Morphological and Genomic Characterization of Filobasidiella depauperata: A Homothallic Sibling Species of the Pathogenic Cryptococcus Species Complex

The fungal species Cryptococcus neoformans and Cryptococcus gattii cause respiratory and neurological disease in animals and humans following inhalation of basidiospores or desiccated yeast cells from the environment. Sexual reproduction in C. neoformans and C. gattii is controlled by a bipolar system in which a single mating type locus (MAT) specifies compatibility. These two species are dimorphic, growing as yeast in the asexual stage, and producing hyphae, basidia, and basidiospores during the sexual stage. In contrast, Filobasidiella depauperata, one of the closest related species, grows exclusively as hyphae and it is found in association with decaying insects. Examination of two available strains of F. depauperata showed that the life cycle of this fungal species shares features associated with the unisexual or same-sex mating cycle in C. neoformans. Therefore, F. depauperata may represent a homothallic and possibly an obligately sexual fungal species. RAPD genotyping of 39 randomly isolated progeny from isolate CBS7855 revealed a new genotype pattern in one of the isolated basidiospores progeny, therefore suggesting that the homothallic cycle in F. depauperata could lead to the emergence of new genotypes. Phylogenetic analyses of genes linked to MAT in C. neoformans indicated that two of these genes in F. depauperata, MYO2 and STE20, appear to form a monophyletic clade with the MAT a alleles of C. neoformans and C. gattii, and thus these genes may have been recruited to the MAT locus before F. depauperata diverged. Furthermore, the ancestral MAT a locus may have undergone accelerated evolution prior to the divergence of the pathogenic Cryptococcus species since several of the genes linked to the MAT a locus appear to have a higher number of changes and substitutions than their MATα counterparts. Synteny analyses between C. neoformans and F. depauperata showed that genomic regions on other chromosomes displayed conserved gene order. In contrast, the genes linked to the MAT locus of C. neoformans showed a higher number of chromosomal translocations in the genome of F. depauperata. We therefore propose that chromosomal rearrangements appear to be a major force driving speciation and sexual divergence in these closely related pathogenic and saprobic species.     

Essential oil constituents and RAPD markers to establish species relationship in Cymbopogon Spreng. (Poaceae)

Nineteen Cymbopogon taxa belonging to 11 species, two varieties, one hybrid taxon and four unidentified species were analysed for their essential oil constituents and RAPD profiles to determine the extent of genetic similarity and thereby the phylogenetic relationships among them. Remarkable variation was observed in the essential oil yield ranging from 0.3% in Cymbopogon travancorensis Bor. to 1.2% in Cymbopogon martinii (Roxb.) Wats var. motia. Citral, a major essential oil constituent, was employed as the base marker for chemotypic clustering. Based on genetic analysis, elevation of Cymbopogon flexuosus var. microstachys (Hook. F.) Soenarko to species status and separate species status for C. travancorensis Bor., which has been merged under C. flexuosus (Steud.) Wats were suggested towards resolving some of the taxonomic complexes in Cymbopogon. The separate species status for the earlier proposed varieties of C. martinii (motia and sofia) is further substantiated by these analyses. The unidentified species of Cymbopogon have been observed as intermediate forms in the development of new taxa.     

Genetic diversity in Passiflora species determined by morphological and molecular characteristics

Morphological and molecular characteristics were studied in six wild species of Passiflora. There were statistically significant differences among these six species for all characteristics studied. Intra-specific variability was observed for number of flowers, number of fruits, number of seeds, fruit length, fruit width and leaf area. Cluster analysis using morphological data showed three groups: 1) P. palmeri var. sublanceolata, P. morifolia and P. foetida var. foetida, 2) P. coriacea and P. micropetala, and 3) P. suberosa. The dendrogram constructed using randomly amplified polymorphic DNA (RAPD) data showed six different groups for each species. The genetic distances among the 24 accessions ranged from 0.05 (between P. morifolia accessions P1 and P3) to 0.95 (P. coriacea accession 31 and P. palmeri var. sublanceolata accession 49). The species showed high morphological and molecular inter- and intraspecific variability.     

