Viola tricolor (Violaceae) is a karyologically unstable species

Viola tricolor is a pseudometallophyte covering heavy-metal-polluted and non-polluted areas. The species is a member of the evolutionarily young sect. Melanium of Viola. In this study, we sought to determine whether the karyotype of V. tricolor is stable with respect to chromosome structure or is altered depending on environmental conditions (heavy-metal-polluted vs. non-polluted areas). We established the karyotypes of plant material originating from a Zakopane meadow (non-metallicolous population) and from the Bukowno mine waste heap (metallicolous population), showing evident interpopulation differentiation in chromosome type (2M+20 m+2sm+2st vs. 18 m+8sm), in the number, size, and distribution of rDNA loci (25S and 5S), and also in chromosome mutations, mainly fission of chromosomes into acentric fragments and translocation of the fragments. Variable numbers of both 25S and 5S rDNA loci were distributed at different positions of the chromosomes and not on specific pairs of chromosomes. The results clearly indicate that the karyotype of V. tricolor results from the unstable genetic structure of the species. This character, typical for relatively young evolutionary groups, proves its membership to the Melanium section considered to be young within the genus Viola.     

Patterns of flower morphology and structural changes during interconversion between chasmogamous and cleistogamous flowers in Viola philippica北大核心CSCD

Aims: Viola philippica is a species with a typical chasmogamous-cleistogamous (CH-CL) mixed breeding system. It provides a flower model system to investigate floral organs development under different photoperiods. Morphological changes of intermediate cleistogamous (inCL) flowers have been observed, the trends in variation of changes from CH flowers to CL flowers or from CL flowers to CH flowers have been analyzed, the localized effects of poorly developed stamens and petals in CL and inCL flowers have been identified. This research provided morphology and structural changes with implication for the evolutionary significance of the dimorphic flower formation for further study in dimorphic flower development. Methods: We used methods of anatomy and structural analysis to observe the morphological structures of flowers under different photoperiods. Important findings: Photoperiod played an important role in the development of CH and CL flowers in V. philippica. Under short-day light and intermediate-day light, both CH and inCL flowers developed simultaneously. Most of the floral buds were CH flowers under a photoperiod of short-day light, but most of the floral buds were inCL flowers under mid-day light. Complete CL flowers formed under long-day lights. However, there were a series of transitional types in the number and morphology of stamens and petals among inCL flowers, including five stamens with three petals related to CH flowers and two stamens with one petal related to CL flowers. The former type was dominant under short-day light conditions, and the latter type was dominant under mid-day light. Further more, there were localized effects in stamen and petal development for CL and inCL flowers. The development of ventral lower petal (corresponding to the lower petal with spur of CH flower) and the adjacent two stamens in inCL flowers were best, and the back petal was similar to that of CL flowers, an organ primordium structure. The adjacent stamens with the back petals tended to be poorly developed. In extreme cases, these stamens in inCL flowers had no pollen sac, only a membranous appendage or even a primordium structure. When the plants with CL or CH flowers were placed under short-day light or long-day light, the newly induced flowers all showed a series of inCL flower types, finally the CL flowers transformed into CH flowers, and the CH flowers transformed into CL flowers. This result indicates the gradual effects of different photoperiods on dimorphic flowers development of V. philippica. A long photoperiod could inhibit the development of partial stamens and petals, and a short photoperiod could prevent the suppression of long-day light and promote the development of stamens and petals.     

堇菜属组间的系统发育与亲缘关系：基于trnL-trnF、psbA trnH、rpL16、ITS序列，细胞学以及形态学证据

以鼠鞭草(Hybanthus enneaspermus)、鳞隔堇(Scyphellandra pierrei)、雷诺木(Rinorea bengalensis)作为外类群,对堇菜属(Viola)20个类群的trnL trnF序列,17个类群的psbA trnH、rpL16序列以及1个类群的nrDNA ITS序列进行了测定,并从GenBank下载相应的序列,运用最大简约法以及贝叶斯推论法进行系统分析,构建系统发育树。结果表明：堇菜亚属(subgen.Viola)不是一个单系类群,并明确了堇菜属部分组间类群的亲缘关系。本文还结合形态与细胞学证据对堇菜属进行性状演化的推测。结果表明：1）直立茎较匍匐茎、莲座状茎（叶基生）原始;2）托叶边缘长流苏状与托叶1/2~3/4合生分别是鸟嘴柱头堇菜组（sect.Trigonocarpae）和合生托叶组（sect.Adnatae）演化路线的重要性状标志;3）花柱样式从柱头无喙演化至柱头有喙,并由柱头简单演化至柱头复杂,再趋向于柱头简化。     

Fitness and genetic variation of Viola calaminaria, an endemic metallophyte: implications of population structure and history

We investigated variations in genetic diversity and plant fitness in a rare endemic metallophyte of calamine soils, Viola calaminaria, in relation to population size, population connectivity and population history in order to evaluate and discuss potential conservation strategies for the species. Mean population genetic diversity (H(s) = 0.25) of V. calaminaria was similar to endemic non-metallophyte taxa. Twenty-one per cent of the genetic variation was partitioned among populations and a low (9%) but significant differentiation was found among geographical regions. Our results did not support the hypothesis that the acquisition of metal tolerance may result in reduced genetic diversity, and suggested that strict metallophytes do not exhibit higher inter-population differentiation resulting from scattered habitats. There were no relationships between population genetic diversity and population size. Significant correlations were found between plant fitness and (i) population size and (ii) connectivity index. Recently-founded populations exhibited the same level of genetic diversity as ancient populations and also possessed higher plant fitness. There was no indication of strong founder effects in recently-established populations. The results suggest that the creation of habitats through human activities could provide new opportunities for conservation of this species.     

