Mineral nutrient stoichiometric variability in Hedera helix (Araliaceae) seeds

Background and Aims

The analysis of variability in mineral allocation to seeds has rarely been considered in relation to allometric patterns and deviations from the allometric trajectory. Here, I examine the scaling of carbon (C), nitrogen (N), phosphorus (P) and sulfur (S) with seed mass in field-collected seeds of Hedera helix, taking into account that brood size might influence the allocation patterns.

Methods

C, N and S contents of 56 individual seeds of different sizes were analysed by combustion using a standard automated CNHS procedure. P content was determined for 200 individual seeds using spectrophotometry after acid digestion of ashed samples. This sample included seeds from different brood sizes.

Key Results

C and N content both varied isometrically with seed mass and this variable explained most of the variation in their content in seeds. P and S, however, varied allometrically with seed mass. Additionally, seed mass only explained 37·3 % and 37·6 % of the total variance in P and S content, respectively. Seeds with higher mass contained proportionately more P and, furthermore, the seeds from small broods contained proportionally more P than those from large broods.

Conclusions

Although seed mass in this species can be used as a surrogate of investment in C and N, it does not account for variability in allocation of nutrients such as P and S. The fact that larger seeds increased their P concentration when found in smaller broods might be a consequence of intense competition for this nutrient among developing seeds. Then, brood size may influence the mineral nutrient concentration of seeds.     

Chloroplast evidence for the multiple origins of the hybrid Potamogeton × fluitans

Previous studies of Potamogeton × fluitans Roth. have supported the putative origin of this taxon as a result of hybridization between Potamogeton lucens L. and Potamogeton natans L. In the British Isles P. × fluitans is restricted to only a few sites, while both its parents are relatively common. Previous studies have shown that most of these hybrid populations are monomorphic, with the exception of the Moors River, in Hampshire and Dorset, where multiple genotypes have been identified. This is despite the fact that here the hybrid grows in the absence of one its parents, P. lucens. In this study, species-specific differences in the TrnL (UAA) chloroplast region, a maternally inherited marker, were used to identify the original seed-bearing parent of the hybrids within this river system. It was shown that both species have been maternal parents in the creation of this hybrid population.     

Quantitative morphology and species delimitation under the general lineage concept: Optimization for Hedera (Araliaceae)

? Premise of the study: The use of continuous morphological characters in taxonomy is traditionally contingent on the existence of discrete diagnostic characters. When plant species are the result of recent divergence and gene flow and/or hybridization occur, the use of continuous morphological characters may help in species identification and delimitation. Between nine and 15 species have been recognized in the last treatments of Hedera. The recent divergence of the species and the involvement of allopolyploidization as the main force in this process may have greatly impeded the establishment of clear limits and contributed to multiple taxonomic proposals. ? Methods: A multivariate statistical decision-making procedure was applied to 56 quantitative morphological characters and 602 specimens to identify and delimit Hedera species under the general lineage concept. Species' exclusive genetic ancestry was evaluated with the genealogical sorting index from the Bayesian inference trees of 30 Hedera ITS sequences. ? Key results: The decision-making procedure allowed recognizing 12 species and two groups (stellate and scale-like trichome groups) in Hedera and provided statistical support for making decisions about long-standing taxonomic controversies. Common ancestry was detected for the populations of three species even in the absence of the species monophyly. ? Conclusions: Quantitative variation supports discrete variation and provides statistical support for the taxa recognized in some recent proposals of Hedera. The need of explicit analysis of quantitative data are claimed to reduce taxonomic subjectivity and ease decision-making when qualitative data fail.     

