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Accueil du site → Doctorat → États-Unis → 1985 → A BIOGEOGRAPHICAL ANALYSIS OF A VICARIANT EVENT : THE HERPETOFAUNA OF THE GIBRALTAR STRAIT (SPAIN, MOROCCO, ELECTROPHORESIS, MOLECULAR CLOCK

University of California, Berkeley (1985)

A BIOGEOGRAPHICAL ANALYSIS OF A VICARIANT EVENT : THE HERPETOFAUNA OF THE GIBRALTAR STRAIT (SPAIN, MOROCCO, ELECTROPHORESIS, MOLECULAR CLOCK

BUSACK, STEPHEN DANA

Titre : A BIOGEOGRAPHICAL ANALYSIS OF A VICARIANT EVENT : THE HERPETOFAUNA OF THE GIBRALTAR STRAIT (SPAIN, MOROCCO, ELECTROPHORESIS, MOLECULAR CLOCK)

Auteur : BUSACK, STEPHEN DANA

Université de soutenance : University of California, Berkeley

Grade : Doctor of Philosophy (PhD) 1985

Résumé
Between 5.5 and 7.0 MYBP the formation of the Strait of Gibraltar allowed water from the Atlantic Ocean to fill the basin now known as the Mediterranean Sea. This vicariant event divided the amphibian and reptile fauna then inhabiting southern Spain and northern Morocco into allopatric but conspecific faunas. Because the Strait has continued from its formation to present a geographic barrier to the exchange of terrestrial vertebrates between Africa and Europe, this region and its native herpetofauna provide a natural laboratory in which various tenets of current biogeographic theory may be evaluated. Electrophoretically obtained molecular data allowed an empirical biogeographic analysis of the trans-Gibraltar herpetofauna. Specimens representing paired comparisons of 17 conspecific taxa provided estimates of accumulated genetic distance (Nei’s (’)D) which varied from 0.0 to 0.6 between Spanish and Moroccan populations. Further examination of these genetic data demonstrated that the rate of migration between continental populations of the trans-Gibraltar herpetofauna ranged from being greater to being less than the estimated mutation. European and African populations of several taxa traditionally presumed to be genically homogeneous were shown to be heterogeneous. An analysis of the distribution of alleles within and between continental populations of these taxa suggested that the ability to maintain genetic continuity across the marine barrier varied from species to species. Estimates of the degree of habitat specificity and the frequency of occurrence of individuals were considered as possible correlates of intracontinental genic differentiation. No demostrable correlation was found between these ecological parameters and the genic differentiation demonstrated by Spanish populations of each taxon. The possibility of accidental transport as the mechanism by which reproductive contact is maintained in genically homogeneous populations is advanced. Future workers are admonished against the indiscriminate application of genetic distances to problems involving geologic time.

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