Analysis of allozyme variability in three Plantago species and a comparison to morphological variability

Summary The level of electrophoretic variability in three Plantago species, P. major, P. coronopus, and P. lanceolata, was analyzed in relation to their breeding systems and compared with their morphological variability. From each species several populations were analyzed. The outcrossing P. lanceolata had the highest level of electrophoretic variability and the lowest population differentiation. The inbreeding P. major showed the opposite: a low level of electrophoretic variability and a high population differentiation. P. coronopus, with an intermediate breeding system, had an intermediate level of variability and differentiation. In comparing the species, it appeared that P. coronopus and P. major showed good concordance in the distribution of both kinds of variability, each having only a slightly higher morphological than electrophoretic differentiation between populations. P. lanceolata showed a higher morphological than electrophoretic differentiation between populations. A comparison of populations, within species, revealed good concordance of electrophoretic and morphological variability only within P. coronopus, while some populations of the other two species had relatively lower morphological variability compared with electrophoretic variability.Grassland Species Research Group Publication No. 182     

Geographic structure of chloroplast DNA polymorphisms in European oaks

Chloroplast DNA polymorphisms have been detected by the conventional Southern-blotting hybridization method in four species of European oaks (Quercus petraea, Q. robur, Q. pubescens and Q. pyrenaica). Three polymorphisms, shared by at least three of these species, can be scored directly in ethidium bromidestained gels and were used in a broad survey of the level of differentiation of the oak species and of their pattern of genetic structure in western Europe. The highly significant geographic variation and the high genetic differentiation (Gst=0.895, S_Gst=0.025) indicate a low level of cytoplasmic gene flow. We conclude that cytoplasmic genomes are well suited for the reconstruction of past migrational routes of such a complex of species.     

Comparative investigations on the differentiation of the endodermis and the development of the Hartig net in mycorrhizae of Picea abies and Larix decidua

Summary The differentiation of the endodermis of mycorrhizal roots of Picea abies and Larix decidua was investigated by means of light and transmission electron microscopy and with fluorescence techniques. The initiation and differentiation of the Hartig net were recorded. Differences between the two tree species were found, as were differences between the two tree species and angiosperms. The Casparian band developed immediately after the origin of endodermal cells from the meristem in mycorrhizae of both tree species. In L. decidua only the primary endodermis was present in most mycorrhizal laterals. The secondary structure of the endodermis was restricted to main roots and proximal parts of larch mycorrhizae. In P. abies mycorrhizae, however, the secondary stage of the endodermis developed soon after the primary endodermis and was characterized by regular alternation of short, active passage cells and elongated, rapidly degenerating cells, the inner surface of which was covered by a thick suberin layer. Hartig net development started in P. abies short roots only after the differentiation of endodermis into the secondary stage, whereas in L. decidua, the Hartig net was already initiated at the primary endodermal stage. Differences were specific for tree species.     

Genetic variation and putative hybridization inSalix alba andS. fragilis (Salicaceae): Evidence from allozyme data

Genetic variability was estimated by enzyme electrophoresis in 239 Belgian clones from theSalix alba-S. fragilis complex. This morphological complex suggested a high frequency of hybrids. To test this hypothesis, the clones were pooled as a single co-adapted species complex and secondly as belonging to either species, i.e. beingS. alba-like orS. fragilis-like. The standard genetic variability measures showed higher values for the complex than for the separate species. However, the observed mean heterozygosity was lower in the putative hybrid complex than for each of the species separately. The fixation indices were more variable at the species level and indicated that mostS. fragilis locations appeared fixed forlap-1, whereas no fixation occured inS. alba locations. Averaged at the regional (i.e. catchment) level, this difference between the two species remained and values ranged from 0.457 to 0.617 inS. alba and were much higher, fixed homozygous or monomorph inS. fragilis. Hierarchical F-statistics revealed that most of the differentiation occured at the lower levels of localities and tributaries and that there was no further differentiation between catchments. Tributaries which are 10–25km in length were proposed as the most likely entities for further examination of putative hybridization and events of allelic fixations. By considering the two abovementioned approaches of data input, it could be suggested that most of the allozyme differentiation was between the species and less between the regions.     

