Evolution of resupination in Malagasy species of Bulbophyllum (Orchidaceae)

Fischer, Gunter A.; Gravendeel, Barbara; Sieder, Anton; Andriantiana, Jacky; Heiselmayer, Paul; Cribb, Phillip; Smidt, Eric de Camargo; Samuel, Rosabelle; Kiehn, Michael

doi:10.1016/j.ympev.2007.06.023

Cited by 40 publications

(61 citation statements)

References 32 publications

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“…(Russell et al, 2010b). In the case of Bulbophyllum, there are major clades confined to continental areas (Gravendeel et al, 2004;Fischer et al, 2007;Smidt et al, 2011), so, although the genus as a whole is cosmopolitan, its internal structure reflects more limited dispersability. In Polystachya, one clade has managed recently to migrate from Africa to both the New World and the Asian tropics (Russell et al, 2010a(Russell et al, , 2011, a situation again of a wet-forest species, much akin to the situation with Rhipsalis (see above), becoming successfully established after long-distance dispersal.…”

Section: Surprising Vicariant Patterns Of Relationshipsmentioning

confidence: 99%

Biogeographical patterns of plants in the Neotropics - dispersal rather than plate tectonics is most explanatory

Christenhusz

Chase

2012

Bot J Linn Soc

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The phylogenetic relationships of some Neotropical plant groups have proved to be different from expectation assuming plate tectonics as the underlying model, and these unanticipated relationships (and their timing) have required further work to explain how they came into existence. Well‐known Neotropical families, such as Bromeliaceae and Cactaceae, have one to a few species in Africa, but these can be explained by recent long‐distance dispersals; the estimated ages of the Transatlantic crown and stem clades of these families are of relatively recent origin, so long‐distance dispersal is the only possible explanation and plate tectonic explanations are not viable. Other families with a crown age appropriate to be explained by plate tectonics did not seem to have distributions indicating an involvement of long‐distance dispersal, but the advent of molecular systematics and molecular clocks has shown this to be otherwise. Families exhibiting this pattern include Fabaceae and Lauraceae (and many others), and in spite of the unlikely dispersal qualities of their generally large seeds, they exhibit many instances of long‐distance dispersal occurring throughout their evolutionary history; in fact, long‐distance dispersal is the most probable explanation to account for the current distributions of the great majority of land plant families. One factor that sometimes is overlooked is the boreotropics hypothesis, which may explain more recent connections between American, African and Asian floristic components. However, in some old lineages with small propagules that appear well adapted to long‐distance dispersal, such as Marattiaceae and Orchidaceae, we find a pattern suggesting that tectonics is the primary factor, with clades clearly restricted to one tropical region. These patterns appear to have little to do with dispersability and it is probable that their conforming to expected (tectonic) biogeographical patterns has to do with their specialized life‐history strategies that have acted to make intercontinental establishment unlikely even though dispersal almost certainly occurs. Molecular studies have identified additional, unanticipated clades, and these fit into the relictual category with what may be an overlay of old long‐distance dispersal events. Examples at the ordinal level are Crossosomatales and Huerteales, and we expect future studies to identify more of these relict and unexpected clades at many taxonomic levels. Overall, molecular systematic studies and molecular clocks have demonstrated that there are many more connections between the Neotropics and Palaeotropics, both Asia and Africa, than previously would have been thought under a plate tectonic model. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012,●●, ●●–●●.

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Section: Surprising Vicariant Patterns Of Relationshipsmentioning

confidence: 99%

Biogeographical patterns of plants in the Neotropics - dispersal rather than plate tectonics is most explanatory

Christenhusz

Chase

2012

Bot J Linn Soc

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“…In recent years, plastid DNA sequences have proved useful in orchid phylogenetics (e.g., Cameron, 2005;Van den Berg & al., 2005Carlsward & al., 2006bFischer & al., 2007). Among plastid DNA regions, the trnK intron and matK gene in particular have been a focus in plant phylogenetics (e.g., Hausner & al., 2006;Barthet & Hilu, 2007), including orchids (e.g., Gravendeel & al., 2001;Bytebier & al., 2007;Micheneau & al., 2008), and on that basis, this region was chosen for this study.…”

