Multiple independent origins of auto-pollination in tropical orchids (Bulbophyllum) in light of the hypothesis of selfing as an evolutionary dead end

Background: The transition from outcrossing to selfing has long been portrayed as an ‘evolutionary dead end because, first, reversals are unlikely and, second, selfing lineages suffer from higher rates of extinction owing to a reduced potential for adaptation and the accumulation of deleterious mutations. We tested these two predictions in a clade of Madagascan Bulbophyllum orchids (30 spp.), including eight species where auto-pollinating morphs (i.e., selfers, without a ‘rostellum) co-exist with their pollinator-dependent conspecifics (i.e., outcrossers, possessing a rostellum). Specifically, we addressed this issue on the basis of a time-calibrated phylogeny by means of ancestral character reconstructions and within the state-dependent evolution framework of BiSSE (Binary State Speciation and Extinction), which allowed jointly estimating rates of transition, speciation, and extinction between outcrossing and selfing. Results: The eight species capable of selfing occurred in scattered positions across the phylogeny, with two likely originating in the Pliocene (ca. 4.43.1 Ma), one in the Early Pleistocene (ca. 2.4 Ma), and five since the mid-Pleistocene (ca. 1.3 Ma). We infer that this scattered phylogenetic distribution of selfing is best described by models including up to eight independent outcrossing-to-selfing transitions and very low rates of speciation (and either moderate or zero rates of extinction) associated with selfing. Conclusions: The frequent and irreversible outcrossing-to-selfing transitions in Madagascan Bulbophyllum are clearly congruent with the first prediction of the dead end hypothesis. The inability of our study to conclusively reject or support the likewise predicted higher extinction rate in selfing lineages might be explained by a combination of methodological limitations (low statistical power of our BiSSE approach to reliably estimate extinction in small-sized trees) and evolutionary processes (insufficient time elapsed for selfers to go extinct). We suggest that, in these tropical orchids, a simple genetic basis of selfing (via loss of the ‘rostellum) is needed to explain the strikingly recurrent transitions to selfing, perhaps reflecting rapid response to parallel and novel selective environments over Late Quaternary ( 1.3 Ma) time scales.P20726-B03P17124-B0(VLID)243455