Assessment of genetic diversity of native species in Izu Islands for a discriminate choice of source populations: Implications for revegetation of volcanically devastated sites

In using native species for revegetation, it is necessary choose source populations carefully to reduce the risk of planting suboptimal germplasm. To make preliminary recommendations for native species to use in the revegetation of a volcanically devastated area on Miyake Is., Japan, we investigated the genetic variation of Alnus sieboldiana, Miscanthus sinensis ssp. condensatus, and Polygonum cuspidatum var. terminalis in the Izu Islands and on the Izu Peninsula based on chloroplast DNA (cpDNA) sequence variations and amplified fragment length polymorphisms (AFLPs). The amount and pattern of differentiation differ between organelle and nuclear markers, suggesting the necessity of evaluation based on both types of markers. Within-population diversity did not vary among populations, suggesting that it does not need to be considered in the choice of a source population. The pattern and degree of differentiation varied among species, and geographical proximity did not necessarily accord with genetic similarity, suggesting that the site of an appropriate source population varies among species and should be determined empirically rather than by assuming that close proximity predicts genetic similarity. The Izu Peninsula populations deviated from the island populations in all species. Comparison of cpDNA sequences with those of related species indicates the possibility of hybridization with related species on the Izu Peninsula, suggesting that seeds collected from populations where related species live sympatrically should not be used for revegetation. These findings indicate the need to assess the genetic diversity empirically by using organelle and nuclear markers to avoid unintended consequences of genetic mixing associated with revegetation.     

Low genetic differentiation betweenAdiantum capillusveneris L. andA. ogasawarense Tagawa (Adiantaceae), an endemic pteriodophyte of the bonin (ogasawara) islands

Genetic differentiation was examined betweenAdiantum capillus-veneris L. andA. ogasawarense Tagawa. A total of 136 individuals from two populations ofA. ogasawarense and three populations ofA. capillus-veneris were sampled. Allozymes encoded by 19 putative loci for nine enzyme systems were observed. The populations ofA. ogasawarense are genetically differentiated from those ofA. capillus-veneris; conspecific populations cluster together. However, genetic identity between two species was estimated to be 0.815, and indicates that the degree of allozyme differentiation is lower than those between endemic flowering plants and their progenitors. It is possible that the low genetic differentiation observed betweenA. ogasawarense andA. capillus-veneris results from a recent origin of the endemic species,A. ogasawarense.     

中甸灯台报春与鹅黄灯台报春的系统演化

中甸灯台报春和鹅黄灯台报春在形态上较为相似,通常被认为是亲缘关系较近的物种。该研究选取核基因ITS序列和叶绿体trn L-F为分子标记,利用贝叶斯的方法构建系统树,在用两种分子标记构建的系统树中,两种报春均以0.81的支持率聚成一个分支,明确了两种报春的姐妹种关系。首先,通过选取两个物种的五个形态学性状,进行主成分分析,聚类结果中两种报春各自的个体分别聚在两块区域,表明两种报春的形态学性状产生了明显的分化,且中甸灯台报春的花部各性状值明显大于鹅黄灯台报春,表明花部综合征和繁育系统间的相关联系。然后,通过用8对SSR分子标记对两种报春进行STRUCTURE聚类分析,结果检测K的最适值为2,此时中甸灯台报春和鹅黄灯台报春的个体各自以不同颜色聚成界限清晰的两块区域,揭示了两种报春在分子水平上也产生了显著而稳定的分化,通过Ima2软件,依据叶绿体联合序列,计算了两种报春的分化时间大约是在更新世,推测这两个姐妹种的物种分化受更新世气候动荡和一些地质历史事件的影响。最后,运用maxent软件分析两个物种的生态位差异,结果表明最干季节降水量、年均降水量和季节性降水量对中甸灯台报春的分布有重要影响,最冷季节平均温度、最干月降水量、年均降水量和季节性降水量对鹅黄灯台报春的分布有重要影响,两个物种间的生态位产生了分化。由此推测,这种生态位的差异是物种分化的结果,同时也是物种间系统演化的重要驱动力。     

