A brainstorm on the systematics of Turnera (Turneraceae, Malpighiales) caused by insights from molecular phylogenetics and morphological evolution.

With 145 species, Turnera is the largest genus of Turneraceae (Malpighiales). Despite several morphotaxonomic and cytogenetic studies, our knowledge about the phylogenetic relationships in Turnera remains mainly based on morphological data. Here, we reconstruct the most comprehensive phylogeny of Turnera with molecular data to understand the morphological evolution within this group and to assess its circumscription and infrageneric classification. We analyzed two nuclear and six plastid markers and 112 taxa, including species and infraspecific taxa, 97 from Turnera, covering the 11 series of the genus. Bayesian inference, maximum parsimony and maximum likelihood analyses show that Turnera, as traditionally circumscribed, is not monophyletic. The genus is divided into two well-supported independent clades; one of them is sister to the genus Piriqueta and is here segregated as the new genus Oxossia. According to our reconstructions, Turnera probably evolved from an ancestor without extrafloral nectaries and with solitary, homostylous flowers with yellow petals. The emergences of extrafloral nectaries and distyly, both common in extant taxa, played an important role in the diversification of the genus. An updated infrageneric classification reflecting the relationships within Turnera is now possible based on morphological synapomorphies and is here designed for further studies.

Evidence of 2n microspore production in a natural diploid population of Turnera sidoides subsp. carnea and its relevance in the evolution of the T. sidoides (Turneraceae) autopolyploid complex.

Turnera sidoides is a complex of distylous perennial rhizomatous herbs that includes five subspecies. Since polyploidy has played a prominent role within this species (x = 7), ongoing studies in T. sidoides are focused on the understanding of the mechanisms involved in the origin and the establishment of polyploids. Therefore, aiming to contribute to the understanding of the mode of polyploid formation, in this study we investigated the frequency of unreduced microspores in a natural diploid population of T. sidoides subsp. carnea by analyzing the size range of pollen and the constitution of the sporads. The results showed that some of the individuals studied produced 2n and 4n microspores, both in short- and long-styled floral morphs. The analysis performed documents the production of unreduced microspores in T. sidoides subsp. carnea and provides evidence that support the hypothesis of sexual polyploidization as one of the most probable mechanisms involved in the origin of polyploids within this species complex. The role of unreduced pollen in the establishment and persistence of newly formed polyploids in diploid populations of T. sidoides is also discussed.

Selection on signal­reward correlation: limits and opportunities to the evolution of deceit in Turnera ulmifolia L.

Because pollinators are unable to directly assess the amount of rewards offered by flowers, they rely on the information provided by advertising floral traits. Thus, having a lower intra-individual correlation between signal and reward (signal accuracy) than other plants in the population provides the opportunity to reduce investment in rewards and cheat pollinators. However, pollinators' cognitive capacities can impose a limit to the evolution of this plant cheating strategy if they can punish those plants with low signal accuracy. In this study, we examined the opportunity for cheating in the perennial weed Turnera ulmifolia L. evaluating the selective value of signal accuracy, floral display and reward production in a natural population. We found that plant reproductive success was positively related to signal accuracy and floral display, but not to nectar production. The intensity of selection on floral display was more than three times higher than on signal accuracy. The pattern of selection indicated that pollinators can select for signal accuracy provided by plants and suggests that learning abilities of pollinators can limit the evolution of deceptive strategies in T. ulmifolia.

Structure of styles and pollen tubes of distylous Turnera joelii and T. scabra (Turneraceae): are there different mechanisms of incompatibility between the morphs?

We investigate the anatomy and fine structure of styles and pollen tubes of two distylous Turnera species, which possess a heteromorphic self-incompatibility system. We use fluorescence and transmission electron microscopy to provide the first description of the cellular aspects of pollen-pistil interactions and ultrastructural changes to pollen tubes during the self-incompatibility response of the morphs. No obvious ultrastructural differences occur between pistils and compatible pollen tubes. Conspicuous differences were, however, observed between incompatible pollen tubes of the morphs. Incompatible pollen tubes of the long-styled morph always appear to be intact, and pollen tube tips are often highly fluorescent when stained with aniline blue, a stain for callose. Swelling and loss of cristae of mitochondria, and circular rough endoplasmic reticulum, were observed for incompatible pollen tubes of the long-styled morph. For incompatible pollen tubes of the short-styled morph, the tube cell wall apex and plasma membrane often appear to be ruptured and no easily recognizable organelles, such as mitochondria, can be discerned. Our results clearly show ultrastructural differences between the morphs and support the hypothesis that different self-incompatibility mechanisms might operate between them.

