FARRAR, DONALD R.* AND JAMES E. WATKINS. Department of Botany, Iowa State University, Ames, IA 50011. - Morphological differentiation through differential gene silencing in the allotetraploid derivatives of Botrychium lunaria X B. lanceolatum-a partial confirmation of the hypothesis of Werth and Windham.
An allotetraploid species, with two sets of homoeologous gene loci,
can lose the function of genes from one of its diploid parents at any
given locus without deleterious loss of gene product. This silencing
of gene loci can be visualized through enzyme electrophoresis when the
gene products of the parental diploid species migrate differentially
and one of these contributions is clearly missing in the
allotetraploid. Werth and Windham postulated that extensive gene
silencing over time could produce evolutionary change in
allotetraploids including divergent evolution between genetically
isolated lines. Botrychium species present a model for testing
the possibility of morphological divergence of allotetraploid lines
through differential gene silencing. Botrychium lunaria and
B. lanceolatum each display a number of unique allozymes
revealing them as the unquestionable parents of the widespread
tetraploid B. pinnatum. Recently discovered B.
"alaskense" is equally unquestionably a tetraploid product
of the same parental diploids, yet it is quite distinct
morphologically from B. pinnatum. Allozyme patterns show these
taxa to be differentially silenced at 50% of the loci examined in
which silencing is detectable.
Key words: Allotetraploid, Botrychium, gene silencing, speciation