Aquileqia (columbines) is a plant genus of about 70 species extending across the Northern Hemisphere, including a number of garden hybrid varieties grown for showy flowers. This diversity is driven by a process called adaptive radiation, whereby new species arise quickly because they adapt to new environments. The researchers from CEITEC Masaryk University, together with a multinational consortium led by Magnus Nordborg from the Gregor Mendel Institute of Molecular Plant Biology in Vienna, published the genome sequence of eleven different Aquilegia species in the journal eLife.
The researchers found that genetic variation was widely shared between the eleven different species, even over large geographic distances. This reinforces our modern view on the origin of new biological species.
Speciation does not need to be a simple event where populations of one species become reproductively isolated, and are then split into two. Instead, it can be a long, complicated process where divergent populations cross back and become reproductively isolated again. Consequently, newly arising species share genetic variation. Findings from the study give us a better understanding of how adaptive radiation has contributed to the origin of a fascinating array of flower colours and shapes in columbines, and how plant species will adapt in the future to a changing climate.
Remarkably, the researchers also found that one of Aquilegia’s seven chromosomes was evolving differently than the rest. This chromosome had fewer genes and more non-coding sequences than the rest of the chromosomes, and was approximately twice as diverse as the other chromosomes in the genome.
The CEITEC MU research group of Martin A. Lysák was involved in cytogenomic identification and characterization of the odd chromosome, showing that the chromosome also contains large loci of genes coding ribosomal RNA molecules (rDNA). „With the exception of sex chromosomes, this is probably the first time that anyone has identified a single plant chromosome evolving differently from the remaining ones. We know that this chromosome must have originated before the adaptive radiation of columbines. However, we do not know how it originated and what evolutionary significance it has,“ said Lysák. The researchers want to continue analysing the evolution of this remarkable chromosome.
The published paper exemplifies an exciting interface between different disciplines of plant biology. Whereas population genetics studies evolution by looking at DNA changes over time, chromosomal biology focuses on the evolution of chromosomes, thus on the evolution of complete DNA molecules. The published research demonstrates that due to the advent of novel methodological approaches, ideas from both of these fields can be combined to increase our knowledge of how entire genomes evolve.