stem cross sections. Preparations were viewed with bright‐field light microscopy and with crossed polarizers. Prismatics appear first in the subapical mid‐mesophyll layer of a leaf 650 μm long. Additional prismatics form basipetally in the enlarging lamina. A preemptive wave of small prismatics appears basipetally in the midrib. Druses form secondarily acropetally in petiole and midrib, while existing lamina prismatics enlarge and new ones develop among them in mid‐mesophyll. Prismatics produced early expand vertically, and many eventually extend from epidermis to epidermis. Later‐formed prismatics attain intermediate sizes. No crystals form along lamina veins, but in older leaves, druses occur in spongy mesophyll, mostly near major vein junctions. In the stem, druses are restricted to phloem fibers. No phloem fibers occur in the leaf trace or midvein; therefore, petiolar and midrib druses are only in parenchyma, not in phloem.
Determinants of species rarity: population growth rates of species sharing the same habitat
Authors: Münzbergová Zuzana
Published: February 2008

Determining differences between common and rare species is commonly used to identify factors responsible for rarity. Existing studies, however, suffer from two important drawbacks. First, studies compare species that are closely related phylogenetically but occupy different habitats. Second, these studies concentrate on single life history traits, with unknown relevance for population growth rates. Complete life cycles of one rare and one common Cirsium species sharing the same habitat were compared. Population growth rate was slightly lower in the rare species, translating into a large difference in local extinction probability. Seed predation intensity did not differ between species. However, it can be demonstrated that in connection with the data on complete demography, seed predation is the key factor causing a lower population growth rate in the rare species. These results are the first estimation of factors responsible for commonness or rarity of plants in terms of population growth rate without confounding differences in ecology. They demonstrate that conclusions based on single traits may be misleading and that only a comparison based on a complete life cycle can provide unequivocal evidence for concluding which factors are really those responsible for species commonness or rarity.
Genetic variation and relationships among Ulex (Fabaceae) species in southern Spain and northern Morocco assessed by chloroplast microsatellite (cpSSR) markers
Authors: Cubas Paloma , Pardo Cristina , Tahiri Hikmat
Published: February 2008

Genetic variation in 27 populations of Ulex species from southern Spain and northern Morocco (Betic‐Rif arc) was assessed using 11 chloroplast microsatellite (cpSSR) markers, which revealed 47 different haplotypes. These nonrecombinant, haploid markers allow measurement of genetic variation in closely related species of Ulex where molecular phylogenetic analyses have not provided a clear view of interspecific relationships. Discriminant analysis indicates that the haplotypes are useful to differentiate among species, and analysis of molecular variance (AMOVA) shows high levels of differentiation among populations. The minimum spanning tree (MST), that represents the connections between the haplotypes, suggests that the eastern Rifean U. africanus haplotypes are more genetically related than those from southern Spain. The latter may have lost genetic diversity while colonizing new habitats, eventually differentiating into U. baeticus and U. scaber. Hybridization between these populations, followed by polyploidization, may have originated the tetraploids (U. congestus and U. borgiae) that colonized new habitats associated with acidic rocks. Separate groupings of U. scaber populations may indicate multiple origins from different stocks. Diversification in this group of Ulex species could be related to the opening of the Alboran Sea by Middle Miocene, when the populations from Morocco and Spain became isolated from each other.
Relationships within tribe Lycieae (Solanaceae): paraphyly of Lycium and multiple origins of gender dimorphism
Authors: Levin Rachel A. , Miller Jill S.
Published: February 2008

We infer phylogenetic relationships among Lycium, Grabowskia, and the monotypic Phrodus microphyllus, using DNA sequence data from the nuclear granule‐bound starch synthase gene (GBSSI, waxy) and the chloroplast region trnT‐trnF. This is the first comprehensive molecular phylogenetic study of tribe Lycieae (Solanaceae). In addition to providing an understanding of evolutionary relationships, we use the phylogenetic hypotheses to frame our studies of breeding system transitions, floral and fruit evolution, and biogeographical patterns within Lycieae. Whereas Lycium is distributed worldwide, Phrodus and the majority of Grabowskia species are restricted to South America. Tribe Lycieae is strongly supported as monophyletic, but Lycium likely includes both Grabowskia and Phrodus. Results also suggest a single dispersal event from the Americas to the Old World, and frequent dispersal between North and South America. The diversity of fruit types in Lycieae is discussed in light of dispersal patterns and recent work on fruit evolution across Solanaceae. Dimorphic gender expression has been studied previously within Lycium, and results indicate that transitions in sexual expression are convergent, occurring multiple times in North America (a revised estimate from previous studies) and southern Africa.
Molecular systematics of the trans‐Pacific alpine genusOreomyrrhis(Apiaceae): phylogenetic affinities and biogeographic implications
Authors: Chung Kuo‐Fang , Peng Ching‐I , Downie Stephen R. , Spalik Krzysztof , Schaal Barbara A.
Published: February 2008