Pollinator effectiveness and fruit set in common ivy, Hedera helix (Araliaceae)

Flowers of common ivy (Hedera helix L.) provide late season pollen and nectar for several insect groups, and its fruits are a winter and spring food source for frugivorous birds. Ivy benefits from insect pollination in order to set fruit, but it is unknown which flower-visiting insects are the most effective pollinators. Our observations suggest that Vespula wasps are potentially the most effective pollinators since they were frequent visitors, had relatively fast foraging rates, carried large numbers of pollen grains on their bodies and had the highest ‘Pollination potential PP index’ score (a measure of pollinator effectiveness) of all the insect groups examined. There was also a positive linear relationship between the proportion of ivy flowers that set fruit and wasp foraging activity in 0.5 m² quadrats. Visits by Vespula wasps may therefore be important for ensuring a supply of ivy fruits for birds.     

Molecular evidence for hybrid origins of the invasive polyploids Carthamus creticus and C. turkestanicus (Cardueae, Asteraceae)

The hexaploids Carthamus creticus and C. turkestanicus are noxious weeds with wide but non-overlapping Mediterranean distributions, and C. creticus, together with another polyploid, C. lanatus, have also invaded similar climatic regions in North and South America, South Africa and Australia. Here we infer their origins using sequences of the plastid intergenic spacer trnH-psbA and the intron trnK and three introns of nuclear low-copy genes of the RNA Polymerase family (RPD2 and the duplicated RPC2), as well as RAPD markers (random amplified polymorphic DNA). Phylogenetic analyses of the nuclear introns and additivity analysis of the RAPD markers support the hypotheses that the two hexaploids are allopolyploids sharing a tetraploid progenitor lineage represented by the broadly Mediterranean C. lanatus, combined with different diploid progenitor lineages consistent with the different geographic distributions of the hexaploids. Whereas C. leucocaulos from the south-eastern Greek Islands represents the diploid progenitor lineage of the western C. creticus, the Irano-Turanian C. glaucus represents the diploid progenitor lineage of the eastern C. turkestanicus. The plastid data suggest that the diploid lineages served as the maternal progenitors of the hexaploids.     

Chloroplast microsatellites reveal that metallicolous populations of the Mediterranean shrub Cistus ladanifer L have multiple origins

Cistus ladanifer L. (Cistaceae) is a Mediterranean shrub covering different kinds of soils in the Western Mediterranean area. This species has colonised several metalliferous areas (serpentine outcrops as well as human-polluted sites) throughout its distribution range, and is therefore an interesting species to study the possible effects on genetic diversity and differentiation produced by the colonisation of areas polluted with heavy metals. The genetic structure of 33 natural populations distributed across its entire natural distribution range (Morocco, Portugal and Spain) and growing on either metalliferous or non-metalliferous soils was investigated using chloroplast microsatellites. Population genetic parameters were estimated and genetic groups were identified using Bayesian inference. In addition, we compared the genetic diversity and differentiation among metallicolous and non-metallicolous populations within each Bayesian-defined group. The cpSSR data suggested that metallicolous populations of Cistus ladanifer have arisen through multiple independent evolutionary origins within two different chloroplast lineages. Evidence that the soil type provoked genetic bottlenecks in metallicolous populations or genetic differentiation among metallicolous and non-metallicolous populations was not observed. Historical factors are the main cause of the present genetic structure of C. ladanifer. The nature of tolerance to heavy metals as a species-wide trait in this shrub is discussed.     

Frasnian (Upper Devonian) evidence for multiple origins of seed-like structures

Reproductive structures of Frasnian (early Late Devonian) age from Wuhan, Hubei province, South China provide evidence for the early emergence of monomegaspory and integumentation in plants of non-progymnosperm affinity. Sphinxia wuhania gen. et sp. nov. pre-dates the occurrence of other reproductive structures exhibiting a similar suite of characters and adds support to the view that evolution towards an ovule may not have been a unique event. Sphinxia possesses a single functional megaspore with associated aborted members of the meiotic tetrad, a distinct, striated sporangial wall, and a sterile envelope bearing proximal spines. The morphology of the structure precludes assignment to any known group of plants in the absence of additional information regarding the parent plant. A progymnospermous affinity is unlikely. Thus, Sphinxia demonstrates that the Devonian progymnosperms did not lack potential competition from similarly specialized reproductive strategies in other plant lineages.     

