Differences in the floral anthocyanin content of red petunias and Petunia exserta

In order to resolve a conflict between previous papers regarding the floral anthocyanins of red flowers of Petunia exserta, a naturally occurring species, the HPLC profile of this species was compared with that of commercial red garden petunias. Both HPLC profiles extremely superficially resemble each other in terms of relative amounts and retention times of the major anthocyanins. However, co-elution on HPLC of the mixed sample resulted in clear separation of the components. Three major anthocyanins in red petunias were determined to be cyanidin 3-sophoroside, cyanidin 3-glucoside and peonidin 3-glucoside, which exhibited similar behaviors on HPLC to delphinidin 3-glucoside. delphinidin-3-rutinoside and petunidin 3-rutinoside, respectively, the major floral anthocyanins of P. exserta.     

Patterns of hybridization and population genetic structure in the terrestrial orchids Liparis kumokiri and Liparis makinoana (Orchidaceae) in sympatric populations

We investigated the potential for gene flow and genetic assimilation via hybridization between common and rare species of the terrestrial orchid genus Liparis, focusing specifically on sympatric and allopatric populations of the common Liparis kumokiri and the rare Liparis makinoana. We utilized analyses of genetic diversity, morphology, and the spatial distributions of individuals and genotypes to quantify the dynamics of interspecific gene flow at within- and among-population scales. High levels of allozyme genetic diversity (HE) were found in populations of the rare L. makinoana (0.317), whereas the common L. kumokiri (N = 1744 from 14 populations) revealed a complete lack of variation. This contrast may reflect different breeding systems and associated rates of genetic drift (L. makinoana is self-incompatible, whereas L. kumokiri is self-compatible). At the two known sympatric sites, individuals were found that recombined parental phenotypes, possessing floral characteristics of L. kumokiri and vegetative characteristics of L. makinoana. These putative hybrids were the only individuals found segregating alleles diagnostic of both parental species. Analysis of these individuals indicated that hybrid genotypes were skewed towards L. kumokiri and later generation recombinants of L. kumokiri at both sympatric sites. Furthermore, Ripley's bivariate L(r) statistics revealed that at one site these hybrids are strongly spatially clustered with L. kumokiri. Nonetheless, the relatively low frequency of hybrids, absence of ongoing hybridization (no F1s or first generation backcrossess), and strong genetic differentiation between morphologically 'pure' parental populations at sympatric sites (FST = 0.708-0.816) indicates that hybridization was not an important bridge for gene flow. The results from these two species suggest that natural hybridization has not played an important role in the diversification of Liparis, but instead support the view that genetic drift and limited gene flow are primarily responsible for speciation in Liparis. Based on genetic data and current status of the species, implications of the research for conservation are considered to provide guidelines for appropriate conservation and management strategies.     

矮牵牛育种研究进展

从常规育种、基因工程育种、体细胞育种和单倍体育种4个方面评述了矮牵牛(Petunia hybrida Vilm.)育种研究进展.国外对矮牵牛育种研究较多,新品种面世推陈出新,国内对其研究则较为薄弱.其常规育种最为成功,不断有新品种推出,基因工程育种也取得了一定成就,已有新品种面世,而体细胞育种及单倍体育种尚无新品种产生,但对这两种方法在育种上应用的可能性和前景作出了一定探索.     

Diversification of plant species in a subtropical region of eastern South American highlands: a phylogeographic perspective on native Petunia (Solanaceae)

In the Southern and Southeastern Brazilian highlands, a clade of seven species of Petunia that are endemic to the region (P. altiplana, P. bonjardinensis, P. guarapuavensis, P. mantiqueirensis, P. reitzii, P. saxicola and P. scheideana) exists in association with grassland formations. These formations are isolated in high-altitude regions, being surrounded by forested areas, and experienced contraction-expansion cycles associated with the glacial cycles of the Pleistocene. To understand the evolutionary history of this group, the divergence of which is probably linked to these past shifts in habitat, we analysed the sequences of the plastidial intergenic spacers trnH-psbA and trnS-trnG from populations throughout the known distributions of all seven species. The common ancestor of this highland clade started to differentiate ～0.9 million years (Myr) ago, which corresponds to a high diversification rate of 2.06 species per Myr in the intervening period. The high level of haplotype sharing among several species in the clade and the absence of reciprocal monophyly suggest the persistence of ancestral polymorphisms during speciation events and/or past hybridization, because no hybrid was found. Four of the five species displayed very low genetic diversity and possessed either one or two haplotypes, which is consistent with long-term isolation in restricted areas. The three more diverse species displayed significant population structure, and P. altiplana showed a clear signs of population growth during the last glacial period. These results suggest that diversification occurred as a result of expansion of the ancestral species of the clade during glacial periods followed by fragmentation and isolation during retraction in interglacial periods.     

