Transposable Elements in a Marginal Population of Aegilops speltoides: Temporal Fluctuations Provide New Insights into Genome Evolution of Wild Diploid Wheat

The Middle East is considered the primary center of cereal species variability that resulted from Pleistocene/Holocene climatic fluctuations. It is now on record that environmentally sensitive transposable elements (TE) may be among the most important internal sources for genotypic population change. Thus, we explore the temporal dynamics of several TEs in individual genotypes from a small, marginal population of Aegilops speltoides. The population is characterized by high heteromorphy and possesses a wide spectrum of chromosomal abnormalities. The dynamics of the TE complex was traced in three morphologically different genotypes and their progeny. It was discovered that: (1) various families of TEs vary tremendously in copy number between individuals from the same population and the selfed progenies; (2) the fluctuations in copy number are TE-family specific; (3) there is a great difference in TE copy number expansion or contraction between gametophytes and sporophytes; and (4) a small percentage of TEs that increase in copy number can actually insert at novel locations. We hypothesize that TE dynamics could promote or intensify morphological and karyotypical changes, some of which may be potentially important for the process of microevolution and allow species with plastic genomes to survive as new forms or even species in times of rapid climatic change.