DNA evidence for multiple origins of intergeneric allopolyploids in annualMicroseris (Asteraceae)

Seventy populations of North American annualMicroseris, Stebbinsoseris, andUropappus species were examined for chloroplast and nuclear ribosomal DNA restriction site variability to determine the origin of the allotetraploid speciesS. heterocarpa andS. decipiens. Previously identified chloroplast DNA restriction site variants were used in concert with restriction site variation forNco I in the nuclear-encoded ribosomal DNA repeat. The presence of two, mutually exclusive restriction site gains were observed in diploid populations ofM. douglasii; these same variants were also found in populations of allotetraploidS. heterocarpa, indicating mutiple origins of this species from different maternal diploid populations ofM. douglasii. Variation in the rDNA repeat between the diploid annual species and the putative paternal genome ofU. lindleyi was found to be additive inS. heterocarpa. A similar relationship was observed for the origin ofS. decipiens; cpDNA restriction site variants found inM. bigelovii andM. douglasii were present inS. decipiens. The rDNANco I variants also were additive in this purported allotetraploid. These results confirm the reticulate evolutionary pattern inStebbinsoseris and provide another example of multiple origins of intergeneric allopolyploids.     

Polyploidy and invasion of English ivy (Hedera spp., Araliaceae) in North American forests

Polyploidy is a common feature of agricultural weeds and natural area invaders. There are few studies comparing related diploid and polyploid exotics, however, and it is unclear what ecological and genetic factors favor the establishment of weedy polyploids. This research characterizes the geographic distribution and phenotypic characteristics of diploid Hedera helix and tetraploid Hedera hibernica, European species that are invading North American forests. To confirm the taxonomic affinity of invasive plants, we sequenced five non-coding cpDNA regions for 108 individuals (105 populations) as well as reference samples representing all species in the genus Hedera. Because diploid H. helix and tetraploid H. hibernica are poorly distinguished by morphology and DNA sequence, we used flow cytometry to determine their distribution (585 individuals). More than 90 % of sampled plants had cpDNA sequences identical or similar to H. helix sensu lato and H. hibernica. Diploid H. helix was dominant on the U.S. east coast (78.5 % of sampled plants) while tetraploid H. hibernica was dominant on the U.S. west coast (72.2 % of sampled plants), mirroring the species’ occurrence in maritime versus continental climates of Europe. Moreover, for sympatric occurrences in the Pacific Northwest, H. hibernica was larger and more frequently reproductive than H. helix. In a 2-year garden experiment, tetraploid H. hibernica had substantial architectural differences compared to diploid H. helix, including larger (but less numerous) leaves and thicker (but less branched) stems. Field experiments are needed to evaluate “pre-adaptation” (directional ecological filtering) and other factors mediating the invasion of H. helix and H. hibernica.     

Deciphering the origins of apomictic polyploids in the Cheilanthes yavapensis complex (Pteridaceae)

Deciphering species relationships and hybrid origins in polyploid agamic species complexes is notoriously difficult. In this study of cheilanthoid ferns, we demonstrate increased resolving power for clarifying the origins of polyploid lineages by integrating evidence from a diverse selection of biosystematic methods. The prevalence of polyploidy, hybridization, and apomixis in ferns suggests that these processes play a significant role in their evolution and diversification. Using a combination of systematic approaches, we investigated the origins of apomictic polyploids belonging to the Cheilanthes yavapensis complex. Spore studies allowed us to assess ploidy levels; plastid and nuclear DNA sequencing revealed evolutionary relationships and confirmed the putative progenitors (both maternal and paternal) of taxa of hybrid origin; enzyme electrophoretic evidence provided information on genome dosage in allopolyploids. We find here that the widespread apomictic triploid, Cheilanthes lindheimeri, is an autopolyploid derived from a rare, previously undetected sexual diploid. The apomictic triploid Cheilanthes wootonii is shown to be an interspecific hybrid between C. fendleri and C. lindheimeri, whereas the apomictic tetraploid C. yavapensis is comprised of two cryptic and geographically distinct lineages. We show that earlier morphology-based hypotheses of species relationships, while not altogether incorrect, only partially explain the complicated evolutionary history of these ferns.     