Phylogeny,Species Richness,and Ecological Specialization in Cyperaceae Tribe Cariceae

Cyperaceae tribe Cariceae is characterized by both species richness and habitat diversity, making it an ideal system to study ecological specialization and niche differentiation. We present a phylogenetic hypothesis for the tribe based on nuclear and chloroplast DNA sequence comparisons (ETS-1f, ITS, trnL intron, trnL-trnF intergenic spacer) for 140 representative species from five continents, and use this hypothesis to suggest patterns of both niche conservatism and niche differentiation, particularly within the large subgenus Carex. We identify a new major clade, comprising forest species of East Asian Carex section Siderostictae (subgenus Carex) as sister to the rest of tribe Cariceae. Within Carex subgenus Carex, species tolerant of water-saturated habitats occur in only a few, apparently derived groups, with varying species richness. Clades of predominantly wetland species tend to have broad geographic distribution, often with sister species on different continents, suggesting recent dispersal. In contrast, species within several clades are predominantly forest specialists with distinct Asian and North American lineages. Niche segregation along environmental gradients, such as soil moisture or acidity, is quite common among closely related wetland species, but more difficult to demonstrate within upland forest groups. More complete sampling of species within both wetland and forest groups, combined with comparable sampling of environmental preferences and testing against null models, will be needed for more rigorous exploration of the observed patterns.     

Relationships among species inCarex sect.Phyllostachys (Cyperaceae) based on allozyme divergence

Allozyme variation was examined inCarex sect.Phyllostachys (Cyperaceae) to provide insight into phylogenetic relationships hypothesized in an earlier study and to determine the degree of genetic differentiation within and between taxa. Genetic identity values are concordant with the morphological differences found between species. The lowest values are found between species with the greatest morphological dissimilarity. Conversely, the highest values are associated with species pairs distinguished by relatively few morphological differences. Conspecific populations possess high genetic identities, although interpopulation differentiation has characterized the evolutionary history of some species. Geographic patterning is also evident within species, with geographically proximate populations often having the highest identity values. Phylogenetic trees produced using different cladistic methods were poorly supported and varied in their depiction of relationships among species. One cladogram produced using presence/absence allelic data is more or less congruent with a topology recovered from an earlier analysis utilizing molecular and morphological data. The wide- and narrow-scaled clades are maintained as are the sister species pairsC. backii/C. saximontana, C. basiantha/C. superata, andC. jamesii/C. juniperorum. Contrary to the finding of our previous study, however,C. willdenowii is aligned withC. jamesii/C. juniperorum.     

Patterns of genetic differentiation in two annual bromegrasses,Bromus lanceolatus andB. hordeaceus (Poaceae)

Infraspecific genetic differentiation was analysed in two tetraploid annual bromegrasses,Bromus lanceolatus (from N Africa) andB. hordeaceus (from N Africa and France). Genetic analysis of populations was based on allozyme polymorphisms at 17 loci. Different fixed heterozygous phenotypes were scored in both species, according to their allopolyploid origin. In N Africa, more variation occurred among populations ofB. lanceolatus than ofB. hordeaceus. The variation was not randomly distributed among populations of both species. InB. lanceolatus, differentiation was correlated with climatic variables rather than with geographic distance between populations. Higher correlation of genetic differentiation with geographic distance occurred inB. hordeaceus, particularly at large geographic scale, between French and N African populations. Within each region, the populations appeared weakly genetically differentiated, even when belonging to different subspecies.     

