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    Dark-centred umbels in Apiaceae: diversity, development and evolution
    (Oxford Univ Press, 2023) Classen-Bockhoff, Regine; Celep, Ferhat; Ajani, Yousef; Frenken, Lisa; Reuther, Kerstin; Dogan, Musa
    The wild carrot (Daucus carota) is famous for its dark flowers in the umbel centre. Several studies have been conducted to figure out their functional significance, but the evolution of the dark centre remains an enigma. In the present paper, we consider all known apioid species with dark-centred umbels to get a deeper understanding of their biology and evolution. Based on herbaria studies, literature and field work, we reconstructed the distribution area of 10 species (7 genera, 6 clades) of Apiaceae-Apioideae. To recognize homology of the dark structures, developmental studies were conducted in Artedia squamata and Echiophora trichophylla Field studies included architecture, flower morph distribution (andromonoecy) and flowering sequence within the plants, abundancy and behaviour of umbel visitors and preliminary manipulation experiments (removal/adding of dark structures). The dark structures are not homologous to each other. In the Daucus alliance, central flowers or umbellets are conspicuous, whereas in other species dark brush-like (A. squamata) or club-shaped structures (Dicyclophora persica, Echinophora trichophylla, Tordylium aegyptiacum, T. cappadocicum) develop from a naked receptacle. Species are andromonoecious, have a modular architecture and flower in multicyclic protandrous sequence. Among the many umbel visitors, beetles were the most abundant group. Only visitors found on umbels in both flowering phases were recognized as possible pollinators. Manipulation experiments indicated that the dark structures influence the behaviour of some, but not all umbel visitors. In Echinophora trichophylla, a massive gall infection was observed. It is evident that the dark structures evolved several times in parallel. The brush- and club-shaped structures are interpreted as the results of mutations affecting umbel development. Dark umbel centres are most likely stabilized by selection due to their general adaptive function. Their appearance in an area known as a hotspot of beetle pollination gives rise to the assumption that they may act as beetle marks. The wild carrot is famous for its red flower in the umbel centre. The function of this flower has been discussed since the time of Darwin. Experiments have led to the general conclusion that it is adaptive addressing at least part of the unspecialized visitors and pollinators. We show that Daucus carota is not the only species with dark umbel-centres. At least 10 apioid species from 7 genera and 6 clades have conspicuous dark structures in their umbels. It is evident that the morphologically diverse structures evolved in parallel. Some receptacle structures appear to be inherited mutations linked with the peculiarities of the umbel meristem. As the diversity centre of the species with dark-centred umbels is SW Asia, an area known as a hotspot of beetle pollination, we speculate that the dark umbel centres may act as beetle marks not only but primarily attracting beetles as pollinators.
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    Öğe
    Flower-like meristem conditions and spatial constraints shape architecture of floral pseudanthia in Apioideae
    (Bmc, 2022) Baczynski, Jakub; Celep, Ferhat; Spalik, Krzysztof; Classen-Bockhoff, Regine
    Background: Pseudanthia are multiflowered units that resemble single flowers, frequently by association with pseudocorollas formed by enlarged peripheral florets (ray flowers). Such resemblance is not only superficial, because numerous pseudanthia originate from peculiar reproductive meristems with flower-like characteristics, i.e. floral unit meristems (FUMs). Complex FUM-derived pseudanthia with ray flowers are especially common in Apiaceae, but our knowledge about their patterning is limited. In this paper, we aimed to investigate both the genetic and morphological basis of their development. Results: We analysed umbel morphogenesis with SEM in six species representing four clades of Apiaceae subfamily Apioideae with independently acquired floral pseudanthia. Additionally, using in situ hybridization, we investigated expression patterns of LEAFY (LFY), UNUSUAL FLORAL ORGANS (UFO), and CYCLOIDEA (CYC) during umbel development in carrot (Daucus carota subsp. carota). Here, we show that initial differences in size and shape of umbel meristems influence the position of ray flower formation, whereas an interplay between peripheral promotion and spatial constraints in umbellet meristems take part in the establishment of specific patterns of zygomorphy in ray flowers of Apiaceae. This space-dependent patterning results from flower-like morphogenetic traits of the umbel which are also visible at the molecular level. Transcripts of DcLFY are uniformly distributed in the incipient umbel, umbellet and flower meristems, while DcCYC shows divergent expression in central and peripheral florets. Conclusions: Our results indicate that umbels develop from determinate reproductive meristems with flower-like characteristics, which supports their recognition as floral units. The great architectural diversity and complexity of pseudanthia in Apiaceae can be explained by the unique conditions of FUMs-an interplay between expression of regulatory genes, specific spatio-temporal ontogenetic constraints and morphogenetic gradients arising during expansion and repetitive fractionation. Alongside Asteraceae, umbellifers constitute an interesting model for investigation of patterning in complex pseudanthia.
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    Öğe
    Pollination Ecology, Specialization, and Genetic Isolation in Sympatric Bee-PollinatedSalvia(Lamiaceae)
    (UNIV CHICAGO PRESS, 2020) Celep, Ferhat; Atalay, Zeynep; Dikmen, Fatih; Dogan, Musa; Sytsma, Kenneth J.; Classen-Bockhoff, Regine
    Premise of research. Previous pollination ecology studies ofSalviahave shown that there is low specialization for certain subgroups of bees and that pollinator number varies with species and locality. We studied 12Salviaspecies (three clades with different corolla morphologies and staminal lever mechanisms) that in part co-occur and coflower to examine prezygotic isolation mechanisms and the degree of specialization versus generalization in pollination ecology. Methodology. Pollinators were identified using field observations, photos, and related literature across three sites in Turkey. Video documentation of the visitation rate and the site of pollen placement on the pollinator body, morphometric measurements between flowers and pollinators, flowering time, flower color, handling time, and stigma contact ratio were analyzed. Plant-pollinator networks were constructed. Pivotal results. Mechanical, phenological, and ethological isolation occurs among sympatricSalviaspecies. A morphological fit is evident between flower tube length and the proboscis length of the main pollinators. Pollinator networks indicate that most species are ecological generalists and that only a few are specialists. Conclusions. The 12Salviaspecies, though phenotypically and functionally specialized by their zygomorphic, bilabiate flowers and bee-pollination syndrome, differ in the degree of their ecological specialization. Most of the sympatricSalviaspecies tend to be ecologically generalized, with two or more main pollinators and a few additional secondary pollinators, while a fewSalviaspecies are clearly specialized. Some floral traits (e.g., flower color, morphology, size, corolla tube length and width of the corolla tube entrance, type and size of the staminal lever mechanism, small numbers of flowers in the inflorescence), a short flowering time, and a small population size appear to be correlated with the degree of ecological specialization.