The origin of the bifurcating style in Asteraceae (Compositae)

Comparative anatomical and micromorphological analyses of root, stem, peduncle, leaf and inflorescence have been conducted on two Xeranthemum species, X. annuum and X. cylindraceum, by light microscopy (LM) and scanning electron microscopy (SEM). The main goal of the study was to examine the most important anatomical features and to find new valid taxonomic delimiting characters for the first time in both species. Regarding vegetative organs anatomy, the data obtained in this study indicated that both species possessed secondary tissues in the root, although these plants are annual. Also, stem anatomy was a typical of the Compositae family members, and anomocytic stomata type and dorsiventral leaf structure were present. On the involucral bracts surface crystals were noticeable, while highly developed multilayer sclerenchyma was present in the mesophyll. Palea anatomy was very similar to bract anatomy. Some floral features were as follows: lateral anther dehiscence, corolla composed of uniseriate epidermis and with a homogeneous parenchyma in the mesophyll, inferior ovary and anatropous ovule with basal placentation. The specific quantitative characters that were different between the examined species were emphasized. Some selected, well defined qualitative anatomical characters (e.g. shape of the young stem and peduncle cross-sections, type of glandular trichomes and cortical vascular bundles occurrence), on the basis of which the studied species were distinguishable, strengthen the taxonomy of the Xeranthemum genus and provide features for better identification of the taxa. This is the first study of the anatomy of Xeranthemum species and some of the characters found (secondary growth and dorsiventral leaves) points towards an adaptation of mesophilous ancestors to xeric habitats in Xeranthemum.

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“…7E-F). Lateral anther dehiscence was observed, although in Compositae introrse anthers are common (Katinas et al, 2016).…”

Section: Discussionmentioning

confidence: 97%

Anatomical characteristics of Xeranthemum L. (Compositae) species: taxonomical insights and evolution of life form

Gavrilović¹,

Rančić²,

Škundrić³

et al. 2019

PAK.J.BOT.

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“…However, much greater effort has been expended on elucidating the relationship between pollen and pollination (e.g., Banks and Rudall, 2016;Hesse, 2000;Osborn et al, 1991) than between stigma and pollination (Heslop-Harrison, 1992). The study of the diversity of stigmata related to various types of pollination (Basso-Alves et al, 2011;Jousselin and Kjellberg, 2001) and breeding systems (Katinas et al, 2016;Lora et al, 2011) is thus of great interest in general and for obligate mutualisms such as between fig trees (Ficus) and their agaonid pollinating wasps in particular (Galil and Eisikowitch, 1968).…”

Section: Introductionmentioning

confidence: 99%

Morphological diversity and function of the stigma in Ficus species (Moraceae)

et al. 2018

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The stigma plays several roles such as pollen hydration and selection, and pollen tube nutrition. In the Ficus-fig wasp mutualism, stigmata have an additional, almost unknown, function by representing a physical interface for both plant and wasp reproduction. We used light and electron microscopy to compare the detailed morphology of the stigmata of nine Ficus species of different sections and with different pollination modes and sexual expressions. Figs were collected at the stage when the stigmata were receptive for pollination. Stigmata in actively pollinated monoecious species have well developed papillae concentrated on the adaxial surface exposed towards the fig cavity. Conversely, the passively pollinated monoecious species have the whole surface of the stigmata covered by somewhat smaller papillae. In both actively and passively pollinated monoecious species these features are consistent, irrespective of style length. In all actively pollinated gynodioecious species, the stigmata of pistillate flowers were tubular or infundibuliform whereas in almost all actively pollinated monoecious species (except F. racemosa) the stigmata were filiform, with one branch or two asymmetric branches. In gynodioecious species the short-styled flowers in "male" figs show a limited receptive surface with small papillae, while the stigmata of long-styled flowers in "female" figs are covered by papillae that extend down the sides of the style, increasing the stigmatic surface. In actively pollinated species, stigmata are cohesive, forming a common surface for pollen tube germination (= synstigma). The synstigma arrangement was quite variable: lax, cohesive or very cohesive, with entanglement by stigmatic papillae and stylar trichomes. Entanglement by stylar trichomes is common in gynodioecious species. The synstigma arrangement did not correlate with phylogeny or breeding system. This study is the first to report a very loose synstigma in actively pollinated monoecious Ficus species. Our analyses revealed that, in Ficus, the synstigma is functionally analogous to an extra-gynoecial compitum. Comparative studies will be required to test further hypotheses about the evolutionary determinants of such variation.