Chloroplast DNA variation of Panax (Araliaceae) in Nepal and its taxonomic implications

The restriction site and size variation of five PCR amplified fragments of noncoding chloroplast DNA (cpDNA) was examined in material from 13 populations ofPanax from Nepal and China. Fourteen restriction endonucleases produced 81 restriction site and length variations from the large single-copy region of cpDNA, 27 of which are polymorphic. The cpDNA dataset suggests two distinct groups ofPanax from Nepal (clades I and II). Clade I consists of two populations ofP. pseudoginseng subsp.pseudoginseng, and clade II is composed of material referable toP. pseudogingeng subsp.himalaicus (vars.himalaicus, angustifolius, andbipinnatifidus). The three accessions ofP. pseudoginseng subsp.japonicus andP. ginseng studied from China had cpDNA characters that differed from the HimalayanPanax. The highly distinctive cpDNA profile and morphology ofP. pseudoginseng subsp.pseudoginseng sensu Hara (1970) from central Nepal support its status as a separate species, which has an extremely restricted distribution.     

The distribution of diploids and polyploids of the Scilla scilloides complex in Korea

A total of 3 384 individuals of Scilla scilloides Druce were sampled from 40 natural populations at 35 different localities over the Korean Peninsula and analysed cytogenetically. The following cytogenetic types were found: AA (19.6%), AABB (72.4%), ABBB (4.3%), AABBB (3.0%) and aneuploids (0.8%). Of these, AA was found in 9 populations along the west side of the Korean Peninsula facing the Yellow Sea and on Yeongdo and Jeju Islands. Type AABB, the most common type in the complex, was found in 33 natural populations on the Korean Peninsula and Jeju Island. The distributions of ABBB and AABBB are restricted to the southern part of the Korean Peninsula and Jeju Island; they were found in 8 natural populations. In southern Korea the above four types showed overlapping distribution and two or three were often found growing together.Genome A, occurring in the three allopolyploids in the Korean Peninsula, was the same as that in allopolyploids in Japan. However, genome A occurring as AA diploids was karyotypically different from that in the allopolyploids. On the basis of distribution patterns and cytological features, the origin of the allopolyploids is discussed.     

Amplified fragment length polymorphisms and sequence data in the phylogenetic analysis of polyploids: multiple origins of Veronica cymbalaria (Plantaginaceae)

The origin of polyploid Veronica cymbalaria (Plantaginaceae) was investigated using DNA sequence data and amplified fragment length polymorphism (AFLP) fingerprints to reveal the parentage of this taxon. The use of AFLP fingerprints in phylogenetic analysis is problematic and various methods have therefore been compared. DNA sequence data (for the internal transcribed spacer (ITS) region and the plastid trnL-F region (trnL intron, 3'exon, and trnL-F spacer)) and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the ITS region suggested a reliable hypothesis for the evolution of the V. cymbalaria complex. This hypothesis allowed evaluation of the effect of different distance measures (Jaccard and Nei-Li) in phenetic, character-state weighted parsimony, and Bayesian analyses of AFLP markers. The study establishes that tetraploid V. cymbalaria originated at least twice in the eastern Mediterranean, with one parent differing in the two separate origins. Hexaploid V. cymbalaria originated even more often. The results illustrate that even subtle differences in the analyses of AFLP markers can lead to drastically different conclusions. The study reveals multiple origins of a Mediterranean polyploid species. Furthermore, it demonstrates that the analysis of a complex marker system such as AFLP fingerprints using only one type of analysis can easily be misleading.     