Section: Introductionmentioning

confidence: 99%

Phylogenetics and cytology of a pantropical orchid genusPolystachya(Polystachyinae, Vandeae, Orchidaceae): Evidence from plastid DNA sequence data

Russell

Samuel

Rupp

et al. 2010

TAXON

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The pantropical orchid genus Polystachya is the subject of ongoing taxonomic work. We inferred phylogenetic relationships in the genus using 5.3 kb of plastid DNA, for 83 out of ca. 240 species and 12 out of 15 sections, as well as five outgroup species. We also collected ploidy data using chromosome counts and genome size estimates. Bayesian and parsimony trees were congruent with each other and well resolved. Polystachya appears monophyletic based on current sampling, provided that the name P. neobenthamia is used instead of Neobenthamia gracilis for that species. The current sectional classification does not define monophyletic groups, but the present study can be used as the basis for a future sectional classification. Areas postulated as Pleistocene refugia for wet tropical forests in Africa also form centres of diversity for the genus. Biogeographical analyses using DIVA and Lagrange show an early radiation in eastern Africa, followed by separate radiations in eastern and western Africa. Subsequent dispersal from western to eastern Africa has occurred at a much higher rate than from east to west. Dispersal to the Neotropics occurred more than once, and one lineage has spread recently and rapidly throughout the tropics. Polyploidy has occurred several times during the diversification of the genus, most notably in association with the recent pantropical dispersal.

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“…30 species comprising sects. Calamaria , Humblotiorchis , and Bifalcula , but none of those relatives has a suberect rostellum ( [60] Gamisch et al, unpubl. data).…”

Section: Discussionmentioning

confidence: 99%

Histological and Micro-CT Evidence of Stigmatic Rostellum Receptivity Promoting Auto-Pollination in the Madagascan Orchid Bulbophyllum bicoloratum

et al. 2013

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BackgroundThe rostellum, a projecting part of the gynostemium in orchid flowers, separates the anther(s) from the stigma and thus commonly prevents auto-pollination. Nonetheless, as a modified (usually distal) portion of the median stigma lobe, the rostellum has been frequently invoked of having re-gained a stigmatic function in rare cases of orchid auto-pollination. Here it is shown that a newly discovered selfing variant of Madagascan Bulbophyllum bicoloratum has evolved a modified rostellum allowing the penetration of pollen tubes from in situ pollinia.MethodsGynostemium micro-morphology and anatomy of selfing and outcrossing variants of B . bicoloratum was studied by using light and scanning electron microscopy and histological sections. Pollen tube growth in the selfing variant was further observed via X-ray computed microtomography (micro-CT), providing 3D reconstructions of floral tissues at a micron scale.FindingsSelfing variants possess a suberect (‘displaced’) rostellum rather than the conventional, erect type. Very early in anthesis, the pollinia of selfers are released from the anther and slide down onto the suberect rostellum, where pollen tube growth preferentially occurs through the non-vascularized, i.e. rear (adaxial) and (semi-) lateral parts. This penetrated tissue is comprised of a thin layer of elongate and loosely arranged cells, embedded in stigmatic exudates, as also observed in the stigmatic cavity of both selfing and outcrossing variants.ConclusionsOur results provide the first solid evidence of a stigmatic function for the rostellum in orchid flowers, thereby demonstrating for the first time the feasibility of the micro-CT technique for accurately visualizing pollen tube growth in flowering plants. Rostellum receptivity in B . bicoloratum probably uniquely evolved as an adaptation for reproductive assurance from an outcrossing ancestor possessing an erect (non-receptive) rostellum. These findings open up new avenues in the investigation of an organ that apparently re-gained its ‘primordial function’ of being penetrated by pollen tubes.

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Evolution of resupination in Malagasy species of Bulbophyllum (Orchidaceae)

Cited by 40 publications

References 32 publications

Biogeographical patterns of plants in the Neotropics - dispersal rather than plate tectonics is most explanatory

Biogeographical patterns of plants in the Neotropics - dispersal rather than plate tectonics is most explanatory

Phylogenetics and cytology of a pantropical orchid genusPolystachya(Polystachyinae, Vandeae, Orchidaceae): Evidence from plastid DNA sequence data

Histological and Micro-CT Evidence of Stigmatic Rostellum Receptivity Promoting Auto-Pollination in the Madagascan Orchid Bulbophyllum bicoloratum

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