A requirement for <Emphasis Type="Italic">kit</Emphasis> in embryonic zebrafish melanocyte differentiation is revealed by melanoblast delay

Exploring differences in gene requirements between species can allow us to delineate basic developmental mechanisms, provide insight into patterns of evolution, and explain heterochronic differences in developmental processes. One example of differences in gene requirements between zebrafish and mammals is the requirement of the kit receptor tyrosine kinase in melanocyte development. kit is required for migration, survival and differentiation of all neural crest-derived melanocytes in mammals. In contrast, zebrafish kit is not required for differentiation of embryonic melanocytes during normal development. When melanoblast development in zebrafish embryos is delayed by injecting morpholinos targeted to the mitfa gene, we show that these delayed melanoblasts fail to differentiate in kit mutants. Thus, we show that there is a kit requirement for melanocyte differentiation in zebrafish when melanoblast development is delayed. Furthermore, we show that kit is not involved in maintaining melanocyte precursors through the developmental delay, but instead is required for differentiation of melanocytes after the block on their development is removed. Finally, we suggest there is a heterochronic shift in the onset of melanocyte differentiation between fish and mouse, and developmental delay of melanoblast development in zebrafish removes this heterochronic difference.Edited by D. Tautz     

Differences in allozyme patterns between Diaphanosoma brachyurum and Diaphanosoma mongolianum,as revealed in Central European populations

Recent taxonomic revisions in the genus Diaphanosoma have made the uncertainty in species discrimination with morphological characters obvious. Therefore species characterization on a genetic basis seems to be required.Here we examined the genetic structure of two Diaphanosoma mongolianum populations and three Diaphanosoma brachyurum populations in Central Europe by allozyme electrophoresis. A genetic differentiation between both species was evident. 5 out of 9 tested loci carried diagnostic alleles. Both species differed in their habitat choice: D. mongolianum was adapted to higher trophic levels than D. brachyurum. Co-occurrence was observed in a eutrophic lake. Populations sampled from their preferred habitats showed high genotype diversities.Most genotype frequency distributions were in agreement with Hardy-Weinberg expectations and temporal (between years) changes in genotypic compositions were not common. This indicated annually occurring bouts of sexual reproduction, similar to intermittent Daphnia populations. Genetic differentiation among lakes suggested restricted gene flow.     

Relationships between five species ofLolium (Poaceae)

Morphological analysis and electrophoresis of seed proteins of fiveLolium species disclosed that they form two distinct groups corresponding to those recognized from compatibility data.Lolium temulentum andL. remotum of the self-pollinated group were shown to be distinct but closely related species. Morphological intergradation and high similarities between protein profiles ofL. perenne, L. multiflorum andL. rigidum (cross-pollinated species) suggest little genetic differentiation between these taxa. This implies that treatment at the infraspecific level might better accomodate the data.     

Ruellia sect.Urceolata (Acanthaceae), a novel species complex from southern Mexico

A new section in MexicanRuellia, R. sect.Urceolata comprising three species (includingR. cedilloi, spec. nova), endemic to Mexico, is described and illustrated. The taxonomic relationship and differentiation of the species are discussed. Evolution in Mexican Ruellas seems to be occurring at the diploid level.     

Polymorphism in Oerstedia dorsalis (Abilgaard, 1806) revisited

Genetic distance, estimated from electrophoretic variation of six enzyme loci, between three groups of Oerstedia dorsalis specimens which differ in their external morphology shows that one of the varieties should be assigned the rank of species. The genetic differentiation is compared with a multivariate assessment of morphological distance between these forms, and it is concluded that the substantial genetic differentiation between the two species is not reflected in morphological divergence.     

Genetic analysis of morphological variability in three Plantago species with different mating systems

Summary Morphological variability in three Plantago species possessing different mating systems — P. Major, P. coronopus, and P. lanceolata — was analyzed. From each species several populations were analyzed. In comparing the species, it appeared that both the inbreeding P. major and the outbreeding P. lanceolata showed a high degree of morphological differentiation between populations. It was hypothesized that the absence of population differentiation for the species with a mixed mating system, P. coronopus, was caused by high adaptive plasticity. Plasticity is probably the predominant mechanism by which this species copes with different environments. There were considerable differences between populations within each species for their levels of variability and their heritabilities. It appeared that besides the influence of the mating system, selection may diminish morphological variability in the case of strong directional selection, especially in P. major and P. lanceolata.Grassland Species Research Group Publication No. 135     

