A new spiny, cushion-like Euphorbia (Euphorbiaceae) from south-west Iran with special reference to the phytogeographic importance of local endemic species

Euphorbia acanthodes Akhani is described as a new gypsophilous species from south-west Iran. The affinity, morphological and carpological features, and habitat of the species are discussed. A list of a further 36 interesting endemic species of south-western Iran and adjacent areas is given with notes on their affinities and distribution. These include Centaurea gudrunensis Boiss. & Hausskn., as a new record from Iran. The specific status of Pteropyrum naufelum Al-Khayat is confirmed and it is suggested that P. noëanum Boiss. ex Meisn. is synonymous with P. aucheri Boiss. The biogeographic importance of the so-called 'Persian foothills', and biodiversity conservation status of the area are discussed, together with distribution maps of 12 species. It is concluded that the majority of the endemic species in the southern and south-western parts of Iran are Irano–Turanian or have their origins in the Irano–Turanian region. Therefore, it is questionable to consider the area as part of either the Saharo–Sindian, Sudanian or Sudano–Zambezian regions.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 107–121.     

Evolutionary bursts in Euphorbia (Euphorbiaceae) are linked with photosynthetic pathway

The mid‐Cenozoic decline of atmospheric CO₂ levels that promoted global climate change was critical to shaping contemporary arid ecosystems. Within angiosperms, two CO₂‐concentrating mechanisms (CCMs)—crassulacean acid metabolism (CAM) and C₄—evolved from the C₃ photosynthetic pathway, enabling more efficient whole‐plant function in such environments. Many angiosperm clades with CCMs are thought to have diversified rapidly due to Miocene aridification, but links between this climate change, CCM evolution, and increased net diversification rates (r) remain to be further understood. Euphorbia (～2000 species) includes a diversity of CAM‐using stem succulents, plus a single species‐rich C₄ subclade. We used ancestral state reconstructions with a dated molecular phylogeny to reveal that CCMs independently evolved 17–22 times in Euphorbia, principally from the Miocene onwards. Analyses assessing among‐lineage variation in r identified eight Euphorbia subclades with significantly increased r, six of which have a close temporal relationship with a lineage‐corresponding CCM origin. Our trait‐dependent diversification analysis indicated that r of Euphorbia CCM lineages is approximately threefold greater than C₃ lineages. Overall, these results suggest that CCM evolution in Euphorbia was likely an adaptive strategy that enabled the occupation of increased arid niche space accompanying Miocene expansion of arid ecosystems. These opportunities evidently facilitated recent, replicated bursts of diversification in Euphorbia.     

Euphorbia gokakensis sp. nov. (Euphorbiaceae) from sandstone formations in Karnataka,India

Euphorbia gokakensis, a new succulent species of Euphorbiaceae, is described from the Belgaum district of Karnataka, India. The new species belongs to Euphorbia subgen. Euphorbia, and closely resembles Euphorbia caducifolia Haines. However, it is distinguished by its characteristic dwarf habit forming a compact cushion that hardly exceeds 50 cm in height.     

Seed production, predation and dispersal in the Mediterranean myrmecochore Euphorbia characias (Euphorbiaceae)

Seed production of a population of 193 reproductive individuals of Euphorbia characias from the north-east Iberian peninsula was estimated at 155 000 seeds per year The dehiscence period lasts for four weeks The timing of ballistic dispersal is uniformly distributed throughout the day Seeds remain on the surface a mean time (± SE) of 52.3 ± 6.7 mm Several and species take the seeds in varying proportions Messor barbarus (0 225), a granivorous ant which eats the seeds, Aphaenogaster senilis (0 313), Pheidolc pallidula (0 296) and Tapinoma nigerrimum (0 162) which take the seeds to their nests but do not eat them Half a million ant foraging trips per day indicate a very strong short term influence of ants on fate of Euphorbia seeds Ants as a group have a dual role of predation and dispersal of Euphorbia characias seeds The characteristics of this Euphorbia (sclerophylly, diplochory, firmness of elaiosome, absence of subsidiary myrmecochorous features) better fit the syndrome described for Australian myrmecochores than the one proposed for European and North American myrmecochores     

Euphorbia venkatarajui sp. nov. (Euphorbiaceae) from Eastern Ghats of Andhra Pradesh,India

Euphorbia venkatarajui, a new succulent species of Euphorbiaceae, is described from Kurnool district of Andhra Pradesh state, India. The new species belongs to the subgenus Euphorbia, and it closely resembles Euphorbia gokakensis S.R. Yadav, Malpure and Chandore and E. caducifolia Haines., but differs in certain distinct characters.     