High resolution linkage maps of the model organism Petunia reveal substantial synteny decay with the related genome of tomato

Two linkage maps were constructed for the model plant Petunia. Mapping populations were obtained by crossing the wild species Petunia axillaris subsp. axillaris with Petunia inflata, and Petunia axillaris subsp. parodii with Petunia exserta. Both maps cover the seven chromosomes of Petunia, and span 970 centimorgans (cM) and 700 cM of the genomes, respectively. In total, 207 markers were mapped. Of these, 28 are multilocus amplified fragment length polymorphism (AFLP) markers and 179 are gene-derived markers. For the first time we report on the development and mapping of 83 Petunia microsatellites. The two maps retain the same marker order, but display significant differences of recombination frequencies at orthologous mapping intervals. A complex pattern of genomic rearrangements was detected with the related genome of tomato (Solanum lycopersicum), indicating that synteny between Petunia and other Solanaceae crops has been considerably disrupted. The newly developed markers will facilitate the genetic characterization of mutants and ecological studies on genetic diversity and speciation within the genus Petunia. The maps will provide a powerful tool to link genetic and genomic information and will be useful to support sequence assembly of the Petunia genome.     

Isolation barriers between petunia axillaris and Petunia integrifolia (Solanaceae)

The isolation barriers restricting gene flow between populations or species are of crucial interest for understanding how biological species arise and how they are maintained. Few studies have examined the entire range of possible isolation barriers from geographic isolation to next generation hybrid viability. Here, we present a detailed analysis of isolation barriers between two flowering plant species of the genus Petunia (Solanaceae). Petunia integrifolia and P. axillaris feature divergent pollination syndromes but can produce fertile hybrids when crossed in the laboratory. Both Petunia species are primarily isolated in space but appear not to hybridize in sympatry. Our experiments demonstrate that pollinator isolation is very high but not strong enough to explain the absence of hybrids in nature. However, pollinator isolation in conjunction with male gametic isolation (i.e., pollen-pistil interaction) can explain the lack of natural hybridization, while postzygotic isolation barriers are low or nonexistent. Our study supports the notion that reproductive isolation in flowering plants is mainly caused by pre- rather than postzygotic isolation mechanisms.     

一种新型矮牵牛花发育突变体的研究

报道了新发现的一种矮牵牛(Petunia hybrida L.)花发育突变体,命名为efficient(eff),并对这一突变体进行了形态学和遗传学分析。eff突变体主要表现为雌蕊心皮数目的增加和雄蕊上长出花瓣状结构,同时,雄蕊、花瓣和萼片数亦有增多,但营养器官无变化。心皮数目的增加导致雌蕊柱头和子房体积的显著增大,并形成较大的果实。雄蕊上花瓣的形成对花粉的产生无明显影响。扫描电镜观察发现,eff突变体在花器官原基形成时发生了相应数目的增加及特征的变化。遗传学分析表明,突变的表现型符合孟德尔单基因遗传规律。     

Floral scent diversity is differently expressed in emitted and endogenous components in Petunia axillaris lines

