Lip anatomy and its implications for the pollination mechanisms of Bulbophyllum species (Orchidaceae)

BACKGROUND AND AIMS: The lip structure of six Brazilian and one Asiatic species of Bulbophyllum with wind-assisted fly pollination (B. involutum, B. ipanemense and B. weddellii) and non-wind-assisted fly pollination (B. epiphytum, B. glutinosum, B. regnellii and B. rothschildianum) was studied to investigate the presence of secretory tissues related to these pollination mechanisms. METHODS: The lip study was carried out through scanning electron microscopy (lip surface) and light microscopy (anatomical features). KEY RESULTS: In most of the species studied, the osmophores (odour glands) were located in the lobes and in the upper surface of the lip callus. Differences in the lip structure were observed between the two groups (the presence of a nectary and the extent of osmophore surface), depending on the mechanism of pollination. Nectaries were found in the cavity callus in B. ipanemense, B. involutum and B. weddellii, even though their pollinators were presumably attracted by the instinct to oviposit. CONCLUSIONS: These findings corroborate the hypothesis that, because pollination in these species is dependent on an unpredictable external factor (wind), nectar is necessary to keep the insect in the flower for a long period. Despite the occurrence of a liquid-like nectar in the flowers of B. epiphytum, B. glutinosum, B. regnelli and B. rothschildianum, no anatomical evidence for nectaries was found in the lips of these species, although a similar structure may occur in another region of the flowers. This observation agrees with the fact that pollination by lip movement in the latter species requires only gravity, with no additional mechanism being needed to keep the flies in the flower.     

Bulbophyllum wuzhishanensis (Orchidaceae), a new species from Hainan, China

Bulbophyllum wuzhishanensis, a new species from Hainan, China, is described and illustrated. The new species is probably related toBulbophyllum ledungense, but differs from it by having a long inflorescence, a column without stelids, and a longer lip.     

Differential cell enlargement and its possible implication for resupination in Lemboglossum bictoniense (Orchidaceae)

Changes in the structural features of cell populations in the pedicel of Lemboglossum bictoniense (Bateman ex. Lindley) Halbinger were examined by means of light microscopy in relation to resupination, a twisting of the pedicel through 180^o prior to flower opening. Serial sections in transverse and longitudinal planes were taken from pre-resupinate and fully resupinate pedicels of flowers from a single inflorescence, and comparisons made between the tissues. The pedicel is a prismatic cylinder flattened on three sides, producing three distinct ribS. Each rib contains one central vascular bundle enclosed by cortical parenchyma. Intervening cortical parenchyma forms flanks external to a central core of three vascular bundles, each of which is split into three distinct traces at this level. Resupination is accompanied by axial and radial expansion of cortical parenchyma. Specialized raphide-bearing cells in the cortex expand axially doubling their length in the ground parenchyma. These raphide cells are localized in the rib cortex, and their expansion is reflected in greater elongation of the ribs relative to flank areas. The extra rib length is accommodated by a lateral displacement (twisting) of the ribs around the central axis of the pedicel. Tissue distortion is reduced by cell division, expansion of intercellular spaces and a radial contraction of pith parenchyma. Raphide cell elongation could be a contributing factor in pedicel twisting. The direction of resupination may be controlled by the organization of these cells into arcs on one or other side of the rib vascular bundle.     

A remarkable new Bulbophyllum, sect. Sestochilus (Orchidaceae) from Thailand

Ongoing studies show that what hitherto in Thailand and neighboring countries have been gathered under one variable species, Bulbophyllum lobbii , must be separated in a number of distinct, well defined species. One such. B. smitinandii , is treated here.     

The gynostemium of Bulbophyllum ecornutum (J. J. Smith) J. J. Smith (Orchidaceae)

RASMUSSEN, F. N., 1985. The gynostemium of Bulbophyllum ecornutum (J. J. Smith) J.J. Smith (Orchidaceae) . Stages in the development of the gynostemium of Bulbophyllum ecornutum demonstrate that the pollinium stalk is a hamulus in this and in a closely related species, B. gibbolabium . A hamulus arises by apical growth and reflexion of the median carpel. Hamuli have recently been discovered in several orchid genera, and a transverse fold of the rostellar apex is already known from a large group of orchids. The closely related B. cornutum has a quite different gynostemium structure.     

