Euphorbia angustifrons mihi

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Acer Bosniacum mihi

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Alyssum Heinzi mihi?

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Gagea tisoniana, a new species of Gagea Salisb. sect. Gagea (Liliaceae) from central Italy

Gagea tisoniana Peruzzi et al. sp. nov. is described and its taxonomic relationship is discussed. The new species, which appears to be endemic to central Italy, is close to G. pratensis (Pers.) Dumort., G. pusilla (F. W. Schmidt) Sweet, and other mainly poorly known [i.e. G. succedanea Griseb. et Schenk, G. transversalis Stev., and G. paczoskii (Zapal.) Grossh.] or as yet undescribed taxa from eastern Europe and the eastern Mediterranean area. The recognition of the new taxon G. tisoniana is claimed on the basis of anatomical, karyological, ecological, and phytogeographical data. Maps of the Italian distribution of G. pratensis (2 n  = 60), G. pusilla (2 n  = 24), and G. tisoniana (2 n  = 24) are presented, together with an analytical identification key. Finally, G. pratensis is recorded here for the first time in Tuscany (Monte Cetona).  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 155 , 337–347.     

Gagea bohemica (Liliaceae), a highly variable monotypic species within Gagea sect. Didymobulbos

Abstract

Gagea bohemica s.l. (Liliaceae) consists of two morphologically extreme forms (saxatilis and bohemica) which depending on the varying opinions of the authors are considered as separate species, subspecies or as a single variable species. In this study, morphological (form and length of perianth segments, pilosity of pedicles and peduncles) and molecular data (cpDNA trnL–trnF IGS) of 55 samples corresponding to 43 populations from Western Europe to the Mediterranean area and eastern Caucasus were investigated. G. bohemica (Zauschn.) Schult. & Schult. f. represents a highly variable monotypic species from both morphological and karyological (2n = 24, 36, 48, 60, 72) aspects. Based on the molecular and morphological data presented here, a differentiation between specific and infraspecific taxa is not possible. We hypothesize that the morphological variability of this species is largely influenced by different site conditions and ploidy level.     

Systematics of Gagea and Lloydia (Liliaceae) and infrageneric classification of Gagea based on molecular and morphological data

Our study represents the first phylogenetic analyses of the genus Gagea Salisb. (Liliaceae), including 58 species of Gagea and 6 species of the closely related genus Lloydia Salisb. ex Rchb. Our molecular results support the infrageneric classification of the genus Gagea in sections according to Levichev and demonstrate that Pascher's subdivision of this genus into two subgenera can no longer be upheld. Certain Gagea sections (e.g., Gagea, Minimae, and Plecostigma) are well supported by cpDNA and nrDNA data. Gagea sect. Fistulosae is closely related to G. sect. Didymobolbos. Gagea sect. Graminifoliae and G. sect. Incrustatae are closely related to G. sect Platyspermum. The analyses support the monophyly of Gagea and Lloydia collectively. The molecular analyses reveal the basal position of G. graeca in proportion to all other species of Gagea and Lloydia investigated. Minor morphological differences could be established between both genera which support their close relationship.     

Die Embryosackentwicklung in der Gattung Gagea Salisb

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Hybridization drives speciation in Gagea (Liliaceae)

Hybridization seems to play an important role in speciation of Gagea Salisb., a genus which is characterised by polyploid taxa lines and in which diploids (2n = 24) appear only to be common in basal sections. Hybrid detection was applied utilising direct and cloning nrDNA ITS data (ITS1, 5.8S rDNA, ITS2) combined with neighbour and ribotype networks and discussed in connection with previously published cpDNA, morphological and karyological data of the authors. We have evidence of the hybrid origin of taxa within the section Gagea (G. pomeranica, G. megapolitana) and the monophyletic clade of sections Didymobulbos and Fistulosae (G. microfistulosa, G. polidorii, G. cf. bohemica). Morphologically and karyologically differentiated Gagea megapolitana and G. pomeranica, adapted to synanthropic habitats, represent both hybrids of G. pratensis × G. lutea. Gagea microfistulosa represents a hybrid of G. villosa × G. fragifera; Gagea polidorii could represent the reverse hybrid. G. glacialis is also closely related to the latter complex.     