Natural hybrids in Chamaecrista sect. Absus subsect. Baseophyllum (Leguminosae-Caesalpinioideae): genetic and morphological evidence

Summary Chamaecrista sect. Absus subsect. Baseophyllum (Leguminosae–Caesalpinioideae) includes eight species with geographic distribution concentrated in the Cadeia do Espinha?o mountain range of the States of Bahia and Minas Gerais, in eastern Brazil. During the taxonomic revision of this group, individuals were encountered with intermediate morphology between three sympatric species. Allozyme and multivariate morphometric analyses were carried out to investigate the occurrence of hybridization between these species in four populations and 14 suspected hybrid individuals between C. confertiformis and C. depauperata and between C. blanchetii and C. confertiformis. The results of both analyses support the occurrence of natural hybridization between them, and that all the individuals with intermediate morphology are probably F1 hybrids. The hybrids are formally described as C. × blanchetiformis and C. ×patyensis.     

Evaluation of genetic diversity among Iranian accessions of Ocimum spp. using AFLP markers

Amplified fragment length polymorphism (AFLP) markers were used to assess the genetic, diversity of 120 Ocimum accessions belonging to five species and varieties named: Ocimum ciliatum, Ocimum minimum, Ocimum basilicum var. purpurascens, O. basilicum var. dianatnejadii and O. basilicum var. alba. Eight AFLP primer combinations revealed 150 polymorphic bands (59.5%). The highest and the lowest PIC were 0.87 and 0.81 for E-CAA/M-ACC and E-CAA/M-AGA primer combinations, respectively, with average polymorphic information content (PIC) value of 0.84 over all primer combinations. Cluster analysis based on unweighted pair group method with arithmetic Average (UPGMA) and Jaccard’s coefficient grouped the five species and varieties into two main clusters. The first cluster contained the accessions belonging to O. ciliatum and the second comprised different botanical varieties of O. basilicum and O. minimum. The means of Shannon’s diversity index and Nei’s index of genetic diversity indicated that O. basilicum had the greatest variation, while O. ciliatum showed the least variation. Nei’s genetic identity measured in five Ocimum species and botanical varieties revealed the highest identity (0.939) between O. minimum and O. basilicum var. purpurascens and the lowest genetic identity (0.611) between O. basilicum var. purpurascens and O. ciliatum. In conclusion AFLP results indicated that O. minimum should be considered as a variety of O. basilicum.     

Incipient radiation within the dominant Hawaiian tree Metrosideros polymorpha

Although trees comprise a primary component of terrestrial species richness, the drivers and temporal scale of divergence in trees remain poorly understood. We examined the landscape-dominant tree, Metrosideros polymorpha, for variation at nine microsatellite loci across 23 populations on young Hawai''i Island, sampling each of the island''s five varieties throughout its full geographic range. For four varieties, principal coordinate analysis revealed strong clustering of populations by variety across the 10 430 km² island, indicating partitioning of the species into multiple evolutionarily significant units. The single island-endemic form, riparian var. newellii, showed especially strong differentiation from other varieties despite occurring in sympatry with other varieties and likely evolved from a bog form on the oldest volcano, Kohala, within the past 500 000 years. Along with comparable riparian forms on other Pacific Islands, var. newellii appears to represent parallel incipient ecological speciation within Metrosideros. Greater genetic distance among the more common varieties on the oldest volcano and an inverse relationship between allelic diversity and substrate age appear consistent with colonization of Hawai''i Island by older, partially diverged varieties followed by increased hybridization among varieties on younger volcanoes. This study demonstrates that broad population-level sampling is required to uncover patterns of diversification within a ubiquitous and long-lived tree species. Hawaiian Metrosideros appears to be a case of incipient radiation in trees and thus should be useful for studies of divergence and the evolution of reproductive isolating barriers at the early stages of speciation.     

Taxonomy and geographic distribution of <Emphasis Type="Italic">Carex lucorum</Emphasis> var. <Emphasis Type="Italic">austrolucorum</Emphasis> (section <Emphasis Type="Italic">Acrocystis</Emphasis>, Cyperaceae)

Carex lucorum currently comprises two morphologically similar varieties. We revise the taxonomy of C. lucorum, and map the distribution of the taxa. Based on multivariate analyses and analyses of variance of measured characters, allopatry, and previous studies revealing differences in achene micromorphology, chromosome differences, and flavonoid chemistry, we elevate C. lucorum var. austrolucorum to species status as C. austrolucorum. We provide an identification key to C. lucorum and its closest relatives.     

