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Accueil du site → Doctorat → États-Unis → 1980 → CHROMOSOMAL POLYMORPHISM IN NATURAL POPULATIONS OF THE DESERT ADAPTED SPECIES, DROSOPHILA MOJAVENSIS

University of Arizona (1980)

CHROMOSOMAL POLYMORPHISM IN NATURAL POPULATIONS OF THE DESERT ADAPTED SPECIES, DROSOPHILA MOJAVENSIS

Johnson, William Robert

Titre : CHROMOSOMAL POLYMORPHISM IN NATURAL POPULATIONS OF THE DESERT ADAPTED SPECIES, DROSOPHILA MOJAVENSIS

Auteur : Johnson, William Robert

Université de soutenance : University of Arizona

Grade : Doctor of Philosophy (PhD) 1980

Résumé
The karyotype variability of Drosophila mo.lavensis was examined from thirty-nine natural populations in southern Arizona and California, USA, and Sonora, Sinaloa, and Baja California, Mexico. The distribution and degree of heterozygosity of the four gene arrangements on the second chromosome and the two gene arrangements of the third in conjunction with observations of the species* genetics and ecology has led to a hypothesis of population structure and inversion heterokaryotypy. The baja race, fotmd on the peninsula of Baja California is sub-divided into a mosaic of three marginal populations in three distinct phytogeographic regions. The description of these populations as being marginal or central is based on hypothesized trophic resource production in the host cactus, Machaerocereus. and population survival through time. The cen tral populations have continuity in time in the same geographic area, while marginal populations, due to the ephemeral nature of the resource in those areas undergo frequent local extinctions and must be re established by inter-deme migration. This latter description is also applicable to the host plants and populations of the mojavensls race (Ferocactus) in southern California and the sonorensis race (Lemalreocereus) In Sonora and Sinaloa, Mexico. In regions of sustained resource production, populations of D^. mo.lavensis are able to increase fitness by utilizing heterokaryotypy. In marginal populations, direc tional karyotype selection maintains regionally (phytogeographic) specific inversions in a relatively homozygous state.

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