The alpine ecosystem is the only terrestrial biogeographic unit that is distributed globally. Studying phylogenetics of the plant species in this widespread ecosystem can provide insights into the historical biogeographic processes that have shaped the global biodiversity. The trans‐Pacific disjunct alpine genusOreomyrrhis(Apiaceae) was investigated using nrDNA ITS sequences to test the taxonomic and biogeographic hypotheses. Phylogenetic analyses using maximum parsimony, maximum likelihood, and Bayesian inference revealed that species ofOreomyrrhisform a weakly supported monophyletic clade that is nested withinChaerophyllumsect.Chaerophyllum(subtribe Scandicinae, tribe Scandiceae). The optimal solutions of dispersal‐vicariance analysis indicate that the ancestor ofChaerophyllumsect.Chaerophyllum(includingOreomyrrhis) was distributed in Eurasia and subsequently dispersed to North America and southern Pacific Rim. Based on dating using ITS sequence variation, these dispersal events were most likely recent, probably during late Tertiary to Quaternary. The structure of the ITS haplotype network suggests that a rapid range expansion via long‐distance dispersal had been crucial in generating the trans‐Pacific disjunction ofOreomyrrhis. Furthermore, evolution toward smaller mericarp size and a transition from outcrossing to selfing duringOreomyrrhis's evolution might have increased the chances for long‐distance dispersal, facilitating its range expansion and occupation on alpine environments.
Chloroplast DNA phylogeny of the woody Sonchus alliance (Asteraceae: Sonchinae) in the Macaronesian Islands
Authors: Lee Chunghee , Kim Seung‐Chul , Lundy Karen , Santos‐Guerra Arnoldo
Published: February 2008

Determining accurate phylogenetic relationships among the members of the woody Sonchus alliance presents challenges because of an insufficient level of molecular variation and the convergent evolution of similar morphological traits in island settings. To obtain a better resolved phylogeny and to test the potential role of hybridization and introgression, we sequenced all members of the alliance with multiple populations for the ITS of nrDNA and over 4000 base pairs of coding and noncoding regions of cpDNA. The cpDNA phylogeny is not well resolved in the core members of the alliance (i.e., subg. Dendrosonchus and genus Taeckholmia), but like the ITS tree, it has identified basal lineages of monotypic genera. The cpDNA data set was not significantly different from that of ITS, and subsequent combined analysis provided a better resolved and supported phylogeny within the alliance. The combined ML tree identified the same basal lineages, suggested nonmonophyly of Dendrosonchus and Taeckholmia, and did not support either Boulos' or Aldridge's infrasubgeneric classification system. Assessment of the role of hybridization and introgression was limited due to poor resolution in the cpDNA phylogeny. The combined analysis supports a Gran Canaria origin for the alliance and two subsequent long distance dispersal events to Madeira and Cape Verde islands.
Is there a cost to resprouting? Seedling growth rate and drought tolerance in sprouting and nonsprouting Ceanothus (Rhamnaceae)
Authors: Schwilk Dylan W. , Ackerly David D.
Published: February 2008

Many woody plant species that depend upon fire‐cued seed germination lack the ability to resprout. As the ability to resprout is widely assumed to be the ancestral condition in most plant groups, the failure to sprout is an evolutionary derived trait. Models for the evolutionary loss of sprouting assume a trade‐off between seedling success and vegetative resprouting ability of adults. Such models require higher seedling success rates in nonsprouters than in sprouters. On the other hand, there seem to be few a priori reasons why a strong sprouter might not also have highly competitive post‐fire seedlings. To test the hypothesis that nonsprouting plants have higher growth rates and/or drought survival, we grew seedlings of Ceanothus tomentosus from sprouting and nonsprouting populations in a common garden experiment. Each of these C. tomentosus populations was paired with a sympatric Ceanothus species that differed in resprouting ability. Sprouters exhibited greater allocation to root carbohydrate storage than did nonsprouters, but overall relative growth rates did not differ. Nonsprouters had earlier onset of flowering. These results provide mixed support for models of a sprouting/nonsprouting allocation trade‐off.
Onset of flowering and climate variability in an alpine landscape: a 10‐year study from Swedish Lapland
Authors: Molau Ulf , Nordenhäll Urban , Eriksen Bente
Published: February 2008