Progenitor-derivative speciation in Pozoa (Apiaceae, Azorelloideae) of the southern Andes

Background and Aims

Studies examining patterns and processes of speciation in South America are fewer than in North America and Europe. One of the least well documented processes has been progenitor–derivative speciation. A particularly instructive example occurs in the southern Andes in the genus Pozoa (Apiaceae, Azorelloideae), which consists of only two diploid outcrossing species, the widespread P. coriacea and the geographically and ecologically restricted P. volcanica. This paper tests the hypothesis that the latter species originated from the former through local geographical and ecological isolation by progenitor–derivative speciation.

Methods

DNA sequences were analysed from Pozoa and the related South American genera Asteriscium, Eremocharis and Gymnophyton from non-coding regions of the plastid genome, ndhF-rpl32 and rpl32-trnL, plus incorporation of previously reported rpl16 intron and trnD-trnT intergenic spacer sequences. Amplified fragment length polymorphism (AFLP) data from 105 individuals in 21 populations throughout the entire range of distribution of the genus were used for estimation of genetic diversity, divergence and SplitsTree network analysis. Ecological factors, including habitat and associated species, were also examined.

Key Results

Pozoa coriacea is more similar genetically to the outgroup genera, Asteriscium and Eremocharis, than is P. volcanica. At the population level, only P. volcanica is monophyletic, whereas P. coriacea is paraphyletic. Analyses of genetic differentiation among populations and genetic divergence and diversity of the species show highest values in P. coriacea and clear reductions in P. volcanica. Pozoa coriacea occurs in several types of high elevation habitats, whereas P. volcanica is found only in newly formed open volcanic ash zones.

Conclusions

All facts support that Pozoa represents a good example of progenitor–derivative speciation in the Andes of southern South America.     

共头霉的单孢孢子囊变种

我们从江苏、浙江两省采到的一些样品中分离得到六株毛霉菌种并鉴定为分别属于三个变种的同一个新种,即单孢共头霉原变种(Syncephalastrum monosporum Zheng et al.sp. nov. var. monosporum),单孢共头霉冠囊变种(Syncephalastrum monosporum Zheng et al. var. cristatum Zheng et al. var. nov.),以及单孢共头霉多重生变种(Syncephalastrum monosporum Zheng et al. var. pluriproliferum Zheng et al. var. nov.).它们与共头霉属的唯一已知种总状共头霉(Syncephalastrum racemosum Cohn ex Schroeter)的主要区别在于全部孢子囊都是单孢的小型孢子囊(柱孢囊)而不是像后者一样孢子成单行排列的多袍柱孢囊.我们把这些菌归人共头霉属而没有为它们专门成立一个新属的理由除因它们与总状共头霉有明显的亲缘关系外,主要还因我们认为在不具备其它重要区别特征的情况下,在毛霉目的分类中,无论在科级或属级的水平上,都不应过分强调单孢孢子囊的作用.尽管单孢共头霉是毛霉目内唯一具单孢子柱孢囊的种,我们仍然把它们归入共头霉属内.至于我们为什么要把这六株菌鉴定为一个种的三个变种而不是三个各自独立的种,则是由于我们承认共头霉属的唯一已知种总状共头霉是一个变异性很大的种而并没有把它分成许多不同的种,因此,我们对这个属的另外一个种,即单孢共头霉同样采用较大的种概念.     

Reproductive success and genetic divergence among varieties of the rare and endangered <Emphasis Type="Italic">Astragalus cremnophylax</Emphasis> (Fabaceae) from Arizona,USA

Populations of Astragalus cremnophylax from Arizona and related A. humillimus from New Mexico were assessed for morphological, reproductive, genetic, and ecological differences. Results suggest that some of the taxa (i.e., A. cremnophylax var. cremnophylax and A. humillimus) are poor reproducers and environmental fluctuation is not likely a factor contributing to low fecundity in these species. Astragalus cremnophylax var. cremnophylax appears to have low fecundity due to inbreeding depression. Allozyme data from 18 loci show little within-population and taxon genetic variability. Most genetic variability is distributed among populations and taxa. The population of A. cremnophylax var. cremnophylax from the Grand Canyon (South Rim) was genetically depauperate, indicative of the bottleneck caused by historic trampling at this viewpoint. Cape Final, a population of A. cremnophylax var. cremnophylax on the Grand Canyon (North Rim) is genetically different from typical materials of this taxon (South Rim) and is more closely related to other taxa within this species complex. However, the other varieties of A. cremnophylax are more closely related to A. humillimus than the population at Cape Final, suggesting potential species status for Cape Final materials based on allozyme divergence.     