Julije Klović and the Medicis

L\u27autrice riporta nuovi dati riguardanti Giulio Clovio in relazione con Firenze. Gia nel 1544 il Duca Cosimo I\u27 cercava di prenderlo in servizio, ma cio gli riusci appena nel 1551, alorche il cardinale Alessandro Farnese venne da Roma a Firenze. Nel 1552 Vincenzo Borghini riferisce che il Clovio sta lavorando per Cosimo I\u27, e il 22/6/1553 fu assegnato all\u27artista un appartamento a Palazzo Pitti. Egli vi dimora fino all\u2711/11 di quell\u27anno stesso. Nel frattempo egli gia dipinse la «Crocifissione» (segnata e datata 1553) e la »Pieta«. Si credeva finora che queste due miniature, insieme a un «Autoritratto» piu tardo, fossero le uniche opere nate a Firenze. L\u27autrice, invece, scopri che nel primo inventario della Galleria degli Uffizi (1589) sono registrate sette opere e grazie alla descrizione data, ella le identifica come conservate fino ad oggi: »S. Giovanni Battista«, »Testa di donna« (invero dell\u27Annunziata) e »ll ratto di Gaminede« nel quale la figura principale e fatta secondo il disegno di Michelangelo, mentre le aggiunte del Clovio sono la figura del cane e lo sfondo del paesaggio. Il «Ritratto di Eleonora di Toledo» e andato perduto, ma lo conosciamo dala copia di Daniel Froeschel della fine del XVI secolo. Analizzando e valutando le miniature nominate del Clovio, I\u27autrice rileva che il loro sostrato simboleggiante rispecchia fedelmente la delicata cultura della cerchia farnesiana.Autorica donosi nove podatke o odnosu Julija Klovića sa Firenzom. Već godine 1544. nastojao je vojvoda Cosimo I. da ga dobije u svoju službu, ali mu je to pošlo za rukom tek 1551, kad je kardinal Alessando Farnese došao iz Rima u Firenzu. Vincenzo Borghini izvještava 1552. da Klović radi za Cosima I., a 22. VI. 1553. umjetnik je dobio stan u palači Pitti. Tu se nalazi do 11. XI. iste godine. Do toga je datuma već naslikao »Raspeće« (signirano i datirano 1553) i »Oplakivanje«. Do sada se vjerovalo da su te dvije minijature, uz jedan kasniji «Autoportret», jedini radovi nastali u Firenzi. Autorica međutim otkriva u prvom inventaru galerije Uffizi (1589) zabilježeno sedam radova i zahvaljujući njihovu opisu identificira ih kao do danas sačuvane: »Sv. Krstitelj», »Glava žene« (zapravo Bogorodica iz Navještenja) i »Otmicu Ganimeda» na kojoj je glavni lik rađen prema Michelangelovu crtežu, dok su Klovićev dodatak lik psa i pejzažna pozadina. »Portret Eleonore di Toledo« je izgubljen, ali izgled mu je poznat po kopiji Daniela Froeschela iz konca XVI. stoljeća. Analizirajući i vrednujući pomenute Klovićeve minijature, autorica istiće da njihov simbolski supstrat vjerno ilustrira profinjenu kulturu farnezijanske sredine.The author presents nw data on Julije Klović\u27s relationship with Florence. As early as 1554 Duke Cosimo I tried to draw Klović into his service, but it took him until 1551 to succeed, when Cardinal Alessandro Farnese came to Florence from Rome. Vincenzo Borghini reports in 1552 that Klović was working for the Duke, and on 22 June 1553 he was provided with accomodation in the Pitti Palace. Here he remained until 11 November of the same year. By that date he had already painted the »Crucifix« (signed and dated 1553) and »Mourning«; until now it was believed that these two miniatures, along with a later »Self-Portrait«, were the only works that originated in Florence. The author discloses that there were seven works listed in the first inventory of Uffizi Gallery (1589) and thanks to their descriptions she identifies them as existing today; »St. John the Baptist«, »The Head of a Woman« (actually the Madonna from the Annuciation) and the »Rape of Ganvmede« where the central figure is a replica of Michelangelo\u27s drawing, while Klović\u27s is the addition of the figure of a dog and the landscape in the background. The »Portrait of Eleonor di Toledo« has been lost, but its appearance is known to us through a copy by Daniel Froeschel from the late 16th century. The author stresses, through her analvsis and evaluation of these miniatures, that their symbolic substrate is a faithful illustration of the refined culture of the environment of the Farnese family

Histological and micro-CT evidence of stigmatic rostellum receptivity promoting auto-pollination in the Madagascan orchid Bulbophyllum bicoloratum

Background: The 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. Methods: Gynostemium 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. Findings: Selfing 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. Conclusions: Our 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.P20726-B03P17124-B0(VLID)170467

Evolution of East Asias Arcto-Tertiary relict Euptelea (Eupteleaceae) shaped by Late Neogene vicariance and Quaternary climate change

Background: The evolutionary origin and historical demography of extant Arcto-Tertiary forest species in East Asia is still poorly understood. Here, we reconstructed the evolutionary and population demographic history of the two extant Euptelea species in China (E. pleiosperma) and Japan (E. polyandra). Chloroplast/nuclear DNA sequences and microsatellite loci were obtained from 36 Euptelea populations to explore molecular structure and diversity in relation to past and present distributions based on ecological niche modelling (ENM). Time-calibrated phylogenetic/phylogeographic inferences and niche-identity tests were used to infer the historical process of lineage formation. Results: Euptelea pleiosperma diverged from E. polyandra around the Late Miocene and experienced significant ecological differentiation. A near-simultaneous diversification of six phylogroups occurred during the mid-to-late Pliocene, in response to the abrupt uplift of the eastern Tibetan Plateau and an increasingly cooler and drier climate. Populations of E. pleiosperma seem to have been mostly stationary through the last glacial cycles, while those of E. polyandra reflect more recent climate-induced cycles of range contraction and expansion. Conclusions: Our results illustrate how Late Neogene climatic/tectonic changes promoted speciation and lineage diversification in East Asias Tertiary relict flora. They also demonstrate for the first time a greater variation in such species responses to glacial cycles in Japan when compared to congeners in China.(VLID)193287