Occurrence and evolutionary origins of polyploids in the clubmoss genus Diphasiastrum (Lycopodiaceae)

Two polyploid taxa are commonly recognized in the genus Diphasiastrum, D. wightianum from Asia and D. zanclophyllum from South Africa and Madagascar. Here we present results from Feulgen DNA image densitometry analyses providing the first evidence for the polyploid origin of D. zanclophyllum. Also reported for the first time are data confirming that D. multispicatum and D. veitchii, representing the putative parent lineages of D. wightianum, are diploids. Phylogenetic analyses of the nuclear regions RPB2, LEAFY and LAMB4 reveal that putative tetraploid accessions are of allopolyploid origin. Diphasiastrum zanclophyllum shows close relationship to the North American taxon D. digitatum on the maternal side, but the paternal relationship is less clear. Two accessions from Asia, both inferred to be polyploid, have D. veitchii as the maternal parent, whereas the paternal paralogs show relationships to D. multispicatum and D. tristachyum, respectively. None of these parental combinations have previously been hypothesized.     

Flower development of Meliosma (Sabiaceae): evidence for multiple origins of pentamery in the eudicots

Flower developmental studies are a complement to molecular phylogenetics and a tool to understand the evolution of the angiosperm flower. Buds and mature flowers of Meliosma veitchiorum, M. cuneifolia, and M. dilleniifolia (Sabiaceae) were investigated using scanning electron microscopy to clarify flower developmental patterns and morphology, to understand the origin of the perianth merism, and to discuss the two taxonomic positions proposed for Sabiaceae, among rosids or in the basal grade of eudicots. Flowers in Meliosma appear pentamerous with two of the five sepals and petals strongly reduced, three staminodes alternating with two fertile stamens opposite the small petals, and a two-carpellate gynoecium. The flower development in Meliosma is spiral without distinction between bracteoles and sepals. Because of this development, sepals, petals, and stamens are almost opposite and not alternating as expected in cyclical pentamerous flowers. In four-sepal flowers the direction of petal initiation is reversed. The symmetry of the flower appears to be transversally zygomorphic, although this is hidden by the almost equal size of the larger petals. Evidence points to a unique pentamerous origin of flowers in Meliosma, and not to a trimerous origin, as earlier suggested, and adds support to multiple origins of pentamery in the eudicots.     

Inclusion of the Vietnamese endemic genus Grushvitzkya in Brassaiopsis (Araliaceae): evidence from nuclear ribosomal ITS and chloroplast ndhF sequences

The phylogenetic position of the recently described monotypic Vietnamese genus Grushvitzkya is evaluated using nuclear ribosomal ITS and chloroplast ndh F sequence data . Grushvitzkya stellata has often been considered as intermediate between Brassaiopsis and Trevesia , but differs in having a 5-locular ovary rather than a 2- or 6–16-locular ovary, respectively. The molecular data indicate that Grushvitzkya is deeply nested within Brassaiopsis and has a close relationship with B. phanrangensis from central and southern Indochina, and B. stellata from the regions bordering China and Vietnam. The Kimura 2-parameter distances of the ITS sequences between G. stellata and B. phanrangensis and B. stellata are 0.403 and 0.945%, respectively. Furthermore, G. stellata and B. phanrangensis have an identical ndh F sequence profile. Grushvitzkya stellata differs from B. stellata by a single nucleotide in their ndh F sequences. The available evidence is compatible with the hypothesis that Grushvitzkya diverged recently from B. phanrangensis and B. stellata . Although these three closely related species all possess stellate trichomes, G. stellata and B. phanrangensis have highly similar trichome micromorphology, with almost no difference in size, shape and branching pattern, supporting a very close relationship between the two taxa. The higher number of locules in the ovary of Grushvitzkya appears to be a secondary increase despite earlier interpretations that higher numbers are evolutionarily primitive. Grushvitzkya is herein merged with Brassaiopsis ; because the combination B. stellata is occupied, a new name, Brassaiopsis grushvitzkyi , is proposed.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 455–463.     

