versión impresa ISSN 0716-078X
Rev. chil. hist. nat. v.74 n.1 Santiago mar. 2001
In Memory of Danko Brncic, a friend
En memoria de Danko Brncic, un amigo
The Department of Biology, Virginia Polytechnic Institute and State University, 2089 Derring Hall,
Backsburg, Virginia 24061, U.S.A.
I do not intend to write a scholarly article in memory of my friend, Danko Brncic. Suffice it to say that during my daughter's trip to Chile where she studied the blood physiology of Humbolt penguins, Danko provided the safety net in case anything went wrong in the field: broken bones or debilitating illnesses, for example. I was sorry to learn recently of Danko's death.
Brncic was one of Dobzhansky's early students who undertook to study "co-adaptation". Dobzhansky and Wright had earlier reported on the equilibrium frequencies of chromosomal inversions that were established in laboratory populations of Drosophila pseudoobscura maintained at 25 ºC. These equilibria were established when chromosomes of the contrasting gene arrangements came from the same geographic locality. Later experiments involving chromosomes of different gene arrangements each of which came from a different geographic locality gave different results. In these inter-locality populations, one gene arrangement tended to displace the other. Assuming (for good reason) that equilibria revealed the selective supenority of inversion heterozygotes, Dobzhansky concluded that within a locality, inversions are co-adapted in the sense that their heterozygotes have superior fitness. In contrast, flies heterozygous for inversions that come from different localities do not exhibit a corresponding heterosis. In effect, Dobzhansky suggested that heterosis was the outcome of natural selection, of a co-adaptation of the gene content of different gene arrangements. As Dobzhansky's post-doctoral student during the early 1950s, Brncic undertook to demonstrate co-adaptation within the arrowhead gene arrangement; he succeeded. I have provided a detailed analysis of Brncic's results in both topics in population genetics (1968) and basic population genetics (1981).
A quarter-century ago the matter of coadaptation stirred considerable discussion. One of the supporting pieces of evidence was provided by Dobzhansky's student, Wyatt Anderson, who studied body size Drosophila pseodoobscura Ries carrying recombinant and non-recombinant chromosomes (1968, Genetical Research 12:317-330). This study followed a corresponding one carried out in Great Britain by A. M. MacFarquhar and F. M. Robertson using body size in Drosophila subobscura, as a measure of heterosis (1963, Genetical Research 4:104-131). The earlier expenment failed to reveal any heterosis or its loss of following gene recombination. The contrasting results of these two studies are mentioned in the following untitled essaynearly four decades after their original publication.
Invited Editors: R. Godoy-Herrera and G. Gajardo
Received March 10, 2000; accepted September 18, 2000