BACKGROUND AND AIMS: Among the subspecies of Petunia axillaris are various lines emitting sensorially different scents. Analysis of variations in floral scent among genetically close individuals is a powerful approach to understanding the mechanisms for generating scent diversity. METHODS: Emitted and endogenous components were analysed independently to gain information about evaporation and endogenous production in 13 wild lines of P. axillaris. A dynamic headspace method was used to collect emitted components. Endogenous components were extracted with solvent. Both of these sample types were subjected to quantitative and qualitative analysis by gas chromatography (GC)-flame ionization detector (FID) and GC-mass spectrometry (MS). KEY RESULTS AND CONCLUSIONS: Whereas the profiles of emitted compounds showed qualitative homogeneity, being mainly composed of methyl benzoate with quantitative variation, the profiles of endogenous compounds showed both qualitative and quantitative variation. A negative correlation was found between the evaporation ratio and boiling point of each compound examined. Lower boiling point compounds were strongly represented in the emitted component, resulting in the reduction of qualitative variation in floral scent. In conclusion, floral scent diversity results from variation in both the endogenous production and the evaporation rate of the individual volatile compounds.     

Asymmetric gene introgression in two closely related Orchis species: evidence from morphometric and genetic analyses

ABSTRACT: BACKGROUND: In food-deceptive orchids of the genera Anacamptis, Neotinea and Orchis floral isolation has been shown to be weak, whereas late-acting reproductive barriers are mostly strong, often restricting hybridization to the F1 generation. Only in a few species hybridization extends beyond the F1 generation, giving rise to hybrid swarms. However, little is known about the abundance of later-generation hybrids and what factors drive their occurrence in hybrid populations. In this study, molecular analyses were combined with detailed morphological measurements in a hybrid population of two closely related Orchis species (Orchis militaris and O. purpurea) to investigate the hypothesis that the abundance of later-generation hybrids is driven by changes in floral characters after hybridization that exert selective pressures that in turn affect hybridization. RESULTS: Both the molecular and morphological data point to extensive genetic and morphological homogenization and asymmetric introgression. Estimating genomic clines from the multi-locus genotype data and testing for deviation from neutrality revealed that 30 out of 113 (27%) AFLP markers significantly deviated from neutral expectations. Plants with large floral displays or plant with flowers that resembled more O. purpurea had higher female fitness than plants with small floral displays or plants with flowers resembling more O. militaris, suggesting that directional selection may have contributed to the observed patterns of introgression. CONCLUSIONS: These results indicate that in closely related orchid species hybridization and gene introgression may be partly driven by selection for floral traits of one of the parental types. However, because some pure individuals were still present in the studied population, the parental species appeared to be sufficiently isolated to survive the challenge of sympatry.     

Integrating floral scent, pollination ecology and population genetics

1 . Floral scent is a key factor in the attraction of pollinators. Despite this, the role of floral scent in angiosperm speciation and evolution remains poorly understood. Modern population genetic approaches when combined with pollination ecology can open new opportunities for studying the evolutionary role of floral scent.
2 . A framework of six hypotheses for the application of population genetic tools to questions about the evolutionary role of floral scent is presented. When floral volatile chemistry is linked to pollinator attraction we can analyse questions such as: Does floral volatile composition reflect plant species boundaries? Can floral scent facilitate or suppress hybridization between taxa? Can the attraction of different pollinators influence plant mating systems and pollen-mediated gene flow? How is population genetic structure indirectly influenced by floral scent variation?
3 . The application of molecular tools in sexually deceptive orchids has confirmed that volatile composition reflects species boundaries, revealed the role of shared floral odour in enabling hybridization, confirmed that the sexual attraction mediated by floral odour has implications for pollen flow and population genetic structure and provided examples of pollinator-mediated selection on floral scent variation. Interdisciplinary studies to explore links between floral volatile variation, ecology and population genetics are rare in other plant groups.
4 . Ideal study systems for future floral scent research that incorporate population genetics will include closely related taxa that are morphologically similar, sympatric and co-flowering as well as groups that display wide variation in pollination mechanisms and floral volatiles.     

