Just add water: Rainfall-induced anther closure and color change in Ripariosida hermaphrodita (Malvaceae).

Anther opening has commonly been thought of as unidirectional, but reports of anthers closing in response to rainfall show this is not the case. In some species, anther closure can protect pollen from degrading or washing away, thus possibly enhancing male fitness. Similarly, although floral color is often presumed to be static, numerous floral parts may change color during blooming. These color changes primarily occur in response to pollination or aging, thus potentially increasing pollination efficiency by directing floral visitors to recently opened, unpollinated flowers. Daily observations of 364 Ripariosida hermaphrodita flowers from seven individuals showed that anthers that were purple, open, and shedding pollen became beige colored and tightly closed after rainfall. These findings were further supported by observations of plants exposed to simulated rainfall in a greenhouse and time-lapse photography of flowers misted with water. To our knowledge, our work represents the first report of anther closure in response to rain in Malvaceae and the first report of floral color change induced by rainfall.

Out of Madagascar, repeatedly: The phylogenetics and biogeography of Dombeyoideae (Malvaceae s.l.).

Dispersals have been shown to be critical to the evolution of the long isolated but megadiverse flora of Madagascar and the surrounding islands of the western Indian Ocean, but we are just beginning to understand the directionality of these dispersals. With more than half of its species occurring in the western Indian Ocean region (WIOR), the paleotropical subfamily Dombeyoideae provides a particularly useful case study through which to better understand the biogeography of the WIOR, and yet its biogeography is poorly understood. Here we sampled six molecular markers from all 20 genera in the Dombeyoideae to reconstruct the most complete phylogeny to date for the subfamily. From this, divergence times, calibrated with three fossils (two dombeyoid, one malvoid), and ancestral range estimations were hypothesized. Biogeographic stochastic mapping (BSM) analyses on the maximum clade credibility tree were completed and compared to BSM analyses on 1,000 trees randomly sampled from the posterior distribution of trees resulting from the dating analysis. We found the Dombeyoideae crown node diverged ca. 53 million years ago out of a broad ancestral range involving all three major areas of its distribution: Madagascar, Africa, and Asia. The majority of diversification and dispersals in the subfamily occurred within the last ca. 10 million years, mostly from the Pliocene onwards. There were roughly five dispersals from Madagascar to Africa (and only one in reverse), at least six from Madagascar to surrounding islands of the WIOR (Mascarenes and Comoros), and one dispersal from Madagascar to Asia (and ca. 1 in reverse). Other long-distance dispersals included one from Africa to St. Helena and one from Africa to Australasia, both from within the most widespread clade, the Cheirolaena & allies clade, and one dispersal from Asia to Africa. Critically, the Dombeyoideae provide strong evidence for considering the island of Madagascar as a source for the colonization of continents, as well as the surrounding islands of the WIOR. Furthermore, narrow sympatry was a key process in the evolution of the subfamily, particularly in Madagascar and the Mascarenes.

Polyploidy on islands - concerted evolution and gene loss amid chromosomal stasis.

BACKGROUND AND AIMS: Polyploidy is an important process that often generates genomic diversity within lineages, but it can also cause changes that result in loss of genomic material. Island lineages, while often polyploid, typically show chromosomal stasis but have not been investigated in detail regarding smaller-scale gene loss. Our aim was to investigate post-polyploidization genome dynamics in a chromosomally stable lineage of Malvaceae endemic to New Zealand. METHODS: We determined chromosome numbers and used fluorescence in situ hybridization to localize 18S and 5S rDNA. Gene sequencing of 18S rDNA, the internal transcribed spacers (ITS) with intervening 5.8S rDNA, and a low-copy nuclear gene, GBSSI-1, was undertaken to determine if gene loss occurred in the New Zealand lineage following polyploidy. KEY RESULTS: The chromosome number for all species investigated was 2n = 42, with the first published report for the monotypic Australian genus Asterotrichion. The five species investigated all had two 5S rDNA signals localized interstitially on the long arm of one of the largest chromosome pairs. All species, except Plagianthus regius, had two 18S rDNA signals localized proximally on the short arm of one of the smallest chromosome pairs. Plagianthus regius had two additional 18S rDNA signals on a separate chromosome, giving a total of four. Sequencing of nuclear ribosomal 18S rDNA and the ITS cistron indicated loss of historical ribosomal repeats. Phylogenetic analysis of a low-copy nuclear gene, GBSSI-1, indicated that some lineages maintained three copies of the locus, while others have lost one or two copies. CONCLUSIONS: Although island endemic lineages show chromosomal stasis, with no additional changes in chromosome number, they may undergo smaller-scale processes of gene loss and concerted evolution ultimately leading to further genome restructuring and downsizing.

