Shifts in Chromosome Evolution Rates Shape the Karyotype Patterns of Leafcutting Ants

• Published in: Ecology and evolution 2024-11, Vol.14 (11), p.e70602-n/a
• Main Authors: Cardoso, Danon Clemes, Cristiano, Maykon Passos
• Format: Article
• Language: English
• Subjects: Ants; Bats; Biological evolution; Brownian motion; chromosome evolution; Chromosome number; Chromosomes; Comparative analysis; Developmental biology; Evolution; Fossils; Fungi; Genomes; Hypotheses; karyotype; Karyotypes; leafcutting ants; phylogenetic comparative methods; phylogenetic inference; Phylogenetics; Phylogeny; Polyploidy; Taxonomy; Variation
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.70602

ABSTRACT Trait evolution has become a central focus in evolutionary biology, with phylogenetic comparative methods offering a framework to study how and why traits vary among species. Identifying variations in trait evolution rates within phylogenies is important for uncovering the mechanisms behind these differences. Karyotype variation, which is substantial across eukaryotic organisms, plays an essential role in species diversification. This study investigates karyotype variation within the leafcutting ant clade, focusing on chromosome number and morphology. We aim to determine whether karyotypic traits are phylogenetically dependent and how different evolutionary models explain karyotype diversity. Previous models have been insufficient in explaining these variations. To address these gaps, we employ modern phylogenetic methods to assess the impact of chromosomal fissions and fusions on karyotype evolution. By evaluating various evolutionary models—particularly the Brownian motion model, which suggests neutral chromosomal changes—we pursue for the further understanding the mode and tempo of karyotype evolution in ants. Our research examines how shifts in chromosomal change rates contribute to divergence among leafcutting ant species and assesses the role of chromosomal changes in the clade's evolutionary trajectory. Comparative analysis of leafcutting ant ideograms suggests that shared karyotype traits are strongly related to species relationships. This implies that karyotype diversification in leafcutting ants follows a phylogenetic trajectory at varying rates, with differences in karyotype traits reflecting the evolutionary distance between lineages. Particularly, the increase in the chromosome number of Acromyrmex is likely due to fission rearrangements rather than demi or polyploidization. We discuss and provide insights into the mechanisms driving karyotype variation and its implications for leafcutting ant diversification. Modern phylogenetic methods were used to explore how chromosome number and other karyotypic traits vary across species. The focus was on testing whether karyotypic traits follow a Brownian motion model (indicating neutral changes) or are influenced by phylogenetic constraints.This research elucidates the mechanisms underlying chromosomal evolution and its impact on leafcutting ant diversification.