Pollinator-mediated interactions between a pathogenic fungus, Uromyces pisi (Pucciniaceae), and its host plant,Euphorbia cyparissias (Euphorbiaceae)

The plant Euphorbia cyparissias is commonly infected by rust fungi of the species complex Uromyces pisi. When infected, E. cyparissias is unable to flower, but instead is induced by the fungus to form pseudoflowers. Pseudoflowers are rosettes of yellow leaves upon which the fungus presents its gametes in a sweet-smelling fungal nectar. We hypothesized that the fungi, as they are heterothallic, are dependent on insect visitation to cross-fertilize their mating types. We confirmed that insects are required with an insect exclusion experiment. We further hypothesized that pseudoflowers of U. pisi interact with uninfected true host flowers through insects during their period of co-"flowering" in early spring. We conducted artificial array experiments in the field to test whether the two species share insects and whether they influenced each other's insect visitation. Insects moved between true flowers and pseudoflowers, but true flowers received more visits over all. Pseudoflowers and true flowers did not influence each other's visitation rates in mixtures. However, shorter visits were observed on pseudoflowers in mixtures than monocultures, suggesting that true flowers might be competitors for pseudoflowers. Further experiments are needed to determine whether the similarity of pseudoflowers to true flowers is adaptive.     

中国大戟属13种15个居群的核型报道

对国产大戟科Euphorbiaceae大戟属Euphorbia的13种15个地方居群的核型进行研究, 以期为解决该属的种间亲缘关系和物种进化机制提供依据。结果如下: 地锦E. humifusa (望江居群), 2n=2x=22=20m (2SAT)+2sm; 地锦E. humifusa (红旗村居群), 2n=2x=22=18m+4sm; 千根草E. thymifolia, 2n=4x=40=40m; 斑地锦E. maculata, 2n=4x=40=36m+4sm; 银边翠E. marginata, 2n=8x=56=40m+ 8sm+8st; 铁海棠E. milii, 2n=4x=40=32m+8sm; 金刚纂E. neriifolia, 2n=6x=60=6m+36sm+12st+6t; 火殃勒E. antiquorum, 2n=6x=60=24m+24sm+12st; 一品红E. pulcherrima, 2n=4x=28=24m(3SAT)+4sm; 猩猩草E. cyathophora, 2n=4x=28=16m+12sm; 齿裂大戟E. dentata, 2n=4x=28=28m; 续随子E. lathyris, 2n=2x=20=12m+8sm; 泽漆E. helioscopia, 2n=6x=42=36m+6sm; 乳浆大戟E. esula (陈家沟居群), 2n=2x=20=14m+6sm; 乳浆大戟E. esula (樱桃沟居群), 2n=4x=40=32m+8sm。千根草和斑地锦两个种的核型以及乳浆大戟的四倍体居群核型均为首次报道。     

Pectin distribution pattern in the apertural intine of Euphorbia peplus L. (Euphorbiaceae) pollen

The apertural inner layer (intine) of Euphorbia L. pollen grains has a characteristic but original structure that has paired thickenings, one on either side of the colpus. To determine the nature and role of this intine layer, pollen grains of Euphorbia peplus L. were germinated in vivo and in vitro. The germination process involves wall changes that facilitate formation of the pollen tube and its subsequent growth. In the thickenings of the intine of E. peplus, the unesterified pectin epitopes are more densely localised in the inner part of the middle intine. No such epitopes are located in the intine portion adjacent to the plasma membrane (cellulosic endintine). Unesterified pectin epitopes are also localised in the outer part of the intine but are restricted to the centre of the aperture, around and in the pore. The de-esterification of pectins is very advanced at the time of dehiscence and pollen germination. The stratification of the aperture intine may take the following pathway at the time of germination: the thin outer zone of the intine in the pore region becomes disorganised and undergoes dissolution with liberation of unesterified and esterified pectins; the middle intine thickenings undergo an important elastic modification, but without liberation of unesterified pectins; the cellulosic inner intine is the progenitor of the pollen tube wall. This special intine of E. peplus is an adaptation to the hydration process preceding germination, increasing intine and pollen grain wall elasticity.     