A Malvaceae mystery: A mallow maelstrom of genome multiplications and maybe misleading methods?

Previous research suggests that Gossypium has undergone a 5- to 6-fold multiplication following its divergence from Theobroma. However, the number of events, or where they occurred in the Malvaceae phylogeny remains unknown. We analyzed transcriptomic and genomic data from representatives of eight of the nine Malvaceae subfamilies. Phylogenetic analysis of nuclear data placed Dombeya (Dombeyoideae) as sister to the rest of Malvadendrina clade, but the plastid DNA tree strongly supported Durio (Helicteroideae) in this position. Intraspecific Ks plots indicated that all sampled taxa, except Theobroma (Byttnerioideae), Corchorus (Grewioideae), and Dombeya (Dombeyoideae), have experienced whole genome multiplications (WGMs). Quartet analysis suggested WGMs were shared by Malvoideae-Bombacoideae and Sterculioideae-Tilioideae, but did not resolve whether these are shared with each other or Helicteroideae (Durio). Gene tree reconciliation and Bayesian concordance analysis suggested a complex history. Alternative hypotheses are suggested, each involving two independent autotetraploid and one allopolyploid event. They differ in that one entails an allopolyploid origin for the Durio lineage, whereas the other invokes an allopolyploid origin for Malvoideae-Bombacoideae. We highlight the need for more genomic information in the Malvaceae and improved methods to resolve complex evolutionary histories that may include allopolyploidy, incomplete lineage sorting, and variable rates of gene and genome evolution.

Nesogordonia tricarpellata (Dombeyaceae), a new species from Madagascar that compels modification of the morphological circumscription of the genus.

Nesogordonia tricarpellata Skema & Dorr, sp. nov., a new species from southeastern Madagascar, is described and illustrated. It differs from all other species of Nesogordonia Baill. in having 6-9 stamens, 3 staminodes, a 3-carpellate ovary, and a 3-valved capsule. These androecial and gynoecial characters require modification of the long-standing circumscription of the genus. The new species also has the southernmost geographic range of any species in the genus.

Recent assembly of the Cerrado, a neotropical plant diversity hotspot, by in situ evolution of adaptations to fire.

The relative importance of local ecological and larger-scale historical processes in causing differences in species richness across the globe remains keenly debated. To gain insight into these questions, we investigated the assembly of plant diversity in the Cerrado in South America, the world's most species-rich tropical savanna. Time-calibrated phylogenies suggest that Cerrado lineages started to diversify less than 10 Mya, with most lineages diversifying at 4 Mya or less, coinciding with the rise to dominance of flammable C4 grasses and expansion of the savanna biome worldwide. These plant phylogenies show that Cerrado lineages are strongly associated with adaptations to fire and have sister groups in largely fire-free nearby wet forest, seasonally dry forest, subtropical grassland, or wetland vegetation. These findings imply that the Cerrado formed in situ via recent and frequent adaptive shifts to resist fire, rather than via dispersal of lineages already adapted to fire. The location of the Cerrado surrounded by a diverse array of species-rich biomes, and the apparently modest adaptive barrier posed by fire, are likely to have contributed to its striking species richness. These findings add to growing evidence that the origins and historical assembly of species-rich biomes have been idiosyncratic, driven in large part by unique features of regional- and continental-scale geohistory and that different historical processes can lead to similar levels of modern species richness.

A novel technique for light delivery through branched or bent anatomic structures.

OBJECTIVE: Photodynamic therapy is an effective cancer treatment, but light delivery constraints currently limit its application to superficial, easily visualized tumors. The goal of this study was to determine whether it would be possible to manipulate the optical properties of irregularly shaped anatomic structures for the purpose of light delivery. Such a technique could potentially expand the role of photodynamic therapy to treat tumors currently viewed as inaccessible to visible light. METHODS: Ex vivo sheep tracheas and lungs were filled with substances of varying refractive indices. The effects on transmission of visible light of a known wavelength introduced into the proximal lumen of the organs were studied. Data were collected with naked-eye observation, standard photography, charge-coupled device imaging, and direct light measurement. RESULTS: Filling a lung or trachea with a liquid possessing a refractive index higher than that of tissue dramatically increases the ability to deliver light around bends and through a branched network. CONCLUSION: It is possible to manipulate the optical properties of an ex vivo organ for the purpose of enhanced light delivery.