Cytogenetic and molecular analyses reveal a divergence between Acromyrmex striatus (Roger, 1863) and other congeneric species: taxonomic implications

PLoS One. 2013;8(3):e59784. doi: 10.1371/journal.pone.0059784. Epub 2013 Mar 20.

Abstract

The leafcutter ants, which consist of Acromyrmex and Atta genera, are restricted to the New World and they are considered the main herbivores in the neotropics. Cytogenetic studies of leafcutter ants are available for five species of Atta and 14 species of Acromyrmex, both including subspecies. These two ant genera have a constant karyotype with a diploid number of 22 and 38 chromosomes, respectively. The most distinct Acromyrmex species from Brazil is A. striatus, which is restricted to the southern states of Santa Catarina and Rio Grande do Sul. Several cytogenetic and phylogenetic studies have been conducted with ants, but the karyotypic characterization and phylogenetic position of this species relative to leafcutter ants remains unknown. In this study, we report a diploid number of 22 chromosomes for A. striatus. The phylogenetic relationship between A. striatus and other leafcutter ants was estimated based on the four nuclear genes. A. striatus shared the same chromosome number as Atta species and the majority of metacentric chromosomes. Nuclear data generated a phylogenetic tree with a well-supported cluster, where A. striatus formed a different clade from other Acromyrmex spp. This combination of cytogenetic and molecular approaches provided interesting insights into the phylogenetic position of A. striatus among the leafcutter ants and the tribe Attini.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Ants / classification*
  • Ants / genetics*
  • Base Sequence
  • Bayes Theorem
  • Brazil
  • Chromosomes / genetics*
  • Evolution, Molecular*
  • Genes / genetics
  • Karyotyping
  • Likelihood Functions
  • Models, Genetic
  • Molecular Sequence Data
  • Phylogeny*
  • Sequence Alignment
  • Sequence Analysis, DNA
  • Species Specificity

Grants and funding

This research forms part of the DSc thesis of the first author, who was supported by a Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) studentship. Additional financial support was provided by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and FAPEMIG (Process numbers: CRA-APQ-00935-11). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.