ENM

Potential distributions of the four major lineages of Bulbophyllum from the Neotropics, Africa, Madagascar and the Asia-Pacific region at the present (c. 1950–2000) and at the Last Glacial Maximum (CCSM and MIROC

Data from: Clade-age-dependent diversification under high species turnover shapes species richness disparities among tropical rainforest lineages of Bulbophyllum (Orchidaceae)

Background: Tropical rainforests (TRFs) harbour almost half of the world’s vascular plant species diversity while covering only about 6–7% of land. However, why species richness varies amongst the Earth’s major TRF regions remains poorly understood. Here we investigate the evolutionary processes shaping continental species richness disparities of the pantropical, epiphytic and mostly TRF-dwelling orchid genus Bulbophyllum (c. 1,948 spp. in total; Asia-Pacific region: c. 1,564 spp.; Madagascar: 210; Africa: 80; Neotropics: 94) using diversification analyses based on a time-calibrated molecular phylogeny, coupled with ecological niche modelling (ENM) of geographic distributions under present and past (Last Glacial Maximum) conditions. Results: Our results suggest an early-to-late Miocene scenario of ‘out-of-Asia-Pacific’ origin and progressive, dispersal-mediated diversification in Madagascar, Africa and the Neotropics, respectively. Species richness disparities amongst these four TRF lineages are best explained by a time-for-speciation effect rather than differences in net diversification or diversity-dependent diversification due to present or past spatial-bioclimatic limits. All four lineages of experienced dramatic range expansions during the LGM, which conflicts with the common notion that TRFs mostly fragmented/contracted during glacial periods. Conclusions: Most species of at least the Madagascan, African and Neotropical lineages originated during the Quaternary. Their diversification under high species turnover (i.e. high rates of speciation and extinction) might relate to climate-induced range fluctuations during this time period combined with various intrinsic features commonly invoked to foster rapid population turnover in tropical orchids (e.g., epiphytism, specialization on pollinators and mycorrhizal fungi, dispersal by wind). Further (e.g., phylogenomic and ecological) research within each Bulbophyllum lineage but also other pantropical TRF taxa is required to provide a better understanding of how evolutionary processes as well as past and current environmental conditions drive tropical biodiversity and account for regional differences in species richness patterns on a global scale

Clade-age-dependent diversification under high species turnover shapes species richness disparities among tropical rainforest lineages of Bulbophyllum (Orchidaceae)

Abstract Background Tropical rainforests (TRFs) harbour almost half of the world’s vascular plant species diversity while covering only about 6–7% of land. However, why species richness varies amongst the Earth’s major TRF regions remains poorly understood. Here we investigate the evolutionary processes shaping continental species richness disparities of the pantropical, epiphytic and mostly TRF-dwelling orchid mega-genus Bulbophyllum (c. 1948 spp. in total) using diversification analyses based on a time-calibrated molecular phylogeny (including c. 45–50% spp. each from Madagascar, Africa, Neotropics, and 8.4% from the Asia-Pacific region), coupled with ecological niche modelling (ENM) of geographic distributions under present and past (Last Glacial Maximum; LGM) conditions. Results Our results suggest an early-to-late Miocene scenario of ‘out-of-Asia-Pacific’ origin and progressive, dispersal-mediated diversification in Madagascar, Africa and the Neotropics, respectively. Species richness disparities amongst these four TRF lineages are best explained by a time-for-speciation (i.e. clade age) effect rather than differences in net diversification or diversity-dependent diversification due to present or past spatial-bioclimatic limits. For each well-sampled lineage (Madagascar, Africa, Neotropics), we inferred high rates of speciation and extinction over time (i.e. high species turnover), yet with the origin of most extant species falling into the Quaternary. In contrast to predictions of classical ‘glacial refuge’ theories, all four lineages experienced dramatic range expansions during the LGM. Conclusions As the Madagascan, African and Neotropical lineages display constant-rate evolution since their origin (early-to-mid-Miocene), Quaternary environmental change might be a less important cause of their high species turnover than intrinsic features generally conferring rapid population turnover in tropical orchids (e.g., epiphytism, specialization on pollinators and mycorrhizal fungi, wind dispersal). Nonetheless, climate-induced range fluctuations during the Quaternary could still have played an influential role in the origination and extinction of Bulbophyllum species in those three, if not in all four TRF regions

ITS_Bulbophyllum_global_2019

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