Flavonoids and other compounds from the aerial parts of Viola etrusca

The non-volatile constituents of the rare species Viola etrusca Erben (Violaceae), collected at Mount Amiata, Italy, were phytochemically investigated for the first time. Two new flavonoid glycosides, 4'-methoxyrhamnetin (1) and violetruscoside (2), an isorhamnetin derivative, were isolated from the flowering aerial parts, together with eleven known substances, including eight flavonoids, a phenolic acid, glycerin, and a coumarin derivative. The NMR data of violanthin (10) and isoviolanthin (11) are reported for the first time.     

Ant-seed interactions: combined effects of ant and plant species on seed removal patterns

Seed dispersal by ants (i.e. myrmecochory) is usually considered as a mutualism: ants feed on nutritive bodies, called elaiosomes, before rejecting and dispersing seeds in their nest surroundings. While mechanisms of plant dispersal in the field are well documented, the behaviour of the ant partner was rarely investigated in details. Here, we compared in laboratory conditions the foraging behaviour of two ant species, the omnivorous Lasius niger and the insectivorous Myrmica rubra to which seeds of two European myrmecochorous plants (Chelidonium majus and Viola odorata) were given. Ant colonies were simultaneously presented three types of items: entire seeds with elaiosome (SE), seeds without elaiosome (S) and detached elaiosomes (E). The presence of elaiosomes on seeds did not attract workers from a distance since ants first contact equally each type of items. Although ants are mass-recruiting species, we never observed any recruitment nor trail-laying behaviour towards seeds. For ants having contacted seed items, their antennation, manipulation and seed retrieval behaviour strongly varied depending on the species of each partner. Antennation behaviour, followed by a loss of contact, was the most frequent ant-seed interaction and can be considered as a “hesitation” clue. For both plant species, insectivorous Myrmica ants removed items in larger number and at higher speed than Lasius. This fits with the hypothesis of a convergence between odours of elaiosomes and insect preys. For both ant species, the small Chelidonium seeds were retrieved in higher proportion than Viola ones, confirming the hypothesis that ants prefer the higher elaiosome/diaspore-ratio. Thus, in these crossed experiments, the ant-plant pair Myrmica/Chelidonium was the most effective as ants removed quickly almost all items after a few antennations. The presence of an elaiosome body increased the seed removal by ants excepting for Myrmica which retrieved all Chelidonium seeds, even those deprived of their elaiosome. After 24 h, all the retrieved seeds were rejected out of the nest to the refuse piles. In at least half of these rejected items, the elaiosome was discarded by ants. Species-specific patterns and behavioural differences in the dynamics of myrmecochory are discussed at the light of ant ecology. Received 10 September 2007; revised 5 February 2008; accepted 5 March 2008.     

Genetic effects of habitat fragmentation in Viola pubescens (Violaceae), a perennial herb with chasmogamous and cleistogamous flowers

The reproductive biology of a plant species is important in the response of populations to habitat fragmentation, especially if plant-pollinator interactions are disrupted. The genetic effects of forest fragmentation were examined in the common understorey herb Viola pubescens, a species that produces self-pollinated cleistogamous (CL) flowers and potentially outcrossing chasmogamous (CH) flowers. Using allozymes, we measured genetic variation in different sized populations. These were located in woodlots of various sizes (0.5-40.5 ha) and distances from one another (0.3-46 km) within the agricultural landscape of central Ohio in the Midwestern United States. Changes in forest cover of each woodlot within the past 180 years were determined from historical sources and aerial photographs. Woodlot and population sizes were significantly and positively correlated with measures of genetic variation (A, P, HO and HE), with variation highest in populations in the largest woodlot population and lowest in the smallest woodlot population. Most large woodlots resulted from fluctuations in forest cover over the past 60 years, while smaller fragments remained the same size. Overall, populations in Crawford County were genetically differentiated from one another (theta = 0.34), but there was no relationship between genetic and geographical distance. Preliminary evidence for a single year indicated a high rate of outcrossing in most populations. Despite the CH/CL reproductive advantage and apparent outcrossing, populations of V. pubescens in small woodlots remain susceptible to potentially detrimental effects of fragmentation such as genetic drift and reduced levels of genetic variation.     

地丁化学成分的研究

从紫花地丁中首次分得四个有机酸,一个酰胺和一个黄酮甙,其中二十四酰对羟基苯乙胺为一新化合物。