Carolina Carrizo García

Phylogenetic relationships, diversification and expansion of chili peppers (Capsicum, Solanaceae)

BACKGROUND AND AIMS Capsicum (Solanaceae), native to the tropical and temperate Americas, comprises the well-known sweet and hot chili peppers and several wild species. So far, only partial taxonomic and phylogenetic analyses have been done for the genus. Here, the phylogenetic relationships between nearly all taxa of Capsicum were explored to test the monophyly of the genus and to obtain a better knowledge of species relationships, diversification and expansion. METHODS Thirty-four of approximately 35 Capsicum species were sampled. Maximum parsimony and Bayesian inference analyses were performed using two plastid markers (matK and psbA-trnH) and one single-copy nuclear gene (waxy). The evolutionary changes of nine key features were reconstructed following the parsimony ancestral states method. Ancestral areas were reconstructed through a Bayesian Markov chain Monte Carlo analysis. KEY RESULTS Capsicum forms a monophyletic clade, with Lycianthes as a sister group, following both phylogenetic approaches. Eleven well-supported clades (four of them monotypic) can be recognized within Capsicum, although some interspecific relationships need further analysis. A few features are useful to characterize different clades (e.g. fruit anatomy, chromosome base number), whereas some others are highly homoplastic (e.g. seed colour). The origin of Capsicum is postulated in an area along the Andes of western to north-western South America. The expansion of the genus has followed a clockwise direction around the Amazon basin, towards central and south-eastern Brazil, then back to western South America, and finally northwards to Central America. CONCLUSIONS New insights are provided regarding interspecific relationships, character evolution, and geographical origin and expansion of Capsicum A clearly distinct early-diverging clade can be distinguished, centred in western-north-western South America. Subsequent rapid speciation has led to the origin of the remaining clades. The diversification of Capsicum has culminated in the origin of the main cultivated species in several regions of South to Central America.

An approach to the diversity of endothecial thickenings in Solanaceae

Summary The special features of the endothecial thickenings in 59 species of 44 Solanaceae genera were studied and four different thickening types were distinguished: annular, helical, and reticulate ribs, and palmate baseplate. Some variations can be observed due to the presence of branched ribs and differences in the ribs width and number per cell. In general, each species shows a single thickening type, although there may be a range of variation within a single pattern in some cases. It is also possible to find species in which two types coexist. The coincidence among the thickening types and the different hierarchical position of the taxa is analysed. Even when a possible scheme of structural relationships can be deduced, it is difficult to elucidate the polarisation of the types of thickening due to the disagreements in the suprageneric classification.

It is a matter of timing: asynchrony during pollen development and its consequences on pollen performance in angiosperms—a review

Functional pollen is needed to successfully complete fertilization. Pollen is formed inside the anthers following a specific sequence of developmental stages, from microsporocyte meiosis to pollen release, that concerns microsporocytes/microspores and anther wall tissues. The processes involved may not be synchronous within a flower, an anther, and even a microsporangium. Asynchrony has been barely analyzed, and its biological consequences have not been yet assessed. In this review, different processes of pollen development and lifetime, stressing on the possible consequences of their differential timing on pollen performance, are summarized. Development is usually synchronized until microsporocyte meiosis I (occasionally until meiosis II). Afterwards, a period of mostly asynchronous events extends up to anther opening as regards: (1) meiosis II (sometimes); (2) microspore vacuolization and later reduction of vacuoles; (3) amylogenesis, amylolysis, and carbohydrate inter-conversion; (4) the first haploid mitosis; and (5) intine formation. Asynchrony would promote metabolic differences among developing microspores and therefore physiologically heterogeneous pollen grains within a single microsporangium. Asynchrony would increase the effect of competition for resources during development and pollen tube growth and also for water during (re)hydration on the stigma. The differences generated by developmental asynchronies may have an adaptive role since more efficient pollen grains would be selected with regard to homeostasis, desiccation tolerance, resilience, speed of (re)hydration, and germination. The performance of each pollen grain which landed onto the stigma will be the result of a series of selective steps determined by its development, physiological state at maturity, and successive environmental constrains.

