Cleistogamy, a breeding system in which permanently closed, self-pollinated flowers are produced, has received increasing attention in recent years, but the last comprehensive review of this system was over 20 years ago. The goal of this paper is to clarify the different types of cleistogamy, quantify the number of families, genera, and species in which cleistogamy occurs, and estimate the number of times and potential reasons why cleistogamy has evolved within angiosperms. Cleistogamous species were identified through a literature survey using 13 online databases with references dating back to 1914; only those species well-supported by floral descriptions or empirical data were included in the data set. On the basis of this survey, we suggest the use of three different categories of cleistogamy in future studies: dimorphic, complete, and induced. Based on these categories, cleistogamy in general is present in 693 angiosperm species, distributed over 228 genera and 50 families. When analyzed on a family level across the angiosperms, the breeding system has evolved approximately 34 to 41 times. Theoretical investigations indicate that the evolution of cleistogamy in taxa may be influenced by the presence of heterogeneous environments, inbreeding depression and geitonogamy, and differential seed dispersal, as well as by various ecological factors and plant size. Cleistogamy will undoubtedly be discovered in additional species as the reproductive biology of more taxa is examined in the future. Such information will be invaluable for understanding the selective pressures and factors favoring the evolution of cleistogamy as well as the evolutionary loss of this breeding system, a subject that has received little attention to date.

The structure of the living Patagonian flora, dominated by the steppe, is a direct consequence of past climatic and tectonic events. These arid-adapted communities were widespread during the Late Neogene, but their origin in Patagonia can be traced back to the Paleogene. Vegetational trends throughout Paleocene-Miocene time are based on available paleobotanical and palynological information. Four major supported stages in vegetation turnovers are recognized: (1) Paleocene and Early Eocene floras were rainforest-dominated, including many angiosperms with warm-temperate affinities (e.g., palms, Juglandaceae, Casuarinaceae). However, mainly in the Early Eocene, some geographic areas influenced by warm but drier conditions are suggested by the occurrence of certain taxa (e.g., Anacardiaceae). These areas containing arid-adapted floras would have arisen in Patagonian inland regions, in a generally wet continent. (2) The Middle Eocene-Early Oligocene interval was distinguished by the invasion of Nothofagus forests. Progressive replacements of megathermal communities by meso- and microthermal rainforest are documented. Nothofagus forest expansion suggests a marked cooling trend at this time, although some megathermal elements (Aquifoliaceae Ilex, Tiliaceae-Bombacaceae, Sapindaceae) were still present at the beginning of this period. Arid-loving taxa have not been recorded in abundance. (3) Late Oligocene-Early Miocene floras were characterized by the occurrence of shrubby-herbaceous elements belonging to Asteraceae, Chenopodiaceae, Ephedraceae, Convolvulaceae, Fabaceae, and Poaceae. They began to give a modern appearance to plant communities. Xerophytic formations would have occupied coastal salt marshes and pockets in inland areas. Megathermal angiosperms of the Rubiaceae, Combretaceae, Sapindaceae, Chloranthaceae, and Arecaceae occurred mainly during the Late Oligocene. Forests of Nothofagaceae, Podocarpaceae, and Araucariaceae are still documented in extra-Andean Patagonia; however, a contrast between coastal and inland environments may have developed, particularly in the Miocene. (4) Middle-Late Miocene records show an increasing diversity and abundance of xerophytic-adapted taxa, including Asteraceae, Chenopodiaceae, and Convolvulaceae Cressa/Wilsonia. Expansion of these xerophytic taxa, coupled with extinctions of megathermal/nonseasonal elements, would have been associated with both tectonic and climatic forcing factors, led to the development of aridity and extreme seasonality. These arid-adapted Late Miocene floras are closely related to modern communities, with steppe widespread across extra-Andean Patagonia and forest restricted to the western humid upland regions.

Eighty-seven species belonging to 59 genera and 33 plant families identified in the study area are presented. The three families with the most species represented were Labiatae (nine aquatic species), Compositae (seven species), and Salicaceae (seven species). The genera most represented were Mentha (six species), Polygonum (five species), and Salix (five species). Sixty-three folk-medicinal aquatic species (73.3%) had similar therapeutic uses in neighboring countries, while the 24 remaining species (26.7%) did not show therapeutic similarity with their use in other countries. Emerged species (plants rooted in soil under water but which emerge partially above the water's surface) were the most recorded, while amphibious, submerged, and floating species were the least recorded. The folk-medicinal importance of the recorded aquatic species were classified by rank-order priority (ROP). Twenty-one species (24%) had ROP values higher than 50, indicating the highest popularity level in folk-medicinal potentiality; 26 species (29.9%) had therapeutic effects informed by fewer than three informants and were therefore excluded from further consideration; 40 species (46.1%) had ROP values of less than 50, and were thus classified as nonpopular medicinal plants.