Long‐term studies on phenology are rarely reported from arctic and alpine areas, but are essential for understanding biotic and abiotic controls on flowering. We monitored first flowering day (FFD) for 144 species in a subarctic–alpine area in Swedish Lapland over a period of 10 yr (1992–2001). Temperature and global radiation were monitored continuously, and snowcover duration was observed. Thawing degree‐days and snowcover duration (exposure) were the dominant environmental controls on phenology. We introduce a lability index (LI) to describe the interannual variability in FFD among species. The temporal sequence of species is very constant among years, although a few species are more labile. The species were also classified into the catagories “Functional type,” “Raunkiær's life form,” and “Sørensen's wintering floral type.” The last two reflected the environmental data best, and together with “Exposure” they were combined into a phenology index (PI). The index was subsequently used in a triangular ordination together with FFD. The ordination illustrates whether species flower earlier or later than expected from their preconditions. We hypothesize that species having a delayed flowering respond more readily to global warming than species having an already optimized flowering.
Only seed size matters for germination in different populations of the dimorphic Tragopogon pratensis subsp. pratensis (Asteraceae)
Authors: van Mölken Tamara , Jorritsma‐Wienk Linda D. , van Hoek Paul H. W. , de Kroon Hans
Published: February 2008

Many studies have focused on the ecology of seed dimorphism, the production of two seed types by a single plant. Morphology and seed size are usually correlated, but how morphology affects germination percentage and seedling growth is poorly understood. Here we explicitly separate these effects for nine populations of the dimorphic species Tragopogon pratensis subsp. pratensis. Larger seeds yielded higher germination percentages, yet seed morphology had no additional direct effect on germination. Neither seed size nor seed morphology affected seedling growth. Neither germination nor seedling growth varied among populations, but seed head varied significantly. Results show that germination is mainly controlled by seed size rather than by seed morphology. This study is one of the few to distinguish explicitly between seed size and seed morphology effects on ecological characteristics and suggests that seed dimorphism may exert its ecological effects predominantly through its correlated size.
Fruit maturation, not deteriorating light conditions, is the primary cue of senescence in a spring ephemeral annual plant—Floerkea proserpinacoides (Limnanthaceae)
Authors: Mokhtar Ines Ben , Houle Gilles
Published: February 2008

In monocarpic plants, reproduction is closely associated with senescence, which is itself often correlated to specific environmental signals. Floerkea proserpinacoides (Limnanthaceae) is a spring ephemeral annual of the deciduous forests of eastern North America. The phenology of its growth and reproduction is considered to be a specific adaptation to the short period during which there is a high availability of resources (mostly light). Indeed, flowering starts 2–3 wk following seedling emergence soon after snowmelt and continues until tree canopy closure. However, fruit maturation is postponed for several weeks and is followed by the plant's death. The objective of this study is to determine if senescence in F. proserpinacoides is primarily cued by fruit maturation or deteriorating light conditions associated with tree canopy closure. Plants for which reproductive investment was manipulated by removing their carpels were grown either in full light or in the shade. Carpel‐removal plants reached a higher biomass than control plants (46.0– 57.5% higher), especially in full light. However, longevity was greater in carpel‐removal plants, particularly in the shade (25.3–37.8% greater). These results thus suggest that fruit maturation, not deteriorating light conditions associated with canopy closure, is the primary cue of plant senescence in F. proserpinacoides.
Rainfall exclusion in an eastern Amazonian forest alters soil water movement and depth of water uptake
Authors: Romero‐Saltos Hugo , Sternberg Leonel da S. L. , Moreira Marcelo Z. , Nepstad Daniel C.
Published: February 2008