Floral divergence in closely related Leucospermum tottum (Proteaceae) varieties pollinated by birds and long-proboscid flies

The Proteaceae are renowned for their floral diversity but surprisingly the role of pollinators in driving evolutionary divergence in this family has been underexplored. Here we focus on recently diverged taxa to gain insight into the processes that generate diversity by testing whether two varieties of Leucospermum tottum might have originated by pollinator mediated adaptive divergence. L. tottum var. tottum has pale salmon-coloured horizontally-oriented flowers, long nectar tubes, and small volumes of concentrated nectar. L. tottum var. glabrum has red and yellow vertically oriented flowers, short nectar tubes, and large volumes of dilute nectar. Despite the morphological divergence, the varieties are indistinguishable using eight molecular markers, indicating a very early stage of differentiation. Consistent with their morphologies, L. tottum var. tottum is pollinated by long-proboscid flies (Philoliche rostrata and Philoliche gulosa), Cape sugarbirds (Promerops cafer), and, to a lesser extent, by Orange-breasted sunbirds (Anthobaphes violacea), whereas, L. tottum var. glabrum is pollinated only by Orange-breasted sunbirds. A. violacea visits both varieties, but makes more frequent contact with pollen presenters when foraging on L. tottum var. glabrum. The exclusion of birds caused a steeper reduction in seed production in L. tottum var. glabrum than in L. tottum var. tottum, consistent with specialization for bird-pollination in this variety. Additionally, L. tottum var. glabrum exhibits autogamy, whereas L. tottum var. tottum does not. Floral divergence between the two L. tottum varieties corresponds with divergence in pollinator use.     

Population variation and phylogeny in the endangered <Emphasis Type="BoldItalic">Chamaesyce skottsbergii</Emphasis> (Euphorbiaceae) based on RAPD and ITS analyses

Chamaesyce skottsbergii var. skottsbergii is federally listed as an endangered taxon, and is found in small and isolated populations restricted to calcareous soils in dry shrubland habitats on the Hawaiian islands of Oahu and Molokai. Concern over the genetic relationship among these disjunct populations arose as a result of threats to the habitat of the Oahu population. The populations were examined using random amplified polymorphic DNA (RAPD) markers and sequence analysis of the internal transcribed spacer (ITS) region of the rDNA cistron. Chamaesyce skottsbergii var. vaccinioides, a closely related variety found in several small populations on Molokai, was used for baseline comparison of the genetic divergence among populations. RAPD analysis demonstrated that variation within and among populations is the highest for any Hawaiian species examined. Polymorphism was greater than 95% within populations and was 99.4% at the species level. Similarly, measures of genetic similarity indicate that differentiation among these populations is higher than is known for some species. Both RAPD and ITS sequence analysis indicate that populations of C. skottsbergii var. skottsbergii on Oahu and Molokai are genetically distinct, and the extent of this genetic differentiation supports the recognition of these populations as distinct varieties. The Molokai population is in fact much more closely related to var. vaccinioides than to var. skottsbergii on Oahu, and thus should be recognized by the previously used variety name, C. skottsbergii var. audens. Further conservation measures for each of the varieties are addressed.     

Taxonomic Study of Linaria depauperata and L. supina Complexes in Eastern Spain

Morphological characteristics were studied in two groups ofclosely related taxa of sectionSupinae , Linaria depauperataand L. supina, from eastern Spain. Vegetative, floral and seedcharacteristics were of little use in distinguishing betweenthese taxa as the ranges for all the taxa studied overlapped.Flower colour could be used as a diagnostic character for somebut not all of these taxa. Seed coat characters were of hightaxonomic value, both when trying to distinguish among thesetwo groups, and the taxa included within them, and also whenestablishing relationships among the taxa studied. Some differenceswere found in the indumentum distribution and density. Threetypes of trichomes were identified, two of them eglandular andcommon to all taxa. The third type of trichome was a simplegland, that varied in the number of cells in the stalk and gland.Trichome length and wall width of stalk cells allowed severalgroups of taxa to be distinguished. Similarity relationshipsamong the samples studied are shown in a UPGMA phenogram. Accordingto these results, two new species, L. cardonica and L. sulphurea,are described. L. arabiniana is conspecific with L. depauperatasubsp. hegelmaieri. A key to identify the different taxa isprovided. Copyright 2001 Annals of Botany Company Scropulariaceae, Antirrhineae, taxonomy, morphological characters, seed-coat, trichomes, Linaria depauperata,Linaria supina     