Estudo farmacobotânico comparativo de folhas de Turnera chamaedrifolia Cambess. e Turnera subulata Sm. (Turneraceae) / Comparative and pharmacobotanical study of the leaves of Turnera chamaedrifolia Cambess. and Turnera subulata Sm. (Turneraceae)

Neste trabalho realizou-se um estudo farmacobotânico comparativo entre as folhas de Turnera chamaedrifolia Cambess. e Turnera subulata Sm. (Turneraceae), espécies cujas folhas são usadas na medicina popular. As identificações botânicas e as morfodiagnoses macroscópicas foram realizadas após estudos morfológicos. Para as morfodiagnoses microscópicas realizaram-se secções paradérmicas e transversais de folhas (lâmina e pecíolo), que foram posteriormente clarificadas em hipoclorito (1 por cento) e coradas com safranina hidroalcoólica e safrablue. As duas espécies compartilham o mesmo tipo de estômato, paracítico, entretanto, T. chamaedrifolia possui folhas com a epiderme hipoestomática, com células de paredes ondeadas; o mesofilo dorsiventral; e a vascularização do pecíolo com três feixes nas porções distal e mediana, e apenas um feixe na proximal. Em T. subulata a epiderme é anfi-hipoestomática, com paredes sinuosas; mesofilo isobilateral; e a vascularização do pecíolo possui um feixe na porção distal e três feixes nas porções mediana e proximal. A morfologia das estruturas vegetativas e reprodutivas associada à anatomia foliar são caracteres distintivos para estas espécies.

This work is a comparative pharmacobotanical study between the leaves of Turnera chamaedrifolia Cambess. and Turnera subulata Sm. (Turneraceae), which are used in folk medicine. The botanical identifications and macroscopical morphodiagnosis were done after morphological studies. The microscopical morphodiagnosis was carried out by paradermic and transversal cuts of the leaves (blade and petiole), clarified and coloured with safranin and astrablue. The leaves of T. chamaedrifolia have hypostomatics epidermis, with wavy cells walls; the mesophyll is dorsiventral; and the vascular system of the peciole has three vascular bundles in the distal and medium portions, and only one, in the proximal portion. T. subulata has amphihypostomatic epidermis, with sinuous cells walls; the mesophyll is isobilateral; and the vascular system of the petiole has only one vascular bundle in the distal portion and three in the medium and proximal portions. The vegetative and reproductive morphologies associated to the leaf anatomy constitute a set of distinctive characters for these species.

Inheritance of spontaneous mutant homostyles in Turnera subulata x krapovickasii and in autotetraploid T. scabra (Turneraceae).

To explore the genetic architecture of distyly in Turnera spp., we determined the inheritance and compatibility behaviour of two spontaneous homostyled mutants. A long-homostyled mutant shoot arose on an otherwise short-styled plant that was an artificial hybrid (Turnera subulata x T. krapovickasii) between two diploid distylous species. The mutation appears to be an allele, SH, of the distyly locus with the dominance relationships, S>SH>s, where S confers the short-styled phenotype, SH confers homostyly in SHSH and SHs genotypes, and ss genotypes are long-styled. Aberrant segregation ratios were observed among some crosses and might be the result of pollen competition. Compatibility relationships are consistent with the hypothesis that a gene complex determines distyly. Infrequently, revertant short-styled flowers have appeared on cuttings of the T. subulata x T. krapovickasii mutant and on occasion, short-styled progeny have appeared in crosses where none were expected. A second mutant homostyle was discovered in autotetraploid T. scabra. The mutation is inherited as above, however, tetrasomic inheritance occurs at the locus. This homostyled mutant carries two copies of the SH allele and has the duplex genotype SHSHss. Compatibility relationships were as observed above. The occurrence of homostyled mutants is consistent with the hypothesis that a linked gene complex underlies the inheritance of distyly in Turnera but we cannot discount the hypothesis that an allelic series is responsible.