Trachymyrmex is one of the most species-rich genera within fungus-farming ants and presents intraspecific cytogenetic polymorphisms as well as possible cryptic species. This ant genus is currently paraphyletic. Therefore, to unravel systematic and taxonomic misunderstandings, it is necessary to incorporate new information. We aimed to cytogenetically and genetically examine Trachymyrmex holmgreni populations from southern and northern Brazil to identify intraspecific chromosomal variations that support incipient speciation and reveal the species' position in a molecular phylogeny. Our cytogenetic approach did not show population variation in the mapping of both 18S rDNA and the TTAGG(6) motif, presenting instead a pattern characteristic of correlated species. However, the clustered pattern of the microsatellite GA(15) showed significant differences among populations: a well-defined block in each homologue, distinctly irregular signs between homologues, and blocks in 2 pairs of homologues. Our phylogenetic reconstruction yielded unexpected results, grouping representatives of 3 former morphological groups into 1 clade, namely T. urichii, T. papulatus, and T. holmgreni. Previously, it was suggested that northern and southern populations of T. holmgreni may be undergoing incipient speciation, but we can only indicate that the southernmost population differs prominently from the others in its distribution pattern of the microsatellite GA(15). Our study also supports the uniformity of karyotypes and repetitive DNA from both telomeric sequences and ribosomal DNA in Trachymyrmex studied here. In addition, we clarify some phylogenetic uncertainties within the genus and suggest further relevant systematic changes. Finally, additional studies utilizing other probes and additional populations may allow the detection of hidden genetic variation.

1.
Abouheif E, Wray GA: Evolution of the gene network underlying wing polyphenism in ants. Science 297:249-252 (2012).
2.
Adams RMM, Jones TH, Jeter AW, De Fine Licht HH, Schultz TR, Nash DR: A comparative study of exocrine gland chemistry in Trachymyrmex and Sericomyrmex fungus-growing ants. Biochem Syst Ecol 40:91-97 (2012).
3.
Araújo MDS, Oliveira JPR, Souza DJD, Oliveira MA, Jesus FGD: Sexual castes of Trachymyrmex fuscus (Formicidae: Attini) performing worker tasks. Cienc Rural 46:199-202 (2016).
4.
Baker RJ, Bickham JW: Speciation by monobrachial centric fusions. Proc Natl Acad Sci USA 83:8245-8248 (1986).
5.
Barros LAC, Aguiar HJAC, Mariano CSF, Delabie JHC, Pompolo SG: Cytogenetic characterization of the ant Trachymyrmex fuscus Emery, 1934 (Formicidae: Myrmicinae: Attini) with the description of a chromosomal polymorphism. Ann Soc Entomol Fr 49:367-373 (2013a).
6.
Barros LAC, Mariano CSF, Pompolo SG: Cytogenetic studies of five taxa of the tribe Attini (Formicidae: Myrmicinae). Caryologia 66:59-64 (2013b).
7.
Barros LAC, Teixeira GA, Aguiar HJAC, Lopes DM, Pompolo SG: Cytogenetic studies in Trachymyrmex holmgreni Wheeler, 1925 (Formicidae: Myrmicinae) by conventional and molecular methods. Sociobiology 65:185-190 (2018).
8.
Biémont C, Vieira C: Junk DNA as evolutionary force. Nature 443:521-524 (2006).
9.
Bolton B: A New General Catalogue of the Ants of the World (Harvard University Press, Cambridge 1995).
10.
Brady SG, Schultz TR, Fisher BL, Ward PS: Evaluating alternative hypotheses for the early evolution and diversification of ants. Proc Natl Acad Sci USA 103:18172-18177 (2006).
11.
Brandão CRF, Mayhé-Nunes AJ: A phylogenetic hypothesis for the Trachymyrmex species groups, and the transition from fungus-growing to leaf-cutting in the Attini. Mem Am Entomol Inst 80:72-88 (2007).
12.
Cardoso DC, Cristiano MP: Myrmecofauna of the southern catarinense Restinga sandy coastal plain: new records of species occurrence for the State of Santa Catarina and Brazil. Sociobiology 55:229-239 (2010).
13.
Cardoso DC, Cristiano MP, Tavares MG: Methodological remarks on rearing basal Attini ants in the laboratory for biological and evolutionary studies: overview of the genus Mycetophylax. Insect Soc 58:427-430 (2011).
14.
Cardoso DC, Cristiano MP, Barros LAC, Lopes DM, Pompolo SG: First cytogenetic characterization of a species of the arboreal ant genus Azteca Forel, 1978 (Dolichoderinae, Formicidae). Comp Cytogenet 6:107-114 (2012).
15.
Cardoso DC, Pompolo SG, Cristiano MP, Tavares MG: The role of fusion in ant chromosome evolution: insights from cytogenetic analysis using a molecular phylogenetic approach in the genus Mycetophylax. PLoS One 9:e87473 (2014).
