Genomic, karyological and morphological changes of South American garlics (Ipheion) provide insights into mechanisms of speciation in the Pampean region.

Speciation proceeds through mechanisms that promote reproductive isolation and shape the extent of genetic variation in natural populations, and thus its study is essential to understand the evolutionary processes leading to increased biodiversity. Chromosomal rearrangements are known to facilitate reproductive isolation by hybrid sterility and favour speciation events. The genus Ipheion (Amaryllidaceae, Allioideae) is unique as its species exhibit a remarkable karyological variability but lack population-level genetic data. To unveil the diversification processes acting upon the formation of new lineages within Ipheion in the Pampas of South America, we combined morphology and karyology approaches with genotyping-by-sequencing. Our phylogenomic and population genomics results supported the taxonomic division of Ipheion into three morphological and genetically well-differentiated groups. The origin of Ipheion uniflorum was traced back to its current southern distribution area in the southern Pampean region (in Argentina), from where it had expanded to the north reaching Uruguay. Our results further suggested that chromosome rearrangements and ploidy shifts had triggered speciation events, first during the origin of I. uniflorum and later during its subsequent diversification into I. recurvifolium and I. tweedieanum, in both cases reinforced by extrinsic factors and biogeographical settings. The current study illustrates the analytical power of multidisciplinary approaches integrating phylo- and population genomics with classic analyses to reveal evolutionary processes in plants.

Reconstructing the phylogenetic history of the tribe Leucocoryneae (Allioideae): Reticulate evolution and diversification in South America.

At present, the Allioideae is included within the Amaryllidaceae, which is an economically important bulb crop subfamily that includes onion, garlic, and ornamental species worldwide. The Allioideae includes four tribes geographically disjunct namely: Allieae, widespread in the northern hemisphere, tribe Tulbaghieae distributed in South Africa, and tribes Leucocoryneae and Gilliesieae are endemic to South America. Although we agree with the current tribal circumscription of the Leucocoryneae including Beauverdia, Ipheion, Latace, Leucocoryne, Nothoscordum, and Tristagma, there are still taxonomic and phylogenetic uncertainties regarding the monophyly, phylogenetic relationships, and divergence time of several lineages in a biogeographic context. In this study, a comprehensive molecular phylogeny of the tribe Leucocoryneae was inferred based on nuclear ribosomal ITS and plastid (ndhF and matK) sequences. We used Bayesian inference and maximum parsimony analyses to predict ancestor-descendant relationships. Our results confirmed the monophyly of the four tribes of subfamily Allioideae. Similarly, within the Leucocoryneae, Ipheion, Leucocoryne, and Nothosocordum Sect. Inodorum were also monophyletic; Tristagma and Nothoscordum would be monophyletic if including Ipheion and Beauverdia, respectively. Network analyses were implemented to reveal putative scenarios of reticulate evolution. Both, current and ancestral hybridization events have presumably occurred among species of Nothoscordum Sect. Nothoscordum and Beauverdia favored by spatial overlapping of populations, flowering synchrony and a puzzling pattern of cytogenetic attributes. The estimation of divergence time indicates that the tribe Leucocoryneae originated in the Late Oligocene in southern South America with possible ancestors in Africa. Most crown lineages within the tribe diversified in conjunction with biogeographical events during the Late Miocene to Pliocene. We posit that new suitable environments available after the Andean uplift and during the Age of the Southern Plains provided the favorable geographic setting for the major lineages of Leucocoryneae in southern Pampas, extra-Andean Patagonia, Andean mountains, and in Chile. Hybridization, polyploidization, and Robertsonian translocations of chromosomes have been the driving forces and major sources of speciation in the evolution of tribe Leucocoryneae.

A novel indicator of karyotype evolution in the tribe Leucocoryneae (Allioideae, Amaryllidaceae).

The tribe Leucocoryneae is taxonomically and cytogenetically complex, mainly due to its extraordinary morphological and karyological variation. Robertsonian translocations had long been recognized as a central factor contributing to karyotype diversity within the Leucocoryneae, but so far no major tendency prevailing on the observed complexity of karyotype formula among species has been identified. The assessment of nuclear DNA contents by flow cytometry using propidium iodide in 23 species, representing all genera within the tribe, showed a monoploid genome size variation of 1Cx = 9.07-30.46 pg denoting a threefolds fluctuation. A highly significant linear association between the average DNA content per chromosome arm (2C/FN) and the monoploid genome size (1Cx) is reported for the first time and identified as a novel indicator of a trend governing karyotype diversity within Leucocoryneae. This trend shows that a reduction in DNA content per chromosome arm is influencing and has shaped karyotype evolution of different monophyletic groups within the tribe despite the complex karyotype diversity and apparently contrasting patterns of genome sizes.

First Glimpse on Spring Starflower Domestication.

The cultivation and domestication of plants are human-driven processes that change the biology and attributes of a plant. Ipheion uniflorum is a bulbous geophyte known as Spring Starflower whose cultivation dates back to the first half of the 19th century. At least seven cultivars have been developed from natural stands. However, comparative analyses of wild and cultivated materials are largely missing. In the present study, we provide a morphological evaluation and analyses of the cytological and genetic variability of I. uniflorum that reveal significant levels of differentiation and evidence of artificial selection in the Spring Starflower. Distinctive phenotypic characters in cultivated materials that are rarely found or lacking in wild plants and natural populations, such as pink or violet flowers, together with its reduced heterozygosity and starting genetic differentiation support the view of early mechanisms of domestication acting upon Spring Starflower plants. The probable geographic origin of the cultivated forms is discussed together with perspectives for plant breeding.

The Uses of Herbaria in Botanical Research. A Review Based on Evidence From Argentina.

Botanists, a section of the broad universe of researchers in Biology, are intensive users of herbaria. Presumably, all botanists use herbaria, with greater or lesser frequency and intensity, in the development of their research. In this article, we will try to prove this statement. For this purpose, an institutional history of Botany and herbaria in Argentina is presented. This study will also show that there are other fields of knowledge in which the herbarium has a role as an input, or data source, for research (e.g. agronomy, ethnobotany, medicine). On the other hand, it will be demonstrated that, in addition to the uses of the herbarium in basic science, this institution has a crucial role in the knowledge and preservation of biodiversity, and in the improvement of species for commercial use.