INDEPENDENT ORIGINATION OF FLORAL ZYGOMORPHY, A PREDICTED ADAPTIVE RESPONSE TO POLLINATORS: DEVELOPMENTAL AND GENETIC MECHANISMS

Observations of floral development indicate that floral organ initiation in pentapetalous flowers more commonly results in a medially positioned abaxial petal (MAB) than in a medially positioned adaxial petal (MAD), where the medial plane is defined by the stem and the bract during early floral development. It was proposed that the dominant MAB petal initiation might impose a developmental constraint that leads to the evolution of limited patterns of floral zygomorphy in Asteridae, a family in which the floral zygomorphy develops along the medial plane and results in a central ventral (CV) petal in mature flowers. Here, I investigate whether the pattern of floral organ initiation may limit patterns of floral zygomorphy to evolve in pentapetalous angiosperms. I analyzed floral diagrams representing 405 species in 330 genera of pentapetalous angiosperms to reconstruct the evolution of floral organ initiation and the evolution of developmental processes that give rise to floral zygomorphy on a phylogenetic framework. Results indicate that MAB petal initiation is the most common; it occupies 86.2% of diversity and represents the ancestral state of floral organ initiation in pentapetalous angiosperms. The MAD petal initiation evolved 28 times independently from the ancestral MAB petal initiation. Among the 34 independent originations of floral zygomorphy, 76.5% of these clades represent MAB petal initiation, among which only 47% of the clades result a CV petal in mature flowers. The discrepancy is explained by the existence of developmental processes that result in floral zygomorphy along oblique planes of floral symmetry in addition to along the medial plane. Findings suggest that although the early floral organ initiation plays a constraining role to the evolution of patterns of floral zygomorphy, the constraint diverges along phylogenetically distantly related groups that allow the independent originations of floral zygomorphy through distinct development processes in pentapetalous angiosperms. In additional study, the butterfly-like flowers of Schizanthus are adapted to pollination by bees, hummingbirds, and moths. I investigated the genetic basis of the zygomorphic corolla, for which development is key to the explosive pollen release mechanism found in the species of Schizanthus adapted to bee pollinators. I examined differential gene expression profiles across the zygomorphic corolla of Schizanthus pinnatus, a bee-pollinated species, by analyzing RNA transcriptome sequencing (RNA- seq). Data indicated that CYC2 is not expressed in the zygomorphic corolla of Sc. pinnatus, suggesting CYC2 is not involved in the development of floral zygomorphy in Schizanthus (Solanaceae). The data also indicated that a number of genes are differentially expressed across the corolla

First occurrence of mastixioid (Cornaceae) fossil in India and its biogeographic implications

Mastixioids in the family Cornaceae, are presently native only in limited areas of Asia, they have rich fossil fruit record in Cenozoic sediments of Europe and North America, but unfortunately none have been reported from Cenozoic sediments of India and Asia until now. Here, we report the occurrence of leaf remains (both impression and compression) along with carbonised fruits, resembling morphologically and anatomically those of the extant endemic species Mastixia arborea C.B. Clarke. Our materials were recovered from the middle Miocene to early Pleistocene Siwalik sediments exposed around West Kameng and Papumpare districts in Arunachal Pradesh, eastern Himalaya. These new fossil materials confirm the existence of Mastixia in the Miocene-Pleistocene Siwalik forests in India. At present the modern analogue does not grow in the eastern Himalaya and is endemic to the tropical evergreen forests of the Western Ghats, situated at the same palaeolatitude as the fossil locality. Extinction from the entire eastern Himalaya and probable movement of this taxon to the Western Ghats is likely due to climate change in the area, related to the Himalayan Orogeny during Miocene–Pleistocene times. The disappearance of Mastixia from this area may be related to the gradual intensification of rainfall seasonality since the late Miocene. The recovery of this species and our earlier-described evergreen taxa from the same Siwalik time (Mio-Pleistocene), suggest the existence of tropical, warm and humid climatic conditions during the period of deposition. The leaf and fruit remains are here described as new species, namely Mastixia asiatica Khan, Bera M et Bera S, sp. nov. and Mastixia siwalika Khan, Bera M et Bera S, sp. nov. respectively. This report documents the first fossil record of Mastixia leaf remains using both macro and micromorphological characters. We also review the historical phytogeography, and highlight the phytogeographic implication of, the mastixioids

Multifunctional Bracts in the Dove Tree Davidia involucrata (Nyssaceae:Cornales)

Although there has been much experimental work on floral traits that are under selection from mutualists and antagonists, selection by abiotic environmental factors on flowers has been largely ignored. Here we test whether pollen susceptibility to rain damage could have played a role in the evolution of the reproductive architecture of Davidia involucrata, an endemic in the mountains of western China. Flowers in this tree species lack a perianth and are arranged in capitula surrounded by large (up to 10 cm#5 cm) bracts that at anthesis turn from green to white, losing their photosynthetic capability. Flowers are nectarless, and pollen grains are presented on the recurved anther walls for 5–7 days. Flower visitors, and likely pollinators, were mainly pollen-collecting bees from the genera Apis, Xylocopa, Halictus, and Lasioglossum. Capitula with natural or white paper bracts attracted significantly more bees per hour than capitula that had their bracts removed or replaced by green paper. Experimental immersion of pollen grains in water resulted in rapid loss of viability, and capitula with bracts lost less pollen to rain than did capitula that had their bracts removed, suggesting that the bracts protect the pollen from rain damage as well as attracting pollinators

A new striking and critically endangered species of Nasa (Loasaceae, Cornales) from North Peru

Nasa angeldiazioides sp. nov. is described and illustrated. The species is restricted to two forest remnants on the western slope of the northern Peruvian Andes (Dept. Lambayeque) where it is found in the undergrowth of primary forest. The new taxon shows a unique leaf morphology in the family Loasaceae. Molecular and morphological data show that the new species belongs to the Nasa triphylla group. Since the relic forests of the north-western Andes are increasingly threatened by the effects of climate change, i.e. droughts and wildfires, the new species already faces imminent extinction

Functional distinctiveness of major plant lineages

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106060/1/jec12208.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106060/2/jec12208-sup-0001-Supp_Info.pd

Progress and problems in the assessment of flower morphology in higher-level systematics

Floral features used for characterization of higher-level angiosperm taxa (families, orders, and above) are assessed following a comparison of earlier (precladistic/premolecular) and current classifications. Cronquist (An integrated system of classification of flowering plants. Columbia University Press, New York, 1981) and APG (Angiosperm Phylogeny Group) (Bot J Linn Soc 161:105-121, 2009) were mainly used as the basis for this comparison. Although current circumscriptions of taxonomic groups (clades) are largely based on molecular markers, it is also important to morphologically characterize these new groups, as, in many cases, they are completely novel assemblages, especially at the level of orders and above. Features used in precladistic/premolecular classifications are often much more evolutionarily plastic than earlier assumed. A number of earlier neglected but potentially useful features at higher levels are discussed based on our own and other recent studies. As certain features tend to evolve repeatedly in a clade, it appears that apomorphic features in the strict sense are less helpful to characterize larger clades than earlier assumed, and rather apomorphic tendencies of features are more useful at this leve