16.
Cardoso DC, Heinze J, Moura MN, Cristiano MP: Chromosomal variation among populations of a fungus-farming ant: implications for karyotype evolution and potential restriction to gene flow. BMC Evol Biol 18:146 (2018a).
17.
Cardoso DC, Santos HG, Cristiano MP: The Ant Chromosome database - ACdb: an online resource for ant (Hymenoptera: Formicidae) chromosome researchers. Myrmecol News 27:87-91 (2018b).
18.
Cazaux B, Catalan J, Veyrunes F, Douzery EJP, Britton-Davidian J: Are ribosomal DNA clusters rearrangement hotspots? A case study in the genus Mus (Rodentia, Muridae). BMC Evol Biol 11:124 (2011).
19.
Chirino MG, Dalíková M, Marec FR, Bressa MJ: Chromosomal distribution of interstitial telomeric sequences as signs of evolution through chromosome fusion in six species of the giant water bugs (Hemiptera, Belostoma). Ecol Evol 7:5227-5235 (2017).
20.
Cioffi MB, Kejnovsky E, Bertollo LAC: The chromosomal distribution of microsatellite repeats in the genome of the wolf fish Hoplias malabaricus, focusing on the sex chromosomes. Cytogenet Genome Res 132:289-296 (2011).
21.
Cristiano MP, Cardoso DC, Fernandes-Salomão TM: Cytogenetic and molecular analyses reveal a divergence between Acromyrmex striatus (Roger, 1863) and other congeneric species: taxonomic implications. PLoS One 8:e59784 (2013).
22.
Cristiano MP, Cardoso DC, Beirão MV, Reis ACCC, Pereira TP, Moura MN: Nesting and distribution of Trachymyrmex holmgreni in Brazilian restinga. Insect Soc 66:139-151 (2019).
23.
Crozier RH: Karyotypes of twenty-one ant species (Hymenoptera: Formicidae), with reviews of the known ant karyotypes. Can J Genet Cytol 12:109-128 (1970).
24.
Eckert KA, Hile SE: Every microsatellite is different: intrinsic DNA features dictate mutagenesis of common microsatellites present in the human genome. Mol Carcinog 48:379-388 (2009).
25.
Faria R, Navarro A: Chromosomal speciation revisited: rearranging theory with pieces of evidence. Trends Ecol Evol 25:660-669 (2010).
26.
Farré M, Robinson TJ, Ruiz-Herrera A: An integrative breakage model of genome architecture, reshuffling and evolution. Bioessays 37:479-488 (2015).
27.
Frydrychová R, Grossmann P, Trubac P, Vítková M, Marec F: Phylogenetic distribution of TTAGG telomeric repeats in insects. Genome 47:163-178 (2004).
28.
Gokhman VE, Kuznetsova VG: Presence of the canonical TTAGG insect telomeric repeat in the Tenthredinidae (Symphyta) suggests its ancestral nature in the order Hymenoptera. Genetica 146:341-344 (2018).
29.
Grozeva S, Kuznetsova VG, Anokhin BA: Karyotypes, male meiosis and comparative FISH mapping of 18S ribosomal DNA and telomeric (TTAGG)n repeat in eight species of true bugs (Hemiptera, Heteroptera). Comp Cytogenet 5:355-374 (2011).
30.
Guerra M: Chromosome numbers in plant cytotaxonomy: concepts and implications. Cytogenet Genome Res 120: 339-350 (2008).
31.
Hartley G, O'Neill RJ: Centromere repeats: hidden gems of the genome. Genes 10:223 (2019).
32.
Hoffmann AA, Rieseberg LH: Revisiting the impact of inversions in evolution: from population genetic markers to drivers of adaptive shifts and speciation? Annu Rev Ecol Evol Syst 39:21-42 (2008).
33.
Hughes SE, Hawley RS: Heterochromatin: a rapidly evolving species barrier. PLoS Biol 7:e1000233 (2009).
34.
Imai HT, Crozier RH, Taylor RW: Karyotype evolution in Australian ants. Chromosoma 59:341-393 (1977).
35.
Imai HT, Taylor RW, Crosland MWJ, Crozier RH: Modes of spontaneous chromosomal mutation and karyotype evolution in ants with reference to the minimum interaction hypothesis. Jpn J Genet 63:159-185 (1988).
36.
Imai HT, Satta Y, Takahata N: Integrative study on chromosome evolution of mammals, ants and wasps based on the minimum interaction theory. J Theor Biol 210:475-497 (2001).
37.
Kearse M, Moir R, Wilson A, Stones-Havas S, Cheung M, et al: Geneious Basic: an integrated and extendable desktop software platform for the organization and analysis of sequence data. Bioinformatics 28:1647-1649 (2012).