Pollen starch reserves in tomato relatives: Ecophysiological implications

The presence or absence of starch in microspore development and in pollen grains was recorded in eleven wild tomato species (Solanum sect. Lycopersicon) and two close relatives (S. lycopersicoides and S. sitiens). In all the species starch started to accumulate in the early microspore bicellular stage and continued until the cytoplasm was filled. At flower anthesis, pollen grains were mostly starchless in the wild tomatoes, except in S. pennellii, which had starchy pollen. Starchy pollen is also present in the two related species. The latter two species had larger pollen grains and grow in drier environments than the other species. The heterogeneity of pollen starch content among all these species, supposed to have the same pollination mechanism, is a new finding supporting the idea that starch content and pollination mechanism do not necessarily influence each other. The presence of starchy pollen in the self‐incompatible species, which grow in the driest environments, raises questions regarding the relationship between carbohydrates content and pollen survival.

Combination of sequences of cell divisions in the anther wall formation in Solanaceae species

Summary Anther wall formation was studied in six Solanaceae species ( Bouchetia anomala , Capsicum tovari , Margaranthus solanaceus , Physalis viscosa , Withania adpressa , and Withania riebeckii ). Combinations of at least three different sequences of cell divisions were observed in the same species, even in the same microsporangium. These data contrast with the general idea that each species shows a single pattern or type of wall formation. The mentioned co-occurrence of cell divisions evidences the close affinity of the anther wall formation types, and the thin boundary between them. This co-occurrence also reveals different cell abilities and some kind of convergence, since two neighbour cells may go through different sequences of divisions but originate the same wall structure (= number of layers).

Anther wall development and structure in wild tomatoes (Solanum sect. Lycopersicon) : functional inferences

Development of the anther wall and its structure at maturity in wild tomatoes (Solanum sect. Lycopersicon) are described, and the features are discussed in relation to anther dehiscence and the buzz-pollination mechanism. The anther wall formation follows two different patterns in the same microsporangia and a high number of cells divisions may occur. The number of layers formed varies across the ventral, dorsal and lateral surfaces of each theca. Large epidermal cells develop, lining the stomium, and they could possibly be involved in stomium opening. Cells with thickenings are formed in the apical fifth of the anther, where the tissues seem to degenerate after the stomium opening, forming a wider aperture through which the pollen can be shed. The multilayered dorsal wall remains swollen and could act as an attractant to pollinators and as mechanical support. The apparently disordered anther wall development sets up different structures across and along the anther, which can be interpreted as histological adaptations to the buzz-pollination mechanism.

Pollen phenotyping and performance in rocoto chili (Capsicum pubescens Ruiz et Pav., Solanaceae)

Abstract The rocoto chili (Capsicum pubescens) is a species native to the highlands of South America, which is cultivated for its fruits. The species is regarded as self-compatible; however, self-incompatible strains and even a variable degree of self-incompatibility have been found. To characterise pollen grains and determine whether there is also variation in pollen performance and male fertility in the species, pollen morphology, cellular state, starch content, viability, longevity and germinability were analysed in plants obtained from the germplasm cultivated in Argentina. All the individuals studied were male fertile, showing a high percentage of vital pollen, capable of germinating in vitro. Some pollen features were uniform (e.g. exine sculpture, number of nuclei at maturity), but there were significant variations in pollen performance among the plants studied.

Phylogenetic relationships of Deprea: New insights into the evolutionary history of physaloid groups

Deprea is the genus with the second highest species richness in tribe Physalideae (Solanaceae) and comprises 50 species that are mainly distributed in the Andes of South America. The taxonomy of Deprea has been unstable after controversial hypotheses about its position and circumscription. Additionally, biogeographical inferences are only based on observations of the restricted area of distribution of some species and no ancestral area estimation have been performed. Here, we present a phylogenetic analysis and an ancestral area reconstruction of Deprea in order to establish its circumscription, resolve its position within Physalideae, and reconstruct its biogeographical history. Phylogenetic analyses were conducted using Maximum Likelihood and Bayesian approaches. Forty-three Deprea species and 26 related taxa were sampled for three DNA markers (psbA-trnH, ITS, and waxy). A Bayesian binary MCMC model was applied in order to infer ancestral areas. Deprea is resolved as a strongly supported monophyletic group according to its current circumscription and is placed within subtribe Withaninae of Physalideae. The phylogenetic relationships enabled us to solve taxonomic problems including the rejection and acceptance of previous synonyms. The most probable ancestral area for Deprea is the Northern Andes of South America and the Amotape-Huancabamba zone. Our phylogeny provides increased resolution and support for the current position and circumscription of Deprea. Better resolution of interspecific relationships was also obtained, although some affinities remain unclear. The phylogenetic and ancestral area reconstructions provide a framework for addressing taxonomic problems and investigating new evolutionary questions.