Deuterium‐labeled water was used to study the effect of the Tapajós Throughfall Exclusion Experiment (TTEE) on soil moisture movement and on depth of water uptake by trees of Coussarea racemosa, Sclerolobium chrysophyllum, and Eschweilera pedicellata. The TTEE simulates an extended dry season in an eastern Amazonian rainforest, a plausible scenario if the El Niño phenomenon changes with climate change. The TTEE excludes 60% of the wet season throughfall from a 1‐ha plot (treatment), while the control 1‐ha plot receives precipitation year‐round. Mean percolation rate of the label peak in the control plot was greater than in the treatment plot during the wet season (0.75 vs. 0.07 m/mo). The rate was similar for both plots during the dry season (ca. 0.15 m/mo), indicative that both plots have similar topsoil structure. Interestingly, the label peak in the control plot during the dry season migrated upward an average distance of 64 cm. We show that water probably moved upward through soil pores—i.e., it did not involve roots (hydraulic lift)—most likely because of a favorable gradient of total (matric + gravitational) potential coupled with sufficient unsaturated hydraulic conductivity. Water probably also moved upward in the treatment plot, but was not detectable; the label in this plot did not percolate below 1 m or beyond the depth of plant water uptake. During the dry season, trees in the rainfall exclusion plot, regardless of species, consistently absorbed water significantly deeper, but never below 1.5–2 m, than trees in the control plot, and therefore may represent expected root function of this understory/subcanopy tree community during extended dry periods.
Relative humidity and temperature modify the mechanical properties of isolated tomato fruit cuticles
Authors: Matas Antonio J. , López‐Casado Gloria , Cuartero Jesús , Heredia Antonio
Published: February 2008

The mechanical properties of enzymatically isolated cuticular membrane (CM) from ripe tomato fruits were investigated at 10 to 45°C and relative humidity (RH) of 40 to wet. CM samples were stressed by uniaxial tension loads to determine their tensile modulus, E, breaking stress (strength), σmax, and maximum elongation, ϵmax. The CM stress–strain curves revealed a biphasic behavior when tested at RH values below wet conditions. In the first phase, CM responded to the loads by instantaneous extension with no further extension recorded until a further load was added: defined as pure elastic strain (Ee). In the second phase, CM responded by instantaneous extension and by some additional time‐dependent extension, defined as viscoelastic strain (Ev). When CMs were submerged in aqueous solution (wet), the stress–strain curves were monophasic, with both elastic and viscoelastic strain. Ee depended on RH and was higher than Ev, which was independent of RH. Temperature decreased Ee and σmax of tomato fruit CM. Temperature response was not linear but consisted of two temperature‐independent phases separated by a transition temperature. This transition zone has been related previously to the presence of a secondary phase transition in the cutin matrix of the tomato fruit CM.
An overview of the phylogenetic relationships within Epidendroideae inferred from multiple DNA regions and recircumscription of Epidendreae and Arethuseae (Orchidaceae)
Authors: van den Berg Cássio , Goldman Douglas H. , Freudenstein John V. , Pridgeon Alec M. , Cameron Kenneth M. , Chase Mark W.
Published: February 2008

Phylogenetic relationships within the epidendroid orchids with emphasis on tribes Epidendreae and Arethuseae were assessed with parsimony and model‐based analyses of individual and combined DNA sequence data from ITS nuclear ribosomal DNA and plastid trnL intron, the trnL‐F spacer, matK (gene and spacers), and rbcL regions. Despite the absence of boostrap support for some of the relationships, a well‐resolved and supported consensus was found, for which most clades were present in more than one individual analysis. Most clades of this consensus attained high posterior probabilities with a Bayesian approach. Circumscription of Arethuseae and Epidendreae are different from most orchid systems based on morphology, but they correspond to a combination of patterns from several less comprehensive orchid phylogenetic analyses previously published. A new circumscription of Epidendreae includes only Neotropical subtribes (Bletiinae, Chysiinae, Laeliinae, Ponerinae, and Pleurothallidinae), whereas Arethuseae include Coelogyninae (all Old World) and Arethusinae (pantropical). Many previously included genera will need to be moved to other tribes. Taxa previously assigned to be Old World Epidendreae are related to different groups of Old World orchids, and this study can serve as a guide for sampling strategies in future studies to resolve troublesome epidendroid orchid clades.
Phylogenetic relationships among New Caledonian Sapotaceae (Ericales): molecular evidence for generic polyphyly and repeated dispersal
Authors: Bartish Igor V. , Swenson Ulf , Munzinger Jérôme , Anderberg Arne A.
Published: February 2008