38.
Kubat Z, Hobza R, Vyskot B, Kejnovsky E: Microsatellite accumulation on the Y chromosome in Silene latifolia. Genome 51:350-356 (2008).
39.
Kumar S, Stecher G, Tamura K: MEGA7: Molecular Evolutionary Genetics Analysis version 7.0 for bigger datasets. Mol Biol Evol 33:1870-1874 (2016).
40.
Levan A, Fredga K, Sandberg AA: Nomeclature for centromeric position on chromosomes. Hereditas 52:201-220 (1964).
41.
Lorite P, Palomeque T: Karyotype evolution in ants (Hymenoptera: Formicidae), with a review of the known ant chromosome numbers. Myrmecol News 13:89-102 (2010).
42.
Lorite P, Chica E, Palomeque T: Cytogenetic studies of ant Linepithema humile Shattuck (= Iridomyrmex humilis Mayr) in European populations. Caryologia 49:199-205 (1996).
43.
Lorite P, Carrillo JA, Palomeque T: Conservation of (TTAGG)(n) telomeric sequences among ants (Hymenoptera, Formicidae). J Hered 93:282-285 (2002).
44.
Maryańska-Nadachowska A, Anokhin BA, Gnezdilov VM, Kuznetsova VG: Karyotype stability in the family Issidae (Hemiptera, Auchenorrhyncha) revealed by chromosome techniques and FISH with telomeric (TTAGG)n and 18S rDNA probes. Comp Cytogenet 10:347-369 (2016).
45.
Mayhé-Nunes AJ, Brandão CRF: Revisionary studies on the attine ant genus Trachymyrmex Forel. Part 1: definition of the genus and the Opulentus group (Hymenoptera: Formicidae). Sociobiology 40:667-698 (2002).
46.
Mayhé-Nunes AJ, Brandão CRF: Revisionary studies on the attine ant genus Trachymyrmex Forel. Part 2: the Iheringi group (Hymenoptera: Formicidae). Sociobiology 45:271-305 (2005).
47.
Mayhé-Nunes AJ, Brandão CRF: Revisionary studies on the attine ant genus Trachymyrmex Forel. Part 3: the Jamaicensis group (Hymenoptera: Formicidae). Zootaxa 1444:1-21 (2007).
48.
Mehdiabadi NJ, Schultz TR: Natural history and phylogeny of the fungus-farming ants (Hymenoptera: Formicidae: Myrmicinae: Attini). Myrmecol News 13:37-55 (2009).
49.
Menezes RST, Bardella VB, Cabral-de-Mello DC, Lucena DAA, Almeida EAB: Are the TTAGG and TTAGGG telomeric repeats phylogenetically conserved in aculeate Hymenoptera? Sci Nat 104:85 (2017).
50.
Milani D, Cabral-de-Mello DC: Microsatellite organization in the grasshopper Abracris flavolineata (Orthoptera: Acrididae) revealed by FISH mapping: remarkable spreading in the A and B chromosomes. PLoS One 9:e97956 (2014).
51.
Murakami T, Fujiwara A, Yoshida MC: Cytogenetics of ten ant species of the tribe Attini (Hymenoptera, Formicidae) in Barro Colorado Island, Panama. Chromosome Sci 2:135-139 (1998).
52.
Pereira JOP: Diversidade genética da abelha sem ferrão Melipona quinquefasciata baseada no sequenciamento das regiões ITS1 e 18S do DNA ribossômico nuclear (Doctoral thesis), Universidade Federal do Ceará (2006).
53.
Pereira TTP, Reis ACCC, Cardoso DC, Cristiano MP: Molecular phylogenetic reconstruction and localization of the (TTAGG)n telomeric repeats in the chromosomes of Acromyrmex striatus (Roger, 1863) suggests a lower ancestral karyotype for leafcutter ants (Hymenoptera). Comp Cytogenet 12:13-26 (2018).
54.
Rabeling C, Cover SP, Johnson RA, Mueller UG: A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera: Formicidae). Zootaxa 1664:1-54 (2007).
55.
Rambaut A: FigTree v1.4.3. Available at http://tree.bio.ed.ac.uk/software/figtree (2009).
56.
Rambaut A, Drummond AJ, Xie D, Baele G, Suchard MA: Posterior summarization in Bayesian phylogenetics using Tracer 1.7. Syst Biol 67:901-904 (2018).
57.
Raskina O, Belyayev A, Nevo E: Quantum speciation in Aegilops: molecular cytogenetic evidence from rDNA clusters variability in natural populations. Proc Natl Acad Sci USA 101:14818-14823 (2004).
58.
Raskina O, Barber JC, Nevo E, Belyayev A: Repetitive DNA and chromosomal rearrangements: speciation-related events in plant genomes. Cytogenet Genome Res 120:351-357 (2008).