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“…Version of Record TAXON 65 (6) • December 2016(6) • December : 1328(6) • December -1344 is a cephalioid (a very condensed botryoid/thyrsoid), from which the Asteraceae capitulum could have arisen (Pozner & al., 2012). Recently, Katinas & al. (2016) observed bilobed stigmas in Acicarpha tribuloides Juss., Boopis multicaulis Phil.…”

Section: Introductionmentioning

confidence: 95%

Insights into the phylogeny and evolutionary history of Calyceraceae

Denham

Zavala-Gallo

Johnson

et al. 2016

TAXON

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Calyceraceae is a small family with six traditionally recognized genera and 47 species from southern South America. Most species grow along the Andes (of both Argentina and Chile) and in arid regions of the Patagonian steppe. This family belongs to the well‐supported MGCA clade within Asterales, which includes Menyanthaceae+Goodeniaceae+Calyceraceae+ Asteraceae. Calyceraceae is monophyletic and sister to Asteraceae, one of the five largest families of angiosperms. Although Calyceraceae is clearly distinct as a family, its genera are not, and taxonomic revisionary effort has confirmed the lack of sharp boundaries among genera. We performed a phylogenetic analysis of Calyceraceae with a broad taxon sampling (41 of 47 species), and with sequence data from multiple regions from the nuclear (ITS) and plastid genomes (ycg6‐psbM, psbM‐trnD, trnS‐trnG, trnH‐psbA, trnD‐trnT) using maximum parsimony and Bayesian approaches. We aimed at identifying monophylectic groups, their putative morphological synapomorphies and their geographical distribution; we also estimated divergence times and examined chromosomes numbers in an evolutionary context. We obtained well‐resolved and strongly supported phylogenies that show Calyceraceae to be divided into two major clades with geographically structured subclades within each. Our results indicate that an early split within Calyceraceae occurred about 27.4 Ma, probably related to differential changes in chromosome numbers, which allowed the two lineages to evolve in sympatry. We found that major natural subgroups diverged 15–12 Ma, following the Early‐Miocene South Andes construction stage. Finally, the diversification of the extant species is probably associated to Andean orogeny and climate changes in the last 5–4 Myr. We recovered Acicarpha as monophyletic, while the remaining traditionally recognized genera of Calyceraceae are para‐ or polyphyletic. Most species of Moschopis are included in the Glutinose group, but M. monocephala is more closely related to some Calycera species. Calycera is divided into two clades; the Calycera group and the Pilose group. All species of Nastanthus are placed in a well‐supported main group with species of Gamocarpha and Boopis. Gamocarpha could be monophyletic after exclusion of G. dentata and G. angustifolia, but is nested within Nastanthus and Boopis species. Boopis is clearly polyphyletic with its species distributed in all main groups.

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The origin of the bifurcating style in Asteraceae (Compositae)

Abstract: These developments resulted in bifurcation in the styles of Asteraceae, with each branch face having a different function, and it is suggested here as a mechanism that promoted outcrossing, which in turn led to the great diversification in the family.

Cited by 21 publications

References 39 publications

Anatomical characteristics of Xeranthemum L. (Compositae) species: taxonomical insights and evolution of life form

Anatomical characteristics of Xeranthemum L. (Compositae) species: taxonomical insights and evolution of life form

Morphological diversity and function of the stigma in Ficus species (Moraceae)

Insights into the phylogeny and evolutionary history of Calyceraceae

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