Population Genetic Structure of a Sandstone Specialist and a Generalist Heath Species at Two Levels of Sandstone Patchiness across the Strait of Gibraltar

Many habitat specialist species are originally composed of small, discontinuous populations because their habitats are naturally fragmented or patchy. They may have suffered the long-term effects of natural patchiness. Mediterranean heathlands, a representative habitat in the Strait of Gibraltar region, are associated with nutrient-poor, acidic sandstone soils. Sandstone soil patches in the African side of the Strait (Tangier) are, in general, smaller and more scattered than in the European side (Algeciras). In this study, we analyze the effect of this sandstone patchiness on the population genetic diversity and structure of two Erica species from these Mediterranean heathlands that differ in their edaphic specificity, E. australis, sandstone specialist, and E. arborea, generalist. Average levels of within-population genetic diversity and gene flow between populations were significantly lower in Tangier (high sandstone patchiness) than in Algeciras (low patchiness) for the sandstone specialist, whereas no differences between both sides of the Strait were detected in the edaphic generalist. Since most endemic species in Mediterranean heathlands of the Strait of Gibraltar are sandstone specialists, these results highlight an increased vulnerability to loss of genetic diversity and local extinction of the heathland endemic flora in the Tangier side of the Strait of Gibraltar.     

Specialization to cold‐water upwellings may facilitate gene flow in seabirds: new evidence from the Peruvian pelican Pelecanus thagus (Pelecaniformes: Pelecanidae)

Recent research has shown that tropical seabirds specialized to feed on cold water upwellings exhibit low population genetic differentiation and high gene flow across large geographic distances. This pattern is opposite to the general pattern of differentiation reported for tropical seabirds, and led us to hypothesize that specialization to cold‐water upwellings facilitates gene flow between colonies. As a test of this hypothesis we characterized population differentiation and gene flow across the range of the Peruvian pelican Pelecanus thagus, an upwelling specialist endemic to the Humboldt Current, using an 838 base pair segment of the mitochondrial control region and seven microsatellite loci. In support of our hypothesis we report genetic panmixia across the geographic range of this species and inferred high gene flow between colonies. The high dispersal propensity of upwelling specialist seabirds (adults and/or juveniles) may reduce loss of genetic diversity during population declines, and increase the ability of these species to colonize new islands.     

Evidence of population bottleneck in Astragalus michauxii (Fabaceae), a narrow endemic of the southeastern United States

Genetic factors such as decreased genetic diversity and increased homozygosity can have detrimental effects on rare species, and may ultimately limit potential adaptation and exacerbate population declines. The Gulf and Atlantic Coastal Plain physiographic region has the second highest level of endemism in the continental USA, but habitat fragmentation and land use changes have resulted in catastrophic population declines for many species. Astragalus michauxii (Fabaceae) is an herbaceous plant endemic to the region that is considered vulnerable to extinction, with populations generally consisting of fewer than 20 individuals. We developed eight polymorphic microsatellites and genotyped 355 individuals from 24 populations. We characterized the population genetic diversity and structure, tested for evidence of past bottlenecks, and identified evidence of contemporary gene flow between populations. The mean ratios of the number of alleles to the allelic range (M ratio) across loci for A. michauxii populations were well below the threshold of 0.68 identified as indicative of a past genetic bottleneck. Genetic diversity estimates were similar across regions and populations, and comparable to other long-lived perennial species. Within-population genetic variation accounted for 92 % of the total genetic variation found in the species. Finally, there is evidence for contemporary gene flow among the populations in North Carolina. Although genetic factors can threaten rare species, maintaining habitats through prescribed burning, in concert with other interventions such as population augmentation or (re)introduction, are likely most critical to the long term survival of A. michauxii.     

The neighborhood matters: effects of neighbor number and sibling (or kin) competition on floral traits in Spergularia marina (Caryophyllaceae)

Abstract.— Effects of abiotic factors on the expression of floral and gender traits have been well documented in wild plant species; by contrast, little is known of the effect(s) on an individual's floral phenotype of the genetic composition of its neighboring conspecifics. Here we report the results of a greenhouse experiment conducted to detect the effects of genetic attributes of an individual's local environment on the expression of floral traits in the selfing annual, Spergularia marina (Caryophyllaceae). First, to test the hypothesis that negative effects of intraspecific competition are stronger when an individual competes with genetically similar individuals than when it competes with unrelated genotypes, we evaluated the effects of the number of nearest-neighbor kin (vs. unrelated individuals) on floral traits. Plants adjacent to two kin produced significantly fewer stamens per flower than plants adjacent to one or no siblings, indicating that kin competition reduced allocation to male function. Second, to test the hypothesis that the genetic diversity of a neighborhood influences the phenotype of a focal plant, we determined whether the number of maternal families represented among an individual's nearest neighbors influences its phenotype. The number of maternal families surrounding a focal plant did not affect floral trait expression. These results suggest that in S. marina , male function is more sensitive than female function to the genetic environment and that as an individual's genetic similarity to its neighbors increases, so do the negative effects of competition for limited resources.     