Floral ontogeny in Scirpus, Eriophorum and Dulichium (Cyperaceae), with special reference to the perianth

BACKGROUND AND AIMS: Based on molecular phylogenetic analysis, it has been suggested recently that the Cyperaceae comprises only two subfamilies: the Mapanioideae and the Cyperoideae. In most flowers of the Cyperoideae, the whorl of inner stamens is reduced, resulting in tetracyclic flowers. In the more primitive (scirpoid) genera within the Cyperoideae, the perianth consists of two polysymmetric whorls, whereas the perianth parts in the more derived genera have been subject to modifications and/or reduction. Comparative studies of the many silky hairs of Eriophorum and of the eight bristles of Dulichium have given rise to much discussion about their homology. METHODS: The spikelet and floral ontogeny in freshly collected inflorescences was investigated using scanning electron microscopy. KEY RESULTS: Complete floral ontogenies are presented for Scirpus sylvaticus L., Eriophorum latifolium Hoppe and Dulichium arundinaceum (L.) Britton, with special reference to the perianth. The results in S. sylvaticus confirm the trimerous monocot-like organization of the flower. It is used as a model for floral development in Cyperoideae. In the early developmental stages, the androecium of E. latifolium is surrounded by a massive perigonial primordium, from which the many hair-like bristles originate. Consequently, the stamens develop among the hair primordia, more or less simultaneously. The hairs are arranged in whorls, which develop centripetally. The development of the perianth in D. arundinaceum starts with the formation of three initial perianth primordia opposite the stamens. Subsequently, two more abaxial bristle primordia, alternating with the stamens, originate simultaneously with the appearance of three adaxial bristle primordia in the zone where an adaxial inner perianth primordium is expected. CONCLUSIONS: The floral development in E. latifolium and D. arundinaceum can be considered as variations upon the scirpoid floral ontogenetic theme.     

Evolution and speciation in Pellia,with special reference to the Pellia megaspora-endiviifolia complex (Metzgeriales), II. Cytology

Abstract

A unique karyotype within the genus Pellia, both in terms of chromosome structure and in the distribution of heterochromatin as defined by Giemsa C-banding, supports the taxonomic recognition of P. megaspora. Resembling P. endiviifolia more closely than P. epiphylla or P. neesiana in its heterochromatin content, the species differs significantly in karyotype symmetry and the absence of an m-chromosome. Comparison of P. endiviifolia from Britain, Japan and Canada has identified clear and extensive evidence of cytological polymorphism.     

Euphorbia aaron-rossii (Euphorbiaceae), a new species from Marble and Grand Canyons of the Colorado River,Arizona

The new species,Euphorbia aaron-rossii from along the Colorado River within the inner gorge of Marble Canyon and Grand Canyon, Coconino Co., Arizona, is described, mapped, and illustrated. Scanning electron micrographs of the seed coat are included. It clearly belongs to subgenusAgaloma sectionTithymalopsis, where it is most closely related toE. wrightii.     

Systematics of Dendrobiinae (Orchidaceae), with special reference to Australian taxa

The systematics of subtribe Dendrobiinae, Dendrobium, and Australian dendrobiums in particular, are reviewed. Molecular approaches have delimited the subtribe, established Asian and Australasian clades and clarified relationships at some levels within them. At most lower taxonomic levels within Dendrobium s.l., resolution has been partial. Morphological and molecular phylogenetics indicate that Dendrocoryne, Rhizobium and some other sections are not monophyletic, with morphological analyses providing the greatest resolution into groups corresponding with biogeography. For most sections, sampling is too incomplete to determine relationships and monophyly. Distribution, pollination syndromes, breeding systems, fertility and specialized anatomical features contribute little to classification. Natural hybrids are more common than previously stated and may have played a role in the high level of homoplasy and evolution of Australian epiphytes. There is little support for splitting Dendrobium into many genera and species based on terminal clades. The evidence is interpreted as favouring recombination of Cadetia, Flickingeria and Diplocaulobium within the conserved broad genus Dendrobium. Nomenclatural stability is retained in continuing to use the long‐held subgeneric sectional classification, including many of the sections of Schlechter, and infraspecific ranks of subspecies and varieties. In Dendrocoryne, Thelychiton, Tropilis and Tetrabaculum are rejected, as is Dockrillia in Rhizobium. Proposals to elevate infraspecific taxa to species level for variable species complexes are not supported by current morphological or molecular data based on slowly evolving DNA regions. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 166 , 105–126.