The distribution of diploids and polyploids of theScilla scilloides complex in the northeastern district of China

A cytological analysis was made of 1504 individuals ofScilla scilloides Druce from the northeastern district of China. In terms of genome combination four cytotypes were found: AA (90.95%), AAAA (0.07%), AABB (8.92%) and AABB+2 (0.07%). In the cytotypes A and B denote genome A (x=8) and genome B (x=9), respectively. Most of 18 natural populations examined consist of one cytotype: indeed, all individuals examined of 15 of the populations are AA diploids, those of one population AABB allotetraploids, and individuals examined of two other populations have two cytotypes each, AA and AAAA, and AABB and AABB+2. In karyotype the genome A of the AA and AAAA was different from that of the AABB, and a direction of morphological change of chromosomes in the genome A is discussed in light of results of hybridization experiments reported elsewhere. Taken together with information available for the distribution of different cytotypes in China, Korea and Japan, the results of the present study support the view of Maekawa thatScilla scilloides was native to mainland China and lately introduced to Japan.     

Chloroplast DNA evidence for reticulate evolution in Eucalyptus (Myrtaceae)

Four highly differentiated chloroplast DNA (cpDNA) lineages were identified in the forest tree species Eucalyptus globulus Labill. (Myrtaceae) in Australia using restriction site polymorphisms from Southern analysis. The cpDNA variation did not conform with ssp. boundaries, yet there was a strong geographical pattern to the distribution of the lineages. One lineage (C) was geographically central and widespread, whereas the other three lineages were found in peripheral populations: Western (W), Northern (N) and Southern (S). Thirteen haplotypes were detected in E. globulus , seven of which belonged to clade C. At least three of the cpDNA lineages (C, N and S) were shared extensively with other species. On the east coast of the island of Tasmania, there was a major north–south difference in cpDNA in the virtually continuous distribution of E. globulus . Northern populations harboured haplotypes from clade C while southeastern populations harboured a single haplotype from clade S. This difference was also reflected in several co-occurring endemic species. It is argued that the extensive cpDNA differentiation within E. globulus is likely to originate from interspecific hybridization and 'chloroplast capture' from different species in different parts of its range. Superficially, this hybridization is not evident in taxonomic traits; however, large-scale common garden experiments have revealed a steep cline in quantitative genetic variation that coincides with the haplotype transition in Tasmania. Our cpDNA results provide the strongest evidence to date that hybridization has had a widespread impact on a eucalypt species and indicate that reticulate evolution may be occurring on an unappreciated scale in Eucalyptus .     

Cytogenetic and molecular evidence suggest multiple origins and geographical parthenogenesis in Nothoscordum gracile (Alliaceae)

Background and Aims

Nothoscordum gracile is an apomitic tetraploid widely distributed throughout the Americas and naturalized in many temperate regions of other continents. It has been suggested to form a species complex with sexual and apomictic N. nudicaule and N. macrostemon. Tetraploids of these species also share a structurally heterozygous chromosome complement 2n = 19 (13M + 6A). In this work, the origin of N. gracile and its relationships with its related species was investigated based on cytological and molecular data.

Methods

Cytogenetic analyses were based on meiotic behaviour, CMA bands, localization of 5S and 45S rDNA sites, and genomic in situ hybridization (GISH). Nuclear ITS and plastidial trnL-trnF sequences were also obtained for most individuals.

Key Results

Proximal CMA bands were observed in the long arms of all acrocentrics of 2x and 4x N. macrostemon but not in diploid and some tetraploid cytotypes of N. nudicaule. Samples of N. gracile showed a variable number of CMA bands in the long arms of acrocentrics. Analysis of ITS sequences, dot-blot, GISH, and 5S and 45S rDNA sites, revealed no differentiation among the three species. The trnL-trnF cpDNA fragment showed variation with a trend to geographical structuring irrespective of morphospecies and fully congruent with karyotype variation.

Conclusions

The 2n = 19 karyotype was probably formed by a centric fusion event occurring in N. nudicaule and later transmitted to tetraploid cytotypes of N. macrostemon. Diploids of N. nudicaule and N. macrostemon appeared as consistent recently diverged species, whereas tetraploid apomicts seem to constitute an assemblage of polyploid hybrids originating from multiple independent hybridization events between them, part of which are morphologically recognizable as N. gracile.