Fossil pollen from early Palaeogene sediments in western India provides phylogenetic insights into divergence history and pollen character evolution in the pantropical family Ebenaceae

Many plant families lack substantive fossil records, limiting our understanding of their origin and evolution. The abundance and preservation potential of pollen through geological time have helped to overcome such limitations and have provided reliable fossils for reconstructing biogeographical history and character evolution in many angiosperm families. Here, using scanning electron microscopy, we identified six Ebenaceae-type fossil pollen grains from early Palaeogene sediments of western India. Phenetic and phylogenetic analyses using pollen characters of fossil and extant taxa reavealed affinities of these fossils to three genera of Ebenaceae (Euclea, Royena and Diospyros). Furthermore, our divergence dating analysis using these fossils as priors suggested a Gondwanan origin for the family during the mid-Cretaceous [c. 107 Mya, 95% highest posterior density (HPD): 100–112 Mya] and supports the boreotropical and ‘out of India’ dispersal hypotheses as the most probable explanations for the present global distribution of the family. The study also supports the dispersal of the family into India, from Africa, through the Kohistan–Ladakh Arc during the Palaeocene. Finally, comparative phylogenetic analyses suggest significant synapomorphic and phylogenetic signals for a few selected pollen characters in Ebenaceae. Our findings have important implications for understanding the biogeography and evolution of the highly diverse and ecologically and economically important family Ebenaceae.

Unravelling the Habenaria repens (Orchidaceae) complex in Brazil: a biosystematic and molecular phylogenetic approach

Habenaria repens (Orchidaceae) represents a species complex distributed from the southern USA to northern Argentina, including several morphological variants, here referred to as morphotypes. To investigate and clarify the morphological and genetic relationships between these morphotypes and resolve the taxonomy of the complex, we applied a biosystematic multi-population approach using molecular phylogenetic, morphometric and population genetics analyses in the group. We sampled 31 (phylogenetic analyses) and 20 (morphometric and microsatellite analyses) populations of Habenaria aranifera and H. repens from Brazil and the USA, including six morphotypes of H. repens. Bayesian and maximum parsimony phylogenetic analyses of nuclear ribosomal (ITS and ETS) and plastid (matK, trnK and rps16-trnK) markers revealed that the complex is polyphyletic, subdivided into three distantly related clades. Population genetic analyses using microsatellites showed a remarkably similar structure to the phylogenetic analyses, but both were different from the morphometric analyses of floral characters, indicating cases of diversification and convergence, probably due to pollination processes. Habenaria aranifera is embedded in a paraphyletic and polymorphic H. repens with a broad geographical distribution and other attributes of an ochlospecies, probably constituting a progenitor–derivative pair. Our results support the recognition of H. aranifera, H. repens and three or four new species.

A leaky dimorphic sexual system and breeding system characterize a successful island colonist: the reproductive biology of Plocama pendula (Rubiaceae)

Island plants provide special opportunities for the study of evolution and ecology. In field and greenhouse studies we characterized a model reproductive system for Plocama pendula, endemic to the Canary Islands. This species has a complicated and not immediately obvious reproductive system. Pollination is biotic, and all flowers are morphologically hermaphroditic, but half of the plants characteristically bear flowers with nectar, pistils with reflexed stigmatic lobes and pollen-less anthers (i.e. they are functionally female flowers). The other half bear nectar-less flowers with abundant pollen and full-sized pistils that mostly have un-reflexed stigmatic lobes (i.e. they are hermaphroditic flowers functioning mostly as males). However, experiments show these pollen-bearing flowers to be self-compatible. Thus, the functionally male flowers have a breeding system that allows selfing in limited circumstances, but the functionally male flowers produce far fewer fruits than do functionally female flowers. With morphologically gynodioecious, functionally largely dioecious flowers, sometimes capable of selfing, the reproductive system of this species could be labelled as ‘leaky’ in many respects. Thus, we propose that P. pendula has colonized new habitats and persists in substantial populations at least in part because it manifests a reproductive system that is a model for successfully balancing the often-conflicting evolutionary demands of colonization, establishment and persistence.