Studies on theStellaria longipes complex (Caryophyllaceae): Isozyme variability and the relationship betweenStellaria longipes andS. longifolia

Genetic variation within and the relationship betweenStellaria longipes Goldie andS. longifolia Muhl. were studied. Ten enzyme systems were assessed in eight natural populations ofS. longipes (25 loci) and three ofS. longifolia (20 loci) using starch and polyacrylamide gel electrophoresis. Patterns of population differentiation corresponded to geographic distance. There was no evidence that polyploidS. longipes had greater electrophoretic variability than diploidS. longipes. The isozyme data confirmed extensive population differentiation in these species and, within that context, a relatively close relationship betweenS. longipes andS. longifolia. It was postulated that diploids of these two species might be the progenitors of tetraploidS. longipes.     

Population and species variation of minisatellite DNA in Plantago

Three Plantago species were surveyed for within- and between-population variation at DNA sequences detected with the M13 minisatellite probe. The levels and patterns of variation detected by this probe correspond to those expected from the mating systems of the species. The highly-selfing species P. major has a relatively low variability of minisatellite sequences within populations and considerable differentiation between populations. The outcrossing species P. lanceolata exhibits higher minisatellite variability within populations and moderate differentiation between populations. P. coronopus, with a mixed mating system, has levels of variation intermediate between P. major and P. lanceolata. The levels of variation within and between populations corresponds, in general, to the levels of allozyme variation determined in an earlier study. Mating system and population structure appear to have a major influence on M13-detected fragment variation.     

Concordant clines and significant correlation between floral and pollen characters in Asarum heterotropoides var. heterotropoides (Aristolochiaceae)

To examine geographic differentiation in Asarum heterotropoides var. heterotropoides in Hokkaido Is. in the northern Japan, in which two putative cryptic species have been suspected to exist, extensive and detailed morphological research on 794 individuals from 44 populations throughout Hokkaido Is. was performed. Among the characters examined, the angle between and tip shape of the calyx lobes and the supratecta of the pollen grains were significantly correlated and were found in similar geographic clines. Among them, the pollen showed two discrete states in almost distinct distribution. Multidimensional scaling analysis showed that individuals within each of the two pollen types had different trends in flower characters. Consequently, we assumed a cline from south to north on Hokkaido Is. For the causes of the cline, the two hypotheses were proposed, primary geographic differentiation or extensive introgressive hybridization between two distinct geographical species existing in the past.     

西南地区6种魔芋属植物基于cpDNA序列的遗传多样性研究

研究野生作物资源的遗传变异及分化机制对种质资源的收集与改良具有重要意义。魔芋是我国西南地区的特色经济作物,但由于受到人为活动干扰,野生种群不断衰退。为评估西南地区魔芋属(Amorphophallus)野生群体的遗传多样性,探究代表性物种的系统发育地位,该研究利用3个叶绿体DNA(cpDNA)片段,分析了魔芋6个物种的遗传多样性,重建了种间系统发育关系。结果表明:(1)西南地区野生魔芋群体的遗传多样性普遍较低,虽然单倍型多样性(H_d)均值为0.428,但近一半群体只有1个单倍型,6个物种整体水平上的单倍型多样性在0.704到0.983之间。(2)在6个物种间检测到高水平的遗传分化,遗传分化系数(F_ST)值在0.481到0.967之间。(3)系统发育分析表明,选取的27个魔芋种主要聚成3个分支:非洲分支、东南亚分支和东亚大陆分支。疣柄魔芋(A. paeoniifolius)隶属于东南亚分支,而东亚大陆分支A包含花魔芋(A. konjac)和西盟魔芋(A. krausei),东亚大陆分支B由东亚魔芋(A. kiusianus)、滇魔芋(A. yunnanensis)和东京魔芋(A. tonkinensis)构成。生境隔离与人为干扰造成了西南地区野生魔芋群体较低的遗传多样性,魔芋属东亚大陆分支的分化可能与早期的快速扩张和生态适应有关。该研究为西南地区魔芋资源的合理保护、可持续利用和杂交育种提供了参考资料。