Oscillaria caldariorum mihi n. sp. eine Plage des Warmhauses

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Photosynthetic compensation by the reproductive structures in the spring ephemeral Gagea lutea

Growth and reproduction of spring ephemerals inhabiting deciduous forests progress simultaneously during a short period from snowmelt to canopy closure. To clarify the mechanism to mitigate the cost of reproduction, contributions of foliar and non-foliar photosynthetic products to seed production were examined in a spring ephemeral Gagea lutea. Leaf growth, foliar and non-foliar photosynthetic activities, and total assimilated products were compared among reproductive-intact, floral bud-removal, and vegetative plants. Translocation of current photosynthetic products to individual organs was quantified by ¹³CO₂-trace experiment. Bulb growth was compared between hand-pollination and floral bud-removal treatments. Finally, seed set was compared between intact, leaf-clipping, and bract-clipping treatments. Fruit-forming plants retained leaves longer than vegetative and floral bud-removal plants, but the assimilative contribution of extended leaf longevity was negligible. Carbon supply by bract photosynthesis was large enough for fruit development, while carbon supply by fruit photosynthesis was offset by the high respiration loss. Foliar photosynthetic products were largely transported to bulbs, while translocation to reproductive functions was negligible. Because the floral bud-removal increased the bulb growth, lack of reproduction could lead to more storage. The leaf-clipping had no effect on seed production, while the bract-clipping significantly reduced the seed production. Therefore, current photosynthesis of leafy bracts might be a major carbon source for fruit development. This self-compensative mechanism of reproductive structure enables the continuous reproductive activity in this species.     

Speciation and evolution in the Gagea reticulata species complex (Tulipeae; Liliaceae)

For the 12 named taxa in the Gagea reticulata species complex, 609 cloned sequences of the low-copy nuclear gene malate synthase (MS) were used to investigate species relationships, using standard phylogenetic tools and network analyses. Three (homologous) copies of MS locus were present in each individual analyzed, and multiple alleles were present at most of these loci. Duplication of MS occurred after divergence of the G. reticulata complex. After comparisons, 591 sequence types (i.e. haplotypes) were identified, requiring implementation of novel statistical analyses to group haplotypes in a smaller number of groups/lineages to enable further study. Haplotype groups/lineages are not fully congruent with species limits with some widely present among species. MS genotypes at the root of the network are those of G. setifolia from central Iran, with more derived sequences in this species found in the west and northwest. Presence of ancestral genotypes in several other taxa may indicate either the retention of "ancestral" polymorphisms, more recent introgressive hybridization, or both. The relative DNA content of specimens was estimated with flow cytometry (FCM). The FCM analyses revealed two levels of DNA content (putatively "diploid" and "tetraploid"), but no correlation between number of MS gene copies and ploidy was found.     

内蒙古顶冰花属（百合科）一新种

报道了产于贺兰山的顶冰花属（百合科）一新种——贺兰山顶冰花Gagea alashanica Y. Z. Zhao & L. Q. Zhao。该种因柱头头状,鳞茎外皮上端向上延伸成圆筒状,抱茎,无附属小鳞茎,植物除基生叶外,茎上具有3-4枚附生叶,无明显总苞片而与新疆顶冰花G. neopopovii Goloskokov相似,但基生叶2枚,半圆筒形;鳞茎外皮向上延伸较短,长约2. 5cm,易于区别。     

Minor differences with big consequences: Reproductive patterns in the genus Gagea (Liliaceae)

Reproductive patterns in ten species of Gagea Salisb. were compared by counts and measurements of bulbs, bulbils and flowers in large cohorts including all life stages. Two types of bulbils were found: taxa with “type I bulbils” start to develop a single to several bulbils as soon as the replacement bulb has reached a certain diameter and then continue to form them indefinitely throughout the life of the plant. “Type II bulbils” are only temporarily produced in immature, non-flowering plants of some species, but not in fully grown, flowering individuals, a phenomenon termed “reproductive switch”. Patterns of bulbil formation are species-specific: G. davlianidzeae, G. nigra, G. peduncularis, G. pratensis, and G. spathacea produce only type I bulbils; G. angelae, G. fedschenkoana and G. lutea develop only type II bulbils. Both bulbil types occur simultaneously in G. fragifera and G. villosa. The quantitative investigations demonstrate the existence of species-specific thresholds for the development of bulbils as well as flowers. Compared to the adult volume of the replacement bulb (where 90% of all plants flower), both types of bulbils have usually low thresholds: 0–5% (type I, all but one species) and 3–13% (type II). Inflorescences develop if plants attain between 38 and 60% of the adult bulb volume. Minor changes in patterns of bulbil formation and thresholds for their development may ensure survival of highly sterile taxa (e.g. G. spathacea, G. fragifera). This, in turn, can facilitate speciation in the genus driven by both hybridization and polyploidization.     