Tracing the origins of hybrids through history: monstrous cultivars and Napoléon Bonaparte’s exiled paper daisies (Asteraceae; Gnaphalieae)

Golden everlasting paper daisies (Xerochrysum, Gnaphalieae, Asteraceae) were some of the earliest Australian native plants to be cultivated in Europe. Reputedly a favourite of Napoléon Bonaparte and Empress Joséphine, X. bracteatum is thought to have been introduced to the island of St Helena in the South Atlantic during Napoléon’s exile there. Colourful cultivars were developed in the 1850s, and there is a widely held view that these were produced by crossing Xerochrysum with African or Asian Helichrysum spp. Recent molecular phylogenetic analyses and subtribal classification of Gnaphalieae cast doubt on this idea. Using single-nucleotide polymorphism (SNP) data, we looked for evidence of gene flow between modern cultivars, naturalized paper daisies from St Helena and four Xerochrysum spp. recorded in Europe in the 1800s. There was strong support for gene flow between cultivars and X. macranthum. Paper daisies from St Helena were genotypically congruent with X. bracteatum and showed no indications of ancestry from other species or from the cultivars, consistent with the continuous occurrence of naturalized paper daisies introduced by Joséphine and Napoléon. We also present new evidence for the origin of colourful Xerochrysum cultivars and hybridization of congeners in Europe from Australian collections.

What can the phylogeny of class I KNOX genes and their expression patterns in land plants tell us about the evolution of shoot development?

KNOX genes encode transcription factors (TFs), several of which act non-cell-autonomously. KNOX genes evolved in algae, and two classes, class I KNOX and class II KNOX genes, were already present in charophytes. In tracheophytes, class I KNOX genes are expressed in shoot apical meristems (SAMs) and thought to inhibit cell differentiation, whereas class II KNOX genes are expressed in mature organs regulating differentiation. In this review, we summarize the data available on gene families and expression patterns of class I and class II KNOX genes in embryophytes. The expression patterns of class I KNOX genes should be seen in the context of SAM structure and of leaf primordium development where the inhibition of cell differentiation needs to be lifted. Although the SAMs of angiosperms and gnetophytes almost always belong to the duplex type, several other types are distributed in gymnosperms, ferns, lycopods and bryophytes. KNOX gene families remained small (maximally five genes) in the representatives of bryophytes, lycopods and ferns examined thus far; however, they expanded to some extent in gymnosperms and, independently and much more strongly, in angiosperms. The growing sophistication of mechanisms to repress and re-induce class KNOX I expression played a major role in the evolution of leaf shape.

Resolving generic limits in Cyperaceae tribe Abildgaardieae using targeted sequencing

Morphological characterizations of genera in Cyperaceae tribe Abildgaardieae have been highly problematic and the subject of much debate. Earlier molecular phylogenetic studies based on Sanger sequencing and a limited sampling have indicated that several generic circumscriptions are not monophyletic. Here, we provide the first phylogenetic hypothesis for Abildgaardieae using targeted sequencing data obtained with the Angiosperms353 enrichment panel for 50 species. We test whether recent taxonomic decisions made based on Sanger sequencing data are validated by our targeted sequencing data. Our results support subsuming the small African genus Nemum into the large genus Bulbostylis and subsuming the monotypic genus Crosslandia into the diverse genus Fimbristylis. Also, our results support the recent publication of the new genus Zulustylis for two African species previously placed in Fimbristylis. Furthermore, we investigate the phylogenetic placement of recently described tropical Australian endemic species of Actinoschoenus, which are recognized here as the new morphologically cryptic genus Scleroschoenus. Based on our phylogenetic hypothesis and supported by morphological data, we recognize the genus Abildgaardia. The placement in Abildgaardieae of two monotypic genera Nelmesia and Trichoschoenus, only known from the type collections from the Democratic Republic of Congo and Madagascar, respectively, are also discussed. New combinations and lectotypifications are made in Abildgaardia, Actinoschoenus, Arthrostylis and Scleroschoenus.