The genetic structure of a primate species: Rhesus macaques and other Cercopithecine monkeys

Among rhesus macaques (Macaca mulatta)and other cercopithecine monkeys, social groups occupying adjacent home ranges (i.e., members of the same local population) exchange individuals and genes and thus exhibit marked genetic similarities. To assess the degree to which this pattern extends beyond the local population, the genetic structure of M. mulattaand six other primate species was determined using Nei’s (1973) gene-diversity analysis. The genetic similarities seen among social groups in the Dunga Gali population of M. mulatta (Melnick et al.,1984a) can be seen over the entire species range. Comparison of these results with the structures of other similarly organized primate species indicates that (1) the average social group contains most of its local population’s genetic diversity, (2) the average local population contains the majority of the genetic diversity found in the region to which it belongs, and (3) the proportion of species gene diversity found in the average regional population varies substantially between species. Genetic homogeneity within local and regional populations is probably the product of gene flow. The application of a number of analytical models of selection and gene flow strongly suggests that gene flow, genetic drift, and zoogeography offer a more parsimonious and plausible explanation for interspecific variation in regional differentiation than does stabilizing selection.     

Widespread gene flow between oceans in a pelagic seabird species complex

Global‐scale gene flow is an important concern in conservation biology as it has the potential to either increase or decrease genetic diversity in species and populations. Although many studies focus on the gene flow between different populations of a single species, the potential for gene flow and introgression between species is understudied, particularly in seabirds. The only well‐studied example of a mixed‐species, hybridizing population of petrels exists on Round Island, in the Indian Ocean. Previous research assumed that Round Island represents a point of secondary contact between Atlantic (Pterodroma arminjoniana) and Pacific species (Pterodroma neglecta and Pterodroma heraldica). This study uses microsatellite genotyping and tracking data to address the possibility of between‐species hybridization occurring outside the Indian Ocean. Dispersal and gene flow spanning three oceans were demonstrated between the species in this complex. Analysis of migration rates estimated using bayesass revealed unidirectional movement of petrels from the Atlantic and Pacific into the Indian Ocean. Conversely, structure analysis revealed gene flow between species of the Atlantic and Pacific oceans, with potential three‐way hybrids occurring outside the Indian Ocean. Additionally, geolocation tracking of Round Island petrels revealed two individuals travelling to the Atlantic and Pacific. These results suggest that interspecific hybrids in Pterodroma petrels are more common than was previously assumed. This study is the first of its kind to investigate gene flow between populations of closely related Procellariiform species on a global scale, demonstrating the need for consideration of widespread migration and hybridization in the conservation of threatened seabirds.     

Genetic Evidence of the Contribution of Ethnic Migrations to the Propagation and Persistence of the Rare and Declining Scrambling Shrub Caesalpinia bonduc L

This paper examines the contribution of human migrations to the propagation and maintenance of Caesalpina bonduc by means of an analysis of its population genetics and distribution patterns. One hundred and forty seven sites were surveyed in the three climatic zones of Benin and all individuals of the species were recorded. A set of individuals was randomly selected and sampled from seven populations and morphological variation and genetic diversity were assessed. The study confirmed the presence of the species in all climatic zones but its abundance varied greatly. Morphological variability between populations and zones was low in comparison with the high amount of variation within populations. AFLP and cpDNA fingerprinting revealed an extremely low genetic diversity within populations and a low genetic differentiation, suggesting parental links between populations. The results support the hypothesis of human involvement in Caesalpinia dispersal and persistence in Benin. However, the low genetic diversity may imply high risks for future extinction. We recommend that gene flow among the remaining populations be supported in order to conserve the species.