An Integrative Approach With Cytogenetic and Molecular Data of the Leaf‐Cutting Ant Acromyrmex hystrix (Latreille, 1802) Highlights a Notably Derived Karyotype in the Genus

Fungus‐growing ants are a peculiar ant group that cultivates fungi for food. Within this group, the so‐called leaf‐cutting ants ( Atta Fabricius, 1804, Acromyrmex Mayr, 1865 and Amoimyrmex Cristiano et al. 2020) hold significant ecological and economic importance. Previous studies have highlighted conserved chromosome numbers with 2 n = 22 in Atta and Amoimyrmex , and 2 n = 38 in Acromyrmex , with the single exception of the social parasite Acromyrmex ameliae De Souza et al. 2007, with 2 n = 36, as a result of Robertsonian fusion. Although Acromyrmex hystrix (Latreille, 1802) is the type species of Acromyrmex , it is one of the least‐known species of this genus. In this study, we described its karyotype and inferred the phylogenetic relationships within Acromyrmex . A distinct chromosome number was detected for the species, with 2 n = 28 chromosomes and a karyotypic formula of 10m + 16sm + 2st. Our phylogenetic reconstruction revealed Ac. hystrix constituted a separate clade within Acromyrmex . This karyotype is derived within Acromyrmex , with a chromosome number reduction from 2 n = 38 to 28. Cytogenetic and molecular data revealed the evolutionary divergence of Ac. hystrix within Acromyrmex . Although leaf‐cutting ants are among the most studied ants, many gaps remain in our understanding of these insects. The inclusion of additional species in the molecular phylogeny, coupled with chromosomal information, could provide insights into the evolution of Acromyrmex .