Intraspecific variation in the karyotype length and genome size of fungus-farming ants (genus Mycetophylax), with remarks on procedures for the estimation of genome size in the Formicidae by flow cytometry

Abstract

Ants (Formicidae) present considerable diversity in chromosome numbers, which vary from n = 1 to n = 60, although this variation is not proportional to that in genome size, for which estimates range from 0.18 pg to 0.77 pg. Intraspecific variation in the chromosome number and karyotype structure has been reported among species, although the variation among populations of the same species has received much less attention, and there are few data on genome size. Here, we studied the karyotype length and genome size of different populations of the fungus-farming ants Mycetophylax conformis (Mayr, 1884) and Mycetophylax morschi (Emery, 1888). We also provide remarks on procedure for the estimation of ant genome size by Flow Cytometry (FCM) analysis. Chromosome number and morphology did not vary among the populations of M. conformis or the cytotypes of M. morschi, but karyotype length and genome size were significantly distinct among the populations of these ants. Our results on the variation in karyotype length and genome size among M. morschi and M. conformis populations reveal considerable diversity that would be largely overlooked by more traditional descriptions of karyotypes, which were also supported by the estimates of genome size obtained using flow cytometry. Changes in the amount of DNA reflect variation in the fine structure of the chromosomes, which may represent the first steps of karyotype evolution and may occur previously to any changes in the chromosome number.

Chromosome size affects sequence divergence between species through the interplay of recombination and selection

“…Chromosomes are the fundamental unit of inheritance of the nuclear DNA in all eukaryotic species and their evolution goes arm in arm with organismal evolution. Not only the sequence, but also the size, shape, structure and number of chromosomes can vary between species, populations, and even individuals within a population (Hauffe and Searle 1993;Graphodatsky et al 2011;Dion-Côté et al 2017;Moura et al 2020). Chromosome evolution is therefore crucial to our understanding of the evolution and maintenance of biodiversity.…”

Chromosome size affects sequence divergence between species through the interplay of recombination and selection

“…2017; Moura et al. 2020). Chromosome evolution is therefore crucial to our understanding of the evolution and maintenance of biodiversity.…”

Dynamic development of AT‐rich heterochromatin has followed diversification and genome expansion of psammophilous Mycetophylax (Formicidae: Attini: Attina)

“…Changes in heterochromatin probably promote karyotype repatterning in M. simplex and M. conformis since their shared common ancestor with M. morschi . The former species exhibit C‐bands + /DAPI + bands beyond the centromere and the smaller metacentric and submetacentric chromosomes, whereas M. morschi karyotypes is comprised by a majority of metacentric chromosomes relatively large in size (see Cardoso, Pompolo, et al, 2014; and Moura et al, 2020 for karyomorphometric data). There are no deeply changes in GS among psammophilous Mycetophylax except in M. simplex .…”

“…In this study, we showed that the proportion of AT% changes in evolutionarily opposite ways between the sister clades of Mycetophylax. the centromere and the smaller metacentric and submetacentric chromosomes, whereas M. morschi karyotypes is comprised by a majority of metacentric chromosomes relatively large in size (see Cardoso, Pompolo, et al, 2014;and Moura et al, 2020 for karyomorphometric data). There are no deeply changes in GS among psammophilous Mycetophylax except in M. simplex.…”