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Maximum parsimony and Bayesian likelihood analysis of ribosomal DNA internal transcribed spacer (ITS) sequences from 55 samples representing 25 species, subspecies, and/or hybrids of Tropaeolum sect. Chilensia yielded a tree with a large proportion of well-supported nodes at the interspecific and intersubspecific level. However, the tree shows samples from two species, T.azureum and T. brachyceras, arising in two different positions. Samples representing subspecies of T. hookerianum and T. leptophyllum suggest that these species are polyphyletic. The data corroborate evidence for hybridization between T. brachyceras and T. tricolor. Consideration of interfertility data, past and present Chilean ecology, and empirical evidence for the behavior of phenotypic and genotypic characters in known hybrids suggest a high likelihood that reticulate evolution has played a role in the diversification of T. sect. Chilensia. This reticulate evolution may explain the discordance between the ITS tree and the conventional taxonomy. High divergence in ITS sequences between T. sect. Chilensia and other members of Tropaeolum prohibits reliable outgroup-rooting, but midpoint rooting places the root at a partition comprising taxa whose distribution conforms to a relictual eastern-western South American disjunction described for other taxa. Within the Chilean taxa, the analysis suggests that biogeographic diversification has been from the mesophytic southern habitats northward to central mediterranean and northern arid zones. [ABSTRACT FROM AUTHOR]

Examines the plant distribution of Malesherbiaceae, a monogenetic plant group in South America. Characteristics of the habitat; Interrelationship between the rise of the Andes and increased aridity on the western slopes; Occurrence of geological and climatic changes.

Examines the plant distribution of Oxalis tuberosa alliance in South America. Use of cladograms developed from DNA sequence data; Comparison between phylogeny and distribution; Presence of endemic species.

A taxonomic revision of the Euglenophyta found exclusively in South America is presented. The taxonomy, geographical distribution and critical analysis of the synonyms are given. More than two hundred species and infraspecific entities from South America are described, many of them recorded several times in different regions. The genus Trachelomonas comprises the highest number of new taxa, reaching more than 100 entities. It is followed by Phacus (48 taxa), Strombomonas (33 taxa), Euglena (15 taxa) Lepocinclis (14 taxa), and Distigma, Entosiphon and Sphenomonas with one new taxon each. [ABSTRACT FROM AUTHOR]