Temporal variation in pollinarium size after its removal in species of Bulbophyllum: A different mechanism preventing self-pollination in Orchidaceae

InBulbophyllum involutum andB. ipanemense (Orchidaceae), two closely related species, shortly after removal the pollinarium has a diameter of approximately twice that of the entrance of the stigmatic cavity, requiring a mean time of 105 to 135 minutes to shrink in width and allow pollination. Because the pollinators of these species remain for some minutes in the same flower after removing the pollinia this mechanism, previously unknown inOrchidaceae, may be very important in preventing self-pollination. This mechanism does not occur inB. weddellii, and the pollinator does not remain in the flower after removing the pollinia. The smaller diameter of the stigmatic cavity inB. involutum reduces by 50% the chances of interspecific pollination withB. weddellii, and interspecific crossing is strictly unidirectional. This is important in maintaining isolation between these sympatric species, which share the same pollinators and have synchronized flowering.     

Bird pollination in South African species ofSatyrium (Orchidaceae)

Field observations showed that three South African orchid species,Satyrium carneum, S. coriifolium andS. princeps, are pollinated by sunbirds. Foraging sunbirds insert their bills into the labellum chamber of the flowers and suck nectar from the labellum spurs with their tongues. The column overarches the entrance to the labellum and pollinaria become affixed to the upper mandible of the bill. Birds often attempt to remove pollinaria by rubbing their bills against a branch, but are mostly unsuccessful due to the large plate-like viscidia which attach the pollinaria very firmly to the bill. Other modifications for bird pollination in theseSatyrium species may include the red, carmine or orange colour of the flowers, sturdy inflorescence stems used for perching and large amounts of dilute nectar in the spurs. EachSatyrium species was pollinated by several species of sunbird, and despite some differences in flowering time, occasional hybrids occur at a site whereS. carneum andS. coriifolium share the same sunbird pollinators.     

A new species ofLiparis (Orchidaceae) from India

Liparis indiraii spec. nova from India is close toL. alata A. Rich. andL. atropurpurea Lindl.     

Chromosomal diversity in two synchronopatric species of Hoffmannseggella (Orchidaceae)

Hoffmannseggella viridiflora Verola & Semir (Laeliinae, Orchidaceae) is a recently discovered species in the campos rupestres vegetation of the Espinhaço Range, MG, Brazil, in synchronopatry with H. bradei (Pabst) V. P. Castro & Chiron. Both morphological and phenological studies indicate that these species are closely related. To substantiate the differentiation of these two species we examined their chromosome numbers and morphologies. The two species had different chromosome numbers, with H. bradei having 2n = 40 and H. viridiflora having 2n = 44 chromosomes, an aneuploid number not previously documented in the genus. Meiotic behavioral studies undertaken with H. bradei revealed many abnormalities related to bivalent numbers and chromosome migration, suggesting that meiotic abnormalities could generate aneuploid gametes and perhaps aneuploid zygotes. Karyotype formulas and chromosome morphologies are quite different between the species, so H. viridiflora was not directly derived from H. bradei through simple chromosome additions. Complementary analyses are necessary to understand the process and species involved in the origin of H. viridiflora.     

Chromosome numbers and karyotypes of Catasetum species (Orchidaceae)

Mitotic chromosomes of 12 species of Catasetum were assessed to contribute with the karyotypic study of the subtribe Catasetinae (Orchidaceae), expanding the knowledge of this group in terms of chromosomes and supporting its taxonomic and evolutionary analysis. The species are maintained in cultivation in the greenhouse of the Department of Plant Biology/IB/UNICAMP and in the “Orquidário Frederico Carlos Hoehne” of the Botanical Garden of São Paulo. Chromosome counts ranged from 2n = 54 to 2n = 108. Karyotypes were prepared for all species studied, in which there was a predominance of metacentric chromosomes and some submetacentric ones. The chromosome size ranged from 0.5 to 4.9 μm, the total chromosome length ranged from 34.7 to 78.7 μm and the asymmetry index TF% ranged from 21.2 to 42.3. The results obtained so far favor the taxonomy of the genus, allowing to distinguish species with very similar external morphology.     

