Abstract
The co-evolution of fig wasps with fig trees provide an excellent model
for studying ecological systems and adaptive evolution. Transposable
elements (TEs), as an important component of the genomes, are the
powerful driver for environmental adaptation of the organisms. Here, the
TEs in the genomes of six pollinator and five non-pollinator species
were analyzed in the characteristics of composition, historical burst
patterns, and their possible effects on the functions of conjunctive
genes. Compared with pollinators, non-pollinators’ TEs showed a
significant burst state with more types, longer lengths, and higher
contents in the genomes, which might be related to their different
evolutionary and life histories, as well as their different sensitivity
to environmental changes. However, we identified a common TE burst peak
period of 32-34 Mya in both groups, highly consistent with the glacial
epoch of Eocene-Oligocene transition in geological history. Further
functional enrichment analysis of the genes within 1 Kb near the
insertion positions of TEs in the four geological periods representing
the major continental ice sheet growth or decay was demonstrated, and
the results showed that large amount of TEs were inserted near genes
related to the environmental information processing, especially the
Circadian entrainment pathway. These TEs might act as cis-regulatory
modules to regulate the conjunctive genes in response to geo-climate
changes. These results revealed the molecular basis of the fig wasp’s
response to changes in the syconia microenvironment and paleoclimate
macroenvironment from the perspective of genomic TEs. Keywords:
transposable elements, fig wasp, adaptive evolution, geo-climate,
cis-regulatory modules