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It is well known that Darwin and Wallace came to discover the phenomenon of evolution through a historical approach to the geographical distribution of organisms. Before Darwin, evolution was a mere speculation that could be invoked to explain some facts. Darwin’s biogeographical argument for evolution is based largely on three main explanatory hypotheses. The first is that the geographical distribution of organisms is historically informative. The second hypothesis is that long-distance dispersal over barriers is one main force (extinction is the other) that modifies the distribution of organisms. The third of Darwin’s biogeographical hypotheses is that the factors that shape the distribution of organisms are mainly historical (large, often global and long temporal scales) rather than ecological (small spatial and short temporal scales). From the time of Darwin until now, a wide spectrum of biogeographical schools have provided new insights that challenge the central role of space, dispersal and history as the main explanatory hypotheses for the distribution of organisms, generating three binary opposites: (1) the spatial dimension of evolution: geographical distribution of organisms as historically informative vs. historically uninformative; (2) the processes that modify the geographical distribution of organisms: dispersal vs. vicariance; and (3) the explanation of geographical distribution: history vs. ecology. We analyse these three binary opposites to show that the components of each are complementary rather than antagonistic approaches to the study of biogeography.

Aim The pappus is one of the most distinctive features of the genera belonging to the sunflower family, and is an efficient mechanism for dispersion by wind. The pappose Holocheilus (seven species) and the non-pappose Panphalea (nine species) are two genera of the monophyletic subtribe Nassauviinae (Asteraceae, Mutisieae), which overlap in their areas of distribution. This paper aims to reconstruct the biogeographical histories that shaped the distribution of these two genera, which are phylogenetically and geographically related, but differ in their means of dispersion. Our initial expectation was that the dispersion capability of the pappus should be reflected in more dispersal events in Holocheilus than in Panphalea. Location South-eastern Brazil, Paraguay, Uruguay and Argentina. Methods Morphological data were acquired from the literature and by analysis of specimens. Two cladistic analyses, one for Holocheilus and one for Panphalea, were based on morphological characters, and data matrices were analysed with the Fitch parsimony algorithm of paup. The ancestral distributions were reconstructed using diva ver. 1.1 according to the dispersal–vicariance optimization method. Results The Paranense-fields were identified as the most likely ancestral area of Holocheilus and Panphalea. Biogeographical reconstruction of Holocheilus shows several dispersal events from the Paranense-fields: two ancestral dispersal events to the Yungas, followed by vicariance events (Paranense-fields/Yungas) and numerous terminal dispersals to the surrounding areas such as Chacoan, Pampean and Espinal. diva reconstruction of Panphalea distribution also shows frequent terminal dispersals, with no vicariant events, from the Paranense-fields to the other areas: (1) to Espinal, Pampean-Uruguayan, Pampean-oriental; (2) to Paranense-hills; (3) to Pampean-Uruguayan; and (4) to Paranense-pine lands. Main conclusions In the past, both genera probably originated in the Paranense-fields area, which was subject to the dry and humid cycles of the Quaternary glaciations. Dispersal was the process that predominantly shaped the distribution of Panphalea and Holocheilus, with approximately the same number of dispersal events in both genera, despite differing ranges of dispersion. The main barriers to dispersal were the dry Cerrado and Chaco, the latter promoting vicariance in Holocheilus. The lack of a pappus in Panphalea was a limitation for its dispersion compared with Holocheilus.

Historical biogeography is going through an extraordinary revolution concerning its foundations, basic concepts, methods, and relationships to other disciplines of comparative biology. There are external and internal forces that are shaping the present of historical biogeography. The external forces are: global tectonics as the dominant paradigm in geosciences, cladistics as the basic language of comparative biology and the biologist’s perception of biogeography. The internal forces are: the proliferation of competing articulations, recourse to philosophy and the debate over fundamentals. The importance of the geographical dimension of life’s diversity to any understanding of the history of life on earth is emphasized. Three different kinds of processes that modify the geographical spatial arrangement of the organisms are identified: extinction, dispersal and vicariance. Reconstructing past biogeographic events can be done from three different perspectives: (1) the distribution of individual groups (taxon biogeography) (2) areas of endemism (area biogeography), and (3) biotas (spatial homology). There are at least nine basic historical biogeographic approaches: centre of origin and dispersal, panbiogeography, phylogenetic biogeography, cladistic biogeography, phylogeography, parsimony analysis of endemicity, event-based methods, ancestral areas, and experimental biogeography. These nine approaches contain at least 30 techniques (23 of them have been proposed in the last 14 years). The whole practice and philosophy of biogeography depend upon the development of a coherent and comprehensive conceptual framework for handling the distribution of organisms and events in space.