Cactophilic Drosophila in South America: A Model for Evolutionary Studies |
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Authors: | Maura Helena Manfrin Fabio Melo Sene |
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Institution: | 1. Departamento de Biologia FFCLRP-USP, Av.dos Bandeirantes, 3900, Ribeir?o Preto, SP, 14040-901, Brazil 2. Departamento de Genética FMRP-USP, Av.dos Bandeirantes, 3900, Ribeir?o Preto, SP, 14049-900, Brazil
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Abstract: | The Drosophila buzzatii cluster is composed of seven cactophilic species and their known geographical distribution encompasses the open vegetation
diagonal, which includes the morphoclimatic Domains of the Caatinga, Chaco and Cerrado, which are situated between the Amazon
and the Atlantic forests. Besides these areas, these cactophilic species are also found in a narrow strip along the Atlantic
coast from northeastern Brazil to the southern tip of the country. The hypothesis of vicariant events, defining the core areas
of each species, is proposed to explain the historical diversification for the cluster. The intraspecific analysis for the
cluster shows a population structure with gene flow restricted by distance, range expansion with secondary contact resulting
in introgression and simpatry, especially in the limits of the species distribution, polytypic populations and assortative
mating in inter population experiments. There is a variation related to these events that depends on the species and geographic
origin of the population analyzed. These events are, hypothetically, described as the results of expansion and retraction
of the population ranges, as a consequence of their association with cacti, which theoretically follow the expansion and retraction
of dry areas during the paleoclimatic oscillations in South America, as that promoted by the glacial cycles of the Quaternary.
The Drosophila buzzatii cluster is divided into two groups. The first one is composed of D. buzzatii, a species that has a broad geographic distribution and no significant differentiation between its populations. The second
is the Drosophila serido sibling set, which encompasses the others species and is characterized by a significant potential for differentiation. |
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Keywords: | Drosophila buzzatii cluster contact zone Drosophila phylogeography population structure repleta group systematics |
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