A new species of Thrixspermum (Orchidaceae) from China

A new species from China, Thrixspermum tsii (Orchidaceae), is described and illustrated and its relationships to T. centipeda and T. subulatum are discussed.     

A new species of Ornithocephalus (Orchidaceae) from Panama

Ornithocephalus aristatus, a new species from Panama, is described and illustrated. Among the species of the genusOrnithocephalus, it can be distinguished by the nonresupinate flowers, the sepals each provided with a flexuous awn half as long as the sepal itself, the porrect petals with revolute margins, the hastate lip with triangular-ovate, crose lateral lobes, the linear, acute midlobe, conduplicate and subreflexed at apex, and the dise with a bilobed, obreniform callus provided with a conical tuft of stiff hairs. A key to the species ofOrnithocephalus from Panama is provided.     

New Malaxis species (Orchidaceae, Epidendroideae) from Colombia

Two new species of the genus Malaxis are described and illustrated based on the Colombian material. Their taxonomic affinities are briefly discussed and the relevant floral elements of the most similar species are illustrated. The differences between genera Malaxis and Micorstylis are compared.     

New species of the subtribe Goodyerinae (Orchidaceae) from Colombia

Seven new species of the subtribe Goodyerinae, six of Microchilus and one of Aspidogyne, are described and illustrated based on Colombian material. The information about the distribution and ecology of the new entities as well as brief taxonomic notes are provided.     

New species of the genus Epistephium (Orchidaceae, Vanilloideae)

The morphological study of the herbarium material representing Epistephium (Orchidaceae, Vanilloideae) led to the discovery of two groups of specimens that significantly differ from all known species of the genus. The results of literature data study and of comparative analysis of those and other specimens suggest that these collections represent new taxa that we describe as E. garayi and E. kubiyuense. The distinguishing features of the species are indicated. As both new species are reported from Colombia (E. garayi, also from Guyana), the key for the determination of all Colombian representatives of the genus is included. Information on the ecology and distribution of newly described taxa is presented.     

A new species of Maxillaria (Orchidaceae) from Costa Rica

Maxillaria suaveolens Barringer from the Gulfo Dolce region of Costa Rica is described and illustrated.     

Evolution,pollination, and systematics of the tribeNeottieae (Orchidaceae)

The various classifications of the orchid tribeNeottieae are reviewed and a new classification is proposed that divides the tribe into three subtribes,Neottiinae, Limodorinae, andCephalantherinae, based primarily on characters of the column (gynostemium). A cladistic analysis illustrates that these three subtribes are more closely related to one another than either is to any other group in subfam.Neottioideae, although there are very few apomorphic characters for the tribe. Pollination biology is also discussed showing links between breeding systems and distribution. There is also a possible role between column and labellum morphology and the emergence of a deceptive pollination syndrome from one of reward.     

Phylogenetic constrains on mycorrhizal specificity in eight Dendrobium(Orchidaceae) species

Plant phylogeny constrains orchid mycorrhizal(OrM) fungal community composition in some orchids. Here, we investigated the structures of the OrM fungal communities of eight Dendrobium species in one niche to determine whether similarities in the OrM fungal communities correlated with the phylogeny of the host plants and whether the Dendrobium-OrM fungal interactions are phylogenetically conserved. A phylogeny based on DNA data was constructed for the eight coexisting Dendrobium species,and the OrM fungal communities were characterized by their roots. There were 31 different fungal lineages associated with the eight Dendrobium species. In total, 82.98% of the identified associations belonging to Tulasnellaceae, and a smaller proportion involved members of the unknown Basidiomycota(9.67%). Community analyses revealed that phylogenetically related Dendrobium tended to interact with a similar set of Tulasnellaceae fungi. The interactions between Dendrobium and Tulasnellaceae fungi were significantly influenced by the phylogenetic relationships among the Dendrobium species. Our results provide evidence that the mycorrhizal specificity in the eight coexisting Dendrobium species was phylogenetically conserved.