Safeguarding the rare woodland species Gagea spathacea: Understanding habitat requirements is not sufficient

A large proportion of temperate forest plant diversity is found in the herb layer. However, for many of its species, little is known about their autecology, which makes it difficult to assess potential threats and efficiently safeguard the diversity of understorey herbaceous communities. This also applies to Gagea spathacea (Liliaceae), a globally rare spring geophyte, which mainly occurs in deciduous forests of northern Central Europe. We investigated the causal relationships between population characteristics of G. spathacea and abiotic site conditions across different forest communities in the center of its distributional range. Leaf length (a surrogate of the species' vegetative propagation) was positively related to soil moisture and soil nitrogen. Consequently, mean leaf length was highest in moist forest communities of the alliance Alno-Ulmion. Moreover, mean variability in leaf length was lowest in those forests, indicating a higher and more stable vegetative propagation via bulbils. We found no support for a significant relationship between leaf length and leaf density or between leaf length and flower formation. Population density varied strongly among forest sites, but was not related to soil moisture and hardly influenced by soil nitrogen. Our results suggest that soil water and nutrient supply play a vital role in determining the species' vegetative propagation, whereas the duration of habitat continuity is most likely an important determinant of population size and density. Conservation strategies therefore require a better understanding of the complex interrelationships between abiotic site conditions and the historical context-dependency of habitats.     

Microsporogenesis,pollen mitosis and pollen tube growth in Gagea villosa (Liliaceae)

In this study, Gagea villosa (Bieb.) Duby was investigated by using light microscopy methods in cytological and cytoembryological respects. Anthers were tetrasporangiate. Anther wall was formed with an epidermis, endothecium, middle layer and tapetum. Tapetum was glandular type and it began to degenerate when microspores released from tetrads. Tapetum cells generally have one or two nuclei. Mitosis seen in tapetum cells was generally normal but micronuclei were found in some of them. Fibrous thickenings were determined in endothecium. Microsporogenesis and pollen mitosis were generally regular. Cytokinesis was successive type. Meiosis in pollen mother cells was asynchronous in one anther locus. Mature pollen grains were 2-celled. Pollen sterility was found to be 24%. Some of the fertile pollen grains, smaller than the normal were seen at the end of the pollen mitosis. Microgametophyte development was examined in vivo and in vitro. Germination ratio of pollen grains in vitro was 4%. Generally swollen pollen tube tips and weak development of some curled pollen tubes were seen. Callose plug formation was seen only in vivo pollen tube growth.     

Bulbils contra seeds: reproductive investment in two species of Gagea (Liliaceae)

The reproductive biology of the sympatric species Gagea lutea and Gagea spathacea was analyzed morphologically and by resource allocation measurements. Both taxa reproduce vegetatively by bulbils. The hexaploid G. lutea regularly forms seeds, but flowering plants cease to produce bulbils. Seed set was never observed in nonaploid G. spathacea which does not stop vegetative reproduction when flowering. In this species, the pollen contains a high proportion of non-viable grains. Already sterile plants invest more resources (per cent of total nitrogen) into bulbils than G. lutea (10.9 vs. 5.9%). For flowering plants, the respective values are 6.1% (flowers) plus 18.4% (bulbils) for G. spathacea versus 14.8% (flowers only) for G. lutea. G. spathacea lost the ability to reproduce sexually and relies solely on vegetative reproduction. This seems to require the breakdown of the switch mechanism between the bulbil and flower formation (as in G. lutea) and a higher net investment in reproduction, hampering individual growth.     

Hybridity as a main evolutionary force in the genus Gagea Salisb. (Liliaceae)

Abstract

The important role of hybridity in the evolution of the genus Gagea is becoming clear, through morphological, karyological and molecular evidences. Several species were recently inferred or hypothesized to be of hybrid origin; especially in sect. Didymobulbos, sect. Fistulosae and sect. Gagea. Representative case studies, such as G. luberonensis J.-M. Tison, G. polidorii J.-M. Tison and G. pomeranica Ruthe, are presented and discussed.

Since many Gagea species show very reduced or null sexual reproduction vs. a massive vegetative propagation, there are several problems in distinguishing hybrids from hybridogenous species in this genus. The actual trend is to consider them at specific level because of their ability to stabilize, at least through vegetative propagation by bulblets and/or bulbils.