59.
Rieseberg LH: Chromosomal rearrangements and speciation. Trends Ecol Evol 16:351-358 (2001).
60.
Ronquist F, Teslenko M, van der Mark P, Ayres DL, Darling A, et al: MrBayes 3.2: efficient Bayesian phylogenetic inference and model choice across a large model space. Syst Biol 61:539-542 (2012).
61.
Ruiz-Herrera A, Nergadze SG, Santagostino M, Giulotto E: Telomeric repeats far from the ends: mechanisms of origin and role in evolution. Cytogenet Genome Res 122:219-228 (2008).
62.
Ruiz-Ruano FJ, Cuadrado A, Montiel EE, Camacho JPM, López-León MD: Next generation sequencing and FISH reveal uneven and nonrandom microsatellite distribution in two grasshopper genomes. Chromosoma 124:221-234 (2015).
63.
Sahara K, Marec F, Traut W: TTAGG telomeric repeats in chromosomes of some insects and other arthropods. Chromosome Res 7:449-460 (1999).
64.
Sambrook J, Russell DW: Molecular Cloning: A Laboratory Manual (Cold Spring Harbor Laboratory Press, New York 2001).
65.
Sánchez-Peña SR, Chacón-Cardosa MC, Canales-del-Castillo R, Ward L, Resendez-Pérez D: A new species of Trachymyrmex (Hymenoptera, Formicidae) fungus-growing ant from the Sierra Madre Oriental of northeastern Mexico. ZooKeys 706:73-94 (2017).
66.
Schultz TR, Brady SG: Major evolutionary transitions in ant agriculture. Proc Natl Acad Sci USA 105:5435-5440 (2008).
67.
Seifert B: Cryptic species in ants (Hymenoptera: Formicidae) revisited: we need a change in the alpha-taxonomic approach. Myrmecol News 12:149-166 (2009).
68.
Shapiro JA, von Sternberg R: Why repetitive DNA is essential to genome function. Biol Rev Camb Philos Soc 80:227-250 (2005).
69.
Sosa-Calvo J, Schultz TR, Ješovnik A, Dahan RA, Rabeling C: Evolution, systematics, and natural history of a new genus of cryptobiotic fungus-growing ants. Syst Entomol 43:549-567 (2018).
70.
Speicher MR, Carter NP: The new cytogenetics: blurring the boundaries with molecular biology. Nat Rev Genet 6:782-792 (2005).
71.
Štundlová J, Šmíd J, Nguyen P, Šťáhlavský F: Cryptic diversity and dynamic chromosome evolution in Alpine scorpions (Euscorpiidae: Euscorpius). Mol Phylogenet Evol 134:152-163 (2019).
72.
Travenzoli NM, Lima BA, Cardoso DC, Dergam JA, Fernandes-Salomão TM, Lopes DM: Cytogenetic analysis and chromosomal mapping of repetitive DNA in Melipona species (Hymenoptera, Meliponini). Cytogenet Genome Res 158:213-224 (2019).
73.
Vasconcelos HL, Araujo BB, Mayhé-Nunes AJ: Patterns of diversity and abundance of fungus-growing ants (Formicidae: Attini) in areas of the Brazilian Cerrado. Rev Bras Zool 25:445-450 (2008).
74.
Vershinina AO, Anokhin BA, Lukhtanov VA: Ribosomal DNA clusters and telomeric (TTAGG)n repeats in blue butterflies (Lepidoptera, Lycaenidae) with low and high chromosome numbers. Comp Cytogenet 9:161-171 (2015).
75.
Vieira AS, Bueno OC, Camargo-Mathias MI: Morphophysiological differences between the metapleural glands of fungus-growing and non-fungus-growing ants (Hymenoptera, Formicidae). PLoS One 7:e43570 (2012).
76.
Ward PS, Downie D: The ant subfamily Pseudomyrmecinae (Hymenoptera: Formicidae): phylogeny and evolution of big-eyed arboreal ants. Syst Entomol 30:310-335 (2005).
77.
Ward PS, Sumnicht TP: Molecular and morphological evidence for three sympatric species of Leptanilla (Hymenoptera: Formicidae) on the Greek Island of Rhodes. Myrmecol News 17:5-11 (2012).
78.
White MJD: Animal Cytology and Evolution (University Press, Cambridge 1973).
79.
Wilder J, Hollocher H: Mobile elements and the genesis of microsatellites in dipterans. Mol Biol Evol 18:384-392 (2001).
80.
Zhang DX: Lepidopteran microsatellite DNA: redundant but promising. Trends Ecol Evol 19:507-509 (2004).
81.
Zolan ME: Chromosome-length polymorphism in fungi. Microbiol Mol Biol Rev 59:686-698 (1995).
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