Abstract
This theory seeks to define species and to explore evolutionary forces
and genetic elements in speciation and species maintenance. The theory
explains how speciation and species maintenance are caused by natural
selection acting on non-Mendelian and Mendelian variation, respectively.
The emergence and maintenance of species as groups of populations are
balanced by evolutionary forces including complementary mechanisms of
gene flow within and between populations at population-specific rates:
sexual and asexual reproduction, recombining and nonrecombining genome
regions, vertical and horizontal DNA transfer, and transposon
proliferation and control. While recombining genome regions carry
conserved genes and are subjected to meiotic recombination,
nonrecombining genome regions carry accessory genes and are not
subjected to such structural restrain. Sexual reproduction, vertical DNA
transfer, recombining genome regions and transposon control keep species
in existence by maintaining recombining chromosome number and structure,
while asexual reproduction, horizontal DNA transfer, nonrecombining
genome regions and transposon proliferation help species emerge by
promoting reproductive isolation and changes in chromosome number and
structure. The theory is based on the analysis of the genome sequences
of isolates in the Fusarium oxysporum complex. The rate of horizontal
supernumerary chromosome transfer in this complex was estimated to be
0.1 per genome per year.