Levels of seed proteins in Citrullus and Praecitrullus accessions

Variation among 17 accessions of Citrullus lanatus from different geographic regions and interspecific relationships of six taxa of Citrullus and Praecitrullus were studied using electrophoretic patterns of their seed storage proteins. Globulins, the salt soluble proteins, represented the major fraction with their proportion varying between 56.6% and 67.0%. These were followed by albumins (16.6–20.8%) and glutelins (13.5–18.5%) with prolamins as the lowest (2.2–4.1%) of the four fractions. Two-dimensional gel electrophoresis under nonreducing conditions in the first dimension and reducing conditions in the second revealed disulphide-bonded subunit pairs of molecular weight 53, 52, 50 and 41 kDa, unlike the single subunit pair generally reported in different cucurbits, each consisting of a large and a small subunit. In the UPGMA dendrogram based on polypeptide patterns, the occurrence of C. lanatus var. lanatus, C. lanatus var. citroides and C. lanatus accession PI 482318 in one subcluster suggested that phylogenetically C. lanatus var. citroides and C. lanatus var. lanatus are closely related. The recently described annual wild species, Citrullus rehmii, occurred independently nearest to the subcluster of these cultivated and wild taxa. Citrullus colocynthis, the perennial wild species occurred farther from this cluster showing relatively more genetic distance from the watermelons. Praecitrullus fistulosus was outclustered and appeared genetically distant from all the Citrullus taxa; this supported its placement in a separate genus unlike its nomenclature as a botanical variety of watermelon or as a separate species of Citrullus proposed in certain earlier studies.     

Leaf anatomical studies of Chamaecrista subsect. Baseophyllum (Leguminosae, Caesalpinioideae): new evidence for the up-ranking of the varieties to the species level

This study aims to determine whether morphoanatomical characters of the leaves of the species of Chamaecrista sect. Absus subsection Baseophyllum could be used to support an up-ranking of C. cytisoides varieties to the species level as previously defined by molecular studies. The significance of anatomical adaptive strategies to arid environments is also discussed. Standard light microscopy techniques and histochemical tests were used for both morphoanatomical and histochemical characterization of the leaves. All the species studied share a single-layered epidermis, actinodromous–camptodromous–brochidodromous type of venation, vascular bundles surrounded by layers of fibers bounded externally by a sheath of cells containing solitary crystals, enlarged tracheids at the vein endings, vascular petiole/rachis tissue with a parenchymatous pith, accessory vascular bundles, mucilage idioblasts and hypodermis in the mesophyll, colleters, and non-secretory trichomes. The position and type of stomata, type of mesophyll, number of palisade and spongy parenchyma layers, position of mucilage idioblasts in the mesophyll, and the number of accessory vascular bundles of petiole/rachis provided useful characters for discriminating the eight species of the subsect. Baseophyllum. Histochemical tests reveal the presence of total polysaccharides, pectins, mucilage and phenolic compounds in the idioblasts. Other xeromorphic characters such as thickened outer periclinal cell walls, compact mesophyll, mucilage idioblasts and hypodermis in the mesophyll may help enable the studied species to survive in exposed sunny areas.     

凝胶电泳与共头霉分类

对于共头霉的唯一已知种总状共头霉Syncephalastrum racemosum Cohn ex Schroet.(S 1)和新发现的具单孢孢子囊的新种单孢共头霉下的三个变种,原变种S.monosporum Zheng et al. var. monosporum( S7, S8, S9),冠囊变种var. cristatum Zheng et al. (S10, S11)及多重生变种var. pluriproliferum Zheng et al.(S12) 6株菌的蛋白和酯酶进行了聚丙烯酰胺凝胶电泳的研究.这4个分类群的蛋白图谱和酯酶酶谱互不相同,而同一分类群内各个菌株之间则有很高的相似性.从计算出的相似性百分数来看,3个新变种相互之间有较为密切的关系,而和S. racemosum虽然较疏远,但也有相当程度的亲缘关系.这些结果被认为支持了根据形态鉴定而定这三个新变种属于同一新种内并将其和S. racemosum一并归属于一个属内.由此可见,聚丙烯酰胺凝胶电泳是共头霉分类的有用的辅助手段.