The phylogeny of a representative group of genera and species from the Sapotaceae tribe Chrysophylleae, mainly from Australia and New Caledonia, was studied by jackknife analyses of sequences of nuclear ribosomal DNA. The phylogeny conflicts with current opinions on generic delimitation in Sapotaceae.PouteriaandNiemeyera, as presently circumscribed, are both shown to be nonmonophyletic. In contrast, all species currently assigned to these and other segregate genera confined to Australia, New Caledonia, or neighboring islands, form a supported clade. Earlier classifications in which more genera are recognized may better reflect relationships among New Caledonian taxa. Hence, there is need for a revision of generic boundaries in Chrysophylleae, and particularly within thePouteriacomplex, includingLeptostylis,Niemeyera,Pichonia,Pouteriapro parte (the main part of sectionOligotheca), andPycnandra. SectionOligothecahave been recognized as the separate genusPlanchonella, a monophyletic group that needs to be resurrected. Three clades with strong support in our jackknife analysis have one Australian species that is sister to a relatively large group of New Caledonian endemics, suggesting multiple dispersal events between this small and isolated tropical island and Australia. The phylogeny also suggests an interesting case of a relatively recent and rapid radiation of several lineages of Sapotaceae within New Caledonia.
Cuticular anatomy of Sphenobaiera huangii (Ginkgoales) from the Lower Jurassic of Hubei, China
Authors: Wang Yongdong , Guignard Gaëtan , Thévenard Frédéric , Dilcher David , Barale Georges , Mosbrugger Volker , Yang Xiaoju , Mei Shengwu
Published: February 2008

Sphenobaiera huangii (Sze) Hsü is typical Early Mesozoic fossil foliage of Ginkgoales in China. It has been recorded from the Upper Triassic to the Lower Jurassic. The cuticular anatomy is investigated based on material from the type locality, Lower Jurassic Hsiangchi Formation, Zigui County, Hubei Province. The specimens are similar to S. huangii, but contain new information about leaf morphology and cuticular anatomy. Lower and upper cuticle is investigated using light and electron microscopy (LM, SEM, and TEM). Many features are described for the first time, including general structures of lower and upper cuticle, stomata, papillae, and cuticular ultrastructure. At the ultrastructural level, two layers have been distinguished in both lower and upper cuticle, including a homogeneous outer layer with granules and a heterogeneous inner layer with fibrils. Based on a literature comparison between S. huangii and other relevant species of Sphenobaiera, S. huangii may represent the best‐known taxon in the genus Sphenobaiera in both leaf morphology and cuticular structures. This study provides the first detailed ultrastructural data on the leaf cuticle of Sphenobaiera, one of the oldest foliage taxa of Ginkgoales, and offers further evidence for potential discussion on the taxonomic relationships of S. huangii with other ginkgoalean taxa.
Pollen competition among two species of Senecio (Asteraceae) that form a hybrid zone on Mt. Etna, Sicily
Authors: Chapman Mark A. , Forbes David G. , Abbott Richard J.
Published: February 2008

Hybridization between interfertile, sympatric or parapatric, plant species can be reduced significantly by conspecific pollen advantage (CPA), whereby conspecific pollen has an advantage over heterospecific pollen in terms of ovule fertilization. We examined CPA in two interfertile species of Senecio, S. aethnensis, and S. chrysanthemifolius (Asteraceae), which form a hybrid zone on Mt. Etna, Sicily. Individuals of both species were pollinated with pollen mixtures containing 0, 25, 50, 75, or 100% heterospecific pollen, and offspring were genotyped to determine if they were products of conspecific or heterospecific pollen fertilizing the ovules. The mean proportion of hybrid offspring produced on S. aethnensis plants was not significantly different to that expected based on the proportion of heterospecific pollen applied to the flower head. However, S. chrysanthemifolius mother plants showed moderate CPA, with the proportion of hybrid offspring significantly less than expected. Seed set or seed germination was not reduced, hence the CPA found for S. chrysanthemifolius acts before ovule fertilization. The consequences of asymmetry in CPA on the reproductive isolation of S. aethnensis are briefly discussed, along with other mechanisms that may play a role in the maintenance of the hybrid zone on Mt. Etna.