Evolución cromosomática y su relación con los patrones de diversificación en angiospermas: un acercamiento macro y microevolutivo a través de la hiperdiversa familia de las ciperáceas

Abstract

Chromosome evolution is one of the main drivers of differentiation and, eventually, speciation among eukaryotic organisms. This diversification could be triggered either by whole genome duplication (polyploidy) or partial duplications or deletions of the karyotype (aneuploidy). Moreover, mutations that cause dysploidy events (fusion or fission) or translocations in certain chromosomes could also favor diversification. The centromere plays a fundamental role in the cell division process with respect to genetic inheritance. Chromosomes with a single centromere are named monocentric, whilst the so-called holocentric chromosomes present a large number of centromeres throughout the chromosomes. If a holocentric chromosome were to break, remaining fragments would be viable in the subsequent cell division events, due to the fact that each fragment would be carrying at least one functional centromere. In the first place, we have studied the appearance of the monocentric and holocentric chromosomes in the tree of life, and the transitions between both types, being more frequent the reversion to monocentry. In the second place, we have gone in depth in the diversity of holocentric lineages, observing that there is no significant diversification difference between holocentry vs. monocentry when comparing with its sister lineages. Therefore, we continue to study whether different modes of chromosome number evolution exist in the most species-rich holocentric plant lineage (family Cyperaceae, order Poales). We found significant support for a complex model displaying different scenarios, based on its relationship with previously reported diversification shifts in the family. Finally, we focused on the relationship between chromosome number and several climatic and morphological factors in the genus Carex. This is the most diverse among the sedges genera, with ca. 2000 species, and which karyotype mainly evolves by means of dysploidy. We found significantly higher diversification rates near intermedial chromosome numbers of the genus. We infer that, despite showing a multitude of distinct evolutionary histories, chromosome number seems to have had an impact on the genus evolution, in part related to morphological and niche climatic characteristics.