Abstract: PREMISE OF THE STUDY: Understanding the drivers of speciation is a central task of evolutionary biology. Chromosomal rearrangements are known to play an important role in species diversification, but the role of rearrangements of holocentric chromosomes—chromosomes without localized centromeres—is poorly understood. METHODS: We made numerous artificial crosses between Carex scoparia individuals of different diploid chromosome numbers and, for comparison, between individuals of the same chromosome number. We studied chromosome pairing and chromosomal rearrangements in the F1 individuals using light microscopy. We then estimated germination rates as a function of geographic distance, genetic distance, chromosome number differences in parents, and pairing irregularities in F1 individuals, using generalized least squares to fit alternative regression models. KEY RESULTS: The most informative predictors of germination rates in the F1 generation are chromosome number differences and minimum number of chromosome pairing irregularities in the F1 individuals. Genetic and geographic distances between parents are not significant predictors. CONCLUSIONS: Holocentric chromosomal rearrangements play an important role in postzygotic reproductive isolation in Carex through F1 hybrid inviability and sterility. Hybrid dysfunction seems to be a suitable model for chromosomal speciation when there are several chromosomal rearrangements between parents. However, we have not tested the hypothesis that genome rearrangements may also play an important role in suppressing recombination between cytogenetically divergent populations.
Marcial Escudero, Marlene Hahn, Bethany Brown, Kate Luedes & Andrew Hipp. 2016. Chromosomal rearrangements in holocentric organisms lead to reproductive isolation by hybrid dysfunction: the correlation between karyotype rearrangements and germination rates in sedges. American Journal of Botany, 103, 1529-1536.
See at AJB http://www.amjbot.org/content/103/8/1529.abstract
Participate in the symposium: Evolutionary and ecological mechanisms governing the generation and maintenance of plant assemblages in biodiversity hotspots. Conveners: Rafael Molina Venegas (University of Alcalá), Spain, and Marcial Escudero (University of Seville), Spain.Main talk: "Ecological and evolutinary assembly of plant communities, analytical and genomic tools (big biodiversity data, full genome sequencing, shotgun)", by Sébastien Lavergne, (University of Grenoble Alpes-CNRS), France.Traditionally, the evolutionary mechanisms that generate biodiversity (i.e. how new species emerge) and the ecological mechanisms that maintain biodiversity (i.e. habitat filtering, species interactions) have been studied separately. Recently it has been an extraordinary increase in studies that aim bridging gaps between these evolutionary and ecological processes. This effort has been enhanced by the rapid increase of available molecular data, published phylogenies and major advances in computational methods. Nevertheless, elucidating how evolutionary and ecological factors shape plant assemblages in biodiversity hotspots remains an important challenge. This broad-scale symposium aims to understand the historical and contemporary drivers that shaped biodiversity hotspots. This symposium includes different research topics such as functional and phylogenetic structure of plant communities, niche evolution and species diversification, macroecology, as well as the analytical (e.g. big biodiversity data) and genomic tools (e.g. full genome sequencing, shotgun) that may serve for this general purpose.